Science.gov

Sample records for actinic keratosis treatment

  1. Actinic keratosis

    MedlinePlus

    Solar keratosis; Sun-induced skin changes - keratosis; Keratosis - actinic (solar); Skin lesion - actinic keratosis ... likely to develop it if you: Have fair skin, blue or green eyes, or blond or red ...

  2. Actinic keratosis. Current treatment options.

    PubMed

    Jeffes, E W; Tang, E H

    2000-01-01

    Actinic keratoses are hyperkeratotic skin lesions that represent focal abnormal proliferation of epidermal keratinocytes. Some actinic keratoses evolve into squamous cell carcinoma of the skin, while others resolve spontaneously. The conversion rate of actinic keratosis to squamous cell carcinoma is not accurately known, but appears to be in the range of 0.25 to 1% per year. Although there is a low rate of conversion of actinic keratoses to squamous cell carcinoma, 60% of squamous cell carcinomas of the skin probably arise from actinic keratoses. The main cause of actinic keratoses in otherwise healthy Caucasians appears to be the sun. Therapy for actinic keratoses begins with prevention which starts with sun avoidance and physical protection. Sunprotection with sunscreens actually slows the return of actinic keratoses in patients already getting actinic keratoses. Interestingly, a few studies are available that demonstrate that a high fat diet is associated with the production of more actinic keratoses than is a low fat diet. One of the mainstays of therapy has been local destruction of the actinic keratoses with cryotherapy, and curettage and electrodesiccation. A new addition to this group of therapies to treat individual actinic keratoses is photodynamic therapy with topical aminolevulinic acid and light. In patients who have numerous actinic keratoses in an area of severely sun damaged skin, therapies which are applied to the whole actinic keratosis area are used. The goal of treating such an area of skin is to treat all of the early as well as the numerous clinically evident actinic keratoses at the same time. The classical approaches for treating areas of photodamaged skin without treating actinic keratoses individually include: the use of topically applied fluorouracil cream, dermabrasion, and cutaneous peels with various agents like trichloroacetic acid. Both topically as well as orally administered retinoids have been used to treat actinic keratoses but

  3. Non-adherence to topical treatments for actinic keratosis

    PubMed Central

    Shergill, Bav; Zokaie, Simon; Carr, Alison J

    2014-01-01

    Background There is limited information on the patterns of use, adherence rates, and factors that impact adherence with topical treatments for actinic keratosis (AK). Objectives To establish patterns of use and adherence with topical treatments for AK and to identify treatment-related factors that impact on adherence. Methods A community-based, cross-sectional study was performed using a standardized questionnaire completed online or via telephone interview. Patients were stratified according to the presence of AK lesions on the scalp and/or other extremities; and presence of scarring resulting from treatment. Results This study included 305 patients with AK who were currently using a patient-applied topical therapy for AK or had used one within the previous 12 months. In total, 88% (n = 268/305) of patients were either non-adherent, non-persistent or both non-adherent and non-persistent to topical therapy. Duration of treatment was associated with increasing rates of non-adherence (adjusted odds ratio [OR]; for treatment durations greater than 4 weeks, 2.2, P < 0.01): 52% of patients were non-adherent with 3–4 week treatment duration; 69% of patients with 4–8 week treatment duration; and 71% of patients with 6–12 week treatment duration. There were similar increases in non-persistence with increasing treatment duration (adjusted OR; for treatment durations greater than 4 weeks, 2.1, P < 0.05). Conclusion This study found high rates of non-adherence and non-persistence in patients with AK. Duration of treatment was a significant factor contributing to non-adherence and non-persistence to topical treatments. Patient-applied topical therapies that require less frequent application and have shorter treatment duration may be associated with improved adherence rates. PMID:24379656

  4. A consensus approach to improving patient adherence and persistence with topical treatment for actinic keratosis

    PubMed Central

    Stockfleth, Eggert; Peris, Ketty; Guillen, Carlos; Cerio, Rino; Basset-Seguin, Nicole; Foley, Peter; Sanches, José; Culshaw, Alex; Erntoft, Sandra; Lebwohl, Mark

    2015-01-01

    Background Topical therapy is important in the treatment of actinic keratosis, but guidance for improving adherence/persistence during topical therapy is still lacking. Objectives To utilize expert consensus to generate a list of recommendations to improve real-world efficacy when prescribing topical therapy for actinic keratosis. Methods An expert panel of eight dermatologists was convened to generate recommendations based on facilitated discussion and consensus generation using a modified Delphi session. The recommendations were ratified with the expert panel. Results Facilitated discussion generated 31 issues within five themes, which were prioritized using expert voting. Consensus was achieved on the importance of short and simple treatment regimens for maximizing patient compliance, physician awareness of the progression of actinic keratosis to squamous cell carcinoma, provision of appropriate patient information, and the use of effective communication strategies to educate physicians about actinic keratosis. Based on these key findings, eight recommendations were generated. Conclusions The recommendations will assist physicians when prescribing topical actinic keratosis therapy. Further research should focus on the types of patient outcomes that are influenced by the characteristics of topical field therapy. PMID:25865875

  5. New developments in the treatment of actinic keratosis: focus on ingenol mebutate gel

    PubMed Central

    Berman, Brian

    2012-01-01

    Actinic keratosis is a common disease in older, fair-skinned people, and is a consequence of cumulative ultraviolet exposure. It is part of a disease continuum in photodamaged skin that may lead to invasive squamous cell carcinoma. Treatment options frequently used include cryosurgery and topical pharmacologic agents, which are examples of lesion-directed and field-directed strategies. Ingenol mebutate gel was recently approved by the US Food and Drug Administration for topical treatment of actinic keratosis. While the mechanism of action of ingenol mebutate is not fully understood, in vitro and in vivo studies using tumor models indicate it has multiple mechanisms. Ingenol mebutate directly induces cell death by mitochondrial swelling and loss of cell membrane integrity preferentially in transformed keratinocytes. It promotes an inflammatory response characterized by infiltration of neutrophils and other immunocompetent cells that kills remaining tumor cells. The ability of ingenol mebutate to eliminate mutant p53 patches in ultraviolet-irradiated mouse skin suggests that it may have the potential to treat chronically ultraviolet-damaged skin. In human studies, ingenol mebutate achieved high clearance of actinic keratosis on the head and body after 2–3 consecutive daily treatments when measured by complete or partial clearance of lesions. Localized inflammatory skin responses were generally mild to moderate and resolved in less than a month. PMID:22956883

  6. Comparative study of actinic keratosis treatment with 3% diclofenac sodium and 5% 5-fluorouracil*

    PubMed Central

    Segatto, Majoriê Mergen; Dornelles, Sérgio Ivan Torres; Silveira, Vera Bauer; Frantz, Gabriela de Oliveira

    2013-01-01

    BACKGROUND Actinic keratosis is a frequent lesion which occurs in sunlight exposed areas. Diclofenac sodium and 5-Fluorouracil are effective, non-invasive and easy-to-apply topical treatment options. OBJECTIVES To assess and compare the effectiveness of 3% diclofenac sodium associated with 2.5% hyaluronic acid and of 5% 5-Fluorouracil for the treatment of actinic keratosis, as well as the patient's degree of satisfaction and tolerability. METHODS 28 patients with a clinical diagnosis of actinic keratosis were randomized to receive diclofenac sodium or 5-Fluorouracil and were clinically assessed before and after treatment as well as 8 weeks after the end of treatment. Modified versions of the Investigator and Patient Global Improvement Scores were used. RESULTS The average number of lesions in the diclofenac sodium group before and after treatment was 13.6 and 6.6 (p<0,001), respectively, while it was 17.4 and 3.15 (p<0.001) in the 5-Fluorouracil group. There was a significant reduction in the number of lesions in the 5-Fluorouracil group in relation to the diclofenac sodium group (p<0.001). To the non-blinded physician, there was a higher satisfactory therapeutic response in the 5-Fluorouracil group (p<0.001); to the blinded physician, there was a higher satisfactory response in this same group, although not statistically significant (p=0.09). There was a high degree of satisfaction in both groups (73% in the diclofenac sodium group and 77% in the 5-Fluorouracil group; p=0.827). Regarding adverse effects, the diclofenac sodium group presented a higher degree of satisfaction (93.3% vs 38.4%; p=0.008). Erythema, edema, crusts and itching were significantly higher in the 5-Fluorouracil group. CONCLUSION We concluded that 5-Fluorouracil was more effective; however, it showed lower tolerability than diclofenac sodium. PMID:24173178

  7. Comparison of three light doses in the photodynamic treatment of actinic keratosis using mathematical modeling.

    PubMed

    Vignion-Dewalle, Anne-Sophie; Betrouni, Nacim; Tylcz, Jean-Baptiste; Vermandel, Maximilien; Mortier, Laurent; Mordon, Serge

    2015-05-01

    Photodynamic therapy (PDT) is an emerging treatment modality for various diseases, especially for cancer therapy. Although high efficacy is demonstrated for PDT using standardized protocols in nonhyperkeratotic actinic keratoses, alternative light doses expected to increase efficiency, to reduce adverse effects or to expand the use of PDT, are still being evaluated and refined. We propose a comparison of the three most common light doses in the treatment of actinic keratosis with 5-aminolevulinic acid PDT through mathematical modeling. The proposed model is based on an iterative procedure that involves determination of the local fluence rate, updating of the local optical properties, and estimation of the local damage induced by the therapy. This model was applied on a simplified skin sample model including an actinic keratosis lesion, with three different light doses (red light dose, 37 J∕cm2, 75 mW∕cm2, 500 s; blue light dose, 10 J∕cm2, 10 mW∕cm2, 1000 s; and daylight dose, 9000 s). Results analysis shows that the three studied light doses, although all efficient, lead to variable local damage. Defining reference damage enables the nonoptimal parameters for the current light doses to be refined and the treatment to be more suitable.

  8. Comparison of three light doses in the photodynamic treatment of actinic keratosis using mathematical modeling

    NASA Astrophysics Data System (ADS)

    Vignion-Dewalle, Anne-Sophie; Betrouni, Nacim; Tylcz, Jean-Baptiste; Vermandel, Maximilien; Mortier, Laurent; Mordon, Serge

    2015-05-01

    Photodynamic therapy (PDT) is an emerging treatment modality for various diseases, especially for cancer therapy. Although high efficacy is demonstrated for PDT using standardized protocols in nonhyperkeratotic actinic keratoses, alternative light doses expected to increase efficiency, to reduce adverse effects or to expand the use of PDT, are still being evaluated and refined. We propose a comparison of the three most common light doses in the treatment of actinic keratosis with 5-aminolevulinic acid PDT through mathematical modeling. The proposed model is based on an iterative procedure that involves determination of the local fluence rate, updating of the local optical properties, and estimation of the local damage induced by the therapy. This model was applied on a simplified skin sample model including an actinic keratosis lesion, with three different light doses (red light dose, 37 J/cm2, 75 mW/cm2, 500 s blue light dose, 10 J/cm2, 10 mW/cm2, 1000 s and daylight dose, 9000 s). Results analysis shows that the three studied light doses, although all efficient, lead to variable local damage. Defining reference damage enables the nonoptimal parameters for the current light doses to be refined and the treatment to be more suitable.

  9. Real-world approach to actinic keratosis management: practical treatment algorithm for office-based dermatology.

    PubMed

    Dirschka, Thomas; Gupta, Girish; Micali, Giuseppe; Stockfleth, Eggert; Basset-Séguin, Nicole; Del Marmol, Véronique; Dummer, Reinhard; Jemec, Gregor B E; Malvehy, Josep; Peris, Ketty; Puig, Susana; Stratigos, Alexander J; Zalaudek, Iris; Pellacani, Giovanni

    2016-11-13

    Actinic keratosis (AK) is a chronic skin disease in which multiple clinical and subclinical lesions co-exist across large areas of sun-exposed skin, resulting in field cancerisation. Lesions require treatment because of their potential to transform into invasive squamous cell carcinoma. This article aims to provide office-based dermatologists and general practitioners with simple guidance on AK treatment in daily clinical practice to supplement existing evidence-based guidelines. Novel aspects of the proposed treatment algorithm include differentiating patients according to whether they have isolated scattered lesions, lesions clustered in small areas or large affected fields without reference to specific absolute numbers of lesions. Recognising that complete lesion clearance is rarely achieved in real-life practice and that AK is a chronic disease, the suggested treatment goals are to reduce the number of lesions, to achieve long-term disease control and to prevent disease progression to invasive squamous cell carcinoma. In the clinical setting, physicians should select AK treatments based on local availability, and the presentation and needs of their patients. The proposed AK treatment algorithm is easy-to-use and has high practical relevance for real-life, office-based dermatology.

  10. Ingenol mebutate in low amounts for the treatment of actinic keratosis in Korean patients

    PubMed Central

    Joe, Hyun Jae; Oh, Byung Ho

    2017-01-01

    Background Ingenol mebutate (IM), a novel agent for field therapy of actinic keratosis (AK), has a drawback of inducing local skin reactions (LSRs), which may cause discomfort in patients. To reduce the LSRs, we tried the application of IM in low amounts. Objective The purpose of this study was to review Korean patients with AK being treated with IM and evaluate the LSRs and therapeutic outcomes of low amounts of IM. Methods We retrospectively reviewed 47 patients with AK on the face. A total of 20 and 27 patients were treated by applying recommended amount of 18.8 mg/cm2 and the lower amount of 10 mg/cm2, respectively. Results The mean composite LSR score for the low amount group (LAG; 12.18±3.29) was significantly lower than that for the recommended amount group (RAG; 15.45±2.70) (P<0.01, independent sample t-test). The 2-month clearance rate calculated by the number of AKs before and after treatment in each patient was significantly higher for RAG (88.16%), compared with 75.56% for LAG (P<0.001). Conclusion Low amount of IM for the treatment of facial AK significantly reduced LSRs in Korean patients. Minimizing LSRs may allow for a secondary targeting treatment of IM for the residual lesions, depending on initial treatment outcomes.

  11. Laser-mediated Photodynamic Therapy: An Alternative Treatment for Actinic Keratosis?

    PubMed

    Kessels, Janneke P H M; Nelemans, Patty J; Mosterd, Klara; Kelleners-Smeets, Nicole W J; Krekels, Gertruud A M; Ostertag, Judith U

    2016-03-01

    Photodynamic therapy (PDT) with light emitting diode (LED) illumination is a frequently used treatment modality for actinic keratosis (AK) with excellent cosmetic outcome. A major disadvantage, however, is the high pain score. Pulsed dye laser (PDL) illumination has been suggested, but the long-term efficacy of this treatment is unknown. In this split-face study we prospectively treated 61 patients with AK, with both LED-PDT and PDL-PDT. The mean change in the number of lesions between the end of follow-up and start of therapy was -4.25 (95% confidence interval (95% CI) -5.07; -3.43) for LED-PDT and -3.88 (95% CI -4,76; -2.99) for PDL-PDT, with a non-significant difference (p = 0.258) of -0.46 (95% CI -1.28; 0.35). The percentage decrease from baseline in the total number of AK was 55.8% and 47.8%, respectively, at 12-month follow-up. Visual analogue scale pain score was lower after PDL (mean 2.64) compared with LED illumination (mean 6.47). These findings indicate that PDL-PDT is an effective alternative illumination source fo.

  12. Cost-effectiveness analysis of topical treatments for actinic keratosis in the perspective of the Italian health care system.

    PubMed

    Colombo, G L; Chimenti, S; Di Matteo, S; Fargnoli, M C; Frascione, P; Silipo, V; Peris, K

    2010-10-01

    Actinic keratosis (AK) is the most common cutaneous malignant neoplasm and its prevalence continues to increase. According to the most recent findings, AK is currently considered the initial stage, in situ, of squamous cell carcinoma. Field-directed therapies for AKs are the preferred treatment since they have the advantage to clear the clinically visible lesions and also subclinical lesions within the cancerous field. We assessed the cost-effectiveness of topical treatments for AKs including 3% diclofenac in 2.5% hyaluronic acid (HA) gel, imiquimod 5% cream and photodynamic therapy with methyl aminolevulinate (MAL-PDT) in the perspective of the Italian Health Care System (SSN). We used a decision tree analytical approach and efficacy data were drawn from published clinical trials. Cost was evaluated from the SSN perspective during a time horizon of 3 months. A responder was defined as a patient with all lesions clinically cleared and showing an excellent cosmetic result. Based on the applied model, the cost per complete responder was calculated. Diclofenac 3% in HA was less expensive (Euro 256) than MAL-PDT (Euro 320) and imiquimod (Euro 342). Effectiveness was similar and better for diclofenac 3% in HA and MAL-PDT (0.813%) in comparison to 0.734% of imiquimod, respectively. The one-way and probabilistic sensitivity analyses confirmed the results of base case scenario. Based on this cost-effectiveness model, diclofenac 3% in HA can be considered the treatment of choice for AK lesions and surrounding field under a pharmacoeconomic point of view.

  13. Ingenol Mebutate Topical Gel A Status Report On Clinical Use Beyond Actinic Keratosis

    PubMed Central

    Del Rosso, James Q.

    2016-01-01

    Ingenol mebutate is available as a topical gel formulation approved for the treatment of actinic keratosis. Two different concentrations are available for treatment of actinic keratoses at specific anatomic sites with the advantages of short durations of therapy and limited “down time” related to visible inflammation as compared to other topical agents. Due to the various modes of action of ingenol mebutate, it has also been used for treatment of disease states other than actinic keratosis. This manuscript discusses the suggested modes of action of ingenol mebutate and reviews publications on the use of ingenol mebutate gel for cutaneous disorders other than actinic keratosis, including squamous cell carcinoma in-situ, basal cell carcinoma, actinic cheilitis, anogenital warts, and others. Author commentaries are also included with the goal of providing relevant clinical insights. PMID:28224020

  14. Prospective, case-based assessment of sequential therapy with topical Fluorouracil cream 0.5% and ALA-PDT for the treatment of actinic keratosis.

    PubMed

    Martin, George

    2011-04-01

    The sequential use of topical therapies and short-incubation photodynamic therapy for actinic keratosis (AK) has not been extensively studied. The author reports on treatment with sequential 5-fluorouracil (5-FU) cream 0.5% and 5-aminolevulinic acid?photodynamic therapy (ALA-PDT) in three older men with photodamaged skin and a history of AK. These findings suggest that this combination therapy, when compared with short-contact (1 hour) ALA-PDT alone, is more effective, minimizes the recurrence of areas of field cancerization and improves the appearance of the skin. The use of 5-FU cream 0.5% before and after photodynamic therapy is effective in revealing the presence of both clinical and subclinical AK lesions.

  15. Actinic keratosis: preventable and treatable like other precancerous and cancerous skin lesions.

    PubMed

    Nicol, N H

    1989-01-01

    Actinic keratosis, like many other precancerous and cancerous skin lesions are preventable and treatable. Nurses, physicians, other health care providers, school teachers, daycare workers, grandparents, parents, and children must assume the role of educating others regarding attitudes and knowledge about sun damage to the skin. Protecting one's skin should be a lifelong process from the newborn period onward. However, if sun damage does occur, the next important step is early detection of skin cancer. Individuals with associated risk factors should be screened routinely by health care personnel with expertise in the area of skin cancer. The best treatment of actinic keratosis, as with most diseases, is prevention.

  16. The Impact of the Current United States Guidelines on the Management of Actinic Keratosis

    PubMed Central

    2010-01-01

    Actinic keratosis is one of the most common diagnoses made by dermatologists. Many experts recommend treating all actinic keratoses because of their potential to progress to invasive squamous cell carcinoma. Physicians have a large armamentarium of actinic keratosis treatment modalities available to them, including destructive therapies, such as cryotherapy, curettage and electrodessication, chemical peels, photodynamic therapy, and topical therapies, including 5-fluorouracil, imiquimod, and diclofenac. In addition to standardized monotherapy regimens, combinations of two concomitant or sequential therapies and alternative topical dosing regimens have been studied in a number of clinical trials. Such therapeutic courses are used to maintain or enhance efficacy while improving tolerability, convenience, and/or patient adherence. This abundance of treatment options prompted development of several actinic keratosis management guidelines. Whereas two sets of treatment guidelines were published by European organizations within the past three years, the most recent United States-based guidelines for dermatologists were published by the American Academy of Dermatology in 1995. Because they are not up to date, the 1995 United States guidelines lack recent clinical developments and an evidence rating system and can no longer effectively guide practitioners. While there are benefits and potential limitations to developing an updated set of United States-based guidelines, there is a clearly defined need for a unified, comprehensive, evidence-based guideline approach to actinic keratosis treatment that balances the need to tailor long-term management of the disease to the needs of the individual patient. PMID:21103312

  17. Evaluation of the therapeutic results of actinic keratosis treated with topical 5% fluorouracil by reflectance confocal laser microscopy: preliminary study*

    PubMed Central

    Ishioka, Priscila; Maia, Marcus; Rodrigues, Sarita Bartholomei; Marta, Alessandra Cristina; Hirata, Sérgio Henrique

    2015-01-01

    Topical treatment for actinic keratosis with 5% fluorouracil has a recurrence rate of 54% in 12 months of follow-up. This study analyzed thirteen actinic keratoses on the upper limbs through confocal microscopy, at the time of clinical diagnosis and after 4 weeks of treatment with fluorouracil. After the treatment was established and evidence of clinical cure was achieved, in two of the nine actinic keratoses, confocal microscopy enabled visualization of focal areas of atypical honeycomb pattern in the epidermis indicating therapeutic failure. Preliminary data suggest the use of confocal microscopy as a tool for diagnosis and therapeutic control of actinic keratosis. PMID:26131881

  18. Reduced degree of irritation during a second cycle of ingenol mebutate gel 0.015% for the treatment of actinic keratosis.

    PubMed

    Jim On, Shelbi C; Haddican, Madelaine; Yaroshinsky, Alex; Singer, Giselle; Lebwohl, Mark

    2015-01-01

    Ingenol mebutate gel is a topical field treatment of actinic keratosis (AK). One of several proposed mechanisms of action for ingenol mebutate is induction of cell death in proliferating keratinocytes, suggesting a preferential action on AKs rather than healthy skin. Local skin reactions (LSRs) during 2 sequential 4-week cycles of AK treatment with ingenol mebutate gel 0.015% on the face or scalp were evaluated to test the hypothesis that reapplication of the study product would produce lower LSR scores than during the first treatment cycle. In this unblinded study, 20 participants with AKs on the face or scalp were treated with ingenol mebutate gel 0.015% once daily for 3 days in 2 sequential 4-week cycles. Composite LSR scores were evaluated during both cycles. The composite LSR score during the second cycle was found to be significantly lower than the first cycle (P=.0002). The proportion of participants who experienced LSRs in the second treatment cycle was less than the first cycle. Ingenol mebutate gel 0.015% may cumulatively reduce the burden of sun-damaged skin over 2 treatment cycles by targeting and removing transformed keratinocytes.

  19. Efficacy of a photolyase-based device in the treatment of cancerization field in patients with actinic keratosis and non-melanoma skin cancer.

    PubMed

    Puviani, M; Barcella, A; Milani, M

    2013-12-01

    Eryfotona AK-NMSC (ISDIN Spain) is a film-forming medical device in cream or fluid formulation containing the DNA-repair enzyme photolyase and high-protection UV filters in liposomes (repairsomes) indicated in the treatment of cancerization field in patients with actinic keratosis (AK) or non-melanoma skin cancer (NMSC). Photolyase is an enzyme that recognizes and directly repairs UV-induced DNA damage. The most common UV-induced DNA damage is the formation of cyclobutane pyrimidine dimers (CPD). Clinical studies evaluating the histological and cellular effects of Eryfotona AK-NMSC have shown a potential benefit in the treatment of the cancerization field in AK patients. In particular the use of Eryfotona AK-NMSC improves the confocal microscopic appearance of skin at the cancerization field level. In addition, Eryfotona AK-NMSC improves the p53 gene expression at keratinocyte level. In this study we reported a series of 6 cases of patients with AK or NMSC lesions treated with Eryfotona AK-NMSC fluid, both as coadjuvant and as single treatment, applied twice daily in the affected area with photograph documentation. Clinical photographs of the skin lesions at baseline and after Eryfotona AK-NMSC treatment were taken in all cases using a high-definition digital camera. Six patients with multiple AK lesions of the scalp or face with or without NMSC were treated for a mean of 1-3 months with Eryfotona AK-NMSC fluid formulation. Image documentations before and after treatment of this clinical series show a great improvement in AK lesions count and of cancerization field. This clinical series supports the clinical efficacy of the use of photolyase and high-protection UV filters in the treatment of cancerization field and AK lesions in patients with actinic damage.

  20. Oral nicotinamide and actinic keratosis: a supplement success story.

    PubMed

    Kim, Burcu; Halliday, Gary M; Damian, Diona L

    2015-01-01

    Nicotinamide has shown potential as a safe and effective intervention for the prevention of malignant and premalignant skin lesions. Recent studies have shown that nicotinamide, in both oral and topical forms, is able to prevent ultraviolet-induced immunosuppression in humans [1,2,3] and mice [4,5]. Immunosuppression is a known factor for the progression of premalignant lesions, such as actinic keratosis [6]. Murine studies have shown that nicotinamide is also able to protect against photocarcinogenesis [4,5]. Preliminary human studies suggest that nicotinamide may help prevent skin cancers and enhance the regression of actinic keratoses.

  1. Pre-treatment protoporphyrin IX concentration in actinic keratosis lesions may be a predictive biomarker of response to aminolevulinic-acid based photodynamic therapy

    PubMed Central

    Kanick, SC; Davis, SC; Zhao, Y; Sheehan, KL; Hasan, T; Maytin, EV; Pogue, BW; Chapman, MS

    2015-01-01

    Background Although Aminolevulinic Acid (ALA)-induced protoporphyrin IX (PpIX) photodynamic therapy (PDT) is an effective FDA-approved therapy for actinic keratosis (AK), a substantial fraction of patients (up to 25%) do not respond to treatment. This study examined the feasibility of using pre-treatment measurements of PpIX concentration in AK lesions to predict response of ALA-PpIX PDT. Methods A non-invasive fiber-optic fluorescence spectroscopy system was used to measure PpIX concentration in patients undergoing standard-of-care ALA-PDT for AK. All patients provided assessments of pain at the time of treatment (n=70), and a subset reported pain and erythema 48–76 hours after treatment (n=13). Results PpIX concentration was significantly higher in lesions of patients reporting high levels of pain (VAS score ≥ 5) immediately after treatment vs. patients reporting pain scores below VAS=5 (p<0.022) (n=70). However, pain was not an exclusive indicator of PpIX concentration as many patients with low PpIX concentration reported high pain. In a subpopulation of patients surveyed in the days after treatment (n=13), PpIX concentration measured on the day of treatment was uncorrelated with pain-reported immediately after treatment (r=0.17, p<0.57), but positive correlations were found between PpIX concentration and patient-reported pain (r=0.55, p < 0.051) and erythema (r=0.58, p < 0.039) in the 48–72 hr following treatment. Conclusions These data suggest that in vivo optical measurements of PpIX concentration acquired before light delivery may be an objective predictor of response to ALA-PpIX PDT. Identification of non-responding patients on the day of treatment could facilitate the use of interventions that may improve outcomes. PMID:26480810

  2. The impact of the current United States guidelines on the management of actinic keratosis: is it time for an update?

    PubMed

    Martin, George

    2010-11-01

    Actinic keratosis is one of the most common diagnoses made by dermatologists. Many experts recommend treating all actinic keratoses because of their potential to progress to invasive squamous cell carcinoma. Physicians have a large armamentarium of actinic keratosis treatment modalities available to them, including destructive therapies, such as cryotherapy, curettage and electrodessication, chemical peels, photodynamic therapy, and topical therapies, including 5-fluorouracil, imiquimod, and diclofenac. In addition to standardized monotherapy regimens, combinations of two concomitant or sequential therapies and alternative topical dosing regimens have been studied in a number of clinical trials. Such therapeutic courses are used to maintain or enhance efficacy while improving tolerability, convenience, and/or patient adherence. This abundance of treatment options prompted development of several actinic keratosis management guidelines. Whereas two sets of treatment guidelines were published by European organizations within the past three years, the most recent United States-based guidelines for dermatologists were published by the American Academy of Dermatology in 1995. Because they are not up to date, the 1995 United States guidelines lack recent clinical developments and an evidence rating system and can no longer effectively guide practitioners. While there are benefits and potential limitations to developing an updated set of United States-based guidelines, there is a clearly defined need for a unified, comprehensive, evidence-based guideline approach to actinic keratosis treatment that balances the need to tailor long-term management of the disease to the needs of the individual patient.

  3. Treatment Options for Actinic Keratosis

    MedlinePlus

    ... Skin Cancer Skin color and being exposed to sunlight can increase the risk of nonmelanoma skin cancer ... carcinoma include the following: Being exposed to natural sunlight or artificial sunlight (such as from tanning beds) ...

  4. MAL Daylight Photodynamic Therapy for Actinic Keratosis: Clinical and Imaging Evaluation by 3D Camera

    PubMed Central

    Cantisani, Carmen; Paolino, Giovanni; Pellacani, Giovanni; Didona, Dario; Scarno, Marco; Faina, Valentina; Gobello, Tommaso; Calvieri, Stefano

    2016-01-01

    Non-melanoma skin cancer is the most common skin cancer with an incidence that varies widely worldwide. Among them, actinic keratosis (AK), considered by some authors as in situ squamous cell carcinoma (SCC), are the most common and reflect an abnormal multistep skin cell development due to the chronic ultraviolet (UV) light exposure. No ideal treatment exists, but the potential risk of their development in a more invasive form requires prompt treatment. As patients usually present with multiple AK on fields of actinic damage, there is a need for effective, safe, simple and short treatments which allow the treatment of large areas. To achieve this, daylight photodynamic therapy (DL-PDT) is an innovative treatment for multiple mild actinic keratosis, well tolerated by patients. Patients allocated to the PDT unit, affected by multiple mild−moderate and severe actinic keratosis on sun-exposed areas treated with DL-PDT, were clinically evaluated at baseline and every three months with an Antera 3D, Miravex© camera. Clinical and 3D images were performed at each clinical check almost every three months. In this retrospective study, 331 patients (56.7% male, 43.3% female) were treated with DL-PDT. We observed a full clearance in more than two-thirds of patients with one or two treatments. Different responses depend on the number of lesions and on their severity; for patients with 1–3 lesions and with grade I or II AK, a full clearance was reached in 85% of cases with a maximum of two treatments. DL-PDT in general improved skin tone and erased sun damage. Evaluating each Antera 3D images, hemoglobin concentration and pigmentation, a skin color and tone improvement in 310 patients was observed. DL-PDT appears as a promising, effective, simple, tolerable and practical treatment for actinic damage associated with AK, and even treatment of large areas can be with little or no pain. The 3D imaging allowed for quantifying in real time the aesthetic benefits of DL

  5. MAL Daylight Photodynamic Therapy for Actinic Keratosis: Clinical and Imaging Evaluation by 3D Camera.

    PubMed

    Cantisani, Carmen; Paolino, Giovanni; Pellacani, Giovanni; Didona, Dario; Scarno, Marco; Faina, Valentina; Gobello, Tommaso; Calvieri, Stefano

    2016-07-11

    Non-melanoma skin cancer is the most common skin cancer with an incidence that varies widely worldwide. Among them, actinic keratosis (AK), considered by some authors as in situ squamous cell carcinoma (SCC), are the most common and reflect an abnormal multistep skin cell development due to the chronic ultraviolet (UV) light exposure. No ideal treatment exists, but the potential risk of their development in a more invasive form requires prompt treatment. As patients usually present with multiple AK on fields of actinic damage, there is a need for effective, safe, simple and short treatments which allow the treatment of large areas. To achieve this, daylight photodynamic therapy (DL-PDT) is an innovative treatment for multiple mild actinic keratosis, well tolerated by patients. Patients allocated to the PDT unit, affected by multiple mild-moderate and severe actinic keratosis on sun-exposed areas treated with DL-PDT, were clinically evaluated at baseline and every three months with an Antera 3D, Miravex(©) camera. Clinical and 3D images were performed at each clinical check almost every three months. In this retrospective study, 331 patients (56.7% male, 43.3% female) were treated with DL-PDT. We observed a full clearance in more than two-thirds of patients with one or two treatments. Different responses depend on the number of lesions and on their severity; for patients with 1-3 lesions and with grade I or II AK, a full clearance was reached in 85% of cases with a maximum of two treatments. DL-PDT in general improved skin tone and erased sun damage. Evaluating each Antera 3D images, hemoglobin concentration and pigmentation, a skin color and tone improvement in 310 patients was observed. DL-PDT appears as a promising, effective, simple, tolerable and practical treatment for actinic damage associated with AK, and even treatment of large areas can be with little or no pain. The 3D imaging allowed for quantifying in real time the aesthetic benefits of DL

  6. Actinic Keratosis Clinical Practice Guidelines: An Appraisal of Quality

    PubMed Central

    Kirby, Joslyn S.; Scharnitz, Thomas; Seiverling, Elizabeth V.; Ahrns, Hadjh; Ferguson, Sara

    2015-01-01

    Actinic keratosis (AK) is a common precancerous skin lesion and many AK management guidelines exist, but there has been limited investigation into the quality of these documents. The objective of this study was to assess the strengths and weaknesses of guidelines that address AK management. A systematic search for guidelines with recommendations for AK was performed. The Appraisal of Guidelines for Research and Evaluation (AGREE II) was used to appraise the quality of guidelines. Multiple raters independently reviewed each of the guidelines and applied the AGREE II tool and scores were calculated. Overall, 2,307 citations were identified and 7 fulfilled the study criteria. The Cancer Council of Australia/Australian Cancer Network guideline had the highest mean scores and was the only guideline to include a systematic review, include an evidence rating for recommendations, and report conflicts of interest and funding sources. High-quality, effective guidelines are evidence-based with recommendations that are concise and organized, so practical application is facilitated. Features such as concise tables, pictorial diagrams, and explicit links to evidence are helpful. However, the rigor and validity of some guidelines were weak. So, it is important for providers to be aware of the features that contribute to a high-quality, practical document. PMID:26451140

  7. Histopathological analysis of the therapeutic response to cryotherapy with liquid nitrogen in patients with multiple actinic keratosis*

    PubMed Central

    de Oliveira, Marina Câmara; Trevisan, Flávia; Pinto, Clovis Antônio Lopes; Xavier, Célia Antônia; Pinto, Jaqueline Campoi Calvo Lopes

    2015-01-01

    Actinic keratoses are premalignant lesions of the skin caused by excessive sun exposure. Lesions may become mainly squamous cell carcinoma. Cryotherapy with liquid nitrogen is one of the main treatments. In order to evaluate the response of actinic keratosis to cryotherapy by histopathology, two lesions were selected in each of 14 patients with multiple actinic keratoses. In one lesion a biopsy was performed and in the other lesion a biopsy was performed after cryotherapy. Subsequently, both biopsies were compared histologically. Of the thirteen patients who completed the study, the best results were obtained in lesions undergoing cryotherapy concerning the atypia of keratinocytes, epithelial thickness and corneal layer and lymphocytic infiltrate. Despite the small number of patients, it was concluded that, if performed correctly, cryotherapy has high efficacy in the treatment of actinic keratoses. PMID:26131870

  8. Histopathological analysis of the therapeutic response to cryotherapy with liquid nitrogen in patients with multiple actinic keratosis.

    PubMed

    Oliveira, Marina Câmara de; Trevisan, Flávia; Pinto, Clovis Antônio Lopes; Xavier, Célia Antônia; Pinto, Jaqueline Campoi Calvo Lopes

    2015-01-01

    Actinic keratoses are premalignant lesions of the skin caused by excessive sun exposure. Lesions may become mainly squamous cell carcinoma. Cryotherapy with liquid nitrogen is one of the main treatments. In order to evaluate the response of actinic keratosis to cryotherapy by histopathology, two lesions were selected in each of 14 patients with multiple actinic keratoses. In one lesion a biopsy was performed and in the other lesion a biopsy was performed after cryotherapy. Subsequently, both biopsies were compared histologically. Of the thirteen patients who completed the study, the best results were obtained in lesions undergoing cryotherapy concerning the atypia of keratinocytes, epithelial thickness and corneal layer and lymphocytic infiltrate. Despite the small number of patients, it was concluded that, if performed correctly, cryotherapy has high efficacy in the treatment of actinic keratoses.

  9. Lumican as a novel marker for differential diagnosis of Bowen disease and actinic keratosis.

    PubMed

    Takayama, Ryoko; Ishiwata, Toshiyuki; Ansai, Shin-ichi; Yamamoto, Tetsushi; Matsuda, Yoko; Naito, Zenya; Kawana, Seiji

    2013-12-01

    Lumican, a member of the small leucine-rich proteoglycan family, regulates the assembly and diameter of collagen fibers in the extracellular matrix of various tissues. Lumican expression correlates with pathological conditions, including skin fragility, corneal opacification, and corneal and cardiac wound healing. Lumican is overexpressed in tumor cells, including in the breast, colorectal, neuroendocrine cell, uterine cervical, and pancreatic cancers. Lumican expression also correlates with the growth and metastasis of various malignancies. For example, lumican expression is lower in the dermis of malignant melanoma cases than in early-stage melanomas. However, the expression patterns and roles of lumican in nonmelanoma skin cancer have not been elucidated. In this study, we used immunohistochemistry and in situ hybridization to examine the expression patterns of lumican in normal skin, Bowen disease, and actinic keratosis. In normal skin, lumican was expressed in the collagen fibers in the dermis, acrosyringium, follicular epithelium, and sebocytes but not in epidermal keratinocytes. In Bowen disease, lumican was expressed in 34 (91.8%) of 37 patients. Notably, all cases of actinic keratosis were negative for lumican. These findings suggest that lumican plays an important role in the pathogenesis of Bowen disease and actinic keratosis and might be useful as an adjunct to the diagnosis for subtypes of 2 diseases: bowenoid actinic keratosis and Bowen disease in sun-exposed areas.

  10. Efficacy of a Film-Forming Medical Device Containing Piroxicam and Sun Filters in the Treatment of Multiple Actinic Keratosis Lesions in a Subject with a History of Kaposi Sarcoma

    PubMed Central

    Scotti, Elisabetta; Deledda, Salvatore; Milani, Massimo

    2016-01-01

    Actinic keratosis (AK) is considered a premalignant form of skin cancer due to chronic sun exposure. In addition, human papilloma virus (HPV) has been advocated a role in the pathogenesis of this clinical condition. HPV proteins (mainly E6 and E7) seem to act synergistically with ultraviolet (UV) radiation in reducing the defensive mechanisms of keratinocyte apoptosis after UV damage. Data regarding the involvement of other viruses, i.e. human herpes viruses (HHV), in the pathogenesis of AK are so far controversial. HHV8 is considered the infective agent involved in the development of Kaposi sarcoma. Some experimental data have shown that AK lesions carry HHV8 in more than 30% of the bioptic samples. Topical piroxicam was shown to be effective in the treatment of AK. In addition, the molecule shows antiviral action against HPV and HHV8. Here, we report the efficacy of a medical device containing a film-forming substance (polyvinyl alcohol), chemical and physical sun filters (SPF 50+), and 0.8% piroxicam (Actixicam™, Difa Cooper; ACTX) in the treatment of multiple scalp AK lesions, unresponsive to other treatments, in a subject with Kaposi sarcoma and a history of severe contact dermatitis. The subject presented with severe involvement of the scalp, with multiple hypertrophic AK lesions. Previous lesion-directed and field-targeted treatments have not been effective. The subject was treated with ACTX applied twice daily on the affected scalp. Relevant clinical improvement was observed as soon as 1 month of therapy. Complete clinical resolution of all scalp lesions was observed after 3 months of treatment. The product was well tolerated. PMID:28101017

  11. Field cancerization: from molecular basis to selective field-directed management of actinic keratosis.

    PubMed

    Philipp-Dormston, Wolfgang G

    2015-01-01

    The incidence of non-melanoma skin cancer (NMSC), including actinic keratosis (AK), squamous cell carcinoma (SCC), Bowen's Disease (BD) and basal cell carcinoma (BCC), is increasing. UVA and UVB radiation lead to genetic alterations in keratinocytes, which eventually result in skin cancer. In the concept of field cancerization of the skin, genetically altered keratinocytes accumulate over an area exposed to UV radiation. Field treatment not only clears clinically visible NMSC lesions but also potentially targets subclinical 'sleeping' cell patches and fields. Topical treatments are available for the field-directed management of NMSC. They are either self-administered by the patient (ingenol mebutate, diclofenac, imiquimod or 5-FU) or administered by the dermatologist (photodynamic therapy (PDT)). This article discusses the treatment options with respect to their efficacy, tolerability and selectivity. Selective treatment options for atypic keratinocytes include imiquimod, ingenol mebutate, diclofenac and PDT. PDT yields 100% treatment compliance because it is always administered by the treating dermatologist. The efficacy rates achieved with PDT significantly exceed those of the patient-administered topicals. The first clinical trials assessing the effects of PDT on field cancerization clinically, histologically and immunochemically have been conducted and have yielded promising results. Preventive effects and a delay in the re-occurrence of NMSC have been observed in animal experiments of ingenol mebutate and PDT, whereas for the latter, clinical data are already available.

  12. The importance of treating the field in actinic keratosis.

    PubMed

    Stockfleth, E

    2017-03-01

    Actinic keratoses (AKs) are intraepithelial atypical proliferations of keratinocytes that develop in skin that has undergone long-term exposure to ultraviolet radiation. Given the ageing population and an increasing prevalence of AK, the socio-economic burden of AK is likely to rise over the coming years. Areas of subclinical (non-visible) sun damage in the periphery of visible AK lesions contain the same genetic changes as those found in the lesions themselves, and are known as areas of field cancerization. AK lesions and the field are associated with an increased risk of skin cancer, including invasive squamous cell carcinoma. Although effective in clearing visible AK, lesion-directed therapies do not address field cancerization and can lead to high recurrence rates. In contrast, field-directed therapies, such as ingenol mebutate, imiquimod and diclofenac, can clear both visible and subclinical AK lesions and reduce the development of new lesions in the treated field. Additionally, preclinical studies suggest that field therapy may prevent or delay the recurrence of non-melanoma skin cancer. AK treatment guidelines now recognize the importance of treating the field in patients with AK, and adaptation of treatment guidelines into clinical practice is warranted. Physician and patient education around the consequences of leaving the field of cancerization untreated is necessary in order to reduce the increasing burden associated with AK.

  13. Ingenol mebutate: A novel topical drug for actinic keratosis

    PubMed Central

    Aditya, Suruchi; Gupta, Sanjeev

    2013-01-01

    The global incidence of non-melanoma skin cancer is rising. Significant morbidity leading to unacceptable cosmetic outcomes and/or functional impairment is a major concern. Search for non-surgical, non-invasive and tissue-sparing treatment modalities has led to development of new therapeutic agents. Actinic keratoses (AK) are one part of a continuous spectrum of benign sun damage to squamous cell carcinoma (SCC). Although it is not possible to predict which AK might progress to SCC, the presence of AK is a biomarker of risk for patients and must be treated to avoid possible morbidity and mortality. Ingenol mebutate is a novel topical drug from the latex sap of a plant-Euphorbia peplus that acts by chemoablative and immunostimulatory properties. Clinical studies have proven it to be safe and efficacious, leading to FDA approval of this chemotherapeutic agent for field therapy of AK in 2012. Current topical agents for field therapy of AK must be applied for weeks, whereas ingenol needs to be applied for three days. Ingenol offers a new therapeutic option that is convenient, safe, effective, acceptable and well-tolerated. PMID:23984250

  14. Pharmacotherapeutic management of actinic keratosis: focus on newer topical agents.

    PubMed

    Samrao, Aman; Cockerell, Clay J

    2013-08-01

    Actinic (solar) keratoses (AK) have the potential for malignant transformation and are the second most common diagnosis in dermatologic practices. No well-established clinical criteria are available to determine which AK are more likely to undergo malignant transformation; therefore, many dermatologists utilize field-directed approaches to treat all visible and subclinical AK on an affected skin surface. Current topical therapeutic agents require lengthy treatment regimens and are less well tolerated than many newer and investigational agents. We review and compare the efficacy and tolerability of well-established topical agents for the management of AK in the United States including 5-fluorouracil, imiquimod 5% cream as well as the newer 2.5 and 3.75% formulations, diclofenac 3% gel, photodynamic therapy, and the recently approved ingenol mebutate gel and discuss the therapeutic potential of investigational agents. Cryotherapy and 5-fluorouracil are efficacious at treating AK but less tolerable than imiquimod cream, particularly at its lower concentrations. The newer agents, diclofenac gel and ingenol mebutate, appear to be more tolerable than cryotherapy and 5- fluorouracil; however, comparative studies regarding efficacy are not available.

  15. Solar keratosis: epidemiology, pathogenesis, presentation and treatment.

    PubMed

    Holmes, Cara; Foley, Peter; Freeman, Michael; Chong, Alvin H

    2007-05-01

    Solar keratosis is a common problem encountered by dermatologists, particularly in Australia. Solar keratosis is most commonly found on sun-exposed areas such as the scalp, face and forearms. UV radiation is thought to be the major aetiological factor, with age, immunosuppression and human papillomavirus being important contributing factors. Solar keratosis usually presents as a discrete, variably erythematous and irregular lesion with a scaly surface. Although the exact rate of malignant transformation to squamous cell carcinoma is unknown, the majority of squamous cell carcinomas appear to arise from within solar keratosis. For this reason, solar keratosis is commonly treated and, consequently, an increasing number of therapeutic options is now available. Traditional therapies, such as liquid nitrogen cryotherapy, are still popular, but newer choices, such as photodynamic therapy and imiquimod cream, are now providing further options with similar efficacy and superior adverse effect profiles, albeit at a higher cost.

  16. Defining Field Cancerization of the Skin Using Noninvasive Optical Coherence Tomography Imaging to Detect and Monitor Actinic Keratosis in Ingenol Mebutate 0.015%- Treated Patients

    PubMed Central

    Schwartz, Michelle; Feldman, Eleanor; Bieber, Amy; Bienenfeld, Amanda; Nandanan, Naveen; Siegel, Daniel M.

    2016-01-01

    Objective: The objective of this study was to assess the ability of optical coherence tomography to detect clinical and subclinical actinic keratoses confirmed by histopathology. The efficacy of ingenol mebutate treatment of actinic keratosis was also evaluated using optical coherence tomography, and correlation of treatment efficacy with severity of local skin reactions was determined. Design: Single-arm, open-label, split-face study. Setting: Hospital outpatient clinic. Participants: Male subjects (N=30) with seven actinic keratoses. Measurements: A suspected actinic keratosis and the normal-appearing, perilesional skin were imaged, biopsied for histopathologic analysis, and the results compared with the clinical and a blinded optical coherence tomography diagnosis. Treatment with ingenol mebutate gel 0.015% was randomly administered to three clinically suspected actinic keratoses and the perilesional skin; three additional, suspected actinic keratoses lesions and perilesional areas were left untreated. Clinical and optical coherence tomography images were obtained for all lesions. Severity of local skin reactions was recorded to evaluate the relationship between local skin reaction and treatment effect. Results: Optical coherence tomography analysis had a 100-percent (28/28) correlation with the clinical diagnosis of actinic keratosis and detected 16 of 22 (73%) histopathologically confirmed subclinical lesions from perilesional skin sites. By optical coherence tomography assessment, the clearance rate for clinically observed lesions was 76 percent for ingenol mebutate-treated areas versus 11 percent for untreated areas; the clearance rate for treated subclinical lesions was 88 percent versus 43 percent for untreated areas. Clearance rates did not vary with the severity of the local response. Conclusion: Optical coherence tomography is effective at detecting clinical and subclinical actinic keratoses and monitoring their response to treatment. PMID:27386042

  17. Mycosis fungoides patient accompanied actinic keratosis, actinic keratosis with squamous cell carcinoma transformation, and porokeratosis after NBUVB therapy – 1st case report and review of the literature

    PubMed Central

    Zhao, Meng-jie; Abdul-fattah, Bilal; Qu, Xiao-ying; Wang, Cui-yan; Wang, Xia; Ran, Yi; Lai, Ting; Chen, Si-yuan; Huang, Chang-zheng

    2016-01-01

    Abstract Introduction: Mycosis fungoides (MF) is the most common form of primary cutaneous T cell lymphoma. Narrowband ultraviolet B light (NBUVB) is used increasingly in treating MF because of its good toleration and well-established management. Concerns: To discuss the risk factors and underlying pathogenic factors in the patients with secondary skin diseases after NBUVB therapy. Methods: We report in details the first case of a patient with MF accompanied with actinic keratosis (AK), AK with squamous cell carcinoma (SCC) transformation and porokeratosis after NBUVB therapy. Meanwhile, Sequence variants in tumor suppressor p53 gene in the patient's specimens were detected. A literature search of the key word “narrowband ultraviolet B light ”and “side effects” was performed on PubMed, 14 cases of this entity were found. A total of 15 patients including our case were reviewed in this study and meaningful conclusion could be drawn. Outcomes: The mean age at diagnosis of secondary skin dermatoses after NBUVB therapy was 62.08 years with a male to female ratio of 2:1. The cases were reported more in Europeans than in Asians (2.75:1), and the Fitzpatrick skin type was mainly Ito III (12/15). The mean cumulative number and cumulative dose of UVB treatments were 43.71 and 42, 400 (mJ/cm2), respectively. There was a positive relationship between Fitzpatrick skin type and cumulative dose of UVB treatments. Among the secondary skin diseases after NBUVB treatment, 12 were tumors, 2 were non-tumorous dermatoses. Only our patient presented with both. By polymerase chain reaction-single nucleotide polymorphism (PCR-SNP) analysis, C–G mutation of exon 4 of p53 was found in AK and MF specimens in our patient. Conclusion: To our knowledge, our case is the first MF patient accompanied with AK, AK with SCC transformation and Porokeratosis after NBUVB treatment. Lower Fitzpatrick skin type may be the risk factor of secondary skin diseases after NBUVB treatment. PMID

  18. Efficacy of ingenol mebutate gel for actinic keratosis in patients treated by thiazide diuretics

    PubMed Central

    Campione, Elena; Di Prete, Monia; Diluvio, Laura; Bianchi, Luca; Orlandi, Augusto

    2016-01-01

    Actinic keratosis (AK) is considered as superficial squamous cell carcinoma. Chronic sun exposure plays a central role in its pathogenesis. In particular, ultraviolet B radiation causes direct damage to the DNA, producing pyrimidine dimers that suppress the protective role of p53. Other risk factors include advanced age, male sex, and fair skin type. Even some drugs used for treating blood hypertension, such as thiazide diuretics, can increase the risk of developing AK. Their photosensitizing action seems to be connected with reactive oxygen species production. We report our experience with ten patients affected by multiple AK, in therapy with thiazide diuretics, treated by ingenol mebutate gel. AK was clinically and dermoscopically evaluated at baseline and after 30 days from the beginning of the treatment. Moreover, patients were screened for vitamin D3 values and reported a general hypovitaminosis status. To our knowledge, we report for the first time the efficacy of ingenol mebutate gel in this group of patients, particularly at risk of developing AK. PMID:27853385

  19. Monitoring blood volume and saturation using superficial fibre optic reflectance spectroscopy during PDT of actinic keratosis.

    PubMed

    Middelburg, Tom A; Kanick, Stephen C; de Haas, Ellen R M; Sterenborg, Henricus J C M; Amelink, Arjen; Neumann, Martino H A M; Robinson, Dominic J

    2011-10-01

    Optically monitoring the vascular physiology during photodynamic therapy (PDT) may help understand patient-specific treatment outcome. However, diffuse optical techniques have failed to observe changes herein, probably by optically sampling too deep. Therefore, we investigated using differential path-length spectroscopy (DPS) to obtain superficial measurements of vascular physiology in actinic keratosis (AK) skin. The AK-specific DPS interrogation depth was chosen up to 400 microns in depth, based on the thickness of AK histology samples. During light fractionated aminolevulinic acid-PDT, reflectance spectra were analyzed to yield quantitative estimates of blood volume and saturation. Blood volume showed significant lesion-specific changes during PDT without a general trend for all lesions and saturation remained high during PDT. This study shows that DPS allows optically monitoring the superficial blood volume and saturation during skin PDT. The patient-specific variability supports the need for dosimetric measurements. In DPS, the lesion-specific optimal interrogation depth can be varied based on lesion thickness.

  20. Mucin1 expression in focal epidermal dysplasia of actinic keratosis

    PubMed Central

    Carrillo, Luz Marina; Rojas, Héctor; Ramírez, Richard; Reyes, Oscar; Suárez, Ambar; Ortega, Fabiana

    2015-01-01

    Background Actinic keratoses (AKs) are generally considered as premalignant skin lesions that can progress into squamous cell carcinoma (SCC) in situ and invasive SCC. However, its progression to SCC is still matter of debate. A transmembrane glycoprotein that contributes to the progression of certain premalignant and malignant lesions is mucin1 (MUC1). Nevertheless, their functions in the skin lesions are not yet fully clear. Therefore, the aim of this study is to ascertain whether MUC1 is present in the focal epidermal dysplasia of AK. Methods Fourteen skin biopsies from patients diagnosed with AK were selected. They were classified according to the degree of dysplasia in keratinocyte intraepidermal neoplasia (KIN) I, KIN II, and KIN III. In five biopsies the three degrees were present, in two biopsies both KIN I and KIN II, in four biopsies only KIN I, and in three biopsies only KIN III. The presence of MUC1 was assessed by immunofluorescence staining using confocal laser scanning microscopy. Results Immunostaining revealed that MUC1 was present over the entire cell surface of only a few atypical basal keratinocytes confined to the lower third of the epidermis (KIN I). While in KIN II where atypical keratinocytes occupy the lower two thirds, MUC1 was localized at the apical surface of some atypical keratinocytes and over the entire cell surface of some of them. Interestingly, in KIN III where the atypical keratinocytes extend throughout the full thickness, MUC1 was localized at the apical surface and over the entire cell surface of many of these cells. Conversely, MUC1 expression was not detected in the epidermis of normal skin. Conclusions Our findings suggest that the expression of MUC1 in AK would be induced by alteration of keratinocyte stratification and differentiation and associated to the degree of dysplasia rather than the thickness of the epidermis. PMID:26605291

  1. A survey of office visits for actinic keratosis as reported by NAMCS, 1990-1999. National Ambulatory Medical Care Survey.

    PubMed

    Gupta, Aditya K; Cooper, Elizabeth A; Feldman, Steven R; Fleischer, Alan B

    2002-08-01

    Although actinic keratosis (AK) has been linked to the development of nonmelanoma skin cancer (NMSC), particularly squamous cell carcinoma (SCC), increased awareness regarding diagnosis and treatment may be an important component for reducing morbidity and even mortality from AK and NMSC. We used the National Ambulatory Medical Care Survey (NAMCS) data from 1990 to 1999 to evaluate the diagnosis and treatment of AKs among a wide variety of patients by physicians across the United States. To our knowledge, no widespread surveys of North American populations have been performed recently to determine the epidemiology of AK. AK was diagnosed in more than 47 million visits over the 10-year period surveyed and was found to occur in 14% of patients visiting dermatologists. The diagnosis of AK as determined by NAMCS does not reflect the true prevalence of AK because only patients seeking physician diagnosis were surveyed. This suggests that the actual number of patients in the United States with AK is much higher than 14%. Rates of AK diagnosis in the standard metropolitan statistical areas (SMSAs) and non-standard metropolitan statistical areas (non-SMSAs) of the West states are higher than in other states, but geographic location may not be a direct risk factor for the development of AKs. Procedures were undertaken at 70% of visits where AK was the primary diagnosis. Destruction of lesions was the most frequently performed procedure found in the survey considering only the 1993 and 1994 NAMCS data. Biopsy was the second most frequently performed procedure.

  2. Predisposing factors of actinic keratosis in a North-West German population.

    PubMed

    Hensen, Peter; Müller, Marcel L; Haschemi, Ramin; Ständer, Hartmut; Luger, Thomas A; Sunderkötter, Cord; Schiller, Meinhard

    2009-01-01

    The growing incident rates of skin cancer and their corresponding precursor lesions, e.g. actinic keratosis (AK), among Caucasians have become an important public health problem. A multicenter case-control study was conducted to identify the risk factors of AK of a prototypical Central European population. The study population comprised a total of 331 cases and 383 controls. Using multivariate analysis we identified ten independent variables predicting the AK risk. The five most crucial were age (OR 1.11; 95% CI 1.08-1,14), gender (OR 3.92; 95% CI 2.42-6.36), history of previous skin malignancies (OR 6.47; 95% CI 3.21-13.03), pale skin phototype (OR 2.5; 95% CI 1.53-4.06), and sun exposure for occupational reasons (OR 1.72; 95% CI 1.01-2.92). Additionally, sun exposure for recreational reasons, denial of the use of sunscreens, painful sunburn episodes before the age of 20, and a familial history of skin malignancies are also significant independent correlates of AK. Our epidemiological data suggest that constitutional susceptibility and sunlight exposure are equally involved in the onset of AK. Additional prophylactic and educational efforts should focus on increasing sun protection policies and educational programs especially aimed at outdoor workers, men, fair skinned individuals and patients with a history of previous skin malignancies. These measures should be able to reduce the excessive incidence rates of AK among Caucasians in Central Europe.

  3. Nuclear morphometry and molecular biomarkers of actinic keratosis, sun-damaged, and nonexposed skin.

    PubMed

    Carpenter, Philip M; Linden, Kenneth G; McLaren, Christine E; Li, Kuo-Tung; Arain, Shehla; Barr, Ronald J; Hite, Pamela; Sun, Joannie D; Meyskens, Frank L

    2004-12-01

    Computer-assisted image analysis is useful for quantifying the histologic and molecular changes of sun-induced squamous cell carcinoma progression. We used the CAS 200 image analysis system to measure nuclear morphometric parameters, p53 expression, and proliferation markers in actinic keratosis (AK), sun-exposed, and normal skin in 51 patients. Nuclear morphometry revealed significant increases in nuclear absorbance, irregularity of nuclear shape, and nuclear size in AK compared with normal and sun-damaged skin. These parameters showed significantly greater variability in AK nuclei. Argyrophyllic nucleolar organizer area and number were also significantly greater in AK compared with sun-damaged skin and normal skin. Ki67 and p53 expressions were both increased in sun-damaged skin relative to normal and greater still in AK. These data are evidence that sun damage induces proliferation and p53 abnormalities before the appearance of nuclear abnormalities and their associated DNA instability. Following these changes during a skin cancer chemopreventative trial can then help assess the efficacy of the agent and help determine where in the progression of neoplastic changes it exerts its biological effects.

  4. Photodynamic therapy: treatment of choice for actinic cheilitis?

    PubMed

    Rossi, R; Assad, G Bani; Buggiani, G; Lotti, T

    2008-01-01

    The major therapeutic approaches (5-fluorouracil, imiquimod, vermilionectomy, and CO(2) Laser ablation) for actinic cheilitis are aimed at avoiding and preventing a malignant transformation into invasive squamous cell carcinoma via destruction/removal of the damaged epithelium. Recently, photodynamic therapy (PDT) has been introduced as a therapeutic modality for epithelial skin tumors, with good efficacy/safety profile and good cosmetic results. Regarding actinic cheilitis, PDT could be considered a new therapeutic option? The target of our study was to evaluate the efficacy and tolerability of PDT in actinic cheilitis, using a methyl-ester of aminolevulinic acid (MAL) as topical photosensitizing agent and controlled the effects of the therapy for a 30-month follow-up period. MAL-PDT seems to be the ideal treatment for actinic cheilitis and other actinic keratosis, especially on exposed parts such as the face, joining tolerability and clinical efficacy with an excellent cosmetic outcome.

  5. Ingenol mebutate gel treatment for actinic cheilitis: report of four cases.

    PubMed

    Barrado Solís, Nerea; Molés Poveda, Paula; Lloret Ruiz, César; Pont Sanjuan, Virginia; Velasco Pastor, Manel; Quecedo Estébanez, Esther; Miquel Miquel, Javier

    2015-01-01

    Actinic cheilitis (AC) are premalignant lesions that have an increased risk of malignant transformation. Their treatment, therefore, is essential to prevent carcinogenesis. However, optimal therapy is not well established and different modalities yield variable results. Ingenol mebutate gel has recently been approved by the US Food and Drug Administration for topical treatment of actinic keratosis, with high clearance rates. On the basis of these findings, we report our experience with this drug for the treatment of AC.

  6. Dual-channel red/blue fluorescence dosimetry with broadband reflectance spectroscopic correction measures protoporphyrin IX production during photodynamic therapy of actinic keratosis

    NASA Astrophysics Data System (ADS)

    Kanick, Stephen Chad; Davis, Scott C.; Zhao, Yan; Hasan, Tayyaba; Maytin, Edward V.; Pogue, Brian W.; Chapman, M. Shane

    2014-07-01

    Dosimetry for aminolevulinic acid (ALA)-induced protoporphyrin IX (PpIX) photodynamic therapy of actinic keratosis was examined with an optimized fluorescence dosimeter to measure PpIX during treatment. While insufficient PpIX generation may be an indicator of incomplete response, there exists no standardized method to quantitate PpIX production at depths in the skin during clinical treatments. In this study, a spectrometer-based point probe dosimeter system was used to sample PpIX fluorescence from superficial (blue wavelength excitation) and deeper (red wavelength excitation) tissue layers. Broadband white light spectroscopy (WLS) was used to monitor aspects of vascular physiology and inform a correction of fluorescence for the background optical properties. Measurements in tissue phantoms showed accurate recovery of blood volume fraction and reduced scattering coefficient from WLS, and a linear response of PpIX fluorescence versus concentration down to 1.95 and 250 nM for blue and red excitations, respectively. A pilot clinical study of 19 patients receiving 1-h ALA incubation before treatment showed high intrinsic variance in PpIX fluorescence with a standard deviation/mean ratio of >0.9. PpIX fluorescence was significantly higher in patients reporting higher pain levels on a visual analog scale. These pilot data suggest that patient-specific PpIX quantitation may predict outcome response.

  7. Dual-channel red/blue fluorescence dosimetry with broadband reflectance spectroscopic correction measures protoporphyrin IX production during photodynamic therapy of actinic keratosis

    PubMed Central

    Kanick, Stephen Chad; Davis, Scott C.; Zhao, Yan; Hasan, Tayyaba; Maytin, Edward V.; Pogue, Brian W.; Chapman, M. Shane

    2014-01-01

    Abstract. Dosimetry for aminolevulinic acid (ALA)-induced protoporphyrin IX (PpIX) photodynamic therapy of actinic keratosis was examined with an optimized fluorescence dosimeter to measure PpIX during treatment. While insufficient PpIX generation may be an indicator of incomplete response, there exists no standardized method to quantitate PpIX production at depths in the skin during clinical treatments. In this study, a spectrometer-based point probe dosimeter system was used to sample PpIX fluorescence from superficial (blue wavelength excitation) and deeper (red wavelength excitation) tissue layers. Broadband white light spectroscopy (WLS) was used to monitor aspects of vascular physiology and inform a correction of fluorescence for the background optical properties. Measurements in tissue phantoms showed accurate recovery of blood volume fraction and reduced scattering coefficient from WLS, and a linear response of PpIX fluorescence versus concentration down to 1.95 and 250 nM for blue and red excitations, respectively. A pilot clinical study of 19 patients receiving 1-h ALA incubation before treatment showed high intrinsic variance in PpIX fluorescence with a standard deviation/mean ratio of >0.9. PpIX fluorescence was significantly higher in patients reporting higher pain levels on a visual analog scale. These pilot data suggest that patient-specific PpIX quantitation may predict outcome response. PMID:24996661

  8. Electrospun poly-l-lactide scaffold for the controlled and targeted delivery of a synthetically obtained Diclofenac prodrug to treat actinic keratosis.

    PubMed

    Piccirillo, Germano; Bochicchio, Brigida; Pepe, Antonietta; Schenke-Layland, Katja; Hinderer, Svenja

    2016-11-02

    Actinic Keratosis' (AKs) are small skin lesions that are related to a prolonged sun-damage, which can develop into invasive squamous cell carcinoma (SCC) when left untreated. Effective, specific and well tolerable therapies to cure AKs are still of great interest. Diclofenac (DCF) is the current gold standard for the local treatment of AKs in terms of costs, effectiveness, side effects and tolerability. In this work, an electrospun polylactic acid (PLA) scaffold loaded with a synthetic DCF prodrug was developed and characterized. Specifically, the prodrug was successfully synthetized by binding DCF to a glycine residue via solid phase peptide synthesis (SPPS) and then incorporated in an electrospun PLA scaffold. The drug encapsulation was verified using multiphoton microscopy (MPM) and its scaffold release was spectrophotometrically monitored and confirmed with MPM. The scaffold was further characterized with scanning electron microscopy (SEM), tensile testing and contact angle measurements. Its biocompatibility was verified by performing a cell proliferation assay and compared to PLA scaffolds containing the same amount of DCF sodium salt (DCFONa). Finally, the effect of the electrospun scaffolds on human dermal fibroblasts (HDFs) morphology and metabolism was investigated by combining MPM with fluorescence lifetime imaging microscopy (FLIM). The obtained results suggest that the obtained scaffold could be suitable for the controlled and targeted delivery of the synthesized prodrug for the treatment of AKs.

  9. IRF4, MC1R and TYR genes are risk factors for actinic keratosis independent of skin color.

    PubMed

    Jacobs, Leonie C; Liu, Fan; Pardo, Luba M; Hofman, Albert; Uitterlinden, André G; Kayser, Manfred; Nijsten, Tamar

    2015-06-01

    Actinic keratosis (AK) is a pre-malignant skin disease, highly prevalent in elderly Europeans. This study investigates genetic susceptibility to AK with a genome-wide association study (GWAS). A full body skin examination was performed in 3194 elderly individuals from the Rotterdam Study (RS) of exclusive north-western European origin (aged 51-99 years, 45% male). Physicians graded the number of AK into four severity levels: none (76%), 1-3 (14%), 4-9 (6%) and ≥10 (5%), and skin color was quantified using a spectrophotometer on sun-unexposed skin. A GWAS for AK severity was conducted, where promising signals at IRF4 and MC1R (P < 4.2 × 10(-7)) were successfully replicated in an additional cohort of 623 RS individuals (IRF4, rs12203592, Pcombined = 6.5 × 10(-13) and MC1R, rs139810560, Pcombined = 4.1 × 10(-9)). Further, in an analysis of ten additional well-known human pigmentation genes, TYR also showed significant association with AK (rs1393350, P = 5.3 × 10(-4)) after correction for multiple testing. Interestingly, the strength and significance of above-mentioned associations retained largely the same level after skin color adjustment. Overall, our data strongly suggest that IRF4, MC1R and TYR genes likely have pleiotropic effects, a combination of pigmentation and oncogenic functions, resulting in an increased risk of AK.

  10. Protein expression of MMP-2 and MT1-MMP in actinic keratosis, squamous cell carcinoma of the skin, and basal cell carcinoma.

    PubMed

    de Oliveira Poswar, Fabiano; de Carvalho Fraga, Carlos Alberto; Gomes, Emisael Stênio Batista; Farias, Lucyana Conceição; Souza, Linton Wallis Figueiredo; Santos, Sérgio Henrique Souza; Gomez, Ricardo Santiago; de-Paula, Alfredo Maurício Batista; Guimarães, André Luiz Sena

    2015-02-01

    Squamous cell carcinoma (SCC) and basal cell carcinoma (BCC) are 2 skin neoplasms with distinct potentials to invasion and metastasis. Actinic keratosis (AK) is a precursor lesion of SCC. Immunohistochemistry was performed to evaluate the expression of MMP-2 and MT1-MMP in samples of BCC (n = 29), SCC (n = 12), and AK (n = 13). The ratio of positive cells to total cells was used to quantify the staining. Statistical significance was considered under the level P < .05. We found a higher expression of MMP-2 in tumor stroma and parenchyma of SCC as compared to BCC. The expression of this protein was also similar between SCC and its precursor actinic keratosis, and it was higher in the stroma of high-risk BCC when compared to low-risk BCC. MT1-MMP, which is an activator of MMP-2, was similarly expressed in all groups. Our results suggest that MMP-2 expression may contribute to the distinct invasive patterns seen in SCC and BCC.

  11. Optimal treatment of actinic keratoses

    PubMed Central

    Uhlenhake, Elizabeth E

    2013-01-01

    The most compelling reason and primary goal of treating actinic keratoses is to prevent malignant transformation into invasive squamous cell carcinoma, and although there are well established guidelines outlining treatment modalities and regimens for squamous cell carcinoma, the more commonly encountered precancerous actinic lesions have no such standard. Many options are available with variable success and patient compliance rates. Prevention of these lesions is key, with sun protection being a must in treating aging patients with sun damage as it is never too late to begin protecting the skin. PMID:23345970

  12. Diclofenac Topical (actinic keratosis)

    MedlinePlus

    ... growths on the skin caused by too much sun exposure). Diclofenac is in a class of medications ... plan to avoid exposure to real and artificial sunlight (sun lamps) and to wear protective clothing and ...

  13. Topical treatment of actinic keratoses with potassium dobesilate 5% cream. A preliminary open-label study

    PubMed Central

    2011-01-01

    Background Fibroblast growth factor (FGF) is involved in skin tumorigenesis: it promotes cell viability, induces angiogenesis and stimulates invasiveness. Dobesilate is a drug that blocks the activity of FGF. The primary objective was to evaluate the efficacy and tolerability of potassium dobesilate 5% cream in the treatment of actinic keratoses. Methods Potassium dobesilate 5% cream was applied twice daily for 16 weeks to actinic keratosis lesions in 30 patients. The lesions were evaluated clinically at an initial baseline visit, at intermediate visits, and at 16 weeks of treatment. Results The use of potassium dobesilate 5% cream for 16 weeks induced complete regression in 70% of evaluated actinic keratoses, corresponding to grade I, II and III clinical variants, and a partial response (at least 75% reduction of lesions) in 20% of the cases. Conclusion Our preliminary trial shows that potassium dobesilate exerts anti-tumorigenic effects and may play a useful role in the chemoprevention of skin cancers. PMID:21463984

  14. Photodynamic therapy for the treatment of actinic cheilitis.

    PubMed

    Kodama, Makiko; Watanabe, Daisuke; Akita, Yoichi; Tamada, Yasuhiko; Matsumoto, Yoshinari

    2007-10-01

    Although actinic cheilitis is a common disease, it should be treated carefully because it can undergo malignant transformation. We report a case of actinic cheilitis treated with photodynamic therapy (PDT) using 5-aminolevulinic acid (ALA), with satisfactory outcome in both clinical and pathological aspects. Actinic cheilitis is a pathologic condition affecting mainly the lower lip caused by long-term exposure of the lips to the UV radiation in sunlight. Analogous to actinic keratosis of the skin, actinic cheilitis is considered as a precancerous lesion and it may develop into squamous cell carcinoma. We report a case of actinic cheilitis treated with PDT using ALA, with satisfactory outcome in both clinical and pathological aspects.

  15. Immunohistochemical analysis of TIMP-3 and MMP-9 in actinic keratosis, squamous cell carcinoma of the skin, and basal cell carcinoma.

    PubMed

    Poswar, Fabiano O; Fraga, Carlos A C; Farias, Lucyana C; Feltenberger, John D; Cruz, Vitória P D; Santos, Sérgio H S; Silveira, Christine M; de Paula, Alfredo M B; Guimarães, André L S

    2013-11-01

    The expression of metalloproteinases and their inhibitors has been related to different invasive and metastatic potentials in cancer. This study aims to investigate the immunohistochemical expression of TIMP-3 and MMP-9 in samples of basal cell carcinoma (BCC), squamous cell carcinoma of the skin (SCC), and actinic keratosis (AK). Immunohistochemistry was performed to evaluate the expression of TIMP-3 and MMP-9 in samples of BCC (n=22), SCC (n=10), and AK (n=15). Ten fields of both tumor parenchyma and tumor stroma were photographed and counted in image software. The ratio of positive cells to total cells was used to quantify the staining. A higher expression of MMP-9 was found in tumor stroma of SCC compared to BCC and AK. No significant differences in TIMP-3 expression were observed among the groups. Considering the well-described differences between these neoplasms, these results provide additional evidence of the role of MMP-9 in tumor invasiveness of keratinocyte-derived tumors.

  16. Real-life practice study of the clinical outcome and cost-effectiveness of photodynamic therapy using methyl aminolevulinate (MAL-PDT) in the management of actinic keratosis and basal cell carcinoma.

    PubMed

    Annemans, Lieven; Caekelbergh, Karin; Roelandts, Rik; Boonen, Hugo; Leys, Christoph; Nikkels, Arjen F; van Den Haute, V; van Quickenborne, L; Verhaeghe, Evelien; Leroy, Bernard

    2008-01-01

    Clinical trials have shown that photodynamic therapy using methyl aminolevulinate (MAL-PDT) is an effective treatment for actinic keratosis (AK), and nodular and superficial basal cell carcinoma (nBCC and sBCC) unsuitable for other available therapies. Economic evaluation models have shown that it is a cost effective intervention as well. The objectives of this prospective, observational, one arm study were (i) to verify in a real-life practice study the results obtained in previous clinical trials with MAL-PDT in the treatment of AK, nBCC and sBCC; (ii) to calculate the real-life cost of treatment and validate predictions from an economic evaluation model. Patients with AK and/or BCC were selected according to Belgian reimbursement criteria for treatment with MAL-PDT. Clinical response, cosmetic outcome and tolerability were assessed. MAL-PDT cost was calculated and compared to published model cost data. Data were collected from 247 patients (117 AK, 130 BCC). A complete clinical response was obtained for 83% of AK (85/102) and BCC (97/116) patients. A good or excellent cosmetic outcome was obtained for 95% of AK patients and 93% of BCC patients. Tolerability was good: only 2 patients withdrew for adverse events. Clinical results were similar to previous studies. Total cost of care per patient was euro 381 for AK, euro 318 for nBCC, and euro 298 for sBCC. Total cost per lesion was euro 58 for AK (identical to model prediction), euro 316 for nBCC and euro 178 for sBCC (both within 20% of model prediction). The clinical results of MAL-PDT in this real-life practice study confirm those demonstrated in previous clinical trials. Costs calculated from this study confirm predicted cost-effectiveness in the original model for MAL-PDT in the management of AK and BCC.

  17. [Photodynamic therapy for actinic cheilitis].

    PubMed

    Castaño, E; Comunión, A; Arias, D; Miñano, R; Romero, A; Borbujo, J

    2009-12-01

    Actinic cheilitis is a subtype of actinic keratosis that mainly affects the lower lip and has a higher risk of malignant transformation. Its location on the labial mucosa influences the therapeutic approach. Vermilionectomy requires local or general anesthetic and is associated with a risk of an unsightly scar, and the treatment with 5-fluorouracil or imiquimod lasts for several weeks and the inflammatory reaction can be very intense. A number of authors have used photodynamic therapy as an alternative to the usual treatments. We present 3 patients with histologically confirmed actinic cheilitis treated using photodynamic therapy with methyl aminolevulinic acid as the photosensitizer and red light at 630 nm. The clinical response was good, with no recurrences after 3 to 6 months of follow-up. Our experience supports the use of photodynamic therapy as a good alternative for the treatment of actinic cheilitis.

  18. Keratosis follicularis spinulosa decalvans in a family.

    PubMed

    Bellet, Jane S; Kaplan, Andrew L; Selim, M Angelica; Olsen, Elise A

    2008-03-01

    Keratosis follicularis spinulosa decalvans (KFSD) is a rare condition characterized by diffuse keratosis pilaris with a scarring alopecia of the scalp and associated photophobia, facial erythema, and palmoplantar keratoderma. Although initially described as a sex-linked disorder, several different inheritance patterns have been observed. We describe a patient whose father and sister were also affected with this condition, consistent with an autosomal dominant genetic transmission. Multiple topical and systemic treatments have been unsuccessful in this patient, attesting to the treatment refractoriness typically seen in KFSD.

  19. Validation of a diagnostic algorithm for the discrimination of actinic keratosis from normal skin and squamous cell carcinoma by means of high-definition optical coherence tomography.

    PubMed

    Marneffe, Alice; Suppa, Mariano; Miyamoto, Makiko; Del Marmol, Véronique; Boone, Marc

    2016-09-01

    Actinic keratoses (AKs) commonly arise on sun-damaged skin. Visible lesions are often associated with subclinical lesions on surrounding skin, giving rise to field cancerization. To avoid multiple biopsies to diagnose subclinical/early invasive lesions, there is an increasing interest in non-invasive diagnostic tools, such as high-definition optical coherence tomography (HD-OCT). We previously developed a HD-OCT-based diagnostic algorithm for the discrimination of AK from squamous cell carcinoma (SCC) and normal skin. The aim of this study was to test the applicability of HD-OCT for non-invasive discrimination of AK from SCC and normal skin using this algorithm. Three-dimensional (3D) HD-OCT images of histopathologically proven AKs and SCCs and images of normal skin were collected. All images were shown in a random sequence to three independent observers with different experience in HD-OCT, blinded to the clinical and histopathological data and with different experience with HD-OCT. Observers classified each image as AK, SCC or normal skin based on the diagnostic algorithm. A total of 106 (38 AKs, 16 SCCs and 52 normal skin sites) HD-OCT images from 71 patients were included. Sensitivity and specificity for the most experienced observer were 81.6% and 92.6% for AK diagnosis and 93.8% and 98.9% for SCC diagnosis. A moderate interobserver agreement was demonstrated. HD-OCT represents a promising technology for the non-invasive diagnosis of AKs. Thanks to its high potential in discriminating SCC from AK, HD-OCT could be used as a relevant tool for second-level examination, increasing diagnostic confidence and sparing patients unnecessary excisions.

  20. Keratosis follicularis spinulosa decalvans.

    PubMed

    Reddy, B S; Thadeus, J; Garg, B R; Rathnakar, C

    1995-01-01

    The case findings in a 22-year-old male patient of keratosis follicularis spinulosa decalvans are described. In addition to the characteristic cutaneous, occular and histological features, he had striking angular stomatitis and fissuring of the tongue simulating vitamin B-complex deficiency. This is an unreported feature to our knowledge. The mode of inheritance suggested X-linked trait.

  1. [Keratosis follicularis spinulosa decalvans].

    PubMed

    Helbig, D; Grabbe, S; Jansen, T

    2008-01-01

    Keratosis follicularis spinulosa decalvans is a rare, X-linked disorder of keratinization of the hair follicle with inflammation and atrophy associated with corneal dystrophy and other symptoms. A family with several affected members is reported. The unaffected parents were related. A 12-year-old girl and her 5-year-old brother had follicular spiny hyperkeratoses on the trunk and extremities. The girl had thinning of the eyelashes and eyebrows as well as scarring alopecia of the scalp as additional features of the disease. Both the girl and her brother had corneal dystrophy and photophobia. Two sisters aged 8 and 10 years did not show similar skin or eye findings.

  2. [Procedure for daylight methyl aminolevulinate photodynamic therapy to treat actinic keratoses].

    PubMed

    Girard, C; Adamski, H; Basset-Séguin, N; Beaulieu, P; Dreno, B; Riboulet, J-L; Lacour, J-P

    2016-04-01

    Actinic keratosis (AK), also known as solar keratosis or pre-cancerous keratosis, is frequently observed in areas of skin exposed to sunlight, particularly in light-skinned patients. In France, photodynamic therapy using red light (conventional PDT) and methylamino 5-levulinate (MAL) is indicated in the treatment of thin or non-hyperkeratotic and non-pigmented multiple AK lesions or large zones covered with AK lesions. It is well-known for its efficacy but also for its side effects, especially pain during illumination, which can limit its use. An alternative to PDT using natural daylight has recently been proposed to treat actinic keratosis lesions, and results in greater flexibility as well as significant reduction in pain. The lesions are prepared as for conventional PDT, with MAL cream being applied by the physician or the patient, after which they are exposed to natural daylight for 2hours. The lesions are then gently cleansed and protected from natural light for 24hours. This paper seeks to provide a precise description of the daylight PDT procedure for the treatment of AK.

  3. Combination of 595-nm pulsed dye laser, long-pulsed 755-nm alexandrite laser, and microdermabrasion treatment for keratosis pilaris: retrospective analysis of 26 Korean patients.

    PubMed

    Lee, Sang Ju; Choi, Min Ju; Zheng, Zhenlong; Chung, Won Soon; Kim, Young Koo; Cho, Sung Bin

    2013-06-01

    Keratosis pilaris (KP) has beenpresented as small keratotic follicular papules with or without surrounding erythema. Various treatments with laser or light therapy have been used for the management of KP with various clinical outcomes. In the present study, we investigated the efficacy and safety of a combination therapy for KP. A total of 29 anatomical sites with KP in 26 patients were treated using a 595-nm pulsed dye laser (PDL) with nonpurpuragenic fluences, a long-pulsed 755-nm alexandrite laser, and microdermabrasion. Clinical improvement was assessed by comparing preand posttreatment clinical photographs and patient satisfaction rates. Evaluation of the clinical results three months after the treatments showed that 12 of the 29 anatomical sites (41.4%) demonstrated Grade 3 clinical improvement, ten (34.5%) had Grade 2 clinical improvement, four (13.8%) showed Grade 1 improvement, and three (10.3%) showed Grade 4 improvement. We observed that KP lesions improved not only in erythema and skin texture, but also in brownish dyschromias. Potential adverse events were not observed, except prolonged posttherapy scaling. Our observations demonstrate that combination therapy using a 595-nm PDL, a long-pulsed 755-nm alexandrite laser, and microdermabrasion can have a positive therapeutic effect on KP.

  4. Keratosis follicularis spinulosa decalvans: case report.

    PubMed

    Berbert, Alceu L C V; Mantese, Sônia A O; Rocha, Ademir; Cherin, Cláudia P; Couto, Carolina M

    2010-01-01

    Keratosis follicularis spinulosa decalvans is a rare disease, with genetic transmission either X-linked or sporadic, characterized by follicular hyperkeratosis and cicatricial alopecia. The disease usually begins in early childhood exacerbating throughout adolescence. The therapies are somewhat effective, with frustrating treatment when there are changes which are predominantly cicatricial. It is reported a case of child with intense cicatricial alopecia, with precocious changes (already present at birth) that rapidly evolved to diffuse cicatricial alopecia on the scalp, which has limited the treatment, with disappointing results.

  5. Keratosis follicularis spinulosa decalvans and acne keloidalis nuchae.

    PubMed

    Goh, Michelle S Y; Magee, Jill; Chong, Alvin H

    2005-11-01

    A 27-year-old man presented with a 10-year history of scarring alopecia on the vertex of the scalp associated with follicular crusting and pustule formation, and a papular eruption on the posterior neck. Additionally, there was keratosis pilaris on the cheeks, eyebrows and thighs. Histology from the vertex showed scarring with a mixed perifollicular inflammatory infiltrate and foci of acute suppurative folliculitis. With clinical correlation, the diagnosis of keratosis follicularis spinulosa decalvans and concurrent acne keloidalis nuchae was made. The association of keratosis follicularis spinulosa decalvans with acne keloidalis nuchae has not previously been described. The patient responded to treatment with oral isotretinoin 20 mg (0.25 mg/kg) daily for 12 months.

  6. Large surface photodynamic therapy with aminolevulinic acid: treatment of actinic keratoses and beyond.

    PubMed

    Bissonette, Robert; Bergeron, Annie; Liu, Younan

    2004-01-01

    Photodynamic therapy (PDT) with topical aminolevulinic acid (ALA) is currently approved in the US and Canada for the spot treatment of non-hypertrophic actinic keratoses of the face and scalp. Dermatologists are currently using ALA-PDT on larger skin surfaces for the treatment of extensive actinic keratoses, sun damage P and acne. This article reviews the safety and efficacy of large surface ALA-PDT for the treatment of actinic keratoses and photodamage. New data on the carcinogenic potential of weekly topical ALA-PDT in mice is also presented. Groups of hairless mice were treated weekly with either ALA alone, blue light alone or ALA-PDT using blue light for a total of 10 months followed by an additional 2 months or observation. Mice were examined weekly for the presence of skin tumors. Skin tumors were not observed in mice treated weekly with blue light alone, with topical application of ALA alone or with ALA-PDT.

  7. Daylight-mediated photodynamic therapy for actinic damage in Latin America: consensus recommendations.

    PubMed

    Grinblat, Beni; Galimberti, Gaston; Chouela, Edgardo; Sanclemente, Gloria; Lopez, Miguel; Alcala, Daniel; Torezan, Luís; Pantoja, Gonzalo

    2016-03-01

    Although conventional photodynamic therapy (c-PDT) using methyl aminolevulinate cream (MAL) is effective for the treatment of grade I-II facial and scalp actinic keratosis (AK), it is associated with treatment-related pain for some patients. Daylight-mediated PDT (DL-PDT) has shown similar efficacy to c-PDT, was nearly painless, and was well tolerated. Overall, DL-PDT effectively treats AK and offers a simpler and better tolerated treatment option than c-PDT. This consensus panel provided recommendations on the use of DL-PDT in Latin America (LATAM) for the treatment of actinic damage associated with few or multiple AKs. The panel was comprised of eight dermatologists from different LATAM countries who have experience using PDT for the treatment of actinic damage. The panel reviewed the relevant literature and provided personal expertise with regard to using DL-PDT for the treatment of photodamage with or without AK. The recommendations formulated by the expert panel provide evidence-based guidelines on all aspects of DL-PDT for the treatment of actinic damage associated with AK in different regions of LATAM. These recommendations provide guidance for dermatologists to ensure maintenance of efficacy and safety of DL-PDT when treating actinic damage, associated with few or multiple AKs in sun-exposed skin.

  8. Two brothers with keratosis follicularis spinulosa decalvans.

    PubMed

    Alfadley, Abdullah; Al Hawsawi, Khalid; Hainau, Bo; Al Aboud, Khalid

    2002-11-01

    Keratosis follicularis spinulosa decalvans is a rare, X-linked disorder affecting both the skin and eyes. There are few reports about this entity. The aim of this report is to describe 2 brothers with progressive scarring alopecia of the scalp, hypotrichosis with follicular prominence of the eyelashes, and extensive keratosis pilaris. The second patient has Down syndrome with palmoplantar keratoderma and partial alopecia of the eyebrows. We also reviewed the literature about this uncommon entity.

  9. Keratosis follicularis spinulosa decalvans in a female.

    PubMed

    Sequeira, Fiona F; Jayaseelan, Elizabeth

    2011-01-01

    Keratosis follicularis spinulosa decalvans (KFSD), is a rare follicular syndrome associated with widespread keratosis pilaris and progressive scarring alopecia. This genodermatoses often starts at infancy or early childhood with an X-linked mode of inheritance. Males are predominantly affected and females frequently show no disease or only a mild form. We describe this not so common entity of KFSD in a nine year old female child.

  10. Nilontinib induced keratosis pilaris atrophicans.

    PubMed

    Khetarpal, Shilpi; Sood, Apra; Billings, Steven D

    2016-08-15

    Keratosis pilaris (KP) is a disorder of follicular keratinization that is characterized by keratin plugs in the hair follicles with surrounding erythema. A 46-year-old man with chronic myelogenous leukemia (CML) was started on nilotinib, a second generation tyrosine kinase inhibitor (TKI). Two months later the patient noticed red bumps on the skin and patchy hair loss on the arms, chest, shoulders, back, and legs. Cutaneous reactions to nilotinib are the most frequent non-hematologic adverse effects reported. However, it is important to distinguish KP-like eruptions from more severe drug hypersensitivity eruptions, which can necessitate discontinuing the medication. Also, it is important to classify the cutaneous eruptions in patients on TKI according to the morphology instead of labeling them all as "chemotherapy eruption" to be able to better manage these adverse effects.

  11. Laser abrasion for cosmetic and medical treatment of facial actinic damage

    SciTech Connect

    David, L.M.; Lask, G.P.; Glassberg, E.; Jacoby, R.; Abergel, R.P.

    1989-06-01

    Previous studies have shown the carbon dioxide (CO/sub 2/) laser to be effective in the treatment of actinic cheilitis. After CO/sub 2/ laser abrasion, normal skin and marked cosmetic improvement of the lip were noted. In our study, twenty-three patients were treated with CO/sub 2/ laser abrasions for cosmetic improvement of facial lines and actinic changes. Pre- and postoperative histopathologic examinations were made on two patients. Preoperative examination of specimens from actinically damaged skin showed atypical keratinocytes in the basal layer of the epidermis, with overlying dense compact orthokeratosis and parakeratosis. Abundant solar elastosis was seen in the papillary dermis. Postoperative histologic specimens showed a normal-appearing epidermis with fibrosis in the papillary dermis and minimal solar elastosis (about four weeks after laser treatment). At present, various modalities are available for the regeneration of the aged skin, including chemical peels and dermabrasion. Significantly fewer complications were noted with CO/sub 2/ laser abrasion than with these methods. Thus, CO/sub 2/ laser abrasion can be useful in the cosmetic and medical treatment of the aged skin. Marked clinical and histologic improvement has been demonstrated.

  12. Keratosis pilaris atrophicans in mother and daughter.

    PubMed

    Khumalo, N P; Loo, W J; Hollowood, K; Salvary, I; Graham, R M; Dawber, R P R

    2002-07-01

    We report two cases of keratosis follicularis spinulosa decalvans in a Caucasian family involving a 28-year-old woman and her mother. This is an unusual family in that no male relatives are similarly affected. Secondly, both patients have no significant eye changes but quite extensive scarring alopecia. To the best of our knowledge this is the second reported family in the UK.

  13. Treatment of actinic cheilitis by photodynamic therapy with 5-aminolevulinic acid and blue light activation.

    PubMed

    Zaiac, Martin; Clement, Annabelle

    2011-11-01

    Actinic cheilitis (AC), a common disorder of the lower lip, should be treated early to prevent progression to invasive squamous cell carcinoma. This study evaluated the safety and efficacy of photodynamic therapy (PDT) with 5-aminolevulinic acid (ALA) activated by blue light for the treatment of AC. Fifteen patients with clinically evident or biopsy-proven AC received two treatments with ALA PDT with blue light activation. Treatments were spaced three to five weeks apart. Most patients achieved 65% to 75% clearance three to five weeks after the first treatment and all achieved more than 75% clearance one month after the second treatment. Three patients achieved complete clearance. Pain and burning during irradiation were absent or mild. All patients said they would repeat the procedure. ALA PDT with 417 nm blue light is a promising option for the treatment of AC of the lower lip.

  14. Automated Detection of Actinic Keratoses in Clinical Photographs

    PubMed Central

    Hames, Samuel C.; Sinnya, Sudipta; Tan, Jean-Marie; Morze, Conrad; Sahebian, Azadeh; Soyer, H. Peter; Prow, Tarl W.

    2015-01-01

    Background Clinical diagnosis of actinic keratosis is known to have intra- and inter-observer variability, and there is currently no non-invasive and objective measure to diagnose these lesions. Objective The aim of this pilot study was to determine if automatically detecting and circumscribing actinic keratoses in clinical photographs is feasible. Methods Photographs of the face and dorsal forearms were acquired in 20 volunteers from two groups: the first with at least on actinic keratosis present on the face and each arm, the second with no actinic keratoses. The photographs were automatically analysed using colour space transforms and morphological features to detect erythema. The automated output was compared with a senior consultant dermatologist’s assessment of the photographs, including the intra-observer variability. Performance was assessed by the correlation between total lesions detected by automated method and dermatologist, and whether the individual lesions detected were in the same location as the dermatologist identified lesions. Additionally, the ability to limit false positives was assessed by automatic assessment of the photographs from the no actinic keratosis group in comparison to the high actinic keratosis group. Results The correlation between the automatic and dermatologist counts was 0.62 on the face and 0.51 on the arms, compared to the dermatologist’s intra-observer variation of 0.83 and 0.93 for the same. Sensitivity of automatic detection was 39.5% on the face, 53.1% on the arms. Positive predictive values were 13.9% on the face and 39.8% on the arms. Significantly more lesions (p<0.0001) were detected in the high actinic keratosis group compared to the no actinic keratosis group. Conclusions The proposed method was inferior to assessment by the dermatologist in terms of sensitivity and positive predictive value. However, this pilot study used only a single simple feature and was still able to achieve sensitivity of detection of 53

  15. A randomized, double-blind, placebo-controlled clinical trial evaluating Dermytol® cream for the treatment of actinic keratoses

    PubMed Central

    Evans, Malkanthi; Kalman, Douglas; Alvarez, Patricia; Paquet, Maryse; Guthrie, Najla

    2014-01-01

    Purpose Actinic keratosis lesions (AKs) have the potential to develop into squamous cell carcinoma (SCC) and thus therapies to prevent SCC development from AKs are warranted. The aim of this study was to assess the effects of a 3 month application of a canola phenolic acid-based cream (CPA) on AK lesions. Patients and methods This was a randomized, double-blind, placebo-controlled, 12 week clinical study conducted at a single-center in Santo Domingo, Dominican Republic. Forty-five subjects (30 CPA and 15 placebo), aged 45–85 years with 3–10 AKs within a 20 cm2 treatment area (scalp, forehead, dorsal forearm, neck, or back of hand) were enrolled. The primary outcome was complete or partial lesion clearance and the secondary outcome was safety of CPA. Results Although complete AK lesion clearance was not seen in this study, a significant reduction in the mean change from baseline in the average lesion area was observed at weeks 3 (P=0.002), 6 (P<0.001), and 12 (P<0.001) in the CPA group, but only at weeks 6 and 12 in the placebo group (P=0.005 and P=0.002, respectively). Furthermore, the proportion of participants with a $10% decrease in average lesion area was significantly higher in the CPA group than the placebo group at weeks 3 (P=0.05) and 6 (P=0.02), and showed a trend at week 12 (P=0.06). A subset analysis of the change in average lesion area based upon the total lesion area at baseline revealed that CPA elicited a greater reduction than placebo (2×) in participants with a baseline total AK lesion area of 100–500 mm2 than in participants with a total area <100 mm2 (1.3×). Conclusion The results of this study and previous in vitro studies suggest a potential role for CPA in the treatment of AK lesions and the prevention of SCC development. PMID:25143750

  16. Novel approaches in anti-angiogenic treatment targeting endothelial F-actin: a new anti-angiogenic strategy?

    PubMed

    Thoenes, Lilja; Günther, Michael

    2008-12-01

    As a functional blood supply is crucial for growth of solid tumors, the development of anticancer agents to inhibit the formation of new tumor blood vessels is an area of extensive research. Endothelial cell motility driven by the dynamics of the cytoskeleton is a key feature of angiogenesis. Agents that preferentially target endothelial tubulin are well established, and inhibition of the endothelial actin dynamics appears to be another promising anti-angiogenic strategy. Remodeling of the actin cytoskeleton is regulated by several pathways involving a large number of signaling proteins. Therefore, therapeutic strategies for the modulation of actin dynamics include agents that target the actin cytoskeleton directly, as well as inhibitors of actin binding proteins and regulators in upstream pathways. This review provides an overview of the regulation of the actin cytoskeleton and proteins that could potentially be targeted by therapeutic agents. In addition, an outline of promising agents, which includes recombinant proteins, endogenous effectors and treatment regimes that exert anti-angiogenic effects partly mediated by affecting endothelial actin dynamics is provided.

  17. Successful use of a topical mixture with ozolipoile in the treatment of actinic ulcers

    PubMed Central

    Inchingolo, Francesco; Tarullo, Angelo; Cagiano, Raffaele; Resta, Gianpiero; Dipalma, Gianna; Inchingolo, Angelo Michele; Tarullo, Antonella; Scacco, Salvatore; Marrelli, Massimo; Corti, Luigi; Tatullo, Marco

    2015-01-01

    Purpose Post-radiation skin damage is the result of alterations produced in the irradiated zone. There are different studies aimed at verifying the effectiveness of several kinds of molecules in the treatment of radiation-induced skin damage. The purpose of this study is to test a mixture with a formulation containing several natural active ingredients on actinic ulcers in patients receiving radiation therapies. Patients and methods The authors recruited 13 patients, and randomly divided them into a test group (T1) and a control group (T2). The patients in both groups were undergoing radiotherapy. The T1 group was treated with a mixture called ozolipoile, whereas the T2 group was administered hyaluronic acid gel followed by non-ablative laser therapy. We evaluated the obtained results, the time of clinical healing, the reduction of pain, and each side effect, comparing all data between the T1 and T2 groups. Results The average Visual Analog Scale results showed decrease in pain in both groups; however, while the T1 group showed a significant decrease in the values, the T2 group reported a more gradual reduction in the values, without ever reaching the minimum values obtained with the treatment with ozolipoile. Conclusion Treatment of actinic ulcers with ozolipoile mixture leads to faster control of pain and to better healing of small-size ulcers. PMID:25848312

  18. [Environmental and occupational risk factors in keratosis of the larynx].

    PubMed

    de Vincentiis, M; Gallo, A; Boccia, M M; Diletti, G; Simonelli, M; Della Rocca, C

    1993-01-01

    Laryngeal keratosis may frequently precede the appearance of carcinoma of the larynx which might well indicate that these diseases have a common denominator. A retrospective study of 120 subjects with laryngeal keratosis was examined. The intention of the Authors was to verify whether the principle risk factors involved in the appearance of laryngeal carcinoma were the same as those implicated in laryngeal keratosis formation. Sex age, work activity, cigarette smoke, alcohol consumption and vocal chord abuse were considered. Laryngeal keratosis takes keratosis with dysplasia as well as keratosis without. A link between these two types of keratosis and cancer was sought. In particular, the possibility that a persistent action of the mentioned risk factors could cause laryngeal dysplasia-free keratosis to change into dysplastic lesions and subsequently into cancer was investigated. A case-control study was performed in order to analyze the importance of work activity. Results were statistically significant (P < 0.001). The Cramer V2 calculation demonstrated a clear correlation between the number of cigarettes smoked and the appearance of dysplasia (V2 = 0.117; P < 0.005). Results showed a clearly different behaviour between sexes. The number of males was much higher than females as was the age at which keratosis appeared greater in males. The fact that the average age in which keratosis appeared preceded the appearance of laryngeal cancer by ten years indicates that this interrum is sufficient for keratosis with dysplasia to be transformed into cancer (due to the continued action of the mentioned etiologic factors, mainly referred to cigarette smoke). In our data analysis, no correlation was demonstrated between keratosis without dysplasia and cancer.

  19. Daylight photodynamic therapy with methyl-aminolevulinate for the treatment of actinic cheilitis.

    PubMed

    Fai, Dario; Romanello, Eugenio; Brumana, Marta Benedetta; Fai, Carlotta; Vena, Gino Antonio; Cassano, Nicoletta; Piaserico, Stefano

    2015-01-01

    Actinic cheilitis (AC) is a common premalignant condition that requires an effective treatment to reduce the risk of malignant transformation. Photodynamic therapy (PDT) has been recently added to the armamentarium available for AC treatment. Daylight PDT (D-PDT) is a novel PDT modality in which the activation of the topical photosensitizer is induced by the exposure to natural daylight instead of artificial light sources without preliminary occlusion. This simplified procedure was found to be more tolerated as compared to conventional PDT. We report our preliminary experience on the use of D-PDT using methyl-aminolevulinate cream in 10 patients with refractory AC of the lower lip. Patients received two consecutive D-PDT sessions with an interval of 7-14 days. At 3 months after therapy, a complete response was observed in seven patients, with sustained results in five patients over an observational period of 6-12 months. Treatment was well tolerated.

  20. Keratosis follicularis spinulosa decalvans: report of a new pedigree.

    PubMed

    Herd, R M; Benton, E C

    1996-01-01

    Keratosis follicularis spinulosa decalvans is a rare, X-linked genodermatosis characterized by follicular hyperkeratosis, scarring alopecia of the scalp, eyebrows and eyelashes, corneal dystrophy and photophobia. We describe two cases from a large family, the first with keratosis follicularis spinulosa decalvans to be reported in the U.K.

  1. Psychomotor retardation - an unusual association of keratosis follicularis spinulosa decalvans.

    PubMed

    Masood, Q; Manzoor, S; Hassan, I; Majid, I

    2000-01-01

    Keratosis follicularis spinulosa decalvans is one of a group of related disorders that shows keratosis pilaris with inflammation followed by atrophy. Here we report a case of this relatively rare disorder in a 6-year old boy who had associated psychomotor retardation.

  2. [A case of keratosis follicularis spinulosa decalvans (author's transl)].

    PubMed

    Salamon, T; Gvozdenović, B

    1975-01-01

    The case of a 2-year-old boy with keratosis follicularis spinulosa decalvans is described. On of his sisters had keratosis follicularis of the upper arms, forearms, thighs and legs as well as blepharonconjunctivitis chronica catarrhalis bilateralis and was considered as forme fruste of the anomaly. His mother had sparse eyebrows. The mode of inheritance and the Lyon hypothesis are discussed.

  3. Diclofenac in hyaluronic acid gel: an alternative treatment for actinic cheilitis

    PubMed Central

    LIMA, Giana da Silveira; da SILVA, Gabriela Ferrari; GOMES, Ana Paula Neutzling; de ARAÚJO, Lenita Maria Aver; SALUM, Fernanda Gonçalves

    2010-01-01

    Objective Actinic cheilitis (AC) is a precancerous lesion of the lip vermillion caused by prolonged exposure to ultraviolet light. The aim of this study was to evaluate the effect of 3% diclofenac in 2.5% hyaluronic acid gel in the treatment of AC. Methods Thirty-four patients with chronic AC were treated twice a day with topical diclofenac during a period of 30 to 180 days. The individuals were followed up every 15 days by means of clinical examination and digital photographic documentation. Results Of the 27 patients that completed the study, 12 (44%) showed complete remission of the whitish plaques and exfoliative areas, and 15 (56%) had partial remission of the clinical picture of cheilitis. The latter group was submitted to excision of the leukoplakic areas which diagnosis varied from mild to moderate epithelial dysplasia. Conclusion The results suggest a promising role for diclofenac in hyaluronic acid gel in the treatment of AC. This treatment has the advantages of not being invasive and showing few side effects. PMID:21085813

  4. Light and laser treatment modalities for disseminated superficial actinic porokeratosis: a systematic review.

    PubMed

    Aird, Gregory A; Sitenga, Jenna L; Nguyen, Austin Huy; Vaudreuil, Adam; Huerter, Christopher J

    2017-02-27

    Treatment of disseminated superficial actinic porokeratosis (DSAP) is poorly standardized. The present review seeks to comprehensively discuss the potential for laser and light modalities in the treatment of DSAP. A systematic review of light and laser treatment modalities was conducted to include 26 cases of patients with DSAP. Systematic review resulted in 14 articles to be included. Photodynamic therapy (PDT) overall was the least successful treatment modality, with clinical improvement seen in a minority of patients (MAL-PDT: N = 9 patients, 33.3% showed improvement; ALA-PDT: N = 3 patients, 0% improvement; hypericin-PDT: N = 2 patients, 0% improvement) after numerous post-procedural side effects of hyperpigmentation, inflammation, erythema, and discomfort. Overall, in the available reports, PDT demonstrates poor outcomes with greater incidence of side effects. The response rates of DSAP lesions treated with lasers were as follows: (Q-switched ruby lasers: N = 2, 100%; CO2 laser: N = 1, 100%; PDT and CO2 combination therapy: N = 2, 0-50%; erbium and neodymium YAG lasers: N = 2, 100%; fractional 1927-nm thulium fiber lasers: N = 2, 100%; Grenz rays: N = 1, 100%; and fractional photothermolysis: N = 2, 100%). The side effects of laser therapy were minimal and included mild erythema, slight hyperpigmentation, and moderate edema. Laser therapy is a promising treatment option for DSAP with an excellent side effect profile. However, higher power studies are required to determine optimal guidelines for laser treatment of DSAP.

  5. Follicular keratosis of the chin treated with 1.24R-dihydroxyvitamin D3 ointment.

    PubMed

    Yanagihara, Makoto; Takeda, Kiminobu; Tanabe, Hiroshi; Abe, Shinya; Ishizaki, Hiroshi

    2007-01-01

    In follicular keratosis of the chin, keratotic follicular papules occur on the chin and jaw due to localized prolonged pressure and friction on the naked skin. We present one patient with this disorder. The dermatoscopic examination revealed many well-demarcated yellow spindle bodies in the patchy lesion. Therapy with 1.24R-dihydroxyvitamin D3 ointment was effective during the treatment but had no residual positive effect.

  6. Paclitaxel-loaded ethosomes®: potential treatment of squamous cell carcinoma, a malignant transformation of actinic keratoses.

    PubMed

    Paolino, Donatella; Celia, Christian; Trapasso, Elena; Cilurzo, Felisa; Fresta, Massimo

    2012-05-01

    Topical application of anticancer drugs for the treatment of malignancies represents a new challenge in dermatology, potentially being an alternative therapeutic approach for the efficacious treatment of non-melanoma skin cancer, that is, actinic keratoses, and malignant lesions of the skin caused by ultraviolet radiation. Anti-proliferative and antimitotic drugs, including many of the taxanes, are currently under investigation for the treatment of cutaneous malignant transformation of actinic keratoses, particularly the squamous cell carcinoma. Paclitaxel-loaded ethosomes® are proposed as topical drug delivery systems for the treatment of this pathology due to their suitable physicochemical characteristics and enhanced skin penetration ability for deep dermal delivery. Our in vitro data show that the skin application of paclitaxel-loaded ethosomes® improved the permeation of paclitaxel in a stratum corneum-epidermis membrane model and increased its anti-proliferative activity in a squamous cell carcinoma model as compared to the free drug. The results obtained encouraged the use of the paclitaxel-loaded ethosomes® as the formulation for the potential treatment of squamous cell carcinoma, a malignant transformation of actinic keratoses.

  7. Treatment of ras-induced cancers by the F-actin-bundling drug MKT-077.

    PubMed

    Tikoo, A; Shakri, R; Connolly, L; Hirokawa, Y; Shishido, T; Bowers, B; Ye, L H; Kohama, K; Simpson, R J; Maruta, H

    2000-01-01

    A rhodacyanine dye called MKT-077 has shown a highly selective toxicity toward several distinct human malignant cell lines, including bladder carcinoma EJ, and has been subjected to clinical trials for cancer therapy. In the pancreatic carcinoma cell line CRL-1420, but not in normal African green monkey kidney cell line CV-1, it is selectively accumulated in mitochondria. However, both the specific oncogenes responsible for its selective toxicity toward cancer cells, and its target proteins in these cancer cells, still remain to be determined. This study was conducted using normal and ras-transformed NIH 3T3 fibroblasts to determine whether oncogenic ras mutants such as v-Ha-ras are responsible for the selective toxicity of MKT-077 and also to identify its targets, using its derivative called "compound 1" as a specific ligand. We have found that v-Ha-ras is responsible for the selective toxicity of MKT-077 in both in vitro and in vivo. Furthermore, we have identified and affinity purified at least two distinct proteins of 45 kD (p45) and 75 kD (p75), which bind MKT-077 in v-Ha-ras-transformed cells but not in parental normal cells. Microsequencing analysis has revealed that the p45 is a mixture of beta- and gamma-actin, whereas the p75 is HSC70, a constitutive member of the Hsp70 heat shock adenosine triphosphatase family, which inactivates the tumor suppressor p53. MKT-077 binds actin directly, bundles actin filaments by cross-linking, and blocks membrane ruffling. Like a few F-actin-bundling proteins such as HS1, alpha-actinin, and vinculin as well as F-actin cappers such as tensin and chaetoglobosin K (CK), the F-actin-bundling drug MKT-077 suppresses ras transformation by blocking membrane ruffling. These findings suggest that other selective F-actin-bundling/capping compounds are also potentially useful for the chemotherapy of ras-associated cancers.

  8. Actinic Prurigo.

    PubMed

    Rodríguez-Carreón, Alma Angélica; Rodríguez-Lobato, Erika; Rodríguez-Gutiérrez, Georgina; Cuevas-González, Juan Carlos; Mancheno-Valencia, Alexandra; Solís-Arias, Martha Patricia; Vega-Memije, María Elisa; Hojyo-Tomoka, María Teresa; Domínguez-Soto, Luciano

    2015-01-01

    Actinic prurigo is an idiopathic photodermatosis that affects the skin, as well as the labial and conjunctival mucosa in indigenous and mestizo populations of Latin America. It starts predominantly in childhood, has a chronic course, and is exacerbated with solar exposure. Little is known of its pathophysiology, including the known mechanisms of the participation of HLA-DR4 and an abnormal immunologic response with increase of T CD4+ lymphocytes. The presence of IgE, eosinophils, and mast cells suggests that it is a hypersensitivity reaction (likely type IVa or b). The diagnosis is clinical, and the presence of lymphoid follicles in the mucosal histopathologic study of mucosa is pathognomonic. The best available treatment to date is thalidomide, despite its secondary effects.

  9. Keratosis follicularis spinulosa decalvans associated with acne keloidalis nuchae and tufted hair folliculitis.

    PubMed

    Janjua, Shahbaz A; Iftikhar, Nadia; Pastar, Zrinjka; Hosler, Gregory A

    2008-01-01

    Keratosis follicularis spinulosa decalvans is a rare, X-linked disorder characterized by scarring alopecia of the scalp and eyebrows in the setting of widespread keratosis pilaris. Less frequent associations are ocular abnormalities and palmoplantar keratoderma. Acne keloidalis nuchae has previously been described in one patient with keratosis follicularis spinulosa decalvans. We report another case of keratosis follicularis spinulosa decalvans with acne keloidalis nuchae and tufted hair folliculitis, thus further establishing this association.

  10. Italian guidelines and therapeutic algorithm for actinic keratoses.

    PubMed

    Rossi, R; Calzavara-Pinton, P G; Giannetti, A; Peserico, A; Santucci, M; Vena, G A; Lotti, T

    2009-12-01

    The prevalence of actinic keratosis (AK) continues to rise among white people throughout the world and it is necessary to increase the level of attention paid to it from a diagnostic and a preventive point of view. Today, AK must be considered an in situ squamous cell carcinoma and as such, must be managed using one of the available approved therapeutic alternatives. However, when multiple AKs develop on severely photodamaged skin, the treatment of the lesion together with that of the field of cancerization is part of an optimal strategy that aims not only to solve alterations clinically evident but also those in the surrounding skin field cancerization, that most likely hosts genetic alterations and is the site of initial gradual replacement of normal cells with tumoral cells. This paper reports the most recent evidences from a careful review of the literature's key articles of the treatment of AKs and suggests guidelines for the clinicians. The guidelines indicated by the authors have also been based on practical evaluations and their own clinical experience. The present conclusions may be modified by new findings in the field of oncologic research.

  11. Bacterial nucleators: actin' on actin

    PubMed Central

    Bugalhão, Joana N.; Mota, Luís Jaime; Franco, Irina S.

    2015-01-01

    The actin cytoskeleton is a key target of numerous microbial pathogens, including protozoa, fungi, bacteria and viruses. In particular, bacterial pathogens produce and deliver virulence effector proteins that hijack actin dynamics to enable bacterial invasion of host cells, allow movement within the host cytosol, facilitate intercellular spread or block phagocytosis. Many of these effector proteins directly or indirectly target the major eukaryotic actin nucleator, the Arp2/3 complex, by either mimicking nucleation promoting factors or activating upstream small GTPases. In contrast, this review is focused on a recently identified class of effector proteins from Gram-negative bacteria that function as direct actin nucleators. These effector proteins mimic functional activities of formins, WH2-nucleators and Ena/VASP assembly promoting factors demonstrating that bacteria have coopted the complete set of eukaryotic actin assembly pathways. Structural and functional analyses of these nucleators have revealed several motifs and/or mechanistic activities that are shared with eukaryotic actin nucleators. However, functional effects of these proteins during infection extend beyond plain actin polymerization leading to interference with other host cell functions such as vesicle trafficking, cell cycle progression and cell death. Therefore, their use as model systems could not only help in the understanding of the mechanistic details of actin polymerization but also provide novel insights into the connection between actin dynamics and other cellular pathways. PMID:26416078

  12. Keratosis Pilaris Revisited: Is It More Than Just a Follicular Keratosis?

    PubMed Central

    Thomas, Mary; Khopkar, Uday Sharadchandra

    2012-01-01

    Background: Keratosis pilaris (KP) is characterized by keratinous plugs in the follicular orifices and varying degrees of perifollicular erythema. The most accepted theory of its pathogenesis proposes defective keratinization of the follicular epithelium resulting in a keratotic infundibular plug. We decided to test this hypothesis by doing dermoscopy of patients diagnosed clinically as keratosis pilaris. Materials and Methods: Patients with a clinical diagnosis of KP seen between September 2011 and December 2011 were included in the study. A clinical history was obtained and examination and dermoscopic evaluation were performed on the lesions of KP. Results: The age of the patients ranged from 6-38 years. Sixteen patients had history of atopy. Nine had concomitant ichthyosis vulgaris. All the 25 patients were found to have coiled hair shafts within the affected follicular infundibula. The hair shafts were extracted with the help of a sterile needle and were found to retain their coiled nature. Perifollicular erythema was seen in 11 patients; perifollicular scaling in 9. Conclusion: Based on our observations and previously documented histological data of KP, we infer that KP may not be a disorder of keratinization, but caused by the circular hair shaft which ruptures the follicular epithelium leading to inflammation and abnormal follicular keratinization. PMID:23766609

  13. Actinous enigma or enigmatic actin

    PubMed Central

    Povarova, Olga I; Uversky, Vladimir N; Kuznetsova, Irina M; Turoverov, Konstantin K

    2014-01-01

    Being the most abundant protein of the eukaryotic cell, actin continues to keep its secrets for more than 60 years. Everything about this protein, its structure, functions, and folding, is mysteriously counterintuitive, and this review represents an attempt to solve some of the riddles and conundrums commonly found in the field of actin research. In fact, actin is a promiscuous binder with a wide spectrum of biological activities. It can exist in at least three structural forms, globular, fibrillar, and inactive (G-, F-, and I-actin, respectively). G-actin represents a thermodynamically instable, quasi-stationary state, which is formed in vivo as a result of the energy-intensive, complex posttranslational folding events controlled and driven by cellular folding machinery. The G-actin structure is dependent on the ATP and Mg2+ binding (which in vitro is typically substituted by Ca2+) and protein is easily converted to the I-actin by the removal of metal ions and by action of various denaturing agents (pH, temperature, and chemical denaturants). I-actin cannot be converted back to the G-form. Foldable and “natively folded” forms of actin are always involved in interactions either with the specific protein partners, such as Hsp70 chaperone, prefoldin, and the CCT chaperonin during the actin folding in vivo or with Mg2+ and ATP as it takes place in the G-form. We emphasize that the solutions for the mysteries of actin multifunctionality, multistructurality, and trapped unfolding can be found in the quasi-stationary nature of this enigmatic protein, which clearly possesses many features attributed to both globular and intrinsically disordered proteins.

  14. [Keratosis follicularis spinulosa decalvans (Siemens' syndrome) associated with other abnormalities].

    PubMed

    Domenech, P; Ferrando, J; Corretger, M; Torras, H; Valls, X; González, A

    1985-01-01

    Keratosis follicularis spinulosa decalvans (ichthyosis follicularis or Siemens's syndrome) is considered a general form of keratosis pilaris decalvans. Localized types are keratosis pilaris atrophicans and atrophoderma vermicularis. A case of this unusual process is presented. Clinical, histological and scanning electron microscopic studies of the hair were performed. Clinically, a generalized hypotrichosis with hyperkeratotic follicular plugs is observed; especially in the scalp and the eyebrows. Other interesting clinical findings were cutis hyperelastica, gingival hypertrophy, mongoloid palpebral fissures, big pinnae and clinodactyly of the 5th finger. From the histological point of view we observed follicular plugging, dystrophic pilosebaceous follicles, absence of sebaceous glands, perifollicular fibrosis and minimal lymphomonocytic infiltrate. Scanning electronmicroscopy shows a brittle hair with cuticular abnormalities. Siemens's syndrome can be considered a specific pilosebaceous dysplasia because the absence or hypoplasia of sebaceous glands; which produces follicular hyperkeratosis and pilar atrophy with perifollicular fibrosis and alopecia.

  15. A kindred with alopecia, keratosis, pilaris, cataracts, and psoriasis.

    PubMed

    Appell, M L; Sherertz, E F

    1987-01-01

    Three members of a family with numerous ectodermal abnormalities are described. These anomalies primarily include patchy alopecia beginning in childhood, premature cataracts, widespread keratosis pilaris, and psoriasis. The alopecia and premature cataracts appear to follow an autosomal dominant inheritance pattern with incomplete penetrance and appear to be linked. Psoriasis also occurs in several members of this family and probably represents a separate but possibly related genodermatosis. This kindred has features of both keratosis follicularis spinulosa decalvans and ichthyosis follicularis, and the disorder seems to fit into the group of follicular hyperkeratosis disorders.

  16. Folliculitis spinulosa decalvans: an uncommon entity within the keratosis pilaris atrophicans spectrum.

    PubMed

    Di Lernia, Vito; Ricci, Cinzia

    2006-01-01

    Folliculitis spinulosa decalvans is an uncommon condition characterized by follicular hyperkeratosis, followed by scarring alopecia. We report a 12-year-old boy affected by keratotic papules of the scalp and keratosis pilaris of the limbs who developed erythema, pustules, and scale crusts on the scalp associated with scarring alopecia. Histologic examination showed follicular and interfollicular hyperkeratosis, follicular plugging, mild inflammation, and focal scarring. A transient remission of the inflammatory changes on the scalp was obtained after treatment with isotretinoin. The follicular spinulous hyperkeratosis persisted. A severe relapse of the scalp inflammation was observed during a 2-year follow-up.

  17. Clinical and Histopathological Investigation of Seborrheic Keratosis

    PubMed Central

    Roh, Nam Kyung; Hahn, Hyung Jin; Lee, Yang Won; Choe, Yong Beom

    2016-01-01

    Background Seborrheic keratosis (SK) is one of the most common epidermal tumors of the skin. However, only a few large-scale clinicohistopathological investigations have been conducted on SK or on the possible correlation between histopathological SK subtype and location. Objective The aim of this study was to analyze the clinical and histopathological features of a relatively large number of cases of diagnosed SK. Methods Two hundred and seventy-one pathology slides of skin tissue from patients with clinically diagnosed SK and 206 cases of biopsy-proven SK were analyzed. The biopsy-proven cases of SK were assessed for histopathological subclassification. The demographic, clinical, and histopathological data of the patients were collected for analysis of associated factors. Results The most frequent histopathological subtype was the acanthotic type, followed by mixed, hyperkeratotic, melanoacanthoma, clonal, irritated, and adenoid types; an unexpectedly high percentage (9.2%) of the melanoacanthoma variant was observed. The adenoid type was more common in sun-exposed sites than in sun-protected sites (p=0.028). Premalignant and malignant entities together represented almost one-quarter (24.2%) of the clinicopathological mismatch cases (i.e., mismatch between the clinical and histopathological diagnoses). Regarding the location of SK development, the frequency of mismatch for the sun-exposed areas was significantly higher than that for sun-protected areas (p=0.043). Conclusion The adenoid type was more common in sun-exposed sites. Biopsy sampling should be performed for lesions situated in sun-exposed areas to exclude other premalignant or malignant diseases. PMID:27081260

  18. Suspected Pulmonary Metastasis of Actinic Cutaneous Squamous Cell Carcinoma.

    PubMed

    Meter, Monet E; Nye, David J; Galvez, Christian R

    2017-01-01

    Introduction. It is rare for actinic or squamous cell carcinoma (SCC) in situ to metastasize. Case Presentation. A 67-year-old male had a significant medical history including severe psoriatic arthritis treated with UVB, methotrexate, and rapamycin. He had twenty-five different skin excisions of actinic keratosis four of which were invasive SCC. Our patient developed shortness of breath necessitating a visit to the emergency department. A CT scan of his chest revealed a mass in the right lower lung. A subsequent biopsy of the mass revealed well-differentiated SCC. He underwent thoracoscopic surgery with wedge resection of the lung lesion. Discussion. Actinic keratosis (AK) is considered precancerous and associated with UV exposure. It exists as a continuum of progression with low potential for malignancy. The majority of invasive SCCs are associated with malignant progression of AK, but only 5-10% of AKs will progress to malignant potential. Conclusion. In this case, a new finding of lung SCC in the setting of multiple invasive actinic cutaneous SCC associated with a history of extensive UV light exposure and immunosuppression supports a metastatic explanation for lung cancer.

  19. Suspected Pulmonary Metastasis of Actinic Cutaneous Squamous Cell Carcinoma

    PubMed Central

    Meter, Monet E.; Galvez, Christian R.

    2017-01-01

    Introduction. It is rare for actinic or squamous cell carcinoma (SCC) in situ to metastasize. Case Presentation. A 67-year-old male had a significant medical history including severe psoriatic arthritis treated with UVB, methotrexate, and rapamycin. He had twenty-five different skin excisions of actinic keratosis four of which were invasive SCC. Our patient developed shortness of breath necessitating a visit to the emergency department. A CT scan of his chest revealed a mass in the right lower lung. A subsequent biopsy of the mass revealed well-differentiated SCC. He underwent thoracoscopic surgery with wedge resection of the lung lesion. Discussion. Actinic keratosis (AK) is considered precancerous and associated with UV exposure. It exists as a continuum of progression with low potential for malignancy. The majority of invasive SCCs are associated with malignant progression of AK, but only 5–10% of AKs will progress to malignant potential. Conclusion. In this case, a new finding of lung SCC in the setting of multiple invasive actinic cutaneous SCC associated with a history of extensive UV light exposure and immunosuppression supports a metastatic explanation for lung cancer. PMID:28386508

  20. Cholera toxin treatment of vascular smooth muscle cells decreases smooth muscle α-actin content and abolishes the platelet-derived growth factor-BB-stimulated DNA synthesis

    PubMed Central

    Sachinidis, Agapios; Seul, Claudia; Gouni-Berthold, Ioanna; Seewald, Stefan; Ko, Yon; Vetter, Hans; Fingerle, Jürgen; Hoppe, Jürgen

    2000-01-01

    The second messenger cyclic AMP regulates diverse biological processes such as cell morphology and cell growth. We examined the role of the second messenger cyclic AMP on rat aortic vascular smooth muscle cell (VSMC) morphology and the intracellular transduction pathway mediated by platelet-derived growth factor β-receptor (PDGF-Rβ). The effect of PDGF-BB on VSMCs growth was assessed by [3H]-thymidine incorporation. Tyrosine phosphorylation of PDGF-Rβ, PLC-γ1, ERK1 and ERK2, p125FAK and paxillin as well as Sm α-actin was examined by the chemiluminescence Western blotting method. Actin mRNA level was quantitated by Northern blotting. Visualization of Sm α-actin filaments, paxillin and PDGF-Rβ was performed by immunfluorescence microscopy. Cholera toxin (CTX; 10 nM) treatment lead to a large and sustained increase in the cyclic AMP concentration after 2 h which correlated with change of VSMC morphology including complete disruption of the Sm α-actin filament array and loss of focal adhesions. Treatment of VSMCs with CTX did not influence tyrosine phosphorylation of p125FAK and paxillin but decreased the content of a Sm α-actin protein. Maximal decrease of 70% was observed after 24 h of treatment. CTX also caused a 90% decrease of the actin mRNA level. CTX treatment completely abolished PDGF-BB stimulated DNA-synthesis although PDGF-Rβ level and subcellular distribution and translocation was not altered. Furthermore CTX attenuated the PDGF-BB-induced tyrosine phosphorylation of the PDGF-Rβ, PI 3′-K, PLC-γ1 and ERK1/2 indicating an action of cyclic AMP on PDGF-β receptor. We conclude that although cyclic AMP attenuates the PDGF-Rβ mediated intracellular transduction pathway, an intact actin filament may be required for the PDGF-BB-induced DNA synthesis in VSMCs. PMID:10928958

  1. Dual pools of actin at presynaptic terminals.

    PubMed

    Bleckert, Adam; Photowala, Huzefa; Alford, Simon

    2012-06-01

    We investigated actin's function in vesicle recycling and exocytosis at lamprey synapses and show that FM1-43 puncta and phalloidin-labeled filamentous actin (F-actin) structures are colocalized, yet recycling vesicles are not contained within F-actin clusters. Additionally, phalloidin also labels a plasma membrane-associated cortical actin. Injection of fluorescent G-actin revealed activity-independent dynamic actin incorporation into presynaptic synaptic vesicle clusters but not into cortical actin. Latrunculin-A, which sequesters G-actin, dispersed vesicle-associated actin structures and prevented subsequent labeled G-actin and phalloidin accumulation at presynaptic puncta, yet cortical phalloidin labeling persisted. Dispersal of presynaptic F-actin structures by latrunculin-A did not disrupt vesicle clustering or recycling or alter the amplitude or kinetics of excitatory postsynaptic currents (EPSCs). However, it slightly enhanced release during repetitive stimulation. While dispersal of presynaptic actin puncta with latrunculin-A failed to disperse synaptic vesicles or inhibit synaptic transmission, presynaptic phalloidin injection blocked exocytosis and reduced endocytosis measured by action potential-evoked FM1-43 staining. Furthermore, phalloidin stabilization of only cortical actin following pretreatment with latrunculin-A was sufficient to inhibit synaptic transmission. Conversely, treatment of axons with jasplakinolide, which induces F-actin accumulation but disrupts F-actin structures in vivo, resulted in increased synaptic transmission accompanied by a loss of phalloidin labeling of cortical actin but no loss of actin labeling within vesicle clusters. Marked synaptic deficits seen with phalloidin stabilization of cortical F-actin, in contrast to the minimal effects of disruption of a synaptic vesicle-associated F-actin, led us to conclude that two structurally and functionally distinct pools of actin exist at presynaptic sites.

  2. Keratosis Follicularis Spinulosa Decalvans: A Report of Three Cases.

    PubMed

    Malvankar, Dipali D; Sacchidanand, S

    2015-01-01

    Keratosis follicularis spinulosa decalvans is a disorder affecting the hair follicles characterized by scarring alopecia of the scalp, eyebrows, and axillae, sometimes associated with photophobia and keratoderma. Being X-linked, it is more commonly seen in males but can be rarely seen in females also. We report three cases of this rare disorder including one in a female.

  3. Keratosis Follicularis Spinulosa Decalvans: A Report of Three Cases

    PubMed Central

    Malvankar, Dipali D; Sacchidanand, S

    2015-01-01

    Keratosis follicularis spinulosa decalvans is a disorder affecting the hair follicles characterized by scarring alopecia of the scalp, eyebrows, and axillae, sometimes associated with photophobia and keratoderma. Being X-linked, it is more commonly seen in males but can be rarely seen in females also. We report three cases of this rare disorder including one in a female. PMID:26622157

  4. Plasma Gelsolin Levels Decrease in Diabetic State and Increase upon Treatment with F-Actin Depolymerizing Versions of Gelsolin

    PubMed Central

    Khatri, Neeraj; Sagar, Amin; Peddada, Nagesh; Choudhary, Vikas; Chopra, Bhupinder Singh; Garg, Veena; Ashish

    2014-01-01

    The study aims to map plasma gelsolin (pGSN) levels in diabetic humans and mice models of type II diabetes and to evaluate the efficacy of gelsolin therapy in improvement of diabetes in mice. We report that pGSN values decrease by a factor of 0.45 to 0.5 in the blood of type II diabetic humans and mice models. Oral glucose tolerance test in mice models showed that subcutaneous administration of recombinant pGSN and its F-actin depolymerizing competent versions brought down blood sugar levels comparable to Sitagliptin, a drug used to manage hyperglycemic condition. Further, daily dose of pGSN or its truncated versions to diabetic mice for a week kept sugar levels close to normal values. Also, diabetic mice treated with Sitagliptin for 7 days, showed increase in their pGSN values with the decrease in blood glucose as compared to their levels at the start of treatment. Gelsolin helped in improving glycemic control in diabetic mice. We propose that gelsolin level monitoring and replacement of F-actin severing capable gelsolin(s) should be considered in diabetic care. PMID:25478578

  5. Distribution of GAP-43, beta-III tubulin and F-actin in developing and regenerating axons and their growth cones in vitro, following neurotrophin treatment.

    PubMed

    Avwenagha, Ovokeloye; Campbell, Gregor; Bird, Margaret M

    2003-11-01

    Brain derived neurotrophic factor (BDNF) when added to explant cultures of both embryonic and adult retinal ganglion cell (RGC) axons exerted a marked effect on their growth cone size and complexity and also on the intensity of GAP-43, beta-III tubulin and F-actin immunoreaction product in their axons. GAP-43 was distributed in axons, lamellipodia, and filopodia whereas beta-III tubulin was distributed along the length of developing and adult regenerating axons and also in the C-domain of their growth cones. BDNF-treated developing RGC growth cones were larger and displayed increased numbers of GAP-43 and microtubule-containing branches. Although filopodia and lamellipodia were lost from both developing and adult RGC growth cones following trkB-IgG treatment, the intensity of the immunoreaction product of all these molecules was reduced and trkB-IgGs had no effect on the axonal distribution of betas-III tubulin and GAP-43. BDNF-treated growth cones also displayed increased numbers of F-actin containing filopodia and axonal protrusions. This study demonstrates, for the first time, that trkB-IgG treatment causes the loss of F-actin in the P-domain of growth cone tips in developing and regenerating RGC axons. Although microtubules and F-actin domains normally remained distinct in cultured growth cones, beta-III tubulin and F-actin overlapped within the growth cone C-domain, and within axonal protrusions of adult RGC axons, under higher concentrations of BDNF. The collapse of RGC growth cones appeared to correlate with the loss of F-actin. In vitro, trkB signalling may therefore be involved in the maintenance and stabilisation of RGC axons, by influencing F-actin polymerisation, stabilisation and distribution.

  6. Actinic reticuloid

    SciTech Connect

    Marx, J.L.; Vale, M.; Dermer, P.; Ragaz, A.; Michaelides, P.; Gladstein, A.H.

    1982-09-01

    A 58-year-old man has his condition diagnosed as actinic reticuloid on the basis of clinical and histologic findings and phototesting data. He had clinical features resembling mycosis fungoides in light-exposed areas. Histologic findings disclosed a bandlike infiltrate with atypical mononuclear cells in the dermis and scattered atypical cells in the epidermis. Electron microscopy disclosed mononuclear cells with bizarre, convoluted nuclei, resembling cerebriform cells of Lutzner. Phototesting disclosed a diminished minimal erythemal threshold to UV-B and UV-A. Microscopic changes resembling actinic reticuloid were reproduced in this patient 24 and 72 hours after exposure to 15 minimal erythemal doses of UV-B.

  7. Topical Colchicine Gel versus Diclofenac Sodium Gel for the Treatment of Actinic Keratoses: A Randomized, Double-Blind Study

    PubMed Central

    Faghihi, Gita; Iraji, Fariba; Behfar, Shadi; Abtahi-Naeini, Bahareh

    2016-01-01

    Introduction. Actinic keratoses (AKs), a premalignant skin lesion, are a common lesion in fair skin. Although destructive treatment remains the gold standard for AKs, medical therapies may be preferable due to the comfort and reliability .This study aims to compare the effects of topical 1% colchicine gel and 3% diclofenac sodium gel in AKs. Materials and Methods. In this randomized double-blind study, 70 lesions were selected. Patients were randomized before receiving either 1% colchicine gel or 3% diclofenac sodium cream twice a day for 6 weeks. Patients were evaluated in terms of their lesion size, treatment complications, and recurrence at 7, 30, 60, and 120 days after treatment. Results. The mean of changes in the size was significant in both groups both before and after treatment (<0.001). The mean lesion size before treatment and at 30, 60, and 120 days was not different between the two groups (p > 0.05). No case of erythema was seen in the colchicine group, while erythema was seen in 22.9% (eight cases) of patients in the diclofenac sodium group (p = 0.005). Conclusions. 1% colchicine gel was a safe and effective medication with fewer side effects and lack of recurrence of the lesion. PMID:27689135

  8. Nucleus-associated actin in Amoeba proteus.

    PubMed

    Berdieva, Mariia; Bogolyubov, Dmitry; Podlipaeva, Yuliya; Goodkov, Andrew

    2016-10-01

    The presence, spatial distribution and forms of intranuclear and nucleus-associated cytoplasmic actin were studied in Amoeba proteus with immunocytochemical approaches. Labeling with different anti-actin antibodies and staining with TRITC-phalloidin and fluorescent deoxyribonuclease I were used. We showed that actin is abundant within the nucleus as well as in the cytoplasm of A. proteus cells. According to DNase I experiments, the predominant form of intranuclear actin is G-actin which is associated with chromatin strands. Besides, unpolymerized actin was shown to participate in organization of a prominent actin layer adjacent to the outer surface of nuclear envelope. No significant amount of F-actin was found in the nucleus. At the same time, the amoeba nucleus is enclosed in a basket-like structure formed by circumnuclear actin filaments and bundles connected with global cytoplasmic actin cytoskeleton. A supposed architectural function of actin filaments was studied by treatment with actin-depolymerizing agent latrunculin A. It disassembled the circumnuclear actin system, but did not affect the intranuclear chromatin structure. The results obtained for amoeba cells support the modern concept that actin is involved in fundamental nuclear processes that have evolved in the cells of multicellular organisms.

  9. Nagashima-type palmoplantar keratosis: a common Asian type caused by SERPINB7 protease inhibitor deficiency.

    PubMed

    Kubo, Akiharu

    2014-08-01

    Nagashima-type palmoplantar keratosis (NPPK) is an autosomal recessive diffuse non-epidermolytic palmoplantar keratosis caused by mutations in SERPINB7, a member of the serine protease inhibitor superfamily. Genetic studies suggest that NPPK is the most common palmoplantar keratosis in Japan, and probably Asia, but one that is extremely rare in Western countries. In this issue, Yin et al. report a founder effect of a SERPINB7 mutation in Chinese populations.

  10. Atrophoderma vermiculatum: a case report and review of the literature on keratosis pilaris atrophicans.

    PubMed

    Luria, Rebecca B; Conologue, Theresa

    2009-02-01

    Atrophoderma vermiculatum (AV) is a rare follicular disorder primarily affecting children with reticular or honeycomb atrophy of the cheeks and forehead. Along with keratosis pilaris atrophicans faciei (KPAF) and keratosis follicularis spinulosa decalvans (KFSD), AV falls within the broader spectrum of keratosis pilaris atrophicans (KPA). Although these 3 variants of KPA have unique presentations and associations, they can all be frustratingly difficult to treat. We describe a sporadic case of AV that presented in late adolescence, a relatively late age of onset.

  11. [Keratosis follicularis spinulosa decalvans and amino-aciduria (author's transl)].

    PubMed

    Grosshans, E; Heid, E; Stoll, C

    1978-04-01

    A new case of keratosis follicularis spinulosa decalvans (Siemens, 1925) in a 12 1/2 year old boy is related. This X-dominant inherited disturbance of follicular keratinization is associated with an amino-aciduria in the propositus and his mother, especially an increase of aspartic acid in urin and blood. The scarring infundibular plugs are constituted by nucleated keratin, which brightened up in polarized light and seems to be of internal trichilemmal origin.

  12. G-actin regulates rapid induction of actin nucleation by mDia1 to restore cellular actin polymers.

    PubMed

    Higashida, Chiharu; Suetsugu, Shiro; Tsuji, Takahiro; Monypenny, James; Narumiya, Shuh; Watanabe, Naoki

    2008-10-15

    mDia1 belongs to the formin family of proteins that share FH1 and FH2 domains. Although formins play a critical role in the formation of many actin-based cellular structures, the physiological regulation of formin-mediated actin assembly within the cell is still unknown. Here we show that cells possess an acute actin polymer restoration mechanism involving mDia1. By using single-molecule live-cell imaging, we found that several treatments including low-dose G-actin-sequestering drugs and unpolymerizable actin mutants activate mDia1 to initiate fast directional movement. The FH2 region, the core domain for actin nucleation, is sufficient to respond to latrunculin B (LatB) to increase its actin nucleation frequency. Simulation analysis revealed an unexpected paradoxical effect of LatB that leads to a several fold increase in free G-actin along with an increase in total G-actin. These results indicate that in cells, the actin nucleation frequency of mDia1 is enhanced not only by Rho, but also strongly through increased catalytic efficiency of the FH2 domain. Consistently, frequent actin nucleation by mDia1 was found around sites of vigorous actin disassembly. Another major actin nucleator, the Arp2/3 complex, was not affected by the G-actin increase induced by LatB. Taken together, we propose that transient accumulation of G-actin works as a cue to promote mDia1-catalyzed actin nucleation to execute rapid reassembly of actin filaments.

  13. Disruption of actin filaments and suppression of pancreatic cancer cell viability and migration following treatment with polyisoprenylated cysteinyl amides

    PubMed Central

    Nkembo, Augustine T; Salako, Olufisayo; Poku, Rosemary A; Amissah, Felix; Ntantie, Elizabeth; Flores-Rozas, Hernan; Lamango, Nazarius S

    2016-01-01

    Pancreatic cancer is characterized by K-Ras mutations in over 90% of the cases. The mutations make the tumors aggressive and resistant to current therapies resulting in very poor prognoses. Valiant efforts to drug mutant K-Ras and related proteins for the treatment of cancers with Ras mutations have been elusive. The need thus persists for therapies to target and suppress the hyperactive K-Ras mutant proteins to normal levels of activity. Polyisoprenylated cysteinyl amide inhibitors (PCAIs) of polyisoprenylated methylated protein methyl esterase (PMPMEase) were designed to disrupt polyisoprenylated protein metabolism and/or functions. The potential for PCAIs to serve as targeted anticancer agents for pancreatic cancer was evaluated in pancreatic ductal adenocarcinoma (PDAC) cell lines expressing mutant (MIAPaCa-2 and Panc-1) and wild type (BxPC-3) K-Ras proteins. The PCAIs inhibited MIAPaCa-2 and BxPC-3 cell viability and induced apoptosis with EC50 values as low as 1.9 µM. The PCAIs, at 0.5 µM, inhibited MIAPaCa-2 cell migration by 50%, inhibited colony formation and disrupted F-actin filament organization. The PCAIs blocked MIAPaCa-2 cell progression at the G0/G1 phase. These results reveal that the PCAIs disrupt pertinent biological processes that lead to pancreatic cancer progression and thus have the potential to act as targeted effective treatments for pancreatic cancer. PMID:27904769

  14. Daylight methyl-aminolevulinate photodynamic therapy versus ingenol mebutate for the treatment of actinic keratoses: an intraindividual comparative analysis.

    PubMed

    Genovese, Giovanni; Fai, Dario; Fai, Carlotta; Mavilia, Luciano; Mercuri, Santo R

    2016-05-01

    Daylight-photodynamic therapy (D-PDT) and ingenol mebutate (IM) are novel therapies directed to actinic keratoses (AK). The purpose of our study was to compare effectiveness, tolerability, cosmetic outcome and patient preference of D-PDT versus IM in the treatment of grade I and II AK. Twenty-seven patients with AK on the face or scalp were enrolled. Each patient received, in a 25 cm(2) target area, D-PDT on right side and IM on left side. Overall 323 AK were treated. Both target areas achieved complete response in 40.47% of the cases and average AK clearance rate was similar for D-PDT and IM (p=0.74). In D-PDT areas mean grade II AK clearance rate was lower compared with that of grade I AK (p=0.015). In IM areas grade I and II AK average clearance rates were similar (p=0.28). At week 1 and month 1, mean local skin responses (LSR) score were higher in areas treated with IM. IM areas showed more severe pain and cosmetic sequelae. D-PDT had similar effectiveness to IM, even if IM demonstrated higher grade II AK clearance rate. Tolerability profile was superior for D-PDT in terms of LSR and pain. D-PDT was more cosmetically acceptable. Patients preferred D-PDT to IM in most cases.

  15. Time-resolved fluorescence measurements of actin-phalloidin interactions

    NASA Astrophysics Data System (ADS)

    Helms, Michael K.; French, Todd E.

    2000-03-01

    Compounds that interact with the cytoskeleton affect mobility and division, making them useful for treatment of certain types of cancer. Actin binding drugs such as the phallotoxins (small, bicyclic peptides) bind to and stabilize actin polymers (F-actin) without binding to actin monomers (G-actin). It has been shown that the intensity of fluorescently labeled phallotoxins such as fluorescein- phalloidin and rhodamine-phalloidin increases upon bind F- actin. We used LJL BioSystems' new FLAReTM technology to measure excited state lifetime changes of fluorescein- phalloidin and rhodamine-phalloidin upon binding to F- actin.

  16. Clinical and genetic heterogeneity in keratosis follicularis spinulosa decalvans.

    PubMed

    Castori, Marco; Covaciu, Claudia; Paradisi, Mauro; Zambruno, Giovanna

    2009-01-01

    Keratosis follicularis spinulosa decalvans (KFSD) is an uncommon genodermatosis mainly characterized by follicular hyperkeratosis, progressive cicatricial alopecia and photophobia. Although an excess of affected males and linkage studies strongly suggest an X-linked pattern of inheritance, an apparently rarer autosomal dominant form with prominent follicular inflammation has also been postulated. We report on a three-generation family with five affected individuals and male-to-male transmission. In addition to widespread keratosis pilaris, cicatricial alopecia and eye involvement, our patients show diffuse facial erythema, recurrent folliculitis, enamel hypoplasia, and thickened nails. A literature review of the last 50 years identified 43 additional KFSD cases. X-linked inheritance is demonstrated in two pedigrees by linkage studies and suspected in five. An autosomal dominant pattern is confirmed in three families, including ours, by male-to-male transmission and considered likely in four. Marked facial erythema, extensive folliculitis, onychodystrophy and multiple caries are frequently reported in the autosomal dominant variant, while palmo-plantar keratoderma and early onset seem more typical of the X-linked form. Moreover, three sporadic male patients showing additional multisystemic abnormalities might be explained by an X-linked contiguous-gene syndrome.

  17. Treatment of actinic keratoses and photodamage with non-contact fractional 1540-nm laser quasi-ablation: an ex vivo and clinical evaluation.

    PubMed

    Lapidoth, Moshe; Adatto, Maurice; Halachmi, Shlomit

    2013-02-01

    The main use of non-ablative fractional photothermolysis today is for the improvement of wrinkles and scars. The purpose of this work was to evaluate the effect of a "classic" non-ablative fractional 1540 nm on facial photodamaged skin and actinic keratoses. Seventeen patients with facial actinic keratoses (AKs) and photodamage underwent two or three laser treatments with fractional 1540-nm erbium glass laser at fluences of 75 mJ, 15 ms pulse duration, and 10-mm spot size in non-contact mode. Two blinded assessors and participants evaluated clinical improvement of treatment areas after 3 months, using a quartile grading scale (no improvement = 0, 1-25% improvement = 1, 26-50% = 2, 51-75% = 3, and 76-100% = 4). Three months after the last treatment, the mean level of improvement was 3.4 ± 0.72 for AK and 3.3 ± 0.54 for skin appearance. Adverse events observed after each treatment were moderate erythema, mild edema, erosions (two cases), and mild desquamation. No scarring or post-inflammatory pigmentary changes were observed. The clinical results were supported by histological changes observed in Yucatan pig studies in vivo and ex vivo. The 1540-nm fractional erbium glass laser in the non-contact mode is a safe and effective treatment for facial photodamage and AKs.

  18. Fractional Carbon Dioxide Laser for Keratosis Pilaris: A Single-Blind, Randomized, Comparative Study.

    PubMed

    Vachiramon, Vasanop; Anusaksathien, Pattarin; Kanokrungsee, Silada; Chanprapaph, Kumutnart

    2016-01-01

    Objective. Keratosis pilaris (KP) is a common condition which can frequently be cosmetically disturbing. Topical treatments can be used with limited efficacy. The objective of this study is to evaluate the effectiveness and safety of fractional carbon dioxide (CO2) laser for the treatment of KP. Patients and Methods. A prospective, randomized, single-blinded, intraindividual comparative study was conducted on adult patients with KP. A single session of fractional CO2 laser was performed to one side of arm whereas the contralateral side served as control. Patients were scheduled for follow-up at 4 and 12 weeks after treatment. Clinical improvement was graded subjectively by blinded dermatologists. Patients rated treatment satisfaction at the end of the study. Results. Twenty patients completed the study. All patients stated that the laser treatment improved KP lesions. At 12-week follow-up, 30% of lesions on the laser-treated side had moderate to good improvement according to physicians' global assessment (p = 0.02). Keratotic papules and hyperpigmentation appeared to respond better than the erythematous component. Four patients with Fitzpatrick skin type V developed transient pigmentary alteration. Conclusions. Fractional CO2 laser treatment may be offered to patients with KP. Dark-skinned patients should be treated with special caution.

  19. Fractional Carbon Dioxide Laser for Keratosis Pilaris: A Single-Blind, Randomized, Comparative Study

    PubMed Central

    Vachiramon, Vasanop; Anusaksathien, Pattarin; Kanokrungsee, Silada; Chanprapaph, Kumutnart

    2016-01-01

    Objective. Keratosis pilaris (KP) is a common condition which can frequently be cosmetically disturbing. Topical treatments can be used with limited efficacy. The objective of this study is to evaluate the effectiveness and safety of fractional carbon dioxide (CO2) laser for the treatment of KP. Patients and Methods. A prospective, randomized, single-blinded, intraindividual comparative study was conducted on adult patients with KP. A single session of fractional CO2 laser was performed to one side of arm whereas the contralateral side served as control. Patients were scheduled for follow-up at 4 and 12 weeks after treatment. Clinical improvement was graded subjectively by blinded dermatologists. Patients rated treatment satisfaction at the end of the study. Results. Twenty patients completed the study. All patients stated that the laser treatment improved KP lesions. At 12-week follow-up, 30% of lesions on the laser-treated side had moderate to good improvement according to physicians' global assessment (p = 0.02). Keratotic papules and hyperpigmentation appeared to respond better than the erythematous component. Four patients with Fitzpatrick skin type V developed transient pigmentary alteration. Conclusions. Fractional CO2 laser treatment may be offered to patients with KP. Dark-skinned patients should be treated with special caution. PMID:27247936

  20. Daylight photodynamic therapy - Experience and safety in treatment of actinic keratoses of the face and scalp in low latitude and high brightness region*

    PubMed Central

    Galvão, Luiz Eduardo Garcia; Gonçalves, Heitor de Sá; Botelho, Karine Paschoal; Caldas, Juliana Chagas

    2017-01-01

    Daylight photodynamic therapy has been used in countries with high latitudes during the summer for actinic keratoses treatment with reports of similar efficacy to conventional photodynamic therapy. We evaluate its safety in 20 patients in the city of Fortaleza, a local with low latitude and high brightness. Sixteen patients did not report any discomfort due to the procedure. Daylight photodynamic therapy is an easy application method with great tolerability by the patient and has the possibility of being performed throughout the year in these regions. It can mean a promising tool in the control of skin cancer. PMID:28225978

  1. Abnormal epidermal changes after argon laser treatment

    SciTech Connect

    Neumann, R.A.; Knobler, R.M.; Aberer, E.; Klein, W.; Kocsis, F.; Ott, E. )

    1991-02-01

    A 26-year-old woman with a congenital port-wine stain on the forehead was treated three times at 2-month intervals with an argon laser. Six months after the last treatment, moderate blanching and mild scaling confined to the treated area was observed. A biopsy specimen of the treated area revealed a significant decrease in ectatic vessels. However, epidermal changes similar to those of actinic keratosis with disorganized cell layers and marked cytologic abnormalities were seen. Analysis of peripheral blood lymphocytes for a defect in DNA repair was negative. Multiple, argon laser-induced photothermal effects may be responsible for the changes observed in our case and may lead to premalignant epidermal transformation.

  2. Daylight photodynamic therapy with MAL cream for large-scale photodamaged skin based on the concept of 'actinic field damage': recommendations of an international expert group.

    PubMed

    Philipp-Dormston, W G; Sanclemente, G; Torezan, L; Tretti Clementoni, M; Le Pillouer-Prost, A; Cartier, H; Szeimies, R M; Bjerring, P

    2016-01-01

    Conventional PDT (c-PDT) is a widely used and approved non-invasive treatment for actinic keratosis (AK). Recent clinical, histological and immunohistochemical observations have shown that c-PDT with methyl aminolevulinate (MAL) may also partially reverse the signs of photodamage. However, pain and the need for special light source equipment are limiting factors for its use, especially in the treatment of large areas. More recently, daylight PDT (DL-PDT) has been shown to be similar to c-PDT in the treatment of AK, nearly painless and more convenient to perform. To establish consensus on recommendations for the use of MAL DL-PDT in patients with large-scale photodamaged skin. The expert group was comprised of eight dermatologists. Consensus was developed based on the personal experience of the experts in c-PDT and DL-PDT, and results of an extensive literature review. MAL DL-PDT for large areas of photodamaged skin was evaluated and recommendations based on broad clinical experience were provided. As supported by evidence-based data from multicentre studies conducted in Australia and Europe, the authors defined the concept of 'actinic field damage' which refers to photodamage associated with actinic epidermal dysplasia, and provide comprehensive guidelines for the optimal use of DL-PDT in the treatment of actinic field damage. The authors concluded that MAL DL-PDT has a similar efficacy to c-PDT at 3-month (lesion complete response rate of 89% vs. 93% in the Australian study and 70% vs. 74% in the European study (95% C.I. = [-6.8;-0.3] and [-9.5;2.4] respectively) and 6-month follow-ups (97% maintenance of complete lesion response) in the treatment of AKs. The authors agree that DL-PDT is not only efficacious but also nearly pain-free and easy to perform, and therefore results in high patient acceptance especially for the treatment of areas of actinic field damage.

  3. Formin DAAM1 Organizes Actin Filaments in the Cytoplasmic Nodal Actin Network

    PubMed Central

    Luo, Weiwei; Lieu, Zi Zhao; Manser, Ed; Bershadsky, Alexander D.; Sheetz, Michael P.

    2016-01-01

    A nodal cytoplasmic actin network underlies actin cytoplasm cohesion in the absence of stress fibers. We previously described such a network that forms upon Latrunculin A (LatA) treatment, in which formin DAAM1 was localized at these nodes. Knock down of DAAM1 reduced the mobility of actin nodes but the nodes remained. Here we have investigated DAAM1 containing nodes after LatA washout. DAAM1 was found to be distributed between the cytoplasm and the plasma membrane. The membrane binding likely occurs through an interaction with lipid rafts, but is not required for F-actin assembly. Interesting the forced interaction of DAAM1 with plasma membrane through a rapamycin-dependent linkage, enhanced F-actin assembly at the cell membrane (compared to the cytoplasm) after the LatA washout. However, immediately after addition of both rapamycin and LatA, the cytoplasmic actin nodes formed transiently, before DAAM1 moved to the membrane. This was consistent with the idea that DAAM1 was initially anchored to cytoplasmic actin nodes. Further, photoactivatable tracking of DAAM1 showed DAAM1 was immobilized at these actin nodes. Thus, we suggest that DAAM1 organizes actin filaments into a nodal complex, and such nodal complexes seed actin network recovery after actin depolymerization. PMID:27760153

  4. A study of the solar effect on actinic keratoses by quantification of elastic fibres using an image analysis system.

    PubMed

    Cho, C G; Jo, H Y; Choi, H C; Kim, I H; Song, H J; Oh, C H

    1999-07-01

    It is widely accepted that elastotic changes of the skin are primarily an indicator of cumulative sun exposure of the dermis and are a characteristic finding of actinic keratoses. To date, there have been few reports that measure the amount of elastic tissue objectively and quantitatively, especially in actinic keratoses. The computerized image analysis method has proved useful recently in determining the area of elastic fibres. Using this method, we objectively quantified the elastotic tissue in actinic keratoses and evaluated the relationship between the degree of dermal elastosis, epidermal atypia and histological types of actinic keratoses. Of the 28 actinic keratoses studied, the average percentage area of the elastic fibre was 40.48 +/- 14.48 (mean +/- SD) percentile. There was a 3.65-fold increase in the amount of elastic fibre in actinic keratoses compared with that of seborrhoeic keratoses occurring on the face (p < 0.00001). In addition, the more severe the atypia, the greater the area of elastic fibres in a representative section of the dermis. In conclusion, we observed that on quantitative assessment of elastic tissue in actinic keratoses, the percentage area of the elastic fibres in a representative section of the dermis ranges from 34.86 to 46.11%. This result may provide information for use in histological diagnosis of actinic keratoses and evidence for the possible role of sunlight in the pathogenesis of actinic keratosis.

  5. Clinical and histopathologic study of benign lichenoid keratosis on the face.

    PubMed

    Kim, Han Su; Park, Eun Joo; Kwon, In Ho; Kim, Kwang Ho; Kim, Kwang Joong

    2013-10-01

    Benign lichenoid keratosis is a cutaneous entity that consists of a nonpruritic papule or slightly indurated plaque that is histologically characterized by a band-like inflammatory infiltrate with interface involvement. The purpose of this study was to investigate the clinical and histopathologic features of benign lichenoid keratosis localized on the face. Fourteen benign lichenoid keratosis patients diagnosed clinically and histopathologically in our clinic during the 10-year period from 2002 to 2012 were studied. Thirteen female and 1 male patients were included. The mean age at diagnosis was 46.5 years. The color of most of the lesions was brown (10 cases, 71%). The cheek was the most commonly involved area (10 cases, 71%). All of the lesions were single. There were 9 (64%) flat lesion cases and 5 (36%) raised lesion cases. Most patients denied having any symptoms; 3 had mild pruritus. The histopathological findings indicated that all the cases exhibited lichenoid inflammatory infiltrate obscuring the dermal-epidermal junction and vacuolar alteration of basal cell layer. The lesions showed focal parakeratosis (79%), melanophages (79%), hyperkeratosis (71%), and necrotic keratinocytes (71%). Solar elastosis (50%) and acanthosis (43%) were also seen frequently. Diagnosis of benign lichenoid keratosis should be made by a combination of clinical manifestations and histopathological findings. In particular, benign lichenoid keratosis should be considered if a middle-aged patient presents a solitary asymptomatic brown lesion on the face. We think benign lichenoid keratosis may be a specific disorder rather than the inflammatory stage of regressing solar lentigines, large cell acanthoma or reticulated seborrheic keratosis.

  6. Actin-Regulator Feedback Interactions during Endocytosis

    PubMed Central

    Wang, Xinxin; Galletta, Brian J.; Cooper, John A.; Carlsson, Anders E.

    2016-01-01

    Endocytosis mediated by clathrin, a cellular process by which cells internalize membrane receptors and their extracellular ligands, is an important component of cell signaling regulation. Actin polymerization is involved in endocytosis in varying degrees depending on the cellular context. In yeast, clathrin-mediated endocytosis requires a pulse of polymerized actin and its regulators, which recruit and activate the Arp2/3 complex. In this article, we seek to identify the main protein-protein interactions that 1) cause actin and its regulators to appear in pulses, and 2) determine the effects of key mutations and drug treatments on actin and regulator assembly. We perform a joint modeling/experimental study of actin and regulator dynamics during endocytosis in the budding yeast Saccharomyces cerevisiae. We treat both a stochastic model that grows an explicit three-dimensional actin network, and a simpler two-variable Fitzhugh-Nagumo type model. The models include a negative-feedback interaction of F-actin onto the Arp2/3 regulators. Both models explain the pulse time courses and the effects of interventions on actin polymerization: the surprising increase in the peak F-actin count caused by reduced regulator branching activity, the increase in F-actin resulting from slowing of actin disassembly, and the increased Arp2/3 regulator lifetime resulting from latrunculin treatment. In addition, they predict that decreases in the regulator branching activity lead to increases in accumulation of regulators, and we confirmed this prediction with experiments on yeast harboring mutations in the Arp2/3 regulators, using quantitative fluorescence microscopy. Our experimental measurements suggest that the regulators act quasi-independently, in the sense that accumulation of a particular regulator is most strongly affected by mutations of that regulator, as opposed to the others. PMID:27028652

  7. [Keratosis follicularis spinulosa decalvans. Therapy with isotretinoin and etretinate in the inflammatory stage].

    PubMed

    Richard, G; Harth, W

    1993-08-01

    Keratosis follicularis spinulosa decalvans (KFSD) is a rare X-linked disorder of keratinization of the hair follicle associated with corneal dystrophy. The clinical picture is characterized by solid follicular hyperkeratosis, especially on the exposed skin, sparse eyebrows/eyelashes, follicular scaling and scarring alopecia of the scalp, dry skin and ocular symptoms with keratitis and photophobia. We describe the three stages of the disease: onset, inflammation and partial remission and the treatment appropriate in each. Two patients in the inflammatory stage of KFSD, with recurrent deep, fibrosing folliculitis and perifolliculitis followed by spreading and scarring alopecia on the scalp, responded to oral therapy with retinoids. In both cases there was a distinct and lasting remission of the inflammation and stabilization of the spreading alopecia after treatment with etretinate (Tigason), up to 0.8 mg/kg body weight, or isotretinoin (Roaccutan), 0.5 mg/kg body weight, for 12 weeks. The follicular spinulous hyperkeratosis became softer, but persisted. Thus, oral therapy with retinoids appears helpful in the inflammatory stage of KFSD, even though there is little improvement in the follicular hyperkeratosis.

  8. Treatment of Bowen Disease With Photodynamic Therapy and the Advantages of Sequential Topical Imiquimod.

    PubMed

    Victoria-Martínez, A M; Martínez-Leborans, L; Ortiz-Salvador, J M; Pérez-Ferriols, A

    2017-03-01

    Photodynamic therapy (PDT) has been shown to be useful and effective in the treatment of actinic keratosis, Bowen disease, and basal cell carcinoma. We present a series of 13 Bowen disease lesions treated using PDT. Complete responses were achieved in 11 (84%) of the lesions after 3 months of treatment; at 18 months, complete responses were seen in 9 (70%) of the lesions. Patients who presented a partial response or recurrence were treated with topical 5% imiquimod and achieved complete responses. The lesions that presented partial response or recurrence were the largest lesions, between 3 and 5cm in diameter. PDT in monotherapy or combined sequentially with imiquimod is an excellent and well-tolerated therapeutic option for Bowen disease. The treatment has few adverse effects and shows satisfactory results, particularly in multiple large lesions in areas of difficult surgical reconstruction or in elderly patients with a high surgical risk.

  9. Why is Actin Patchy?

    NASA Astrophysics Data System (ADS)

    Carlsson, Anders

    2009-03-01

    The intracellular protein actin, by reversibly polymerizing into filaments, generates forces for motion and shape changes of many types of biological cells. Fluorescence imaging studies show that actin often occurs in the form of localized patches of size roughly one micrometer at the cell membrane. Patch formation is most prevalent when the free-actin concentration is low. I investigate possible mechanisms for the formation of actin patches by numerically simulating the ``dendritic nucleation'' model of actin network growth. The simulations include filament growth, capping, branching, severing, and debranching. The attachment of membrane-bound activators to actin filaments, and subsequent membrane diffusion of unattached activators, are also included. It is found that as the actin concentration increases from zero, the actin occurs in patches at lower actin concentrations, and the size of the patches increases with increasing actin concentration. At a critical value of the actin concentration, the system undergoes a transition to complete coverage. The results are interpreted within the framework of reaction-diffusion equations in two dimensions.

  10. Erbium laser resurfacing for actinic cheilitis.

    PubMed

    Cohen, Joel L

    2013-11-01

    Actinic cheilitis is a precancerous condition characterized by grayish-whitish area(s) of discoloration on the mucosal lip, often blunting the demarcation between mucosa and cutaneous lip. Actinic cheilitis is considered to be an early part of the spectrum of squamous cell carcinoma. Squamous cell carcinoma specifically of the lip has a high rate of recurrence and metastasis through the oral cavity leading to a poor overall survival. Risk factors for the development of actinic cheilitis include chronic solar irradiation, increasing age, male gender, light skin complexion, immunosuppression, and possibly tobacco and alcohol consumption. Treatment options include topical pharmacotherapy (eg, fluorouracil, imiquimod) or procedural interventions (eg, cryotherapy, electrosurgery, surgical vermillionectomy, laser resurfacing), each with their known advantages and disadvantages. There is little consensus as to which treatment options offer the most clinical utility given the paucity of comparative clinical data. In my practice, laser resurfacing has become an important tool for the treatment of actinic cheilitis owing to its ease of use and overall safety, tolerability, and cosmetic acceptability. Herein the use of erbium laser resurfacing is described for three actinic cheilitis presentations for which I find it particularly useful: clinically prominent actinic cheilitis, biopsy-proven actinic cheilitis, and treatment of the entire lip following complete tumor excision of squamous cell carcinoma. All patients were treated with a 2940-nm erbium laser (Sciton Profile Contour Tunable Resurfacing Laser [TRL], Sciton, Inc., Palo Alto, CA).

  11. Nagashima-type palmoplantar keratosis in a Chinese Han population

    PubMed Central

    Zhang, Jia; Zhang, Guolong; Ni, Cheng; Cheng, Ruhong; Liang, Jianying; Li, Ming; Yao, Zhirong

    2016-01-01

    Nagashima-type palmoplantar keratosis (NPPK) is an autosomal recessive form of palmoplantar keratoderma (PPK), which is caused by mutations in the SERPINB7 gene. NPPK has only been reported in Japanese and Chinese populations. The present study was conducted on 12 unrelated Chinese patients who were clinically predicted to suffer from NPPK. Mutation screening was performed by direct sequencing of the entire coding regions of SERPINB7, SLURP1, AQP5, CSTA, KRT1 and KRT9 genes. Direct sequencing of SERPINB7 revealed five homozygous founder mutations (c.796C>T) and four compound heterozygous mutations in nine patients, including one novel mutation (c.122_127delTGGTCC). Nine out of the 12 patients were diagnosed with NPPK due to SERPINB7 pathogenic mutations, and the results expanded the known mutation spectrum of NPPK. Taking the other seven reported Chinese patients, who had been definitively diagnosed with NPPK by genetic testing, into account, the present study further demonstrated that NPPK is a common entity in Mainland China, and c.796C>T is the most prevalent mutation and exerts a founder effect. Furthermore, the NPPK cases described in the current study presented a consistently mild phenotype, as compared with the degrees of phenotypic variability associated with other types of relatively severe PPK, including Mal de Meleda and Olmsted syndrome. PMID:27666198

  12. Regressing basal-cell carcinoma masquerading as benign lichenoid keratosis

    PubMed Central

    Kulberg, Aleksandra; Weyers, Wolfgang

    2016-01-01

    Background Benign lichenoid keratosis (BLK, LPLK) is often misdiagnosed clinically as superficial basal-cell carcinoma (BCC), especially when occurring on the trunk. However, BCCs undergoing regression may be associated with a lichenoid interface dermatitis that may be misinterpreted as BLK in histopathologic sections. Methods In order to assess the frequency of remnants of BCC in lesions interpreted as BLK, we performed step sections on 100 lesions from the trunk of male patients that had been diagnosed as BLK. Results Deeper sections revealed remnants of superficial BCC in five and remnants of a melanocytic nevus in two specimens. In the original sections of cases in which a BCC showed up, crusts tended to be more common, whereas vacuolar changes at the dermo-epidermal junction and melanophages in the papillary dermis tended to be less common and less pronounced. Conclusions Lesions from the trunk submitted as BCC and presenting histopathologically as a lichenoid interface dermatitis are not always BLKs. Although no confident recommendations can be given on the basis of this limited study, deeper sections may be warranted if lesions are crusted and/or associated with only minimal vacuolar changes at the dermo-epidermal junction and no or few melanophages in the papillary dermis. PMID:27867740

  13. Familial keratosis follicularis spinulosa decalvans associated with woolly hair.

    PubMed

    Lacarrubba, Francesco; Dall'Oglio, Federica; Rossi, Alfredo; Schwartz, Robert A; Micali, Giuseppe

    2007-08-01

    Keratosis follicularis spinulosa decalvans (KFSD) is a rare inherited disorder of keratinization clinically characterized by diffuse follicular hyperkeratosis, progressive scarring alopecia of scalp, eyebrows and eyelashes, corneal dystrophy and photophobia. Woolly hair is a hereditary condition, transmitted as an autosomal dominant or recessive trait, usually seen in Caucasians at birth or shortly after, in which there are curly, thick, often heavily pigmented hairs. We report two cases, a son and his mother, in whom KFSD occurred in association with woolly hair. In addition, various dental anomalies, including agenesis, inclusions and teeth malformations, were present in the child. Interestingly, both patients simultaneously developed an inflammatory tinea capitis caused by Microsporum canis. To our knowledge, the association of KFSD with woolly hair has not been described. The dental anomalies found in the child are intriguing, as they have never been reported previously in patients with KFSD. Finally, the concomitant onset of inflammatory tinea capitis in both patients may be explained by the enhanced susceptibility to fungal infection in keratinizing disorders.

  14. Profilin connects actin assembly with microtubule dynamics

    PubMed Central

    Nejedla, Michaela; Sadi, Sara; Sulimenko, Vadym; de Almeida, Francisca Nunes; Blom, Hans; Draber, Pavel; Aspenström, Pontus; Karlsson, Roger

    2016-01-01

    Profilin controls actin nucleation and assembly processes in eukaryotic cells. Actin nucleation and elongation promoting factors (NEPFs) such as Ena/VASP, formins, and WASP-family proteins recruit profilin:actin for filament formation. Some of these are found to be microtubule associated, making actin polymerization from microtubule-associated platforms possible. Microtubules are implicated in focal adhesion turnover, cell polarity establishment, and migration, illustrating the coupling between actin and microtubule systems. Here we demonstrate that profilin is functionally linked to microtubules with formins and point to formins as major mediators of this association. To reach this conclusion, we combined different fluorescence microscopy techniques, including superresolution microscopy, with siRNA modulation of profilin expression and drug treatments to interfere with actin dynamics. Our studies show that profilin dynamically associates with microtubules and this fraction of profilin contributes to balance actin assembly during homeostatic cell growth and affects micro­tubule dynamics. Hence profilin functions as a regulator of microtubule (+)-end turnover in addition to being an actin control element. PMID:27307590

  15. Keratosis follicularis spinulosa decalvans. Report of two cases and literature review.

    PubMed

    Rand, R; Baden, H P

    1983-01-01

    We report herein two cases of keratosis follicularis spinulosa decalvans (KFSD) and review the literature on this condition. The entity is one of a group of related disorders that shows keratosis pilaris with inflammation followed by atrophy. The clinical features and course of KFSD are characteristic. During infancy, keratosis pilaris begins on the face and, by childhood, progresses to involve the trunk and extremities. Sometime during childhood or up to the early teenage years, a cicatricial alopecia of the scalp and eyebrows develops and is the hallmark of this disorder. Hyperkeratosis of the palms and soles is a frequently associated finding and is usually manifested during adolescence. Other features occurring with this syndrome include atopy, photophobia, and corneal abnormalities. Sex-linked inheritance has been proposed by several authors.

  16. Three percent diclofenac in 2.5% hyaluronan gel in the treatment of actinic keratoses: a meta-analysis of the recent studies.

    PubMed

    Pirard, D; Vereecken, P; Mélot, C; Heenen, M

    2005-11-01

    Three percent diclofenac in 2.5% hyaluronan gel (DHA) is approved by the Food and Drug Administration (FDA) in the treatment of actinic keratoses (AK). We conducted a meta-analysis of the few prospective studies that evaluated the effect of DHA on the target lesion number score TLNS0 (indicating complete resolution of all target lesions in the treatment area) and/or the cumulative target lesion number score CLNS0 (indicating resolution of the target and new lesions in the treatment area) with assessment 30 days after the end of treatment. A comprehensive search of the 1966-2005 MEDLINE database and review of the reference lists of relevant articles identified the published randomised trials. Three studies were included, with a total of 364 patients. The placebo was the hyaluronan vehicle gel (HAV). The intention-to-treat analyses show that DHA significantly improve the TLNS0 (OR= 3.72; 95% CI=2.05-6.74) and the CLNS0 (OR=4.09; 95% CI=2.55-6.56) compare to HAV. Overall, 42/106 (39.6% CI: 30.8- 49.1%) had a TLNS0 with mean treatment duration of 75 days +/- 21 [mean+/-standard deviation (SD)], and 70/179 (39.1% CI:32.3-46.4%) patients had a CLNS0 with a mean 78 days+/-16 treatment duration. DHA is effective compared to HAV in the treatment of AK. Further studies should establish subgroup analyses according to sites and severity of the AK lesions in order to determine if more patients could be improved in restricted indications. Biopsies, a longer follow-up evaluation, and comparisons with the other treatments of AK will also be helpful in the future to define the place of this treatment in the management of AK.

  17. Actinic cheilitis in dental practice.

    PubMed

    Savage, N W; McKay, C; Faulkner, C

    2010-06-01

    Actinic cheilitis is a potentially premalignant condition involving predominantly the vermilion of the lower lip. The aim of the current paper was to review the clinical presentation of actinic cheilitis and demonstrate the development of management plans using a series of cases. These are designed to provide immediate treatment where required but also to address the medium and long-term requirements of the patient. The authors suggest that the clinical examination of lips and the assessment of actinic cheilitis and other lip pathology become a regular part of the routine soft tissue examination undertaken as a part of the periodic examination of dental patients. Early recognition of actinic cheilitis can allow the development of strategies for individual patients that prevent progression. These are based on past sun exposure, future lifestyle changes and the daily use of emollient sunscreens, broad-brimmed hats and avoidance of sun exposure during the middle of the day. This is a service that is not undertaken as a matter of routine in general medical practice as patients are not seen with the regularity of dental patients and generally not under the ideal examination conditions available in the dental surgery.

  18. Neurite outgrowth is driven by actin polymerization even in the presence of actin polymerization inhibitors

    PubMed Central

    Chia, Jonathan X.; Efimova, Nadia; Svitkina, Tatyana M.

    2016-01-01

    Actin polymerization is a universal mechanism to drive plasma membrane protrusion in motile cells. One apparent exception to this rule is continuing or even accelerated outgrowth of neuronal processes in the presence of actin polymerization inhibitors. This fact, together with the key role of microtubule dynamics in neurite outgrowth, led to the concept that microtubules directly drive plasma membrane protrusion either in the course of polymerization or by motor-driven sliding. The possibility that unextinguished actin polymerization drives neurite outgrowth in the presence of actin drugs was not explored. We show that cultured hippocampal neurons treated with cytochalasin D or latrunculin B contained dense accumulations of branched actin filaments at ∼50% of neurite tips at all tested drug concentrations (1–10 μM). Actin polymerization is required for neurite outgrowth because only low concentrations of either inhibitor increased the length and/or number of neurites, whereas high concentrations inhibited neurite outgrowth. Of importance, neurites undergoing active elongation invariably contained a bright F-actin patch at the tip, whereas actin-depleted neurites never elongated, even though they still contained dynamic microtubules. Stabilization of microtubules by Taxol treatment did not stop elongation of cytochalasin–treated neurites. We conclude that actin polymerization is indispensable for neurite elongation. PMID:27682586

  19. Improved patient satisfaction using ingenol mebutate gel 0.015% for the treatment of facial actinic keratoses: a prospective pilot study.

    PubMed

    Emilio, Joanna; Schwartz, Michelle; Feldman, Eleanor; Bieber, Amy Kalowitz; Bienenfeld, Amanda; Jung, Min-Kyung; Siegel, Daniel M; Markowitz, Orit

    2016-01-01

    Actinic keratoses (AKs), especially on areas of the face, have a negative impact on a patient's quality of life (QoL). These lesions manifest on sun-damaged skin and have the potential to progress to squamous cell carcinoma. Field-directed therapy alone and in combination with lesion-directed treatment is effective in clearing both visible and nonvisible AK lesions. Topical treatments of AKs thus have the potential to improve a patient's well-being. However, evidence demonstrating improvements in patient QoL is limited, and is mostly based on observational or retrospective studies. Some prospective studies have reported unchanged or even worsening QoL despite excellent treatment outcomes. Our prospective, pilot study demonstrated a significant increase in QoL in 28 subjects with AKs of the face treated with ingenol mebutate gel 0.015%. QoL was assessed at days 0 and 60 using the Skindex-16 survey. Mean overall scores improved from 24.5% at baseline to 15.5% at day 60 (P=0.031). Improvements in QoL were consistent with an 80% reduction in AK lesion number at day 60. These improved QoL findings are in line with those from a recent retrospective study using ingenol mebutate 0.015% gel. This study therefore further demonstrates the potential for field therapy to improve both treatment outcomes and patient satisfaction.

  20. A Clinicopathological and Dermoscopic Correlation of Seborrheic Keratosis

    PubMed Central

    Alapatt, Geethu Francis; Sukumar, D; Bhat, M Ramesh

    2016-01-01

    Background: Seborrheic keratosis (SK) is the most common benign epidermal tumor of the skin. Even though SK has been well characterized clinically, dermoscopically, and histopathologically, data regarding clinical dermoscopic and histopathological correlation of different types of SK are inadequate. Aim: We carried out this study to establish any correlation between the clinical, dermoscopic, and histopathological appearance of SK and its variants. Methods: This was a descriptive study. Patients with SK were evaluated with respect to age, sex, family history of similar lesions, site of lesions, and symptoms associated with the lesions. Dermoscopy was performed in all cases. Biopsies were taken from the lesions and assessed for histopathology. Results: The most common age group affected by SK was 31–50 years (42%). A female preponderance of 76% was seen. Majority of our patients had a positive family history (62%), though Sun exposure was not seen to be a major factor. The most common clinical variant was common SK (CSK) (46%). The most common dermoscopic findings seen in CSK were comedo-like (CL) openings, fissures and ridges (FR), and milia-like (ML) cysts. Dermatosis papulosa nigra and pedunculated SK had characteristic FR and CL openings on dermoscopy. Stucco keratoses showed network-like (NL) structures and sharp demarcation. CL opening on dermoscopy corresponded to papillomatosis and pigmentation, ML cysts corresponded to horn cysts, FR corresponded to papillomatosis, and NL structures corresponded to an increase in basal layer pigmentation. Conclusions: This study emphasizes the use of dermoscopy in improving the diagnostic accuracy of SK. The correlation between the various histological and dermoscopic features is described. PMID:27904179

  1. Keratosis follicularis spinulosa decalvans: a rare cause of scarring alopecia in two young Indian girls.

    PubMed

    Maheswari, Uma G; Chaitra, V; Mohan, Subbiah S

    2013-01-01

    Keratosis follicularis spinulosa decalvans (KFSD) is an X-linked xenodermatosis characterized by scarring alopecia and follicular hyperkeratosis. This condition mainly affects males with females being carriers and will have milder symptoms. We present two sisters with severe form of KFSD, progressing to scarring alopecia.

  2. Keratosis follicularis spinulosa decalvans: report of a case with ultrastructural study and unsuccessful trial of retinoids.

    PubMed

    Puppin, D; Aractingi, S; Dubertret, L; Blanchet-Bardon, C

    1992-01-01

    Keratosis follicularis spinulosa decalvans (KFSD) is a genetic disorder characterized by disseminated follicular hyperkeratosis, especially localizated to scalp and face. We report the case of a new patient displaying typical features of KFSD. Ultrastructural study was performed and displayed round keratohyalin granules in follicular keratinocytes. Trial with etretinate, which has not been reported before in this disease, proved to be ineffective.

  3. Keratosis Follicularis Spinulosa Decalvans: A Rare Cause of Scarring Alopecia in Two Young Indian Girls

    PubMed Central

    Maheswari, Uma G; Chaitra, V; Mohan, Subbiah S

    2013-01-01

    Keratosis follicularis spinulosa decalvans (KFSD) is an X-linked xenodermatosis characterized by scarring alopecia and follicular hyperkeratosis. This condition mainly affects males with females being carriers and will have milder symptoms. We present two sisters with severe form of KFSD, progressing to scarring alopecia. PMID:23960394

  4. [Keratosis follicularis spinulosa decalvans associated with patent ductus arteriosus and hypospadia in an Asiatic patient].

    PubMed

    Harth, W; Linse, R

    1999-04-01

    Keratosis follicularis spinulosa decalvans (KFSD) appeared sporadically in an Asian boy, who also presented with naevus teleangiectaticus lateralis, patent ductus arteriosus (Botalli) and hypospadia. The association of these findings raises the question of a new syndrome. In addition, this is the first report of KFSD in a patient of Asian origin.

  5. Effects of latrunculin B on the actin cytoskeleton and hyphal growth in Phytophthora infestans.

    PubMed

    Ketelaar, Tijs; Meijer, Harold J G; Spiekerman, Marjolein; Weide, Rob; Govers, Francine

    2012-12-01

    The actin cytoskeleton is conserved in all eukaryotes, but its functions vary among different organisms. In oomycetes, the function of the actin cytoskeleton has received relatively little attention. We have performed a bioinformatics study and show that oomycete actin genes fall within a distinct clade that is divergent from plant, fungal and vertebrate actin genes. To obtain a better understanding of the functions of the actin cytoskeleton in hyphal growth of oomycetes, we studied the actin organization in Phytophthora infestans hyphae and the consequences of treatment with the actin depolymerising drug latrunculin B (latB). This revealed that latB treatment causes a concentration dependent inhibition of colony expansion and aberrant hyphal growth. The most obvious aberrations observed upon treatment with 0.1 μM latB were increased hyphal branching and irregular tube diameters whereas at higher concentrations latB (0.5 and 1 μM) tips of expanding hyphae changed into balloon-like shapes. This aberrant growth correlated with changes in the organization of the actin cytoskeleton. In untreated hyphae, staining with fluorescently tagged phalloidin revealed two populations of actin filaments: long, axially oriented actin filament cables and cortical actin filament plaques. Two hyphal subtypes were recognized, one containing only plaques and the other containing both cables and plaques. In the latter, some hyphae had an apical zone without actin filament plaques. Upon latB treatment, the proportion of hyphae without actin filament cables increased and there were more hyphae with a short apical zone without actin filament plaques. In general, actin filament plaques were more resilient against actin depolymerisation than actin filament cables. Besides disturbing hyphal growth and actin organization, actin depolymerisation also affected the positioning of nuclei. In the presence of latB, the distance between nuclei and the hyphal tip decreased, suggesting that the actin

  6. Pharmacological characterization of actin-binding (-)-doliculide.

    PubMed

    Foerster, Florian; Braig, Simone; Chen, Tao; Altmann, Karl-Heinz; Vollmar, Angelika M

    2014-09-15

    Natural compounds offer a broad spectrum of potential drug candidates against human malignancies. Several cytostatic drugs, which are in clinical use for decades, derive directly from natural sources or are synthetically optimized derivatives of natural lead structures. An eukaryote target molecule to which many natural derived anti-cancer drugs bind to is the microtubule network. Of similar importance for the cell is the actin cytoskeleton, responsible for cell movements, migration of cells and cytokinesis. Nature provides also a broad range of compounds directed against actin as intracellular target, but none of these actin-targeting compounds has ever been brought to clinical trials. One reason why actin-binding compounds have not yet been considered for further clinical investigations is that little is known about their pharmacological properties in cancer cells. Herein, we focused on the closer characterization of doliculide, an actin binding natural compound of marine origin in the breast cancer cell lines MCF7 and MDA-MB-231. We used fluorescence-recovery-after-photobleaching (FRAP) analysis to determine doliculide's early effects on the actin cytoskeleton and rhodamin-phalloidin staining for long-term effects on the actin CSK. After validating the disruption of the actin network, we further investigated the functional effects of doliculide. Doliculide treatment leads to inhibition of proliferation and impairs the migratory potential. Finally, we could also show that doliculide leads to the induction of apoptosis in both cell lines. Our data for the first time provide a closer characterization of doliculide in breast cancer cells and propagate doliculide for further investigations as lead structure and potential therapeutic option as actin-targeting compound.

  7. Topical AC-11 abates actinic keratoses and early squamous cell cancers in hairless mice exposed to Ultraviolet A (UVA) radiation.

    PubMed

    Mentor, Julian M; Etemadi, Amir; Patta, Abrienne M; Scheinfeld, Noah

    2015-04-16

    AC-11 is an aqueous extract of the botanical, Uncaria tomentosa, which has a variety of effects that enhance DNA repair and down regulate inflammation. AC-11 is essentially free of oxindole alkaloids (< 0.05%, w/w) but contains more than 8% carboxy alkyl esters (CAEs) as their active ingredients. Three groups of 10 outbred SK-1 hairless or SK-II hairless strains of mice each were treated with AC-11 at 0.5%, 1.5%, and 3.0% in a non-irritating, dye-free, perfume-free, and fragrance-free vanishing cream vehicle. Ten mice used vehicle only and 10 were untreated. Each concentration of AC-11 and was applied daily to the backs of the mice prior to exposure to a 1,600-watt solar simulator used in this work (Solar Light Co. Philadelphia, PA) emitting (mainly Ultraviolet A (UVA) and B (UVB) radiation) duration of the experimental period with UVB wavelengths was filtered out with a 1.0 cm Schott WG 345 filter. AC-11 with a peak absorption at 200nm does act as a sun block. We tested for and focused on clinical appearance of mice and histological appearance of tumors in mice rather than metrics of radiation generated inflammation. Tumor progression scores were assigned as follows: 4+ = extensive tumor development; 3+ = early malignancies (raised palpable plaques)(early squamous cell cancers) 2+ = firm scaling, palpable keratosis (actinic keratoses); 1+ = light scaling with erythema. Following a total cumulative dose of 738 J/cm2, 85.7% all of the irradiated control animals, which did not receive AC-11 had precancerous actinic keratosis (AK)-type lesions (2+) (64.3% versus 42.9%) or early squamous cell carcinoma (SCC) (3+) (21.4% vs. 4.8%), in comparison with 47.7 % of AC-11-treated animals. There were no significant differences between the AC-11 groups. Three months after cessation of exposure to UVA radiation, the lesions in all but three of the 14 animals which were treated with AC-11 that were still evaluable irradiated with UVA radiation progressed to papillomas and frank

  8. Actin Mechanics and Fragmentation*

    PubMed Central

    De La Cruz, Enrique M.; Gardel, Margaret L.

    2015-01-01

    Cell physiological processes require the regulation and coordination of both mechanical and dynamical properties of the actin cytoskeleton. Here we review recent advances in understanding the mechanical properties and stability of actin filaments and how these properties are manifested at larger (network) length scales. We discuss how forces can influence local biochemical interactions, resulting in the formation of mechanically sensitive dynamic steady states. Understanding the regulation of such force-activated chemistries and dynamic steady states reflects an important challenge for future work that will provide valuable insights as to how the actin cytoskeleton engenders mechanoresponsiveness of living cells. PMID:25957404

  9. Actin Polymerization is Stimulated by Actin Crosslinking Protein Palladin

    PubMed Central

    Gurung, Ritu; Yadav, Rahul; Brungardt, Joseph G.; Orlova, Albina; Egelman, Edward H.; Beck, Moriah R.

    2016-01-01

    The actin scaffold protein palladin regulates both normal cell migration and invasive cell motility, processes that require the coordinated regulation of actin dynamics. However, the potential effect of palladin on actin dynamics has remained elusive. Here we show that the actin binding immunoglobulin-like domain of palladin, which is directly responsible for both actin binding and bundling, also stimulates actin polymerization in vitro. Palladin eliminated the lag phase that is characteristic of the slow nucleation step of actin polymerization. Furthermore, palladin dramatically reduced depolymerization, slightly enhanced the elongation rate, and did not alter the critical concentration. Microscopy and in vitro crosslinking assays reveal differences in actin bundle architecture when palladin is incubated with actin before or after polymerization. These results suggest a model whereby palladin stimulates a polymerization-competent form of G-actin, akin to metal ions, either through charge neutralization or conformational changes. PMID:26607837

  10. Axonal actin in action: Imaging actin dynamics in neurons.

    PubMed

    Ladt, Kelsey; Ganguly, Archan; Roy, Subhojit

    2016-01-01

    Actin is a highly conserved, key cytoskeletal protein involved in numerous structural and functional roles. In neurons, actin has been intensively investigated in axon terminals-growth cones-and dendritic spines, but details about actin structure and dynamics in axon shafts have remained obscure for decades. A major barrier in the field has been imaging actin. Actin exists as soluble monomers (G-actin) as well as actin filaments (F-actin), and labeling actin with conventional fluorescent probes like GFP/RFP typically leads to a diffuse haze that makes it difficult to discern kinetic behaviors. In a recent publication, we used F-actin selective probes to visualize actin dynamics in axons, resolving striking actin behaviors that have not been described before. However, using these probes to visualize actin dynamics is challenging as they can cause bundling of actin filaments; thus, experimental parameters need to be strictly optimized. Here we describe some practical methodological details related to using these probes for visualizing F-actin dynamics in axons.

  11. Rare case of external dental fistula of the submental region misdiagnosed as inverted follicular keratosis and thyroglossal duct cyst

    PubMed Central

    Sato, Toshihisa; Suenaga, Hideyuki; Igarashi, Masaki; Hoshi, Kazuto; Takato, Tsuyoshi

    2015-01-01

    Introduction Odontogenic cutaneous sinus tract is a relatively rare occurrence that can be complicated to diagnose. The presence of a cutaneous lesion is often not even partly associated with a dental etiology because of the less frequency of occurrence in the case of dental symptoms. Consequently, the underlying dental cause is often missed leading to inappropriate diagnosis and treatment. Case presentation Here, we report the case of a 45-year-old man who presented with a persistent lesion of the cervical region. At the time of presentation, the lesion had been present for approximately one year with a gradual increase in size but no specific symptoms. The patient had previously undergone punch resection under local anesthesia, which resulted in a histopathological diagnosis of inverted follicular keratosis. A diagnosis was made of an odontogenic cutaneous sinus tract secondary to chronic apical periodontitis of the left mandibular second molar. Discussion Cutaneous sinus tract in the face and neck is most likely to develop intraorally. Root canal treatment or surgical extractions are the common treatment choices. A previously reported review of 137 cases found that 106 (77%) were treated by extraction and 27 (20%) were treated by surgical or conservative nonsurgical endodontic therapy. Conclusion Early diagnosis of cutaneous sinus tract using proper aid is responsible for shortening the treatment duration and avoiding unnecessary treatment. PMID:26413920

  12. Dexamethasone alters F-actin architecture and promotes cross-linked actin network formation in human trabecular meshwork tissue.

    PubMed

    Clark, Abbot F; Brotchie, Daniel; Read, A Thomas; Hellberg, Peggy; English-Wright, Sherry; Pang, Iok-Hou; Ethier, C Ross; Grierson, Ian

    2005-02-01

    Elevated intraocular pressure is an important risk factor for the development of glaucoma, a leading cause of irreversible blindness. This ocular hypertension is due to increased hydrodynamic resistance to the drainage of aqueous humor through specialized outflow tissues, including the trabecular meshwork (TM) and the endothelial lining of Schlemm's canal. We know that glucocorticoid therapy can cause increased outflow resistance and glaucoma in susceptible individuals, that the cytoskeleton helps regulate aqueous outflow resistance, and that glucocorticoid treatment alters the actin cytoskeleton of cultured TM cells. Our purpose was to characterize the actin cytoskeleton of cells in outflow pathway tissues in situ, to characterize changes in the cytoskeleton due to dexamethasone treatment in situ, and to compare these with changes observed in cell culture. Human ocular anterior segments were perfused with or without 10(-7) M dexamethasone, and F-actin architecture was investigated by confocal laser scanning microscopy. We found that outflow pathway cells contained stress fibers, peripheral actin staining, and occasional actin "tangles." Dexamethasone treatment caused elevated IOP in several eyes and increased overall actin staining, with more actin tangles and the formation of cross-linked actin networks (CLANs). The actin architecture in TM tissues was remarkably similar to that seen in cultured TM cells. Although CLANs have been reported previously in cultured cells, this is the first report of CLANs in tissue. These cytoskeletal changes may be associated with increased aqueous humor outflow resistance after ocular glucocorticoid treatment.

  13. Polycation induced actin bundles.

    PubMed

    Muhlrad, Andras; Grintsevich, Elena E; Reisler, Emil

    2011-04-01

    Three polycations, polylysine, the polyamine spermine and the polycationic protein lysozyme were used to study the formation, structure, ionic strength sensitivity and dissociation of polycation-induced actin bundles. Bundles form fast, simultaneously with the polymerization of MgATP-G-actins, upon the addition of polycations to solutions of actins at low ionic strength conditions. This indicates that nuclei and/or nascent filaments bundle due to attractive, electrostatic effect of polycations and the neutralization of repulsive interactions of negative charges on actin. The attractive forces between the filaments are strong, as shown by the low (in nanomolar range) critical concentration of their bundling at low ionic strength. These bundles are sensitive to ionic strength and disassemble partially in 100 mM NaCl, but both the dissociation and ionic strength sensitivity can be countered by higher polycation concentrations. Cys374 residues of actin monomers residing on neighboring filaments in the bundles can be cross-linked by the short span (5.4Å) MTS-1 (1,1-methanedyl bismethanethiosulfonate) cross-linker, which indicates a tight packing of filaments in the bundles. The interfilament cross-links, which connect monomers located on oppositely oriented filaments, prevent disassembly of bundles at high ionic strength. Cofilin and the polysaccharide polyanion heparin disassemble lysozyme induced actin bundles more effectively than the polylysine-induced bundles. The actin-lysozyme bundles are pathologically significant as both proteins are found in the pulmonary airways of cystic fibrosis patients. Their bundles contribute to the formation of viscous mucus, which is the main cause of breathing difficulties and eventual death in this disorder.

  14. MBTPS2 mutation in a British pedigree with keratosis follicularis spinulosa decalvans.

    PubMed

    Fong, K; Wedgeworth, E K; Lai-Cheong, J E; Tosi, I; Mellerio, J E; Powell, A M; McGrath, J A

    2012-08-01

    Keratosis follicularis spinulosa decalvans (KFSD; OMIM 308800) is an X-linked disorder characterized by widespread hyperkeratotic follicular papules (including keratosis pilaris-like lesions), facial erythema, hypotrichosis and scarring alopecia. KFSD results from mutations in the MBTPS2 gene. Mutations in this gene also underlie ichthyosis follicularis, alopecia and photophobia syndrome. We report a British pedigree with KFSD resulting from the mutation p.Asn508Ser. This particular mutation has been reported in three other pedigrees with KFSD (Dutch, American, British) and is the only pathogenic mutation reported in this disorder to date. However, the same mutation has also been reported in a Chinese pedigree with IFAP syndrome, highlighting the clinical heterogeneity and overlapping molecular pathology of these two disorders.

  15. Hypotrichosis with keratosis pilaris: electrophoretical study of hair fibrous proteins from a patient.

    PubMed

    Dekio, S; Nagashima, T; Watanabe, Y; Jidoi, J

    1989-01-01

    S-carboxymethylated (SCM) fibrous proteins from the scalp hair of a patient with hypotrichosis with keratosis pilaris (HTKP) and from that of a normal individual were analyzed using two-dimensional electrophoresis. One SCM fibrous protein component was different electrophoretically in the HTKP patient. It is suggested that the brittleness of the HTKP hair might result from this alteration of the fibrous protein composition of the hair.

  16. Keratosis follicularis spinulosa decalvans. An infant with failure to thrive, deafness, and recurrent infections.

    PubMed

    Britton, H; Lustig, J; Thompson, B J; Meyer, S; Esterly, N B

    1978-05-01

    A 10-month-old male infant had keratosis follicularis spinulosa decalvans, an X-linked dominant disorder. His cutaneous abnormalities consisted of generalized hyperkeratosis, spiny follicular papular lesions, universal alopecia, and hypoplastic nails. Ocular changes characteristic of the disease were also present. Unusual findings included deafness, failure to thrive, predisposition to bacterial infections without demonstrable immune defect, and transient hepatomegaly with abnormal liver function studies.

  17. Photodynamic therapy for actinic keratoses.

    PubMed

    Kalisiak, Michal S; Rao, Jaggi

    2007-01-01

    Actinic keratoses (AKs) are one of the most common conditions that are treated by dermatologists and they have the potential to progress to squamous cell carcinoma if left untreated. Photodynamic therapy (PDT) has emerged as a novel and versatile method of treating those lesions. Topical preparations of aminolevulinic acid and methyl aminolevulinate are commercially available photosensitizers, and numerous light sources may be used for photoactivation. This article focuses on practical aspects of PDT in the treatment of AKs, outcomes of relevant clinical trials, and special applications of PDT in transplant recipients and other who are predisposed to AK formation. Step-by-step descriptions of PDT sessions are presented.

  18. Endothelial actin-binding proteins and actin dynamics in leukocyte transendothelial migration.

    PubMed

    Schnoor, Michael

    2015-04-15

    The endothelium is the first barrier that leukocytes have to overcome during recruitment to sites of inflamed tissues. The leukocyte extravasation cascade is a complex multistep process that requires the activation of various adhesion molecules and signaling pathways, as well as actin remodeling, in both leukocytes and endothelial cells. Endothelial adhesion molecules, such as E-selectin or ICAM-1, are connected to the actin cytoskeleton via actin-binding proteins (ABPs). Although the contribution of receptor-ligand interactions to leukocyte extravasation has been studied extensively, the contribution of endothelial ABPs to the regulation of leukocyte adhesion and transendothelial migration remains poorly understood. This review focuses on recently published evidence that endothelial ABPs, such as cortactin, myosin, or α-actinin, regulate leukocyte extravasation by controlling actin dynamics, biomechanical properties of endothelia, and signaling pathways, such as GTPase activation, during inflammation. Thus, ABPs may serve as targets for novel treatment strategies for disorders characterized by excessive leukocyte recruitment.

  19. Quantification of Filamentous Actin (F-actin) Puncta in Rat Cortical Neurons.

    PubMed

    Li, Hailong; Aksenova, Marina; Bertrand, Sarah J; Mactutus, Charles F; Booze, Rosemarie

    2016-02-10

    Filamentous actin protein (F-actin) plays a major role in spinogenesis, synaptic plasticity, and synaptic stability. Changes in dendritic F-actin rich structures suggest alterations in synaptic integrity and connectivity. Here we provide a detailed protocol for culturing primary rat cortical neurons, Phalloidin staining for F-actin puncta, and subsequent quantification techniques. First, the frontal cortex of E18 rat embryos are dissociated into low-density cell culture, then the neurons grown in vitro for at least 12-14 days. Following experimental treatment, the cortical neurons are stained with AlexaFluor 488 Phalloidin (to label the dendritic F-actin puncta) and microtubule-associated protein 2 (MAP2; to validate the neuronal cells and dendritic integrity). Finally, specialized software is used to analyze and quantify randomly selected neuronal dendrites. F-actin rich structures are identified on second order dendritic branches (length range 25-75 µm) with continuous MAP2 immunofluorescence. The protocol presented here will be a useful method for investigating changes in dendritic synapse structures subsequent to experimental treatments.

  20. Quantification of Filamentous Actin (F-actin) Puncta in Rat Cortical Neurons

    PubMed Central

    Bertrand, Sarah J.; Mactutus, Charles F.; Booze, Rosemarie

    2016-01-01

    Filamentous actin protein (F-actin) plays a major role in spinogenesis, synaptic plasticity, and synaptic stability. Changes in dendritic F-actin rich structures suggest alterations in synaptic integrity and connectivity. Here we provide a detailed protocol for culturing primary rat cortical neurons, Phalloidin staining for F-actin puncta, and subsequent quantification techniques. First, the frontal cortex of E18 rat embryos are dissociated into low-density cell culture, then the neurons grown in vitro for at least 12-14 days. Following experimental treatment, the cortical neurons are stained with AlexaFluor 488 Phalloidin (to label the dendritic F-actin puncta) and microtubule-associated protein 2 (MAP2; to validate the neuronal cells and dendritic integrity). Finally, specialized software is used to analyze and quantify randomly selected neuronal dendrites. F-actin rich structures are identified on second order dendritic branches (length range 25-75 µm) with continuous MAP2 immunofluorescence. The protocol presented here will be a useful method for investigating changes in dendritic synapse structures subsequent to experimental treatments. PMID:26889716

  1. Correlation between treatment time, photobleaching, inflammation and pain after photodynamic therapy with methyl aminolevulinate on tape-stripped skin in healthy volunteers.

    PubMed

    Lerche, Catharina M; Fabricius, Susanne; Philipsen, Peter A; Wulf, Hans Christian

    2015-05-01

    Photodynamic therapy (PDT) is an attractive treatment option for skin diseases such as actinic keratosis, since large skin areas can be treated with high response rates and good cosmetic outcomes. Nevertheless inflammation and pain are still major side effects. The aim of this study was to investigate the extent to which less time-consuming PDT treatment regimens using methyl aminolevulinate (MAL) decrease protoporphyrin IX (PpIX) photobleaching, inflammation and pain. Twenty-four healthy volunteers were treated with 4 different interventions on each forearm. All 8 fields were tape-stripped 10 times. On the right arm MAL was applied for 20, 40, 60 or 180 min, followed by further incubation after wiping off MAL until 180 min after start and then illuminating with red light 180 min after start. On the left arm MAL or vehicle was applied for 30, 60, or 90 min and illuminated immediately after MAL removal. PpIX fluorescence, photobleaching, objective and subjective erythema (as a measure for inflammation), pigmentation and pain were measured. The results showed a significant correlation between incubation time, time until illumination and photobleaching. Furthermore, there was a significant correlation between photobleaching and erythema and also between photobleaching and pain. In conclusion, shorter PDT regimens result in decreased photobleaching and also less inflammation and pain. We hypothesize that a shorter incubation time is important for the optimal specific subcellular distribution of PpIX and to avoid unspecific distribution. We propose a shorter PDT regimen, "Pulse PDT", comprising, for example 30 min incubation with MAL and illumination after 180 min, and we have planned a study of actinic keratosis and "Pulse PDT".

  2. Directed actin assembly and motility.

    PubMed

    Boujemaa-Paterski, Rajaa; Galland, Rémi; Suarez, Cristian; Guérin, Christophe; Théry, Manuel; Blanchoin, Laurent

    2014-01-01

    The actin cytoskeleton is a key component of the cellular architecture. However, understanding actin organization and dynamics in vivo is a complex challenge. Reconstitution of actin structures in vitro, in simplified media, allows one to pinpoint the cellular biochemical components and their molecular interactions underlying the architecture and dynamics of the actin network. Previously, little was known about the extent to which geometrical constraints influence the dynamic ultrastructure of these networks. Therefore, in order to study the balance between biochemical and geometrical control of complex actin organization, we used the innovative methodologies of UV and laser patterning to design a wide repertoire of nucleation geometries from which we assembled branched actin networks. Using these methods, we were able to reconstitute complex actin network organizations, closely related to cellular architecture, to precisely direct and control their 3D connections. This methodology mimics the actin networks encountered in cells and can serve in the fabrication of innovative bioinspired systems.

  3. Amplification of actin polymerization forces

    PubMed Central

    Dmitrieff, Serge; Nédélec, François

    2016-01-01

    The actin cytoskeleton drives many essential processes in vivo, using molecular motors and actin assembly as force generators. We discuss here the propagation of forces caused by actin polymerization, highlighting simple configurations where the force developed by the network can exceed the sum of the polymerization forces from all filaments. PMID:27002174

  4. Amplification of actin polymerization forces.

    PubMed

    Dmitrieff, Serge; Nédélec, François

    2016-03-28

    The actin cytoskeleton drives many essential processes in vivo, using molecular motors and actin assembly as force generators. We discuss here the propagation of forces caused by actin polymerization, highlighting simple configurations where the force developed by the network can exceed the sum of the polymerization forces from all filaments.

  5. Actin-binding proteins implicated in the formation of the punctate actin foci stimulated by the self-incompatibility response in Papaver.

    PubMed

    Poulter, Natalie S; Staiger, Christopher J; Rappoport, Joshua Z; Franklin-Tong, Vernonica E

    2010-03-01

    The actin cytoskeleton is a key target for signaling networks and plays a central role in translating signals into cellular responses in eukaryotic cells. Self-incompatibility (SI) is an important mechanism responsible for preventing self-fertilization. The SI system of Papaver rhoeas pollen involves a Ca(2+)-dependent signaling network, including massive actin depolymerization as one of the earliest cellular responses, followed by the formation of large actin foci. However, no analysis of these structures, which appear to be aggregates of filamentous (F-)actin based on phalloidin staining, has been carried out to date. Here, we characterize and quantify the formation of F-actin foci in incompatible Papaver pollen tubes over time. The F-actin foci increase in size over time, and we provide evidence that their formation requires actin polymerization. Once formed, these SI-induced structures are unusually stable, being resistant to treatments with latrunculin B. Furthermore, their formation is associated with changes in the intracellular localization of two actin-binding proteins, cyclase-associated protein and actin-depolymerizing factor. Two other regulators of actin dynamics, profilin and fimbrin, do not associate with the F-actin foci. This study provides, to our knowledge, the first insights into the actin-binding proteins and mechanisms involved in the formation of these intriguing structures, which appear to be actively formed during the SI response.

  6. Actin stress in cell reprogramming

    PubMed Central

    Guo, Jun; Wang, Yuexiu; Sachs, Frederick; Meng, Fanjie

    2014-01-01

    Cell mechanics plays a role in stem cell reprogramming and differentiation. To understand this process better, we created a genetically encoded optical probe, named actin–cpstFRET–actin (AcpA), to report forces in actin in living cells in real time. We showed that stemness was associated with increased force in actin. We reprogrammed HEK-293 cells into stem-like cells using no transcription factors but simply by softening the substrate. However, Madin-Darby canine kidney (MDCK) cell reprogramming required, in addition to a soft substrate, Harvey rat sarcoma viral oncogene homolog expression. Replating the stem-like cells on glass led to redifferentiation and reduced force in actin. The actin force probe was a FRET sensor, called cpstFRET (circularly permuted stretch sensitive FRET), flanked by g-actin subunits. The labeled actin expressed efficiently in HEK, MDCK, 3T3, and bovine aortic endothelial cells and in multiple stable cell lines created from those cells. The viability of the cell lines demonstrated that labeled actin did not significantly affect cell physiology. The labeled actin distribution was similar to that observed with GFP-tagged actin. We also examined the stress in the actin cross-linker actinin. Actinin force was not always correlated with actin force, emphasizing the need for addressing protein specificity when discussing forces. Because actin is a primary structural protein in animal cells, understanding its force distribution is central to understanding animal cell physiology and the many linked reactions such as stress-induced gene expression. This new probe permits measuring actin forces in a wide range of experiments on preparations ranging from isolated proteins to transgenic animals. PMID:25422450

  7. A comparison of dermoscopic features among lentigo senilis/initial seborrheic keratosis, seborrheic keratosis, lentigo maligna and lentigo maligna melanoma on the face.

    PubMed

    Sahin, Mustafa Turhan; Oztürkcan, Serap; Ermertcan, Aylin Türel; Güneş, Ali Tahsin

    2004-11-01

    Clinical differentiation of facial lentigo senilis/initial seborrheic keratosis (LS/ISK), seborrheic keratosis (SK), lentigo maligna (LM), and lentigo maligna melanoma (LMM) can be difficult. Dermoscopy improves the diagnoses in pigmented skin lesions (PSLs), but it is not helpful for the sun-exposed face because of the flat rete ridges without network-derived features. Therefore, development of new diagnostic criteria for this particular localization is a current issue of dermatology. In this retrospective study, dermoscopic slides of facial pigmented skin lesions of 66 patients referred to two clinics in Turkey were evaluated. Our aim was to determine the reliability of dermoscopy in the differentiation of these entities. The facial PSLs of 66 patients (34 males and 32 females) (median age: 58.2) were photographed with a Dermaphot (Heine, Hersching, Germany) over a five year period from November of 1995 to May of 2000. All of the dermoscopic slides were analysed according to 27 dermoscopic criteria developed by Schiffner et al. This data set contained 22 histologically proven malignant (14 LM, 8 early LMM) and 44 benign (18 SK, 26 LS/ISK) PSLs. In general, asymmetric pigmented follicular openings, dark streaks, slate-gray streaks, dark globules, slate-gray globules, dark dots, dark rhomboidal structures, light brown rhomboidal structures, dark homogeneous areas and dark pseudonetworks were statistically significant for malignant growth. On the other hand, milia-like cysts, pseudofollicular openings, cerebriform structures, light brown globules, light brown dots, light brown homogeneous areas, yellow opaque homogeneous areas, and light brown pseudonetworks were statistically significant for benign growth. This research emphasizes that dermoscopic features on the face differ from criteria used in other locations of the body. Analysis of the data suggests that dermoscopy can be used in the differentiation of LS/ISK, SK, LM and LMM from each other.

  8. Pigmented squamous cell carcinoma of the cheek skin probably arising from solar keratosis.

    PubMed

    Terada, Tadashi; Yamagami, Jun; Fugimoto, Atsushi; Tanaka, Kyoko; Sugiura, Makoto

    2003-07-01

    We report a rare case of pigmented squamous cell carcinoma (SCC) of the cheek skin probably arising from solar keratosis. An 80-year-old man was referred to our clinic because of a black skin nodule in the right cheek. The nodular lesion was 1 cm in diameter, dome-shaped, hard, sharply demarcated, partially erosive and telangiectatic at the border. The lesion was completely excised under the clinical diagnosis of probable seborrheic keratosis. Microscopically, cutaneous horn and mildly atypical squamous epithelia suggestive of previous solar keratosis were present in the surface of the lesion. The lesion consisted of atypical squamous cells with keratinization and intercellular bridges, and it was regarded as SCC. The SCC cells were seen to invade lightly into the upper dermis, where lymphocytic infiltrations and melanophages were noted. Characteristically, heavy deposition of melanin pigment was recognized in the SCC cells as well as in proliferated dendritic and pigment blockade melanocytes that were scattered or colonized within the SCC cell nests. Masson-Fontana stain revealed numerous melanin granules in the SCC cells, as well as in dendritic and pigment blockade melanocytes. Immunohistochemically, the SCC cells were positive for cytokeratins and epithelial membrane antigen, and negative for S-100 protein and HMB45 antigen. Dendritic and pigment blockade melanocytes were negative for cytokeratins, epithelial membrane antigen, and HMB45 antigen, but positive for S-100 protein. The present case suggests that SCC cells of the skin may induce proliferation of melanocytes. The differential diagnosis and the histogenesis of pigmented SCC of the skin are discussed.

  9. Actinic prurigo of the lip: Two case reports

    PubMed Central

    Miranda, Ana MO; Ferrari, Thiago M; Werneck, Juliana T; Junior, Arley Silva; Cunha, Karin S; Dias, Eliane P

    2014-01-01

    Actinic prurigo is a photodermatosis that can affect the skin, conjunctiva and lips. It is caused by an abnormal reaction to sunlight and is more common in high-altitude living people, mainly in indigenous descendants. The diagnosis of actinic prurigo can be challenging, mainly when lip lesions are the only manifestation, which is not a common clinical presentation. The aim of this article is to report two cases of actinic prurigo showing only lip lesions. The patients were Afro-American and were unaware of possible Indian ancestry. Clinical exam, photographs, videoroscopy examination and biopsy were performed, and the diagnosis of actinic prurigo was established. Topical corticosteroid and lip balm with ultraviolet protection were prescribed with excellent results. The relevance of this report is to show that although some patients may not demonstrate the classical clinical presentation of actinic prurigo, the associated clinical and histological exams are determinants for the correct diagnosis and successful treatment of this disease. PMID:25133153

  10. Autofluorescence of seborrheic keratosis (warts) and of tissue surrounding malignant tumors

    NASA Astrophysics Data System (ADS)

    Lohmann, Wolfgang; Schill, Wolf-Bernhard; Bohle, Rainer M.; Dreyer, Thomas

    1997-12-01

    Autofluorescence measurements on human tissue have revealed a decrease in intensity in malignant tumors and an increase in the healthy region adjacent to the tumor. This latter event might serve as a protective wall against the invasive tumor cells. The composition of this wall is still unknown. Antioxidants such as NADH might be involved. In the case of seborrheic keratosis (wart), the intensity is increased in the pigmented spots. Care must be taken, therefore, when warts are attached to malignant tumors. The resulting value is, then, not indicative for the condition of the system.

  11. Keratosis follicularis spinulosa decalvans: confirmation of linkage to Xp22.13-p22.2.

    PubMed

    Porteous, M E; Strain, L; Logie, L J; Herd, R M; Benton, E C

    1998-04-01

    Keratosis follicularis spinulosa decalvans (KFSD) is a rare, X linked disorder with skin and eye involvement (MIM 308800). We have studied a large British family with KFSD using polymorphic markers from Xp21-p23 and obtained a lod score of 2.056 at theta=0 with markers proximal and distal to the KFSD candidate region Xp22.13-p22.2 identified by Oosterwijk et al. Our data confirm the linkage to Xp22.13-p22.2 observed in the previously reported Dutch family, but fail to narrow the candidate interval for the KFSD locus.

  12. Keratosis follicularis spinulosa decalvans: confirmation of linkage to Xp22.13-p22.2.

    PubMed Central

    Porteous, M E; Strain, L; Logie, L J; Herd, R M; Benton, E C

    1998-01-01

    Keratosis follicularis spinulosa decalvans (KFSD) is a rare, X linked disorder with skin and eye involvement (MIM 308800). We have studied a large British family with KFSD using polymorphic markers from Xp21-p23 and obtained a lod score of 2.056 at theta=0 with markers proximal and distal to the KFSD candidate region Xp22.13-p22.2 identified by Oosterwijk et al. Our data confirm the linkage to Xp22.13-p22.2 observed in the previously reported Dutch family, but fail to narrow the candidate interval for the KFSD locus. PMID:9598732

  13. Repeated Treatments with Ingenol Mebutate Prevents Progression of UV-Induced Photodamage in Hairless Mice

    PubMed Central

    Thaysen-Petersen, Daniel; Bay, Christiane; Hald, Andreas; Skak, Kresten; Zibert, John Robert; Paasch, Uwe; Wulf, Hans Christian; Haedersdal, Merete

    2016-01-01

    Background and Aim Ingenol mebutate (IngMeb) is an effective treatment for actinic keratosis. In this study, we hypothesized that repeated treatments with IngMeb may prevent progression of UV-induced photodamage, and that concurrent application of a corticosteroid may reduce IngMeb-induced local skin responses (LSR). Methods Hairless mice (n = 60; 3 groups of 20 mice) were irradiated with solar simulated ultraviolet radiation (UVR) throughout the study. Five single treatments with IngMeb were given at 4-week intervals (Days 21, 49, 77, 105, and 133). Clobetasol propionate (CP) was applied once daily for 5 days prior to each IngMeb application, as well as 6 h and 1 day post treatment. One week after IngMeb treatment No. 1, 3, and 5 (Days 28, 84, and 140), biopsies from four mice in each group were collected for histological evaluation of UV-damage on a standardized UV-damage scale (0–12). LSR (0–24) were assessed once daily (Days 1–7) after each IngMeb treatment. Results IngMeb prevented progression of photodamage in terms of keratosis grade, epidermal hypertrophy, dysplasia, and dermal actinic damage with a lower composite UV-damage score on day 140 (UVR 10.25 vs. UVR+IngMeb 6.00, p = 0.002) compared to UVR alone. IngMeb induced LSR, including erythema, flaking, crusting, bleeding, vesiculation, and ulceration. Concurrent CP increased LSR (max LSR Tx 1–5: UVR+IngMeb+CP 3.6–5.5 vs. UVR+IngMeb 2.6–4.3) and provided better prevention of photodamage compared to IngMeb alone (Day 140: UVR+IngMeb 6.00 vs. UVR+IngMeb+CP 3.00 p < 0.001). Conclusion Repeated field-directed treatments with IngMeb prevent progression of cutaneous photodamage in hairless mice, while CP cannot be used to alleviate IngMeb-induced LSR. The findings suggest that IngMeb may potentially serve as a prophylactic treatment for UV-induced tumors. PMID:27636884

  14. Reliability of solar keratosis clinical diagnosis: A prospective study.

    PubMed

    Buinauskaite, Evelina; Makstiene, Jurgita; Buinauskiene, Jurate; Valiukeviciene, Skaidra

    2015-05-01

    Usually solar keratoses (SK) are diagnosed clinically. However other diseases may clinically present as erythematous macules, papules or patches on sun-exposed areas; therefore the histopathology remains the gold standard diagnostic tool. Our study, which assessed the efficacy of photodynamic therapy (PDT), showed that one in 20 clinically diagnosed SK lesions grade I-II identified by board-certified dermatologists were rosacea and only one in 40 were malignant lesions. These findings should be considered by clinicians who treat clinically diagnosed grade I-II SK without response to treatment or diagnose the recurrence of SK after PDT.

  15. Evolutionarily divergent, unstable filamentous actin is essential for gliding motility in apicomplexan parasites.

    PubMed

    Skillman, Kristen M; Diraviyam, Karthikeyan; Khan, Asis; Tang, Keliang; Sept, David; Sibley, L David

    2011-10-01

    Apicomplexan parasites rely on a novel form of actin-based motility called gliding, which depends on parasite actin polymerization, to migrate through their hosts and invade cells. However, parasite actins are divergent both in sequence and function and only form short, unstable filaments in contrast to the stability of conventional actin filaments. The molecular basis for parasite actin filament instability and its relationship to gliding motility remain unresolved. We demonstrate that recombinant Toxoplasma (TgACTI) and Plasmodium (PfACTI and PfACTII) actins polymerized into very short filaments in vitro but were induced to form long, stable filaments by addition of equimolar levels of phalloidin. Parasite actins contain a conserved phalloidin-binding site as determined by molecular modeling and computational docking, yet vary in several residues that are predicted to impact filament stability. In particular, two residues were identified that form intermolecular contacts between different protomers in conventional actin filaments and these residues showed non-conservative differences in apicomplexan parasites. Substitution of divergent residues found in TgACTI with those from mammalian actin resulted in formation of longer, more stable filaments in vitro. Expression of these stabilized actins in T. gondii increased sensitivity to the actin-stabilizing compound jasplakinolide and disrupted normal gliding motility in the absence of treatment. These results identify the molecular basis for short, dynamic filaments in apicomplexan parasites and demonstrate that inherent instability of parasite actin filaments is a critical adaptation for gliding motility.

  16. Evolutionarily Divergent, Unstable Filamentous Actin Is Essential for Gliding Motility in Apicomplexan Parasites

    PubMed Central

    Skillman, Kristen M.; Diraviyam, Karthikeyan; Khan, Asis; Tang, Keliang; Sept, David; Sibley, L. David

    2011-01-01

    Apicomplexan parasites rely on a novel form of actin-based motility called gliding, which depends on parasite actin polymerization, to migrate through their hosts and invade cells. However, parasite actins are divergent both in sequence and function and only form short, unstable filaments in contrast to the stability of conventional actin filaments. The molecular basis for parasite actin filament instability and its relationship to gliding motility remain unresolved. We demonstrate that recombinant Toxoplasma (TgACTI) and Plasmodium (PfACTI and PfACTII) actins polymerized into very short filaments in vitro but were induced to form long, stable filaments by addition of equimolar levels of phalloidin. Parasite actins contain a conserved phalloidin-binding site as determined by molecular modeling and computational docking, yet vary in several residues that are predicted to impact filament stability. In particular, two residues were identified that form intermolecular contacts between different protomers in conventional actin filaments and these residues showed non-conservative differences in apicomplexan parasites. Substitution of divergent residues found in TgACTI with those from mammalian actin resulted in formation of longer, more stable filaments in vitro. Expression of these stabilized actins in T. gondii increased sensitivity to the actin-stabilizing compound jasplakinolide and disrupted normal gliding motility in the absence of treatment. These results identify the molecular basis for short, dynamic filaments in apicomplexan parasites and demonstrate that inherent instability of parasite actin filaments is a critical adaptation for gliding motility. PMID:21998582

  17. Role of the actin bundling protein fascin in growth cone morphogenesis: localization in filopodia and lamellipodia.

    PubMed

    Cohan, C S; Welnhofer, E A; Zhao, L; Matsumura, F; Yamashiro, S

    2001-02-01

    Growth cones at the distal tips of growing nerve axons contain bundles of actin filaments distributed throughout the lamellipodium and that project into filopodia. The regulation of actin bundling by specific actin binding proteins is likely to play an important role in many growth cone behaviors. Although the actin binding protein, fascin, has been localized in growth cones, little information is available on its functional significance. We used the large growth cones of the snail Helisoma to determine whether fascin was involved in temporal changes in actin filaments during growth cone morphogenesis. Fascin localized to radially oriented actin bundles in lamellipodia (ribs) and filopodia. Using a fascin antibody and a GFP fascin construct, we found that fascin incorporated into actin bundles from the beginning of growth cone formation at the cut end of axons. Fascin associated with most of the actin bundle except the proximal 6--12% adjacent to the central domain, which is the region associated with actin disassembly. Later, during growth cone morphogenesis when actin ribs shortened, the proximal fascin-free zone of bundles increased, but fascin was retained in the distal, filopodial portion of bundles. Treatment with tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA), which phosphorylates fascin and decreases its affinity for actin, resulted in loss of all actin bundles from growth cones. Our findings suggest that fascin may be particularly important for the linear structure and dynamics of filopodia and for lamellipodial rib dynamics by regulating filament organization in bundles.

  18. Ring closure in actin polymers

    NASA Astrophysics Data System (ADS)

    Sinha, Supurna; Chattopadhyay, Sebanti

    2017-03-01

    We present an analysis for the ring closure probability of semiflexible polymers within the pure bend Worm Like Chain (WLC) model. The ring closure probability predicted from our analysis can be tested against fluorescent actin cyclization experiments. We also discuss the effect of ring closure on bend angle fluctuations in actin polymers.

  19. Role of actin in auxin transport and transduction of gravity

    NASA Astrophysics Data System (ADS)

    Hu, S.; Basu, S.; Brady, S.; Muday, G.

    Transport of the plant hormone auxin is polar and the direction of the hormone movement appears to be controlled by asymmetric distribution of auxin transport protein complexes. Changes in the direction of auxin transport are believed to drive asymmetric growth in response to changes in the gravity vector. To test the possibility that asymmetric distribution of the auxin transport protein complex is mediated by attachment to the actin cytoskeleton, a variety of experimental approaches have been used. The most direct demonstration of the role of the actin cytoskeleton in localization of the protein complex is the ability of one protein in this complex to bind to affinity columns containing actin filaments. Additionally, treatments of plant tissues with drugs that fragment the actin c toskeleton reducey polar transport. In order to explore this actin interaction and the affect of gravity on auxin transport and developmental polarity, embryos of the brown alga, Fucus have been examined. Fucus zygotes are initially symmetrical, but develop asymmetry in response to environmental gradients, with light gradients being the best- characterized signal. Gravity will polarize these embryos and gravity-induced polarity is randomized by clinorotation. Auxin transport also appears necessary for environmental controls of polarity, since auxin efflux inhibitors perturb both photo- and gravity-polarization at a very discrete temporal window within six hours after fertilization. The actin cytoskeleton has previously been shown to reorganize after fertilization of Fucus embryos leading to formation of an actin patch at the site of polar outgrowth. These actin patches still form in Fucus embryos treated with auxin efflux inhibitors, yet the position of these patches is randomized. Together, these results suggest that there are connections between the actin cytoskeleton, auxin transport, and gravity oriented growth and development. (Supported by NASA Grant: NAG2-1203)

  20. Novel actin depolymerizing macrolide aplyronine A.

    PubMed

    Saito, S; Watabe, S; Ozaki, H; Kigoshi, H; Yamada, K; Fusetani, N; Karaki, H

    1996-09-01

    Aplyronine A is a macrolide isolated from Aplysia kurodai. By monitoring fluorescent intensity of pyrenyl-actin, it was found that aplyronine A inhibited both the velocity and the degree of actin polymerization. Aplyronine A also quickly depolymerized F-actin. The kinetics of depolymerization suggest that aplyronine A severs F-actin. The relationship between the concentration of total actin and F-actin at different concentrations of aplyronine A suggests that aplyronine A forms a 1:1 complex with G-actin. From these results, it is concluded that aplyronine A inhibits actin polymerization and depolymerizes F-actin by nibbling. Comparison of the chemical structure of aplyronine A and another actin-depolymerizing macrolide, mycalolide B, suggests that the side-chain but not the macrolide ring of aplyronine A may account for its actin binding and severing activity.

  1. Bacterial Actins and Their Interactors.

    PubMed

    Gayathri, Pananghat

    2017-01-01

    Bacterial actins polymerize in the presence of nucleotide (preferably ATP), form a common arrangement of monomeric interfaces within a protofilament, and undergo ATP hydrolysis-dependent change in stability of the filament-all of which contribute to performing their respective functions. The relative stability of the filament in the ADP-bound form compared to that of ATP and the rate of addition of monomers at the two ends decide the filament dynamics. One of the major differences between eukaryotic actin and bacterial actins is the variety in protofilament arrangements and dynamics exhibited by the latter. The filament structure and the polymerization dynamics enable them to perform various functions such as shape determination in rod-shaped bacteria (MreB), cell division (FtsA), plasmid segregation (ParM family of actin-like proteins), and organelle positioning (MamK). Though the architecture and dynamics of a few representative filaments have been studied, information on the effect of interacting partners on bacterial actin filament dynamics is not very well known. The chapter reviews some of the structural and functional aspects of bacterial actins, with special focus on the effect that interacting partners exert on the dynamics of bacterial actins, and how these assist them to carry out the functions within the bacterial cell.

  2. Keratosis follicularis spinulosa decalvans: a family study of seven male cases and six female carriers.

    PubMed Central

    van Osch, L D; Oranje, A P; Keukens, F M; van Voorst Vader, P C; Veldman, E

    1992-01-01

    Keratosis follicularis spinulosa decalvans (KFSD) is a rare X linked disease which is characterised by follicular hyperkeratosis of the skin and corneal dystrophy. Seven male patients and six female carriers are described. Special attention has been paid to the dermatological and ophthalmic markers of KFSD in patients and carriers. The most prominent features present in the male patients were follicular hyperkeratosis, hyperkeratosis of the calcaneal regions of the soles, scarring alopecia of the scalp, absence of eyebrows and eyelashes, and corneal dystrophy accompanied by photophobia. They also had high cuticles on the fingernails which has not been described before. Carriers often have dry skin, minimal follicular hyperkeratosis, and mild hyperkeratosis of the calcaneal areas of the soles. Mild corneal dystrophy without photophobia was observed in one female carrier. Images PMID:1552542

  3. Keratosis follicularis spinulosa decalvans: a family study of seven male cases and six female carriers.

    PubMed

    van Osch, L D; Oranje, A P; Keukens, F M; van Voorst Vader, P C; Veldman, E

    1992-01-01

    Keratosis follicularis spinulosa decalvans (KFSD) is a rare X linked disease which is characterised by follicular hyperkeratosis of the skin and corneal dystrophy. Seven male patients and six female carriers are described. Special attention has been paid to the dermatological and ophthalmic markers of KFSD in patients and carriers. The most prominent features present in the male patients were follicular hyperkeratosis, hyperkeratosis of the calcaneal regions of the soles, scarring alopecia of the scalp, absence of eyebrows and eyelashes, and corneal dystrophy accompanied by photophobia. They also had high cuticles on the fingernails which has not been described before. Carriers often have dry skin, minimal follicular hyperkeratosis, and mild hyperkeratosis of the calcaneal areas of the soles. Mild corneal dystrophy without photophobia was observed in one female carrier.

  4. Actin cytoskeleton: putting a CAP on actin polymerization.

    PubMed

    Stevenson, V A; Theurkauf, W E

    2000-10-05

    Two recent studies have identified a Drosophila homolog of cyclase-associated protein (CAP) as a developmentally important negative regulator of actin polymerization that may also directly mediate signal transduction.

  5. Nanosecond electric pulses trigger actin responses in plant cells

    SciTech Connect

    Berghoefer, Thomas; Eing, Christian; Flickinger, Bianca; Hohenberger, Petra; Wegner, Lars H.; Frey, Wolfgang; Nick, Peter

    2009-09-25

    We have analyzed the cellular effects of nanosecond pulsed electrical fields on plant cells using fluorescently tagged marker lines in the tobacco cell line BY-2 and confocal laser scanning microscopy. We observe a disintegration of the cytoskeleton in the cell cortex, followed by contraction of actin filaments towards the nucleus, and disintegration of the nuclear envelope. These responses are accompanied by irreversible permeabilization of the plasma membrane manifest as uptake of Trypan Blue. By pretreatment with the actin-stabilizing drug phalloidin, the detachment of transvacuolar actin from the cell periphery can be suppressed, and this treatment can also suppress the irreversible perforation of the plasma membrane. We discuss these findings in terms of a model, where nanosecond pulsed electric fields trigger actin responses that are key events in the plant-specific form of programmed cell death.

  6. Formin' actin in the nucleus.

    PubMed

    Baarlink, Christian; Grosse, Robert

    2014-01-01

    Many if not most proteins can, under certain conditions, change cellular compartments, such as, for example, shuttling from the cytoplasm to the nucleus. Thus, many proteins may exert functions in various and very different subcellular locations, depending on the signaling context. A large amount of actin regulatory proteins has been detected in the mammalian cell nucleus, although their potential roles are much debated and are just beginning to emerge. Recently, members of the formin family of actin nucleators were also reported to dynamically localize to the nuclear environment. Here we discuss our findings that specific diaphanous-related formins can promote nuclear actin assembly in a signal-dependent manner.

  7. Maleimidobenzoyl-G-actin: Structural properties and interaction with skeletal myosin subfragment-1

    SciTech Connect

    Bettache, N.; Bertrand, R.; Kassab, R. )

    1990-09-25

    The authors have investigated various structural and interaction properties of maleimidobenzoyl-G-actin (MBS-actin), a new, internally cross-linked G-actin derivative that does not exhibit, at moderate protein concentration, the salt-and myosin subfragment 1 (S-1)--induced polymerizations of G-actin and reacts reversibly and covalently in solution with S-1 at or near the F-actin binding region of the heavy chain. The far-ultraviolet CD spectrum and {alpha}-helix content of the MBS-actin were identical with those displayed by native G-actin. {sup 45}Ca{sup 2+} measurements showed the same content of tightly bound Ca{sup 2+} in MBS-actin as in G-actin and the EDTA treatment of the modified protein promoted the same red shift of the intrinsic fluorescence spectrum as observed with native G-actin. Incubation of concentrated MBS-actin solutions with 100 mM KCl+5 mM MgCl{sub 2} led to the polymerization of the actin derivative when the critical monomer concentration reached 1.6mg/mL, at 25{degree}C, pH 8.0. The MBS-F-actin formed activated the Mg{sup 2+}-ATPase of S-1 to the same extent as native F-actin. The MBS-G-actin exhibited a DNase I inhibitor activity very close to that found with native G-actin and was to be at all affected by its specific covalent conjugation to S-1. This finding led them to isolate, for the first time, by gel filtration, a ternary complex comprising DNase I tightly bound to MBS-actin cross-linked to the S-1 heavy chain, demonstrating that S-1 and DNase I bind at distinct sites on G-actin. Collectively, the data illustrate further the nativeness of the MBS-G-actin and its potential use in solution studies of the actin-myosin head interactions.

  8. Seborrheic keratosis

    MedlinePlus

    ... Tumor Review Date 11/14/2014 Updated by: Richard J. Moskowitz, MD, Dermatologist in private practice, Mineola, ... commercial use must be authorized in writing by ADAM Health Solutions. About MedlinePlus Site Map FAQs Customer ...

  9. Keratosis pilaris

    MedlinePlus

    ... very dry skin, or who have atopic dermatitis (eczema). The condition is generally worse in winter and ... A.M. Editorial team. Related MedlinePlus Health Topics Eczema Skin Conditions Browse the Encyclopedia A.D.A. ...

  10. Actin dynamics and cofilin-actin rods in Alzheimer disease

    PubMed Central

    Bamburg, James R.; Bernstein, Barbara W.

    2017-01-01

    Cytoskeletal abnormalities and synaptic loss, typical of both familial and sporadic Alzheimer disease (AD), are induced by diverse stresses such as neuroinflammation, oxidative stress, and energetic stress, each of which may be initiated or enhanced by proinflammatory cytokines or amyloid-β (Aβ) peptides. Extracellular Aβ-containing plaques and intracellular phospho-tau-containing neurofibrillary tangles are postmortem pathologies required to confirm AD and have been the focus of most studies. However, AD brain, but not normal brain, also have increased levels of cytoplasmic rod-shaped bundles of filaments composed of ADF/cofilin-actin in a 1:1 complex (rods). Cofilin, the major ADF/cofilin isoform in mammalian neurons, severs actin filaments at low cofilin/actin ratios and stabilizes filaments at high cofilin/actin ratios. It binds cooperatively to ADP-actin subunits in F-actin. Cofilin is activated by dephosphorylation and may be oxidized in stressed neurons to form disulfide-linked dimers, required for bundling cofilin-actin filaments into stable rods. Rods form within neurites causing synaptic dysfunction by sequestering cofilin, disrupting normal actin dynamics, blocking transport, and exacerbating mitochondrial membrane potential loss. Aβ and proinflammatory cytokines induce rods through a cellular prion protein-dependent activation of NADPH oxidase and production of reactive oxygen species. Here we review recent advances in our understanding of cofilin biochemistry, rod formation, and the development of cognitive deficits. We will then discuss rod formation as a molecular pathway for synapse loss that may be common between all three prominent current AD hypotheses, thus making rods an attractive therapeutic target. PMID:26873625

  11. Stochastic dynamics of actin filaments in guard cells regulating chloroplast localization during stomatal movement.

    PubMed

    Wang, Xiu-Ling; Gao, Xin-Qi; Wang, Xue-Chen

    2011-08-01

    Actin filaments and chloroplasts in guard cells play roles in stomatal function. However, detailed actin dynamics vary, and the roles that they play in chloroplast localization during stomatal movement remain to be determined. We examined the dynamics of actin filaments and chloroplast localization in transgenic tobacco expressing green fluorescent protein (GFP)-mouse talin in guard cells by time-lapse imaging. Actin filaments showed sliding, bundling and branching dynamics in moving guard cells. During stomatal movement, long filaments can be severed into small fragments, which can form longer filaments by end-joining activities. With chloroplast movement, actin filaments near chloroplasts showed severing and elongation activity in guard cells during stomatal movement. Cytochalasin B treatment abolished elongation, bundling and branching activities of actin filaments in guard cells, and these changes of actin filaments, and as a result, more chloroplasts were localized at the centre of guard cells. However, chloroplast turning to avoid high light, and sliding of actin fragments near the chloroplast, was unaffected following cytochalasin B treatment in guard cells. We suggest that the sliding dynamics of actin may play roles in chloroplast turning in guard cells. Our results indicate that the stochastic dynamics of actin filaments in guard cells regulate chloroplast localization during stomatal movement.

  12. Formaldehyde fixation is detrimental to actin cables in glucose-depleted S. cerevisiae cells

    PubMed Central

    Vasicova, Pavla; Rinnerthaler, Mark; Haskova, Danusa; Novakova, Lenka; Malcova, Ivana; Breitenbach, Michael; Hasek, Jiri

    2016-01-01

    Actin filaments form cortical patches and emanating cables in fermenting cells of Saccharomyces cerevisiae. This pattern has been shown to be depolarized in glucose-depleted cells after formaldehyde fixation and staining with rhodamine-tagged phalloidin. Loss of actin cables in mother cells was remarkable. Here we extend our knowledge on actin in live glucose-depleted cells co-expressing the marker of actin patches (Abp1-RFP) with the marker of actin cables (Abp140-GFP). Glucose depletion resulted in appearance of actin patches also in mother cells. However, even after 80 min of glucose deprivation these cells showed a clear network of actin cables labeled with Abp140-GFP in contrast to previously published data. In live cells with a mitochondrial dysfunction (rho0 cells), glucose depletion resulted in almost immediate appearance of Abp140-GFP foci partially overlapping with Abp1-RFP patches in mother cells. Residual actin cables were clustered in patch-associated bundles. A similar overlapping “patchy” pattern of both actin markers was observed upon treatment of glucose-deprived rho+ cells with FCCP (the inhibitor of oxidative phosphorylation) and upon treatment with formaldehyde. While the formaldehyde-targeted process stays unknown, our results indicate that published data on yeast actin cytoskeleton obtained from glucose-depleted cells after fixation should be considered with caution.

  13. Chemotaxis and Actin Oscillations

    NASA Astrophysics Data System (ADS)

    Bodenschatz, Eberhard; Hsu, Hsin-Fang; Negrete, Jose; Beta, Carsten; Pumir, Alain; Gholami, Azam; Tarantola, Marco; Westendorf, Christian; Zykov, Vladimir

    Recently, self-oscillations of the cytoskeletal actin have been observed in Dictyostelium, a model system for studying chemotaxis. Here we report experimental results on the self-oscillation mechanism and the role of regulatory proteins and myosin II. We stimulate cells rapidly and periodically by using photo un-caging of the chemoattractant in a micro-fluidic device and measured the cellular responses. We found that the response amplitude grows with stimulation strength only in a very narrow region of stimulation, after which the response amplitude reaches a plateau. Moreover, the frequency-response is not constant but rather varies with the strength of external stimuli. To understand the underlying mechanism, we analyzed the polymerization and de-polymerization time in the single cell level. Despite of the large cell-to-cell variability, we found that the polymerization time is independent of external stimuli and the de-polymerization time is prolonged as the stimulation strength increases. Our conclusions will be summarized and the role of noise in the signaling network will be discussed. German Science Foundation CRC 937.

  14. Rho GTPases, phosphoinositides, and actin

    PubMed Central

    Croisé, Pauline; Estay-Ahumada, Catherine; Gasman, Stéphane; Ory, Stéphane

    2014-01-01

    Rho GTPases are well known regulators of the actin cytoskeleton that act by binding and activating actin nucleators. They are therefore involved in many actin-based processes, including cell migration, cell polarity, and membrane trafficking. With the identification of phosphoinositide kinases and phosphatases as potential binding partners or effectors, Rho GTPases also appear to participate in the regulation of phosphoinositide metabolism. Since both actin dynamics and phosphoinositide turnover affect the efficiency and the fidelity of vesicle transport between cell compartments, Rho GTPases have emerged as critical players in membrane trafficking. Rho GTPase activity, actin remodeling, and phosphoinositide metabolism need to be coordinated in both space and time to ensure the progression of vesicles along membrane trafficking pathways. Although most molecular pathways are still unclear, in this review, we will highlight recent advances made in our understanding of how Rho-dependent signaling pathways organize actin dynamics and phosphoinositides and how phosphoinositides potentially provide negative feedback to Rho GTPases during endocytosis, exocytosis and membrane exchange between intracellular compartments. PMID:24914539

  15. Fluorescence Guided PDT for Optimization of Skin Cancer Treatment

    NASA Astrophysics Data System (ADS)

    Blanco, Kate; Moriyama, Lilian; Inada, Natalia; Kurachi, Cristina; Salvio, Ana; Leite, Everson; Menezes, Priscila; Bagnato, Vanderlei

    2015-04-01

    The photodynamic therapy (PDT) is an alternative technique that can be indicated for superficial basal cell carcinoma (sBCC), Bowen’s disease and actinic keratosis with high efficiency. The objective of this study is to present the importance of fluorescence imaging for PDT guidance and monitoring in real time. Confirming that the lesion is well prepared and the photosensitizer shows a homogenous distribution, the outcome after few PDT sessions will be positive and the recurrence should be lower. Our proposition in this study is use the widefield fluorescence imaging to evaluate the PDT protocol in situ and in real time for each lesion. This evaluation procedure is performed in two steps: first with the monitoring of the production of protoporphyrin IX (PpIX) induced by methyl aminolevulinate (MAL), an derivative of 5-aminolevulinic acid (ALA) and second with the detection of PpIX photobleaching after illumination. The fluorescence images provide information correlated with distinct clinical features and with the treatment outcome. Eight BCC lesions are presented and discussed in this study. Different fluorescence patterns of PpIX production and photobleaching could be correlated with the treatment response. The presented results show the potential of using widefield fluorescence imaging as a guidance tool to customized PDT.

  16. In Vivo Imaging and Characterization of Actin Microridges

    PubMed Central

    Lam, Pui-ying; Mangos, Steve; Green, Julie M.; Reiser, Jochen; Huttenlocher, Anna

    2015-01-01

    Actin microridges form labyrinth like patterns on superficial epithelial cells across animal species. This highly organized assembly has been implicated in mucus retention and in the mechanical structure of mucosal surfaces, however the mechanisms that regulate actin microridges remain largely unknown. Here we characterize the composition and dynamics of actin microridges on the surface of zebrafish larvae using live imaging. Microridges contain phospho-tyrosine, cortactin and VASP, but not focal adhesion kinase. Time-lapse imaging reveals dynamic changes in the length and branching of microridges in intact animals. Transient perturbation of the microridge pattern occurs before cell division with rapid re-assembly during and after cytokinesis. Microridge assembly is maintained with constitutive activation of Rho or inhibition of myosin II activity. However, expression of dominant negative RhoA or Rac alters microridge organization, with an increase in distance between microridges. Latrunculin A treatment and photoconversion experiments suggest that the F-actin filaments are actively treadmilling in microridges. Accordingly, inhibition of Arp2/3 or PI3K signaling impairs microridge structure and length. Taken together, actin microridges in zebrafish represent a tractable in vivo model to probe pattern formation and dissect Arp2/3-mediated actin dynamics in vivo. PMID:25629723

  17. The Role of Actin Cytoskeleton in Memory Formation in Amygdala

    PubMed Central

    Lamprecht, Raphael

    2016-01-01

    The central, lateral and basolateral amygdala (BLA) nuclei are essential for the formation of long-term memories including emotional and drug-related memories. Studying cellular and molecular mechanisms of memory in amygdala may lead to better understanding of how memory is formed and of fear and addiction-related disorders. A challenge is to identify molecules activated by learning that subserve cellular changes needed for memory formation and maintenance in amygdala. Recent studies show that activation of synaptic receptors during fear and drug-related learning leads to alteration in actin cytoskeleton dynamics and structure in amygdala. Such changes in actin cytoskeleton in amygdala are essential for fear and drug-related memories formation. Moreover, the actin cytoskeleton subserves, after learning, changes in neuronal morphogenesis and glutamate receptors trafficking in amygdala. These cellular events are involved in fear and drug-related memories formation. Actin polymerization is also needed for the maintenance of drug-associated memories in amygdala. Thus, the actin cytoskeleton is a key mediator between receptor activation during learning and cellular changes subserving long-term memory (LTM) in amygdala. The actin cytoskeleton may serve as a target for pharmacological treatment of fear memory associated with fear and anxiety disorders and drug addiction to prevent the debilitating consequences of these diseases. PMID:27065800

  18. Cofilin-mediated actin dynamics promotes actin bundle formation during Drosophila bristle development

    PubMed Central

    Wu, Jing; Wang, Heng; Guo, Xuan; Chen, Jiong

    2016-01-01

    The actin bundle is an array of linear actin filaments cross-linked by actin-bundling proteins, but its assembly and dynamics are not as well understood as those of the branched actin network. Here we used the Drosophila bristle as a model system to study actin bundle formation. We found that cofilin, a major actin disassembly factor of the branched actin network, promotes the formation and positioning of actin bundles in the developing bristles. Loss of function of cofilin or AIP1, a cofactor of cofilin, each resulted in increased F-actin levels and severe defects in actin bundle organization, with the defects from cofilin deficiency being more severe. Further analyses revealed that cofilin likely regulates actin bundle formation and positioning by the following means. First, cofilin promotes a large G-actin pool both locally and globally, likely ensuring rapid actin polymerization for bundle initiation and growth. Second, cofilin limits the size of a nonbundled actin-myosin network to regulate the positioning of actin bundles. Third, cofilin prevents incorrect assembly of branched and myosin-associated actin filament into bundles. Together these results demonstrate that the interaction between the dynamic dendritic actin network and the assembling actin bundles is critical for actin bundle formation and needs to be closely regulated. PMID:27385345

  19. Possible association of actin filaments with chloroplasts of spinach mesophyll cells in vivo and in vitro.

    PubMed

    Kumatani, T; Sakurai-Ozato, N; Miyawaki, N; Yokota, E; Shimmen, T; Terashima, I; Takagi, S

    2006-11-01

    In palisade mesophyll cells of spinach (Spinacia oleracea L.) kept under low-intensity white light, chloroplasts were apparently immobile and seemed to be surrounded by fine bundles of actin filaments. High-intensity blue light induced actin-dependent chloroplast movement concomitant with the appearance of a couple of long, straight bundles of actin filaments in each cell, whereas high-intensity red light was essentially ineffective in inducing these responses. The actin organization observed under low-intensity white light has been postulated to function in anchoring chloroplasts at proper intracellular positions through direct interaction with the chloroplasts. Intact chloroplasts, which retained their outer envelopes, were isolated after homogenization of leaves and Percoll centrifugation. No endogenous actin was detected by immunoblotting in the final intact-chloroplast fraction prepared from the leaves kept under low-intensity white light or in darkness. In cosedimentation assays with exogenously added skeletal muscle filamentous actin, however, actin was detected in the intact-chloroplast fraction precipitated after low-speed centrifugation. The association of actin with chloroplasts was apparently dependent on incubation time and chloroplast density. After partial disruption of the outer envelope of isolated chloroplasts by treatment with trypsin, actin was no longer coprecipitated. The results suggest that chloroplasts in spinach leaves can directly interact with actin, and that this interaction may be involved in the regulation of intracellular positioning of chloroplasts.

  20. Xenopus oocyte wound healing as a model system for analysis of microtubule-actin interactions.

    PubMed

    Zhang, Tong; Mandato, Craig A

    2007-01-01

    Microtubule-actin interactions are fundamental to many cellular processes such as cytokinesis and cellular locomotion. Investigating the mechanism of microtubule-actin interactions is the key to understand the cellular morphogenesis and related pathological processes. The abundance and highly dynamic nature of microtubules and F-actin raise a serious challenge when trying to distinguish between the real and fortuitous interactions within a cell. Xenopus oocyte wound model represents an ideal system to study microtubule-actin interactions as well as microtubule-dependent control of the actin polymerization. Here, we describe a series of cytoskeleton specific treatments in Xenopus oocyte wound healing experiments and use confocal fluorescence microscopy to analyze fixed oocytes to examine microtubule-actin interactions.

  1. Boolean gates on actin filaments

    NASA Astrophysics Data System (ADS)

    Siccardi, Stefano; Tuszynski, Jack A.; Adamatzky, Andrew

    2016-01-01

    Actin is a globular protein which forms long polar filaments in the eukaryotic cytoskeleton. Actin networks play a key role in cell mechanics and cell motility. They have also been implicated in information transmission and processing, memory and learning in neuronal cells. The actin filaments have been shown to support propagation of voltage pulses. Here we apply a coupled nonlinear transmission line model of actin filaments to study interactions between voltage pulses. To represent digital information we assign a logical TRUTH value to the presence of a voltage pulse in a given location of the actin filament, and FALSE to the pulse's absence, so that information flows along the filament with pulse transmission. When two pulses, representing Boolean values of input variables, interact, then they can facilitate or inhibit further propagation of each other. We explore this phenomenon to construct Boolean logical gates and a one-bit half-adder with interacting voltage pulses. We discuss implications of these findings on cellular process and technological applications.

  2. Technical advance: identification of plant actin-binding proteins by F-actin affinity chromatography

    NASA Technical Reports Server (NTRS)

    Hu, S.; Brady, S. R.; Kovar, D. R.; Staiger, C. J.; Clark, G. B.; Roux, S. J.; Muday, G. K.

    2000-01-01

    Proteins that interact with the actin cytoskeleton often modulate the dynamics or organization of the cytoskeleton or use the cytoskeleton to control their localization. In plants, very few actin-binding proteins have been identified and most are thought to modulate cytoskeleton function. To identify actin-binding proteins that are unique to plants, the development of new biochemical procedures will be critical. Affinity columns using actin monomers (globular actin, G-actin) or actin filaments (filamentous actin, F-actin) have been used to identify actin-binding proteins from a wide variety of organisms. Monomeric actin from zucchini (Cucurbita pepo L.) hypocotyl tissue was purified to electrophoretic homogeneity and shown to be native and competent for polymerization to actin filaments. G-actin, F-actin and bovine serum albumin affinity columns were prepared and used to separate samples enriched in either soluble or membrane-associated actin-binding proteins. Extracts of soluble actin-binding proteins yield distinct patterns when eluted from the G-actin and F-actin columns, respectively, leading to the identification of a putative F-actin-binding protein of approximately 40 kDa. When plasma membrane-associated proteins were applied to these columns, two abundant polypeptides eluted selectively from the F-actin column and cross-reacted with antiserum against pea annexins. Additionally, a protein that binds auxin transport inhibitors, the naphthylphthalamic acid binding protein, which has been previously suggested to associate with the actin cytoskeleton, was eluted in a single peak from the F-actin column. These experiments provide a new approach that may help to identify novel actin-binding proteins from plants.

  3. Viral infectivity and intracellular distribution of matrix (M) protein of canine distemper virus are affected by actin filaments.

    PubMed

    Klauschies, F; Gützkow, T; Hinkelmann, S; von Messling, V; Vaske, B; Herrler, G; Haas, L

    2010-09-01

    To investigate the role of cytoskeletal components in canine distemper virus (CDV) replication, various agents were used that interfere with turnover of actin filaments and microtubules. Only inhibition of actin filaments significantly reduced viral infectivity. Analysis of the intracellular localization of the viral matrix (M) protein revealed that it aligned along actin filaments. Treatment with actin filament-disrupting drugs led to a marked intracellular redistribution of M protein during infection as well as transfection. In contrast, the localization of the CDV fusion (F) protein was not significantly changed during transfection. Thus, a M protein-actin filament interaction appears to be important for generation of infectious CDV.

  4. Profilin-Dependent Nucleation and Assembly of Actin Filaments Controls Cell Elongation in Arabidopsis1[OPEN

    PubMed Central

    Cao, Lingyan; Blanchoin, Laurent; Staiger, Christopher J.

    2016-01-01

    Actin filaments in plant cells are incredibly dynamic; they undergo incessant remodeling and assembly or disassembly within seconds. These dynamic events are choreographed by a plethora of actin-binding proteins, but the exact mechanisms are poorly understood. Here, we dissect the contribution of Arabidopsis (Arabidopsis thaliana) PROFILIN1 (PRF1), a conserved actin monomer-binding protein, to actin organization and single filament dynamics during axial cell expansion of living epidermal cells. We found that reduced PRF1 levels enhanced cell and organ growth. Surprisingly, we observed that the overall frequency of nucleation events in prf1 mutants was dramatically decreased and that a subpopulation of actin filaments that assemble at high rates was reduced. To test whether profilin cooperates with plant formin proteins to execute actin nucleation and rapid filament elongation in cells, we used a pharmacological approach. Here, we used Small Molecule Inhibitor of Formin FH2 (SMIFH2), after validating its mode of action on a plant formin in vitro, and observed a reduced nucleation frequency of actin filaments in live cells. Treatment of wild-type epidermal cells with SMIFH2 mimicked the phenotype of prf1 mutants, and the nucleation frequency in prf1-2 mutant was completely insensitive to these treatments. Our data provide compelling evidence that PRF1 coordinates the stochastic dynamic properties of actin filaments by modulating formin-mediated actin nucleation and assembly during plant cell expansion. PMID:26574597

  5. The Actin Cytoskeleton as a Therapeutic Target for the Prevention of Relapse to Methamphetamine Use.

    PubMed

    Young, Erica J; Briggs, Sherri B; Miller, Courtney A

    2015-01-01

    A high rate of relapse is a defining characteristic of substance use disorder for which few treatments are available. Exposure to environmental cues associated with previous drug use can elicit relapse by causing the involuntary retrieval of deeply engrained associative memories that trigger a strong motivation to seek out drugs. Our lab is focused on identifying and disrupting mechanisms that support these powerful consolidated memories, with the goal of developing therapeutics. A particularly promising mechanism is regulation of synaptic dynamics by actin polymerization within dendritic spines. Emerging evidence indicates that memory is supported by structural and functional plasticity dendritic spines, for which actin polymerization is critical, and that prior drug use increases both spine and actin dynamics. Indeed we have found that inhibiting amygdala (AMY) actin polymerization immediately or twenty-four hours prior to testing disrupted methamphetamine (METH)-associated memories, but not food reward or fear memories. Furthermore, METH training increased AMY spine density which was reversed by actin depolymerization treatment. Actin dynamics were also shifted to a more dynamic state by METH training. While promising, actin polymerization inhibitors are not a viable therapeutic, as a multitude of peripheral process (e.g. cardiac function) rely on dynamic actin. For this reason, we have shifted our focus upstream of actin polymerization to nonmuscle myosin II. We and others have demonstrated that myosin IIb imparts a mechanical force that triggers spine actin polymerization in response to synaptic stimulation. Similar to an actin depolymerizing compound, pre-test inhibition of myosin II ATPase activity in the AMY produced a rapid and lasting disruption of drug-seeking behavior. While many questions remain, these findings indicate that myosin II represents a potential therapeutic avenue to target the actin cytoskeleton and disrupt the powerful, extinction

  6. Bacterial Actins? An Evolutionary Perspective

    NASA Technical Reports Server (NTRS)

    Doolittle, Russell F.; York, Amanda L.

    2003-01-01

    According to the conventional wisdom, the existence of a cytoskeleton in eukaryotes and its absence in prokaryotes constitute a fundamental divide between the two domains of life. An integral part of the dogma is that a cytoskeleton enabled an early eukaryote to feed upon prokaryotes, a consequence of which was the occasional endosymbiosis and the eventual evolution of organelles. Two recent papers present compelling evidence that actin, one of the principal components of a cytoskeleton, has a homolog in Bacteria that behaves in many ways like eukaryotic actin. Sequence comparisons reveml that eukaryotic actin and the bacterial homolog (mreB protein), unlike many other proteins common to eukaryotes and Bacteria, have very different and more highly extended evolutionary histories.

  7. Photodynamic therapy using light-emitting diodes for the treatment of viral warts.

    PubMed

    Ohtsuki, Akiko; Hasegawa, Toshio; Hirasawa, Yusuke; Tsuchihashi, Hitoshi; Ikeda, Shigaku

    2009-10-01

    Photodynamic therapy with topical 5-aminolevulinic acid is an effective and safe treatment for actinic keratosis and superficial non-melanoma skin cancer. Further, some studies have reported good efficacy when using photodynamic therapy to treat viral warts. The light-emitting diode is an incoherent, narrow-spectrum light source. The purpose of this study is to evaluate the efficacy of photodynamic therapy using a light-emitting diode for viral warts. Six patients with a total of 41 foot and hand warts were recruited in this study. They were treated with 20% 5-aminolevulinic acid cream under occlusion for 5 h. Thereafter, the treated area was irradiated with the light from a red light-emitting diode (633 +/- 6 nm) with a dose of 126 J/cm(2). This treatment was repeated at 2- or 3-week intervals. The rate of improvement observed in patients was 68.3%. The adverse effects included mild to moderate pain and erythema, which was well-tolerated by all six patients. No patients withdrew from the study due to the adverse effects. Photodynamic therapy with topical 5-aminolevulinic acid using the light from a red light-emitting diode has the advantage of non-invasiveness, minimal associated adverse reactions, and production of good results in a significant proportion of cases: therefore, it is an alternative treatment for recalcitrant viral warts.

  8. Formation of long and winding nuclear F-actin bundles by nuclear c-Abl tyrosine kinase

    SciTech Connect

    Aoyama, Kazumasa; Yuki, Ryuzaburo; Horiike, Yasuyoshi; Kubota, Sho; Yamaguchi, Noritaka; Morii, Mariko; Ishibashi, Kenichi; Nakayama, Yuji; Kuga, Takahisa; Hashimoto, Yuuki; Tomonaga, Takeshi; Yamaguchi, Naoto

    2013-12-10

    The non-receptor-type tyrosine kinase c-Abl is involved in actin dynamics in the cytoplasm. Having three nuclear localization signals (NLSs) and one nuclear export signal, c-Abl shuttles between the nucleus and the cytoplasm. Although monomeric actin and filamentous actin (F-actin) are present in the nucleus, little is known about the relationship between c-Abl and nuclear actin dynamics. Here, we show that nuclear-localized c-Abl induces nuclear F-actin formation. Adriamycin-induced DNA damage together with leptomycin B treatment accumulates c-Abl into the nucleus and increases the levels of nuclear F-actin. Treatment of c-Abl-knockdown cells with Adriamycin and leptomycin B barely increases the nuclear F-actin levels. Expression of nuclear-targeted c-Abl (NLS-c-Abl) increases the levels of nuclear F-actin even without Adriamycin, and the increased levels of nuclear F-actin are not inhibited by inactivation of Abl kinase activity. Intriguingly, expression of NLS-c-Abl induces the formation of long and winding bundles of F-actin within the nucleus in a c-Abl kinase activity-dependent manner. Furthermore, NLS-c-AblΔC, which lacks the actin-binding domain but has the full tyrosine kinase activity, is incapable of forming nuclear F-actin and in particular long and winding nuclear F-actin bundles. These results suggest that nuclear c-Abl plays critical roles in actin dynamics within the nucleus. - Highlights: • We show the involvement of c-Abl tyrosine kinase in nuclear actin dynamics. • Nuclear F-actin is formed by nuclear-localized c-Abl and its kinase-dead version. • The c-Abl actin-binding domain is prerequisite for nuclear F-actin formation. • Formation of long nuclear F-actin bundles requires nuclear c-Abl kinase activity. • We discuss a role for nuclear F-actin bundle formation in chromatin regulation.

  9. Actin polymerization is stimulated by actin cross-linking protein palladin.

    PubMed

    Gurung, Ritu; Yadav, Rahul; Brungardt, Joseph G; Orlova, Albina; Egelman, Edward H; Beck, Moriah R

    2016-02-15

    The actin scaffold protein palladin regulates both normal cell migration and invasive cell motility, processes that require the co-ordinated regulation of actin dynamics. However, the potential effect of palladin on actin dynamics has remained elusive. In the present study, we show that the actin-binding immunoglobulin-like domain of palladin, which is directly responsible for both actin binding and bundling, also stimulates actin polymerization in vitro. Palladin eliminated the lag phase that is characteristic of the slow nucleation step of actin polymerization. Furthermore, palladin dramatically reduced depolymerization, slightly enhanced the elongation rate, and did not alter the critical concentration. Microscopy and in vitro cross-linking assays reveal differences in actin bundle architecture when palladin is incubated with actin before or after polymerization. These results suggest a model whereby palladin stimulates a polymerization-competent form of globular or monomeric actin (G-actin), akin to metal ions, either through charge neutralization or through conformational changes.

  10. Formation and Destabilization of Actin Filaments with Tetramethylrhodamine-Modified Actin

    PubMed Central

    Kudryashov, Dmitry S.; Phillips, Martin; Reisler, Emil

    2004-01-01

    Actin labeling at Cys374 with tethramethylrhodamine derivatives (TMR-actin) has been widely used for direct observation of the in vitro filaments growth, branching, and treadmilling, as well as for the in vivo visualization of actin cytoskeleton. The advantage of TMR-actin is that it does not lock actin in filaments (as rhodamine-phalloidin does), possibly allowing for its use in investigating the dynamic assembly behavior of actin polymers. Although it is established that TMR-actin alone is polymerization incompetent, the impact of its copolymerization with unlabeled actin on filament structure and dynamics has not been tested yet. In this study, we show that TMR-actin perturbs the filaments structure when copolymerized with unlabeled actin; the resulting filaments are more fragile and shorter than the control filaments. Due to the increased severing of copolymer filaments, TMR-actin accelerates the polymerization of unlabeled actin in solution also at mole ratios lower than those used in most fluorescence microscopy experiments. The destabilizing and severing effect of TMR-actin is countered by filament stabilizing factors, phalloidin, S1, and tropomyosin. These results point to an analogy between the effects of TMR-actin and severing proteins on F-actin, and imply that TMR-actin may be inappropriate for investigations of actin filaments dynamics. PMID:15298916

  11. Comparisons of Endothelial Cell G- and F-Actin Distribution in Situ and in Vitro

    DTIC Science & Technology

    1993-01-01

    treatment (Fig. 3D) indicated Bottaro, D)., Shepro. D., Peterson. S. and flechtman. H. 13. 1986. Serotonin , norepinephrine and his-that the F-actin of...Correlation among endothelial cell shape. D does niot produce net depolyrmcrization of ac- F-actin arrAngement and prostacyclin synthe - tin

  12. Fascin regulates nuclear actin during Drosophila oogenesis

    PubMed Central

    Kelpsch, Daniel J.; Groen, Christopher M.; Fagan, Tiffany N.; Sudhir, Sweta; Tootle, Tina L.

    2016-01-01

    Drosophila oogenesis provides a developmental system with which to study nuclear actin. During Stages 5–9, nuclear actin levels are high in the oocyte and exhibit variation within the nurse cells. Cofilin and Profilin, which regulate the nuclear import and export of actin, also localize to the nuclei. Expression of GFP-tagged Actin results in nuclear actin rod formation. These findings indicate that nuclear actin must be tightly regulated during oogenesis. One factor mediating this regulation is Fascin. Overexpression of Fascin enhances nuclear GFP-Actin rod formation, and Fascin colocalizes with the rods. Loss of Fascin reduces, whereas overexpression of Fascin increases, the frequency of nurse cells with high levels of nuclear actin, but neither alters the overall nuclear level of actin within the ovary. These data suggest that Fascin regulates the ability of specific cells to accumulate nuclear actin. Evidence indicates that Fascin positively regulates nuclear actin through Cofilin. Loss of Fascin results in decreased nuclear Cofilin. In addition, Fascin and Cofilin genetically interact, as double heterozygotes exhibit a reduction in the number of nurse cells with high nuclear actin levels. These findings are likely applicable beyond Drosophila follicle development, as the localization and functions of Fascin and the mechanisms regulating nuclear actin are widely conserved. PMID:27535426

  13. Differentiation of hidroacanthoma simplex from clonal seborrheic keratosis--an immunohistochemical study.

    PubMed

    Liu, Han-Nan; Chang, Yun-Ting; Chen, Chih-Chiang

    2004-06-01

    Hidroacanthoma simplex (HS) is an uncommon poroid neoplasm confined within the epidermis. The clinical features of HS are not distinctive and histopathologically HS may be confused with clonal seborrheic keratosis (CSK) if cystic or ductal structure is not present. The purpose of our study was to differentiate HS from CSK by the immunohistochemical expressions of various cytokeratins, CEA, CD1a, and S-100 protein, as well as by the degrees of deposition of melanins and glycogen. Four cases of HS and seven cases of CSK were included in the research. In contrast with CSK, HS showed a very low density of Langerhans cells (19.9 +/- 7.7 versus 3.1 +/- 1.0 CD1a (+) cells/mm, P = 0.027) and sparse melanin deposition in the nests. However, HS could not be set apart from CSK by the expressions of cytokeratins. The nests of both HS and CSK showed very similar patterns of cytokeratin expression and seemed to be mainly composed of basaloid cells with focal differentiation toward epidermal suprabasal cells.

  14. Sebaceous gland, hair shaft, and epidermal barrier abnormalities in keratosis pilaris with and without filaggrin deficiency.

    PubMed

    Gruber, Robert; Sugarman, Jeffrey L; Crumrine, Debra; Hupe, Melanie; Mauro, Theodora M; Mauldin, Elizabeth A; Thyssen, Jacob P; Brandner, Johanna M; Hennies, Hans-Christian; Schmuth, Matthias; Elias, Peter M

    2015-04-01

    Although keratosis pilaris (KP) is common, its etiopathogenesis remains unknown. KP is associated clinically with ichthyosis vulgaris and atopic dermatitis and molecular genetically with filaggrin-null mutations. In 20 KP patients and 20 matched controls, we assessed the filaggrin and claudin 1 genotypes, the phenotypes by dermatoscopy, and the morphology by light and transmission electron microscopy. Thirty-five percent of KP patients displayed filaggrin mutations, demonstrating that filaggrin mutations only partially account for the KP phenotype. Major histologic and dermatoscopic findings of KP were hyperkeratosis, hypergranulosis, mild T helper cell type 1-dominant lymphocytic inflammation, plugging of follicular orifices, striking absence of sebaceous glands, and hair shaft abnormalities in KP lesions but not in unaffected skin sites. Changes in barrier function and abnormal paracellular permeability were found in both interfollicular and follicular stratum corneum of lesional KP, which correlated ultrastructurally with impaired extracellular lamellar bilayer maturation and organization. All these features were independent of filaggrin genotype. Moreover, ultrastructure of corneodesmosomes and tight junctions appeared normal, immunohistochemistry for claudin 1 showed no reduction in protein amounts, and molecular analysis of claudin 1 was unremarkable. Our findings suggest that absence of sebaceous glands is an early step in KP pathogenesis, resulting in downstream hair shaft and epithelial barrier abnormalities.

  15. Sebaceous Gland, Hair Shaft, and Epidermal Barrier Abnormalities in Keratosis Pilaris with and without Filaggrin Deficiency

    PubMed Central

    Gruber, Robert; Sugarman, Jeffrey L.; Crumrine, Debra; Hupe, Melanie; Mauro, Theodora M.; Mauldin, Elizabeth A.; Thyssen, Jacob P.; Brandner, Johanna M.; Hennies, Hans-Christian; Schmuth, Matthias; Elias, Peter M.

    2016-01-01

    Although keratosis pilaris (KP) is common, its etiopathogenesis remains unknown. KP is associated clinically with ichthyosis vulgaris and atopic dermatitis and molecular genetically with filaggrin-null mutations. In 20 KP patients and 20 matched controls, we assessed the filaggrin and claudin 1 genotypes, the phenotypes by dermatoscopy, and the morphology by light and transmission electron microscopy. Thirty-five percent of KP patients displayed filaggrin mutations, demonstrating that filaggrin mutations only partially account for the KP phenotype. Major histologic and dermatoscopic findings of KP were hyperkeratosis, hypergranulosis, mild T helper cell type 1-dominant lymphocytic inflammation, plugging of follicular orifices, striking absence of sebaceous glands, and hair shaft abnormalities in KP lesions but not in unaffected skin sites. Changes in barrier function and abnormal paracellular permeability were found in both interfollicular and follicular stratum corneum of lesional KP, which correlated ultrastructurally with impaired extracellular lamellar bilayer maturation and organization. All these features were independent of filaggrin genotype. Moreover, ultrastructure of corneodesmosomes and tight junctions appeared normal, immunohistochemistry for claudin 1 showed no reduction in protein amounts, and molecular analysis of claudin 1 was unremarkable. Our findings suggest that absence of sebaceous glands is an early step in KP pathogenesis, resulting in downstream hair shaft and epithelial barrier abnormalities. PMID:25660180

  16. Keratosis Follicularis Spinulosa Decalvans is caused by mutations in MBTPS2.

    PubMed

    Aten, Emmelien; Brasz, Lisa C; Bornholdt, Dorothea; Hooijkaas, Ingeborg B; Porteous, Mary E; Sybert, Virginia P; Vermeer, Maarten H; Vossen, Rolf H A M; van der Wielen, Michiel J R; Bakker, Egbert; Breuning, Martijn H; Grzeschik, Karl-Heinz; Oosterwijk, Jan C; den Dunnen, Johan T

    2010-10-01

    Keratosis Follicularis Spinulosa Decalvans (KFSD) is a rare genetic disorder characterized by development of hyperkeratotic follicular papules on the scalp followed by progressive alopecia of the scalp, eyelashes, and eyebrows. Associated eye findings include photophobia in childhood and corneal dystrophy. Due to the genetic and clinical heterogeneity of similar disorders, a definitive diagnosis of KFSD is often challenging. Toward identification of the causative gene we reanalyzed a large Dutch KFSD family. SNP arrays (1 M) redefined the locus to a 2.9-Mb region at Xp22.12-Xp22.11. Screening of all 14 genes in the candidate region identified MBTPS2 as the candidate gene carrying a c.1523A>G (p.Asn508Ser) missense mutation. The variant was also identified in two unrelated X-linked KFSD families and cosegregated with KFSD in all families. In symptomatic female carriers, skewed X-inactivation of the normal allele matched with increased severity of symptoms. MBTPS2 is required for cleavage of sterol regulatory element-binding proteins (SREBPs). In vitro functional expression studies of the c.1523A>G mutation showed that sterol responsiveness was reduced by half. Other missense mutations in MBTPS2 have recently been identified in patients with IFAP syndrome. We postulate that both phenotypes are in the spectrum of one genetic disorder with a partially overlapping phenotype.

  17. Three-dimensional structure of actin filaments and of an actin gel made with actin-binding protein.

    PubMed

    Niederman, R; Amrein, P C; Hartwig, J

    1983-05-01

    Purified muscle actin and mixtures of actin and actin-binding protein were examined in the transmission electron microscope after fixation, critical point drying, and rotary shadowing. The three-dimensional structure of the protein assemblies was analyzed by a computer-assisted graphic analysis applicable to generalized filament networks. This analysis yielded information concerning the frequency of filament intersections, the filament length between these intersections, the angle at which filaments branch at these intersections, and the concentration of filaments within a defined volume. Purified actin at a concentration of 1 mg/ml assembled into a uniform mass of long filaments which overlap at random angles between 0 degrees and 90 degrees. Actin in the presence of macrophage actin-binding protein assembled into short, straight filaments, organized in a perpendicular branching network. The distance between branch points was inversely related to the molar ratio of actin-binding protein to actin. This distance was what would be predicted if actin filaments grew at right angles off of nucleation sites on the two ends of actin-binding protein dimers, and then annealed. The results suggest that actin in combination with actin-binding protein self-assembles to form a three-dimensional network resembling the peripheral cytoskeleton of motile cells.

  18. Enhanced gravitropism of roots with a disrupted cap actin cytoskeleton

    NASA Technical Reports Server (NTRS)

    Hou, Guichuan; Mohamalawari, Deepti R.; Blancaflor, Elison B.

    2003-01-01

    The actin cytoskeleton has been proposed to be a major player in plant gravitropism. However, understanding the role of actin in this process is far from complete. To address this problem, we conducted an analysis of the effect of Latrunculin B (Lat B), a potent actin-disrupting drug, on root gravitropism using various parameters that included detailed curvature kinetics, estimation of gravitropic sensitivity, and monitoring of curvature development after extended clinorotation. Lat B treatment resulted in a promotion of root curvature after a 90 degrees reorientation in three plant species tested. More significantly, the sensitivity of maize (Zea mays) roots to gravity was enhanced after actin disruption, as determined from a comparison of presentation time of Lat B-treated versus untreated roots. A short 10-min gravistimulus followed by extended rotation on a 1-rpm clinostat resulted in extensive gravitropic responses, manifested as curvature that often exceeded 90 degrees. Application of Lat B to the cap or elongation zone of maize roots resulted in the disruption of the actin cytoskeleton, which was confined to the area of localized Lat B application. Only roots with Lat B applied to the cap displayed the strong curvature responses after extended clinorotation. Our study demonstrates that disrupting the actin cytoskeleton in the cap leads to the persistence of a signal established by a previous gravistimulus. Therefore, actin could function in root gravitropism by providing a mechanism to regulate the proliferation of a gravitropic signal originating from the cap to allow the root to attain its correct orientation or set point angle.

  19. The association between osteoporotic hip fractures and actinic lesions as a biomarker for cumulative sun exposure in older people-a retrospective case-control study in Argentina.

    PubMed

    Perroud, H A; Dagatti, M S; Amigot, B; Levit, G P; Tomat, M F; Morosano, M E; Masoni, A M; Pezzotto, S M

    2016-04-02

    The aim of this study was to analyze the association between the presence of actinic lesions (solar keratosis and non-melanoma skin cancer) and osteoporotic hip fractures in older patients. Both pathologies are common conditions in this age group. Since cumulative sun exposure is difficult to quantify, the presence of actinic lesions can be used to indirectly analyze the association between ultraviolet radiation and osteoporotic hip fractures. This was an observational case-control study. We reviewed the centralized medical records of patients with hip fracture (cases, n = 51) and patients with other diseases hospitalized in the same institution and period (controls, n = 59). The mean age of the patients was 80 ± 8.3 years (range 50-103 years). Differences in maternal hip fracture history were found between cases and controls (14.8 and 8 %, respectively; p = 0.047). Falls history in the past year was higher in cases than in controls (p < 0.0001). Actinic lesions were observed in 32.7 % of patients (prevalence rate 23.5 % in cases, 40.7 % in controls; p = 0.04). When considering patients with actinic lesions, controls have a higher FRAX score compared with cases. Although sun exposure is recommended for bone health, it represents a risk factor for actinic lesions. The presence of actinic lesions may indicate a lower osteoporotic hip fracture risk. A balance between adequate lifetime sun exposure and protection against its adverse effects is required for each patient, in the context of geographic location.

  20. The application of 5-aminolevulinic acid in the treatment of precancerous lesions, skin cancer, and a new approach to the control of therapy

    NASA Astrophysics Data System (ADS)

    Kulas, Zbigniew; Bereś-Pawlik, Elżbieta; Bieniek, Andrzej; Matusiak, Łukasz

    2009-02-01

    The aim of our work was to determine a therapeutic effect of photodynamic therapy (PDT). Twenty five patients with the Bowen's disease, actinic keratosis and basal cell carcinoma (superficial, nodular) were examined. They were treated with photosensitizer - aminolevulinic acid (metabolized in protoporphyrin IX), and the new red light source built of high-power diodes. A new method, based on numerical analysis of fluorescence imaging of tissues, was proposed as a way for controlling therapy.

  1. Antibodies to Actin in Autoimmune Neutropenia

    DTIC Science & Technology

    1990-02-01

    protein as actin. Purified Acanthamoeba actin by anti-neutrophil antibodies in autoimmune neutropenia, comigrated with the protein and was specifically...anti-rabbit IgG were obtained from ICN Immunobiolog- formed using purified Acanthamoeba actin (gift of Dr Blair Bowers. icals, Naperville, IL. Cells...preparations𔃼 1 - was the protein recognized by these anti-neutrophil antibody 6 .2- positive sera, lgG, and F(ab’) 2. Purified Acanthamoeba actin

  2. An actin cytoskeleton with evolutionarily conserved functions in the absence of canonical actin-binding proteins

    PubMed Central

    Paredez, Alexander R.; Assaf, Zoe June; Sept, David; Timofejeva, Ljudmilla; Dawson, Scott C.; Wang, Chung-Ju Rachel; Cande, W. Z.

    2011-01-01

    Giardia intestinalis, a human intestinal parasite and member of what is perhaps the earliest-diverging eukaryotic lineage, contains the most divergent eukaryotic actin identified to date and is the first eukaryote known to lack all canonical actin-binding proteins (ABPs). We sought to investigate the properties and functions of the actin cytoskeleton in Giardia to determine whether Giardia actin (giActin) has reduced or conserved roles in core cellular processes. In vitro polymerization of giActin produced filaments, indicating that this divergent actin is a true filament-forming actin. We generated an anti-giActin antibody to localize giActin throughout the cell cycle. GiActin localized to the cortex, nuclei, internal axonemes, and formed C-shaped filaments along the anterior of the cell and a flagella-bundling helix. These structures were regulated with the cell cycle and in encysting cells giActin was recruited to the Golgi-like cyst wall processing vesicles. Knockdown of giActin demonstrated that giActin functions in cell morphogenesis, membrane trafficking, and cytokinesis. Additionally, Giardia contains a single G protein, giRac, which affects the Giardia actin cytoskeleton independently of known target ABPs. These results imply that there exist ancestral and perhaps conserved roles for actin in core cellular processes that are independent of canonical ABPs. Of medical significance, the divergent giActin cytoskeleton is essential and commonly used actin-disrupting drugs do not depolymerize giActin structures. Therefore, the giActin cytoskeleton is a promising drug target for treating giardiasis, as we predict drugs that interfere with the Giardia actin cytoskeleton will not affect the mammalian host. PMID:21444821

  3. An actin cytoskeleton with evolutionarily conserved functions in the absence of canonical actin-binding proteins.

    PubMed

    Paredez, Alexander R; Assaf, Zoe June; Sept, David; Timofejeva, Ljudmilla; Dawson, Scott C; Wang, Chung-Ju Rachel; Cande, W Z

    2011-04-12

    Giardia intestinalis, a human intestinal parasite and member of what is perhaps the earliest-diverging eukaryotic lineage, contains the most divergent eukaryotic actin identified to date and is the first eukaryote known to lack all canonical actin-binding proteins (ABPs). We sought to investigate the properties and functions of the actin cytoskeleton in Giardia to determine whether Giardia actin (giActin) has reduced or conserved roles in core cellular processes. In vitro polymerization of giActin produced filaments, indicating that this divergent actin is a true filament-forming actin. We generated an anti-giActin antibody to localize giActin throughout the cell cycle. GiActin localized to the cortex, nuclei, internal axonemes, and formed C-shaped filaments along the anterior of the cell and a flagella-bundling helix. These structures were regulated with the cell cycle and in encysting cells giActin was recruited to the Golgi-like cyst wall processing vesicles. Knockdown of giActin demonstrated that giActin functions in cell morphogenesis, membrane trafficking, and cytokinesis. Additionally, Giardia contains a single G protein, giRac, which affects the Giardia actin cytoskeleton independently of known target ABPs. These results imply that there exist ancestral and perhaps conserved roles for actin in core cellular processes that are independent of canonical ABPs. Of medical significance, the divergent giActin cytoskeleton is essential and commonly used actin-disrupting drugs do not depolymerize giActin structures. Therefore, the giActin cytoskeleton is a promising drug target for treating giardiasis, as we predict drugs that interfere with the Giardia actin cytoskeleton will not affect the mammalian host.

  4. F-actin distribution and function during sexual development in Eimeria maxima.

    PubMed

    Frölich, Sonja; Wallach, Michael

    2015-06-01

    To determine the involvement of the actin cytoskeleton in macrogametocyte growth and oocyst wall formation, freshly purified macrogametocytes and oocysts were stained with Oregon Green 514 conjugated phalloidin to visualize F-actin microfilaments, while Evans blue staining was used to detect type 1 wall forming bodies (WFB1s) and the outer oocyst wall. The double-labelled parasites were then analysed at various stages of sexual development using three-dimensional confocal microscopy. The results showed F-actin filaments were distributed throughout the entire cytoplasm of mature Eimeria maxima macrogametocytes forming a web-like meshwork of actin filaments linking the type 1 WFBs together into structures resembling 'beads on a string'. At the early stages of oocyst wall formation, F-actin localization changed in alignment with the egg-shaped morphology of the forming oocysts with F-actin microfilaments making direct contact with the WFB1s. In tissue oocysts, the labelled actin cytoskeleton was situated underneath the forming outer layer of the oocyst wall. Treatment of macrogametocytes in vitro with the actin depolymerizing agents, Cytochalasin D and Latrunculin, led to a reduction in the numbers of mature WFB1s in the cytoplasm of the developing macrogametocytes, indicating that the actin plays an important role in WFB1 transport and oocyst wall formation in E. maxima.

  5. Synthetic chondramide A analogues stabilize filamentous actin and block invasion by Toxoplasma gondii.

    PubMed

    Ma, Christopher I; Diraviyam, Karthikeyan; Maier, Martin E; Sept, David; Sibley, L David

    2013-09-27

    Apicomplexan parasites such as Toxoplasma gondii rely on actin-based motility to cross biological barriers and invade host cells. Key structural and biochemical differences in host and parasite actins make this an attractive target for small-molecule inhibitors. Here we took advantage of recent advances in the synthesis of cyclic depsipeptide compounds that stabilize filamentous actin to test the ability of chondramides to disrupt growth of T. gondii in vitro. Structural modeling of chondramide A (2) binding to an actin filament model revealed variations in the binding site between host and parasite actins. A series of 10 previously synthesized analogues (2b-k) with substitutions in the β-tyrosine moiety blocked parasite growth on host cell monolayers with EC₅₀ values that ranged from 0.3 to 1.3 μM. In vitro polymerization assays using highly purified recombinant actin from T. gondii verified that synthetic and natural product chondramides target the actin cytoskeleton. Consistent with this, chondramide treatment blocked parasite invasion into host cells and was more rapidly effective than pyrimethamine, a standard therapeutic agent. Although the current compounds lack specificity for parasite vs host actin, these studies provide a platform for the future design and synthesis of synthetic cyclic peptide inhibitors that selectively disrupt actin dynamics in parasites.

  6. The anti-proliferative agent jasplakinolide rearranges the actin cytoskeleton of plant cells.

    PubMed

    Sawitzky, H; Liebe, S; Willingale-Theune, J; Menzel, D

    1999-06-01

    In the present study, we have characterized the action of the natural cyclodepsipeptide jasplakinolide (JAS) on the cytoplasmic architecture, actin-based cytoplasmic motility, and the organization of the actin cytoskeleton in selected examples of green algae (Acetabularia, Pseudobryopsis and Nitella) and higher plant cells (Allium bulb scale cells and Sinapis root hairs). JAS was capable of influencing the actin cytoskeleton and inhibiting cytoplasmic streaming in a differential, cell type-specific manner. With the exception of Nitella, two consecutive responses were observed upon incubation with 2.5 microM JAS: In the first phase cytoplasmic streaming increased transiently alongside with minor modifications of the actin cytoskeleton in the form of adventitious actin spots and spikes appearing throughout the cell cortex in addition to the normal actin bundle system typical for each cell type. In the second phase, cytoplasmic streaming stopped and the actin cytoskeleton became heavily reorganized into shorter, straight, more and more randomly oriented bundle segments. JAS exerted severe long-term effects on the actin cytoskeleton when treatments exceeded 30min at a concentration of 2.5 microM. An in situ competition assay using equimolar concentrations of JAS and FITC-phalloidin suggested that JAS has a phalloidin-like action. Effects of JAS were significantly different from those of cytochalasin D with respect to the resulting degree of perturbance of cytoplasmic organization, the distribution of actin filaments and the speed of reversibility.

  7. Actin crosslinkers: repairing the sense of touch.

    PubMed

    Sun, Sean X; Walcott, Sam

    2010-10-26

    Cells use actin bundles infused with myosin to exert contractile forces on the extracellular environment. This active tension is essential for cellular mechanosensation. Now, the role of actin crosslinkers in stabilizing and repairing the actin bundles is coming into clearer view.

  8. Novel MBTPS2 missense mutation causes a keratosis follicularis spinulosa decalvans phenotype: mutation update and review of the literature.

    PubMed

    Zhang, J; Wang, Y; Cheng, R; Ni, C; Liang, J; Li, M; Yao, Z

    2016-10-01

    Keratosis follicularis spinulosa decalvans (KFSD) is an X-linked condition characterized by keratotic follicular papules and progressive alopecia, which is caused by mutations in the MBTPS2 gene. We carried out a genetic study on a child who was suspected clinically to have KFSD. Sanger sequencing was performed to detect mutations in the entire coding region of MBTPS2. A novel missense mutation (c.599C>T) was identified in the patient, confirming a diagnosis of KFSD. We reviewed related cases with MBTPS2 mutations for evidence of genotype-phenotype correlations.

  9. Mechanism of Actin-Based Motility

    NASA Astrophysics Data System (ADS)

    Pantaloni, Dominique; Le Clainche, Christophe; Carlier, Marie-France

    2001-05-01

    Spatially controlled polymerization of actin is at the origin of cell motility and is responsible for the formation of cellular protrusions like lamellipodia. The pathogens Listeria monocytogenes and Shigella flexneri, which undergo actin-based propulsion, are acknowledged models of the leading edge of lamellipodia. Actin-based motility of the bacteria or of functionalized microspheres can be reconstituted in vitro from only five pure proteins. Movement results from the regulated site-directed treadmilling of actin filaments, consistent with observations of actin dynamics in living motile cells and with the biochemical properties of the components of the synthetic motility medium.

  10. A coat of filamentous actin prevents clustering of late-endosomal vacuoles in vivo.

    PubMed

    Drengk, Anja; Fritsch, Jürgen; Schmauch, Christian; Rühling, Harald; Maniak, Markus

    2003-10-14

    The endocytic pathway depends on the actin cytoskeleton. Actin contributes to internalization at the plasma membrane and to subsequent trafficking steps like propulsion through the cytoplasm, fusion of phagosomes with early endosomes, and transport from early to late endosomes. In vitro studies with mammalian endosomes and yeast vacuoles implicate actin in membrane fusion. Here, we investigate the function of the actin coat that surrounds late endosomes in Dictyostelium. Latrunculin treatment leads to aggregation of these endosomes into grape-like clusters and completely blocks progression of endocytic marker. In addition, the cells round up and stop moving. Because this drug treatment perturbs all actin assemblies in the cell simultaneously, we used a novel targeting approach to specifically study the function of the cytoskeleton in one subcellular location. To this end, we constructed a hybrid protein targeting cofilin, an actin depolymerizing protein, to late endosomes. As a consequence, the endosomal compartments lost their actin coats and aggregated, but these cells remained morphologically normal, and the kinetics of endocytic marker trafficking were unaltered. Therefore, the actin coat prevents the clustering of endosomes, which could be one safeguard mechanism precluding their docking and fusion.

  11. Nuclear Actin in Development and Transcriptional Reprogramming.

    PubMed

    Misu, Shinji; Takebayashi, Marina; Miyamoto, Kei

    2017-01-01

    Actin is a highly abundant protein in eukaryotic cells and dynamically changes its polymerized states with the help of actin-binding proteins. Its critical function as a constituent of cytoskeleton has been well-documented. Growing evidence demonstrates that actin is also present in nuclei, referred to as nuclear actin, and is involved in a number of nuclear processes, including transcriptional regulation and chromatin remodeling. The contribution of nuclear actin to transcriptional regulation can be explained by its direct interaction with transcription machineries and chromatin remodeling factors and by controlling the activities of transcription factors. In both cases, polymerized states of nuclear actin affect the transcriptional outcome. Nuclear actin also plays an important role in activating strongly silenced genes in somatic cells for transcriptional reprogramming. When these nuclear functions of actin are considered, it is plausible to speculate that nuclear actin is also implicated in embryonic development, in which numerous genes need to be activated in a well-coordinated manner. In this review, we especially focus on nuclear actin's roles in transcriptional activation, reprogramming and development, including stem cell differentiation and we discuss how nuclear actin can be an important player in development and cell differentiation.

  12. Actin Dynamics: From Nanoscale to Microscale

    PubMed Central

    Carlsson, Anders E.

    2010-01-01

    The dynamic nature of actin in cells manifests itself in many ways: Polymerization near the cell edge is balanced by depolymerization in the interior, externally induced actin polymerization is followed by depolymerization, and spontaneous oscillations of the cell periphery are frequently seen. I discuss how mathematical modeling relates quantitative measures of actin dynamics to the rates of underlying molecular level processes. The rate of actin incorporation at the leading edge of a moving cell is roughly consistent with existing theories, and the factors determining the characteristic time of actin polymerization are fairly well understood. However, our understanding of actin disassembly is limited, in particular the interplay between severing and depolymerization and the role of specific combinations of proteins in implementing disassembly events. The origins of cell-edge oscillations, and their possible relation to actin waves, are a fruitful area of future research. PMID:20462375

  13. Expression of type I collagen and tenascin C is regulated by actin polymerization through MRTF in dedifferentiated chondrocytes.

    PubMed

    Parreno, Justin; Raju, Sneha; Niaki, Mortah Nabavi; Andrejevic, Katarina; Jiang, Amy; Delve, Elizabeth; Kandel, Rita

    2014-10-16

    This study examined actin regulation of fibroblast matrix genes in dedifferentiated chondrocytes. We demonstrated that dedifferentiated chondrocytes exhibit increased actin polymerization, nuclear localization of myocardin related transcription factor (MRTF), increased type I collagen (col1) and tenascin C (Tnc) gene expression, and decreased Sox9 gene expression. Induction of actin depolymerization by latrunculin treatment or cell rounding, reduced MRTF nuclear localization, repressed col1 and Tnc expression, and increased Sox9 gene expression in dedifferentiated chondrocytes. Treatment of passaged chondrocytes with MRTF inhibitor repressed col1 and Tnc expression, but did not affect Sox9 expression. Our results show that actin polymerization regulates fibroblast matrix gene expression through MRTF in passaged chondrocytes.

  14. In vitro and in vivo evidence for actin association of the naphthylphthalamic acid-binding protein from zucchini hypocotyls

    NASA Technical Reports Server (NTRS)

    Butler, J. H.; Hu, S.; Brady, S. R.; Dixon, M. W.; Muday, G. K.

    1998-01-01

    The N-1-naphthylphthalamic acid (NPA)-binding protein is part of the auxin efflux carrier, the protein complex that controls polar auxin transport in plant tissues. This study tested the hypothesis that the NPA-binding protein (NBP) is associated with the actin cytoskeleton in vitro and that an intact actin cytoskeleton is required for polar auxin transport in vivo. Cytoskeletal polymerization was altered in extracts of zucchini hypocotyls with reagents that stabilized either the polymeric or monomeric forms of actin or tubulin. Phalloidin treatment altered actin polymerization, as demonstrated by immunoblot analyses following native and denaturing electrophoresis. Phalloidin increased both filamentous actin (F-actin) and NPA-binding activity, while cytochalasin D and Tris decreased both F-actin and NPA-binding activity in cytoskeletal pellets. The microtubule stabilizing drug taxol increased pelletable tubulin, but did not alter either the amount of pelletable actin or NPA-binding activity. Treatment of etiolated zucchini hypocotyls with cytochalasin D decreased the amount of auxin transport and its regulation by NPA. These experimental results are consistent with an in vitro actin cytoskeletal association of the NPA-binding protein and with the requirement of an intact actin cytoskeleton for maximal polar auxin transport in vivo.

  15. Chlamydia trachomatis Tarp harbors distinct G and F actin binding domains that bundle actin filaments.

    PubMed

    Jiwani, Shahanawaz; Alvarado, Stephenie; Ohr, Ryan J; Romero, Adriana; Nguyen, Brenda; Jewett, Travis J

    2013-02-01

    All species of Chlamydia undergo a unique developmental cycle that transitions between extracellular and intracellular environments and requires the capacity to invade new cells for dissemination. A chlamydial protein called Tarp has been shown to nucleate actin in vitro and is implicated in bacterial entry into human cells. Colocalization studies of ectopically expressed enhanced green fluorescent protein (EGFP)-Tarp indicate that actin filament recruitment is restricted to the C-terminal half of the effector protein. Actin filaments are presumably associated with Tarp via an actin binding alpha helix that is also required for actin nucleation in vitro, but this has not been investigated. Tarp orthologs from C. pneumoniae, C. muridarum, and C. caviae harbor between 1 and 4 actin binding domains located in the C-terminal half of the protein, but C. trachomatis serovar L2 has only one characterized domain. In this work, we examined the effects of domain-specific mutations on actin filament colocalization with EGFP-Tarp. We now demonstrate that actin filament colocalization with Tarp is dependent on two novel F-actin binding domains that endow the Tarp effector with actin-bundling activity. Furthermore, Tarp-mediated actin bundling did not require actin nucleation, as the ability to bundle actin filaments was observed in mutant Tarp proteins deficient in actin nucleation. These data shed molecular insight on the complex cytoskeletal rearrangements required for C. trachomatis entry into host cells.

  16. Contractile properties of thin (actin) filament-reconstituted muscle fibers.

    PubMed

    Ishiwata, S; Funatsu, T; Fujita, H

    1998-01-01

    Selective removal and reconstitution of the components of muscle fibers (fibrils) is a useful means of examining the molecular mechanism underlying the formation of the contractile apparatus. In addition, this approach is powerful for examining the structure-function relationship of a specific component of the contractile system. In previous studies, we have achieved the partial structural and functional reconstitution of thin filaments in the skeletal contractile apparatus and full reconstitution in the cardiac contractile apparatus. First, all thin filaments other than short fragments at the Z line were removed by treatment with plasma gelsolin, an actin filament-severing protein. Under these conditions, no active tension could be generated. By incorporating exogenous actin into these thin filament-free fibers, actin filaments were reconstituted by polymerization on the short actin fragments remaining at the Z line, and active tension, which was insensitive to Ca2+, was restored. The active tension after the reconstitution of thin filaments reached as high as 30% of the original level in skeletal muscle, while it reached 140% in cardiac muscle. The augmentation of tension in cardiac muscle is mainly attributable to the elongation of reconstituted filaments, longer than the average length of thin filaments in an intact muscle. These results indicate that a muscle contractile apparatus with a high order structure and function can be constructed by the self-assembly of constituent proteins. Recently, we applied this reconstitution system to the study of the mechanism of spontaneous oscillatory contraction (SPOC) in thin (actin) filament-reconstituted cardiac muscle fibers. As a result, we found that SPOC occurs even in regulatory protein-free actin filament-reconstituted fibers (Fujita & Ishiwata, manuscript submitted), although the SPOC conditions were slightly different from the standard SPOC conditions. This result strongly suggests that spontaneous oscillation

  17. Mutations in SERPINB7, encoding a member of the serine protease inhibitor superfamily, cause Nagashima-type palmoplantar keratosis.

    PubMed

    Kubo, Akiharu; Shiohama, Aiko; Sasaki, Takashi; Nakabayashi, Kazuhiko; Kawasaki, Hiroshi; Atsugi, Toru; Sato, Showbu; Shimizu, Atsushi; Mikami, Shuji; Tanizaki, Hideaki; Uchiyama, Masaki; Maeda, Tatsuo; Ito, Taisuke; Sakabe, Jun-ichi; Heike, Toshio; Okuyama, Torayuki; Kosaki, Rika; Kosaki, Kenjiro; Kudoh, Jun; Hata, Kenichiro; Umezawa, Akihiro; Tokura, Yoshiki; Ishiko, Akira; Niizeki, Hironori; Kabashima, Kenji; Mitsuhashi, Yoshihiko; Amagai, Masayuki

    2013-11-07

    "Nagashima-type" palmoplantar keratosis (NPPK) is an autosomal recessive nonsyndromic diffuse palmoplantar keratosis characterized by well-demarcated diffuse hyperkeratosis with redness, expanding on to the dorsal surfaces of the palms and feet and the Achilles tendon area. Hyperkeratosis in NPPK is mild and nonprogressive, differentiating NPPK clinically from Mal de Meleda. We performed whole-exome and/or Sanger sequencing analyses of 13 unrelated NPPK individuals and identified biallelic putative loss-of-function mutations in SERPINB7, which encodes a cytoplasmic member of the serine protease inhibitor superfamily. We identified a major causative mutation of c.796C>T (p.Arg266(∗)) as a founder mutation in Japanese and Chinese populations. SERPINB7 was specifically present in the cytoplasm of the stratum granulosum and the stratum corneum (SC) of the epidermis. All of the identified mutants are predicted to cause premature termination upstream of the reactive site, which inhibits the proteases, suggesting a complete loss of the protease inhibitory activity of SERPINB7 in NPPK skin. On exposure of NPPK lesional skin to water, we observed a whitish spongy change in the SC, suggesting enhanced water permeation into the SC due to overactivation of proteases and a resultant loss of integrity of the SC structure. These findings provide an important framework for developing pathogenesis-based therapies for NPPK.

  18. [Cutaneous signs of Noonan's syndrome. Apropos of a case with ulerythema ophyogenes, disseminated pilar and sudoral keratosis and progressive alopecia].

    PubMed

    Grob, J J; Laure, M; Berge, G; Taramasco, M; Bore, P; Benderitter, T; Andrac, L; Collet, A M; Bonerandi, J J

    1988-01-01

    A case of typical Noonan syndrome (NS) with eye abnormalities, pterygium colli, cryptorchid testes, lymphoedema and asymmetrical cardiac septal hypertrophy is reported in a 8-month old infant. This case was particularly interesting since it included skin manifestations which enabled an early diagnosis to be made. Ulerythema ophryogenes has already been proposed as a cutaneous marker of NS, but the keratinization disorders in our patient also included disseminated keratosis of both hair follicles and sweat glands orifices. Abnormally brittle short curly hair has already been reported, but our patient exhibited progressive alopecia which is very rare in NS. Biochemical hair analysis did not show any abnormalities of aminoacids. All these features were suggestive of keratosis follicularis spinulosa decalvans. It therefore seems very likely that NS is associated with keratinization disorders but ulerythema ophryogenes might only be the limited form of these disorders. The other skin manifestations of NS are reviewed. Since the patient had 4 "café au lait" spots, the relation of NS with Von Recklinghausen syndrome, and neurofibromatosis-Noonan syndrome is discussed. Watson's Leopard and cardio-facial syndromes overlap with, and may represent subsets of NS.

  19. Labeling F-actin barbed ends with rhodamine-actin in permeabilized neuronal growth cones.

    PubMed

    Marsick, Bonnie M; Letourneau, Paul C

    2011-03-17

    The motile tips of growing axons are called growth cones. Growth cones lead navigating axons through developing tissues by interacting with locally expressed molecular guidance cues that bind growth cone receptors and regulate the dynamics and organization of the growth cone cytoskeleton. The main target of these navigational signals is the actin filament meshwork that fills the growth cone periphery and that drives growth cone motility through continual actin polymerization and dynamic remodeling. Positive or attractive guidance cues induce growth cone turning by stimulating actin filament (F-actin) polymerization in the region of the growth cone periphery that is nearer the source of the attractant cue. This actin polymerization drives local growth cone protrusion, adhesion of the leading margin and axonal elongation toward the attractant. Actin filament polymerization depends on the availability of sufficient actin monomer and on polymerization nuclei or actin filament barbed ends for the addition of monomer. Actin monomer is abundantly available in chick retinal and dorsal root ganglion (DRG) growth cones. Consequently, polymerization increases rapidly when free F-actin barbed ends become available for monomer addition. This occurs in chick DRG and retinal growth cones via the local activation of the F-actin severing protein actin depolymerizing factor (ADF/cofilin) in the growth cone region closer to an attractant. This heightened ADF/cofilin activity severs actin filaments to create new F-actin barbed ends for polymerization. The following method demonstrates this mechanism. Total content of F-actin is visualized by staining with fluorescent phalloidin. F-actin barbed ends are visualized by the incorporation of rhodamine-actin within growth cones that are permeabilized with the procedure described in the following, which is adapted from previous studies of other motile cells. When rhodamine-actin is added at a concentration above the critical concentration

  20. Nuclear Actin in Development and Transcriptional Reprogramming

    PubMed Central

    Misu, Shinji; Takebayashi, Marina; Miyamoto, Kei

    2017-01-01

    Actin is a highly abundant protein in eukaryotic cells and dynamically changes its polymerized states with the help of actin-binding proteins. Its critical function as a constituent of cytoskeleton has been well-documented. Growing evidence demonstrates that actin is also present in nuclei, referred to as nuclear actin, and is involved in a number of nuclear processes, including transcriptional regulation and chromatin remodeling. The contribution of nuclear actin to transcriptional regulation can be explained by its direct interaction with transcription machineries and chromatin remodeling factors and by controlling the activities of transcription factors. In both cases, polymerized states of nuclear actin affect the transcriptional outcome. Nuclear actin also plays an important role in activating strongly silenced genes in somatic cells for transcriptional reprogramming. When these nuclear functions of actin are considered, it is plausible to speculate that nuclear actin is also implicated in embryonic development, in which numerous genes need to be activated in a well-coordinated manner. In this review, we especially focus on nuclear actin’s roles in transcriptional activation, reprogramming and development, including stem cell differentiation and we discuss how nuclear actin can be an important player in development and cell differentiation. PMID:28326098

  1. Feeling for Filaments: Quantification of the Cortical Actin Web in Live Vascular Endothelium

    PubMed Central

    Kronlage, Cornelius; Schäfer-Herte, Marco; Böning, Daniel; Oberleithner, Hans; Fels, Johannes

    2015-01-01

    Contact-mode atomic force microscopy (AFM) has been shown to reveal cortical actin structures. Using live endothelial cells, we visualized cortical actin dynamics simultaneously by AFM and confocal fluorescence microscopy. We present a method that quantifies dynamic changes in the mechanical ultrastructure of the cortical actin web. We argue that the commonly used, so-called error signal imaging in AFM allows a qualitative, but not quantitative, analysis of cortical actin dynamics. The approach we used comprises fast force-curve-based topography imaging and subsequent image processing that enhances local height differences. Dynamic changes in the organization of the cytoskeleton network can be observed and quantified by surface roughness calculations and automated morphometrics. Upon treatment with low concentrations of the actin-destabilizing agent cytochalasin D, the cortical cytoskeleton network is thinned out and the average mesh size increases. In contrast, jasplakinolide, a drug that enhances actin polymerization, consolidates the cytoskeleton network and reduces the average mesh area. In conclusion, cortical actin dynamics can be quantified in live cells. To our knowledge, this opens a new pathway for conducting quantitative structure-function analyses of the endothelial actin web just beneath the apical plasma membrane. PMID:26287621

  2. Graphene Oxide Nanosheets Retard Cellular Migration via Disruption of Actin Cytoskeleton.

    PubMed

    Tian, Xin; Yang, Zaixing; Duan, Guangxin; Wu, Anqing; Gu, Zonglin; Zhang, Leili; Chen, Chunying; Chai, Zhifang; Ge, Cuicui; Zhou, Ruhong

    2017-01-01

    Graphene and graphene-based nanomaterials are broadly used for various biomedical applications due to their unique physiochemical properties. However, how graphene-based nanomaterials interact with biological systems has not been thoroughly studied. This study shows that graphene oxide (GO) nanosheets retard A549 lung carcinoma cell migration through nanosheet-mediated disruption of intracellular actin filaments. After GO nanosheets treatment, A549 cells display slower migration and the structure of the intracellular actin filaments is dramatically changed. It is found that GO nanosheets are capable of absorbing large amount of actin and changing the secondary structures of actin monomers. Large-scale all-atom molecular dynamics simulations further reveal the interactions between GO nanosheets and actin filaments at molecular details. GO nanosheets can insert into the interstrand gap of actin tetramer (helical repeating unit of actin filament) and cause the separation of the tetramer which eventually leads to the disruption of actin filaments. These findings offer a novel mechanism of GO nanosheet induced biophysical responses and provide more insights into their potential for biomedical applications.

  3. Changes in actin dynamics are involved in salicylic acid signaling pathway.

    PubMed

    Matoušková, Jindřiška; Janda, Martin; Fišer, Radovan; Sašek, Vladimír; Kocourková, Daniela; Burketová, Lenka; Dušková, Jiřina; Martinec, Jan; Valentová, Olga

    2014-06-01

    Changes in actin cytoskeleton dynamics are one of the crucial players in many physiological as well as non-physiological processes in plant cells. Positioning of actin filament arrays is necessary for successful establishment of primary lines of defense toward pathogen attack, depolymerization leads very often to the enhanced susceptibility to the invading pathogen. On the other hand it was also shown that the disruption of actin cytoskeleton leads to the induction of defense response leading to the expression of PATHOGENESIS RELATED proteins (PR). In this study we show that pharmacological actin depolymerization leads to the specific induction of genes in salicylic acid pathway but not that involved in jasmonic acid signaling. Life imaging of leafs of Arabidopsis thaliana with GFP-tagged fimbrin (GFP-fABD2) treated with 1 mM salicylic acid revealed rapid disruption of actin filaments resembling the pattern viewed after treatment with 200 nM latrunculin B. The effect of salicylic acid on actin filament fragmentation was prevented by exogenous addition of phosphatidic acid, which binds to the capping protein and thus promotes actin polymerization. The quantitative evaluation of actin filament dynamics is also presented.

  4. Nuclear actin depolymerization in transcriptionally active avian and amphibian oocytes leads to collapse of intranuclear structures

    PubMed Central

    Maslova, Antonina; Krasikova, Alla

    2012-01-01

    Actin, which is normally depleted in the nuclei of somatic cells, accumulates in high amounts in giant nuclei of amphibian oocytes. The supramolecular organization and functions of this nuclear pool of actin in growing vertebrate oocyte are controversial. Here, we investigated the role of nuclear actin in the maintenance of the spatial architecture of intranuclear structures in avian and amphibian growing oocytes. A meshwork of filamentous actin was not detected in freshly isolated or fixed oocyte nuclei of Xenopus, chicken or quail. We found that the actin meshwork inside the oocyte nucleus could be induced by phalloidin treatment. Actin polymerization is demonstrated to be required to stabilize the specific spatial organization of nuclear structures in avian and amphibian growing oocytes. In experiments with the actin depolymerizing drugs cytochalasin D and latrunculin A, we showed that disassembly of nuclear actin polymers led to chromosome condensation and their transportation to a limited space within the oocyte nucleus. Experimentally induced “collapsing” of chromosomes and nuclear bodies, together with global inhibition of transcription, strongly resembled the process of karyosphere formation during oocyte growth. PMID:22572951

  5. Keeping it all together: auxin-actin crosstalk in plant development.

    PubMed

    Zhu, Jinsheng; Geisler, Markus

    2015-08-01

    Polar auxin transport and the action of the actin cytoskeleton are tightly interconnected, which is documented by the finding that auxin transporters reach their final destination by active movement of secretory vesicles along F-actin tracks. Moreover, auxin transporter polarity and flexibility is thought to depend on transporter cycling that requires endocytosis and exocytosis of vesicles. In this context, we have reviewed the current literature on an involvement of the actin cytoskeleton in polar auxin transport and identify known similarities and differences in its structure, function and dynamics in comparison to non-plant organisms. By describing how auxin modulates actin expression and actin organization and how actin and its stability affects auxin-transporter endocytosis and recycling, we discuss the current knowledge on regulatory auxin-actin feedback loops. We focus on known effects of auxin and of auxin transport inhibitors on the stability and organization of actin and examine the functionality of auxin and/or auxin transport inhibitor-binding proteins with respect to their suitability to integrate auxin/auxin transport inhibitor action. Finally, we indicate current difficulties in the interpretation of organ, time and concentration-dependent auxin/auxin transport inhibitor treatments and formulate simple future experimental guidelines.

  6. Topical PDT in the Treatment of Benign Skin Diseases: Principles and New Applications.

    PubMed

    Kim, Miri; Jung, Haw Young; Park, Hyun Jeong

    2015-09-25

    Photodynamic therapy (PDT) uses a photosensitizer, light energy, and molecular oxygen to cause cell damage. Cells exposed to the photosensitizer are susceptible to destruction upon light absorption because excitation of the photosensitizing agents leads to the production of reactive oxygen species and, subsequently, direct cytotoxicity. Using the intrinsic cellular heme biosynthetic pathway, topical PDT selectively targets abnormal cells, while preserving normal surrounding tissues. This selective cytotoxic effect is the basis for the use of PDT in antitumor treatment. Clinically, PDT is a widely used therapeutic regimen for oncologic skin conditions such as actinic keratosis, squamous cell carcinoma in situ, and basal cell carcinoma. PDT has been shown, under certain circumstances, to stimulate the immune system and produce antibacterial, and/or regenerative effects while protecting cell viability. Thus, it may be useful for treating benign skin conditions. An increasing number of studies support the idea that PDT may be effective for treating acne vulgaris and several other inflammatory/infective skin diseases, including psoriasis, rosacea, viral warts, and aging-related changes. This review provides an overview of the clinical investigations of PDT and discusses each of the essential aspects of the sequence: its mechanism of action, common photosensitizers, light sources, and clinical applications in dermatology. Of the numerous clinical trials of PDT in dermatology, this review focuses on those studies that have reported remarkable therapeutic benefits following topical PDT for benign skin conditions such as acne vulgaris, viral warts, and photorejuvenation without causing severe side effects.

  7. Topical PDT in the Treatment of Benign Skin Diseases: Principles and New Applications

    PubMed Central

    Kim, Miri; Jung, Haw Young; Park, Hyun Jeong

    2015-01-01

    Photodynamic therapy (PDT) uses a photosensitizer, light energy, and molecular oxygen to cause cell damage. Cells exposed to the photosensitizer are susceptible to destruction upon light absorption because excitation of the photosensitizing agents leads to the production of reactive oxygen species and, subsequently, direct cytotoxicity. Using the intrinsic cellular heme biosynthetic pathway, topical PDT selectively targets abnormal cells, while preserving normal surrounding tissues. This selective cytotoxic effect is the basis for the use of PDT in antitumor treatment. Clinically, PDT is a widely used therapeutic regimen for oncologic skin conditions such as actinic keratosis, squamous cell carcinoma in situ, and basal cell carcinoma. PDT has been shown, under certain circumstances, to stimulate the immune system and produce antibacterial, and/or regenerative effects while protecting cell viability. Thus, it may be useful for treating benign skin conditions. An increasing number of studies support the idea that PDT may be effective for treating acne vulgaris and several other inflammatory/infective skin diseases, including psoriasis, rosacea, viral warts, and aging-related changes. This review provides an overview of the clinical investigations of PDT and discusses each of the essential aspects of the sequence: its mechanism of action, common photosensitizers, light sources, and clinical applications in dermatology. Of the numerous clinical trials of PDT in dermatology, this review focuses on those studies that have reported remarkable therapeutic benefits following topical PDT for benign skin conditions such as acne vulgaris, viral warts, and photorejuvenation without causing severe side effects. PMID:26404243

  8. Differential sensitivity to detergents of actin cytoskeleton from nerve endings.

    PubMed

    Cubí, Roger; Matas, Lluís A; Pou, Marta; Aguilera, José; Gil, Carles

    2013-11-01

    Detergent-resistant membranes (DRM), an experimental model used to study lipid rafts, are typically extracted from cells by means of detergent treatment and subsequent ultracentrifugation in density gradients, Triton X-100 being the detergent of choice in most of the works. Since lipid rafts are membrane microdomains rich in cholesterol, depletion of this component causes solubilization of DRM with detergent. In previous works from our group, the lack of effect of cholesterol depletion on DRM solubilization with Triton X-100 was detected in isolated rat brain synaptosomes. In consequence, the aim of the present work is to explore reasons for this observation, analyzing the possible role of the actin cytoskeleton, as well as the use of an alternative detergent, Brij 98, to overcome the insensitivity to Triton X-100 of cholesterol-depleted DRM. Brij 98 yields Brij-DRM that are highly dependent on cholesterol, since marker proteins (Flotillin-1 and Thy-1), as well as actin, appear solubilized after MCD treatment. Pretreatment with Latrunculin A results in a significant increase in Flotillin-1, Thy-1 and actin solubilization by Triton X-100 after cholesterol depletion. Studies with transmission electron microscopy show that combined treatment with MCD and Latrunculin A leads to a significant increase in solubilization of DRM with Triton X-100. Thus, Triton-DRM resistance to cholesterol depletion can be explained, at least partially, thanks to the scaffolding action of the actin cytoskeleton, without discarding differential effects of Brij 98 and Triton X-100 on specific membrane components. In conclusion, the detergent of choice is important when events that depend on the actin cytoskeleton are going to be studied.

  9. Actin dynamics in mouse fibroblasts in microgravity

    NASA Astrophysics Data System (ADS)

    Moes, Maarten J. A.; Bijvelt, Jose J.; Boonstra, Johannes

    2007-09-01

    After stimulating with the growth factor PDGF, cells exhibit abundant membrane ruffling and other morphological changes under normal gravity conditions. These morphological changes are largely determined by the actin microfilament system. Now these actin dynamics were studied under microgravity conditions in mouse fibroblasts during the DELTA mission. The aim of the present study was to describe the actin morphology in detail, to establish the effect of PDGF on actin morphology and to study the role of several actin-interacting proteins involved in introduced actin dynamics in microgravity. Identical experiments were conducted at 1G on earth as a reference. No results in microgravity were obtained due to a combination of malfunctioning hardware and unfulfilled temperature requirements.

  10. The actin cytoskeleton in endothelial cell phenotypes

    PubMed Central

    Prasain, Nutan; Stevens, Troy

    2009-01-01

    Endothelium forms a semi-permeable barrier that separates blood from the underlying tissue. Barrier function is largely determined by cell-cell and cell-matrix adhesions that define the limits of cell borders. Yet, such cell-cell and cell-matrix tethering is critically reliant upon the nature of adherence within the cell itself. Indeed, the actin cytoskeleton fulfills this essential function, to provide a strong, dynamic intracellular scaffold that organizes integral membrane proteins with the cell’s interior, and responds to environmental cues to orchestrate appropriate cell shape. The actin cytoskeleton is comprised of three distinct, but interrelated structures, including actin cross-linking of spectrin within the membrane skeleton, the cortical actin rim, and actomyosin-based stress fibers. This review addresses each of these actin-based structures, and discusses cellular signals that control the disposition of actin in different endothelial cell phenotypes. PMID:19028505

  11. Polymerization of actin by positively charged liposomes

    PubMed Central

    1988-01-01

    By cosedimentation, spectrofluorimetry, and electron microscopy, we have established that actin is induced to polymerize at low salt concentrations by positively charged liposomes. This polymerization occurs only at the surface of the liposomes, and thus monomers not in direct contact with the liposome remain monomeric. The integrity of the liposome membrane is necessary to maintain actin in its polymerized state since disruption of the liposome depolymerizes actin. Actin polymerized at the surface of the liposome is organized into two filamentous structures: sheets of parallel filaments in register and a netlike organization. Spectrofluorimetric analysis with the probe N- pyrenyl-iodoacetamide shows that actin is in the F conformation, at least in the environment of the probe. However, actin assembly induced by the liposome is not accompanied by full ATP hydrolysis as observed in vitro upon addition of salts. PMID:3360852

  12. Filopodia-like actin cables position nuclei in association with perinuclear actin in Drosophila nurse cells.

    PubMed

    Huelsmann, Sven; Ylänne, Jari; Brown, Nicholas H

    2013-09-30

    Controlling the position of the nucleus is vital for a number of cellular processes from yeast to humans. In Drosophila nurse cells, nuclear positioning is crucial during dumping, when nurse cells contract and expel their contents into the oocyte. We provide evidence that in nurse cells, continuous filopodia-like actin cables, growing from the plasma membrane and extending to the nucleus, achieve nuclear positioning. These actin cables move nuclei away from ring canals. When nurse cells contract, actin cables associate laterally with the nuclei, in some cases inducing nuclear turning so that actin cables become partially wound around the nuclei. Our data suggest that a perinuclear actin meshwork connects actin cables to nuclei via actin-crosslinking proteins such as the filamin Cheerio. We provide a revised model for how actin structures position nuclei in nurse cells, employing evolutionary conserved machinery.

  13. Persistent nuclear actin filaments inhibit transcription by RNA polymerase II.

    PubMed

    Serebryannyy, Leonid A; Parilla, Megan; Annibale, Paolo; Cruz, Christina M; Laster, Kyle; Gratton, Enrico; Kudryashov, Dmitri; Kosak, Steven T; Gottardi, Cara J; de Lanerolle, Primal

    2016-09-15

    Actin is abundant in the nucleus and it is clear that nuclear actin has important functions. However, mystery surrounds the absence of classical actin filaments in the nucleus. To address this question, we investigated how polymerizing nuclear actin into persistent nuclear actin filaments affected transcription by RNA polymerase II. Nuclear filaments impaired nuclear actin dynamics by polymerizing and sequestering nuclear actin. Polymerizing actin into stable nuclear filaments disrupted the interaction of actin with RNA polymerase II and correlated with impaired RNA polymerase II localization, dynamics, gene recruitment, and reduced global transcription and cell proliferation. Polymerizing and crosslinking nuclear actin in vitro similarly disrupted the actin-RNA-polymerase-II interaction and inhibited transcription. These data rationalize the general absence of stable actin filaments in mammalian somatic nuclei. They also suggest a dynamic pool of nuclear actin is required for the proper localization and activity of RNA polymerase II.

  14. Modeling actin waves in dictyostelium cells

    NASA Astrophysics Data System (ADS)

    Wasnik, Vaibhav; Mukhopadhyay, Ranjan

    2011-03-01

    Actin networks in living cells demonstrate a high capacity for self-organization and are responsible for the formation of a variety of structures such as lamellopodia, phagocytic cups, and cleavage furrows. Recent experiments have studied actin waves formed on the surface of dictyostelium cells that have been treated with a depolymerizing agent. These waves are believed to be physiologically important, for example, for the formation of phagocytic cups. We propose and study a minimal model, based on the dendritic nucleation of actin polymers, to explain the formation of these waves. This model can be extended to study the dynamics of the coupled actin-membrane system.

  15. GPCRs and actin-cytoskeleton dynamics.

    PubMed

    Vázquez-Victorio, Genaro; González-Espinosa, Claudia; Espinosa-Riquer, Zyanya P; Macías-Silva, Marina

    2016-01-01

    A multitude of physiological processes regulated by G protein-coupled receptors (GPCRs) signaling are accomplished by the participation of active rearrangements of the cytoskeleton. In general, it is common that a cross talk occurs among networks of microfilaments, microtubules, and intermediate filaments in order to reach specific cell responses. In particular, actin-cytoskeleton dynamics regulate processes such as cell shape, cell division, cell motility, and cell polarization, among others. This chapter describes the current knowledge about the regulation of actin-cytoskeleton dynamic by diverse GPCR signaling pathways, and also includes some protocols combining immunofluorescence and confocal microscopy for the visualization of the different rearrangements of the actin-cytoskeleton. We report how both the S1P-GPCR/G12/13/Rho/ROCK and glucagon-GPCR/Gs/cAMP axes induce differential actin-cytoskeleton rearrangements in epithelial cells. We also show that specific actin-binding molecules, like phalloidin and LifeAct, are very useful to analyze F-actin reorganization by confocal microscopy, and also that both molecules show similar results in fixed cells, whereas the anti-actin antibody is useful to detect both the G- and F-actin, as well as their compartmentalization. Thus, it is highly recommended to utilize different approaches to investigate the regulation of actin dynamics by GPCR signaling, with the aim to get a better picture of the phenomenon under study.

  16. Architecture and Connectivity Govern Actin Network Contractility.

    PubMed

    Ennomani, Hajer; Letort, Gaëlle; Guérin, Christophe; Martiel, Jean-Louis; Cao, Wenxiang; Nédélec, François; De La Cruz, Enrique M; Théry, Manuel; Blanchoin, Laurent

    2016-03-07

    Actomyosin contractility plays a central role in a wide range of cellular processes, including the establishment of cell polarity, cell migration, tissue integrity, and morphogenesis during development. The contractile response is variable and depends on actomyosin network architecture and biochemical composition. To determine how this coupling regulates actomyosin-driven contraction, we used a micropatterning method that enables the spatial control of actin assembly. We generated a variety of actin templates and measured how defined actin structures respond to myosin-induced forces. We found that the same actin filament crosslinkers either enhance or inhibit the contractility of a network, depending on the organization of actin within the network. Numerical simulations unified the roles of actin filament branching and crosslinking during actomyosin contraction. Specifically, we introduce the concept of "network connectivity" and show that the contractions of distinct actin architectures are described by the same master curve when considering their degree of connectivity. This makes it possible to predict the dynamic response of defined actin structures to transient changes in connectivity. We propose that, depending on the connectivity and the architecture, network contraction is dominated by either sarcomeric-like or buckling mechanisms. More generally, this study reveals how actin network contractility depends on its architecture under a defined set of biochemical conditions.

  17. Bioinformatics study of the mangrove actin genes

    NASA Astrophysics Data System (ADS)

    Basyuni, M.; Wasilah, M.; Sumardi

    2017-01-01

    This study describes the bioinformatics methods to analyze eight actin genes from mangrove plants on DDBJ/EMBL/GenBank as well as predicted the structure, composition, subcellular localization, similarity, and phylogenetic. The physical and chemical properties of eight mangroves showed variation among the genes. The percentage of the secondary structure of eight mangrove actin genes followed the order of a helix > random coil > extended chain structure for BgActl, KcActl, RsActl, and A. corniculatum Act. In contrast to this observation, the remaining actin genes were random coil > extended chain structure > a helix. This study, therefore, shown the prediction of secondary structure was performed for necessary structural information. The values of chloroplast or signal peptide or mitochondrial target were too small, indicated that no chloroplast or mitochondrial transit peptide or signal peptide of secretion pathway in mangrove actin genes. These results suggested the importance of understanding the diversity and functional of properties of the different amino acids in mangrove actin genes. To clarify the relationship among the mangrove actin gene, a phylogenetic tree was constructed. Three groups of mangrove actin genes were formed, the first group contains B. gymnorrhiza BgAct and R. stylosa RsActl. The second cluster which consists of 5 actin genes the largest group, and the last branch consist of one gene, B. sexagula Act. The present study, therefore, supported the previous results that plant actin genes form distinct clusters in the tree.

  18. F-actin waves, actin cortex disassembly and focal exocytosis driven by actin-phosphoinositide positive feedback.

    PubMed

    Masters, Thomas A; Sheetz, Michael P; Gauthier, Nils C

    2016-04-01

    Actin polymerization is controlled by the phosphoinositide composition of the plasma membrane. However, the molecular mechanisms underlying the spatiotemporal regulation of actin network organization over extended length scales are still unclear. To observe phosphoinositide-dependent cytoskeletal dynamics we combined the model system of frustrated phagocytosis, total internal reflection microscopy and manipulation of the buffer tonicity. We found that macrophages interacting with IgG-coated glass substrates formed circular F-actin waves on their ventral surface enclosing a region of plasma membrane devoid of cortical actin. Plasma membrane free of actin cortex was strongly depleted of PI(4,5)P2 , but enriched in PI(3,4)P2 and displayed a fivefold increase in exocytosis. Wave formation could be promoted by application of a hypotonic shock. The actin waves were characteristic of a bistable wavefront at the boundary between the regions of membrane containing and lacking cortical actin. Phosphoinositide modifiers and RhoGTPase activities dramatically redistributed with respect to the wavefronts, which often exhibited spatial oscillations. Perturbation of either lipid or actin cytoskeleton-related pathways led to rapid loss of both the polarized lipid distribution and the wavefront. As waves travelled over the plasma membrane, wavefront actin was seen to rapidly polymerize and depolymerize at pre-existing clusters of FcγRIIA, coincident with rapid changes in lipid composition. Thus the potential of receptors to support rapid F-actin polymerization appears to depend acutely on the local concentrations of multiple lipid species. We propose that interdependence through positive feedback from the cytoskeleton to lipid modifiers leads to coordinated local cortex remodeling, focal exocytosis, and organizes extended actin networks.

  19. Closure of supporting cell scar formations requires dynamic actin mechanisms

    PubMed Central

    Hordichok, Andrew J.; Steyger, Peter S.

    2007-01-01

    In many vertebrate inner ear sensory epithelia, dying sensory hair cells are extruded, and the apices of surrounding supporting cells converge to re-seal the epithelial barrier between the electrochemically-distinct endolymph and perilymph. These cellular mechanisms remain poorly understood. Dynamic microtubular mechanisms have been proposed for hair cell extrusion; while contractile actomyosin-based mechanisms are required for cellular extrusion and closure in epithelial monolayers. The hypothesis that cytoskeletal mechanisms are required for hair cell extrusion and supporting cell scar formation was tested using bullfrog saccules incubated with gentamicin (6 hours), and allowed to recover (18 hours). Explants were then fixed, labeled for actin and cytokeratins, and viewed with confocal microscopy. To block dynamic cytoskeletal processes, disruption agents for microtubules (colchicine, paclitaxel) myosin (Y-27632, ML-9) or actin (cytochalasin D, latrunculin A) were added during treatment and recovery. Microtubule disruption agents had no effect on hair cell extrusion or supporting cell scar formation. Myosin disruption agents appeared to slow down scar formation but not hair cell extrusion. Actin disruption agents blocked scar formation, and largely prevented hair cell extrusion. These data suggest that actin-based cytoskeletal processes are required for hair cell extrusion and supporting cell scar formation in bullfrog saccules. PMID:17716843

  20. The nitrate reductase inhibitor, tungsten, disrupts actin microfilaments in Zea mays L.

    PubMed

    Adamakis, Ioannis-Dimosthenis S; Panteris, Emmanuel; Eleftheriou, Eleftherios P

    2014-05-01

    Tungsten is a widely used inhibitor of nitrate reductase, applied to diminish the nitric oxide levels in plants. It was recently shown that tungsten also has heavy metal attributes. Since information about the toxic effects of tungsten on actin is limited, and considering that actin microfilaments are involved in the entry of tungsten inside plant cells, the effects of tungsten on them were studied in Zea mays seedlings. Treatments with sodium tungstate for 3, 6, 12 or 24 h were performed on intact seedlings and seedlings with truncated roots. Afterwards, actin microfilaments in meristematic root and leaf tissues were stained with fluorescent phalloidin, and the specimens were examined by confocal laser scanning microscopy. While the actin microfilament network was well organized in untreated seedlings, in tungstate-treated ones it was disrupted in a time-dependent manner. In protodermal root cells, the effects of tungsten were stronger as cortical microfilaments were almost completely depolymerized and the intracellular ones appeared highly bundled. Fluorescence intensity measurements confirmed the above results. In the meristematic leaf tissue of intact seedlings, no depolymerization of actin microfilaments was noticed. However, when root tips were severed prior to tungstate application, both cortical and endoplasmic actin networks of leaf cells were disrupted and bundled after 24 h of treatment. The differential response of root and leaf tissues to tungsten toxicity may be due to differential penetration and absorption, while the effects on actin microfilaments could not be attributed to the nitric oxide depletion by tungsten.

  1. Reconstitution of a Minimal Actin Cortex by Coupling Actin Filaments to Reconstituted Membranes.

    PubMed

    Vogel, Sven K

    2016-01-01

    A thin layer of actin filaments in many eukaryotic cell types drives pivotal aspects of cell morphogenesis and is generally cited as the actin cortex. Myosin driven contractility and actin cytoskeleton membrane interactions form the basis of fundamental cellular processes such as cytokinesis, cell migration, and cortical flows. How the interplay between the actin cytoskeleton, the membrane, and actin binding proteins drives these processes is far from being understood. The complexity of the actin cortex in living cells and the hardly feasible manipulation of the omnipotent cellular key players, namely actin, myosin, and the membrane, are challenging in order to gain detailed insights about the underlying mechanisms. Recent progress in developing bottom-up in vitro systems where the actin cytoskeleton is combined with reconstituted membranes may provide a complementary route to reveal general principles underlying actin cortex properties. In this chapter the reconstitution of a minimal actin cortex by coupling actin filaments to a supported membrane is described. This minimal system may be very well suited to study for example protein interactions on membrane bound actin filaments in a very controlled and quantitative manner as it may be difficult to perform in living systems.

  2. Imiquimod - Its role in the treatment of cutaneous malignancies

    PubMed Central

    Bubna, Aditya Kumar

    2015-01-01

    Imiquimod is a synthetic imidazoquinolone amine, which has potent immune response modifier activity, when topically used. This characteristic property of imiquimod has led to its use in a number of applications in dermatology, particularly in cutaneous malignancies, where it has been found to be effective and safe. Currently, additional mechanisms for its activity in actinic keratosis, basal cell carcinoma, and invasive squamous cell carcinoma have been elucidated. Its usage for cutaneous metastasis in breast cancer has been a further addition to its therapeutic armamentarium recently. PMID:26288465

  3. The pros and cons of common actin labeling tools for visualizing actin dynamics during Drosophila oogenesis.

    PubMed

    Spracklen, Andrew J; Fagan, Tiffany N; Lovander, Kaylee E; Tootle, Tina L

    2014-09-15

    Dynamic remodeling of the actin cytoskeleton is required for both development and tissue homeostasis. While fixed image analysis has provided significant insight into such events, a complete understanding of cytoskeletal dynamics requires live imaging. Numerous tools for the live imaging of actin have been generated by fusing the actin-binding domain from an actin-interacting protein to a fluorescent protein. Here we comparatively assess the utility of three such tools--Utrophin, Lifeact, and F-tractin--for characterizing the actin remodeling events occurring within the germline-derived nurse cells during Drosophila mid-oogenesis or follicle development. Specifically, we used the UAS/GAL4 system to express these tools at different levels and in different cells, and analyzed these tools for effects on fertility, alterations in the actin cytoskeleton, and ability to label filamentous actin (F-actin) structures by both fixed and live imaging. While both Utrophin and Lifeact robustly label F-actin structures within the Drosophila germline, when strongly expressed they cause sterility and severe actin defects including cortical actin breakdown resulting in multi-nucleate nurse cells, early F-actin filament and aggregate formation during stage 9 (S9), and disorganized parallel actin filament bundles during stage 10B (S10B). However, by using a weaker germline GAL4 driver in combination with a higher temperature, Utrophin can label F-actin with minimal defects. Additionally, strong Utrophin expression within the germline causes F-actin formation in the nurse cell nuclei and germinal vesicle during mid-oogenesis. Similarly, Lifeact expression results in nuclear F-actin only within the germinal vesicle. F-tractin expresses at a lower level than the other two labeling tools, but labels cytoplasmic F-actin structures well without causing sterility or striking actin defects. Together these studies reveal how critical it is to evaluate the utility of each actin labeling tool

  4. The pros and cons of common actin labeling tools for visualizing actin dynamics during Drosophila oogenesis

    PubMed Central

    Spracklen, Andrew J.; Fagan, Tiffany N.; Lovander, Kaylee E.; Tootle, Tina L.

    2015-01-01

    Dynamic remodeling of the actin cytoskeleton is required for both development and tissue homeostasis. While fixed image analysis has provided significant insight into such events, a complete understanding of cytoskeletal dynamics requires live imaging. Numerous tools for the live imaging of actin have been generated by fusing the actin-binding domain from an actin-interacting protein to a fluorescent protein. Here we comparatively assess the utility of three such tools – Utrophin, Lifeact, and F-tractin – for characterizing the actin remodeling events occurring within the germline-derived nurse cells during Drosophila mid-oogenesis or follicle development. Specifically, we used the UAS/GAL4 system to express these tools at different levels and in different cells, and analyzed these tools for effects on fertility, alterations in the actin cytoskeleton, and ability to label filamentous actin (F-actin) structures by both fixed and live imaging. While both Utrophin and Lifeact robustly label F-actin structures within the Drosophila germline, when strongly expressed they cause sterility and severe actin defects including cortical actin breakdown resulting in multi-nucleate nurse cells, early F-actin filament and aggregate formation during stage 9 (S9), and disorganized parallel actin filament bundles during stage 10B (S10B). However, by using a weaker germline GAL4 driver in combination with a higher temperature, Utrophin can label F-actin with minimal defects. Additionally, strong Utrophin expression within the germline causes F-actin formation in the nurse cell nuclei and germinal vesicle during mid-oogenesis. Similarly, Lifeact expression results in nuclear F-actin only within the germinal vesicle. F-tractin expresses at a lower level than the other two labeling tools, but labels cytoplasmic F-actin structures well without causing sterility or striking actin defects. Together these studies reveal how critical it is to evaluate the utility of each actin labeling

  5. Papaverine Prevents Vasospasm by Regulation of Myosin Light Chain Phosphorylation and Actin Polymerization in Human Saphenous Vein

    PubMed Central

    Hocking, Kyle M.; Putumbaka, Gowthami; Wise, Eric S.; Cheung-Flynn, Joyce; Brophy, Colleen M.; Komalavilas, Padmini

    2016-01-01

    Objective Papaverine is used to prevent vasospasm in human saphenous veins (HSV) during vein graft preparation prior to implantation as a bypass conduit. Papaverine is a nonspecific inhibitor of phosphodiesterases, leading to increases in both intracellular cGMP and cAMP. We hypothesized that papaverine reduces force by decreasing intracellular calcium concentrations ([Ca2+]i) and myosin light chain phosphorylation, and increasing actin depolymerization via regulation of actin regulatory protein phosphorylation. Approach and Results HSV was equilibrated in a muscle bath, pre-treated with 1 mM papaverine followed by 5 μM norepinephrine, and force along with [Ca2+]i levels were concurrently measured. Filamentous actin (F-actin) level was measured by an in vitro actin assay. Tissue was snap frozen to measure myosin light chain and actin regulatory protein phosphorylation. Pre-treatment with papaverine completely inhibited norepinephrine-induced force generation, blocked increases in [Ca2+]i and led to a decrease in the phosphorylation of myosin light chain. Papaverine pre-treatment also led to increased phosphorylation of the heat shock-related protein 20 (HSPB6) and the vasodilator stimulated phosphoprotein (VASP), as well as decreased filamentous actin (F-actin) levels suggesting depolymerization of actin. Conclusions These results suggest that papaverine-induced force inhibition of HSV involves [Ca2+]i-mediated inhibition of myosin light chain phosphorylation and actin regulatory protein phosphorylation-mediated actin depolymerization. Thus, papaverine induces sustained inhibition of contraction of HSV by the modulation of both myosin cross-bridge formation and actin cytoskeletal dynamics and is a pharmacological alternative to high pressure distention to prevent vasospasm. PMID:27136356

  6. Force of an actin spring

    NASA Astrophysics Data System (ADS)

    Shin, Jennifer; Mahadevan, L.; Matsudaira, Paul

    2003-03-01

    The acrosomal process of the horseshoe crab sperm is a novel mechanochemical molecular spring that converts its elastic stain energy to mechanical work upon the chemical activation by Ca2+. Twisted and bent, the initial state of the acrosomal bundle features a high degree of complexity in its structure and the energy is believed to be stored in the highly strained actin filaments as an elastic potential energy. When activated, the bundle relaxes from the coil of the highly twisted and bent filaments to its straight conformation at a mean velocity of 15um/s. The mean extension velocity increases dramatically from 3um/s to 27um/s when temperature of the medium is changed from 9.6C to 32C (respective viscosities of 1.25-0.75cp), yet it exhibits a very weak dependence on changes in the medium viscosity (1cp-33cp). These experiments suggest that the uncoiling of the actin spring should be limited not by the viscosity of the medium but by the unlatching events of involved proteins at a molecular level. Unlike the viscosity-limited processes, where force is directly related to the rate of the reaction, a direct measurement is required to obtain the spring force of the acrosomal process. The extending acrosomal bundle is forced to push against a barrier and its elastic buckling response is analyzed to measure the force generated during the uncoiling.

  7. Melanoma in Situ Treated with Topical Imiquimod for Management of Persistently Positive Margins: A Review of Treatment Methods

    PubMed Central

    Fan, Qing; Cohen, Stephanie; John, Becky; Riker, Adam I.

    2015-01-01

    Background Imiquimod is a topical cream approved by the US Food and Drug Administration for treatment of superficial basal cell carcinoma, actinic keratosis, and genital-perianal warts. Its successful use in patients with persistently positive margins of melanoma in situ (MIS) after surgical excision has been previously reported. Case Report A 75-year-old female presented with a primary melanoma that was removed through an elliptical excision with 1 cm margins. Pathology revealed 3 involved margins with residual MIS without an invasive component. After a second operation removed an additional 1 cm margin, pathology revealed 2 positive margins with residual MIS. Rather than undergoing a third excision, the patient decided to pursue a nonsurgical approach with topical imiquimod, and at the 4-month follow-up examination, the incision was completely healed with no clinical evidence of tumor recurrence. Conclusion A nonsurgical approach with 5% topical imiquimod cream applied along the incision was utilized. In specific patient populations, the use of imiquimod is a reasonable alternative approach for the management of persistently positive MIS margins. Long-term follow-up is necessary to assess for evidence of recurrence and the ultimate success of this nonsurgical approach. PMID:26730231

  8. Synthetic peptides that cause F-actin bundling and block actin depolymerization

    DOEpatents

    Sederoff, Heike [Raleigh, NC; Huber, Steven C [Savoy, IL; Larabell, Carolyn A [Berkeley, CA

    2011-10-18

    Synthetic peptides derived from sucrose synthase, and having homology to actin and actin-related proteins, sharing a common motif, useful for causing acting bundling and preventing actin depolymerization. Peptides exhibiting the common motif are described, as well as specific synthetic peptides which caused bundled actin and inhibit actin depolymerization. These peptides can be useful for treating a subject suffering from a disease characterized by cells having neoplastic growth, for anti-cancer therapeutics, delivered to subjects solely, or concomitantly or sequentially with other known cancer therapeutics. These peptides can also be used for stabilizing microfilaments in living cells and inhibiting growth of cells.

  9. Nonsurgical Innovations in the Treatment of Nonmelanoma Skin Cancer

    PubMed Central

    Amini, Sadegh; Viera, Martha H.; Valins, Whitney

    2010-01-01

    Basal cell carcinoma and squamous cell carcinoma are the most frequent types of cancer in the United States and represent 75 percent and 20 percent, respectively, of all nonmelanoma skin cancers. Since ultraviolet radiation is implicated in their development, photoprotection is fundamental in their prevention. Additional preventive measures include identifying high-risk individuals for early detection along with using agents, such as retinoids, that are effective in decreasing the risk of premalignant cells further developing into carcinomas. Newer agents achieving this goal include perillyl alcohol, T4 endonuclease 5, DL-α-tocopherol, and α-difluoromethylornithine. Procedural modalities are currently the standard of treatment, but recent evidence has consistently shown that newer (nonsurgical) therapies, such as interferon, imiquimod, retinoids, and 5-fluorouracil, can be used effectively either as monotherapies or as adjuvants to those surgical modalities for the treatment of superficial nonmelanoma skin cancers and premalignant lesions. These newer therapies have achieved significant reductions in morbidity and mortality. Procedural modalities that have been evolving into important tools for the treatment of actinic keratosis and nonmelanoma skin cancers include photodynamic therapy and lasers. Nonsurgical therapies currently proving to be effective in clinical trials include ingenol mebutate and cyclooxygenase-2 inhibitors. Agents that are showing promising results in early phases of clinical trials include betulinic acid; hedgehog signaling pathway inhibitors, such as cyclopamine and GDC-0449; α-melanocyte–stimulating hormone analogs, such as afamelanotide; epidermal growth factor receptor inhibitors, such as gefitinib and erlotinib; anti-epidermal growth factor receptor monoclonal antibodies, such as cetuximab and panitumumab; and the 5-fluorouracil prodrug capecitabine. PMID:20725548

  10. Growing an actin gel on spherical surfaces.

    PubMed Central

    Noireaux, V; Golsteyn, R M; Friederich, E; Prost, J; Antony, C; Louvard, D; Sykes, C

    2000-01-01

    Inspired by the motility of the bacteria Listeria monocytogenes, we have experimentally studied the growth of an actin gel around spherical beads grafted with ActA, a protein known to be the promoter of bacteria movement. On ActA-grafted beads F-actin is formed in a spherical manner, whereas on the bacteria a "comet-like" tail of F-actin is produced. We show experimentally that the stationary thickness of the gel depends on the radius of the beads. Moreover, the actin gel is not formed if the ActA surface density is too low. To interpret our results, we propose a theoretical model to explain how the mechanical stress (due to spherical geometry) limits the growth of the actin gel. Our model also takes into account treadmilling of actin. We deduce from our work that the force exerted by the actin gel on the bacteria is of the order of 10 pN. Finally, we estimate from our theoretical model possible conditions for developing actin comet tails. PMID:10692348

  11. Molecular genetic analysis of two families with keratosis follicularis spinulosa decalvans: refinement of gene localization and evidence for genetic heterogeneity.

    PubMed

    Oosterwijk, J C; Richard, G; van der Wielen, M J; van de Vosse, E; Harth, W; Sandkuijl, L A; Bakker, E; van Ommen, G J

    1997-10-01

    X-linked keratosis follicularis spinulosa decalvans (KFSD) is a rare disorder affecting both skin and eyes. In the two extended KFSD families analysed to date, the gene was mapped to Xp22.13-p22.2. By analyzing several new markers in this region, we were able to narrow the candidate region to a 1-Mb interval between DXS7161 and (DXS7593, DXS7105) in the large Dutch pedigree. In addition, we analyzed 23 markers in Xp21.2-p22.2 in a German family with KFSD. Haplotype and recombination analysis positioned the KFSD gene in this family most likely outside the candidate region on Xp22.13-p22.2. This finding is suggestive for genetic heterogeneity: in this pedigree there is either another locus on the X-chromosome, or KFSD is transmitted here as an autosomal dominant trait with variable expression.

  12. The Yeast V159N Actin Mutant Reveals Roles for Actin Dynamics In Vivo

    PubMed Central

    Belmont, Lisa D.; Drubin, David G.

    1998-01-01

    Actin with a Val 159 to Asn mutation (V159N) forms actin filaments that depolymerize slowly because of a failure to undergo a conformational change after inorganic phosphate release. Here we demonstrate that expression of this actin results in reduced actin dynamics in vivo, and we make use of this property to study the roles of rapid actin filament turnover. Yeast strains expressing the V159N mutant (act1-159) as their only source of actin have larger cortical actin patches and more actin cables than wild-type yeast. Rapid actin dynamics are not essential for cortical actin patch motility or establishment of cell polarity. However, fluid phase endocytosis is defective in act1-159 strains. act1-159 is synthetically lethal with cofilin and profilin mutants, supporting the conclusion that mutations in all of these genes impair the polymerization/ depolymerization cycle. In contrast, act1-159 partially suppresses the temperature sensitivity of a tropomyosin mutant, and the loss of cytoplasmic cables seen in fimbrin, Mdm20p, and tropomyosin null mutants, suggesting filament stabilizing functions for these actin-binding proteins. Analysis of the cables in these double-mutant cells supports a role for fimbrin in organizing cytoplasmic cables and for Mdm20p and tropomyosin in excluding cofilin from the cables. PMID:9732289

  13. Morphological changes in liposomes caused by polymerization of encapsulated actin and spontaneous formation of actin bundles.

    PubMed Central

    Miyata, H; Hotani, H

    1992-01-01

    Spherical giant liposomes that had encapsulated skeletal-muscle G-actin were made by swelling a dried lipid mixture of dimyristoyl phosphatidylcholine/cardiolipin, 1:1 (wt/wt), in a solution of G-actin/CaCl2 at 0 degree C. Polymerization of the encapsulated G-actin into actin filaments was achieved by raising the temperature to 30 degrees C. We observed the subsequent shape changes of the liposomes by dark-field and differential interference-contrast light microscopy. After approximately 40 min, which was required for completion of actin polymerization, two shapes of liposome were evident: dumbbell and disk. Elongation of the dumbbell-shaped liposomes was concomitant with actin polymerization. Polarization microscopy showed that actin filaments formed thick bundles in the liposomes and that these filaments lay contiguous to the periphery of the liposome. Localization of actin filaments in the liposomes was confirmed by observation of rhodamine phalloidin-conjugated actin filaments by fluorescence microscopy. Both dumbbell- and disk-shaped liposomes were rigid and kept their shapes as far as actin filaments were stabilized. In contrast, liposomes containing bovine serum albumin were fragile, and their shapes continually fluctuated from Brownian motion, indicating that the actin bundles served as mechanical support for the liposome shapes. Images PMID:1454846

  14. F- and G-actin homeostasis regulates mechanosensitive actin nucleation by formins.

    PubMed

    Higashida, Chiharu; Kiuchi, Tai; Akiba, Yushi; Mizuno, Hiroaki; Maruoka, Masahiro; Narumiya, Shuh; Mizuno, Kensaku; Watanabe, Naoki

    2013-04-01

    Physical force evokes rearrangement of the actin cytoskeleton. Signalling pathways such as tyrosine kinases, stretch-activated Ca(2+) channels and Rho GTPases are involved in force sensing. However, how signals are transduced to actin assembly remains obscure. Here we show mechanosensitive actin polymerization by formins (formin homology proteins). Cells overexpressing mDia1 increased the amount of F-actin on release of cell tension. Fluorescence single-molecule speckle microscopy revealed rapid induction of processive actin assembly by mDia1 on cell cortex deformation. mDia1 lacking the Rho-binding domain and other formins exhibited mechanosensitive actin nucleation, suggesting Rho-independent activation. Mechanosensitive actin nucleation by mDia1 required neither Ca(2+) nor kinase signalling. Overexpressing LIM kinase abrogated the induction of processive mDia1. Furthermore, s-FDAPplus (sequential fluorescence decay after photoactivation) analysis revealed a rapid actin monomer increase on cell cortex deformation. Our direct visualization of the molecular behaviour reveals a mechanosensitive actin filament regeneration mechanism in which G-actin released by actin remodelling plays a pivotal role.

  15. Lifeact: a versatile marker to visualize F-actin.

    PubMed

    Riedl, Julia; Crevenna, Alvaro H; Kessenbrock, Kai; Yu, Jerry Haochen; Neukirchen, Dorothee; Bista, Michal; Bradke, Frank; Jenne, Dieter; Holak, Tad A; Werb, Zena; Sixt, Michael; Wedlich-Soldner, Roland

    2008-07-01

    Live imaging of the actin cytoskeleton is crucial for the study of many fundamental biological processes, but current approaches to visualize actin have several limitations. Here we describe Lifeact, a 17-amino-acid peptide, which stained filamentous actin (F-actin) structures in eukaryotic cells and tissues. Lifeact did not interfere with actin dynamics in vitro and in vivo and in its chemically modified peptide form allowed visualization of actin dynamics in nontransfectable cells.

  16. Synthetic mimetics of actin-binding macrolides: rational design of actin-targeted drugs.

    PubMed

    Perrins, Richard D; Cecere, Giuseppe; Paterson, Ian; Marriott, Gerard

    2008-03-01

    Actin polymerization and dynamics are involved in a wide range of cellular processes such as cell division and migration of tumor cells. At sites of cell lysis, such as those occurring during a stroke or inflammatory lung diseases, actin is released into the serum where it polymerizes, leading to problems with clot dissolution and sputum viscosity. Therefore, drugs that target these actin-mediated processes may provide one mechanism to treat these conditions. Marine-organism-derived macrolides, such as reidispongiolide A, can bind to, sever, and inhibit polymerization of actin. Our studies show that the function of these complex macrolides resides in their tail region, whereas the head group stabilizes the actin-drug complex. Synthetic compounds derived from this tail region could therefore be used as a mimetic of the natural product, providing a range of designer compounds to treat actin-associated diseases or as probes to study actin polymerization.

  17. F-actin aggregates in transformed cells

    PubMed Central

    1981-01-01

    Polymerized actin has been found aggregated into distinctive patches inside transformed cells in culture. The F-actin-specific fluorescent probe, nitrobenzoxadiazole-phallacidin, labels these F-actin aggregates near the ventral cell surface of cells transformed by RNA or DNA tumor viruses, or by chemical mutagens, or spontaneously. Their appearance in all eight transformed cell types studied suggests their ubiquity and involvement in transformation morphology. Actin patches developed in normal rat kidney (NRK) cells transformed by a temperature-sensitive mutant of Rous sarcoma virus (LA23-NRK) within 30 min after a shift from the nonpermissive (39 degrees C) to the permissive temperature (32 degrees C). Patch appearance paralleling viral src gene expression tends to implicate pp60src kinase activity in destabilizing the cytoskeleton. However, appearance of the actin aggregates in cells not transformed by retrovirus calls for alternative mechanisms, perhaps involving an endogenous kinase, for this apparently common trait. PMID:6270163

  18. Xenopus egg cytoplasm with intact actin.

    PubMed

    Field, Christine M; Nguyen, Phuong A; Ishihara, Keisuke; Groen, Aaron C; Mitchison, Timothy J

    2014-01-01

    We report optimized methods for preparing Xenopus egg extracts without cytochalasin D, that we term "actin-intact egg extract." These are undiluted egg cytoplasm that contains abundant organelles, and glycogen which supplies energy, and represents the least perturbed cell-free cytoplasm preparation we know of. We used this system to probe cell cycle regulation of actin and myosin-II dynamics (Field et al., 2011), and to reconstitute the large, interphase asters that organize early Xenopus embryos (Mitchison et al., 2012; Wühr, Tan, Parker, Detrich, & Mitchison, 2010). Actin-intact Xenopus egg extracts are useful for analysis of actin dynamics, and interaction of actin with other cytoplasmic systems, in a cell-free system that closely mimics egg physiology, and more generally for probing the biochemistry and biophysics of the egg, zygote, and early embryo. Detailed protocols are provided along with assays used to check cell cycle state and tips for handling and storing undiluted egg extracts.

  19. Signalling Pathways Controlling Cellular Actin Organization.

    PubMed

    Steffen, Anika; Stradal, Theresia E B; Rottner, Klemens

    2017-01-01

    The actin cytoskeleton is essential for morphogenesis and virtually all types of cell shape changes. Reorganization is per definition driven by continuous disassembly and re-assembly of actin filaments, controlled by major, ubiquitously operating machines. These are specifically employed by the cell to tune its activities in accordance with respective environmental conditions or to satisfy specific needs.Here we sketch some fundamental signalling pathways established to contribute to the reorganization of specific actin structures at the plasma membrane. Rho-family GTPases are at the core of these pathways, and dissection of their precise contributions to actin reorganization in different cell types and tissues will thus continue to improve our understanding of these important signalling nodes. Furthermore, we will draw your attention to the emerging theme of actin reorganization on intracellular membranes, its functional relation to Rho-GTPase signalling, and its relevance for the exciting phenomenon autophagy.

  20. Inhibition of tobacco mosaic virus movement by expression of an actin-binding protein.

    PubMed

    Hofmann, Christina; Niehl, Annette; Sambade, Adrian; Steinmetz, André; Heinlein, Manfred

    2009-04-01

    The tobacco mosaic virus (TMV) movement protein (MP) required for the cell-to-cell spread of viral RNA interacts with the endoplasmic reticulum (ER) as well as with the cytoskeleton during infection. Whereas associations of MP with ER and microtubules have been intensely investigated, research on the role of actin has been rather scarce. We demonstrate that Nicotiana benthamiana plants transgenic for the actin-binding domain 2 of Arabidopsis (Arabidopsis thaliana) fimbrin (AtFIM1) fused to green fluorescent protein (ABD2:GFP) exhibit a dynamic ABD2:GFP-labeled actin cytoskeleton and myosin-dependent Golgi trafficking. These plants also support the movement of TMV. In contrast, both myosin-dependent Golgi trafficking and TMV movement are dominantly inhibited when ABD2:GFP is expressed transiently. Inhibition is mediated through binding of ABD2:GFP to actin filaments, since TMV movement is restored upon disruption of the ABD2:GFP-labeled actin network with latrunculin B. Latrunculin B shows no significant effect on the spread of TMV infection in either wild-type plants or ABD2:GFP transgenic plants under our treatment conditions. We did not observe any binding of MP along the length of actin filaments. Collectively, these observations demonstrate that TMV movement does not require an intact actomyosin system. Nevertheless, actin-binding proteins appear to have the potential to exert control over TMV movement through the inhibition of myosin-associated protein trafficking along the ER membrane.

  1. Integrity of the actin cytoskeleton of host macrophages is essential for Leishmania donovani infection.

    PubMed

    Roy, Saptarshi; Kumar, G Aditya; Jafurulla, Md; Mandal, Chitra; Chattopadhyay, Amitabha

    2014-08-01

    Visceral leishmaniasis is a vector-borne disease caused by an obligate intracellular protozoan parasite Leishmania donovani. The molecular mechanism involved in internalization of Leishmania is poorly understood. The entry of Leishmania involves interaction with the plasma membrane of host cells. We have previously demonstrated the requirement of host membrane cholesterol in the binding and internalization of L. donovani into macrophages. In the present work, we explored the role of the host actin cytoskeleton in leishmanial infection. We observed a dose-dependent reduction in the attachment of Leishmania promastigotes to host macrophages upon destabilization of the actin cytoskeleton by cytochalasin D. This is accompanied by a concomitant reduction in the intracellular amastigote load. We utilized a recently developed high resolution microscopy-based method to quantitate cellular F-actin content upon treatment with cytochalasin D. A striking feature of our results is that binding of Leishmania promastigotes and intracellular amastigote load show close correlation with cellular F-actin level. Importantly, the binding of Escherichia coli remained invariant upon actin destabilization of host cells, thereby implying specific involvement of the actin cytoskeleton in Leishmania infection. To the best of our knowledge, these novel results constitute the first comprehensive demonstration on the specific role of the host actin cytoskeleton in Leishmania infection. Our results could be significant in developing future therapeutic strategies to tackle leishmaniasis.

  2. LeftyA decreases Actin Polymerization and Stiffness in Human Endometrial Cancer Cells

    PubMed Central

    Salker, Madhuri S.; Schierbaum, Nicolas; Alowayed, Nour; Singh, Yogesh; Mack, Andreas F.; Stournaras, Christos; Schäffer, Tilman E.; Lang, Florian

    2016-01-01

    LeftyA, a cytokine regulating stemness and embryonic differentiation, down-regulates cell proliferation and migration. Cell proliferation and motility require actin reorganization, which is under control of ras-related C3 botulinum toxin substrate 1 (Rac1) and p21 protein-activated kinase 1 (PAK1). The present study explored whether LeftyA modifies actin cytoskeleton, shape and stiffness of Ishikawa cells, a well differentiated endometrial carcinoma cell line. The effect of LeftyA on globular over filamentous actin ratio was determined utilizing Western blotting and flow cytometry. Rac1 and PAK1 transcript levels were measured by qRT-PCR as well as active Rac1 and PAK1 by immunoblotting. Cell stiffness (quantified by the elastic modulus), cell surface area and cell volume were studied by atomic force microscopy (AFM). As a result, 2 hours treatment with LeftyA (25 ng/ml) significantly decreased Rac1 and PAK1 transcript levels and activity, depolymerized actin, and decreased cell stiffness, surface area and volume. The effect of LeftyA on actin polymerization was mimicked by pharmacological inhibition of Rac1 and PAK1. In the presence of the Rac1 or PAK1 inhibitor LeftyA did not lead to significant further actin depolymerization. In conclusion, LeftyA leads to disruption of Rac1 and Pak1 activity with subsequent actin depolymerization, cell softening and cell shrinkage. PMID:27404958

  3. Actin dynamics shape microglia effector functions.

    PubMed

    Uhlemann, Ria; Gertz, Karen; Boehmerle, Wolfgang; Schwarz, Tobias; Nolte, Christiane; Freyer, Dorette; Kettenmann, Helmut; Endres, Matthias; Kronenberg, Golo

    2016-06-01

    Impaired actin filament dynamics have been associated with cellular senescence. Microglia, the resident immune cells of the brain, are emerging as a central pathophysiological player in neurodegeneration. Microglia activation, which ranges on a continuum between classical and alternative, may be of critical importance to brain disease. Using genetic and pharmacological manipulations, we studied the effects of alterations in actin dynamics on microglia effector functions. Disruption of actin dynamics did not affect transcription of genes involved in the LPS-triggered classical inflammatory response. By contrast, in consequence of impaired nuclear translocation of phospho-STAT6, genes involved in IL-4 induced alternative activation were strongly downregulated. Functionally, impaired actin dynamics resulted in reduced NO secretion and reduced release of TNFalpha and IL-6 from LPS-stimulated microglia and of IGF-1 from IL-4 stimulated microglia. However, pathological stabilization of the actin cytoskeleton increased LPS-induced release of IL-1beta and IL-18, which belong to an unconventional secretory pathway. Reduced NO release was associated with decreased cytoplasmic iNOS protein expression and decreased intracellular arginine uptake. Furthermore, disruption of actin dynamics resulted in reduced microglia migration, proliferation and phagocytosis. Finally, baseline and ATP-induced [Ca(2+)]int levels were significantly increased in microglia lacking gelsolin, a key actin-severing protein. Together, the dynamic state of the actin cytoskeleton profoundly and distinctly affects microglia behaviours. Disruption of actin dynamics attenuates M2 polarization by inhibiting transcription of alternative activation genes. In classical activation, the role of actin remodelling is complex, does not relate to gene transcription and shows a major divergence between cytokines following conventional and unconventional secretion.

  4. LIM Kinase 1 Modulates Cortical Actin and CXCR4 Cycling and Is Activated by HIV-1 to Initiate Viral Infection*

    PubMed Central

    Vorster, Paul J.; Guo, Jia; Yoder, Alyson; Wang, Weifeng; Zheng, Yanfang; Xu, Xuehua; Yu, Dongyang; Spear, Mark; Wu, Yuntao

    2011-01-01

    Almost all viral pathogens utilize a cytoskeleton for their entry and intracellular transport. In HIV-1 infection, binding of the virus to blood resting CD4 T cells initiates a temporal course of cortical actin polymerization and depolymerization, a process mimicking the chemotactic response initiated from chemokine receptors. The actin depolymerization has been suggested to promote viral intracellular migration through cofilin-mediated actin treadmilling. However, the role of the virus-mediated actin polymerization in HIV infection is unknown, and the signaling molecules involved remain unidentified. Here we describe a pathogenic mechanism for triggering early actin polymerization through HIV-1 envelope-mediated transient activation of the LIM domain kinase (LIMK), a protein that phosphorylates cofilin. We demonstrate that HIV-mediated LIMK activation is through gp120-triggered transient activation of the Rack-PAK-LIMK pathway, and that knockdown of LIMK through siRNA decreases filamentous actin, increases CXCR4 trafficking, and diminishes viral DNA synthesis. These results suggest that HIV-mediated early actin polymerization may directly regulate the CXCR4 receptor during viral entry and is involved in viral DNA synthesis. Furthermore, we also demonstrate that in resting CD4 T cells, actin polymerization can be triggered through transient treatment with a pharmacological agent, okadaic acid, that activates LIMK and promotes HIV latent infection of resting CD4 T cells. Taken together, our results suggest that HIV hijacks LIMK to control the cortical actin dynamics for the initiation of viral infection of CD4 T cells. PMID:21321123

  5. Dynamics of an actin spring

    NASA Astrophysics Data System (ADS)

    Riera, Christophe; Mahadevan, L.; Shin, Jennifer; Matsudaira, Paul

    2003-03-01

    The acrosome of the sperm of the horseshoe crab (Limulus Polyphemus) is an unusual actin based system that shows a spectacular dynamical transition in the presence of Ca++ that is present in abundance in the neighborhood of the egg. During this process, the bundle, which is initially bent and twisted uncoils and becomes straight in a matter of a few seconds. Based on microstructural data, we propose a model for the dynamics of uncoiling that is best represented by a triple-well potential corresponding to the different structural arrangements of the supertwisted filaments. Each of the false, true and coiled states corresponds to a local minimum of the energy, with the true state being the one with the lowest energy. Using an evolution equation derived by balancing torques, we investigate the nucleation and propagation of the phase transition and compare the results with those of experiments. Our model quantifies the hypothesis that the acrosomal bundle behaves like a mechano-chemical spring.

  6. Actin from pig and rat uterus.

    PubMed Central

    Elce, J S; Elbrecht, A S; Middlestadt, M U; McIntyre, E J; Anderson, P J

    1981-01-01

    Smooth-muscle actin was isolated from pig uterus and from pregnant-rat uterus. Methods involving acetone-dried powders were unsuccessful, and a column-chromatographic procedure was developed, with proteinase inhibitors and avoiding polymerization as a purification step. The yield of pure actin was 0.8--1.5 mg/g wet wt. of uterus, which should be compared with an expected yield of actin from skeletal muscle of 2--4 mg/g wet wt. The actin was pure as judged by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, and exhibited alpha-, beta-, and gamma-forms on isoelectric focusing. It possessed a blocked N-terminal amino acid residue, and its amino acid analysis conformed to those of other actins. The rat uterine actin was available only in small amounts (5--10 mg) and did not polymerize. The pig uterine actin could be obtained in amounts up to 30 mg, polymerized reversibly, and activated a skeletal myosin Mg2+-dependent ATPase. Images Fig. 2. Fig. 4. PMID:6458278

  7. Reversible stress softening of actin networks

    PubMed Central

    Chaudhuri, Ovijit; Parekh, Sapun H.; Fletcher, Daniel A.

    2011-01-01

    The mechanical properties of cells play an essential role in numerous physiological processes. Organized networks of semiflexible actin filaments determine cell stiffness and transmit force during mechanotransduction, cytokinesis, cell motility and other cellular shape changes1–3. Although numerous actin-binding proteins have been identified that organize networks, the mechanical properties of actin networks with physiological architectures and concentrations have been difficult to measure quantitatively. Studies of mechanical properties in vitro have found that crosslinked networks of actin filaments formed in solution exhibit stress stiffening arising from the entropic elasticity of individual filaments or crosslinkers resisting extension4–8. Here we report reversible stress-softening behaviour in actin networks reconstituted in vitro that suggests a critical role for filaments resisting compression. Using a modified atomic force microscope to probe dendritic actin networks (like those formed in the lamellipodia of motile cells), we observe stress stiffening followed by a regime of reversible stress softening at higher loads. This softening behaviour can be explained by elastic buckling of individual filaments under compression that avoids catastrophic fracture of the network. The observation of both stress stiffening and softening suggests a complex interplay between entropic and enthalpic elasticity in determining the mechanical properties of actin networks. PMID:17230186

  8. Actin dynamics: old friends with new stories.

    PubMed

    Staiger, Christopher J; Blanchoin, Laurent

    2006-12-01

    Actin dynamics, or the rapid turnover of actin filaments, play a central role in numerous cellular processes. A large and diverse cast of characters, accessory proteins known as actin-binding proteins, modulate actin dynamics. They do this by binding to the monomer pool, interacting with the side and ends of filaments, creating breaks along a filament, and generating new filaments de novo. Recent biochemical and single-filament imaging analyses of several conserved classes of plant actin-binding proteins reveal unusual and unexpected properties. Examples that are highlighted in this review include: an abundant monomer-binding protein that catalyzes nucleotide exchange; a barbed-end capping protein that is dissociated from filament ends by the signaling lipid, phosphatidic acid; a villin-like bundling protein that lacks all Ca(2+)-regulated activities; and a formin family member that is non-processive and is sufficient to generate actin filament bundles. These and other stories motivate a careful description of the properties of plant proteins in vitro as a prelude to greater insight into the molecular mechanism(s) underlying the regulation of actin dynamics in vivo.

  9. Thymosin beta4: actin regulation and more.

    PubMed

    Yarmola, Elena G; Klimenko, Evguenia S; Fujita, Go; Bubb, Michael R

    2007-09-01

    The intracellular function of thymosin beta(4) is not limited to simple sequestration of globular actin. Our recent studies revealed that thymosin beta(4) affects actin critical concentration and forms a ternary complex with actin and profilin. The consequences of this complex formation can be very significant. Our new data demonstrate that it is likely that profilin affects binding of thymosin beta(4) to actin in the ternary complex through allosteric changes in actin rather than through competition for the binding site. The N- and C-terminal thymosin beta(4) helices are known to be unstructured in aqueous solution and to adopt helical conformation in organic solvents or upon binding to actin. Osmolytes stabilize protein structure, and TMAO (trimethylamine N-oxide) specifically stabilizes hydrogen bonds. This increases affinity of intact thymosin beta(4) to actin significantly, but the increase is much less for thymosin beta(4) sulfoxide. Our data show that oxidation does not alter binding of profilin to form a ternary complex, and therefore it is very likely that there is no direct steric interference by methionine 6 of thymosin beta(4). Rather, since TMAO has little effect on thymosin beta(4) sulfoxide, this observation is consistent with the hypothesis that methionine oxidation prevents helix transition. The experiment with truncated versions of thymosin beta(4) also supports this hypothesis. Oxidation and formation of the helices are important for both intra- and extracellular properties of thymosin beta(4). We found that actin and, in lesser extent, profilin-actin complex protect thymosin beta(4) from oxidation.

  10. Actin as a potential target for decavanadate.

    PubMed

    Ramos, Susana; Moura, José J G; Aureliano, Manuel

    2010-12-01

    ATP prevents G-actin cysteine oxidation and vanadyl formation specifically induced by decavanadate, suggesting that the oxometalate-protein interaction is affected by the nucleotide. The ATP exchange rate is increased by 2-fold due to the presence of decavanadate when compared with control actin (3.1×10(-3) s(-1)), and an apparent dissociation constant (k(dapp)) of 227.4±25.7 μM and 112.3±8.7 μM was obtained in absence or presence of 20 μM V(10), respectively. Moreover, concentrations as low as 50 μM of decameric vanadate species (V(10)) increases the relative G-actin intrinsic fluorescence intensity by approximately 80% whereas for a 10-fold concentration of monomeric vanadate (V(1)) no effects were observed. Upon decavanadate titration, it was observed a linear increase in G-actin hydrophobic surface (2.6-fold), while no changes were detected for V(1) (0-200 μM). Taken together, three major ideas arise: i) ATP prevents decavanadate-induced G-actin cysteine oxidation and vanadate reduction; ii) decavanadate promotes actin conformational changes resulting on its inactivation, iii) decavanadate has an effect on actin ATP binding site. Once it is demonstrated that actin is a new potential target for decavanadate, being the ATP binding site a suitable site for decavanadate binding, it is proposed that some of the biological effects of vanadate can be, at least in part, explained by decavanadate interactions with actin.

  11. Dynamic reorganization of the actin cytoskeleton

    PubMed Central

    Gressin, Laurène; Théry, Manuel; Blanchoin, Laurent

    2015-01-01

    Cellular processes, including morphogenesis, polarization, and motility, rely on a variety of actin-based structures. Although the biochemical composition and filament organization of these structures are different, they often emerge from a common origin. This is possible because the actin structures are highly dynamic. Indeed, they assemble, grow, and disassemble in a time scale of a second to a minute. Therefore, the reorganization of a given actin structure can promote the formation of another. Here, we discuss such transitions and illustrate them with computer simulations. PMID:26989473

  12. Actinic Granuloma with Focal Segmental Glomerulosclerosis

    PubMed Central

    Phasukthaworn, Ruedee; Chanprapaph, Kumutnart; Vachiramon, Vasanop

    2016-01-01

    Actinic granuloma is an uncommon granulomatous disease, characterized by annular erythematous plaque with central clearing predominately located on sun-damaged skin. The pathogenesis is not well understood, ultraviolet radiation is recognized as precipitating factor. We report a case of a 52-year-old woman who presented with asymptomatic annular erythematous plaques on the forehead and both cheeks persisting for 2 years. The clinical presentation and histopathologic findings support the diagnosis of actinic granuloma. During that period of time, she also developed focal segmental glomerulosclerosis. The association between actinic granuloma and focal segmental glomerulosclerosis needs to be clarified by further studies. PMID:27293392

  13. Actin-based propulsion of a microswimmer.

    PubMed

    Leshansky, A M

    2006-07-01

    A simple hydrodynamic model of actin-based propulsion of microparticles in dilute cell-free cytoplasmic extracts is presented. Under the basic assumption that actin polymerization at the particle surface acts as a force dipole, pushing apart the load and the free (nonanchored) actin tail, the propulsive velocity of the microparticle is determined as a function of the tail length, porosity, and particle shape. The anticipated velocities of the cargo displacement and the rearward motion of the tail are in good agreement with recently reported results of biomimetic experiments. A more detailed analysis of the particle-tail hydrodynamic interaction is presented and compared to the prediction of the simplified model.

  14. Confirmation of X-linked inheritance and provisional mapping of the keratosis follicularis spinulosa decalvans gene on Xp in a large Dutch family.

    PubMed

    Oosterwijk, J C; Nelen, M; Van Zandvoort, P M; Van Osch, L D; Oranje, A P; Wittebol-Post, D; Van Oost, B A

    1992-03-01

    In a large Dutch family with keratosis follicularis spinulosa decalvans (KFSD, MIM 308800), DNA linkage analysis was performed in order to locate the gene. Pedigree analysis and lod score calculation confirmed X-linked inheritance and revealed significant linkage to DNA markers on Xp. A maximum lod score of 5.70 at theta = 0.0 was obtained with DXS41 (p99.6). The KFSD gene is tentatively located on Xp21.2-p22.2.

  15. Phosphoinositide-specific phospholipase C in oat roots: association with the actin cytoskeleton.

    PubMed

    Huang, Chiung-Hua; Crain, Richard C

    2009-10-01

    Phosphoinositide-specific phospholipase C (PI-PLC) activities are involved in mediating plant cell responses to environmental stimuli. Two variants of PI-PLC have been partially purified from the roots of oat seedlings; one cytosolic and one particulate. Although the cytosolic enzyme was significantly purified, the activity still co-migrated with a number of other proteins on heparin HPLC and also on size-exclusion chromatography. The partially purified PI-PLC was tested by Western blotting, and we found that actin and actin-binding proteins, profilin and tropomyosin, co-purified with cytosolic phospholipase C. After a non-ionic detergent (Triton X-100) treatment, PI-PLC activities still remained with the actin cytoskeleton. The effects of phalloidin and F-buffer confirmed this association; these conditions, which favor actin polymerization, decreased the release of PI-PLC from the cytoskeleton. The treatments of latrunculin and G-buffer, the conditions that favor actin depolymerization, increased the release of PI-PLC from the cytoskeleton. These results suggest that oat PI-PLC associates with the actin cytoskeleton.

  16. Computational model of polarized actin cables and cytokinetic actin ring formation in budding yeast

    PubMed Central

    Tang, Haosu; Bidone, Tamara C.

    2015-01-01

    The budding yeast actin cables and contractile ring are important for polarized growth and division, revealing basic aspects of cytoskeletal function. To study these formin-nucleated structures, we built a 3D computational model with actin filaments represented as beads connected by springs. Polymerization by formins at the bud tip and bud neck, crosslinking, severing, and myosin pulling, are included. Parameter values were estimated from prior experiments. The model generates actin cable structures and dynamics similar to those of wild type and formin deletion mutant cells. Simulations with increased polymerization rate result in long, wavy cables. Simulated pulling by type V myosin stretches actin cables. Increasing the affinity of actin filaments for the bud neck together with reduced myosin V pulling promotes the formation of a bundle of antiparallel filaments at the bud neck, which we suggest as a model for the assembly of actin filaments to the contractile ring. PMID:26538307

  17. Tumor-Preferential Induction of Immune Responses and Epidermal Cell Death in Actinic Keratoses by Ingenol Mebutate

    PubMed Central

    Zibert, John R.; Schön, Margarete; Hald, Andreas; Hansen, Maria H.; Litman, Thomas; Schön, Michael P.

    2016-01-01

    The rapid and strong clinical efficacy of the first-in-class, ingenol mebutate, against actinic keratosis (AK) has resulted in its recent approval. We conducted the first comprehensive analysis of the cellular and molecular mode of action of topical ingenol mebutate 0.05% gel in both AK and uninvolved skin of 26 patients in a phase I, single-center, open-label, within-patient comparison. As early as 1 day after application, ingenol mebutate induced profound epidermal cell death, along with a strong infiltrate of CD4+ and CD8+ T-cells, neutrophils, and macrophages. Endothelial ICAM-1 activation became evident after 2 days. The reaction pattern was significantly more pronounced in AK compared with uninvolved skin, suggesting a tumor-preferential mode of action. Extensive molecular analyses and transcriptomic profiling of mRNAs and microRNAs demonstrated alterations in gene clusters functionally associated with epidermal development, inflammation, innate immunity, and response to wounding. Ingenol mebutate reveals a unique mode of action linking directly to anti-tumoral effects. Trial Registration: ClinicalTrials.gov NCT01387711 PMID:27612149

  18. Regulation of actin polymerization by tropomodulin-3 controls megakaryocyte actin organization and platelet biogenesis.

    PubMed

    Sui, Zhenhua; Nowak, Roberta B; Sanada, Chad; Halene, Stephanie; Krause, Diane S; Fowler, Velia M

    2015-07-23

    The actin cytoskeleton is important for platelet biogenesis. Tropomodulin-3 (Tmod3), the only Tmod isoform detected in platelets and megakaryocytes (MKs), caps actin filament (F-actin) pointed ends and binds tropomyosins (TMs), regulating actin polymerization and stability. To determine the function of Tmod3 in platelet biogenesis, we studied Tmod3(-/-) embryos, which are embryonic lethal by E18.5. Tmod3(-/-) embryos often show hemorrhaging at E14.5 with fewer and larger platelets, indicating impaired platelet biogenesis. MK numbers are moderately increased in Tmod3(-/-) fetal livers, with only a slight increase in the 8N population, suggesting that MK differentiation is not significantly affected. However, Tmod3(-/-) MKs fail to develop a normal demarcation membrane system (DMS), and cytoplasmic organelle distribution is abnormal. Moreover, cultured Tmod3(-/-) MKs exhibit impaired proplatelet formation with a wide range of proplatelet bud sizes, including abnormally large proplatelet buds containing incorrect numbers of von Willebrand factor-positive granules. Tmod3(-/-) MKs exhibit F-actin disturbances, and Tmod3(-/-) MKs spreading on collagen fail to polymerize F-actin into actomyosin contractile bundles. Tmod3 associates with TM4 and the F-actin cytoskeleton in wild-type MKs, and confocal microscopy reveals that Tmod3, TM4, and F-actin partially colocalize near the membrane of proplatelet buds. In contrast, the abnormally large proplatelets from Tmod3(-/-) MKs show increased F-actin and redistribution of F-actin and TM4 from the cortex to the cytoplasm, but normal microtubule coil organization. We conclude that F-actin capping by Tmod3 regulates F-actin organization in mouse fetal liver-derived MKs, thereby controlling MK cytoplasmic morphogenesis, including DMS formation and organelle distribution, as well as proplatelet formation and sizing.

  19. Structural Differences Explain Diverse Functions of Plasmodium Actins

    PubMed Central

    Vahokoski, Juha; Martinez, Silvia Muñico; Ignatev, Alexander; Lepper, Simone; Frischknecht, Friedrich; Sidén-Kiamos, Inga; Sachse, Carsten; Kursula, Inari

    2014-01-01

    Actins are highly conserved proteins and key players in central processes in all eukaryotic cells. The two actins of the malaria parasite are among the most divergent eukaryotic actins and also differ from each other more than isoforms in any other species. Microfilaments have not been directly observed in Plasmodium and are presumed to be short and highly dynamic. We show that actin I cannot complement actin II in male gametogenesis, suggesting critical structural differences. Cryo-EM reveals that Plasmodium actin I has a unique filament structure, whereas actin II filaments resemble canonical F-actin. Both Plasmodium actins hydrolyze ATP more efficiently than α-actin, and unlike any other actin, both parasite actins rapidly form short oligomers induced by ADP. Crystal structures of both isoforms pinpoint several structural changes in the monomers causing the unique polymerization properties. Inserting the canonical D-loop to Plasmodium actin I leads to the formation of long filaments in vitro. In vivo, this chimera restores gametogenesis in parasites lacking actin II, suggesting that stable filaments are required for exflagellation. Together, these data underline the divergence of eukaryotic actins and demonstrate how structural differences in the monomers translate into filaments with different properties, implying that even eukaryotic actins have faced different evolutionary pressures and followed different paths for developing their polymerization properties. PMID:24743229

  20. F-actin staining of Drosophila testes.

    PubMed

    Bonaccorsi, Silvia; Giansanti, Maria G; Cenci, Giovanni; Gatti, Maurizio

    2012-01-01

    Preparations of Drosophila testes fixed with paraformaldehyde can be stained for F-actin according to the protocol described here. This staining procedure is particularly suitable for staining the male fusome and the cytokinetic contractile ring.

  1. [Actin in the wound healing process].

    PubMed

    Nowak, Dorota; Popow-Woźniak, Agnieszka; Raźnikiewicz, Linda; Malicka-Błaszkiewicz, Maria

    2009-01-01

    Wound healing is an important biological process of crucial value for organisms survival and retention of its proper functions. The recognition of molecular mechanisms of these phenomenon is still under investigation. The transition of mesenchymal fibroblasts to myofibroblasts is a key point in wound healing. The contraction ability of myofibroblast enables the shrinkage of a wound and closes its edges. Alpha smooth muscle actin (alpha-SMA), one of six actin isoforms, is a marker of compeletely differentiated myofibroblast. The regulation of differentiation process depends on many growth factors (especially TGF beta 1), the level of active thymosin beta 4, extracellular matrix proteins--including fibronectin, and also on specificity of microenvironment. Thymosin beta 4 is responsible for maintenance of pool of monomeric actin and actin filaments depolymerization. It can also act as a transcription factor, migration stimulator and immunomodulator, so this protein deserves for more attention in wound healing research field.

  2. Mechanics model for actin-based motility

    NASA Astrophysics Data System (ADS)

    Lin, Yuan

    2009-02-01

    We present here a mechanics model for the force generation by actin polymerization. The possible adhesions between the actin filaments and the load surface, as well as the nucleation and capping of filament tips, are included in this model on top of the well-known elastic Brownian ratchet formulation. A closed form solution is provided from which the force-velocity relationship, summarizing the mechanics of polymerization, can be drawn. Model predictions on the velocity of moving beads driven by actin polymerization are consistent with experiment observations. This model also seems capable of explaining the enhanced actin-based motility of Listeria monocytogenes and beads by the presence of Vasodilator-stimulated phosphoprotein, as observed in recent experiments.

  3. Mechanics model for actin-based motility.

    PubMed

    Lin, Yuan

    2009-02-01

    We present here a mechanics model for the force generation by actin polymerization. The possible adhesions between the actin filaments and the load surface, as well as the nucleation and capping of filament tips, are included in this model on top of the well-known elastic Brownian ratchet formulation. A closed form solution is provided from which the force-velocity relationship, summarizing the mechanics of polymerization, can be drawn. Model predictions on the velocity of moving beads driven by actin polymerization are consistent with experiment observations. This model also seems capable of explaining the enhanced actin-based motility of Listeria monocytogenes and beads by the presence of Vasodilator-stimulated phosphoprotein, as observed in recent experiments.

  4. Actin binding domain of filamin distinguishes posterior from anterior actin filaments in migrating Dictyostelium cells

    PubMed Central

    Shibata, Keitaro; Nagasaki, Akira; Adachi, Hiroyuki; Uyeda, Taro Q. P.

    2016-01-01

    Actin filaments in different parts of a cell interact with specific actin binding proteins (ABPs) and perform different functions in a spatially regulated manner. However, the mechanisms of those spatially-defined interactions have not been fully elucidated. If the structures of actin filaments differ in different parts of a cell, as suggested by previous in vitro structural studies, ABPs may distinguish these structural differences and interact with specific actin filaments in the cell. To test this hypothesis, we followed the translocation of the actin binding domain of filamin (ABDFLN) fused with photoswitchable fluorescent protein (mKikGR) in polarized Dictyostelium cells. When ABDFLN-mKikGR was photoswitched in the middle of a polarized cell, photoswitched ABDFLN-mKikGR rapidly translocated to the rear of the cell, even though actin filaments were abundant in the front. The speed of translocation (>3 μm/s) was much faster than that of the retrograde flow of cortical actin filaments. Rapid translocation of ABDFLN-mKikGR to the rear occurred normally in cells lacking GAPA, the only protein, other than actin, known to bind ABDFLN. We suggest that ABDFLN recognizes a certain feature of actin filaments in the rear of the cell and selectively binds to them, contributing to the posterior localization of filamin.

  5. Cross-linking study on skeletal muscle actin: properties of suberimidate-treated actin.

    PubMed

    Ohara, O; Takahashi, S; Ooi, T; Fujiyoshi, Y

    1982-06-01

    Cross-linking experiments were performed on muscle skeletal actin, using imidoesters of various chain lengths. Chemical analyses on all products except one (derived from succinimidate) show evidence of the presence of intramolecular cross-links in the molecule. The detailed properties of suberimidate-treated actin (SA) are as follows: SA contains nearly 1 mol of intramolecular cross-link per mol of actin and less than 15% of intermolecularly cross-linked products. Even at a low salt concentration, SA is polymeric, exchanges slowly its bound nucleotide with free nucleotides in solution, and shows an F-actin-type CD spectrum. Electron micrographs of SA reveal that SA exists actually as fibrous polymers in solutions of low ionic strength, although the fibers seem to be less rigid than those at high salt concentration. The F-form of SA at a high salt concentration is indistinguishable from intact F-actin. SA can bind heavy meromyosin and activate the ATPase of heavy meromyosin as observed for intact F-actin. Tropomyosin binds SA only at a high salt concentration. These results show that SA possesses the properties of F-actin even in media of low salt concentration, which are favorable for depolymerization of F-actin. Thus, we may infer that the conformation of SA is frozen in the F-state of actin by the introduction of intramolecular cross-links in the protein.

  6. Cardiac actin is the major actin gene product in skeletal muscle cell differentiation in vitro.

    PubMed Central

    Bains, W; Ponte, P; Blau, H; Kedes, L

    1984-01-01

    We examined the expression of alpha-skeletal, alpha-cardiac, and beta- and gamma-cytoskeletal actin genes in a mouse skeletal muscle cell line (C2C12) during differentiation in vitro. Using isotype-specific cDNA probes, we showed that the alpha-skeletal actin mRNA pool reached only 15% of the level reached in adult skeletal muscle and required several days to attain this peak, which was then stably maintained. However, these cells accumulated a pool of alpha-cardiac actin six times higher than the alpha-skeletal actin mRNA peak within 24 h of the initiation of differentiation. After cells had been cultured for an additional 3 days, this pool declined to 10% of its peak level. In contrast, over 95% of the actin mRNA in adult skeletal muscle coded for alpha-actin. This suggests that C2C12 cells express a pattern of sarcomeric actin genes typical of either muscle development or regeneration and distinct from that seen in mature, adult tissue. Concurrently in the course of differentiation the beta- and gamma-cytoskeletal actin mRNA pools decreased to less than 10% of their levels in proliferating cells. The decreases in beta- and gamma-cytoskeletal actin mRNAs are apparently not coordinately regulated. Images PMID:6493226

  7. Actin-binding proteins take the reins in growth cones.

    PubMed

    Pak, Chi W; Flynn, Kevin C; Bamburg, James R

    2008-02-01

    Higher-order actin-based networks (actin superstructures) are important for growth-cone motility and guidance. Principles for generating, organizing and remodelling actin superstructures have emerged from recent findings in cell-free systems, non-neuronal cells and growth cones. This Review examines how actin superstructures are initiated de novo at the leading-edge membrane and how the spontaneous organization of actin superstructures is driven by ensembles of actin-binding proteins. How the regulation of actin-binding proteins can affect growth-cone turning and axonal regeneration is also discussed.

  8. Mechanism of Actin Filament Bundling by Fascin

    SciTech Connect

    Jansen, Silvia; Collins, Agnieszka; Yang, Changsong; Rebowski, Grzegorz; Svitkina, Tatyana; Dominguez, Roberto

    2013-03-07

    Fascin is the main actin filament bundling protein in filopodia. Because of the important role filopodia play in cell migration, fascin is emerging as a major target for cancer drug discovery. However, an understanding of the mechanism of bundle formation by fascin is critically lacking. Fascin consists of four {beta}-trefoil domains. Here, we show that fascin contains two major actin-binding sites, coinciding with regions of high sequence conservation in {beta}-trefoil domains 1 and 3. The site in {beta}-trefoil-1 is located near the binding site of the fascin inhibitor macroketone and comprises residue Ser-39, whose phosphorylation by protein kinase C down-regulates actin bundling and formation of filopodia. The site in {beta}-trefoil-3 is related by pseudo-2-fold symmetry to that in {beta}-trefoil-1. The two sites are {approx}5 nm apart, resulting in a distance between actin filaments in the bundle of {approx}8.1 nm. Residue mutations in both sites disrupt bundle formation in vitro as assessed by co-sedimentation with actin and electron microscopy and severely impair formation of filopodia in cells as determined by rescue experiments in fascin-depleted cells. Mutations of other areas of the fascin surface also affect actin bundling and formation of filopodia albeit to a lesser extent, suggesting that, in addition to the two major actin-binding sites, fascin makes secondary contacts with other filaments in the bundle. In a high resolution crystal structure of fascin, molecules of glycerol and polyethylene glycol are bound in pockets located within the two major actin-binding sites. These molecules could guide the rational design of new anticancer fascin inhibitors.

  9. Actin filament curvature biases branching direction

    NASA Astrophysics Data System (ADS)

    Wang, Evan; Risca, Viviana; Chaudhuri, Ovijit; Chia, Jia-Jun; Geissler, Phillip; Fletcher, Daniel

    2012-02-01

    Actin filaments are key components of the cellular machinery, vital for a wide range of processes ranging from cell motility to endocytosis. Actin filaments can branch, and essential in this process is a protein complex known as the Arp2/3 complex, which nucleate new ``daughter'' filaments from pre-existing ``mother'' filaments by attaching itself to the mother filament. Though much progress has been made in understanding the Arp2/3-actin junction, some very interesting questions remain. In particular, F-actin is a dynamic polymer that undergoes a wide range of fluctuations. Prior studies of the Arp2/3-actin junction provides a very static notion of Arp2/3 binding. The question we ask is how differently does the Arp2/3 complex interact with a straight filament compared to a bent filament? In this study, we used Monte Carlo simulations of a surface-tethered worm-like chain to explore possible mechanisms underlying the experimental observation that there exists preferential branch formation by the Arp2/3 complex on the convex face of a curved filament. We show that a fluctuation gating model in which Arp2/3 binding to the actin filament is dependent upon a rare high-local-curvature shape fluctuation of the filament is consistent with the experimental data.

  10. Actin Polymerization Is Essential for Pollen Tube GrowthV⃞

    PubMed Central

    Vidali, Luis; McKenna, Sylvester T.; Hepler, Peter K.

    2001-01-01

    Actin microfilaments, which are prominent in pollen tubes, have been implicated in the growth process; however, their mechanism of action is not well understood. In the present work we have used profilin and DNAse I injections, as well as latrunculin B and cytochalasin D treatments, under quantitatively controlled conditions, to perturb actin microfilament structure and assembly in an attempt to answer this question. We found that a ∼50% increase in the total profilin pool was necessary to half-maximally inhibit pollen tube growth, whereas a ∼100% increase was necessary for half-maximal inhibition of cytoplasmic streaming. DNAse I showed a similar inhibitory activity but with a threefold more pronounced effect on growth than streaming. Latrunculin B, at only 1–4 nM in the growth medium, has a similar proportion of inhibition of growth over streaming to that of profilin. The fact that tip growth is more sensitive than streaming to the inhibitory substances and that there is no correlation between streaming and growth rates suggests that tip growth requires actin assembly in a process independent of cytoplasmic streaming. PMID:11514633

  11. In Vitro Biochemical Characterization of Cytokinesis Actin-Binding Proteins.

    PubMed

    Zimmermann, Dennis; Morganthaler, Alisha N; Kovar, David R; Suarez, Cristian

    2016-01-01

    Characterizing the biochemical and biophysical properties of purified proteins is critical to understand the underlying molecular mechanisms that facilitate complicated cellular processes such as cytokinesis. Here we outline in vitro assays to investigate the effects of cytokinesis actin-binding proteins on actin filament dynamics and organization. We describe (1) multicolor single-molecule TIRF microscopy actin assembly assays, (2) "bulk" pyrene actin assembly/disassembly assays, and (3) "bulk" sedimentation actin filament binding and bundling assays.

  12. Arp2/3 complex inhibition radically alters lamellipodial actin architecture, suspended cell shape, and the cell spreading process

    PubMed Central

    Henson, John H.; Yeterian, Mesrob; Weeks, Richard M.; Medrano, Angela E.; Brown, Briana L.; Geist, Heather L.; Pais, Mollyann D.; Oldenbourg, Rudolf; Shuster, Charles B.

    2015-01-01

    Recent studies have investigated the dendritic actin cytoskeleton of the cell edge's lamellipodial (LP) region by experimentally decreasing the activity of the actin filament nucleator and branch former, the Arp2/3 complex. Here we extend these studies via pharmacological inhibition of the Arp2/3 complex in sea urchin coelomocytes, cells that possess an unusually broad LP region and display correspondingly exaggerated centripetal flow. Using light and electron microscopy, we demonstrate that Arp2/3 complex inhibition via the drug CK666 dramatically altered LP actin architecture, slowed centripetal flow, drove a lamellipodial-to-filopodial shape change in suspended cells, and induced a novel actin structural organization during cell spreading. A general feature of the CK666 phenotype in coelomocytes was transverse actin arcs, and arc generation was arrested by a formin inhibitor. We also demonstrate that CK666 treatment produces actin arcs in other cells with broad LP regions, namely fish keratocytes and Drosophila S2 cells. We hypothesize that the actin arcs made visible by Arp2/3 complex inhibition in coelomocytes may represent an exaggerated manifestation of the elongate mother filaments that could possibly serve as the scaffold for the production of the dendritic actin network. PMID:25568343

  13. Disruption of the actin cytoskeleton results in the promotion of gravitropism in inflorescence stems and hypocotyls of Arabidopsis

    NASA Technical Reports Server (NTRS)

    Yamamoto, Kazuyoshi; Kiss, John Z.

    2002-01-01

    The actin cytoskeleton is hypothesized to play a major role in gravity perception and transduction mechanisms in roots of plants. To determine whether actin microfilaments (MFs) are involved in these processes in stem-like organs, we studied gravitropism in Arabidopsis inflorescence stems and hypocotyls. Localization studies using Alexa Fluor-phalloidin in conjugation with confocal microscopy demonstrated a longitudinally and transversely oriented actin MF network in endodermal cells of stems and hypocotyls. Latrunculin B (Lat-B) treatment of hypocotyls caused depolymerization of actin MFs in endodermal cells and a significant reduction of hypocotyl growth rates. Actin MFs in Lat-B-treated inflorescence stems also were disrupted, but growth rates were not affected. Despite disruption of the actin cytoskeleton in these two organs, Lat-B-treated stems and hypocotyls exhibited a promotion of gravitropic curvature in response to reorientation. In contrast, Lat-B reduced gravitropic curvature in roots but also reduced the growth rate. Thus, in contrast to prevailing hypotheses, our results suggest that actin MFs are not a necessary component of gravitropism in inflorescence stems and hypocotyls. Furthermore, this is the first study to demonstrate a prominent actin MF network in endodermal cells in the putative gravity-perceiving cells in stems.

  14. Structure of a Longitudinal Actin Dimer Assembled by Tandem W Domains: Implications for Actin Filament Nucleation

    SciTech Connect

    Rebowski, Grzegorz; Namgoong, Suk; Boczkowska, Malgorzata; Leavis, Paul C.; Navaza, Jorge; Dominguez, Roberto

    2013-11-20

    Actin filament nucleators initiate polymerization in cells in a regulated manner. A common architecture among these molecules consists of tandem WASP homology 2 domains (W domains) that recruit three to four actin subunits to form a polymerization nucleus. We describe a low-resolution crystal structure of an actin dimer assembled by tandem W domains, where the first W domain is cross-linked to Cys374 of the actin subunit bound to it, whereas the last W domain is followed by the C-terminal pointed end-capping helix of thymosin {beta}4. While the arrangement of actin subunits in the dimer resembles that of a long-pitch helix of the actin filament, important differences are observed. These differences result from steric hindrance of the W domain with intersubunit contacts in the actin filament. We also determined the structure of the first W domain of Vibrio parahaemolyticus VopL cross-linked to actin Cys374 and show it to be nearly identical with non-cross-linked W-Actin structures. This result validates the use of cross-linking as a tool for the study of actin nucleation complexes, whose natural tendency to polymerize interferes with most structural methods. Combined with a biochemical analysis of nucleation, the structures may explain why nucleators based on tandem W domains with short inter-W linkers have relatively weak activity, cannot stay bound to filaments after nucleation, and are unlikely to influence filament elongation. The findings may also explain why nucleation-promoting factors of the Arp2/3 complex, which are related to tandem-W-domain nucleators, are ejected from branch junctions after nucleation. We finally show that the simple addition of the C-terminal pointed end-capping helix of thymosin {beta}4 to tandem W domains can change their activity from actin filament nucleation to monomer sequestration.

  15. Resemblance of actin-binding protein/actin gels to covalently crosslinked networks

    NASA Astrophysics Data System (ADS)

    Janmey, Paul A.; Hvidt, Søren; Lamb, Jennifer; Stossel, Thomas P.

    1990-05-01

    THE maintainance of the shape of cells is often due to their surface elasticity, which arises mainly from an actin-rich cytoplasmic cortex1,2. On locomotion, phagocytosis or fission, however, these cells become partially fluid-like. The finding of proteins that can bind to actin and control the assembly of, or crosslink, actin filaments, and of intracellular messages that regulate the activities of some of these actin-binding proteins, indicates that such 'gel sol' transformations result from the rearrangement of cortical actin-rich networks3. Alternatively, on the basis of a study of the mechanical properties of mixtures of actin filaments and an Acanthamoeba actin-binding protein, α-actinin, it has been proposed that these transformations can be accounted for by rapid exchange of crosslinks between actin filaments4: the cortical network would be solid when the deformation rate is greater than the rate of crosslink exchange, but would deform or 'creep' when deformation is slow enough to permit crosslinker molecules to rearrange. Here we report, however, that mixtures of actin filaments and actin-binding protein (ABP), an actin crosslinking protein of many higher eukaryotes, form gels Theologically equivalent to covalently crosslinked networks. These gels do not creep in response to applied stress on a time scale compatible with most cell-surface movements. These findings support a more complex and controlled mechanism underlying the dynamic mechanical properties of cortical cytoplasm, and can explain why cells do not collapse under the constant shear forces that often exist in tissues.

  16. Structure of a longitudinal actin dimer assembled by tandem w domains: implications for actin filament nucleation.

    PubMed

    Rebowski, Grzegorz; Namgoong, Suk; Boczkowska, Malgorzata; Leavis, Paul C; Navaza, Jorge; Dominguez, Roberto

    2010-10-15

    Actin filament nucleators initiate polymerization in cells in a regulated manner. A common architecture among these molecules consists of tandem WASP homology 2 domains (W domains) that recruit three to four actin subunits to form a polymerization nucleus. We describe a low-resolution crystal structure of an actin dimer assembled by tandem W domains, where the first W domain is cross-linked to Cys374 of the actin subunit bound to it, whereas the last W domain is followed by the C-terminal pointed end-capping helix of thymosin β4. While the arrangement of actin subunits in the dimer resembles that of a long-pitch helix of the actin filament, important differences are observed. These differences result from steric hindrance of the W domain with intersubunit contacts in the actin filament. We also determined the structure of the first W domain of Vibrio parahaemolyticus VopL cross-linked to actin Cys374 and show it to be nearly identical with non-cross-linked W-Actin structures. This result validates the use of cross-linking as a tool for the study of actin nucleation complexes, whose natural tendency to polymerize interferes with most structural methods. Combined with a biochemical analysis of nucleation, the structures may explain why nucleators based on tandem W domains with short inter-W linkers have relatively weak activity, cannot stay bound to filaments after nucleation, and are unlikely to influence filament elongation. The findings may also explain why nucleation-promoting factors of the Arp2/3 complex, which are related to tandem-W-domain nucleators, are ejected from branch junctions after nucleation. We finally show that the simple addition of the C-terminal pointed end-capping helix of thymosin β4 to tandem W domains can change their activity from actin filament nucleation to monomer sequestration.

  17. Actin dynamics in the regulation of endothelial barrier functions and neutrophil recruitment during endotoxemia and sepsis.

    PubMed

    Schnoor, Michael; García Ponce, Alexander; Vadillo, Eduardo; Pelayo, Rosana; Rossaint, Jan; Zarbock, Alexander

    2017-02-02

    Sepsis is a leading cause of death worldwide. Increased vascular permeability is a major hallmark of sepsis. Dynamic alterations in actin fiber formation play an important role in the regulation of endothelial barrier functions and thus vascular permeability. Endothelial integrity requires a delicate balance between the formation of cortical actin filaments that maintain endothelial cell contact stability and the formation of actin stress fibers that generate pulling forces, and thus compromise endothelial cell contact stability. Current research has revealed multiple molecular pathways that regulate actin dynamics and endothelial barrier dysfunction during sepsis. These include intracellular signaling proteins of the small GTPases family (e.g., Rap1, RhoA and Rac1) as well as the molecules that are directly acting on the actomyosin cytoskeleton such as myosin light chain kinase and Rho kinases. Another hallmark of sepsis is an excessive recruitment of neutrophils that also involves changes in the actin cytoskeleton in both endothelial cells and neutrophils. This review focuses on the available evidence about molecules that control actin dynamics and regulate endothelial barrier functions and neutrophil recruitment. We also discuss treatment strategies using pharmaceutical enzyme inhibitors to target excessive vascular permeability and leukocyte recruitment in septic patients.

  18. Actin depolymerization affects stress-induced translational activity of potato tuber tissue

    PubMed

    Morelli; Zhou; Yu; Lu; Vayda

    1998-04-01

    Changes in polymerized actin during stress conditions were correlated with potato (Solanum tuberosum L.) tuber protein synthesis. Fluorescence microscopy and immunoblot analyses indicated that filamentous actin was nearly undetectable in mature, quiescent aerobic tubers. Mechanical wounding of postharvest tubers resulted in a localized increase of polymerized actin, and microfilament bundles were visible in cells of the wounded periderm within 12 h after wounding. During this same period translational activity increased 8-fold. By contrast, low-oxygen stress caused rapid reduction of polymerized actin coincident with acute inhibition of protein synthesis. Treatment of aerobic tubers with cytochalasin D, an agent that disrupts actin filaments, reduced wound-induced protein synthesis in vivo. This effect was not observed when colchicine, an agent that depolymerizes microtubules, was used. Neither of these drugs had a significant effect in vitro on run-off translation of isolated polysomes. However, cytochalasin D did reduce translational competence in vitro of a crude cellular fraction containing both polysomes and cytoskeletal elements. These results demonstrate the dependence of wound-induced protein synthesis on the integrity of microfilaments and suggest that the dynamics of the actin cytoskeleton may affect translational activity during stress conditions.

  19. Yeast mitochondria contain ATP-sensitive, reversible actin-binding activity.

    PubMed Central

    Lazzarino, D A; Boldogh, I; Smith, M G; Rosand, J; Pon, L A

    1994-01-01

    Sedimentation assays were used to demonstrate and characterize binding of isolated yeast mitochondria to phalloidin-stabilized yeast F-actin. These actin-mitochondrial interactions are ATP sensitive, saturable, reversible, and do not depend upon mitochondrial membrane potential. Protease digestion of mitochondrial outer membrane proteins or saturation of myosin-binding sites on F-actin with the S1 subfragment of skeletal myosin block binding. These observations indicate that a protein (or proteins) on the mitochondrial surface mediates ATP-sensitive, reversible binding of mitochondria to the lateral surface of microfilaments. Actin copurifies with mitochondria during subcellular fractionation and is released from the organelle upon treatment with ATP. Thus, actin-mitochondrial interactions resembling those observed in vitro may also exist in intact yeast cells. Finally, a yeast mutant bearing a temperature-sensitive mutation in the actin-encoding ACT1 gene (act1-3) displays temperature-dependent defects in transfer of mitochondria from mother cells to newly developed buds during yeast cell mitosis. Images PMID:7812049

  20. Requirement of cortical actin organization for bombesin, endothelin, and EGF receptor internalization.

    PubMed

    Lunn, J A; Wong, H; Rozengurt, E; Walsh, J H

    2000-12-01

    The role of actin organization in occupancy-induced receptor internalization remains poorly defined. Here we report that treatment of mouse Swiss 3T3 cells with latrunculin A, a potent inhibitor of actin polymerization (including cortical actin), inhibited the internalization of the endogenous bombesin/gastrin-releasing peptide (GRP) receptor, as judged by uptake of (125)I-labeled GRP or fluorescent Cy3-labeled bombesin. In contrast, cells pretreated with cytochalasin D showed minimal inhibition of bombesin/GRP receptor internalization. Similarly, pretreatment of Swiss 3T3 cells with the potent Rho-kinase inhibitor HA-1077, at concentrations (10-20 microM) that abrogated bombesin-mediated stress fiber formation, did not significantly alter receptor-mediated internalization of (125)I-GRP. These results indicate that bombesin/GRP receptor internalization depends on latrunculin A-sensitive cortical actin rather than on rapidly turning over actin stress fibers that are disrupted by either cytochalasin D or HA-1077. The rates and total levels of internalization of the endogenously expressed endothelin A receptor and epidermal growth factor receptor were also markedly reduced by latrunculin A in Swiss 3T3 cells. The potency of latrunculin A for inhibiting G protein-coupled receptor endocytosis was comparable to that for reducing internalization of the epidermal growth factor tyrosine kinase receptor. We conclude that cortical actin structures, disrupted by latrunculin A, are necessary for occupancy-induced receptor internalization in animal cells.

  1. Rho-GTPase effector ROCK phosphorylates cofilin in actin-meditated cytokinesis during mouse oocyte meiosis.

    PubMed

    Duan, Xing; Liu, Jun; Dai, Xiao-Xin; Liu, Hong-Lin; Cui, Xiang-Shun; Kim, Nam-Hyung; Wang, Zhen-Bo; Wang, Qiang; Sun, Shao-Chen

    2014-02-01

    During oocyte meiosis, a spindle forms in the central cytoplasm and migrates to the cortex. Subsequently, the oocyte extrudes a small body and forms a highly polarized egg; this process is regulated primarily by actin. ROCK is a Rho-GTPase effector that is involved in various cellular functions, such as stress fiber formation, cell migration, tumor cell invasion, and cell motility. In this study, we investigated possible roles for ROCK in mouse oocyte meiosis. ROCK was localized around spindles after germinal vesicle breakdown and was colocalized with cytoplasmic actin and mitochondria. Disrupting ROCK activity by RNAi or an inhibitor resulted in cell cycle progression and polar body extrusion failure. Time-lapse microscopy showed that this may have been due to spindle migration and cytokinesis defects, as chromosomes segregated but failed to extrude a polar body and then realigned. Actin expression at oocyte membranes and in cytoplasm was significantly decreased after these treatments. Actin caps were also disrupted, which was confirmed by a failure to form cortical granule-free domains. The mitochondrial distribution was also disrupted, which indicated that mitochondria were involved in the ROCK-mediated actin assembly. In addition, the phosphorylation levels of Cofilin, a downstream molecule of ROCK, decreased after disrupting ROCK activity. Thus, our results indicated that a ROCK-Cofilin-actin pathway regulated meiotic spindle migration and cytokinesis during mouse oocyte maturation.

  2. Spontaneous oscillatory contraction without regulatory proteins in actin filament-reconstituted fibers.

    PubMed

    Fujita, H; Ishiwata, S

    1998-09-01

    Skinned skeletal and cardiac muscle fibers exhibits spontaneous oscillatory contraction (SPOC) in the presence of MgATP, MgADP, and inorganic phosphate (Pi)1 but the molecular mechanism underlying this phenomenon is not yet clear. We have investigated the role of regulatory proteins in SPOC using cardiac muscle fibers of which the actin filaments had been reconstituted without tropomyosin and troponin, according to a previously reported method (Fujita et al., 1996. Biophys. J. 71:2307-2318). That is, thin filaments in glycerinated cardiac muscle fibers were selectively removed by treatment with gelsolin. Then, by adding exogenous actin to these thin filament-free cardiac muscle fibers under polymerizing conditions, actin filaments were reconstituted. The actin filament-reconstituted cardiac muscle fibers generated active tension in a Ca(2+)-insensitive manner because of the lack of regulatory proteins. Herein we have developed a new solvent condition under which SPOC occurs, even in actin filament-reconstituted fibers: the coexistence of 2,3-butanedione 2-monoxime (BDM), a reversible inhibitor of actomyosin interactions, with MgATP, MgADP and Pi. The role of BDM in the mechanism of SPOC in the actin filament-reconstituted fibers was analogous to that of the inhibitory function of the tropomyosin-troponin complex (-Ca2+) in the control fibers. The present results suggest that SPOC is a phenomenon that is intrinsic to the actomyosin motor itself.

  3. Spontaneous oscillatory contraction without regulatory proteins in actin filament-reconstituted fibers.

    PubMed Central

    Fujita, H; Ishiwata, S

    1998-01-01

    Skinned skeletal and cardiac muscle fibers exhibits spontaneous oscillatory contraction (SPOC) in the presence of MgATP, MgADP, and inorganic phosphate (Pi)1 but the molecular mechanism underlying this phenomenon is not yet clear. We have investigated the role of regulatory proteins in SPOC using cardiac muscle fibers of which the actin filaments had been reconstituted without tropomyosin and troponin, according to a previously reported method (Fujita et al., 1996. Biophys. J. 71:2307-2318). That is, thin filaments in glycerinated cardiac muscle fibers were selectively removed by treatment with gelsolin. Then, by adding exogenous actin to these thin filament-free cardiac muscle fibers under polymerizing conditions, actin filaments were reconstituted. The actin filament-reconstituted cardiac muscle fibers generated active tension in a Ca(2+)-insensitive manner because of the lack of regulatory proteins. Herein we have developed a new solvent condition under which SPOC occurs, even in actin filament-reconstituted fibers: the coexistence of 2,3-butanedione 2-monoxime (BDM), a reversible inhibitor of actomyosin interactions, with MgATP, MgADP and Pi. The role of BDM in the mechanism of SPOC in the actin filament-reconstituted fibers was analogous to that of the inhibitory function of the tropomyosin-troponin complex (-Ca2+) in the control fibers. The present results suggest that SPOC is a phenomenon that is intrinsic to the actomyosin motor itself. PMID:9726945

  4. Neuroprotective effects of hypothermia on synaptic actin cytoskeletal changes induced by perinatal asphyxia.

    PubMed

    Muñiz, Javier; Romero, Juan; Holubiec, Mariana; Barreto, George; González, Janneth; Saint-Martin, Madeleine; Blanco, Eduardo; Carlos Cavicchia, Juan; Castilla, Rocío; Capani, Francisco

    2014-05-14

    Cerebral hypoxia-ischemia damages synaptic proteins, resulting in cytoskeletal alterations, protein aggregation and neuronal death. In the previous works, we have shown neuronal and synaptic changes in rat neostriatum subjected to hypoxia that leads to ubi-protein accumulation. Recently, we also showed that, changes in F-actin organization could be related to early alterations induced by hypoxia in the Central Nervous System. However, little is known about effective treatment to diminish the damage. The main aim of this work is to study the effects of birth hypothermia on the actin cytoskeleton of neostriatal post-synaptic densities (PSD) in 60 days olds rats by immunohistochemistry, photooxidation and western blot. We used 2 different protocols of hypothermia: (a) intrahypoxic hypothermia at 15°C and (b) post-hypoxia hypothermia at 32°C. Consistent with previous data at 30 days, staining with phalloidin-Alexa(488) followed by confocal microscopy analysis showed an increase of F-actin fluorescent staining in the neostriatum of hypoxic animals. Correlative photooxidation electron microscopy confirmed these observations showing an increment in the number of mushroom-shaped F-actin staining spines in neostriatal excitatory synapses in rats subjected to hypoxia. In addition, western blot revealed β-actin increase in PSDs in hypoxic animals. The optic relative density measurement showed a significant difference between controls and hypoxic animals. When hypoxia was induced under hypothermic conditions, the changes observed in actin cytoskeleton were blocked. Post-hypoxic hypothermia showed similar answer but actin cytoskeleton modifications were not totally reverted as we observed at 15°C. These data suggest that the decrease of the body temperature decreases the actin modifications in dendritic spines preventing the neuronal death.

  5. Quantitation of liquid-crystalline ordering in F-actin solutions.

    PubMed

    Coppin, C M; Leavis, P C

    1992-09-01

    Actin filaments (F-actin) are important determinants of cellular shape and motility. These functions depend on the collective organization of numerous filaments with respect to both position and orientation in the cytoplasm. Much of the orientational organization arises spontaneously through liquid crystal formation in concentrated F-actin solutions. In studying this phenomenon, we found that solutions of purified F-actin undergo a continuous phase transition, from the isotropic state to a liquid crystalline state, when either the mean filament length or the actin concentration is increased above its respective threshold value. The phase diagram representing the threshold filament lengths and concentrations at which the phase transition occurs is consistent with that predicted by Flory's theory on solutions of noninteracting, rigid cylinders (Flory, 1956b). However, in contrast to other predictions based on this model, we found no evidence for the coexistence of isotropic and anisotropic phases. Furthermore, the phase transition proved to be temperature dependent, which suggests the existence of orientation-dependent interfilament interactions or of a temperature-dependent filament flexibility. We developed a simple method for growing undistorted fluorescent acrylodan-labeled F-actin liquid crystals; and we derived a simple theoretical treatment by which polarization-of-fluorescence measurements could be used to quantitate, for the first time, the degree of spontaneous filament ordering (nematic order parameter) in these F-actin liquid crystals. This order parameter was found to increase monotonically with both filament length and concentration. Actin liquid crystals can readily become distorted by a process known as "texturing." Zigzaging and helicoidal liquid crystalline textures which persisted in the absence of ATP were observed through the polarizing microscope. Possible texturing mechanisms are discussed.

  6. Phosphoinositides regulate membrane-dependent actin assembly by latex bead phagosomes.

    PubMed

    Defacque, Hélène; Bos, Evelyne; Garvalov, Boyan; Barret, Cécile; Roy, Christian; Mangeat, Paul; Shin, Hye-Won; Rybin, Vladimir; Griffiths, Gareth

    2002-04-01

    Actin assembly on membrane surfaces is an elusive process in which several phosphoinositides (PIPs) have been implicated. We have reconstituted actin assembly using a defined membrane surface, the latex bead phagosome (LBP), and shown that the PI(4,5)P(2)-binding proteins ezrin and/or moesin were essential for this process (). Here, we provide several lines of evidence that both preexisting and newly synthesized PI(4,5)P(2), and probably PI(4)P, are essential for phagosomal actin assembly; only these PIPs were routinely synthesized from ATP during in vitro actin assembly. Treatment of LBP with phospholipase C or with adenosine, an inhibitor of type II PI 4-kinase, as well as preincubation with anti-PI(4)P or anti-PI(4,5)P(2) antibodies all inhibited this process. Incorporation of extra PI(4)P or PI(4,5)P(2) into the LBP membrane led to a fivefold increase in the number of phagosomes that assemble actin. An ezrin mutant mutated in the PI(4,5)P(2)-binding sites was less efficient in binding to LBPs and in reconstituting actin assembly than wild-type ezrin. Our data show that PI 4- and PI 5-kinase, and under some conditions also PI 3-kinase, activities are present on LBPs and can be activated by ATP, even in the absence of GTP or cytosolic components. However, PI 3-kinase activity is not required for actin assembly, because the process was not affected by PI 3-kinase inhibitors. We suggest that the ezrin-dependent actin assembly on the LBP membrane may require active turnover of D4 and D5 PIPs on the organelle membrane.

  7. Rat alveolar myofibroblasts acquire alpha-smooth muscle actin expression during bleomycin-induced pulmonary fibrosis.

    PubMed Central

    Vyalov, S. L.; Gabbiani, G.; Kapanci, Y.

    1993-01-01

    The majority of fibroblasts in alveolar septa are characterized by the presence of cytoplasmic bundles of microfilaments that contain cytoplasmic actin isoforms; these cells have been named contractile interstitial cells or V-type myofibroblasts. In the rat, they express desmin as intermediate filament protein. In this study, we explored the possibility that modulation and replication of such septal fibroblasts result in the appearance of alpha-smooth muscle (alpha-SM) actin-positive myofibroblasts, typical of lung fibrosis. Experimental pulmonary fibrosis was produced by a unique intratracheal instillation of bleomycin to 28 rats. Eight additional rats used as controls received the equivalent volume of saline. Paraffin and frozen sections of lungs were examined at days 1, 3, 5 and 7 after treatment. Microfilaments and intermediate filaments were stained using antibodies against total actin, alpha-SM actin, desmin, vimentin, keratin, and SM myosin. Electron microscopic labeling of desmin and alpha-SM actin using immunogold technique was done on Lowicryl K4M resin-embedded specimens. alpha-SM actin appeared in desmin-positive alveolar fibroblasts as early as 24 hours after intratracheal bleomycin instillation; the modulation of alpha-SM actin in these cells was preceded by a lymphomonocytic infiltration of alveolar septa. Twenty-four hours to 3 days after bleomycin administration, a proliferation of alveolar myofibroblasts occurred. Fibrosis with laying down of collagen fibers took place after the above mentioned cellular modifications. Our results support the view that septal fibroblastic cells can modulate into typical alpha-SM actin-containing myofibroblasts during experimental bleomycin-induced pulmonary fibrosis. In such a modulation a possible role of cytokines, particularly of transforming growth factor-beta, is considered. Images Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14

  8. Actin turnover-mediated gravity response in maize root apices: gravitropism of decapped roots implicates gravisensing outside of the root cap.

    PubMed

    Mancuso, Stefano; Barlow, Peter W; Volkmann, Dieter; Baluska, Frantisek

    2006-03-01

    The dynamic actin cytoskeleton has been proposed to be linked to gravity sensing in plants but the mechanistic understanding of these processes remains unknown. We have performed detailed pharmacological analyses of the role of the dynamic actin cytoskeleton in gravibending of maize (Zea mays) root apices. Depolymerization of actin filaments with two drugs having different mode of their actions, cytochalasin D and latrunculin B, stimulated root gravibending. By contrast, drug-induced stimulation of actin polymerization and inhibition of actin turnover, using two different agents phalloidin and jasplakinolide, compromised the root gravibending. Importantly, all these actin drugs inhibited root growth to similar extents suggesting that high actin turnover is essential for the gravity-related growth responses rather than for the general growth process. Both latrunculin B and cytochalasin D treatments inhibited root growth but restored gravibending of the decapped root apices, indicating that there is a strong potential for effective actin-mediated gravity sensing outside the cap. This elusive gravity sensing outside the root cap is dependent not only on the high rate of actin turnover but also on weakening of myosin activities, as general inhibition of myosin ATPases induced stimulation of gravibending of the decapped root apices. Collectively, these data provide evidence for the actin turnover-mediated gravity sensing outside the root cap.

  9. Genetic linkage evaluation of twenty-four loci in an eastern Canadian family segregating Darier’s disease (keratosis follicularis)

    PubMed Central

    Sidenberg, Deborah Gayle; Berg, Daniel; Bassett, Anne Susan; King, Nicole; Petronis, Arturas; Kamble, Arvind Baburao; Kennedy, James Lowery

    2011-01-01

    Background Darier’s disease (keratosis follicularis) is known to have a genetic cause as evidenced by its autosomal dominant transmission in families. The gene causing this disease has not been discovered. Objective During an ongoing linkage study of schizophrenia, a family segregating Darier’s disease was found. This family is being studied in an attempt to locate prospective regions that may contain the Darier’s disease gene. Methods Two genetic strategies are being employed: (1) testing candidate genes for the disorder and (2) scanning the entire genome with polymerase chain reaction–based microsatellite markers. Results Thirty-nine marker systems located on chromosomes 1, 2, 4, 5, 6, 9, 11, 12, 16, 17, 22, X, and Y have been genotyped. Slightly positive lod scores were achieved between six markers and Darier’s disease. The remaining 33 markers were nonsegregating or indeterminate, or revealed an obligate recombinant. Conclusion Linkage analysis can lead to localization of the gene causing Darier’s disease. In these preliminary studies low positive lod scores were obtained, potentially pointing to the chromosomal location of the Darier’s disease gene. PMID:8021367

  10. Time-resolved studies of actin organization by multivalent ions and actin-binding proteins

    NASA Astrophysics Data System (ADS)

    Hwee Lai, Ghee; Purdy, Kirstin; Bartles, James R.; Chee Lai Wong, Gerard

    2007-03-01

    Actin is one of the principal components in the eukaryotic cytoskeleton, the architecture of which is highly regulated for a wide range of biological functions. In the presence of multivalent salts or actin-binding proteins, it is known that F-actin can organize into bundles or networks. In this work, we use time-resolved confocal microscopy to study the dynamics of actin bundle growth induced by multivalent ions and by espin, a prototypical actin binding protein that is known to induce bundles. For divalent ion induced bundles, we observe a rapid lateral saturation followed by longitudinal growth of bundles, in sharp contrast to the bundling mechanism of espin, which favors finite length bundles.

  11. Arabidopsis ACTIN-DEPOLYMERIZING FACTOR7 Severs Actin Filaments and Regulates Actin Cable Turnover to Promote Normal Pollen Tube Growth[W

    PubMed Central

    Zheng, Yiyan; Xie, Yurong; Jiang, Yuxiang; Qu, Xiaolu; Huang, Shanjin

    2013-01-01

    Actin filaments are often arranged into higher-order structures, such as the longitudinal actin cables that generate the reverse fountain cytoplasmic streaming pattern present in pollen tubes. While several actin binding proteins have been implicated in the generation of these cables, the mechanisms that regulate their dynamic turnover remain largely unknown. Here, we show that Arabidopsis thaliana ACTIN-DEPOLYMERIZING FACTOR7 (ADF7) is required for turnover of longitudinal actin cables. In vitro biochemical analyses revealed that ADF7 is a typical ADF that prefers ADP-G-actin over ATP-G-actin. ADF7 inhibits nucleotide exchange on actin and severs filaments, but its filament severing and depolymerizing activities are less potent than those of the vegetative ADF1. ADF7 primarily decorates longitudinal actin cables in the shanks of pollen tubes. Consistent with this localization pattern, the severing frequency and depolymerization rate of filaments significantly decreased, while their maximum lifetime significantly increased, in adf7 pollen tube shanks. Furthermore, an ADF7–enhanced green fluorescent protein fusion with defective severing activity but normal G-actin binding activity could not complement adf7, providing compelling evidence that the severing activity of ADF7 is vital for its in vivo functions. These observations suggest that ADF7 evolved to promote turnover of longitudinal actin cables by severing actin filaments in pollen tubes. PMID:24058157

  12. Structure of the Rigor Actin-Tropomyosin-Myosin Complex

    PubMed Central

    Behrmann, Elmar; Müller, Mirco; Penczek, Pawel A.; Mannherz, Hans Georg; Manstein, Dietmar J.; Raunser, Stefan

    2014-01-01

    The interaction of myosin with actin filaments is the central feature of muscle contraction and cargo movement along actin filaments of the cytoskeleton. Myosin converts the chemical energy stored in ATP into force and movement along actin filaments. Myosin binding to actin induces conformational changes that are coupled to the nucleotide-binding pocket and amplified by a specialized region of the motor domain for efficient force generation. Tropomyosin plays a key role in regulating the productive interaction between myosins and actin. Here, we report the 8 Å resolution structure of the actin-tropomyosin-myosin complex determined by cryo electron microscopy. The pseudo-atomic model of the complex obtained from fitting crystal structures into the map defines the large actin-myosin-tropomyosin interface and the molecular interactions between the proteins in detail and allows us to propose a structural model for tropomyosin dependent myosin binding to actin and actin-induced nucleotide release from myosin. PMID:22817895

  13. The unusual dynamics of parasite actin result from isodesmic polymerization.

    PubMed

    Skillman, Kristen M; Ma, Christopher I; Fremont, Daved H; Diraviyam, Karthikeyan; Cooper, John A; Sept, David; Sibley, L David

    2013-01-01

    Previous reports have indicated that parasite actins are short and inherently unstable, despite being required for motility. Here we re-examine the polymerization properties of actin in Toxoplasma gondii, unexpectedly finding that it exhibits isodesmic polymerization in contrast to the conventional nucleation-elongation process of all previously studied actins from both eukaryotes and bacteria. Polymerization kinetics of actin in T. gondii lacks both a lag phase and critical concentration, normally characteristic of actins. Unique among actins, the kinetics of assembly can be fit with a single set of rate constants for all subunit interactions, without need for separate nucleation and elongation rates. This isodesmic model accurately predicts the assembly, disassembly and the size distribution of actin filaments in T. gondii in vitro, providing a mechanistic explanation for actin dynamics in vivo. Our findings expand the repertoire of mechanisms by which actin polymerization is governed and offer clues about the evolution of self-assembling, stabilized protein polymers.

  14. Sensing actin dynamics: Structural basis for G-actin-sensitive nuclear import of MAL

    SciTech Connect

    Hirano, Hidemi; Matsuura, Yoshiyuki

    2011-10-22

    Highlights: {yields} MAL has a bipartite NLS that binds to Imp{alpha} in an extended conformation. {yields} Mutational analyses verified the functional significance of MAL-Imp{alpha} interactions. {yields} Induced folding and NLS-masking by G-actins inhibit nuclear import of MAL. -- Abstract: The coordination of cytoskeletal actin dynamics with gene expression reprogramming is emerging as a crucial mechanism to control diverse cellular processes, including cell migration, differentiation and neuronal circuit assembly. The actin-binding transcriptional coactivator MAL (also known as MRTF-A/MKL1/BSAC) senses G-actin concentration and transduces Rho GTPase signals to serum response factor (SRF). MAL rapidly shuttles between the cytoplasm and the nucleus in unstimulated cells but Rho-induced depletion of G-actin leads to MAL nuclear accumulation and activation of transcription of SRF:MAL-target genes. Although the molecular and structural basis of actin-regulated nucleocytoplasmic shuttling of MAL is not understood fully, it is proposed that nuclear import of MAL is mediated by importin {alpha}/{beta} heterodimer, and that G-actin competes with importin {alpha}/{beta} for the binding to MAL. Here we present structural, biochemical and cell biological evidence that MAL has a classical bipartite nuclear localization signal (NLS) in the N-terminal 'RPEL' domain containing Arg-Pro-X-X-X-Glu-Leu (RPEL) motifs. The NLS residues of MAL adopt an extended conformation and bind along the surface groove of importin-{alpha}, interacting with the major- and minor-NLS binding sites. We also present a crystal structure of wild-type MAL RPEL domain in complex with five G-actins. Comparison of the importin-{alpha}- and actin-complexes revealed that the binding of G-actins to MAL is associated with folding of NLS residues into a helical conformation that is inappropriate for importin-{alpha} recognition.

  15. MARCKS actin-binding capacity mediates actin filament assembly during mitosis in human hepatic stellate cells.

    PubMed

    Rombouts, Krista; Mello, Tommaso; Liotta, Francesco; Galli, Andrea; Caligiuri, Alessandra; Annunziato, Francesco; Pinzani, Massimo

    2012-08-15

    Cross-linking between the actin cytoskeleton and plasma membrane actin-binding proteins is a key interaction responsible for the mechanical properties of the mitotic cell. Little is known about the identity, the localization, and the function of actin filament-binding proteins during mitosis in human hepatic stellate cells (hHSC). The aim of the present study was to identify and analyze the cross talk between actin and myristoylated alanine-rich kinase C substrate (MARCKS), an important PKC substrate and actin filament-binding protein, during mitosis in primary hHSC. Confocal analysis and chromosomal fraction analysis of mitotic hHSC demonstrated that phosphorylated (P)-MARCKS displays distinct phase-dependent localizations, accumulates at the perichromosomal layer, and is a centrosomal protein belonging to the chromosomal cytosolic fraction. Aurora B kinase (AUBK), an important mitotic regulator, β-actin, and P-MARCKS concentrate at the cytokinetic midbody during cleavage furrow formation. This localization is critical since MARCKS-depletion in hHSC is characterized by a significant loss in cytosolic actin filaments and cortical β-actin that induces cell cycle inhibition and dislocation of AUBK. A depletion of AUBK in hHSC affects cell cycle, resulting in multinucleation. Quantitative live cell imaging demonstrates that the actin filament-binding capacity of MARCKS is key to regulate mitosis since the cell cycle inhibitory effect in MARCKS-depleted cells caused abnormal cell morphology and an aberrant cytokinesis, resulting in a significant increase in cell cycle time. These findings implicate that MARCKS, an important PKC substrate, is essential for proper cytokinesis and that MARCKS and its partner actin are key mitotic regulators during cell cycle in hHSC.

  16. A case report of rare palmoplantar keratosis and nail dystrophy with imatinib.

    PubMed

    Benabbes, M; Tazi Mezalek, Z; Meddah, B

    2017-02-09

    A 48-year-old woman developed palmoplantar hyperkeratosis during treatment with imatinib (400mg/day) for treatment of chronic myeloid leukemia. After 5months of treatment, she developed plantar lesions with yellow-brownish plaques and palmar desquamations. The skin biopsy has eliminated psoriasis. Imatinib was discontinued, and treatment with an emollient balm and a soothing repair cream with an improvement of symptoms. A French imputability assessment score of I3 was obtained, indicating a probable relationship between the side effect and imatinib. In our case, the skin adverse events require definitive drug discontinuation and change of treatment.

  17. Regulation of Sodium Channel Activity by Capping of Actin Filaments

    PubMed Central

    Shumilina, Ekaterina V.; Negulyaev, Yuri A.; Morachevskaya, Elena A.; Hinssen, Horst; Khaitlina, Sofia Yu

    2003-01-01

    Ion transport in various tissues can be regulated by the cortical actin cytoskeleton. Specifically, involvement of actin dynamics in the regulation of nonvoltage-gated sodium channels has been shown. Herein, inside-out patch clamp experiments were performed to study the effect of the heterodimeric actin capping protein CapZ on sodium channel regulation in leukemia K562 cells. The channels were activated by cytochalasin-induced disruption of actin filaments and inactivated by G-actin under ionic conditions promoting rapid actin polymerization. CapZ had no direct effect on channel activity. However, being added together with G-actin, CapZ prevented actin-induced channel inactivation, and this effect occurred at CapZ/actin molar ratios from 1:5 to 1:100. When actin was allowed to polymerize at the plasma membrane to induce partial channel inactivation, subsequent addition of CapZ restored the channel activity. These results can be explained by CapZ-induced inhibition of further assembly of actin filaments at the plasma membrane due to the modification of actin dynamics by CapZ. No effect on the channel activity was observed in response to F-actin, confirming that the mechanism of channel inactivation does not involve interaction of the channel with preformed filaments. Our data show that actin-capping protein can participate in the cytoskeleton-associated regulation of sodium transport in nonexcitable cells. PMID:12686620

  18. Crystal structure of a nuclear actin ternary complex.

    PubMed

    Cao, Tingting; Sun, Lingfei; Jiang, Yuxiang; Huang, Shanjin; Wang, Jiawei; Chen, Zhucheng

    2016-08-09

    Actin polymerizes and forms filamentous structures (F-actin) in the cytoplasm of eukaryotic cells. It also exists in the nucleus and regulates various nucleic acid transactions, particularly through its incorporation into multiple chromatin-remodeling complexes. However, the specific structure of actin and the mechanisms that regulate its polymeric nature inside the nucleus remain unknown. Here, we report the crystal structure of nuclear actin (N-actin) complexed with actin-related protein 4 (Arp4) and the helicase-SANT-associated (HSA) domain of the chromatin remodeler Swr1. The inner face and barbed end of N-actin are sequestered by interactions with Arp4 and the HSA domain, respectively, which prevents N-actin from polymerization and binding to many actin regulators. The two major domains of N-actin are more twisted than those of globular actin (G-actin), and its nucleotide-binding pocket is occluded, freeing N-actin from binding to and regulation by ATP. These findings revealed the salient structural features of N-actin that distinguish it from its cytoplasmic counterpart and provide a rational basis for its functions and regulation inside the nucleus.

  19. Crystal structure of a nuclear actin ternary complex

    PubMed Central

    Cao, Tingting; Sun, Lingfei; Jiang, Yuxiang; Huang, Shanjin; Wang, Jiawei; Chen, Zhucheng

    2016-01-01

    Actin polymerizes and forms filamentous structures (F-actin) in the cytoplasm of eukaryotic cells. It also exists in the nucleus and regulates various nucleic acid transactions, particularly through its incorporation into multiple chromatin-remodeling complexes. However, the specific structure of actin and the mechanisms that regulate its polymeric nature inside the nucleus remain unknown. Here, we report the crystal structure of nuclear actin (N-actin) complexed with actin-related protein 4 (Arp4) and the helicase-SANT–associated (HSA) domain of the chromatin remodeler Swr1. The inner face and barbed end of N-actin are sequestered by interactions with Arp4 and the HSA domain, respectively, which prevents N-actin from polymerization and binding to many actin regulators. The two major domains of N-actin are more twisted than those of globular actin (G-actin), and its nucleotide-binding pocket is occluded, freeing N-actin from binding to and regulation by ATP. These findings revealed the salient structural features of N-actin that distinguish it from its cytoplasmic counterpart and provide a rational basis for its functions and regulation inside the nucleus. PMID:27457955

  20. The Actinome of Dictyostelium discoideum in Comparison to Actins and Actin-Related Proteins from Other Organisms

    PubMed Central

    Joseph, Jayabalan M.; Fey, Petra; Ramalingam, Nagendran; Liu, Xiao I.; Rohlfs, Meino; Noegel, Angelika A.; Müller-Taubenberger, Annette; Glöckner, Gernot; Schleicher, Michael

    2008-01-01

    Actin belongs to the most abundant proteins in eukaryotic cells which harbor usually many conventional actin isoforms as well as actin-related proteins (Arps). To get an overview over the sometimes confusing multitude of actins and Arps, we analyzed the Dictyostelium discoideum actinome in detail and compared it with the genomes from other model organisms. The D. discoideum actinome comprises 41 actins and actin-related proteins. The genome contains 17 actin genes which most likely arose from consecutive gene duplications, are all active, in some cases developmentally regulated and coding for identical proteins (Act8-group). According to published data, the actin fraction in a D. discoideum cell consists of more than 95% of these Act8-type proteins. The other 16 actin isoforms contain a conventional actin motif profile as well but differ in their protein sequences. Seven actin genes are potential pseudogenes. A homology search of the human genome using the most typical D. discoideum actin (Act8) as query sequence finds the major actin isoforms such as cytoplasmic beta-actin as best hit. This suggests that the Act8-group represents a nearly perfect actin throughout evolution. Interestingly, limited data from D. fasciculatum, a more ancient member among the social amoebae, show different relationships between conventional actins. The Act8-type isoform is most conserved throughout evolution. Modeling of the putative structures suggests that the majority of the actin-related proteins is functionally unrelated to canonical actin. The data suggest that the other actin variants are not necessary for the cytoskeleton itself but rather regulators of its dynamical features or subunits in larger protein complexes. PMID:18612387

  1. Actin and Myosin in Pea Tendrils 1

    PubMed Central

    Ma, Yong-Ze; Yen, Lung-Fei

    1989-01-01

    We demonstrate here the presence of actin and myosin in pea (Pisum sativum L.) tendrils. The molecular weight of tendril actin is 43,000, the same as rabbit skeletal muscle actin. The native molecular weight of tendril myosin is about 440,000. Tendril myosin is composed of two heavy chains of molecular weight approximately 165,000 and four (two pairs) light chains of 17,000 and 15,000. At high ionic strength, the ATPase activity of pea tendril myosin is activated by K+-EDTA and Ca2+ and is inhibited by Mg2+. At low ionic strength, the Mg2+-ATPase activity of pea tendril myosin is activated by rabbit skeletal muscle F-actin. Superprecipitation occurred after incubation at room temperature when ATP was added to the crude actomyosin extract. It is suggested that the interaction of actin and myosin may play a role in the coiling movement of pea tendril. Images Figure 1 Figure 3 Figure 4 PMID:16666586

  2. Antibodies to actin in autoimmune haemolytic anaemia

    PubMed Central

    2010-01-01

    Background In autoimmune haemolytic anaemia (AIHA), autoreactive antibodies directed against red blood cells are up-regulated, leading to erythrocyte death. Mycoplasma suis infections in pigs induce AIHA of both the warm and cold types. The aim of this study was to identify the target autoantigens of warm autoreactive IgG antibodies. Sera from experimentally M. suis-infected pigs were screened for autoreactivity. Results Actin-reactive antibodies were found in the sera of 95% of all animals tested. The reactivity was species-specific, i.e. reactivity with porcine actin was significantly higher than with rabbit actin. Sera of animals previously immunised with the M. suis adhesion protein MSG1 showed reactivity with actin prior to infection with M. suis indicating that molecular mimicry is involved in the specific autoreactive mechanism. A potentially cross-reactive epitope was detected. Conclusions This is the first report of autoreactive anti-actin antibodies involved in the pathogenesis of autoimmune haemolytic anaemia. PMID:20353574

  3. Dynamic buckling of actin within filopodia

    PubMed Central

    Leijnse, Natascha; Oddershede, Lene B; Bendix, Poul M

    2015-01-01

    Abstract Filopodia are active tubular structures protruding from the cell surface which allow the cell to sense and interact with the surrounding environment through repetitive elongation-retraction cycles. The mechanical behavior of filopodia has been studied by measuring the traction forces exerted on external substrates.1 These studies have revealed that internal actin flow can transduce a force across the cell surface through transmembrane linkers like integrins. In addition to the elongation-retraction behavior filopodia also exhibit a buckling and rotational behavior. Filopodial buckling in conjunction with rotation enables the cell to explore a much larger 3-dimensional space and allows for more complex, and possibly stronger, interactions with the external environment.2 Here we focus on how bending of the filopodial actin dynamically correlates with pulling on an optically trapped microsphere which acts like an external substrate attached to the filopodial tip. There is a clear correlation between presence of actin near the tip and exertion of a traction force, thus demonstrating that the traction force is transduced along the actin shaft inside the filopodium. By extending a filopodium and holding it while measuring the cellular response, we also monitor and analyze the waiting times for the first buckle observed in the fluorescently labeled actin shaft. PMID:26479403

  4. Tropomyosin-1 protects endothelial cell-cell junctions against cigarette smoke extract through F-actin stabilization in EA.hy926 cell line.

    PubMed

    Gagat, Maciej; Grzanka, Dariusz; Izdebska, Magdalena; Sroka, Wiktor Dariusz; Marszałł, Michał Piotr; Grzanka, Alina

    2014-05-01

    The aim of the study was to estimate the effect of cigarette smoke extract (CSE) on EA.hy926 endothelial cells in culture in the context of maintenance of cell-cell junctions through the structural stabilization of the actin cytoskeleton. In the present study, F-actin was stabilized by the overexpression of tropomyosin-1, which is known to stabilize actin filaments in muscle and non-muscle cells. Our study showed that the stabilization of F-actin significantly increased the survival of cells treated with 25% CSE. In addition, after stabilization of F-actin the migratory potential of EA.hy926 cells subjected to CSE treatment was increased. Our results also showed increased fluorescence intensity of alpha- and beta-catenin after CSE treatment in cells which had stabilized F-actin. Analysis of fluorescence intensity of Zonula occludens-1 did not reveal any significant differences when EA.hy926 cells overexpressing tropomyosin-1 were compared with those lacking overexpression. It would appear that overexpression of tropomyosin-1 preserved the structure of actin filaments in the cells treated with CSE. In conclusion, the present study demonstrates that stabilization of F-actin protects EA.hy926 cells against CSE-induced loss of both adherens and tight junctions. The data presented in this study suggest that overexpression of tropomyosin-1 stabilizes the organizational structure of actin filaments and helps preserve the endothelial barrier function under conditions of strong oxidative stress.

  5. A new F-actin structure in fungi: actin ring formation around the cell nucleus of Cryptococcus neoformans.

    PubMed

    Kopecká, Marie; Kawamoto, Susumu; Yamaguchi, Masashi

    2013-04-01

    The F-actin cytoskeleton of Cryptococcus neoformans is known to comprise actin cables, cortical patches and cytokinetic ring. Here, we describe a new F-actin structure in fungi, a perinuclear F-actin collar ring around the cell nucleus, by fluorescent microscopic imaging of rhodamine phalloidin-stained F-actin. Perinuclear F-actin rings form in Cryptococcus neoformans treated with the microtubule inhibitor Nocodazole or with the drug solvent dimethyl sulfoxide (DMSO) or grown in yeast extract peptone dextrose (YEPD) medium, but they are absent in cells treated with Latrunculin A. Perinuclear F-actin rings may function as 'funicular cabin' for the cell nucleus, and actin cables as intracellular 'funicular' suspending nucleus in the central position in the cell and moving nucleus along the polarity axis along actin cables.

  6. Recombinant alpha-actin for specific fluorescent labeling.

    PubMed

    Iwane, Atsuko H; Morimatsu, Masatoshi; Yanagida, Toshio

    2009-01-01

    Until recently, actin was thought to act merely as a passive track for its motility partner, myosin, during actomyosin interactions. Yet a recent report having observed dynamical conformational changes in labeled skeletal muscle alpha-actin suggests that actin has a more active role. Because the labeling technique was still immature, however, conclusions regarding the significance of the different conformations are difficult to make. Here, we describe the preparation of fully active alpha-actin obtained from a baculovirus expression system. We developed alpha-actin recombinants, of which subdomains 1 and 2 have specific sites for fluorescent probes. This specific labeling technique offers to significantly expand the information acquired from actin studies.

  7. Quantifying and localizing actin-free barbed ends in neutrophils.

    PubMed

    Glogauer, Michael

    2007-01-01

    We describe here a permeablization method that retains coupling between N-formylmethionyl-leucyl-phenylalanine (fMLP) receptor stimulation and barbed-end actin nucleation in neutrophils. Using fluorescently-tagged actin monomers, we are able to quantify and localize actin-free barbed ends generated downstream of chemoattractant receptors. Partial permeabilization of the neutrophils with the mild detergent n-octyl-beta-glucopyranoside maintains signaling from membrane receptor to the actin cytoskeleton while allowing for the introduction of inhibitors and activators of signal transduction pathways implicated in regulating actin cytoskeleton dynamics. This is a useful assay for studying signal transduction to the actin cytoskeleton in neutrophils.

  8. Selective chemical imaging of static actin in live cells.

    PubMed

    Milroy, Lech-Gustav; Rizzo, Stefano; Calderon, Abram; Ellinger, Bernhard; Erdmann, Silke; Mondry, Justine; Verveer, Peter; Bastiaens, Philippe; Waldmann, Herbert; Dehmelt, Leif; Arndt, Hans-Dieter

    2012-05-23

    We have characterized rationally designed and optimized analogues of the actin-stabilizing natural products jasplakinolide and chondramide C. Efficient actin staining was achieved in fixed permeabilized and non-permeabilized cells using different combinations of dye and linker length, thus highlighting the degree of molecular flexibility of the natural product scaffold. Investigations into synthetically accessible, non-toxic analogues have led to the characterization of a powerful cell-permeable probe to selectively image static, long-lived actin filaments against dynamic F-actin and monomeric G-actin populations in live cells, with negligible disruption of rapid actin dynamics.

  9. Structural Transitions of F-Actin:Espin Bundles

    NASA Astrophysics Data System (ADS)

    Purdy, Kirstin; Bartles, James; Wong, Gerard

    2006-03-01

    Espin is an actin bundling protein involved in the formation of the parallel bundles of filamentous actin in hair cell stereocilia. Mutations in espin are implicated in deafness phenotypes in mice and humans. We present measurements of the F-actin structures induced by wild type and by mutated espin obtained via small angle x-ray scattering and fluorescence microscopy. We found that wild type espin induced a paracrystalline hexagonal array of twisted F-actin, whereas the mutated espin only condensed the F-actin into a nematic-like phase. The possibility of coexisting nematic and bundled actin in mixtures containing both mutant and wild type espins was also investigated.

  10. Spontaneous actin dynamics in contractile rings

    NASA Astrophysics Data System (ADS)

    Kruse, Karsten; Wollrab, Viktoria; Thiagarajan, Raghavan; Wald, Anne; Riveline, Daniel

    Networks of polymerizing actin filaments are known to be capable to self-organize into a variety of structures. For example, spontaneous actin polymerization waves have been observed in living cells in a number of circumstances, notably, in crawling neutrophils and slime molds. During later stages of cell division, they can also spontaneously form a contractile ring that will eventually cleave the cell into two daughter cells. We present a framework for describing networks of polymerizing actin filaments, where assembly is regulated by various proteins. It can also include the effects of molecular motors. We show that the molecular processes driven by these proteins can generate various structures that have been observed in contractile rings of fission yeast and mammalian cells. We discuss a possible functional role of each of these patterns. The work was supported by Agence Nationale de la Recherche, France, (ANR-10-LABX-0030-INRT) and by Deutsche Forschungsgemeinschaft through SFB1027.

  11. Actin Out: Regulation of the Synaptic Cytoskeleton

    PubMed Central

    Spence, Erin F.; Soderling, Scott H.

    2015-01-01

    The small size of dendritic spines belies the elaborate role they play in excitatory synaptic transmission and ultimately complex behaviors. The cytoskeletal architecture of the spine is predominately composed of actin filaments. These filaments, which at first glance might appear simple, are also surprisingly complex. They dynamically assemble into different structures and serve as a platform for orchestrating the elaborate responses of the spine during spinogenesis and experience-dependent plasticity. Multiple mutations associated with human neurodevelopmental and psychiatric disorders involve genes that encode regulators of the synaptic cytoskeleton. A major, unresolved question is how the disruption of specific actin filament structures leads to the onset and progression of complex synaptic and behavioral phenotypes. This review will cover established and emerging mechanisms of actin cytoskeletal remodeling and how this influences specific aspects of spine biology that are implicated in disease. PMID:26453304

  12. Calcium Regulation of an Actin Spring

    PubMed Central

    Tam, Barney K.; Shin, Jennifer H.; Pfeiffer, Emily; Matsudaira, P.; Mahadevan, L.

    2009-01-01

    Abstract Calcium is essential for many biological processes involved in cellular motility. However, the pathway by which calcium influences motility, in processes such as muscle contraction and neuronal growth, is often indirect and complex. We establish a simple and direct mechanochemical link that shows how calcium quantitatively regulates the dynamics of a primitive motile system, the actin-based acrosomal bundle of horseshoe crab sperm. The extension of this bundle requires the continuous presence of external calcium. Furthermore, the extension rate increases with calcium concentration, but at a given concentration, we find that the volumetric rate of extension is constant. Our experiments and theory suggest that calcium sequentially binds to calmodulin molecules decorating the actin filaments. This binding leads to a collective wave of untwisting of the actin filaments that drives bundle extension. PMID:19686660

  13. Fluvoxamine, an anti-depressant, inhibits human glioblastoma invasion by disrupting actin polymerization.

    PubMed

    Hayashi, Keiichiro; Michiue, Hiroyuki; Yamada, Hiroshi; Takata, Katsuyoshi; Nakayama, Hiroki; Wei, Fan-Yan; Fujimura, Atsushi; Tazawa, Hiroshi; Asai, Akira; Ogo, Naohisa; Miyachi, Hiroyuki; Nishiki, Tei-ichi; Tomizawa, Kazuhito; Takei, Kohji; Matsui, Hideki

    2016-03-18

    Glioblastoma multiforme (GBM) is the most common malignant brain tumor with a median survival time about one year. Invasion of GBM cells into normal brain is the major cause of poor prognosis and requires dynamic reorganization of the actin cytoskeleton, which includes lamellipodial protrusions, focal adhesions, and stress fibers at the leading edge of GBM. Therefore, we hypothesized that inhibitors of actin polymerization can suppress GBM migration and invasion. First, we adopted a drug repositioning system for screening with a pyrene-actin-based actin polymerization assay and identified fluvoxamine, a clinically used antidepressant. Fluvoxamine, selective serotonin reuptake inhibitor, was a potent inhibitor of actin polymerization and confirmed as drug penetration through the blood-brain barrier (BBB) and accumulation of whole brain including brain tumor with no drug toxicity. Fluvoxamine inhibited serum-induced ruffle formation, cell migration, and invasion of human GBM and glioma stem cells in vitro by suppressing both FAK and Akt/mammalian target of rapamycin signaling. Daily treatment of athymic mice bearing human glioma-initiating cells with fluvoxamine blocked tumor cell invasion and prolonged the survival with almost same dose of anti-depressant effect. In conclusion, fluvoxamine is a promising anti-invasive treatment against GBM with reliable approach.

  14. Actin-binding proteins sensitively mediate F-actin bundle stiffness

    NASA Astrophysics Data System (ADS)

    Claessens, Mireille M. A. E.; Bathe, Mark; Frey, Erwin; Bausch, Andreas R.

    2006-09-01

    Bundles of filamentous actin (F-actin) form primary structural components of a broad range of cytoskeletal processes including filopodia, sensory hair cell bristles and microvilli. Actin-binding proteins (ABPs) allow the cell to tailor the dimensions and mechanical properties of the bundles to suit specific biological functions. Therefore, it is important to obtain quantitative knowledge on the effect of ABPs on the mechanical properties of F-actin bundles. Here we measure the bending stiffness of F-actin bundles crosslinked by three ABPs that are ubiquitous in eukaryotes. We observe distinct regimes of bundle bending stiffness that differ by orders of magnitude depending on ABP type, concentration and bundle size. The behaviour observed experimentally is reproduced quantitatively by a molecular-based mechanical model in which ABP shearing competes with F-actin extension/compression. Our results shed new light on the biomechanical function of ABPs and demonstrate how single-molecule properties determine mesoscopic behaviour. The bending mechanics of F-actin fibre bundles are general and have implications for cytoskeletal mechanics and for the rational design of functional materials.

  15. Multiple crystal structures of actin dimers and their implications for interactions in the actin filament

    PubMed Central

    Sawaya, Michael R.; Kudryashov, D. S.; Pashkov, Inna; Adisetiyo, Helty; Reisler, Emil; Yeates, Todd O.

    2008-01-01

    The structure of actin in its monomeric form is known at high resolution, while the structure of filamentous F-actin is only understood at considerably lower resolution. Knowing pre­cisely how the monomers of actin fit together would lead to a deeper understanding of the dynamic behavior of the actin filament. Here, a series of crystal structures of actin dimers are reported which were prepared by cross-linking in either the longitudinal or the lateral direction in the filament state. Laterally cross-linked dimers, comprised of monomers belonging to different protofilaments, are found to adopt configurations in crystals that are not related to the native structure of filamentous actin. In contrast, multiple structures of longitudinal dimers consistently reveal the same interface between monomers within a single protofilament. The re­appearance of the same longitudinal interface in multiple crystal structures adds weight to arguments that the interface visualized is similar to that in actin filaments. Highly conserved atomic interactions involving residues 199–205 and 287–291 are highlighted. PMID:18391412

  16. Actin: its cumbersome pilgrimage through cellular compartments

    PubMed Central

    Schleicher, Michael

    2008-01-01

    In this article, we follow the history of one of the most abundant, most intensely studied proteins of the eukaryotic cells: actin. We report on hallmarks of its discovery, its structural and functional characterization and localization over time, and point to present days’ knowledge on its position as a member of a large family. We focus on the rather puzzling number of diverse functions as proposed for actin as a dual compartment protein. Finally, we venture on some speculations as to its origin. PMID:18438682

  17. Actin Age Orchestrates Myosin-5 and Myosin-6 Runlengths

    PubMed Central

    Zimmermann, Dennis; Santos, Alicja; Kovar, David R.; Rock, Ronald S.

    2015-01-01

    Summary Unlike a static and immobile skeleton, the actin cytoskeleton is a highly dynamic network of filamentous actin (F-actin) polymers that continuously turn over. In addition to generating mechanical forces and sensing mechanical deformation, dynamic F-actin networks serve as cellular tracks for myosin motor traffic. However, much of our mechanistic understanding of processive myosins comes from in vitro studies where motility was studied on pre-assembled and artificially stabilized, static F-actin tracks. In this work, we examine the role of actin dynamics in single-molecule myosin motility using assembling F-actin and the two highly processive motors, myosin-5 and myosin-6. These two myosins have distinct functions in the cell and travel in opposite directions along actin filaments [1–3]. Myosin-5 walks towards the barbed ends of F-actin, traveling to sites of actin polymerization at the cell periphery [4]. Myosin-6 walks towards the pointed end of F-actin [5], traveling towards the cell center along older segments of the actin filament. We find that myosin-5 takes 1.3 to 1.5-fold longer runs on ADP•Pi (young) F-actin, while myosin-6 takes 1.7 to 3.6-fold longer runs along ADP (old) F-actin. These results suggest that conformational differences between ADP•Pi and ADP F-actin tailor these myosins to walk farther toward their preferred actin filament end. Taken together, these experiments define a new mechanism by which myosin traffic may sort to different F-actin networks depending on filament age. PMID:26190073

  18. Decavanadate interactions with actin: inhibition of G-actin polymerization and stabilization of decameric vanadate.

    PubMed

    Ramos, Susana; Manuel, Miguel; Tiago, Teresa; Duarte, Rui; Martins, Jorge; Gutiérrez-Merino, Carlos; Moura, José J G; Aureliano, Manuel

    2006-11-01

    Decameric vanadate species (V10) inhibit the rate and the extent of G-actin polymerization with an IC50 of 68+/-22 microM and 17+/-2 microM, respectively, whilst they induce F-actin depolymerization at a lower extent. On contrary, no effect on actin polymerization and depolymerization was detected for 2mM concentration of "metavanadate" solution that contains ortho and metavanadate species, as observed by combining kinetic with (51)V NMR spectroscopy studies. Although at 25 degrees C, decameric vanadate (10 microM) is unstable in the assay medium, and decomposes following a first-order kinetic, in the presence of G-actin (up to 8 microM), the half-life increases 5-fold (from 5 to 27 h). However, the addition of ATP (0.2mM) in the medium not only prevents the inhibition of G-actin polymerization by V10 but it also decreases the half-life of decomposition of decameric vanadate species from 27 to 10h. Decameric vanadate is also stabilized by the sarcoplasmic reticulum vesicles, which raise the half-life time from 5 to 18h whereas no effects were observed in the presence of phosphatidylcholine liposomes, myosin or G-actin alone. It is proposed that the "decavanadate" interaction with G-actin, favored by the G-actin polymerization, stabilizes decameric vanadate species and induces inhibition of G-actin polymerization. Decameric vanadate stabilization by cytoskeletal and transmembrane proteins can account, at least in part, for decavanadate toxicity reported in the evaluation of vanadium (V) effects in biological systems.

  19. Expression of cardiac alpha-actin spares extraocular muscles in skeletal muscle alpha-actin diseases--quantification of striated alpha-actins by MRM-mass spectrometry.

    PubMed

    Ravenscroft, Gianina; Colley, Stephen M J; Walker, Kendall R; Clement, Sophie; Bringans, Scott; Lipscombe, Richard; Fabian, Victoria A; Laing, Nigel G; Nowak, Kristen J

    2008-12-01

    As with many skeletal muscle diseases, the extraocular muscles (EOMs) are spared in skeletal muscle alpha-actin diseases, with no ophthalmoplegia even in severely affected patients. We hypothesised that the extraocular muscles sparing in these patients was due to significant expression of cardiac alpha-actin, the alpha-actin isoform expressed in heart and foetal skeletal muscle. We have shown by immunochemistry, Western blotting and a novel MRM-mass spectrometry technique, comparable levels of cardiac alpha-actin in the extraocular muscles of human, pig and sheep to those in the heart. The sparing of extraocular muscles in skeletal muscle alpha-actin disease is thus probably due to greater levels of cardiac alpha-actin, than the negligible amounts in skeletal muscles, diluting out the effects of the mutant skeletal muscle alpha-actin.

  20. Damage effects of protoporphyrin IX - sonodynamic therapy on the cytoskeletal F-actin of Ehrlich ascites carcinoma cells.

    PubMed

    Zhao, Xia; Liu, Quanhong; Tang, Wei; Wang, Xiaobing; Wang, Pan; Gong, Liyan; Wang, Yuan

    2009-01-01

    In this study, we report evidence of the damage effects of sonodynamic therapy (SDT) on a novel intracellular target, cytoskeletal F-actin, that has great importance for cancer treatment. Ehrlich ascites carcinoma (EAC) cells suspended in PBS were exposed to ultrasound at 1.34 MHz for up to 60s in the presence and absence of protoporphyrin IX (PPIX). To evaluate the polymeric state and distribution of actin filaments (AF) we employed FITC-Phalloidin staining. The percentage of cells with intact AF was decreased with 10-80 microM PPIX after ultrasonic exposure, while only few cells with disturbed F-actin were observed with 80 microM PPIX alone. The fluorescence intensity of FITC-Phalloidin labeled cells was detected by flow cytometry. The morphological changes of EAC cells were observed by scanning electron microscope (SEM). The nuclei were stained with Hoechst 33258 to determine apoptosis. Cytoskeletal F-actin and cell morphological changes were dependent on the time after SDT. Some cells suffered deformations of plasma membrane as blebs that reacted positively to FITC-Phalloidin at 2h after SDT treatment. Many of the cells showed the typically apoptotic chromatin fragmentation. The alterations were more significant 4h later. Our results showed that cytoskeletal F-actin might represent an important target for the SDT treatment and the observed effect on F-actin and the subsequent bleb formation mainly due to apoptosis formation due to the treatment.

  1. Enhanced Gravitropism of Roots with a Disrupted Cap Actin Cytoskeleton1

    PubMed Central

    Hou, Guichuan; Mohamalawari, Deepti R.; Blancaflor, Elison B.

    2003-01-01

    The actin cytoskeleton has been proposed to be a major player in plant gravitropism. However, understanding the role of actin in this process is far from complete. To address this problem, we conducted an analysis of the effect of Latrunculin B (Lat B), a potent actin-disrupting drug, on root gravitropism using various parameters that included detailed curvature kinetics, estimation of gravitropic sensitivity, and monitoring of curvature development after extended clinorotation. Lat B treatment resulted in a promotion of root curvature after a 90° reorientation in three plant species tested. More significantly, the sensitivity of maize (Zea mays) roots to gravity was enhanced after actin disruption, as determined from a comparison of presentation time of Lat B-treated versus untreated roots. A short 10-min gravistimulus followed by extended rotation on a 1-rpm clinostat resulted in extensive gravitropic responses, manifested as curvature that often exceeded 90°. Application of Lat B to the cap or elongation zone of maize roots resulted in the disruption of the actin cytoskeleton, which was confined to the area of localized Lat B application. Only roots with Lat B applied to the cap displayed the strong curvature responses after extended clinorotation. Our study demonstrates that disrupting the actin cytoskeleton in the cap leads to the persistence of a signal established by a previous gravistimulus. Therefore, actin could function in root gravitropism by providing a mechanism to regulate the proliferation of a gravitropic signal originating from the cap to allow the root to attain its correct orientation or set point angle. PMID:12644685

  2. Chlamydial TARP is a bacterial nucleator of actin.

    PubMed

    Jewett, Travis J; Fischer, Elizabeth R; Mead, David J; Hackstadt, Ted

    2006-10-17

    Chlamydia trachomatis entry into host cells results from a parasite-directed remodeling of the actin cytoskeleton. A type III secreted effector, TARP (translocated actin recruiting phosphoprotein), has been implicated in the recruitment of actin to the site of internalization. To elucidate the role of TARP in actin recruitment, we identified host cell proteins that associated with recombinant GST-TARP fusions. TARP directly associated with actin, and this interaction promoted actin nucleation as determined by in vitro polymerization assays. Domain analysis of TARP identified an actin-binding domain that bears structural and primary amino acid sequence similarity to WH2 domain family proteins. In addition, a proline-rich domain was found to promote TARP oligomerization and was required for TARP-dependent nucleation of new actin filaments. Our findings reveal a mechanism by which chlamydiae induce localized cytoskeletal changes by the translocated effector TARP during entry into host cells.

  3. Actin network architecture can determine myosin motor activity.

    PubMed

    Reymann, Anne-Cécile; Boujemaa-Paterski, Rajaa; Martiel, Jean-Louis; Guérin, Christophe; Cao, Wenxiang; Chin, Harvey F; De La Cruz, Enrique M; Théry, Manuel; Blanchoin, Laurent

    2012-06-08

    The organization of actin filaments into higher-ordered structures governs eukaryotic cell shape and movement. Global actin network size and architecture are maintained in a dynamic steady state through regulated assembly and disassembly. Here, we used experimentally defined actin structures in vitro to investigate how the activity of myosin motors depends on network architecture. Direct visualization of filaments revealed myosin-induced actin network deformation. During this reorganization, myosins selectively contracted and disassembled antiparallel actin structures, while parallel actin bundles remained unaffected. The local distribution of nucleation sites and the resulting orientation of actin filaments appeared to regulate the scalability of the contraction process. This "orientation selection" mechanism for selective contraction and disassembly suggests how the dynamics of the cellular actin cytoskeleton can be spatially controlled by actomyosin contractility.

  4. Microtubules as Platforms for Assaying Actin Polymerization In Vivo

    PubMed Central

    Oelkers, J. Margit; Vinzenz, Marlene; Nemethova, Maria; Jacob, Sonja; Lai, Frank P. L.; Block, Jennifer; Szczodrak, Malgorzata; Kerkhoff, Eugen; Backert, Steffen; Schlüter, Kai; Stradal, Theresia E. B.; Small, J. Victor

    2011-01-01

    The actin cytoskeleton is continuously remodeled through cycles of actin filament assembly and disassembly. Filaments are born through nucleation and shaped into supramolecular structures with various essential functions. These range from contractile and protrusive assemblies in muscle and non-muscle cells to actin filament comets propelling vesicles or pathogens through the cytosol. Although nucleation has been extensively studied using purified proteins in vitro, dissection of the process in cells is complicated by the abundance and molecular complexity of actin filament arrays. We here describe the ectopic nucleation of actin filaments on the surface of microtubules, free of endogenous actin and interfering membrane or lipid. All major mechanisms of actin filament nucleation were recapitulated, including filament assembly induced by Arp2/3 complex, formin and Spir. This novel approach allows systematic dissection of actin nucleation in the cytosol of live cells, its genetic re-engineering as well as screening for new modifiers of the process. PMID:21603613

  5. Arabidopsis Villins Promote Actin Turnover at Pollen Tube Tips and Facilitate the Construction of Actin Collars[W

    PubMed Central

    Qu, Xiaolu; Zhang, Hua; Xie, Yurong; Wang, Juan; Chen, Naizhi; Huang, Shanjin

    2013-01-01

    Apical actin filaments are crucial for pollen tube tip growth. However, the specific dynamic changes and regulatory mechanisms associated with actin filaments in the apical region remain largely unknown. Here, we have investigated the quantitative dynamic parameters that underlie actin filament growth and disappearance in the apical regions of pollen tubes and identified villin as the major player that drives rapid turnover of actin filaments in this region. Downregulation of Arabidopsis thaliana VILLIN2 (VLN2) and VLN5 led to accumulation of actin filaments at the pollen tube apex. Careful analysis of single filament dynamics showed that the severing frequency significantly decreased, and the lifetime significantly increased in vln2 vln5 pollen tubes. These results indicate that villin-mediated severing is critical for turnover and departure of actin filaments originating in the apical region. Consequently, the construction of actin collars was affected in vln2 vln5 pollen tubes. In addition to the decrease in severing frequency, actin filaments also became wavy and buckled in the apical cytoplasm of vln2 vln5 pollen tubes. These results suggest that villin confers rigidity upon actin filaments. Furthermore, an observed decrease in skewness of actin filaments in the subapical region of vln2 vln5 pollen tubes suggests that villin-mediated bundling activity may also play a role in the construction of actin collars. Thus, our data suggest that villins promote actin turnover at pollen tube tips and facilitate the construction of actin collars. PMID:23715472

  6. Localization of actin in Moloney murine leukemia virus by immunoelectron microscopy.

    PubMed

    Nermut, M V; Wallengren, K; Pager, J

    1999-07-20

    Immunoelectron microscopy was used to detect actin in wild-type (wt) Moloney murine leukemia virus (MoMuLV) and in virus-like particles (VLP) produced by recombinant Semliki Forest virus expressing only the MoMuLV gag polyprotein. Gold immunolabeling revealed the presence of actin on the surface of delipidized VLP and delipidized wt virus particles. Statistical evaluation of the number of colloidal gold particles per VLP revealed a large range of values and a prevalence of VLP with small numbers of gold particles. Labeling for actin was lost after prolonged treatment of VLP with 1% Nonidet-P40, high-pH buffer, or gelsolin. Gold immunolabeling with antibodies to gag proteins p15 (MA) and p12 and p30 (CA) was abundant and was not affected by treatment of VLP or wt virus with 1% Nonidet or gelsolin. VLP treated with a mixture of detergent and aldehyde fixatives showed more uniform and consistent labeling for actin than without fixatives. Negative staining or heavy metal shadowing revealed a globular surface of delipidized VLP. Stereomicrographs of gold-immunolabeled VLP showed that p15gag and p12gag were associated with the globular projections. Delipidized VLP were also well labeled with antibody to p30gag, which indicated that the gag shell permitted access of antibodies to p30gag and was therefore not a closely packed structure. Labeling for actin-binding proteins moesin and ezrin was negative in both the wt virus and the VLP. The absence of Gaussian distribution of actin in the sample of VLP suggests that actin is not a structural protein and its presence in MuLV virus particles may be fortuitous. This, however, does not rule out any possible role of actin in transport, assembly, budding, or release of virus particles, events which take place in the cytoplasm or at the plasma membrane. The site of actin in VLP is discussed in relation to the present knowledge of the molecular organization of the MuLV gag shell.

  7. Actin of Beta vulgaris seedlings under the clinorotation

    NASA Astrophysics Data System (ADS)

    Kozeko, L. Ye.

    We study the influence of altered gravity on actin expression in roots of Beta vulguris seedlings grown on the horizontal clinostat (2 rpm) from seed germination for three days. It is shown that the total actin quantity was not influenced. Three actin isoforms are revealed; a relative protein quantity of these isoforms was similar both in clinorotated seedlings and in ones grown in norm. This point to stable expression of actin under the altered gravity conditions.

  8. Actin-aggregating Cucurbitacins from Physocarpus capitatus

    PubMed Central

    Maloney, Katherine N.; Fujita, Masaki; Eggert, Ulrike S.; Schroeder, Frank C.; Field, Christine M.; Mitchison, Timothy J.; Clardy, Jon

    2009-01-01

    Bioassay-guided fractionation of Physocarpus capitatus yielded two new cucurbitacins (3 and 4) along with the known cucurbitacin F (1) and dihydrocucurbitacin F (2). Preliminary mechanism of action studies indicate that the cucurbitacins cause actin aggregates and inhibit cell division. PMID:18959442

  9. Genetics Home Reference: actin-accumulation myopathy

    MedlinePlus

    ... fibers and are important for muscle contraction. Attachment (binding) and release of the overlapping thick and thin filaments allows them to move relative to each other so that the muscles can contract. ACTA1 gene mutations that cause actin-accumulation myopathy ...

  10. Molecular Basis of Actin Nucleation Factor Cooperativity

    PubMed Central

    Zeth, Kornelius; Pechlivanis, Markos; Samol, Annette; Pleiser, Sandra; Vonrhein, Clemens; Kerkhoff, Eugen

    2011-01-01

    The distinct actin nucleation factors of the Spir and formin subgroup families cooperate in actin nucleation. The Spir/formin cooperativity has been identified to direct two essential steps in mammalian oocyte maturation, the asymmetric spindle positioning and polar body extrusion during meiosis. Understanding the nature and regulation of the Spir/Fmn cooperation is an important requirement to comprehend mammalian reproduction. Recently we dissected the structural elements of the Spir and Fmn family proteins, which physically link the two actin nucleation factors. The trans-regulatory interaction is mediated by the Spir kinase non-catalytic C-lobe domain (KIND) and the C-terminal formin Spir interaction motif (FSI). The interaction inhibits formin nucleation activity and enhances the Spir activity. To get insights into the molecular mechanism of the Spir/Fmn interaction, we determined the crystal structure of the KIND domain alone and in complex with the C-terminal Fmn-2 FSI peptide. Together they confirm the proposed structural homology of the KIND domain to the protein kinase fold and reveal the basis of the Spir/formin interaction. The complex structure showed a large interface with conserved and positively charged residues of the Fmn FSI peptide mediating major contacts to an acidic groove on the surface of KIND. Protein interaction studies verified the electrostatic nature of the interaction. The data presented here provide the molecular basis of the Spir/formin interaction and give a first structural view into the mechanisms of actin nucleation factor cooperativity. PMID:21705804

  11. Curvature and torsion in growing actin networks

    PubMed Central

    Shaevitz, Joshua W; Fletcher, Daniel A

    2011-01-01

    Intracellular pathogens such as Listeria monocytogenes and Rickettsia rickettsii move within a host cell by polymerizing a comet-tail of actin fibers that ultimately pushes the cell forward. This dense network of cross-linked actin polymers typically exhibits a striking curvature that causes bacteria to move in gently looping paths. Theoretically, tail curvature has been linked to details of motility by considering force and torque balances from a finite number of polymerizing filaments. Here we track beads coated with a prokaryotic activator of actin polymerization in three dimensions to directly quantify the curvature and torsion of bead motility paths. We find that bead paths are more likely to have low rather than high curvature at any given time. Furthermore, path curvature changes very slowly in time, with an autocorrelation decay time of 200 s. Paths with a small radius of curvature, therefore, remain so for an extended period resulting in loops when confined to two dimensions. When allowed to explore a three-dimensional (3D) space, path loops are less evident. Finally, we quantify the torsion in the bead paths and show that beads do not exhibit a significant left- or right-handed bias to their motion in 3D. These results suggest that paths of actin-propelled objects may be attributed to slow changes in curvature, possibly associated with filament debranching, rather than a fixed torque. PMID:18560043

  12. Curvature and torsion in growing actin networks

    NASA Astrophysics Data System (ADS)

    Shaevitz, Joshua W.; Fletcher, Daniel A.

    2008-06-01

    Intracellular pathogens such as Listeria monocytogenes and Rickettsia rickettsii move within a host cell by polymerizing a comet-tail of actin fibers that ultimately pushes the cell forward. This dense network of cross-linked actin polymers typically exhibits a striking curvature that causes bacteria to move in gently looping paths. Theoretically, tail curvature has been linked to details of motility by considering force and torque balances from a finite number of polymerizing filaments. Here we track beads coated with a prokaryotic activator of actin polymerization in three dimensions to directly quantify the curvature and torsion of bead motility paths. We find that bead paths are more likely to have low rather than high curvature at any given time. Furthermore, path curvature changes very slowly in time, with an autocorrelation decay time of 200 s. Paths with a small radius of curvature, therefore, remain so for an extended period resulting in loops when confined to two dimensions. When allowed to explore a three-dimensional (3D) space, path loops are less evident. Finally, we quantify the torsion in the bead paths and show that beads do not exhibit a significant left- or right-handed bias to their motion in 3D. These results suggest that paths of actin-propelled objects may be attributed to slow changes in curvature, possibly associated with filament debranching, rather than a fixed torque.

  13. EPLIN: a fundamental actin regulator in cancer metastasis?

    PubMed

    Collins, Ross J; Jiang, Wen G; Hargest, Rachel; Mason, Malcolm D; Sanders, Andrew J

    2015-12-01

    Treatment of malignant disease is of paramount importance in modern medicine. In 2012, it was estimated that 162,000 people died from cancer in the UK which illustrates a fundamental problem. Traditional treatments for cancer have various drawbacks, and this creates a considerable need for specific, molecular targets to overcome cancer spread. Epithelial protein lost in neoplasm (EPLIN) is an actin-associated molecule which has been implicated in the development and progression of various cancers including breast, prostate, oesophageal and lung where EPLIN expression is frequently lost as the cancer progresses. EPLIN is important in the regulation of actin dynamics and has multiple associations at epithelial cells junctions. Thus, EPLIN loss in cancer may have significant effects on cancer cell migration and invasion, increasing metastatic potential. Overexpression of EPLIN has proved to be an effective tool for manipulating cancerous traits such as reducing cell growth and cell motility and rendering cells less invasive illustrating the therapeutic potential of EPLIN. Here, we review the current state of knowledge of EPLIN, highlighting EPLIN involvement in regulating cytoskeletal dynamics, signalling pathways and implications in cancer and metastasis.

  14. Actin cytoskeleton demonstration in Trichomonas vaginalis and in other trichomonads.

    PubMed

    Brugerolle, G; Bricheux, G; Coffe, G

    1996-01-01

    The flagellate form of Trichomonas vaginalis (T v) transforms to amoeboid cells upon adherence to converslips. They grow and their nuclei divide without undergoing cytokinesis, yielding giant cells and a monolayer of T v F-actin was demonstrated in Trichomonas vaginalis by fluorescence microscopy using phalloidin and an anti-actin mAb which labelled the cytoplasm of both the flagellate and amoeboid forms. Comparative electrophoresis and immunoblotting established that the actin band has the same 42 kDa as muscle actin, but 2-D electrophoresis resolved the actin band into four spots; the two major spots observed were superimposable with major muscle actin isoforms. Electron microscopy demonstrated an ectoplasmic microfibrillar layer along the adhesion zone of amoeboid T v adhering to coverslips. Immunogold staining, using anti-actin monoclonal antibodies demonstrated that this layer was mainly composed of actin microfilaments. A comparative immunoblotting study comprising seven trichomonad species showed that all trichomonads studied expressed actin. The mAb Sigma A-4700 specific for an epitope on the actin C-terminal sequence labelled only actin of Trichomonas vaginalis, Tetratrichomonas gallinarum. Trichomitus batrachorum and Hypotrichomonas acosta, but not the actin of Tritrichomonas foetus, Tritrichomonas augusta and Monocercomonas sp. This discrimination between a 'trichomonas branch' and a 'tritrichomonas branch' is congruent with inferred sequence phylogeny from SSu rRNA and with classical phylogeny of trichomonads.

  15. Functional synergy of actin filament cross-linking proteins.

    PubMed

    Tseng, Yiider; Schafer, Benjamin W; Almo, Steven C; Wirtz, Denis

    2002-07-12

    The organization of filamentous actin (F-actin) in resilient networks is coordinated by various F-actin cross-linking proteins. The relative tolerance of cells to null mutations of genes that code for a single actin cross-linking protein suggests that the functions of those proteins are highly redundant. This apparent functional redundancy may, however, reflect the limited resolution of available assays in assessing the mechanical role of F-actin cross-linking/bundling proteins. Using reconstituted F-actin networks and rheological methods, we demonstrate how alpha-actinin and fascin, two F-actin cross-linking/bundling proteins that co-localize along stress fibers and in lamellipodia, could synergistically enhance the resilience of F-actin networks in vitro. These two proteins can generate microfilament arrays that "yield" at a strain amplitude that is much larger than each one of the proteins separately. F-actin/alpha-actinin/fascin networks display strain-induced hardening, whereby the network "stiffens" under shear deformations, a phenomenon that is non-existent in F-actin/fascin networks and much weaker in F-actin/alpha-actinin networks. Strain-hardening is further enhanced at high rates of deformation and high concentrations of actin cross-linking proteins. A simplified model suggests that the optimum results of the competition between the increased stiffness of bundles and their decreased density of cross-links. Our studies support a re-evaluation of the notion of functional redundancy among cytoskeletal regulatory proteins.

  16. Prostaglandins temporally regulate cytoplasmic actin bundle formation during Drosophila oogenesis.

    PubMed

    Spracklen, Andrew J; Kelpsch, Daniel J; Chen, Xiang; Spracklen, Cassandra N; Tootle, Tina L

    2014-02-01

    Prostaglandins (PGs)--lipid signals produced downstream of cyclooxygenase (COX) enzymes--regulate actin dynamics in cell culture and platelets, but their roles during development are largely unknown. Here we define a new role for Pxt, the Drosophila COX-like enzyme, in regulating the actin cytoskeleton--temporal restriction of actin remodeling during oogenesis. PGs are required for actin filament bundle formation during stage 10B (S10B). In addition, loss of Pxt results in extensive early actin remodeling, including actin filaments and aggregates, within the posterior nurse cells of S9 follicles; wild-type follicles exhibit similar structures at a low frequency. Hu li tai shao (Hts-RC) and Villin (Quail), an actin bundler, localize to all early actin structures, whereas Enabled (Ena), an actin elongation factor, preferentially localizes to those in pxt mutants. Reduced Ena levels strongly suppress early actin remodeling in pxt mutants. Furthermore, loss of Pxt results in reduced Ena localization to the sites of bundle formation during S10B. Together these data lead to a model in which PGs temporally regulate actin remodeling during Drosophila oogenesis by controlling Ena localization/activity, such that in S9, PG signaling inhibits, whereas at S10B, it promotes Ena-dependent actin remodeling.

  17. Synthetic actin-binding domains reveal compositional constraints for function.

    PubMed

    Lorenzi, Maria; Gimona, Mario

    2008-01-01

    The actin-binding domains of many proteins consist of a canonical type 1/type 2 arrangement of the structurally conserved calponin homology domain. Using the actin-binding domain of alpha-actinin-1 as a scaffold we have generated synthetic actin-binding domains by altering position and composition of the calponin homology domains. We show that the presence of two calponin homology domains alone and in the context of an actin-binding domain is not sufficient for actin-binding, and that both single and homotypic type 2 calponin homology domain tandems fail to bind to actin in vitro and in transfected cells. In contrast, single and tandem type 1 calponin homology domain arrays bind actin directly but result in defective turnover rates on actin filaments, and in aberrant actin bundling when introduced into the full-length alpha-actinin molecule. An actin-binding domain harboring the calponin homology domains in an inverted position, however, functions both in isolation and in the context of the dimeric alpha-actinin molecule. Our data demonstrate that the dynamics and specificity of actin-binding via actin-binding domains requires both the filament binding properties of the type 1, and regulation by type 2 calponin homology domains, and appear independent of their position.

  18. Actin organization in chick embryo fibroblasts after influenza virus infection. I. Isolation and characterization of actin from chick embryo cells.

    PubMed

    Krizanová, O; Závodská, E; Solariková, L; Ciampor, F; Kocisková, D

    1984-05-01

    Comparison of two starting materials for actin purification has shown that preparation of actin from aceton-dried cytoskeleton was more effective than from native chick embryos (CE). The isolated actin formed a single band of Mr = 42-43000 in SDS-PAGE; less purified samples revealed additional faint bands. G form of actin (non-polymerized) inhibited the activity of DNase I, electron microscopy showed actin filaments and bundles formed upon its polymerization. The freshly purified homogeneous actin has not lost its DNase I-inhibiting activity when incubated for 60 min at 35 degrees or 45 degrees C. Older or less purified actin samples kept under similar conditions showed 18-25% decrease of their DNase I-inhibiting activity and a loss of their polymerization ability. Digestion with trypsin caused a decrease of DNase I-inhibiting activity of fresh as well as for older actin samples.

  19. Lichen Planus-like Keratosis: Another Differential Diagnosis for Kaposi Sarcoma

    PubMed Central

    Clavellina-Miller, Marcela; Moreno-Coutiño, Gabriela; Toussaint-Caire, Sonia; Reyes-Terán, Gustavo

    2015-01-01

    Epidemic Kaposi sarcoma is a common finding among HIV/AIDS patients that are not under antiretroviral treatment, and sometimes it is the first sign of the disease. However, it can be seen even in patients with undetectable viral load and high CD 4 cell count. Under these circumstances, the clinical presentation can be atypical in location or number. For this reason, the number of differential diagnosis is increased and biopsy of the suspicious lesions is essential for an accurate diagnosis and further apropiate treatment. PMID:26538737

  20. Unconventional actins and actin-binding proteins in human protozoan parasites.

    PubMed

    Gupta, C M; Thiyagarajan, S; Sahasrabuddhe, A A

    2015-06-01

    Actin and its regulatory proteins play a key role in several essential cellular processes such as cell movement, intracellular trafficking and cytokinesis in most eukaryotes. While these proteins are highly conserved in higher eukaryotes, a number of unicellular eukaryotic organisms contain divergent forms of these proteins which have highly unusual biochemical and structural properties. Here, we review the biochemical and structural properties of these unconventional actins and their core binding proteins which are present in commonly occurring human protozoan parasites.

  1. Creatine kinase and alpha-actin mRNA levels decrease in diabetic rat hearts

    SciTech Connect

    Popovich, B.; Barrieux, A.; Dillmann, W.H.

    1987-05-01

    Diabetic cardiomyopathy is associated with cardiac atrophy and isoenzyme redistribution. To determine if tissue specific changes occur in mRNAs coding for ..cap alpha..-actin and creatine kinase (CK), they performed RNA blot analysis. Total ventricular RNA from control (C) and 4 wk old diabetic (D) rats were hybridized with /sup 32/P cDNA probes for ..cap alpha..-actin and CK. A tissue independent cDNA probe, CHOA was also used. Signal intensity was quantified by photodensitometry. D CK mRNA was 47 +/- 16% lower in D vs C. Insulin increases CK mRNA by 20% at 1.5 hs, and completely reverses the deficit after 4 wks. D ..cap alpha..-actin mRNA is 66 +/- 18% lower in D vs C. Insulin normalized ..cap alpha..-actin mRNA by 5 hs. CHOA mRNA is unchanged in D vs C, but D + insulin CHOA mRNA is 30 +/- 2% lower than C. In rats with diabetic cardiomyopathy, muscle specific CK and ..cap alpha..-actin mRNAs are decreased. Insulin treatment reverses these changes.

  2. Actin-dependence of the chloroplast cold positioning response in the liverwort Marchantia polymorpha L.

    PubMed

    Kimura, Shun; Kodama, Yutaka

    2016-01-01

    The subcellular positioning of chloroplasts can be changed by alterations in the environment such as light and temperature. For example, in leaf mesophyll cells, chloroplasts localize along anticlinal cell walls under high-intensity light, and along periclinal cell walls under low-intensity light. These types of positioning responses are involved in photosynthetic optimization. In light-mediated chloroplast positioning responses, chloroplasts move to the appropriate positions in an actin-dependent manner, although some exceptions also depend on microtubule. Even under low-intensity light, at low temperature (e.g., 5°C), chloroplasts localize along anticlinal cell walls; this phenomenon is termed chloroplast cold positioning. In this study, we analyzed whether chloroplast cold positioning is dependent on actin filaments and/or microtubules in the liverwort Marchantia polymorpha L. When liverwort cells were treated with drugs for the de-polymerization of actin filaments, chloroplast cold positioning was completely inhibited. In contrast, chloroplast cold positioning was not affected by treatment with a drug for the de-polymerization of microtubules. These observations indicate the actin-dependence of chloroplast cold positioning in M. polymorpha. Actin filaments during the chloroplast cold positioning response were visualized by using fluorescent probes based on fluorescent proteins in living liverwort cells, and thus, their behavior during the chloroplast cold positioning response was documented.

  3. Actin-dependence of the chloroplast cold positioning response in the liverwort Marchantia polymorpha L.

    PubMed Central

    Kimura, Shun

    2016-01-01

    The subcellular positioning of chloroplasts can be changed by alterations in the environment such as light and temperature. For example, in leaf mesophyll cells, chloroplasts localize along anticlinal cell walls under high-intensity light, and along periclinal cell walls under low-intensity light. These types of positioning responses are involved in photosynthetic optimization. In light-mediated chloroplast positioning responses, chloroplasts move to the appropriate positions in an actin-dependent manner, although some exceptions also depend on microtubule. Even under low-intensity light, at low temperature (e.g., 5°C), chloroplasts localize along anticlinal cell walls; this phenomenon is termed chloroplast cold positioning. In this study, we analyzed whether chloroplast cold positioning is dependent on actin filaments and/or microtubules in the liverwort Marchantia polymorpha L. When liverwort cells were treated with drugs for the de-polymerization of actin filaments, chloroplast cold positioning was completely inhibited. In contrast, chloroplast cold positioning was not affected by treatment with a drug for the de-polymerization of microtubules. These observations indicate the actin-dependence of chloroplast cold positioning in M. polymorpha. Actin filaments during the chloroplast cold positioning response were visualized by using fluorescent probes based on fluorescent proteins in living liverwort cells, and thus, their behavior during the chloroplast cold positioning response was documented. PMID:27703856

  4. ACTIN DEPOLYMERIZING FACTOR4 regulates actin dynamics during innate immune signaling in Arabidopsis.

    PubMed

    Henty-Ridilla, Jessica L; Li, Jiejie; Day, Brad; Staiger, Christopher J

    2014-01-01

    Conserved microbe-associated molecular patterns (MAMPs) are sensed by pattern recognition receptors (PRRs) on cells of plants and animals. MAMP perception typically triggers rearrangements to actin cytoskeletal arrays during innate immune signaling. However, the signaling cascades linking PRR activation by MAMPs to cytoskeleton remodeling are not well characterized. Here, we developed a system to dissect, at high spatial and temporal resolution, the regulation of actin dynamics during innate immune signaling in plant cells. Within minutes of MAMP perception, we detected changes to single actin filament turnover in epidermal cells treated with bacterial and fungal MAMPs. These MAMP-induced alterations phenocopied an ACTIN DEPOLYMERIZING FACTOR4 (ADF4) knockout mutant. Moreover, actin arrays in the adf4 mutant were unresponsive to a bacterial MAMP, elf26, but responded normally to the fungal MAMP, chitin. Together, our data provide strong genetic and cytological evidence for the inhibition of ADF activity regulating actin remodeling during innate immune signaling. This work is the first to directly link an ADF/cofilin to the cytoskeletal rearrangements elicited directly after pathogen perception in plant or mammalian cells.

  5. Actin, actin-related proteins and profilin in diatoms: a comparative genomic analysis.

    PubMed

    Aumeier, Charlotte; Polinski, Ellen; Menzel, Diedrik

    2015-10-01

    Diatoms are heterokont unicellular algae with a widespread distribution throughout all aquatic habitats. Research on diatoms has advanced significantly over the last decade due to available genetic transformation methods and publicly available genome databases. Yet up to now, proteins involved in the regulation of the cytoskeleton in diatoms are largely unknown. Consequently, this work focuses on actin and actin-related proteins (ARPs) encoded in the diatom genomes of Thalassiosira pseudonana, Thalassiosira oceanica, Phaeodactylum tricornutum, Fragilariopsis cylindrus and Pseudo-nitzschia multiseries. Our comparative genomic study revealed that most diatoms possess only a single conventional actin and a small set of ARPs. Among these are the highly conserved cytoplasmic Arp1 protein and the nuclear Arp4 as well as Arp6. Diatom genomes contain genes coding for two structurally different homologues of Arp4 that might serve specific functions. All diatom species examined here lack ARP2 and ARP3 proteins, suggesting that diatoms are not capable of forming the Arp2/3 complex, which is essential in most eukaryotes for actin filament branching and plus-end dynamics. Interestingly, none of the sequenced representatives of the Bacillariophyta phylum code for profilin. Profilin is an essential actin-binding protein regulating the monomer actin pool and is involved in filament plus-end dynamics. This is the first report of organisms not containing profilin.

  6. Activation of endothelial nitric oxide synthase is dependent on its interaction with globular actin in human umbilical vein endothelial cells.

    PubMed

    Mi, Qiongyu; Chen, Nan; Shaifta, Yasin; Xie, Liping; Lu, Hui; Liu, Zhen; Chen, Qi; Hamid, Colleen; Becker, Silke; Ji, Yong; Ferro, Albert

    2011-09-01

    Endothelial nitric oxide synthase (eNOS) has been reported to associate with globular actin, and this association increases eNOS activity. Adenosine, histamine, salbutamol and thrombin cause activation of eNOS through widely different mechanisms. Whether these eNOS agonists can regulate eNOS activity through affecting its association with actin is unknown. As previously reported, we confirmed in cultured human umbilical vein endothelial cells (HUVEC) that histamine and thrombin increased intracellular Ca(2+) whereas adenosine and salbutamol did not, and that these four agonists caused different effects on actin filament structure. Nevertheless, despite their divergent effects on intracellular Ca(2+) and on actin filament structure, we found by immunoprecipitation that adenosine, histamine, salbutamol and thrombin all caused an increase in association between eNOS and globular actin. This increase of association was inhibited by pre-treatment with phalloidin, an actin filament stabilizer. All of these agonists also increased phosphorylation of eNOS on serine residue 1177, eNOS activity, and cyclic guanosine-3', 5'-monophosphate, and these increases were all attenuated by phalloidin. Agonist-induced phosphorylation of eNOS on serine 1177 was attenuated by Akt inhibition, whereas association of eNOS with actin was not. We also found, in HEK-293 cells transfected with the eNOS mutants eNOS-S1177A or eNOS-S1177D, that the association between eNOS and globular actin was decreased as compared to cells transfected with wild-type eNOS. We conclude that association of globular actin with eNOS plays an essential and necessary role in agonist-induced eNOS activation, through enabling its phosphorylation by Akt at serine residue 1177.

  7. Pilocarpine-induced epilepsy is associated with actin cytoskeleton reorganization in the mossy fiber-CA3 synapses.

    PubMed

    Zhang, Yan-Feng; Xiong, Tian-Qing; Tan, Bai-Hong; Song, Yan; Li, Shu-Lei; Yang, Li-Bin; Li, Yan-Chao

    2014-03-01

    Dramatic structural changes have been demonstrated in the mossy fiber-CA3 synapses in the post status epilepticus (SE) animals, suggesting a potential reorganization of filamentous actin (F-actin) network occurring in the hippocampus. However, until now the long-term effects of SE on the synaptic F-actin have still not been reported. In this study, phalloidin labeling combined with confocal microscopy and protein analyses were adopted to investigate the effects of pilocarpine treatment on the F-actin in the C57BL/6 mice. As compared to the controls, there was ∼ 43% reduction in F-actin density in the post SE mice. Quantitative analysis showed that the labeling density and the puncta number were significantly decreased after pilocarpine treatment (p<0.01, n=5 mice per group, Student's t-test). The puncta of F-actin in the post SE group tended to be highly clustered, while those in the controls were generally distributed evenly. The mean puncta size of F-actin puncta was 0.73±0.19μm(2) (n=1102 puncta from 5 SE mice) in the experimental group, significantly larger than that in the controls (0.51±0.10μm(2), n=1983 puncta from 5 aged-matched control mice, p<0.01, Student's t-test). These observations were well consistent with the alterations of postsynaptic densities in the same region, revealed by immunostaining of PSD95, suggesting the reorganization of F-actin occurred mainly postsynaptically. Our results are indicative of important cytoskeletal changes in the mossy fiber-CA3 synapses after pilocarpine treatment, which may contribute to the excessive excitatory output in the hippocampal trisynaptic circuit.

  8. Exploring the Stability Limits of Actin and Its Suprastructures

    PubMed Central

    Rosin, Christopher; Erlkamp, Mirko; Ecken, Julian von der; Raunser, Stefan; Winter, Roland

    2014-01-01

    Actin is the main component of the microfilament system in eukaryotic cells and can be found in distinct morphological states. Global (G)-actin is able to assemble into highly organized, supramolecular cellular structures known as filamentous (F)-actin and bundled (B)-actin. To evaluate the structure and stability of G-, F-, and B-actin over a wide range of temperatures and pressures, we used Fourier transform infrared spectroscopy in combination with differential scanning and pressure perturbation calorimetry, small-angle x-ray scattering, laser confocal scanning microscopy, and transmission electron microscopy. Our analysis was designed to provide new (to our knowledge) insights into the stabilizing forces of actin self-assembly and to reveal the stability of the actin polymorphs, including in conditions encountered in extreme environments. In addition, we sought to explain the limited pressure stability of actin self-assembly observed in vivo. G-actin is not only the least temperature-stable but also the least pressure-stable actin species. Under abyssal conditions, where temperatures as low as 1–4°C and pressures up to 1 kbar are reached, G-actin is hardly stable. However, the supramolecular assemblies of actin are stable enough to withstand the extreme conditions usually encountered on Earth. Beyond ∼3–4 kbar, filamentous structures disassemble, and beyond ∼4 kbar, complete dissociation of F-actin structures is observed. Between ∼1 and 2 kbar, some disordering of actin assemblies commences, in agreement with in vivo observations. The limited pressure stability of the monomeric building block seems to be responsible for the suppression of actin assembly in the kbar pressure range. PMID:25517163

  9. Demonstration of prominent actin filaments in the root columella

    NASA Technical Reports Server (NTRS)

    Collings, D. A.; Zsuppan, G.; Allen, N. S.; Blancaflor, E. B.; Brown, C. S. (Principal Investigator)

    2001-01-01

    The distribution of actin filaments within the gravity-sensing columella cells of plant roots remains poorly understood, with studies over numerous years providing inconsistent descriptions of actin organization in these cells. This uncertainty in actin organization, and thus in actin's role in graviperception and gravisignaling, has led us to investigate actin arrangements in the columella cells of Zea mays L., Medicago truncatula Gaertn., Linum usitatissiilium L. and Nicotianla benthamiana Domin. Actin organization was examined using a combination of optimized immunofluorescence techniques, and an improved fluorochrome-conjugated phalloidin labeling method reliant on 3-maleimidobenzoyl-N-hydroxy-succinimide ester (MBS) cross-linking combined with glycerol permeabilization. Confocal microscopy of root sections labeled with anti-actin antibodies revealed patterns suggestive of actin throughout the columella region. These patterns included short and fragmented actin bundles, fluorescent rings around amyloplasts and intense fluorescence originating from the nucleus. Additionally, confocal microscopy of MBS-stabilized and Alexa Fluor-phalloidin-labeled root sections revealed a previously undetected state of actin organization in the columella. Discrete actin structures surrounded the amyloplasts and prominent actin cables radiated from the nuclear surface toward the cell periphery. Furthermore, the cortex of the columella cells contained fine actin bundles (or single filaments) that had a predominant transverse orientation. We also used confocal microscopy of plant roots expressing endoplasmic reticulum (ER)-targeted green fluorescent protein to demonstrate rapid ER movements within the columella cells, suggesting that the imaged actin network is functional. The successful identification of discrete actin structures in the root columella cells forms the perception and signaling.

  10. Spatial control of the actin cytoskeleton in Drosophila epithelial cells.

    PubMed

    Baum, B; Perrimon, N

    2001-10-01

    The actin cytoskeleton orders cellular space and transduces many of the forces required for morphogenesis. Here we combine genetics and cell biology to identify genes that control the polarized distribution of actin filaments within the Drosophila follicular epithelium. We find that profilin and cofilin regulate actin-filament formation throughout the cell cortex. In contrast, CAP-a Drosophila homologue of Adenylyl Cyclase Associated Proteins-functions specifically to limit actin-filament formation catalysed by Ena at apical cell junctions. The Abl tyrosine kinase also collaborates in this process. We therefore propose that CAP, Ena and Abl act in concert to modulate the subcellular distribution of actin filaments in Drosophila.

  11. Association of actin filaments with axonal microtubule tracts.

    PubMed

    Bearer, E L; Reese, T S

    1999-02-01

    Axoplasmic organelles move on actin as well as microtubules in vitro and axons contain a large amount of actin, but little is known about the organization and distribution of actin filaments within the axon. Here we undertake to define the relationship of the microtubule bundles typically found in axons to actin filaments by applying three microscopic techniques: laser-scanning confocal microscopy of immuno-labeled squid axoplasm; electronmicroscopy of conventionally prepared thin sections; and electronmicroscopy of touch preparations-a thin layer of axoplasm transferred to a specimen grid and negatively stained. Light microscopy shows that longitudinal actin filaments are abundant and usually coincide with longitudinal microtubule bundles. Electron microscopy shows that microfilaments are interwoven with the longitudinal bundles of microtubules. These bundles maintain their integrity when neurofilaments are extracted. Some, though not all microfilaments decorate with the S1 fragment of myosin, and some also act as nucleation sites for polymerization of exogenous actin, and hence are definitively identified as actin filaments. These actin filaments range in minimum length from 0.5 to 1.5 microm with some at least as long as 3.5 microm. We conclude that the microtubule-based tracks for fast organelle transport also include actin filaments. These actin filaments are sufficiently long and abundant to be ancillary or supportive of fast transport along microtubules within bundles, or to extend transport outside of the bundle. These actin filaments could also be essential for maintaining the structural integrity of the microtubule bundles.

  12. Actin filaments as dynamic reservoirs for Drp1 recruitment

    PubMed Central

    Hatch, Anna L.; Ji, Wei-Ke; Merrill, Ronald A.; Strack, Stefan; Higgs, Henry N.

    2016-01-01

    Drp1 is a dynamin-family GTPase recruited to mitochondria and peroxisomes, where it oligomerizes and drives membrane fission. Regulation of mitochondrial Drp1 recruitment is not fully understood. We previously showed that Drp1 binds actin filaments directly, and actin polymerization is necessary for mitochondrial Drp1 oligomerization in mammals. Here we show the Drp1/actin interaction displays unusual properties that are influenced by several factors. At saturation, only a fraction Drp1 binds actin filaments, and the off-rate of actin-bound Drp1 is significantly increased by unbound Drp1. GDP and GTP accelerate and decelerate Drp1/actin binding dynamics, respectively. Actin has a biphasic effect on Drp1 GTP hydrolysis, increasing at low actin:Drp1 ratio but returning to baseline at high ratio. Drp1 also bundles filaments. Bundles have reduced dynamics but follow the same trends as single filaments. Drp1 preferentially incorporates into bundles at higher ionic strength. We measure Drp1 concentration to be ∼0.5 μM in U2OS cell cytosol, suggesting the actin-binding affinity measured here (Kd = 0.6 μM) is in the physiologically relevant range. The ability of Drp1 to bind actin filaments in a highly dynamic manner provides potential for actin filaments to serve as reservoirs of oligomerization-competent Drp1 that can be accessed for mitochondrial fission. PMID:27559132

  13. Direct Observation of Tropomyosin Binding to Actin Filaments

    PubMed Central

    Schmidt, William M.; Lehman, William; Moore, Jeffrey R.

    2015-01-01

    Tropomyosin is an elongated α-helical coiled-coil that binds to seven consecutive actin subunits along the long-pitch helix of actin filaments. Once bound, tropomyosin polymerizes end-to-end and both stabilizes F-actin and regulates access of various actin binding proteins including myosin in muscle and non-muscle cells. Single tropomyosin molecules bind weakly to F-actin with millimolar Kd, whereas the end-to-end linked tropomyosin associates with about a one thousand-fold greater affinity. Despite years of study, the assembly mechanism of tropomyosin onto actin filaments remains unclear. In the current study, we used total internal reflection fluorescence (TIRF) microscopy to directly monitor the cooperative binding of fluorescently labeled tropomyosin molecules to phalloidin-stabilized actin filaments. We find that tropomyosin molecules assemble from multiple growth sites following random low affinity binding of single molecules to actin. As the length of the tropomyosin chain increases, the probability of detachment decreases, which leads to further chain growth. Tropomyosin chain extension is linearly dependent on tropomyosin concentration, occurring at approximately 100 monomers/(μM*s). The random tropomyosin binding to F-actin leads to discontinuous end-to-end association where gaps in the chain continuity smaller than the required seven sequential actin monomers are available. Direct observation of tropomyosin detachment revealed the number of gaps in actin-bound tropomyosin, the time course of gap annealing, and the eventual filament saturation process. PMID:26033920

  14. Dendritic Actin Nucleation Causes Traveling Waves and Patches

    NASA Astrophysics Data System (ADS)

    Carlsson, Anders

    2010-03-01

    Reversible polymerization of the intracellular protein actin into semiflexible filaments is crucial for cell motion and environmental sensing. Recent studies have shown that polymerized actin can spontaneously form traveling waves and/or moving patches. I investigate possible mechanisms for such phenomena by numerically simulating the ``dendritic nucleation'' model of actin network growth. The simulations treat the growth of an actin network on a flat portion of a cell membrane, using a stochastic-growth method which calculates an explicit three-dimensional network structure. The calculations treat processes including filament growth, capping, branching, severing, and Brownian motion. The dynamics of membrane proteins stimulating actin polymerization are also included: they diffuse in the membrane, and detach/deactivate in the presence of polymerized actin. The simulations show three types of polymerized-actin behavior: 1) traveling waves, 2) coherently moving patches, and 3) random fluctuations with occasional moving patches. Wave formation is favored at low free-actin concentrations by a long reattachment time for the membrane proteins, and by weakness of the attractive interaction between filaments and the membrane. Raising the free-actin concentration results in a randomly varying distribution of polymerized actin. Lowering the free-actin concentration below the optimal value for waves causes the waves to break up into patches which, however, move coherently. Effects of similar magnitude are predicted when other intracellular protein concentrations are varied. Diffusion of the membrane proteins slows the waves, and, if fast enough, stops them completely, resulting in the formation of a static spot.

  15. Geometrical and Mechanical Properties Control Actin Filament Organization

    PubMed Central

    Ennomani, Hajer; Théry, Manuel; Nedelec, Francois; Blanchoin, Laurent

    2015-01-01

    The different actin structures governing eukaryotic cell shape and movement are not only determined by the properties of the actin filaments and associated proteins, but also by geometrical constraints. We recently demonstrated that limiting nucleation to specific regions was sufficient to obtain actin networks with different organization. To further investigate how spatially constrained actin nucleation determines the emergent actin organization, we performed detailed simulations of the actin filament system using Cytosim. We first calibrated the steric interaction between filaments, by matching, in simulations and experiments, the bundled actin organization observed with a rectangular bar of nucleating factor. We then studied the overall organization of actin filaments generated by more complex pattern geometries used experimentally. We found that the fraction of parallel versus antiparallel bundles is determined by the mechanical properties of actin filament or bundles and the efficiency of nucleation. Thus nucleation geometry, actin filaments local interactions, bundle rigidity, and nucleation efficiency are the key parameters controlling the emergent actin architecture. We finally simulated more complex nucleation patterns and performed the corresponding experiments to confirm the predictive capabilities of the model. PMID:26016478

  16. Geometrical and mechanical properties control actin filament organization.

    PubMed

    Letort, Gaëlle; Politi, Antonio Z; Ennomani, Hajer; Théry, Manuel; Nedelec, Francois; Blanchoin, Laurent

    2015-05-01

    The different actin structures governing eukaryotic cell shape and movement are not only determined by the properties of the actin filaments and associated proteins, but also by geometrical constraints. We recently demonstrated that limiting nucleation to specific regions was sufficient to obtain actin networks with different organization. To further investigate how spatially constrained actin nucleation determines the emergent actin organization, we performed detailed simulations of the actin filament system using Cytosim. We first calibrated the steric interaction between filaments, by matching, in simulations and experiments, the bundled actin organization observed with a rectangular bar of nucleating factor. We then studied the overall organization of actin filaments generated by more complex pattern geometries used experimentally. We found that the fraction of parallel versus antiparallel bundles is determined by the mechanical properties of actin filament or bundles and the efficiency of nucleation. Thus nucleation geometry, actin filaments local interactions, bundle rigidity, and nucleation efficiency are the key parameters controlling the emergent actin architecture. We finally simulated more complex nucleation patterns and performed the corresponding experiments to confirm the predictive capabilities of the model.

  17. Cytoplasmic Actin: Purification and Single Molecule Assembly Assays

    PubMed Central

    Hansen, Scott D.; Zuchero, J. Bradley; Mullins, R. Dyche

    2014-01-01

    The actin cytoskeleton is essential to all eukaryotic cells. In addition to playing important structural roles, assembly of actin into filaments powers diverse cellular processes, including cell motility, cytokinesis, and endocytosis. Actin polymerization is tightly regulated by its numerous cofactors, which control spatial and temporal assembly of actin as well as the physical properties of these filaments. Development of an in vitro model of actin polymerization from purified components has allowed for great advances in determining the effects of these proteins on the actin cytoskeleton. Here we describe how to use the pyrene actin assembly assay to determine the effect of a protein on the kinetics of actin assembly, either directly or as mediated by proteins such as nucleation or capping factors. Secondly, we show how fluorescently labeled phalloidin can be used to visualize the filaments that are created in vitro to give insight into how proteins regulate actin filament structure. Finally, we describe a method for visualizing dynamic assembly and disassembly of single actin filaments and fluorescently labeled actin binding proteins using total internal reflection fluorescence (TIRF) microscopy. PMID:23868587

  18. Distributed actin turnover in the lamellipodium and FRAP kinetics.

    PubMed

    Smith, Matthew B; Kiuchi, Tai; Watanabe, Naoki; Vavylonis, Dimitrios

    2013-01-08

    Studies of actin dynamics at the leading edge of motile cells with single-molecule speckle (SiMS) microscopy have shown a broad distribution of EGFP-actin speckle lifetimes and indicated actin polymerization and depolymerization over an extended region. Other experiments using FRAP with the same EGFP-actin as a probe have suggested, by contrast, that polymerization occurs exclusively at the leading edge. We performed FRAP experiments on XTC cells to compare SiMS to FRAP on the same cell type. We used speckle statistics obtained by SiMS to model the steady-state distribution and kinetics of actin in the lamellipodium. We demonstrate that a model with a single diffuse actin species is in good agreement with FRAP experiments. A model including two species of diffuse actin provides an even better agreement. The second species consists of slowly diffusing oligomers that associate to the F-actin network throughout the lamellipodium or break up into monomers after a characteristic time. Our work motivates studies to test the presence and composition of slowly diffusing actin species that may contribute to local remodeling of the actin network and increase the amount of soluble actin.

  19. Evidence for filamentous actin in ookinetes of a malarial parasite.

    PubMed

    Siden-Kiamos, Inga; Louis, Christos; Matuschewski, Kai

    2012-02-01

    Extracellular stages of apicomplexan parasites utilize their own actin myosin motor machinery for gliding locomotion, penetration of cell barriers, and host cell invasion. Thus far, filamentous actin could not be visualized by standard microscopic techniques in vivo. Here, we describe the generation of a novel peptide antibody against the divergent amino-terminal portion of the major Plasmodium isoform, actin I. We show that our antiserum, termed Ab-actinI-I, is conformation-specific. In motile ookinetes it recognizes actin in rod-like structures, which are sensitive to inhibitors interfering with actin polymerization. The average size of the rods is 600 nm, which is considerably longer than what has been detected in in vitro studies of actin filaments.

  20. The Potential Roles of Actin in The Nucleus

    PubMed Central

    Falahzadeh, Khadijeh; Banaei-Esfahani, Amir; Shahhoseini, Maryam

    2015-01-01

    Over the past few decades, actin’s presence in the nucleus has been demonstrated. Actin is a key protein necessary for different nuclear processes. Although actin is well known for its functional role in dynamic behavior of the cytoskeleton, emerging studies are now highlighting new roles for actin. At the present time there is no doubt about the presence of actin in the nucleus. A number of studies have uncovered the functional involvement of actin in nuclear processes. Actin as one of the nuclear components has its own structured and functional rules, such as nuclear matrix association, chromatin remodeling, transcription by RNA polymerases I, II, III and mRNA processing. In this historical review, we attempt to provide an overview of our current understanding of the functions of actin in the nucleus. PMID:25870830

  1. Confinement induces actin flow in a meiotic cytoplasm

    PubMed Central

    Pinot, Mathieu; Steiner, Villier; Dehapiot, Benoit; Yoo, Byung-Kuk; Chesnel, Franck; Blanchoin, Laurent; Kervrann, Charles; Gueroui, Zoher

    2012-01-01

    In vivo, F-actin flows are observed at different cell life stages and participate in various developmental processes during asymmetric divisions in vertebrate oocytes, cell migration, or wound healing. Here, we show that confinement has a dramatic effect on F-actin spatiotemporal organization. We reconstitute in vitro the spontaneous generation of F-actin flow using Xenopus meiotic extracts artificially confined within a geometry mimicking the cell boundary. Perturbations of actin polymerization kinetics or F-actin nucleation sites strongly modify the network flow dynamics. A combination of quantitative image analysis and biochemical perturbations shows that both spatial localization of F-actin nucleators and actin turnover play a decisive role in generating flow. Interestingly, our in vitro assay recapitulates several symmetry-breaking processes observed in oocytes and early embryonic cells. PMID:22753521

  2. New Insights into Mechanism and Regulation of Actin Capping Protein

    PubMed Central

    Cooper, John A.; Sept, David

    2008-01-01

    The heterodimeric actin capping protein, referred to here as “CP,” is an essential element of the actin cytoskeleton, binding to the barbed ends of actin filaments and regulating their polymerization. In vitro, CP has a critical role in the dendritic nucleation process of actin assembly mediated by Arp2/3 complex, and in vivo, CP is important for actin assembly and actin-based process of morphogenesis and differentiation. Recent studies have provided new insight into the mechanism of CP binding the barbed end, which raises new possibilities for the dynamics of CP and actin in cells. In addition, a number of molecules that bind and regulate CP have been discovered, suggesting new ideas for how CP may integrate into diverse processes of cell physiology. PMID:18544499

  3. Mast cell desensitization inhibits calcium flux and aberrantly remodels actin

    PubMed Central

    Ang, W.X. Gladys; Church, Alison M.; Kulis, Mike; Choi, Hae Woong; Burks, A. Wesley

    2016-01-01

    Rush desensitization (DS) is a widely used and effective clinical strategy for the rapid inhibition of IgE-mediated anaphylactic responses. However, the cellular targets and underlying mechanisms behind this process remain unclear. Recent studies have implicated mast cells (MCs) as the primary target cells for DS. Here, we developed a murine model of passive anaphylaxis with demonstrated MC involvement and an in vitro assay to evaluate the effect of DS on MCs. In contrast with previous reports, we determined that functional IgE remains on the cell surface of desensitized MCs following DS. Despite notable reductions in MC degranulation following DS, the high-affinity IgE receptor FcεRI was still capable of transducing signals in desensitized MCs. Additionally, we found that displacement of the actin cytoskeleton and its continued association with FcεRI impede the capacity of desensitized MCs to evoke the calcium response that is essential for MC degranulation. Together, these findings suggest that reduced degranulation responses in desensitized MCs arise from aberrant actin remodeling, providing insights that may lead to improvement of DS treatments for anaphylactic responses. PMID:27669462

  4. Actin-interacting Protein 1 Promotes Disassembly of Actin-depolymerizing Factor/Cofilin-bound Actin Filaments in a pH-dependent Manner*

    PubMed Central

    Nomura, Kazumi; Hayakawa, Kimihide; Tatsumi, Hitoshi; Ono, Shoichiro

    2016-01-01

    Actin-interacting protein 1 (AIP1) is a conserved WD repeat protein that promotes disassembly of actin filaments when actin-depolymerizing factor (ADF)/cofilin is present. Although AIP1 is known to be essential for a number of cellular events involving dynamic rearrangement of the actin cytoskeleton, the regulatory mechanism of the function of AIP1 is unknown. In this study, we report that two AIP1 isoforms from the nematode Caenorhabditis elegans, known as UNC-78 and AIPL-1, are pH-sensitive in enhancement of actin filament disassembly. Both AIP1 isoforms only weakly enhance disassembly of ADF/cofilin-bound actin filaments at an acidic pH but show stronger disassembly activity at neutral and basic pH values. However, a severing-defective mutant of UNC-78 shows pH-insensitive binding to ADF/cofilin-decorated actin filaments, suggesting that the process of filament severing or disassembly, but not filament binding, is pH-dependent. His-60 of AIP1 is located near the predicted binding surface for the ADF/cofilin-actin complex, and an H60K mutation of AIP1 partially impairs its pH sensitivity, suggesting that His-60 is involved in the pH sensor for AIP1. These biochemical results suggest that pH-dependent changes in AIP1 activity might be a novel regulatory mechanism of actin filament dynamics. PMID:26747606

  5. Actin-mediated motion of meiotic chromosomes

    PubMed Central

    Koszul, R.; Kim, K. P.; Prentiss, M.; Kleckner, N.; Kameoka, S.

    2008-01-01

    Summary Chromosome movement is prominent during meiosis. Here, using a combination of in vitro and in vivo approaches, we elucidate the basis for dynamic mid-prophase chromosome movement in budding yeast. Diverse finding reveal a process in which, at the pachytene stage, individual telomere/nuclear envelope (NE) ensembles attach passively to, and then move in concert with, nucleus-hugging actin cables that are continuous with the global cytoskeletal actin network. Other chromosomes move in concert with lead chromosome(s). The same process, in modulated form, explains the zygotene "bouquet" configuration in which, immediately preceding pachytene, chromosome ends colocalize dynamically in a restricted region of the NE. Mechanical properties of the system and biological roles of mid-prophase movement for meiosis, including recombination, are discussed. PMID:18585353

  6. PI(3,5)P2 controls endosomal branched actin dynamics by regulating cortactin–actin interactions

    PubMed Central

    Hong, Nan Hyung; Qi, Aidong

    2015-01-01

    Branched actin critically contributes to membrane trafficking by regulating membrane curvature, dynamics, fission, and transport. However, how actin dynamics are controlled at membranes is poorly understood. Here, we identify the branched actin regulator cortactin as a direct binding partner of phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2) and demonstrate that their interaction promotes turnover of late endosomal actin. In vitro biochemical studies indicated that cortactin binds PI(3,5)P2 via its actin filament-binding region. Furthermore, PI(3,5)P2 competed with actin filaments for binding to cortactin, thereby antagonizing cortactin activity. These findings suggest that PI(3,5)P2 formation on endosomes may remove cortactin from endosome-associated branched actin. Indeed, inhibition of PI(3,5)P2 production led to cortactin accumulation and actin stabilization on Rab7+ endosomes. Conversely, inhibition of Arp2/3 complex activity greatly reduced cortactin localization to late endosomes. Knockdown of cortactin reversed PI(3,5)P2-inhibitor–induced actin accumulation and stabilization on endosomes. These data suggest a model in which PI(3,5)P2 binding removes cortactin from late endosomal branched actin networks and thereby promotes net actin turnover. PMID:26323691

  7. Calcium regulation of actin crosslinking is important for function of the actin cytoskeleton in Dictyostelium.

    PubMed

    Furukawa, Ruth; Maselli, Andrew; Thomson, Susanne A M; Lim, Rita W L; Stokes, John V; Fechheimer, Marcus

    2003-01-01

    The actin cytoskeleton is sensitive to changes in calcium, which affect contractility, actin-severing proteins, actin-crosslinking proteins and calmodulin-regulated enzymes. To dissect the role of calcium control on the activity of individual proteins from effects of calcium on other processes, calcium-insensitive forms of these proteins were prepared and introduced into living cells to replace a calcium-sensitive form of the same protein. Crosslinking and bundling of actin filaments by the Dictyostelium 34 kDa protein is inhibited in the presence of micromolar free calcium. A modified form of the 34 kDa protein with mutations in the calcium binding EF hand (34 kDa deltaEF2) was prepared using site-directed mutagenesis and expressed in E. coli. Equilibrium dialysis using [(45)Ca]CaCl(2) revealed that the wild-type protein is able to bind one calcium ion with a Kd of 2.4 microM. This calcium binding is absent in the 34 kDa deltaEF2 protein. The actin-binding activity of the 34 kDa deltaEF2 protein was equivalent to wildtype but calcium insensitive in vitro. The wild-type and 34 kDa deltaEF2 proteins were expressed in 34-kDa-null and 34 kDa/alpha-actinin double null mutant Dictyostelium strains to test the hypothesis that calcium regulation of actin crosslinking is important in vivo. The 34 kDa deltaEF2 failed to supply function of the 34 kDa protein important for control of cell size and for normal growth to either of these 34-kDa-null strains. Furthermore, the distribution of the 34 kDa protein and actin were abnormal in cells expressing 34 kDa deltaEF2. Thus, calcium regulation of the formation and/or dissolution of crosslinked actin structures is required for dynamic behavior of the actin cytoskeleton important for cell structure and growth.

  8. Dynamics of Membranes Driven by Actin Polymerization

    PubMed Central

    Gov, Nir S.; Gopinathan, Ajay

    2006-01-01

    A motile cell, when stimulated, shows a dramatic increase in the activity of its membrane, manifested by the appearance of dynamic membrane structures such as lamellipodia, filopodia, and membrane ruffles. The external stimulus turns on membrane bound activators, like Cdc42 and PIP2, which cause increased branching and polymerization of the actin cytoskeleton in their vicinity leading to a local protrusive force on the membrane. The emergence of the complex membrane structures is a result of the coupling between the dynamics of the membrane, the activators, and the protrusive forces. We present a simple model that treats the dynamics of a membrane under the action of actin polymerization forces that depend on the local density of freely diffusing activators on the membrane. We show that, depending on the spontaneous membrane curvature associated with the activators, the resulting membrane motion can be wavelike, corresponding to membrane ruffling and actin waves, or unstable, indicating the tendency of filopodia to form. Our model also quantitatively explains a variety of related experimental observations and makes several testable predictions. PMID:16239328

  9. Novel roles for actin in mitochondrial fission.

    PubMed

    Hatch, Anna L; Gurel, Pinar S; Higgs, Henry N

    2014-11-01

    Mitochondrial dynamics, including fusion, fission and translocation, are crucial to cellular homeostasis, with roles in cellular polarity, stress response and apoptosis. Mitochondrial fission has received particular attention, owing to links with several neurodegenerative diseases. A central player in fission is the cytoplasmic dynamin-related GTPase Drp1, which oligomerizes at the fission site and hydrolyzes GTP to drive membrane ingression. Drp1 recruitment to the outer mitochondrial membrane (OMM) is a key regulatory event, which appears to require a pre-constriction step in which the endoplasmic reticulum (ER) and mitochondrion interact extensively, a process termed ERMD (ER-associated mitochondrial division). It is unclear how ER-mitochondrial contact generates the force required for pre-constriction or why pre-constriction leads to Drp1 recruitment. Recent results, however, show that ERMD might be an actin-based process in mammals that requires the ER-associated formin INF2 upstream of Drp1, and that myosin II and other actin-binding proteins might be involved. In this Commentary, we present a mechanistic model for mitochondrial fission in which actin and myosin contribute in two ways; firstly, by supplying the force for pre-constriction and secondly, by serving as a coincidence detector for Drp1 binding. In addition, we discuss the possibility that multiple fission mechanisms exist in mammals.

  10. Novel roles for actin in mitochondrial fission

    PubMed Central

    Hatch, Anna L.; Gurel, Pinar S.; Higgs, Henry N.

    2014-01-01

    ABSTRACT Mitochondrial dynamics, including fusion, fission and translocation, are crucial to cellular homeostasis, with roles in cellular polarity, stress response and apoptosis. Mitochondrial fission has received particular attention, owing to links with several neurodegenerative diseases. A central player in fission is the cytoplasmic dynamin-related GTPase Drp1, which oligomerizes at the fission site and hydrolyzes GTP to drive membrane ingression. Drp1 recruitment to the outer mitochondrial membrane (OMM) is a key regulatory event, which appears to require a pre-constriction step in which the endoplasmic reticulum (ER) and mitochondrion interact extensively, a process termed ERMD (ER-associated mitochondrial division). It is unclear how ER–mitochondrial contact generates the force required for pre-constriction or why pre-constriction leads to Drp1 recruitment. Recent results, however, show that ERMD might be an actin-based process in mammals that requires the ER-associated formin INF2 upstream of Drp1, and that myosin II and other actin-binding proteins might be involved. In this Commentary, we present a mechanistic model for mitochondrial fission in which actin and myosin contribute in two ways; firstly, by supplying the force for pre-constriction and secondly, by serving as a coincidence detector for Drp1 binding. In addition, we discuss the possibility that multiple fission mechanisms exist in mammals. PMID:25217628

  11. Metallothionein immunolocalization in actinic skin nonmelanoma carcinomas.

    PubMed

    Borges Júnior, Paulo C; Ribeiro, Rosy I M A; Cardoso, Sérgio V; Berbet, Alceu L C; Rocha, Ademir; Espindola, Foued S; Loyola, Adriano M

    2007-06-01

    Basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) are the most frequent skin cancer. Its pathogeny is linked to genotoxic effects of actinic radiation exposure, especially to ultraviolet wavelength. Metallothionein (MT) is a low-molecular weight protein with high affinity for heavy metal. Its intracellular function has been related to heavy metals and free-radical detoxification, although many studies linked MT to protective action against actinic mutagenesis. In other way, overexpression in malignant tumors has been related to worse prognosis. We aimed to evaluate MT immunohistochemical expression in skin cancer associated to actinic radiation. Twenty-six BCC cases, 20 SCC, and 6 normal skin fragments were investigated. Immunohistochemical assay were performed by streptavidin-biotin-peroxidase technique with standard monoclonal antibody (E9). In normal skin, immunostaining was observed in basal layer of the epithelium. In the epithelium adjacent to tumors, suprabasal layer was also intensely labeled. Mean MT immunostaining indices were 18.5+21.2% for BCC and 69.1+14.4% for SCC. This difference was statistically significant. Higher MT expression in SCC as compared with BCC suggests association with tumoral aggressiveness.

  12. Growth of branched actin networks against obstacles.

    PubMed Central

    Carlsson, A E

    2001-01-01

    A method for simulating the growth of branched actin networks against obstacles has been developed. The method is based on simple stochastic events, including addition or removal of monomers at filament ends, capping of filament ends, nucleation of branches from existing filaments, and detachment of branches; the network structure for several different models of the branching process has also been studied. The models differ with regard to their inclusion of effects such as preferred branch orientations, filament uncapping at the obstacle, and preferential branching at filament ends. The actin ultrastructure near the membrane in lamellipodia is reasonably well produced if preferential branching in the direction of the obstacle or barbed-end uncapping effects are included. Uncapping effects cause the structures to have a few very long filaments that are similar to those seen in pathogen-induced "actin tails." The dependence of the growth velocity, branch spacing, and network density on the rate parameters for the various processes is quite different among the branching models. An analytic theory of the growth velocity and branch spacing of the network is described. Experiments are suggested that could distinguish among some of the branching models. PMID:11566765

  13. Global treadmilling coordinates actin turnover and controls the size of actin networks.

    PubMed

    Carlier, Marie-France; Shekhar, Shashank

    2017-03-01

    Various cellular processes (including cell motility) are driven by the regulated, polarized assembly of actin filaments into distinct force-producing arrays of defined size and architecture. Branched, linear, contractile and cytosolic arrays coexist in vivo, and cells intricately control the number, length and assembly rate of filaments in these arrays. Recent in vitro and in vivo studies have revealed novel molecular mechanisms that regulate the number of filament barbed and pointed ends and their respective assembly and disassembly rates, thus defining classes of dynamically different filaments, which coexist in the same cell. We propose that a global treadmilling process, in which a steady-state amount of polymerizable actin monomers is established by the dynamics of each network, is responsible for defining the size and turnover of coexisting actin networks. Furthermore, signal-induced changes in the partitioning of actin to distinct arrays (mediated by RHO GTPases) result in the establishment of various steady-state concentrations of polymerizable monomers, thereby globally influencing the growth rate of actin filaments.

  14. Actin-binding Protein Drebrin Regulates HIV-1-triggered Actin Polymerization and Viral Infection*

    PubMed Central

    Gordón-Alonso, Mónica; Rocha-Perugini, Vera; Álvarez, Susana; Ursa, Ángeles; Izquierdo-Useros, Nuria; Martinez-Picado, Javier; Muñoz-Fernández, María A.; Sánchez-Madrid, Francisco

    2013-01-01

    HIV-1 contact with target cells triggers F-actin rearrangements that are essential for several steps of the viral cycle. Successful HIV entry into CD4+ T cells requires actin reorganization induced by the interaction of the cellular receptor/co-receptor complex CD4/CXCR4 with the viral envelope complex gp120/gp41 (Env). In this report, we analyze the role of the actin modulator drebrin in HIV-1 viral infection and cell to cell fusion. We show that drebrin associates with CXCR4 before and during HIV infection. Drebrin is actively recruited toward cell-virus and Env-driven cell to cell contacts. After viral internalization, drebrin clustering is retained in a fraction of the internalized particles. Through a combination of RNAi-based inhibition of endogenous drebrin and GFP-tagged expression of wild-type and mutant forms, we establish drebrin as a negative regulator of HIV entry and HIV-mediated cell fusion. Down-regulation of drebrin expression promotes HIV-1 entry, decreases F-actin polymerization, and enhances profilin local accumulation in response to HIV-1. These data underscore the negative role of drebrin in HIV infection by modulating viral entry, mainly through the control of actin cytoskeleton polymerization in response to HIV-1. PMID:23926103

  15. The Saccharomyces cerevisiae actin-related protein Arp2 is involved in the actin cytoskeleton

    PubMed Central

    1996-01-01

    Arp2p is an essential yeast actin-related protein. Disruption of the corresponding ARP2 gene leads to a terminal phenotype characterized by the presence of a single large bud. Thus, Arp2p may be important for a late stage of the cell cycle (Schwob, E., and R.P. Martin, 1992. Nature (Lond.). 355:179-182). We have localized Arp2p by indirect immunofluorescence. Specific peptide antibodies revealed punctate staining under the plasma membrane, which partially colocalizes with actin. Temperature-sensitive arp2 mutations were created by PCR mutagenesis and selected by an ade2/SUP11 sectoring screen. One temperature-sensitive mutant that was characterized, arp2-H330L, was osmosensitive and had an altered actin cytoskeleton at a nonpermissive temperature, suggesting a role of Arp2p in the actin cytoskeleton. Random budding patterns were observed in both haploid and diploid arp2- H330L mutant cells. Endocytosis, as judged by Lucifer yellow uptake, was severely reduced in the mutant, at all temperatures. In addition, genetic interaction was observed between temperature-sensitive alleles arp2-H330L and cdc10-1. CDC10 is a gene encoding a neck filament- associated protein that is necessary for polarized growth and cytokinesis. Overall, the immunolocalization, mutant phenotypes, and genetic interaction suggest that the Arp2 protein is an essential component of the actin cytoskeleton that is involved in membrane growth and polarity, as well as in endocytosis. PMID:8698808

  16. Lamellipodin promotes actin assembly by clustering Ena/VASP proteins and tethering them to actin filaments

    PubMed Central

    Hansen, Scott D; Mullins, R Dyche

    2015-01-01

    Enabled/Vasodilator (Ena/VASP) proteins promote actin filament assembly at multiple locations, including: leading edge membranes, focal adhesions, and the surface of intracellular pathogens. One important Ena/VASP regulator is the mig-10/Lamellipodin/RIAM family of adaptors that promote lamellipod formation in fibroblasts and drive neurite outgrowth and axon guidance in neurons. To better understand how MRL proteins promote actin network formation we studied the interactions between Lamellipodin (Lpd), actin, and VASP, both in vivo and in vitro. We find that Lpd binds directly to actin filaments and that this interaction regulates its subcellular localization and enhances its effect on VASP polymerase activity. We propose that Lpd delivers Ena/VASP proteins to growing barbed ends and increases their polymerase activity by tethering them to filaments. This interaction represents one more pathway by which growing actin filaments produce positive feedback to control localization and activity of proteins that regulate their assembly. DOI: http://dx.doi.org/10.7554/eLife.06585.001 PMID:26295568

  17. Impact of actin filament stabilization on adult hippocampal and olfactory bulb neurogenesis.

    PubMed

    Kronenberg, Golo; Gertz, Karen; Baldinger, Tina; Kirste, Imke; Eckart, Sarah; Yildirim, Ferah; Ji, Shengbo; Heuser, Isabella; Schröck, Helmut; Hörtnagl, Heide; Sohr, Reinhard; Djoufack, Pierre Chryso; Jüttner, René; Glass, Rainer; Przesdzing, Ingo; Kumar, Jitender; Freyer, Dorette; Hellweg, Rainer; Kettenmann, Helmut; Fink, Klaus Benno; Endres, Matthias

    2010-03-03

    Rearrangement of the actin cytoskeleton is essential for dynamic cellular processes. Decreased actin turnover and rigidity of cytoskeletal structures have been associated with aging and cell death. Gelsolin is a Ca(2+)-activated actin-severing protein that is widely expressed throughout the adult mammalian brain. Here, we used gelsolin-deficient (Gsn(-/-)) mice as a model system for actin filament stabilization. In Gsn(-/-) mice, emigration of newly generated cells from the subventricular zone into the olfactory bulb was slowed. In vitro, gelsolin deficiency did not affect proliferation or neuronal differentiation of adult neural progenitors cells (NPCs) but resulted in retarded migration. Surprisingly, hippocampal neurogenesis was robustly induced by gelsolin deficiency. The ability of NPCs to intrinsically sense excitatory activity and thereby implement coupling between network activity and neurogenesis has recently been established. Depolarization-induced [Ca(2+)](i) increases and exocytotic neurotransmitter release were enhanced in Gsn(-/-) synaptosomes. Importantly, treatment of Gsn(-/-) synaptosomes with mycotoxin cytochalasin D, which, like gelsolin, produces actin disassembly, decreased enhanced Ca(2+) influx and subsequent exocytotic norepinephrine release to wild-type levels. Similarly, depolarization-induced glutamate release from Gsn(-/-) brain slices was increased. Furthermore, increased hippocampal neurogenesis in Gsn(-/-) mice was associated with a special microenvironment characterized by enhanced density of perfused vessels, increased regional cerebral blood flow, and increased endothelial nitric oxide synthase (NOS-III) expression in hippocampus. Together, reduced filamentous actin turnover in presynaptic terminals causes increased Ca(2+) influx and, subsequently, elevated exocytotic neurotransmitter release acting on neural progenitors. Increased neurogenesis in Gsn(-/-) hippocampus is associated with a special vascular niche for neurogenesis.

  18. Phosphocreatine as an energy source for actin cytoskeletal rearrangements during myoblast fusion.

    PubMed

    O'Connor, Roddy S; Steeds, Craig M; Wiseman, Robert W; Pavlath, Grace K

    2008-06-15

    Myoblast fusion is essential for muscle development, postnatal growth and muscle repair after injury. Recent studies have demonstrated roles for actin polymerization during myoblast fusion. Dynamic cytoskeletal assemblies directing cell-cell contact, membrane coalescence and ultimately fusion require substantial cellular energy demands. Various energy generating systems exist in cells but the partitioning of energy sources during myoblast fusion is unknown. Here, we demonstrate a novel role for phosphocreatine (PCr) as a spatiotemporal energy buffer during primary mouse myoblast fusion with nascent myotubes. Creatine treatment enhanced cell fusion in a creatine kinase (CK)-dependent manner suggesting that ATP-consuming reactions are replenished through the PCr/CK system. Furthermore, selective inhibition of actin polymerization prevented myonuclear addition following creatine treatment. As myotube formation is dependent on cytoskeletal reorganization, our findings suggest that PCr hydrolysis is coupled to actin dynamics during myoblast fusion. We conclude that myoblast fusion is a high-energy process, and can be enhanced by PCr buffering of energy demands during actin cytoskeletal rearrangements in myoblast fusion. These findings implicate roles for PCr as a high-energy phosphate buffer in the fusion of multiple cell types including sperm/oocyte, trophoblasts and macrophages. Furthermore, our results suggest the observed beneficial effects of oral creatine supplementation in humans may result in part from enhanced myoblast fusion.

  19. The formation of cortical actin arrays in human trabecular meshwork cells in response to cytoskeletal disruption.

    PubMed

    Murphy, Kaitlin C; Morgan, Joshua T; Wood, Joshua A; Sadeli, Adeline; Murphy, Christopher J; Russell, Paul

    2014-10-15

    The cytoskeleton of human trabecular meshwork (HTM) cells is known to be altered in glaucoma and has been hypothesized to reduce outflow facility through contracting the HTM tissue. Latrunculin B (Lat-B) and Rho-associated protein kinase (ROCK) inhibitors disrupt the actin cytoskeleton and are in clinical trials as glaucoma therapeutics. We have previously reported a transient increase in HTM cell stiffness peaking at 90 min after Lat-B treatment with a return to pretreatment values after 270 min. We hypothesize that changes in actin morphology correlate with alterations in cell stiffness induced by Lat-B but this is not a general consequence of other cytoskeletal disrupting agents such as Rho kinase inhibitors. We treated HTM cells with 2 µM Lat-B or 100 µM Y-27632 and allowed the cells to recover for 30-270 min. While examining actin morphology in Lat-B treated cells, we observed striking cortical actin arrays (CAAs). The percentage of CAA positive cells (CPCs) was time dependent and exceeded 30% at 90 min and decreased after 270 min. Y-27632 treated cells exhibited few CAAs and no changes in cell stiffness. Together, these data suggest that the increase in cell stiffness after Lat-B treatment is correlated with CAAs.

  20. Tropomyosin - master regulator of actin filament function in the cytoskeleton.

    PubMed

    Gunning, Peter W; Hardeman, Edna C; Lappalainen, Pekka; Mulvihill, Daniel P

    2015-08-15

    Tropomyosin (Tpm) isoforms are the master regulators of the functions of individual actin filaments in fungi and metazoans. Tpms are coiled-coil parallel dimers that form a head-to-tail polymer along the length of actin filaments. Yeast only has two Tpm isoforms, whereas mammals have over 40. Each cytoskeletal actin filament contains a homopolymer of Tpm homodimers, resulting in a filament of uniform Tpm composition along its length. Evidence for this 'master regulator' role is based on four core sets of observation. First, spatially and functionally distinct actin filaments contain different Tpm isoforms, and recent data suggest that members of the formin family of actin filament nucleators can specify which Tpm isoform is added to the growing actin filament. Second, Tpms regulate whole-organism physiology in terms of morphogenesis, cell proliferation, vesicle trafficking, biomechanics, glucose metabolism and organ size in an isoform-specific manner. Third, Tpms achieve these functional outputs by regulating the interaction of actin filaments with myosin motors and actin-binding proteins in an isoform-specific manner. Last, the assembly of complex structures, such as stress fibers and podosomes involves the collaboration of multiple types of actin filament specified by their Tpm composition. This allows the cell to specify actin filament function in time and space by simply specifying their Tpm isoform composition.

  1. Actin is required for IFT regulation in Chlamydomonas reinhardtii.

    PubMed

    Avasthi, Prachee; Onishi, Masayuki; Karpiak, Joel; Yamamoto, Ryosuke; Mackinder, Luke; Jonikas, Martin C; Sale, Winfield S; Shoichet, Brian; Pringle, John R; Marshall, Wallace F

    2014-09-08

    Assembly of cilia and flagella requires intraflagellar transport (IFT), a highly regulated kinesin-based transport system that moves cargo from the basal body to the tip of flagella [1]. The recruitment of IFT components to basal bodies is a function of flagellar length, with increased recruitment in rapidly growing short flagella [2]. The molecular pathways regulating IFT are largely a mystery. Because actin network disruption leads to changes in ciliary length and number, actin has been proposed to have a role in ciliary assembly. However, the mechanisms involved are unknown. In Chlamydomonas reinhardtii, conventional actin is found in both the cell body and the inner dynein arm complexes within flagella [3, 4]. Previous work showed that treating Chlamydomonas cells with the actin-depolymerizing compound cytochalasin D resulted in reversible flagellar shortening [5], but how actin is related to flagellar length or assembly remains unknown. Here we utilize small-molecule inhibitors and genetic mutants to analyze the role of actin dynamics in flagellar assembly in Chlamydomonas reinhardtii. We demonstrate that actin plays a role in IFT recruitment to basal bodies during flagellar elongation and that when actin is perturbed, the normal dependence of IFT recruitment on flagellar length is lost. We also find that actin is required for sufficient entry of IFT material into flagella during assembly. These same effects are recapitulated with a myosin inhibitor, suggesting that actin may act via myosin in a pathway by which flagellar assembly is regulated by flagellar length.

  2. Reduction of exportin 6 activity leads to actin accumulation via failure of RanGTP restoration and NTF2 sequestration in the nuclei of senescent cells.

    PubMed

    Park, Su Hyun; Park, Tae Jun; Lim, In Kyoung

    2011-04-15

    We have previously reported that G-actin accumulation in nuclei is a universal phenomenon of cellular senescence. By employing primary culture of human diploid fibroblast (HDF) and stress-induced premature senescence (SIPS), we explored whether the failure of actin export to cytoplasm is responsible for actin accumulation in nuclei of senescent cells. Expression of exportin 6 (Exp6) and small G-protein, Ran, was significantly reduced in the replicative senescence, but not yet in SIPS, whereas nuclear import of actin by cofilin was already increased in SIPS. After treatment of young HDF cells with H(2)O(2), rapid reduction of nuclear RanGTP was observed along with cytoplasmic increase of RanGDP. Furthermore, significantly reduced interaction of Exp6 with RanGTP was found by GST-Exp6 pull-down analysis. Failure of RanGTP restoration was accompanied with inhibition of ATP synthesis and NTF2 sequestration in the nuclei along with accordant change of senescence morphology. Indeed, knockdown of Exp6 expression significantly increased actin molecule in the nuclei of young HDF cells. Therefore, actin accumulation in nuclei of senescent cells is most likely due to the failure of RanGTP restoration with ATP deficiency and NTF2 accumulation in nuclei, which result in the decrease of actin export via Exp6 inactivation, in addition to actin import by cofilin activation.

  3. Reduction of exportin 6 activity leads to actin accumulation via failure of RanGTP restoration and NTF2 sequestration in the nuclei of senescent cells

    SciTech Connect

    Park, Su Hyun; Park, Tae Jun; Lim, In Kyoung

    2011-04-15

    We have previously reported that G-actin accumulation in nuclei is a universal phenomenon of cellular senescence. By employing primary culture of human diploid fibroblast (HDF) and stress-induced premature senescence (SIPS), we explored whether the failure of actin export to cytoplasm is responsible for actin accumulation in nuclei of senescent cells. Expression of exportin 6 (Exp6) and small G-protein, Ran, was significantly reduced in the replicative senescence, but not yet in SIPS, whereas nuclear import of actin by cofilin was already increased in SIPS. After treatment of young HDF cells with H{sub 2}O{sub 2}, rapid reduction of nuclear RanGTP was observed along with cytoplasmic increase of RanGDP. Furthermore, significantly reduced interaction of Exp6 with RanGTP was found by GST-Exp6 pull-down analysis. Failure of RanGTP restoration was accompanied with inhibition of ATP synthesis and NTF2 sequestration in the nuclei along with accordant change of senescence morphology. Indeed, knockdown of Exp6 expression significantly increased actin molecule in the nuclei of young HDF cells. Therefore, actin accumulation in nuclei of senescent cells is most likely due to the failure of RanGTP restoration with ATP deficiency and NTF2 accumulation in nuclei, which result in the decrease of actin export via Exp6 inactivation, in addition to actin import by cofilin activation.

  4. Fibroblast-mediated contraction in actinically exposed and actinically protected aging skin

    SciTech Connect

    Marks, M.W.; Morykwas, M.J.; Wheatley, M.J. )

    1990-08-01

    The changes in skin morphology over time are a consequence of both chronologic aging and the accumulation of environmental exposure. Through observation, we know that actinic radiation intensifies the apparent aging of skin. We have investigated the effects of aging and actinic radiation on the ability of fibroblasts to contract collagen-fibroblast lattices. Preauricular and postauricular skin samples were obtained from eight patients aged 49 to 74 undergoing rhytidectomy. The samples were kept separate, and the fibroblasts were grown in culture. Lattices constructed with preauricular fibroblasts consistently contracted more than lattices containing postauricular fibroblasts. The difference in amount of contraction in 7 days between sites was greatest for the younger patients and decreased linearly as donor age increased (r = -0.96). This difference may be due to preauricular fibroblasts losing their ability to contract a lattice as aging skin is exposed to more actinic radiation.

  5. Inhibition of actin polymerization in the NAc shell inhibits morphine-induced CPP by disrupting its reconsolidation

    PubMed Central

    Li, Gongying; Wang, Yanmei; Yan, Min; Xu, Yunshuai; Song, Xiuli; Li, Qingqing; Zhang, Jinxiang; Ma, Hongxia; Wu, Yili

    2015-01-01

    Drug-associated contextual cues contribute to drug craving and relapse after abstinence, which is a major challenge to drug addiction treatment. Previous studies showed that disrupting memory reconsolidation impairs drug reward memory. However, the underlying mechanisms remain elusive. Although actin polymerization is involved in memory formation, its role in the reconsolidation of drug reward memory is unknown. In addition, the specific brain areas responsible for drug memory have not been fully identified. In the present study, we found that inhibiting actin polymerization in the nucleus accumbens (NAc) shell, but not the NAc core, abolishes morphine-induced conditioned place preference (CPP) by disrupting its reconsolidation in rats. Moreover, this effect persists for more than 2 weeks by a single injection of the actin polymerization inhibitor, which is not reversed by a morphine-priming injection. Furthermore, the application of actin polymerization inhibitor outside the reconsolidation window has no effect on morphine-associated contextual memory. Taken together, our findings first demonstrate that inhibiting actin polymerization erases morphine-induced CPP by disrupting its reconsolidation. Our study suggests that inhibition of actin polymerization during drug memory reconsolidation may be a potential approach to prevent drug relapse. PMID:26538334

  6. Inhibition of actin polymerization in the NAc shell inhibits morphine-induced CPP by disrupting its reconsolidation.

    PubMed

    Li, Gongying; Wang, Yanmei; Yan, Min; Xu, Yunshuai; Song, Xiuli; Li, Qingqing; Zhang, Jinxiang; Ma, Hongxia; Wu, Yili

    2015-11-05

    Drug-associated contextual cues contribute to drug craving and relapse after abstinence, which is a major challenge to drug addiction treatment. Previous studies showed that disrupting memory reconsolidation impairs drug reward memory. However, the underlying mechanisms remain elusive. Although actin polymerization is involved in memory formation, its role in the reconsolidation of drug reward memory is unknown. In addition, the specific brain areas responsible for drug memory have not been fully identified. In the present study, we found that inhibiting actin polymerization in the nucleus accumbens (NAc) shell, but not the NAc core, abolishes morphine-induced conditioned place preference (CPP) by disrupting its reconsolidation in rats. Moreover, this effect persists for more than 2 weeks by a single injection of the actin polymerization inhibitor, which is not reversed by a morphine-priming injection. Furthermore, the application of actin polymerization inhibitor outside the reconsolidation window has no effect on morphine-associated contextual memory. Taken together, our findings first demonstrate that inhibiting actin polymerization erases morphine-induced CPP by disrupting its reconsolidation. Our study suggests that inhibition of actin polymerization during drug memory reconsolidation may be a potential approach to prevent drug relapse.

  7. The arabidopsis ACT7 actin gene is expressed in rapidly developing tissues and responds to several external stimuli.

    PubMed Central

    McDowell, J M; An, Y Q; Huang, S; McKinney, E C; Meagher, R B

    1996-01-01

    ACT7 encodes one of the six distinct and ancient subclasses of actin protein in the complex Arabidopsis actin gene family. We determined the sequence and structure of the Arabidopsis thaliana ACT7 actin gene and investigated its tissue-specific expression and regulation. The ACT7 mRNA levels varied by 128-fold among several different tissues and organs. The highest levels of aCT7 mRNA were found in rapidly expanding vegetative organs, the lowest in pollen. A translational fusion with the 5' end of ACT 7 (1.9 kb) joined to the beta-glucuronidase reporter gene was strongly and preferentially expressed in all young, developing vegetative tissues of transgenic Arabidopsis plants. ACT7 was the only Arabidopsis actin gene strongly expressed in the hypocotyl and seed coat. Although no beta-glucuronidase expression was seen in developing ovules or immature seeds, strong expression was seen in dry seeds and immediately after imbibition in the entire seedling. ACT7 was the only Arabidopsis actin gene to respond strongly to auxin, other hormone treatments, light regime, and wounding, and may be the primary actin gene responding to external stimuli. The ACT7 promoter sequence contains a remarkable number of motifs with sequence similarity to putative phytohormone response elements. PMID:8754679

  8. Melanotic and non-melanotic malignancies of the face and external ear - A review of current treatment concepts and future options.

    PubMed

    Kolk, Andreas; Wolff, Klaus-Dietrich; Smeets, Ralf; Kesting, Marco; Hein, Rüdiger; Eckert, Alexander W

    2014-08-01

    Skin has the highest incidence and variety of tumors of all organs. Its structure is of great complexity, and every component has the potential to originate a skin neoplasm (SN). Because of its exposed nature, skin is vulnerable to carcinogenic stimuli such as UV radiation. Various entities can cause SN. Nonmelanotic skin cancers (NMSC) are the most common of all cancers, with over one million cases diagnosed annually in the US. Basal cell carcinoma (BCC) accounts for approximately 80% of all NMSC, most of the remaining 20% being squamous cell carcinoma (SCC). The skin of the head and neck is the most common site for tumors, accounting for more than 80% of all NMSC. BCC, SCC, and malignant melanomas (MM) represent 85-90% of all SN. Merkel cell tumors (MCC), lymphoepithelioma-like carcinomas of the skin (LELCS), dermato-fibro-sarcomas, leiomyosarkomas, and Kaposi-sarcomas are less frequent in the facial skin region and the external ear. Based on data from the German Federal Cancer Registry (2003/2004), 140,000 people in Germany were affected by SN (100,000 BCC, 22,000 SCC, 22,000 MM). This number increases considerably if malignant precursors, such as actinic keratosis, are included. Each year, the frequency of SN diagnosis rises by 3-7%. Among all known malignant tumors, MM exhibits the highest rate of increase in incidence. In the past, SN was primarily diagnosed in people aged 50 years or older. However, recently, the risk for developing SN has shifted, and younger people are also affected. Early diagnosis is significantly correlated with prognosis. Resection of SN creates defects that must be closed with local or microvascular flaps to avoid functional disturbing scar formation and deflection of the nose, eyelids, or lips. All therapeutic strategies for SN, the current standard for adjuvant and systemic treatment, and the management of the increasing number of patients under permanent blood thinner medication are described with regard to the treatment of SN.

  9. Use of a fusion protein between GFP and an actin-binding domain to visualize transient filamentous-actin structures.

    PubMed

    Pang, K M; Lee, E; Knecht, D A

    1998-03-26

    Many important processes in eukaryotic cells involve changes in the quantity, location and the organization of actin filaments [1] [2] [3]. We have been able to visualize these changes in live cells using a fusion protein (GFP-ABD) comprising the green fluorescent protein (GFP) of Aequorea victoria and the 25 kDa highly conserved actin-binding domain (ABD) from the amino terminus of the actin cross-linking protein ABP-120 [4]. In live cells of the soil amoeba Dictyostelium that were expressing GFP-ABD, the three-dimensional architecture of the actin cortex was clearly visualized. The pattern of GFP-ABD fluorescence in these cells coincided with that of rhodamine-phalloidin, indicating that GFP-ABD specifically binds filamentous (F) actin. On the ventral surface of non-polarized vegetative cells, a broad ring of F actin periodically assembled and contracted, whereas in polarized cells there were transient punctate F-actin structures; cells cycled between the polarized and non-polarized morphologies. During the formation of pseudopods, an increase in fluorescence intensity coincided with the initial outward deformation of the membrane. This is consistent with the models of pseudopod extension that predict an increase in the local density of actin filaments. In conclusion, GFP-ABD specifically binds F actin and allows the visualization of F-actin dynamics and cellular behavior simultaneously.

  10. Actin-Dynamics in Plant Cells: The Function of Actin-Perturbing Substances: Jasplakinolide, Chondramides, Phalloidin, Cytochalasins, and Latrunculins.

    PubMed

    Holzinger, Andreas; Blaas, Kathrin

    2016-01-01

    This chapter gives an overview of the most common F-actin-perturbing substances that are used to study actin dynamics in living plant cells in studies on morphogenesis, motility, organelle movement, or when apoptosis has to be induced. These substances can be divided into two major subclasses: F-actin-stabilizing and -polymerizing substances like jasplakinolide and chondramides and F-actin-severing compounds like chytochalasins and latrunculins. Jasplakinolide was originally isolated form a marine sponge, and can now be synthesized and has become commercially available, which is responsible for its wide distribution as membrane-permeable F-actin-stabilizing and -polymerizing agent, which may even have anticancer activities. Cytochalasins, derived from fungi, show an F-actin-severing function and many derivatives are commercially available (A, B, C, D, E, H, J), also making it a widely used compound for F-actin disruption. The same can be stated for latrunculins (A, B), derived from red sea sponges; however the mode of action is different by binding to G-actin and inhibiting incorporation into the filament. In the case of swinholide a stable complex with actin dimers is formed resulting also in severing of F-actin. For influencing F-actin dynamics in plant cells only membrane permeable drugs are useful in a broad range. We however introduce also the phallotoxins and synthetic derivatives, as they are widely used to visualize F-actin in fixed cells. A particular uptake mechanism has been shown for hepatocytes, but has also been described in siphonal giant algae. In the present chapter the focus is set on F-actin dynamics in plant cells where alterations in cytoplasmic streaming can be particularly well studied; however methods by fluorescence applications including phalloidin and antibody staining as well as immunofluorescence-localization of the inhibitor drugs are given.

  11. Actin-Dynamics in Plant Cells: The Function of Actin Perturbing Substances Jasplakinolide, Chondramides, Phalloidin, Cytochalasins, and Latrunculins

    PubMed Central

    Holzinger, Andreas; Blaas, Kathrin

    2016-01-01

    This chapter will give an overview of the most common F-actin perturbing substances, that are used to study actin dynamics in living plant cells in studies on morphogenesis, motility, organelle movement or when apoptosis has to be induced. These substances can be divided into two major subclasses – F-actin stabilizing and polymerizing substances like jasplakinolide, chondramides and F-actin severing compounds like chytochalasins and latrunculins. Jasplakinolide was originally isolated form a marine sponge, and can now be synthesized and has become commercially available, which is responsible for its wide distribution as membrane permeable F-actin stabilizing and polymerizing agent, which may even have anti-cancer activities. Cytochalasins, derived from fungi show an F-actin severing function and many derivatives are commercially available (A, B, C, D, E, H, J), also making it a widely used compound for F-actin disruption. The same can be stated for latrunculins (A, B), derived from red sea sponges, however the mode of action is different by binding to G-actin and inhibiting incorporation into the filament. In the case of swinholide a stable complex with actin dimers is formed resulting also in severing of F-actin. For influencing F-actin dynamics in plant cells only membrane permeable drugs are useful in a broad range. We however introduce also the phallotoxins and synthetic derivatives, as they are widely used to visualize F-actin in fixed cells. A particular uptake mechanism has been shown for hepatocytes, but has also been described in siphonal giant algae. In the present chapter the focus is set on F-actin dynamics in plant cells where alterations in cytoplasmic streaming can be particularly well studied; however methods by fluorescence applications including phalloidin- and antibody staining as well as immunofluorescence-localization of the inhibitor drugs are given. PMID:26498789

  12. Liquid behavior of cross-linked actin bundles.

    PubMed

    Weirich, Kimberly L; Banerjee, Shiladitya; Dasbiswas, Kinjal; Witten, Thomas A; Vaikuntanathan, Suriyanarayanan; Gardel, Margaret L

    2017-02-28

    The actin cytoskeleton is a critical regulator of cytoplasmic architecture and mechanics, essential in a myriad of physiological processes. Here we demonstrate a liquid phase of actin filaments in the presence of the physiological cross-linker, filamin. Filamin condenses short actin filaments into spindle-shaped droplets, or tactoids, with shape dynamics consistent with a continuum model of anisotropic liquids. We find that cross-linker density controls the droplet shape and deformation timescales, consistent with a variable interfacial tension and viscosity. Near the liquid-solid transition, cross-linked actin bundles show behaviors reminiscent of fluid threads, including capillary instabilities and contraction. These data reveal a liquid droplet phase of actin, demixed from the surrounding solution and dominated by interfacial tension. These results suggest a mechanism to control organization, morphology, and dynamics of the actin cytoskeleton.

  13. High Actin Concentrations in Brain Dendritic Spines and Postsynaptic Densities

    NASA Astrophysics Data System (ADS)

    Matus, Andrew; Ackermann, Marcel; Pehling, Gundula; Randolph Byers, H.; Fujiwara, Keigi

    1982-12-01

    Antibodies against actin were used to corroborate the presence of actin as a major component protein of isolated brain postsynaptic densities. The same antibodies also were used as an immunohistochemical stain to study the distribution of actin in sections of intact brain tissue. This showed two major sites where actin is concentrated: smooth muscle cells around blood vessels and postsynaptic sites. In the postsynaptic area the highest concentration of actin occurs in postsynaptic densities and there also is intense staining in the surrounding cytoplasm, especially within dendritic spines. Antiactin staining was much weaker in other parts of neurons and in glial cells. The high concentration of actin in dendritic spines may be related to shape changes that these structures have been found to undergo in response to prolonged afferent stimulation.

  14. Modeling the dynamics of dendritic actin waves in living cells

    NASA Astrophysics Data System (ADS)

    Wasnik, Vaibhav; Mukhopadhyay, Ranjan

    2014-11-01

    The actin cytoskeleton in living cells exhibits a high degree of capacity for dynamic self-organization. Recent experiments have observed propagating actin waves in Dictyostelium cells recovering from complete depolymerization of their actin cytoskeleton. The propagation of these waves appear to be dependent on a programmed recruitment of a few proteins that control actin assembly and disassembly. Such waves also arise spontaneously along the plasma membrane of the cell, and it has been suggested that actin waves enable the cell to scan a surface for particles to engulf. Based on known molecular components involved in wave propagation, we present and study a minimal reaction-diffusion model for actin wave production observed in recovering cells.

  15. F-actin retains a memory of angular order.

    PubMed Central

    Orlova, A; Egelman, E H

    2000-01-01

    Modifications can be made to F-actin that do not interfere with the binding of myosin but inhibit force generation, suggesting that actin's internal dynamics are important for muscle contraction. Observations from electron microscopy and x-ray diffraction have shown that subunits in F-actin have a relatively fixed axial rise but a variable twist. One possible explanation for this is that the actin subunits randomly exist in different discrete states of "twist, " with a significant energy barrier separating these states. This would result in very slow torsional transitions. Paracrystals impose increased order on F-actin filaments by reducing the variability in twist. By looking at filaments that have recently been dissociated from paracrystals, we find that F-actin retains a "memory" of its previous environment that persists for many seconds. This would be consistent with slow torsional transitions between discrete states of twist. PMID:10733996

  16. Identification of sucrose synthase as an actin-binding protein

    NASA Technical Reports Server (NTRS)

    Winter, H.; Huber, J. L.; Huber, S. C.; Davies, E. (Principal Investigator)

    1998-01-01

    Several lines of evidence indicate that sucrose synthase (SuSy) binds both G- and F-actin: (i) presence of SuSy in the Triton X-100-insoluble fraction of microsomal membranes (i.e. crude cytoskeleton fraction); (ii) co-immunoprecipitation of actin with anti-SuSy monoclonal antibodies; (iii) association of SuSy with in situ phalloidin-stabilized F-actin filaments; and (iv) direct binding to F-actin, polymerized in vitro. Aldolase, well known to interact with F-actin, interfered with binding of SuSy, suggesting that a common or overlapping binding site may be involved. We postulate that some of the soluble SuSy in the cytosol may be associated with the actin cytoskeleton in vivo.

  17. Quantitative Evaluation of Plant Actin Cytoskeletal Organization During Immune Signaling.

    PubMed

    Lu, Yi-Ju; Day, Brad

    2017-01-01

    High spatial and temporal resolution microscopy-based methods are valuable tools for the precise real-time imaging of changes in cellular organization in response to stimulus perception. Here, we describe a quantitative method for the evaluation of the plant actin cytoskeleton during immune stimulus perception and the activation of defense signaling. As a measure of the biotic stress-induced changes in actin filament organization, we present methods for analyzing changes in actin filament organization following elicitation of pattern-triggered immunity and effector-triggered immunity. Using these methods, it is possible to not only quantitatively evaluate changes in actin cytoskeletal organization following biotic stress perception, but to also use these protocols to assess changes in actin filament organization following perception of a wide range of stimuli, including abiotic and developmental cues. As described herein, we present an example application of this method, designed to evaluate changes in actin cytoskeletal organization following pathogen perception and immune signaling.

  18. A Robust Actin Filaments Image Analysis Framework

    PubMed Central

    Alioscha-Perez, Mitchel; Benadiba, Carine; Goossens, Katty; Kasas, Sandor; Dietler, Giovanni; Willaert, Ronnie; Sahli, Hichem

    2016-01-01

    The cytoskeleton is a highly dynamical protein network that plays a central role in numerous cellular physiological processes, and is traditionally divided into three components according to its chemical composition, i.e. actin, tubulin and intermediate filament cytoskeletons. Understanding the cytoskeleton dynamics is of prime importance to unveil mechanisms involved in cell adaptation to any stress type. Fluorescence imaging of cytoskeleton structures allows analyzing the impact of mechanical stimulation in the cytoskeleton, but it also imposes additional challenges in the image processing stage, such as the presence of imaging-related artifacts and heavy blurring introduced by (high-throughput) automated scans. However, although there exists a considerable number of image-based analytical tools to address the image processing and analysis, most of them are unfit to cope with the aforementioned challenges. Filamentous structures in images can be considered as a piecewise composition of quasi-straight segments (at least in some finer or coarser scale). Based on this observation, we propose a three-steps actin filaments extraction methodology: (i) first the input image is decomposed into a ‘cartoon’ part corresponding to the filament structures in the image, and a noise/texture part, (ii) on the ‘cartoon’ image, we apply a multi-scale line detector coupled with a (iii) quasi-straight filaments merging algorithm for fiber extraction. The proposed robust actin filaments image analysis framework allows extracting individual filaments in the presence of noise, artifacts and heavy blurring. Moreover, it provides numerous parameters such as filaments orientation, position and length, useful for further analysis. Cell image decomposition is relatively under-exploited in biological images processing, and our study shows the benefits it provides when addressing such tasks. Experimental validation was conducted using publicly available datasets, and in osteoblasts

  19. Helical buckling of actin inside filopodia generates traction.

    PubMed

    Leijnse, Natascha; Oddershede, Lene B; Bendix, Poul M

    2015-01-06

    Cells can interact with their surroundings via filopodia, which are membrane protrusions that extend beyond the cell body. Filopodia are essential during dynamic cellular processes like motility, invasion, and cell-cell communication. Filopodia contain cross-linked actin filaments, attached to the surrounding cell membrane via protein linkers such as integrins. These actin filaments are thought to play a pivotal role in force transduction, bending, and rotation. We investigated whether, and how, actin within filopodia is responsible for filopodia dynamics by conducting simultaneous force spectroscopy and confocal imaging of F-actin in membrane protrusions. The actin shaft was observed to periodically undergo helical coiling and rotational motion, which occurred simultaneously with retrograde movement of actin inside the filopodium. The cells were found to retract beads attached to the filopodial tip, and retraction was found to correlate with rotation and coiling of the actin shaft. These results suggest a previously unidentified mechanism by which a cell can use rotation of the filopodial actin shaft to induce coiling and hence axial shortening of the filopodial actin bundle.

  20. Dendritic Actin Filament Nucleation Causes Traveling Waves and Patches

    PubMed Central

    Carlsson, Anders E

    2010-01-01

    The polymerization of actin via branching at a cell membrane containing nucleation-promoting factors (NPFs) is simulated using a stochastic-growth methodology. The polymerized-actin distribution displays three types of behavior: a) traveling waves, b) moving patches, and c) random fluctuations. Increasing actin concentration causes a transition from patches to waves. The waves and patches move by a treadmilling mechanism which does not require myosin II. The effects of downregulation of key proteins on actin wave behavior are evaluated. PMID:20867207

  1. Biomimetic systems for studying actin-based motility.

    PubMed

    Upadhyaya, Arpita; van Oudenaarden, Alexander

    2003-09-16

    Actin polymerization provides a major driving force for eukaryotic cell motility. Successive intercalation of monomeric actin subunits between the plasma membrane and the filamentous actin network results in protrusions of the membrane enabling the cell to move or to change shape. One of the challenges in understanding eukaryotic cell motility is to dissect the elementary biochemical and biophysical steps that link actin polymerization to mechanical force generation. Recently, significant progress was made using biomimetic, in vitro systems that are inspired by the actin-based motility of bacterial pathogens such as Listeria monocytogenes. Polystyrene microspheres and synthetic phospholipid vesicles coated with proteins that initiate actin polymerization display motile behavior similar to Listeria, mimicking the leading edge of lamellipodia and filopodia. A major advantage of these biomimetic systems is that both biochemical and physical parameters can be controlled precisely. These systems provide a test bed for validating theoretical models on force generation and polarity establishment resulting from actin polymerization. In this review, we discuss recent experimental progress using biomimetic systems propelled by actin polymerization and discuss these results in the light of recent theoretical models on actin-based motility.

  2. What we talk about when we talk about nuclear actin

    PubMed Central

    Belin, Brittany J; Mullins, R Dyche

    2013-01-01

    In the cytoplasm, actin filaments form crosslinked networks that enable eukaryotic cells to transport cargo, change shape, and move. Actin is also present in the nucleus but, in this compartment, its functions are more cryptic and controversial. If we distill the substantial literature on nuclear actin down to its essentials, we find four, recurring, and more-or-less independent, claims: (1) crosslinked networks of conventional actin filaments span the nucleus and help maintain its structure and organize its contents; (2) assembly or contraction of filaments regulates specific nuclear events; (3) actin monomers moonlight as subunits of chromatin remodeling complexes, independent of their ability to form filaments; and (4) modified actin monomers or oligomers, structurally distinct from canonical, cytoskeletal filaments, mediate nuclear events by unknown mechanisms. We discuss the evidence underlying these claims and as well as their strengths and weaknesses. Next, we describe our recent work, in which we built probes specific for nuclear actin and used them to describe the form and distribution of actin in somatic cell nuclei. Finally, we discuss how different forms of nuclear actin may play different roles in different cell types and physiological contexts. PMID:23934079

  3. Myosin Vs organize actin cables in fission yeast

    PubMed Central

    Lo Presti, Libera; Chang, Fred; Martin, Sophie G.

    2012-01-01

    Myosin V motors are believed to contribute to cell polarization by carrying cargoes along actin tracks. In Schizosaccharomyces pombe, Myosin Vs transport secretory vesicles along actin cables, which are dynamic actin bundles assembled by the formin For3 at cell poles. How these flexible structures are able to extend longitudinally in the cell through the dense cytoplasm is unknown. Here we show that in myosin V (myo52 myo51) null cells, actin cables are curled, bundled, and fail to extend into the cell interior. They also exhibit reduced retrograde flow, suggesting that formin-mediated actin assembly is impaired. Myo52 may contribute to actin cable organization by delivering actin regulators to cell poles, as myoV∆ defects are partially suppressed by diverting cargoes toward cell tips onto microtubules with a kinesin 7–Myo52 tail chimera. In addition, Myo52 motor activity may pull on cables to provide the tension necessary for their extension and efficient assembly, as artificially tethering actin cables to the nuclear envelope via a Myo52 motor domain restores actin cable extension and retrograde flow in myoV mutants. Together these in vivo data reveal elements of a self-organizing system in which the motors shape their own tracks by transporting cargoes and exerting physical pulling forces. PMID:23051734

  4. A structural study of F-actin - filamin networks

    NASA Astrophysics Data System (ADS)

    Ahrens-Braunstein, Ashley; Nguyen, Lam; Hirst, Linda

    2010-03-01

    The cell's ability to move and contract is attributed to the semi-flexible filamentous protein, F -actin, one of the three filaments in the cytoskeleton. Actin bundling can be formed by a cross-linking actin binding protein (ABP) filamin. By examining filamin's cross-linking abilities at different concentrations and molar ratios, we can study the flexibility, structure and multiple network formations created when cross-linking F-actin with this protein. We have studied the phase diagram of this protein system using fluorescence microscopy, analyzing the network structures observed in the context of a coarse grained molecular dynamics simulation carried out by our group.

  5. Correlative nanoscale imaging of actin filaments and their complexes

    NASA Astrophysics Data System (ADS)

    Sharma, Shivani; Zhu, Huanqi; Grintsevich, Elena E.; Reisler, Emil; Gimzewski, James K.

    2013-06-01

    Actin remodeling is an area of interest in biology in which correlative microscopy can bring a new way to analyze protein complexes at the nanoscale. Advances in EM, X-ray diffraction, fluorescence, and single molecule techniques have provided a wealth of information about the modulation of the F-actin structure and its regulation by actin binding proteins (ABPs). Yet, there are technological limitations of these approaches to achieving quantitative molecular level information on the structural and biophysical changes resulting from ABPs interaction with F-actin. Fundamental questions about the actin structure and dynamics and how these determine the function of ABPs remain unanswered. Specifically, how local and long-range structural and conformational changes result in ABPs induced remodeling of F-actin needs to be addressed at the single filament level. Advanced, sensitive and accurate experimental tools for detailed understanding of ABP-actin interactions are much needed. This article discusses the current understanding of nanoscale structural and mechanical modulation of F-actin by ABPs at the single filament level using several correlative microscopic techniques, focusing mainly on results obtained by Atomic Force Microscopy (AFM) analysis of ABP-actin complexes.

  6. WH2 domain: a small, versatile adapter for actin monomers.

    PubMed

    Paunola, Eija; Mattila, Pieta K; Lappalainen, Pekka

    2002-02-20

    The actin cytoskeleton plays a central role in many cell biological processes. The structure and dynamics of the actin cytoskeleton are regulated by numerous actin-binding proteins that usually contain one of the few known actin-binding motifs. WH2 domain (WASP homology domain-2) is a approximately 35 residue actin monomer-binding motif, that is found in many different regulators of the actin cytoskeleton, including the beta-thymosins, ciboulot, WASP (Wiskott Aldrich syndrome protein), verprolin/WIP (WASP-interacting protein), Srv2/CAP (adenylyl cyclase-associated protein) and several uncharacterized proteins. The most highly conserved residues in the WH2 domain are important in beta-thymosin's interactions with actin monomers, suggesting that all WH2 domains may interact with actin monomers through similar interfaces. Our sequence database searches did not reveal any WH2 domain-containing proteins in plants. However, we found three classes of these proteins: WASP, Srv2/CAP and verprolin/WIP in yeast and animals. This suggests that the WH2 domain is an ancient actin monomer-binding motif that existed before the divergence of fungal and animal lineages.

  7. Traveling waves in actin dynamics and cell motility

    PubMed Central

    Allard, Jun; Mogilner, Alex

    2012-01-01

    Much of current understanding of cell motility arose from studying steady treadmilling of actin arrays. Recently, there have been a growing number of observations of a more complex, non-steady, actin behavior, including self-organized waves. It is becoming clear that these waves result from activation and inhibition feedbacks in actin dynamics acting on different scales, but the exact molecular nature of these feedbacks and respective roles of biomechanics and biochemistry are still unclear. Here, we review recent advances achieved in experimental and theoretical studies of actin waves and discuss mechanisms and physiological significance of wavy protrusions. PMID:22985541

  8. Helical buckling of actin inside filopodia generates traction

    PubMed Central

    Leijnse, Natascha; Oddershede, Lene B.; Bendix, Poul M.

    2015-01-01

    Cells can interact with their surroundings via filopodia, which are membrane protrusions that extend beyond the cell body. Filopodia are essential during dynamic cellular processes like motility, invasion, and cell–cell communication. Filopodia contain cross-linked actin filaments, attached to the surrounding cell membrane via protein linkers such as integrins. These actin filaments are thought to play a pivotal role in force transduction, bending, and rotation. We investigated whether, and how, actin within filopodia is responsible for filopodia dynamics by conducting simultaneous force spectroscopy and confocal imaging of F-actin in membrane protrusions. The actin shaft was observed to periodically undergo helical coiling and rotational motion, which occurred simultaneously with retrograde movement of actin inside the filopodium. The cells were found to retract beads attached to the filopodial tip, and retraction was found to correlate with rotation and coiling of the actin shaft. These results suggest a previously unidentified mechanism by which a cell can use rotation of the filopodial actin shaft to induce coiling and hence axial shortening of the filopodial actin bundle. PMID:25535347

  9. Interaction of calponin with actin and its functional implications.

    PubMed Central

    Kołakowski, J; Makuch, R; Stepkowski, D; Dabrowska, R

    1995-01-01

    Titration of F-actin with calponin causes the formation of two types of complexes. One, at saturation, contains a lower ratio of calponin to actin (0.5:1) and is insoluble at physiological ionic strength. The another is soluble, with a higher ratio of calponin to actin (1:1). Electron microscopy revealed that the former complex consists of paracrystalline bundles of actin filaments, whereas the latter consists of separate filaments. Ca(2+)-calmodulin causes dissociation of bundles with simultaneous increase in the number of separate calponin-containing filaments. Further increase in the calmodulin concentration results in full release of calponin from actin filaments. In motility assays, calponin, when added together with ATP to actin filaments complexed with immobilized myosin, evoked a decrease in both the number and velocity of moving actin filaments. Addition of calponin to actin filaments before their binding to myosin resulted in a formation of actin filament bundles which were dissociated by ATP. Images Figure 2 PMID:7864810

  10. Arp2/3 complex and actin dynamics are required for actin-based mitochondrial motility in yeast

    PubMed Central

    Boldogh, Istvan R.; Yang, Hyeong-Cheol; Nowakowski, W. Dan; Karmon, Sharon L.; Hays, Lara G.; Yates, John R.; Pon, Liza A.

    2001-01-01

    The Arp2/3 complex is implicated in actin polymerization-driven movement of Listeria monocytogenes. Here, we find that Arp2p and Arc15p, two subunits of this complex, show tight, actin-independent association with isolated yeast mitochondria. Arp2p colocalizes with mitochondria. Consistent with this result, we detect Arp2p-dependent formation of actin clouds around mitochondria in intact yeast. Cells bearing mutations in ARP2 or ARC15 genes show decreased velocities of mitochondrial movement, loss of all directed movement and defects in mitochondrial morphology. Finally, we observe a decrease in the velocity and extent of mitochondrial movement in yeast in which actin dynamics are reduced but actin cytoskeletal structure is intact. These results support the idea that the movement of mitochondria in yeast is actin polymerization driven and that this movement requires Arp2/3 complex. PMID:11248049

  11. Visualization of Actin Cytoskeletal Dynamics in Fixed and Live Drosophila Egg Chambers.

    PubMed

    Groen, Christopher M; Tootle, Tina L

    2015-01-01

    Visualization of actin cytoskeletal dynamics is critical for understanding the spatial and temporal regulation of actin remodeling. Drosophila oogenesis provides an excellent model system for visualizing the actin cytoskeleton. Here, we present methods for imaging the actin cytoskeleton in Drosophila egg chambers in both fixed samples by phalloidin staining and in live egg chambers using transgenic actin labeling tools.

  12. Linking cellular actin status with cAMP signaling in Candida albicans.

    PubMed

    Wang, Yue; Zou, Hao; Fang, Hao-Ming; Zhu, Yong

    2010-01-01

    The fungal pathogen Candida albicans has a remarkable ability to switch growth forms. Particularly, the yeast-to-hyphae switch is closely linked with its virulence. A range of chemicals and conditions can promote hyphal growth including serum, peptidoglycan, CO2, neutral pH, and elevated temperature. All these signals act essentially through the adenylyl cyclase Cyr1 that synthesizes cAMP. Cells lacking Cyr1 are completely defective in hyphal growth. Recently, cellular actin status is found to influence cAMP synthesis. However, how Cyr1 senses and processes multiple external and internal signals to produce a contextually proper level of cAMP remains unclear. We hypothesized that Cyr1 itself possesses multiple sensors for different signals and achieves signal integration through a combined allosteric effect on the catalytic center. To test this hypothesis, we affinity-purified a Cyr1-containing complex and found that it could enhance cAMP synthesis upon treatment with serum, peptidoglycan or CO2 in vitro. The data indicate that the complex is an essentially intact sensor/effector apparatus for cAMP synthesis. The complex contains two more subunits, the cyclase-associated protein Cap1 and G-actin. We discovered that G-actin plays a regulatory role, rendering cAMP synthesis responsive to actin dynamics. These findings shed new lights on the mechanisms that regulate cAMP-mediated responses in fungi.

  13. Dynamin 2 is required for actin assembly in phagocytosis in Sertoli cells

    SciTech Connect

    Otsuka, Atsushi; Abe, Tadashi; Watanabe, Masami; Yagisawa, Hitoshi; Takei, Kohji; Yamada, Hiroshi

    2009-01-16

    Dynamin 2 has been reported to be implicated in phagocytosis. However, the mode of action of dynamin is poorly understood. In this study, we examined whether dynamin 2 participates in actin assembly during phagocytosis in Sertoli cells. In the presence of dynasore, a dynamin inhibitor, phagocytosis was reduced by 60-70% in Sertoli cells and macrophages. Scanning electron microscopy revealed that Sertoli cells treated with dynasore were unable to form phagocytic cups. In addition, dysfunction of dynamin 2 reduced both actin polymerization and recruitment of actin and dynamin 2 to phosphatidylinositol (4,5) bisphosphate [PI(4,5)P{sub 2}]-containing liposomes. The formation of dynamin 2-positive ruffles of Sertoli cells was decreased by 60-70% by sequestering PI(4,5)P{sub 2} either by expression of PH domain of PLC{delta} or treatment with neomycin. These results strongly suggest that dynamin 2 is involved in actin dynamics and the formation of dynamin 2-positive ruffles during phagocytosis.

  14. Nucleocapsid of Tomato spotted wilt tospovirus forms mobile particles that traffic on an actin/endoplasmic reticulum network driven by myosin XI-K.

    PubMed

    Feng, Zhike; Chen, Xiaojiao; Bao, Yiqun; Dong, Jiahong; Zhang, Zhongkai; Tao, Xiaorong

    2013-12-01

    A number of viral proteins from plant viruses, other than movement proteins, have been shown to traffic intracellularly along actin filaments and to be involved in viral infection. However, there has been no report that a viral capsid protein may traffic within a cell by utilizing the actin/endoplasmic reticulum (ER) network. We used Tomato spotted wilt tospovirus (TSWV) as a model virus to study the cell biological properties of a nucleocapsid (N) protein. We found that TSWV N protein was capable of forming highly motile cytoplasmic inclusions that moved along the ER and actin network. The disruption of actin filaments by latrunculin B, an actin-depolymerizing agent, almost stopped the intracellular movement of N inclusions, whereas treatment with a microtubule-depolymerizing reagent, oryzalin, did not. The over-expression of a myosin XI-K tail, functioning in a dominant-negative manner, completely halted the movement of N inclusions. Latrunculin B treatment strongly inhibited the formation of TSWV local lesions in Nicotiana tabacum cv Samsun NN and delayed systemic infection in N. benthamiana. Collectively, our findings provide the first evidence that the capsid protein of a plant virus has the novel property of intracellular trafficking. The findings add capsid protein as a new class of viral protein that traffics on the actin/ER system.

  15. Role of Cyclic Nucleotide-Dependent Actin Cytoskeletal Dynamics: [Ca2+]i and Force Suppression in Forskolin-Pretreated Porcine Coronary Arteries

    PubMed Central

    Hocking, Kyle M.; Baudenbacher, Franz J.; Putumbaka, Gowthami; Venkatraman, Sneha; Cheung-Flynn, Joyce; Brophy, Colleen M.; Komalavilas, Padmini

    2013-01-01

    Initiation of force generation during vascular smooth muscle contraction involves a rise in intracellular calcium ([Ca2+]i) and phosphorylation of myosin light chains (MLC). However, reversal of these two processes alone does not account for the force inhibition that occurs during relaxation or inhibition of contraction, implicating that other mechanisms, such as actin cytoskeletal rearrangement, play a role in the suppression of force. In this study, we hypothesize that forskolin-induced force suppression is dependent upon changes in actin cytoskeletal dynamics. To focus on the actin cytoskeletal changes, a physiological model was developed in which forskolin treatment of intact porcine coronary arteries (PCA) prior to treatment with a contractile agonist resulted in complete suppression of force. Pretreatment of PCA with forskolin suppressed histamine-induced force generation but did not abolish [Ca2+]i rise or MLC phosphorylation. Additionally, forskolin pretreatment reduced filamentous actin in histamine-treated tissues, and prevented histamine-induced changes in the phosphorylation of the actin-regulatory proteins HSP20, VASP, cofilin, and paxillin. Taken together, these results suggest that forskolin-induced complete force suppression is dependent upon the actin cytoskeletal regulation initiated by the phosphorylation changes of the actin regulatory proteins and not on the MLC dephosphorylation. This model of complete force suppression can be employed to further elucidate the mechanisms responsible for smooth muscle tone, and may offer cues to pathological situations, such as hypertension and vasospasm. PMID:23593369

  16. Role of cyclic nucleotide-dependent actin cytoskeletal dynamics:Ca(2+)](i) and force suppression in forskolin-pretreated porcine coronary arteries.

    PubMed

    Hocking, Kyle M; Baudenbacher, Franz J; Putumbaka, Gowthami; Venkatraman, Sneha; Cheung-Flynn, Joyce; Brophy, Colleen M; Komalavilas, Padmini

    2013-01-01

    Initiation of force generation during vascular smooth muscle contraction involves a rise in intracellular calcium ([Ca(2+)]i) and phosphorylation of myosin light chains (MLC). However, reversal of these two processes alone does not account for the force inhibition that occurs during relaxation or inhibition of contraction, implicating that other mechanisms, such as actin cytoskeletal rearrangement, play a role in the suppression of force. In this study, we hypothesize that forskolin-induced force suppression is dependent upon changes in actin cytoskeletal dynamics. To focus on the actin cytoskeletal changes, a physiological model was developed in which forskolin treatment of intact porcine coronary arteries (PCA) prior to treatment with a contractile agonist resulted in complete suppression of force. Pretreatment of PCA with forskolin suppressed histamine-induced force generation but did not abolish [Ca(2+)]i rise or MLC phosphorylation. Additionally, forskolin pretreatment reduced filamentous actin in histamine-treated tissues, and prevented histamine-induced changes in the phosphorylation of the actin-regulatory proteins HSP20, VASP, cofilin, and paxillin. Taken together, these results suggest that forskolin-induced complete force suppression is dependent upon the actin cytoskeletal regulation initiated by the phosphorylation changes of the actin regulatory proteins and not on the MLC dephosphorylation. This model of complete force suppression can be employed to further elucidate the mechanisms responsible for smooth muscle tone, and may offer cues to pathological situations, such as hypertension and vasospasm.

  17. Assessment of Actin FS and Actin FSL sensitivity to specific clotting factor deficiencies.

    PubMed

    Lawrie, A S; Kitchen, S; Purdy, G; Mackie, I J; Preston, F E; Machin, S J

    1998-06-01

    We present a two centre study designed to assess the sensitivity of Actin FS and Actin FSL to deficiencies of factor VIII, IX, XI or XII. The study was undertaken at two centres to avoid bias due to the investigations being undertaken on one analyser. Samples from patients with a factor VIII (n = 36, F VIII = < 1.0-50 iu/dl), factor IX (n = 22, F IX = 2-48 iu/dl), factor XI (n = 23, F XI = 5-50 u/dl) or a factor XII (n = 18, F XII = 1-50 u/dl) deficient state were studied. Activated partial thromboplastin times (APTT) were determined using two batches of Actin FS and of Actin FSL; comparison of APTT results between centres was facilitated by the conversion of clotting times to ratios (test divided by geometric mean normal clotting time). APTT ratios were considered to be elevated if greater than two standard deviations above the mean normal. The factor deficient status of each sample was verified by assaying all samples for factors VIII, IX, XI and XII. Clotting factor assays were performed on a Sysmex CA-1000 fitted with research software, which permitted the auto-dilution and testing of three serial dilution of both a reference preparation and each patient's sample. Assay results were calculated using parallel-line Bioassay principles. This procedure allowed for variation in clotting times due to the effect of temporal drift of any of the reagents within the assay system. Actin FS and Actin FSL demonstrate acceptable sensitivity to factor VIII deficiency, however, both reagents failed to detect a large proportion of factor XI (17.4% and 30.4% of samples, respectively) and factor XII (66.7% and 72.2%, respectively) deficiencies. The detection rate with Actin FSL for factor IX deficiency was also poor (36.4% not detected). As factor IX and XI deficiencies are both associated with haemorrhagic disorders, the inability of these reagents to detect such abnormalities gave cause for concern.

  18. Human CAP1 is a key factor in the recycling of cofilin and actin for rapid actin turnover.

    PubMed

    Moriyama, Kenji; Yahara, Ichiro

    2002-04-15

    Cofilin-ADF (actin-depolymerizing factor) is an essential driver of actin-based motility. We discovered two proteins, p65 and p55, that are components of the actin-cofilin complex in a human HEK293 cell extract and identified p55 as CAP1/ASP56, a human homologue of yeast CAP/SRV2 (cyclase-associated protein). CAP is a bifunctional protein with an N-terminal domain that binds to Ras-responsive adenylyl cyclase and a C-terminal domain that inhibits actin polymerization. Surprisingly, we found that the N-terminal domain of CAP1, but not the C-terminal domain, is responsible for the interaction with the actin-cofilin complex. The N-terminal domain of CAP1 was also found to accelerate the depolymerization of F-actin at the pointed end, which was further enhanced in the presence of cofilin and/or the C-terminal domain of CAP1. Moreover, CAP1 and its C-terminal domain were observed to facilitate filament elongation at the barbed end and to stimulate ADP-ATP exchange on G-actin, a process that regenerates easily polymerizable G-actin. Although cofilin inhibited the nucleotide exchange on G-actin even in the presence of the C-terminal domain of CAP1, its N-terminal domain relieved this inhibition. Thus, CAP1 plays a key role in speeding up the turnover of actin filaments by effectively recycling cofilin and actin and through its effect on both ends of actin filament.

  19. Superinfection Exclusion in Alphabaculovirus Infections Is Concomitant with Actin Reorganization

    PubMed Central

    Beperet, Inés; Irons, Sarah L.; Simón, Oihane; King, Linda A.; Williams, Trevor; Possee, Robert D.; Caballero, Primitivo

    2014-01-01

    ABSTRACT Superinfection exclusion is the ability of an established virus to interfere with a second virus infection. This effect was studied in vitro during lepidopteran-specific nucleopolyhedrovirus (genus Alphabaculovirus, family Baculoviridae) infection. Homologous interference was detected in Sf9 cells sequentially infected with two genotypes of Autographa californica multiple nucleopolyhedrovirus (AcMNPV), each one expressing a different fluorescent protein. This was a progressive process in which a sharp decrease in the signs of infection caused by the second virus was observed, affecting not only the number of coinfected cells observed, but also the level of protein expression due to the second virus infection. Superinfection exclusion was concurrent with reorganization of cytoplasmic actin to F-actin in the nucleus, followed by budded virus production (16 to 20 h postinfection). Disruption of actin filaments by cell treatment with cytochalasin D resulted in a successful second infection. Protection against heterologous nucleopolyhedrovirus infection was also demonstrated, as productive infection of Sf9 cells by Spodoptera frugiperda nucleopolyhedrovirus (SfMNPV) was inhibited by prior infection with AcMNPV, and vice versa. Finally, coinfected cells were observed following inoculation with mixtures of these two phylogenetically distant nucleopolyhedroviruses—AcMNPV and SfMNPV—but at a frequency lower than predicted, suggesting interspecific virus interference during infection or replication. The temporal window of infection is likely necessary to maintain genotypic diversity that favors virus survival but also permits dual infection by heterospecific alphabaculoviruses. IMPORTANCE Infection of a cell by more than one virus particle implies sharing of cell resources. We show that multiple infection, by closely related or distantly related baculoviruses, is possible only during a brief window of time that allows additional virus particles to enter an

  20. Myosin IIIB uses an actin-binding motif in its espin-1 cargo to reach the tips of actin protrusions.

    PubMed

    Merritt, Raymond C; Manor, Uri; Salles, Felipe T; Grati, M'hamed; Dose, Andrea C; Unrath, William C; Quintero, Omar A; Yengo, Christopher M; Kachar, Bechara

    2012-02-21

    Myosin IIIA (MYO3A) targets actin protrusion tips using a motility mechanism dependent on both motor and tail actin-binding activity [1]. We show that myosin IIIB (MYO3B) lacks tail actin-binding activity and is unable to target COS7 cell filopodia tips, yet is somehow able to target stereocilia tips. Strikingly, when MYO3B is coexpressed with espin-1 (ESPN1), a MYO3A cargo protein endogenously expressed in stereocilia [2], MYO3B targets and carries ESPN1 to COS7 filopodia tips. We show that this tip localization is lost when we remove the ESPN1 C terminus actin-binding site. We also demonstrate that, like MYO3A [2], MYO3B can elongate filopodia by transporting ESPN1 to the polymerizing end of actin filaments. The mutual dependence of MYO3B and ESPN1 for tip localization reveals a novel mechanism for the cell to regulate myosin tip localization via a reciprocal relationship with cargo that directly participates in actin binding for motility. Our results are consistent with a novel form of motility for class III myosins that requires both motor and tail domain actin-binding activity and show that the actin-binding tail can be replaced by actin-binding cargo. This study also provides a framework to better understand the late-onset hearing loss phenotype in patients with MYO3A mutations.

  1. A small molecule inhibitor of tropomyosin dissociates actin binding from tropomyosin-directed regulation of actin dynamics

    PubMed Central

    Bonello, Teresa T.; Janco, Miro; Hook, Jeff; Byun, Alex; Appaduray, Mark; Dedova, Irina; Hitchcock-DeGregori, Sarah; Hardeman, Edna C.; Stehn, Justine R.; Böcking, Till; Gunning, Peter W.

    2016-01-01

    The tropomyosin family of proteins form end-to-end polymers along the actin filament. Tumour cells rely on specific tropomyosin-containing actin filament populations for growth and survival. To dissect out the role of tropomyosin in actin filament regulation we use the small molecule TR100 directed against the C terminus of the tropomyosin isoform Tpm3.1. TR100 nullifies the effect of Tpm3.1 on actin depolymerisation but surprisingly Tpm3.1 retains the capacity to bind F-actin in a cooperative manner. In vivo analysis also confirms that, in the presence of TR100, fluorescently tagged Tpm3.1 recovers normally into stress fibers. Assembling end-to-end along the actin filament is thereby not sufficient for tropomyosin to fulfil its function. Rather, regulation of F-actin stability by tropomyosin requires fidelity of information communicated at the barbed end of the actin filament. This distinction has significant implications for perturbing tropomyosin-dependent actin filament function in the context of anti-cancer drug development. PMID:26804624

  2. Recent advances into vanadyl, vanadate and decavanadate interactions with actin.

    PubMed

    Ramos, S; Moura, J J G; Aureliano, M

    2012-01-01

    Although the number of papers about "vanadium" has doubled in the last decade, the studies about "vanadium and actin" are scarce. In the present review, the effects of vanadyl, vanadate and decavanadate on actin structure and function are compared. Decavanadate (51)V NMR signals, at -516 ppm, broadened and decreased in intensity upon actin titration, whereas no effects were observed for vanadate monomers, at -560 ppm. Decavanadate is the only species inducing actin cysteine oxidation and vanadyl formation, both processes being prevented by the natural ligand of the protein, ATP. Vanadyl titration with monomeric actin (G-actin), analysed by EPR spectroscopy, reveals a 1:1 binding stoichiometry and a K(d) of 7.5 μM(-1). Both decavanadate and vanadyl inhibited G-actin polymerization into actin filaments (F-actin), with a IC(50) of 68 and 300 μM, respectively, as analysed by light scattering assays, whereas no effects were detected for vanadate up to 2 mM. However, only vanadyl (up to 200 μM) induces 100% of G-actin intrinsic fluorescence quenching, whereas decavanadate shows an opposite effect, which suggests the presence of vanadyl high affinity actin binding sites. Decavanadate increases (2.6-fold) the actin hydrophobic surface, evaluated using the ANSA probe, whereas vanadyl decreases it (15%). Both vanadium species increased the ε-ATP exchange rate (k = 6.5 × 10(-3) s(-1) and 4.47 × 10(-3) s(-1) for decavanadate and vanadyl, respectively). Finally, (1)H NMR spectra of G-actin treated with 0.1 mM decavanadate clearly indicate that major alterations occur in protein structure, which are much less visible in the presence of ATP, confirming the preventive effect of the nucleotide on the decavanadate interaction with the protein. Putting it all together, it is suggested that actin, which is involved in many cellular processes, might be a potential target not only for decavanadate but above all for vanadyl. By affecting actin structure and function, vanadium can

  3. Actin Foci Adhesion of D. discoideum

    NASA Astrophysics Data System (ADS)

    Flanders, Bret; Paneru, Govind

    2014-03-01

    Amoeboid migration is a fast (10 μm min-1) integrin-independent mode of migration that is important with D. discoideum, leukocytes, and breast cancer cells. It is poorly understood, but depends on the establishment of adhesive contacts to the substrate where the cell transmits traction forces. In pre-aggregative D. discoideum, a model system for learning about amoeboid migration, these adhesive contacts are discrete complexes that are known as actin-foci. They have an area of ~ 0.5 μm2 and a lifetime of ~ 20 s. This talk will present measurements of the adhesive character of actin foci that have been obtained using a submicron force transducer that was designed for this purpose. Results on the rupture stresses and lifetimes of individual acting foci under nano-newton level forces will be described in the context of a general theory for cellular adhesion. This theory depends on, essentially, three cellular properties: the membrane-medium surface tension, the number density of adhesion receptors in the membrane, and the receptor-substrate potential energy surface. Therefore, the use of the transducer to determine the surface tension will be presented, as well.

  4. Actin and Endocytosis in Budding Yeast

    PubMed Central

    Goode, Bruce L.; Eskin, Julian A.; Wendland, Beverly

    2015-01-01

    Endocytosis, the process whereby the plasma membrane invaginates to form vesicles, is essential for bringing many substances into the cell and for membrane turnover. The mechanism driving clathrin-mediated endocytosis (CME) involves > 50 different protein components assembling at a single location on the plasma membrane in a temporally ordered and hierarchal pathway. These proteins perform precisely choreographed steps that promote receptor recognition and clustering, membrane remodeling, and force-generating actin-filament assembly and turnover to drive membrane invagination and vesicle scission. Many critical aspects of the CME mechanism are conserved from yeast to mammals and were first elucidated in yeast, demonstrating that it is a powerful system for studying endocytosis. In this review, we describe our current mechanistic understanding of each step in the process of yeast CME, and the essential roles played by actin polymerization at these sites, while providing a historical perspective of how the landscape has changed since the preceding version of the YeastBook was published 17 years ago (1997). Finally, we discuss the key unresolved issues and where future studies might be headed. PMID:25657349

  5. Actin binding proteins, spermatid transport and spermiation*

    PubMed Central

    Qian, Xiaojing; Mruk, Dolores D.; Cheng, Yan-Ho; Tang, Elizabeth I.; Han, Daishu; Lee, Will M.; Wong, Elissa W. P.; Cheng, C. Yan

    2014-01-01

    The transport of germ cells across the seminiferous epithelium is composed of a series of cellular events during the epithelial cycle essential to the completion of spermatogenesis. Without the timely transport of spermatids during spermiogenesis, spermatozoa that are transformed from step 19 spermatids in the rat testis fail to reach the luminal edge of the apical compartment and enter the tubule lumen at spermiation, thereby entering the epididymis for further maturation. Step 19 spermatids and/or sperms that remain in the epithelium will be removed by the Sertoli cell via phagocytosis to form phagosomes and be degraded by lysosomes, leading to subfertility and/or infertility. However, the biology of spermatid transport, in particular the final events that lead to spermiation remain elusive. Based on recent data in the field, we critically evaluate the biology of spermiation herein by focusing on the actin binding proteins (ABPs) that regulate the organization of actin microfilaments at the Sertoli-spermatid interface, which is crucial for spermatid transport during this event. The hypothesis we put forth herein also highlights some specific areas of research that can be pursued by investigators in the years to come. PMID:24735648

  6. Self-assembly of Artificial Actin Filaments

    NASA Astrophysics Data System (ADS)

    Grosenick, Christopher; Cheng, Shengfeng

    Actin Filaments are long, double-helical biopolymers that make up the cytoskeleton along with microtubules and intermediate filaments. In order to further understand the self-assembly process of these biopolymers, a model to recreate actin filament geometry was developed. A monomer in the shape of a bent rod with vertical and lateral binding sites was designed to assemble into single or double helices. With Molecular Dynamics simulations, a variety of phases were observed to form by varying the strength of the binding sites. Ignoring lateral binding sites, we have found a narrow range of binding strengths that lead to long single helices via various growth pathways. When lateral binding strength is introduced, double helices begin to form. These double helices self-assemble into substantially more stable structures than their single helix counterparts. We have found double helices to form long filaments at about half the vertical binding strength of single helices. Surprisingly, we have found that triple helices occasionally form, indicating the importance of structural regulation in the self-assembly of biopolymers.

  7. Encoding Mechano-Memories in Actin Networks

    NASA Astrophysics Data System (ADS)

    Foucard, Louis; Majumdar, Sayantan; Levine, Alex; Gardel, Margaret

    The ability of cells to sense and adapt to external mechanical stimuli is vital to many of its biological functions. A critical question is therefore to understand how mechanosensory mechanisms arise in living matter, with implications in both cell biology and smart materials design. Experimental work has demonstrated that the mechanical properties of semiflexible actin networks in Eukaryotic cells can be modulated (either transiently or irreversibly) via the application of external forces. Previous work has also shown with a combination of numerical simulations and analytic calculations shows that the broken rotational symmetry of the filament orientational distribution in semiflexible networks leads to dramatic changes in the mechanical response. Here we demonstrate with a combination of numerical and analytic calculations that the observed long-lived mechano-memory in the actin networks arise from changes in the nematic order of the constituent filaments. These stress-induced changes in network topology relax slowly under zero stress and can be observed through changes in the nonlinear mechanics. Our results provide a strategy for designing a novel class of materials and demonstrate a new putative mechanism of mechanical sensing in eukaryotic cells.

  8. Mechanism of interaction of Dictyostelium severin with actin filaments

    PubMed Central

    1982-01-01

    Severin, a 40,000-dalton protein from Dictyostelium that disassembles actin filaments in a Ca2+ -dependent manner, was purified 500-fold to greater than 99% homogeneity by modifications of the procedure reported by Brown, Yamamoto, and Spudich (1982. J. Cell Biol. 93:205-210). Severin has a Stokes radius of 29 A and consists of a single polypeptide chain. It contains a single methionyl and five cysteinyl residues. We studied the action of severin on actin filaments by electron microscopy, viscometry, sedimentation, nanosecond emission anisotropy, and fluorescence energy transfer spectroscopy. Nanosecond emission anisotropy of fluoresence-labeled severin shows that this protein changes its conformation on binding Ca2+. Actin filaments are rapidly fragmented on addition of severin and Ca2+, but severin does not interact with actin filaments in the absence of Ca2+. Fluorescence energy transfer measurements indicate that fragmentation of actin filaments by severin leads to a partial depolymerization (t1/2 approximately equal to 30 s). Depolymerization is followed by exchange of a limited number of subunits in the filament fragments with the disassembled actin pool (t1/2 approximately equal to 5 min). Disassembly and exchange are probably restricted to the ends of the filament fragments since only a few subunits in each fragment participate in the disassembly or exchange process. Steady state hydrolysis of ATP by actin in the presence of Ca2+-severin is maximal at an actin: severin molar ratio of approximately 10:1, which further supports the inference that subunit exchange is limited to the ends of actin filaments. The observation of sequential depolymerization and subunit exchange following the fragmentation of actin by severin suggests that severin may regulate site-specific disassembly and turnover of actin filament arrays in vivo. PMID:6897549

  9. Targeting the actin cytoskeleton: selective antitumor action via trapping PKCɛ

    PubMed Central

    Foerster, F; Braig, S; Moser, C; Kubisch, R; Busse, J; Wagner, E; Schmoeckel, E; Mayr, D; Schmitt, S; Huettel, S; Zischka, H; Mueller, R; Vollmar, A M

    2014-01-01

    Targeting the actin cytoskeleton (CSK) of cancer cells offers a valuable strategy in cancer therapy. There are a number of natural compounds that interfere with the actin CSK, but the mode of their cytotoxic action and, moreover, their tumor-specific mechanisms are quite elusive. We used the myxobacterial compound Chondramide as a tool to first elucidate the mechanisms of cytotoxicity of actin targeting in breast cancer cells (MCF7, MDA-MB-231). Chondramide inhibits cellular actin filament dynamics shown by a fluorescence-based analysis (fluorescence recovery after photobleaching (FRAP)) and leads to apoptosis characterized by phosphatidylserine exposure, release of cytochrome C from mitochondria and finally activation of caspases. Chondramide enhances the occurrence of mitochondrial permeability transition (MPT) by affecting known MPT modulators: Hexokinase II bound to the voltage-dependent anion channel (VDAC) translocated from the outer mitochondrial membrane to the cytosol and the proapoptotic protein Bad were recruited to the mitochondria. Importantly, protein kinase C-ɛ (PKCɛ), a prosurvival kinase possessing an actin-binding site and known to regulate the hexokinase/VDAC interaction as well as Bad phosphorylation was identified as the link between actin CSK and apoptosis induction. PKCɛ, which was found overexpressed in breast cancer cells, accumulated in actin bundles induced by Chondramide and lost its activity. Our second goal was to characterize the potential tumor-specific action of actin-binding agents. As the nontumor breast epithelial cell line MCF-10A in fact shows resistance to Chondramide-induced apoptosis and notably express low level of PKCɛ, we suggest that trapping PKCɛ via Chondramide-induced actin hyperpolymerization displays tumor cell specificity. Our work provides a link between targeting the ubiquitously occurring actin CSK and selective inhibition of pro-tumorigenic PKCɛ, thus setting the stage for actin-stabilizing agents as

  10. Mechanics of composite actin networks: in vitro and cellular perspectives

    NASA Astrophysics Data System (ADS)

    Upadhyaya, Arpita

    2014-03-01

    Actin filaments and associated actin binding proteins play an essential role in governing the mechanical properties of eukaryotic cells. Even though cells have multiple actin binding proteins (ABPs) that exist simultaneously to maintain the structural and mechanical integrity of the cellular cytoskeleton, how these proteins work together to determine the properties of actin networks is not well understood. The ABP, palladin, is essential for the integrity of cell morphology and movement during development. Palladin coexists with alpha-actinin in stress fibers and focal adhesions and binds to both actin and alpha-actinin. To obtain insight into how mutually interacting actin crosslinking proteins modulate the properties of actin networks, we have characterized the micro-structure and mechanics of actin networks crosslinked with palladin and alpha-actinin. Our studies on composite networks of alpha-actinin/palladin/actin show that palladin and alpha-actinin synergistically determine network viscoelasticity. We have further examined the role of palladin in cellular force generation and mechanosensing. Traction force microscopy revealed that TAFs are sensitive to substrate stiffness as they generate larger forces on substrates of increased stiffness. Contrary to expectations, knocking down palladin increased the forces generated by cells, and also inhibited the ability to sense substrate stiffness for very stiff gels. This was accompanied by significant differences in the actin organization and adhesion dynamics of palladin knock down cells. Perturbation experiments also suggest altered myosin activity in palladin KD cells. Our results suggest that the actin crosslinkers such as palladin and myosin motors coordinate for optimal cell function and to prevent aberrant behavior as in cancer metastasis.

  11. TaADF4, an actin-depolymerizing factor from wheat, is required for resistance to the stripe rust pathogen Puccinia striiformis f. sp. tritici.

    PubMed

    Zhang, Bing; Hua, Yuan; Wang, Juan; Huo, Yan; Shimono, Masaki; Day, Brad; Ma, Qing

    2017-03-01

    Actin filament assembly in plants is a dynamic process, requiring the activity of more than 75 actin-binding proteins. Central to the regulation of filament assembly and stability is the activity of a conserved family of actin-depolymerizing factors (ADFs), whose primarily function is to regulate the severing and depolymerization of actin filaments. In recent years, the activity of ADF proteins has been linked to a variety of cellular processes, including those associated with response to stress. Herein, a wheat ADF gene, TaADF4, was identified and characterized. TaADF4 encodes a 139-amino-acid protein containing five F-actin-binding sites and two G-actin-binding sites, and interacts with wheat (Triticum aestivum) Actin1 (TaACT1), in planta. Following treatment of wheat, separately, with jasmonic acid, abscisic acid or with the avirulent race, CYR23, of the stripe rust pathogen Puccinia striiformis f. sp. tritici, we observed a rapid induction in accumulation of TaADF4 mRNA. Interestingly, accumulation of TaADF4 mRNA was diminished in response to inoculation with a virulent race, CYR31. Silencing of TaADF4 resulted in enhanced susceptibility to CYR23, demonstrating a role for TaADF4 in defense signaling. Using a pharmacological-based approach, coupled with an analysis of host response to pathogen infection, we observed that treatment of plants with the actin-modifying agent latrunculin B enhanced resistance to CYR23, including increased production of reactive oxygen species and enhancement of localized hypersensitive cell death. Taken together, these data support the hypothesis that TaADF4 positively modulates plant immunity in wheat via the modulation of actin cytoskeletal organization.

  12. TaADF3, an Actin-Depolymerizing Factor, Negatively Modulates Wheat Resistance Against Puccinia striiformis

    PubMed Central

    Tang, Chunlei; Deng, Lin; Chang, Dan; Chen, Shuntao; Wang, Xiaojie; Kang, Zhensheng

    2016-01-01

    The actin cytoskeleton has been implicated in plant defense against pathogenic fungi, oomycetes, and bacteria. Actin depolymerizing factors (ADFs) are stimulus responsive actin cytoskeleton modulators. However, there is limited evidence linking ADFs with plant defense against pathogens. In this study, we have isolated and functionally characterized a stress-responsive ADF gene (TaADF3) from wheat, which was detectable in all examined wheat tissues. TaADF3 is a three-copy gene located on chromosomes 5AL, 5BL, and 5DL. A particle bombardment assay in onion epidermal cells revealed the cytoplasmic and nuclear localization of TaADF3. The expression of TaADF3 was inducible by abscisic acid (ABA), as well as various abiotic stresses (drought and cold) and virulent Puccinia striiformis f. sp. tritici (Pst) but was down regulated in response to avirulent Pst. Virus-induced silencing of TaADF3 copies enhanced wheat resistance to avirulent Pst, with decreased reactive oxygen species (ROS) accumulation and hypersensitive response (HR). Upon treatment with virulent Pst, TaADF3-knockdown plants exhibited reduced susceptibility, which was accompanied by increased ROS production and HR. Interestingly, the silencing of TaADF3 resulted in hindered pathogen penetration and haustoria formation for both avirulent and virulent Pst. Moreover, the array and distribution of actin filaments was transformed in TaADF3-knockdown epidermal cells, which possibly facilitated attenuating the fungus penetration. Thus, our findings suggest that TaADF3 positively regulates wheat tolerance to abiotic stresses and negatively regulates wheat resistance to Pst in an ROS-dependent manner, possibly underlying the mechanism of impeding fungal penetration dependent on the actin architecture dynamics. PMID:26834758

  13. Importance of Interaction between Integrin and Actin Cytoskeleton in Suspension Adaptation of CHO cells.

    PubMed

    Walther, Christa G; Whitfield, Robert; James, David C

    2016-04-01

    The biopharmaceutical production process relies upon mammalian cell technology where single cells proliferate in suspension in a chemically defined synthetic environment. This environment lacks exogenous growth factors, usually contributing to proliferation of fibroblastic cell types such as Chinese hamster ovary (CHO) cells. Use of CHO cells for production hence requires a lengthy 'adaptation' process to select clones capable of proliferation as single cells in suspension. The underlying molecular changes permitting proliferation in suspension are not known. Comparison of the non-suspension-adapted clone CHO-AD and a suspension-adapted propriety cell line CHO-SA by flow cytometric analysis revealed a highly variable bi-modal expression pattern for cell-to-cell contact proteins in contrast to the expression pattern seen for integrins. Those have a uni-modal expression on suspension and adherent cells. Integrins showed a conformation distinguished by regularly distributed clusters forming a sphere on the cell membrane of suspension-adapted cells. Actin cytoskeleton analysis revealed reorganisation from the typical fibrillar morphology found in adherent cells to an enforced spherical subcortical actin sheath in suspension cells. The uni-modal expression and specific clustering of integrins could be confirmed for CHO-S, another suspension cell line. Cytochalasin D treatment resulted in breakdown of the actin sheath and the sphere-like integrin conformation demonstrating the link between integrins and actin in suspension-adapted CHO cells. The data demonstrates the importance of signalling changes, leading to an integrin rearrangement on the cell surface, and the necessity of the reinforcement of the actin cytoskeleton for proliferation in suspension conditions.

  14. Regulation of myosin II activity by actin architecture

    NASA Astrophysics Data System (ADS)

    Weirich, Kimberly; Stam, Samantha; McCall, Patrick; Munro, Edwin; Gardel, Margaret

    2015-03-01

    Networks of actin filaments containing myosin II motors generate forces and motions that promote biological processes such as cell division, motility, and cargo transport. In cells, actin filaments are arranged in various structures from disordered meshworks to tight bundles. Clusters of myosin II motors, known as myosin filaments, crosslink and generate force on neighboring actin filaments. We hypothesized that the local actin architecture controls the magnitude and duration of force generated by myosin II motors. We used fluorescence imaging to directly measure the mobility of myosin II filaments on actin networks and bundles with varying actin filament polarity, orientation, spacing, and length. On unipolar bundles, myosin exhibits fast, unidirectional motion consistent with their unloaded gliding speed. On mixed polarity bundles, myosin speed is reduced by one order of magnitude and marked by direction switching and trapping. Increasing filament spacing and bundle flexibility reduces the duration of trapping and enhances the mobility of motors. Simulations indicate that stable trapping is a signature of large generated forces while increased mobility indicates force release. Our data underscore that the efficiency of force generation by myosin motors in an actin network depends sensitively on its architecture and suggests actin crosslinking proteins are tuned to optimize actomyosin contractility.

  15. Actin-Based Motility of Intracellular Microbial Pathogens

    PubMed Central

    Goldberg, Marcia B.

    2001-01-01

    A diverse group of intracellular microorganisms, including Listeria monocytogenes, Shigella spp., Rickettsia spp., and vaccinia virus, utilize actin-based motility to move within and spread between mammalian host cells. These organisms have in common a pathogenic life cycle that involves a stage within the cytoplasm of mammalian host cells. Within the cytoplasm of host cells, these organisms activate components of the cellular actin assembly machinery to induce the formation of actin tails on the microbial surface. The assembly of these actin tails provides force that propels the organisms through the cell cytoplasm to the cell periphery or into adjacent cells. Each of these organisms utilizes preexisting mammalian pathways of actin</