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1

P70 S6 kinase mediates tau phosphorylation and synthesis.  

PubMed

Currently, we found that the 70-kDa p70 S6 kinase (p70S6K) directly phosphorylates tau at S262, S214, and T212 sites in vitro. By immunoprecipitation, p-p70S6K (T421/S424) showed a close association with p-tau (S262 and S396/404). Zinc-induced p70S6K activation could only upregulate translation of total S6 and tau but not global proteins in SH-SY5Y cells. The requirement of p70S6K activation was confirmed in the SH-SY5Y cells that overexpress wild-type htau40. Level of p-p70S6K (T421/S424) was only significantly correlated with p-tau at S262, S214, and T212, but not T212/S214, in Alzheimer's disease (AD) brains. These suggested that p70S6K might contribute to tau related pathologies in AD brains. PMID:16364302

Pei, Jin-Jing; An, Wen-Lin; Zhou, Xin-Wen; Nishimura, Takeshi; Norberg, Jan; Benedikz, Eirikur; Götz, Jürgen; Winblad, Bengt

2006-01-01

2

Structural Basis of Human p70 Ribosomal S6 Kinase-1 Regulation by Activation Loop Phosphorylation  

PubMed Central

p70 ribosomal S6 kinase (p70S6K) is a downstream effector of the mTOR signaling pathway involved in cell proliferation, cell growth, cell-cycle progression, and glucose homeostasis. Multiple phosphorylation events within the catalytic, autoinhibitory, and hydrophobic motif domains contribute to the regulation of p70S6K. We report the crystal structures of the kinase domain of p70S6K1 bound to staurosporine in both the unphosphorylated state and in the 3?-phosphoinositide-dependent kinase-1-phosphorylated state in which Thr-252 of the activation loop is phosphorylated. Unphosphorylated p70S6K1 exists in two crystal forms, one in which the p70S6K1 kinase domain exists as a monomer and the other as a domain-swapped dimer. The crystal structure of the partially activated kinase domain that is phosphorylated within the activation loop reveals conformational ordering of the activation loop that is consistent with a role in activation. The structures offer insights into the structural basis of the 3?-phosphoinositide-dependent kinase-1-induced activation of p70S6K and provide a platform for the rational structure-guided design of specific p70S6K inhibitors. PMID:19864428

Sunami, Tomoko; Byrne, Noel; Diehl, Ronald E.; Funabashi, Kaoru; Hall, Dawn L.; Ikuta, Mari; Patel, Sangita B.; Shipman, Jennifer M.; Smith, Robert F.; Takahashi, Ikuko; Zugay-Murphy, Joan; Iwasawa, Yoshikazu; Lumb, Kevin J.; Munshi, Sanjeev K.; Sharma, Sujata

2010-01-01

3

Structural Basis of Human p70 Ribosomal S6 Kinase-1 Regulation by Activation Loop Phosphorylation  

SciTech Connect

p70 ribosomal S6 kinase (p70S6K) is a downstream effector of the mTOR signaling pathway involved in cell proliferation, cell growth, cell-cycle progression, and glucose homeostasis. Multiple phosphorylation events within the catalytic, autoinhibitory, and hydrophobic motif domains contribute to the regulation of p70S6K. We report the crystal structures of the kinase domain of p70S6K1 bound to staurosporine in both the unphosphorylated state and in the 3{prime}-phosphoinositide-dependent kinase-1-phosphorylated state in which Thr-252 of the activation loop is phosphorylated. Unphosphorylated p70S6K1 exists in two crystal forms, one in which the p70S6K1 kinase domain exists as a monomer and the other as a domain-swapped dimer. The crystal structure of the partially activated kinase domain that is phosphorylated within the activation loop reveals conformational ordering of the activation loop that is consistent with a role in activation. The structures offer insights into the structural basis of the 3{prime}-phosphoinositide-dependent kinase-1-induced activation of p70S6K and provide a platform for the rational structure-guided design of specific p70S6K inhibitors.

Sunami, Tomoko; Byrne, Noel; Diehl, Ronald E.; Funabashi, Kaoru; Hall, Dawn L.; Ikuta, Mari; Patel, Sangita B.; Shipman, Jennifer M.; Smith, Robert F.; Takahashi, Ikuko; Zugay-Murphy, Joan; Iwasawa, Yoshikazu; Lumb, Kevin J.; Munshi, Sanjeev K.; Sharma, Sujata (Banyu); (Merck)

2010-03-04

4

Vascular tumors have increased p70 S6-kinase activation and are inhibited by topical rapamycin.  

PubMed

Vascular tumors are endothelial cell neoplasms whose cellular and molecular mechanisms, leading to tumor formation, are poorly understood, and current therapies have limited efficacy with significant side effects. We have investigated mechanistic (mammalian) target of rapamycin (mTOR) signaling in benign and malignant vascular tumors, and the effects of mTOR kinase inhibitor as a potential therapy for these lesions. Human vascular tumors (infantile hemangioma and angiosarcoma) were analyzed by immunohistochemical stains and western blot for the phosphorylation of p70 S6-kinase (S6K) and S6 ribosomal protein (S6), which are activated downstream of mTOR complex-1 (mTORC1). To assess the function of S6K, tumor cells with genetic knockdown of S6K were analyzed for cell proliferation and migration. The effects of topical rapamycin, an mTOR inhibitor, on mTORC1 and mTOR complex-2 (mTORC2) activities, as well as on tumor growth and migration, were determined. Vascular tumors showed increased activation of S6K and S6. Genetic knockdown of S6K resulted in reduced tumor cell proliferation and migration. Rapamycin fully inhibited mTORC1 and partially inhibited mTORC2 activities, including the phosphorylation of Akt (serine 473) and PKC?, in vascular tumor cells. Rapamycin significantly reduced vascular tumor growth in vitro and in vivo. As a potential localized therapy for cutaneous vascular tumors, topically applied rapamycin effectively reduced tumor growth with limited systemic drug absorption. These findings reveal the importance of mTOR signaling pathways in benign and malignant vascular tumors. The mTOR pathway is an important therapeutic target in vascular tumors, and topical mTOR inhibitors may provide an alternative and well-tolerated therapy for the treatment of cutaneous vascular lesions. PMID:23938603

Du, Wa; Gerald, Damien; Perruzzi, Carole A; Rodriguez-Waitkus, Paul; Enayati, Ladan; Krishnan, Bhuvaneswari; Edmonds, Joseph; Hochman, Marcelo L; Lev, Dina C; Phung, Thuy L

2013-10-01

5

Resistance exercise-induced increase in muscle mass correlates with p70S6 kinase phosphorylation in human subjects.  

PubMed

The purpose of the present study was to investigate the possible relationship between a change in Thr(389) phosphorylation of p70S6 kinase (p70(S6k)) after a single resistance training session and an increase in skeletal muscle mass following short-term resistance training. Eight male subjects performed an initial resistance training session in leg press, six sets of 6RM with 2 min between sets. Muscle biopsies were obtained from the vastus lateralis before (T1) and 30 min after the initial training session (T2). Six of these subjects completed a 14-week resistance-training programme, three times per week (nine exercises, six sets, 6RM). A third muscle biopsy was obtained at the end of the 14-week training period (T3). One repetition maximum (1RM) squat, bench press and leg press strength as well as fat-free mass (FFM, with dual energy X-ray absorptiometry) were determined at T1 and T3. The results show that the increase in Thr(389) phosphorylation of p70(S6k) after the initial training session was closely correlated with the percentage increase in whole body FFM (r = 0.89, P < 0.01), FFM(leg) (r = 0.81, P < 0.05), 1RM squat (r = 0.84, P < 0.05), and type IIA muscle fibre cross sectional area (r = 0.82, P < 0.05) after 14 weeks of resistance training. These results may suggest that p70(S6k) phosphorylation is involved in the signalling events leading to an increase in protein accretion in human skeletal muscle following resistance training, at least during the initial training period. PMID:17874120

Terzis, Gerasimos; Georgiadis, Giorgos; Stratakos, Grigoris; Vogiatzis, Ioannis; Kavouras, Stavros; Manta, Panagiota; Mascher, Henrik; Blomstrand, Eva

2008-01-01

6

Inhibition of p70 S6 kinase (S6K1) activity by A77 1726 and its effect on cell proliferation and cell cycle progress.  

PubMed

Leflunomide is a novel immunomodulatory drug prescribed for treating rheumatoid arthritis. It inhibits the activity of protein tyrosine kinases and dihydroorotate dehydrogenase, a rate-limiting enzyme in the pyrimidine nucleotide synthesis pathway. Here, we report that A77 1726, the active metabolite of leflunomide, inhibited the phosphorylation of ribosomal protein S6 and two other substrates of S6K1, insulin receptor substrate-1 and carbamoyl phosphate synthetase 2, in an A375 melanoma cell line. A77 1726 increased the phosphorylation of AKT, p70 S6 (S6K1), ERK1/2, and MEK through the feedback activation of the IGF-1 receptor-mediated signaling pathway. In vitro kinase assay revealed that leflunomide and A77 1726 inhibited S6K1 activity with IC50 values of approximately 55 and 80 ?M, respectively. Exogenous uridine partially blocked A77 1726-induced inhibition of A375 cell proliferation. S6K1 knockdown led to the inhibition of A375 cell proliferation but did not potentiate the antiproliferative effect of A77 1726. A77 1726 stimulated bromodeoxyuridine incorporation in A375 cells but arrested the cell cycle in the S phase, which was reversed by addition of exogenous uridine or by MAP kinase pathway inhibitors but not by rapamycin and LY294002 (a phosphoinositide 3-kinase inhibitor). These observations suggest that A77 1726 accelerates cell cycle entry into the S phase through MAP kinase activation and that pyrimidine nucleotide depletion halts the completion of the cell cycle. Our study identified a novel molecular target of A77 1726 and showed that the inhibition of S6K1 activity was in part responsible for its antiproliferative activity. Our study also provides a novel mechanistic insight into A77 1726-induced cell cycle arrest in the S phase. PMID:25379019

Doscas, Michelle E; Williamson, Ashley J; Usha, Lydia; Bogachkov, Yedida; Rao, Geetha S; Xiao, Fei; Wang, Yimin; Ruby, Carl; Kaufman, Howard; Zhou, Jingsong; Williams, James W; Li, Yi; Xu, Xiulong

2014-10-01

7

Inhibition of p70 S6 Kinase (S6K1) Activity by A77 1726 and Its Effect on Cell Proliferation and Cell Cycle Progress12  

PubMed Central

Leflunomide is a novel immunomodulatory drug prescribed for treating rheumatoid arthritis. It inhibits the activity of protein tyrosine kinases and dihydroorotate dehydrogenase, a rate-limiting enzyme in the pyrimidine nucleotide synthesis pathway. Here, we report that A77 1726, the active metabolite of leflunomide, inhibited the phosphorylation of ribosomal protein S6 and two other substrates of S6K1, insulin receptor substrate-1 and carbamoyl phosphate synthetase 2, in an A375 melanoma cell line. A77 1726 increased the phosphorylation of AKT, p70 S6 (S6K1), ERK1/2, and MEK through the feedback activation of the IGF-1 receptor–mediated signaling pathway. Invitro kinase assay revealed that leflunomide and A77 1726 inhibited S6K1 activity with IC50 values of approximately 55 and 80 ?M, respectively. Exogenous uridine partially blocked A77 1726–induced inhibition of A375 cell proliferation. S6K1 knockdown led to the inhibition of A375 cell proliferation but did not potentiate the antiproliferative effect of A77 1726. A77 1726 stimulated bromodeoxyuridine incorporation in A375 cells but arrested the cell cycle in the S phase, which was reversed by addition of exogenous uridine or by MAP kinase pathway inhibitors but not by rapamycin and LY294002 (a phosphoinositide 3-kinase inhibitor). These observations suggest that A77 1726 accelerates cell cycle entry into the S phase through MAP kinase activation and that pyrimidine nucleotide depletion halts the completion of the cell cycle. Our study identified a novel molecular target of A77 1726 and showed that the inhibition of S6K1 activity was in part responsible for its antiproliferative activity. Our study also provides a novel mechanistic insight into A77 1726–induced cell cycle arrest in the S phase. PMID:25379019

Doscas, Michelle E.; Williamson, Ashley J.; Usha, Lydia; Bogachkov, Yedida; Rao, Geetha S.; Xiao, Fei; Wang, Yimin; Ruby, Carl; Kaufman, Howard; Zhou, Jingsong; Williams, James W.; Li, Yi; Xu, Xiulong

2014-01-01

8

Absence of ?-sarcoglycan alters the response of p70S6 kinase to mechanical perturbation in murine skeletal muscle  

PubMed Central

Background The dystrophin glycoprotein complex (DGC) is located at the sarcolemma of muscle fibers, providing structural integrity. Mutations in and loss of DGC proteins cause a spectrum of muscular dystrophies. When only the sarcoglycan subcomplex is absent, muscles display severe myofiber degeneration, but little susceptibility to contractile damage, suggesting that disease occurs not by structural deficits but through aberrant signaling, namely, loss of normal mechanotransduction signaling through the sarcoglycan complex. We extended our previous studies on mechanosensitive, ?-sarcoglycan-dependent ERK1/2 phosphorylation, to determine whether additional pathways are altered with the loss of ?-sarcoglycan. Methods We examined mechanotransduction in the presence and absence of ?-sarcoglycan, using C2C12 myotubes, and primary cultures and isolated muscles from C57Bl/6 (C57) and ?-sarcoglycan-null (?-SG-/-) mice. All were subjected to cyclic passive stretch. Signaling protein phosphorylation was determined by immunoblotting of lysates from stretched and non-stretched samples. Calcium dependence was assessed by maintaining muscles in calcium-free or tetracaine-supplemented Ringer’s solution. Dependence on mTOR was determined by stretching isolated muscles in the presence or absence of rapamycin. Results C2C12 myotube stretch caused a robust increase in P-p70S6K, but decreased P-FAK and P-ERK2. Neither Akt nor ERK1 were responsive to passive stretch. Similar but non-significant trends were observed in C57 primary cultures in response to stretch, and ?-SG-/- cultures displayed no p70S6K response. In contrast, in isolated muscles, p70S6K was mechanically responsive. Basal p70S6K activation was elevated in muscles of ?-SG-/- mice, in a calcium-independent manner. p70S6K activation increased with stretch in both C57 and ?-SG-/- isolated muscles, and was sustained in ?-SG-/- muscles, unlike the transient response in C57 muscles. Rapamycin treatment blocked all of p70S6K activation in stretched C57 muscles, and reduced downstream S6RP phosphorylation. However, even though rapamycin treatment decreased p70S6K activation in stretched ?-SG-/- muscles, S6RP phosphorylation remained elevated. Conclusions p70S6K is an important component of ?-sarcoglycan-dependent mechanotransduction in skeletal muscle. Our results suggest that loss of ?-sarcoglycan uncouples the response of p70S6K to stretch and implies that ?-sarcoglycan is important for inactivation of this pathway. Overall, we assert that altered load-sensing mechanisms exist in muscular dystrophies where the sarcoglycans are absent. PMID:25024843

2014-01-01

9

P70S6K 1 regulation of angiogenesis through VEGF and HIF-1{alpha} expression  

SciTech Connect

Research highlights: {yields} P70S6K1 regulates VEGF expression; {yields} P70S6K1 induces transcriptional activation through HIF-1{alpha} binding site; {yields} P70S6K1 regulates HIF-1{alpha}, but not HIF-1{beta} protein expression; {yields} P70S6K1 mediates tumor growth and angiogenesis through HIF-1{alpha} and VEGF expression. -- Abstract: The 70 kDa ribosomal S6 kinase 1 (p70S6K1), a downstream target of phosphoinositide 3-kinase (PI3K) and ERK mitogen-activated protein kinase (MAPK), is an important regulator of cell cycle progression, and cell proliferation. Recent studies indicated an important role of p70S6K1 in PTEN-negative and AKT-overexpressing tumors. However, the mechanism of p70S6K1 in tumor angiogenesis remains to be elucidated. In this study, we specifically inhibited p70S6K1 activity in ovarian cancer cells using vector-based small interfering RNA (siRNA) against p70S6K1. We found that knockdown of p70S6K1 significantly decreased VEGF protein expression and VEGF transcriptional activation through the HIF-1{alpha} binding site at its enhancer region. The expression of p70S6K1 siRNA specifically inhibited HIF-1{alpha}, but not HIF-1{beta} protein expression. We also found that p70S6K1 down-regulation inhibited ovarian tumor growth and angiogenesis, and decreased cell proliferation and levels of VEGF and HIF-1{alpha} expression in tumor tissues. Our results suggest that p70S6K1 is required for tumor growth and angiogenesis through HIF-1{alpha} and VEGF expression, providing a molecular mechanism of human ovarian cancer mediated by p70S6K1 signaling.

Bian, Chuan-Xiu; Shi, Zhumei [Department of Pathology, Cancer Center, Nanjing Medical University, Nanjing 210029 (China)] [Department of Pathology, Cancer Center, Nanjing Medical University, Nanjing 210029 (China); Meng, Qiao; Jiang, Yue; Liu, Ling-Zhi [Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107 (United States)] [Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107 (United States); Jiang, Bing-Hua, E-mail: binghjiang@yahoo.com [Department of Pathology, Cancer Center, Nanjing Medical University, Nanjing 210029 (China) [Department of Pathology, Cancer Center, Nanjing Medical University, Nanjing 210029 (China); Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107 (United States)

2010-07-30

10

PF-4708671 Activates AMPK Independently of p70S6K1 Inhibition  

PubMed Central

The P70 ribosomal protein S6 kinase 1 (P70S6K1) is activated by the mammalian target of rapamycin (mTORC1) and regulates proliferation, growth, and metabolism. PF-4708671 is a novel, cell-permeable, has been proposed to be a highly specific inhibitor of p70S6K1. It is used in micromolar concentration range to dissect signaling pathways downstream of mTORC1 and to study the function of p70S6K1. Here we show that PF-4708671 induces AMP-activated protein kinase (AMPK) phosphorylation and activation in immortalized mouse embryonic fibroblasts (MEF) independently of p70S6K1, due to specific inhibition of mitochondrial respiratory chain Complex I. PMID:25202971

Vainer, Gilad W.; Saada, Ann; Kania-Almog, Juliane; Amartely, Adir; Bar-Tana, Jacob; Hertz, Rachel

2014-01-01

11

A Hexane Fraction of Guava Leaves (Psidium guajava L.) Induces Anticancer Activity by Suppressing AKT/Mammalian Target of Rapamycin/Ribosomal p70 S6 Kinase in Human Prostate Cancer Cells  

PubMed Central

Abstract This study was carried out to evaluate the anticancer effects of guava leaf extracts and its fractions. The chemical compositions of the active extracts were also determined. In the present study, we set out to determine whether the anticancer effects of guava leaves are linked with their ability to suppress constitutive AKT/mammalian target of rapamycin (mTOR)/ribosomal p70 S6 kinase (S6K1) and mitogen-activated protein kinase (MAPK) activation pathways in human prostate cancer cells. We found that guava leaf hexane fraction (GHF) was the most potent inducer of cytotoxic and apoptotic effects in PC-3 cells. The molecular mechanism or mechanisms of GHF apoptotic potential were correlated with the suppression of AKT/mTOR/S6K1 and MAPK signaling pathways. This effect of GHF correlated with down-regulation of various proteins that mediate cell proliferation, cell survival, metastasis, and angiogenesis. Analysis of GHF by gas chromatography and gas chromatography–mass spectrometry tentatively identified 60 compounds, including ?-eudesmol (11.98%), ?-copaene (7.97%), phytol (7.95%), ?-patchoulene (3.76%), ?-caryophyllene oxide (CPO) (3.63%), caryophylla-3(15),7(14)-dien-6-ol (2.68%), (E)-methyl isoeugenol (1.90%), ?-terpineol (1.76%), and octadecane (1.23%). Besides GHF, CPO, but not phytol, also inhibited the AKT/mTOR/S6K1 signaling pathway and induced apoptosis in prostate cancer cells. Overall, these findings suggest that guava leaves can interfere with multiple signaling cascades linked with tumorigenesis and provide a source of potential therapeutic compounds for both the prevention and treatment of cancer. PMID:22280146

Ryu, Nae Hyung; Park, Kyung-Ran; Kim, Sung-Moo; Yun, Hyung-Mun; Nam, Dongwoo; Lee, Seok-Geun; Jang, Hyeung-Jin; Ahn, Kyoo Seok; Kim, Sung-Hoon; Shim, Bum Sang; Choi, Seung-Hoon; Mosaddik, Ashik

2012-01-01

12

A hexane fraction of guava Leaves (Psidium guajava L.) induces anticancer activity by suppressing AKT/mammalian target of rapamycin/ribosomal p70 S6 kinase in human prostate cancer cells.  

PubMed

This study was carried out to evaluate the anticancer effects of guava leaf extracts and its fractions. The chemical compositions of the active extracts were also determined. In the present study, we set out to determine whether the anticancer effects of guava leaves are linked with their ability to suppress constitutive AKT/mammalian target of rapamycin (mTOR)/ribosomal p70 S6 kinase (S6K1) and mitogen-activated protein kinase (MAPK) activation pathways in human prostate cancer cells. We found that guava leaf hexane fraction (GHF) was the most potent inducer of cytotoxic and apoptotic effects in PC-3 cells. The molecular mechanism or mechanisms of GHF apoptotic potential were correlated with the suppression of AKT/mTOR/S6K1 and MAPK signaling pathways. This effect of GHF correlated with down-regulation of various proteins that mediate cell proliferation, cell survival, metastasis, and angiogenesis. Analysis of GHF by gas chromatography and gas chromatography-mass spectrometry tentatively identified 60 compounds, including ?-eudesmol (11.98%), ?-copaene (7.97%), phytol (7.95%), ?-patchoulene (3.76%), ?-caryophyllene oxide (CPO) (3.63%), caryophylla-3(15),7(14)-dien-6-ol (2.68%), (E)-methyl isoeugenol (1.90%), ?-terpineol (1.76%), and octadecane (1.23%). Besides GHF, CPO, but not phytol, also inhibited the AKT/mTOR/S6K1 signaling pathway and induced apoptosis in prostate cancer cells. Overall, these findings suggest that guava leaves can interfere with multiple signaling cascades linked with tumorigenesis and provide a source of potential therapeutic compounds for both the prevention and treatment of cancer. PMID:22280146

Ryu, Nae Hyung; Park, Kyung-Ran; Kim, Sung-Moo; Yun, Hyung-Mun; Nam, Dongwoo; Lee, Seok-Geun; Jang, Hyeung-Jin; Ahn, Kyoo Seok; Kim, Sung-Hoon; Shim, Bum Sang; Choi, Seung-Hoon; Mosaddik, Ashik; Cho, Somi K; Ahn, Kwang Seok

2012-03-01

13

Mechanistic target of rapamycin (mTOR) signaling genes in decapod crustaceans: cloning and tissue expression of mTOR, Akt, Rheb, and p70 S6 kinase in the green crab, Carcinus maenas, and blackback land crab, Gecarcinus lateralis.  

PubMed

Mechanistic target of rapamycin (mTOR) controls global translation of mRNA into protein by phosphorylating p70 S6 kinase (S6K) and eIF4E-binding protein-1. Akt and Rheb, a GTP-binding protein, regulate mTOR protein kinase activity. Molting in crustaceans is regulated by ecdysteroids synthesized by a pair of molting glands, or Y-organs (YOs), located in the cephalothorax. During premolt, the YOs hypertrophy and increase production of ecdysteroids. Rapamycin (1?M) inhibited ecdysteroid secretion in Carcinus maenas and Gecarcinus lateralis YOs in vitro, indicating that ecdysteroidogenesis requires mTOR-dependent protein synthesis. The effects of molting on the expression of four key mTOR signaling genes (mTOR, Akt, Rheb, and S6K) in the YO was investigated. Partial cDNAs encoding green crab (C. maenas) mTOR (4031bp), Akt (855bp), and S6K (918bp) were obtained from expressed sequence tags. Identity/similarity of the deduced amino acid sequence of the C. maenas cDNAs to human orthologs were 72%/81% for Cm-mTOR, 58%/73% for Cm-Akt, and 77%/88% for Cm-S6K. mTOR, Akt, S6K, and elongation factor 2 (EF2) in C. maenas and blackback land crab (G. lateralis) were expressed in all tissues examined. The two species differed in the effects of molting on gene expression in the YO. In G. lateralis, Gl-mTOR, Gl-Akt, and Gl-EF2 mRNA levels were increased during premolt. By contrast, molting had no effect on the expression of Cm-mTOR, Cm-Akt, Cm-S6K, Cm-Rheb, and Cm-EF2. These data suggest that YO activation during premolt involves up regulation of mTOR signaling genes in G. lateralis, but is not required in C. maenas. PMID:24269559

Abuhagr, Ali M; Maclea, Kyle S; Chang, Ernest S; Mykles, Donald L

2014-02-01

14

SHORT REPORT Cloning and characterization of a nuclear S6 kinase, S6 kinase-related  

E-print Network

to p70S6K activation involves the FKBP12-rapamycin-associated protein (FRAP, also known as mTOR, RAFT, and RAPT) and was demonstrated using the immunosuppressant rapamy- cin (Chung et al., 1992). How FRAP aects the possibility that FRAP can regulate the p70S6K signaling pathway by its protein kinase activities

15

Activation of p70s6k is Associated with Phosphorylation of Four Clustered Sites Displaying Ser\\/Thr-Pro Motifs  

Microsoft Academic Search

Partial amino acid sequences were obtained from 22 internal tryptic peptides of rat liver p70s6k (M_r 70,000 ribosomal protein S6 kinase), 3 of which were found to contain phosphorylated residues. To determine whether these sites were associated with p70s6k activation, the kinase was labeled to high specific activity with 32P_i in Swiss mouse 3T3 cells. By sequential cleavage with CNBr

Stefano Ferrari; Willi Bannwarth; Simon J. Morley; Nicholas F. Totty; George Thomas

1992-01-01

16

Mechanical stimuli of skeletal muscle: implications on mTOR\\/p70s6k and protein synthesis  

Microsoft Academic Search

The skeletal muscle is a tissue with adaptive properties which are essential to the survival of many species. When mechanically\\u000a stimulated it is liable to undergo remodeling, namely, changes in its mass\\/volume resulting mainly from myofibrillar protein\\u000a accumulation. The mTOR pathway (mammalian target of rapamycin) via its effector p70s6k (ribosomal protein kinase S6) has been\\u000a reported to be of importance

Nelo Eidy Zanchi; Antonio Herbert Lancha

2008-01-01

17

Phosphorylation and degradation of S6K1 (p70S6K1) in response to persistent JNK1 Activation.  

PubMed

S6K (ribosomal S6 kinase p70, p70S6K) activation requires phosphorylation at two stages. The first phosphorylation is independent of insulin stimulation and mediated by an unknown kinase. The second phosphorylation is mediated by mTOR in insulin dependent manner. In this study, we identified JNK1 (c-Jun N-terminal kinase 1) as a kinase in the first phosphorylation. S6K protein was phosphorylated by JNK1 at S411 and S424 in the carboxyl terminal autoinhibitory domain. The phosphorylation was observed in kinase assay with purified S6K as a substrate, and in cells after JNK1 activation by TNF-? or MEKK1 expression. The phosphorylation was detected in JNK2 null cells, but not in JNK1 null cells after TNF-? treatment. When JNK1 activation was inhibited by MKK7 knockdown, the phosphorylation was blocked in cells. The phosphorylation led to S6K protein degradation in NF-?B deficient cells. The degradation was blocked by inhibition of proteasome activity with MG132. In wide type cells, the phosphorylation did not promote S6K degradation when IKK2 (IKK?, I?B kinase beta) was activated. Instead, the phosphorylation allowed S6K activation by mTOR, which stabilizes S6K protein. In IKK2 null cells or cells treated by IKK2 inhibitor, the phosphorylation led to S6K degradation. These data suggest that S6K is phosphorylated by JNK1 and the phosphorylation makes S6K protein unstable in the absence of IKK2 activation. This study provides a mechanism for regulation of S6K protein stability. PMID:23816567

Zhang, Jin; Gao, Zhanguo; Ye, Jianping

2013-12-01

18

FRAP-p70s6K Signaling Is Required for Pancreatic Cancer Cell Proliferation  

Microsoft Academic Search

Background. FRAP-p70s6K signaling regulates mitogenic responses to growth factors in eukaryotic cells. Constitutive p70s6K activation occurs in some human malignancies and may contribute to dysregulated cell growth. We examined whether inhibition of this pathway affects mitogen-induced proliferation and cell cycle progression of human pancreatic cancer cells in vitro.Methods. Quiescent BxPC3 and Panc-1 human pancreatic cancer cells treated with or without

Shimul A. Shah; Michael W. Potter; Rocco Ricciardi; Richard A. Perugini; Mark P. Callery

2001-01-01

19

Regulation of Cell Growth and Cyclin D1 Expression by the Constitutively Active FRAP-p70s6K Pathway in Human Pancreatic Cancer Cells1  

Microsoft Academic Search

The FRAP-p70s6K signaling pathway was found to be constitutively phosphorylated\\/active in MiaPaCa-2 and Panc-1 human pancreatic can- cer cells and a pancreatic cancer tissue sample as judged by the retarded electrophoretic mobility of the two major FRAP downstream targets, p70s6K and 4E-BP1. Treatment of cells with rapamycin, a selective FRAP inhibitor, inhibited basal p70s6K kinase activity and induced dephospho- rylation

Martin Grewe; Frank Gansauge; Roland M. Schmid; Guido Adler; Thomas Seufferlein

1999-01-01

20

The Presence of a Constitutively Active Phosphoinositide 3Kinase in Small Cell Lung Cancer Cells Mediates Anchorage-independent Proliferation via a Protein Kinase B and p70s6k-dependentPathway1  

Microsoft Academic Search

Small cell lung cancer (SCLC) is characterized by early and widespread métastases.Anchorage-independent growth is pivotal to the ability of tumor cells to survive and metastasize in vivo and, under I'M vitro condi tions, allows transformed cells to form colonies in semisolid medium. Here, we report that of five SCLC cell lines tested, all exhibited high basal constitutive phosphoinositide 3-kinase (PI

Sarah M. Moore; Robert C. Rintoul; Trevor R. Walker; Edwin R. Chilvers; Christopher Haslett; Tariq Sethi

21

Resistance to Selumetinib (AZD6244) in Colorectal Cancer Cell Lines is Mediated by p70S6K and RPS6 Activation1  

PubMed Central

Selumetinib (AZD6244, ARRY-142886) is a MEK1/2 inhibitor that has gained interest as an anti-tumour agent. We have determined the degree of sensitivity/resistance to Selumetinib in a panel of colorectal cancer cell lines using cell proliferation and soft agar assays. Sensitive cell lines underwent G1 arrest, whereas Selumetinib had no effect on the cell cycle of resistant cells. Some of the resistant cell lines showed high levels of ERK1/2 phosphorylation in the absence of serum. Selumetinib inhibited phosphorylation of ERK1/2 and RSK and had no effect on AKT phosphorylation in both sensitive and resistant cells. Furthermore, mutations in KRAS, BRAF, or PIK3CA were not clearly associated with Selumetinib resistance. Surprisingly, Selumetinib was able to inhibit phosphorylation of p70 S6 kinase (p70S6K) and its downstream target ribosomal protein S6 (RPS6) in sensitive cell lines. However, p70S6K and RPS6 phosphorylation remained unaffected or even increased in resistant cells. Moreover, in some of the resistant cell lines p70S6K and RPS6 were phosphorylated in the absence of serum. Interestingly, colorectal primary cultures derived from tumours excised to patients exhibited the same behaviour than established cell lines. Pharmacological inhibition of p70S6K using the PI3K/mTOR inhibitor NVP-BEZ235, the specific mTOR inhibitor Rapamycin and the specific p70S6K inhibitor PF-4708671 potentiated Selumetinib effects in resistant cells. In addition, biological inhibition of p70S6K using siRNA rendered responsiveness to Selumetinib in resistant cell lines. Furthermore, combination of p70S6K silencing and PF-47086714 was even more effective. We can conclude that p70S6K and its downstream target RPS6 are potential biomarkers of resistance to Selumetinib in colorectal cancer. PMID:25379021

Grasso, Silvina; Tristante, Elena; Saceda, Miguel; Carbonell, Pablo; Mayor-López, Leticia; Carballo-Santana, Mar; Carrasco-García, Estefanía; Rocamora-Reverte, Lourdes; García-Morales, Pilar; Carballo, Fernando; Ferragut, José A.; Martínez-Lacaci, Isabel

2014-01-01

22

MEK1/2 overactivation can promote growth arrest by mediating ERK1/2-dependent phosphorylation of p70S6K.  

PubMed

The extracellular signal-regulated kinase (ERK)1/2 mitogen-activated protein (MAP) kinase pathway has been involved in the positive and negative regulation of cell proliferation. Upon mitogen stimulation, ERK1/ERK2 activation is necessary for G1- to S-phase progression whereas when hyperactived, this pathway could elicit cell cycle arrest. The mechanisms involved are not fully elucidated but a kinase-independent function of ERK1/2 has been evidenced in the MAPK-induced growth arrest. Here, we show that p70S6K, a central regulator of protein biosynthesis, is essential for the cell cycle arrest induced by overactivation of ERK1/2. Indeed, whereas MEK1 silencing inhibits cell cycle progression, we demonstrate that active mutant form of MEK1 or MEK2 triggers a G1 phase arrest by stimulating an activation of p70S6K by ERK1/2 kinases. Silencing of ERK1/2 activity by shRNA efficiently suppresses p70S6K phosphorylation on Thr421/Ser424 and S6 phosphorylation on Ser240/244 as well as p21 expression, but these effects can be partially reversed by the expression of kinase-dead mutant form of ERK1 or ERK2. In addition, we demonstrate that the kinase p70S6K modulates neither the p21 gene transcription nor the stability of the protein but enhances the translation of the p21 mRNA. In conclusion, our data emphasizes the importance of the translational regulation of p21 by the MEK1/2-ERK1/2-p70S6K pathway to negatively control the cell cycle progression. PMID:24501087

Guégan, Jean-Philippe; Ezan, Frédéric; Gailhouste, Luc; Langouët, Sophie; Baffet, Georges

2014-07-01

23

Phosphorylated p70S6K in noninvasive low-grade urothelial carcinoma of the bladder: correlation with tumor recurrence  

PubMed Central

We investigated whether inhibiting phosphorylated p70S6K (p-p70S6K) suppresses the proliferation and growth of noninvasive low-grade urothelial carcinoma (LG-URCa) in vitro and whether p-p70S6K can serve as a predictive biomarker for the recurrence of noninvasive LG-URCa of the bladder in patients. We constructed a tissue microarray (TMA) for 95 LG-URCa and 35 benign urothelium samples and performed immunohistochemical staining for p-p70S6K and p-4E-BP1. A Cox regression model was used to investigate the predictive factors for recurrence of LG-URCa. We investigated the dose-dependent antiproliferative effect of rapamycin, its antiproliferative effect and the growth-inhibition effect of p70S6K siRNA transfection in RT4 and 253J cell lines. The pT1 staged group (P < 0.05; hazard ratio (HR), 2.415) and the high p-p70S6K staining group (P < 0.05; HR, 2.249) were independent factors for predicting recurrence. Rapamycin inhibited RT4 and 253J cell proliferation in a dose-dependent manner (r = ?0.850, P < 0.001 in RT4 cells; r = ?0.835, P < 0.001 in 253J cells). RT4 and 253J cell proliferation and growth were inhibited by the transfection of p70S6K siRNA and rapamycin, respectively (P < 0.05). Transfection of p70S6K siRNA resulted in inhibitory effects on cell proliferation and growth that were similar to those of rapamycin. Our results suggest that inhibiting p70S6K phosphorylation is important to prevent recurrence and that p70S6K phosphorylation can be used as a molecular biomarker to predict recurrence of certain LG-URCa of the bladder. PMID:24625880

Kim, Soon-Ja; Kim, Jung Hoon; Jung, Hui Seok; Lee, Tae-Jin; Lee, Kyung Mee; Chang, In Ho

2014-01-01

24

Association of sirolimus adverse effects with m-TOR, p70S6K or Raptor polymorphisms in kidney transplant recipients  

E-print Network

transplant recipients Jean-Baptiste Woillard123 * and Nassim Kamar456 *, Annick Rousseau12 , Lionel Rostaing, Department of Nephrology-Dialysis and Multi-Organ Transplantation, Toulouse, France; 5 INSERM U563, IFR is an immunosuppressive drug used in kidney transplantation. m-TOR binds with Raptor and phosphorylates p70S6 kinase

Paris-Sud XI, Université de

25

FOXP1 regulation via the PI3K/Akt/p70S6K signaling pathway in breast cancer cells  

PubMed Central

Loss of Forkhead box P1 (FOXP1) protein expression confers a poor prognosis in sporadic and familial breast cancer patients, and the FOXP1 gene maps to a tumor suppressor locus at chromosome 3p14. Although correlation studies have indicated that FOXP1 has a role in tumor suppression, determination of the regulatory mechanism of FOXP1 is required to establish its function in breast cancer. It has previously been identified that FOXP1 is regulated by estrogen in breast cancer and that treatment with bisphenol A is effective for regulating the transformation of the normal human breast epithelial cell line, MCF-10F. In addition, FOXO-regulated activation of FOXP1 inhibits the apoptosis of MCF-10F cells following tamoxifen and Akt inhibitor VIII administration. The present study indicates that FOXP1 regulation occurs via a PI3K/Akt/p70S6 kinase (p70S6K) signaling pathway. Following treatment with wortmannin, an inhibitor of phosphatidylinositol 3-kinase (PI3K)/Akt, MCF7 and MDA-MB-231 breast cancer cells demonstrated decreased FOXP1 protein expression levels; this result was also observed in the small interfering (si)RNA silencing of Akt. By contrast, overexpression of Akt resulted in increased FOXP1 protein expression levels in the MDA-MB-231 cells compared with the control cell lysates. Furthermore, treatment with rapamycin, a specific inhibitor of the mammalian target of rapamycin/p70S6K cascade, resulted in decreased FOXP1 expression in the MCF7 cells, but not in the MDA-MB-231 cells, which were resistant to rapamycin-induced inhibition. In addition, silencing of p70S6K using siRNA produced a marked decrease in FOXP1 expression. These data indicate that FOXP1 protein expression is regulated by a PI3K/Akt/p70S6K signaling cascade in breast cancer. PMID:25663935

HALACLI, SEVIL OSKAY; DOGAN, AYSE LALE

2015-01-01

26

D-Glucosamine inhibits proliferation of human cancer cells through inhibition of p70S6K  

SciTech Connect

Although D-glucosamine has been reported as an inhibitor of tumor growth both in vivo and in vitro, the mechanism for the anticancer effect of D-glucosamine is still unclear. Since there are several reports suggesting D-glucosamine inhibits protein synthesis, we examined whether D-glucosamine affects p70S6 K activity, an important signaling molecule involved in protein translation. In the present study, we found D-glucosamine inhibited the activity of p70S6K and the proliferation of DU145 prostate cancer cells and MDA-MB-231 breast cancer cells. D-Glucosamine decreased phosphorylation of p70S6K, and its downstream substrates RPS6, and eIF-4B, but not mTOR and 4EBP1 in DU145 cells, suggesting that D-glucosamine induced inhibition of p70S6K is not through the inhibition of mTOR. In addition, D-glucosamine enhanced the growth inhibitory effects of rapamycin, a specific inhibitor of mTOR. These findings suggest that D-glucosamine can inhibit growth of cancer cells through dephosphorylation of p70S6K.

Oh, Hyun-Ji [Chronic Disease Research Center and Institute for Medical Science, School of Medicine, Keimyung University, Daegu 700-712 (Korea, Republic of); Lee, Jason S. [Department of Biological Science, Seoul National University, Seoul 151-742 (Korea, Republic of); Song, Dae-Kyu [Chronic Disease Research Center and Institute for Medical Science, School of Medicine, Keimyung University, Daegu 700-712 (Korea, Republic of); Shin, Dong-Hoon [Chronic Disease Research Center and Institute for Medical Science, School of Medicine, Keimyung University, Daegu 700-712 (Korea, Republic of); Jang, Byeong-Churl [Chronic Disease Research Center and Institute for Medical Science, School of Medicine, Keimyung University, Daegu 700-712 (Korea, Republic of); Suh, Seong-Il [Chronic Disease Research Center and Institute for Medical Science, School of Medicine, Keimyung University, Daegu 700-712 (Korea, Republic of); Park, Jong-Wook [Chronic Disease Research Center and Institute for Medical Science, School of Medicine, Keimyung University, Daegu 700-712 (Korea, Republic of); Suh, Min-Ho [Chronic Disease Research Center and Institute for Medical Science, School of Medicine, Keimyung University, Daegu 700-712 (Korea, Republic of); Baek, Won-Ki [Chronic Disease Research Center and Institute for Medical Science, School of Medicine, Keimyung University, Daegu 700-712 (Korea, Republic of)]. E-mail: wonki@dsmc.or.kr

2007-09-07

27

Lengthening contractions differentially affect p70 s6k phosphorylation compared to isometric contractions in rat skeletal muscle  

Microsoft Academic Search

The purpose of this investigation was to determine if p70s6k phosphorylation is dependent on the mode of resistance exercise (e.g. isometric vs. lengthening). Two groups (n = 5 each) of Female Sprague Dawley rats, ?12 weeks old, were tested. Rats were anesthetized and indwelling electrodes used\\u000a to stimulate the right hind limb muscles via the sciatic nerve. The tibialis anterior (TA) muscle of

Martin Burry; David Hawkins; Espen E. Spangenburg

2007-01-01

28

Arsenite induces cell transformation by reactive oxygen species, AKT, ERK1/2, and p70S6K1  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Chronic exposure to arsenite induces cell proliferation and transformation. Black-Right-Pointing-Pointer Arsenite-induced transformation increases ROS production and downstream signalings. Black-Right-Pointing-Pointer Inhibition of ROS levels via catalase reduces arsenite-induced cell transformation. Black-Right-Pointing-Pointer Interruption of AKT, ERK, or p70S6K1 inhibits arsenite-induced cell transformation. -- Abstract: Arsenic is naturally occurring element that exists in both organic and inorganic formulations. The inorganic form arsenite has a positive association with development of multiple cancer types. There are significant populations throughout the world with high exposure to arsenite via drinking water. Thus, human exposure to arsenic has become a significant public health problem. Recent evidence suggests that reactive oxygen species (ROS) mediate multiple changes to cell behavior after acute arsenic exposure, including activation of proliferative signaling and angiogenesis. However, the role of ROS in mediating cell transformation by chronic arsenic exposure is unknown. We found that cells chronically exposed to sodium arsenite increased proliferation and gained anchorage-independent growth. This cell transformation phenotype required constitutive activation of AKT, ERK1/2, mTOR, and p70S6K1. We also observed these cells constitutively produce ROS, which was required for the constitutive activation of AKT, ERK1/2, mTOR, and p70S6K1. Suppression of ROS levels by forced expression of catalase also reduced cell proliferation and anchorage-independent growth. These results indicate cell transformation induced by chronic arsenic exposure is mediated by increased cellular levels of ROS, which mediates activation of AKT, ERK1/2, and p70S6K1.

Carpenter, Richard L.; Jiang, Yue; Jing, Yi; He, Jun [Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107 (United States)] [Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107 (United States); Rojanasakul, Yon [Department of Basic Pharmaceutical Sciences, West Virginia University, Morgantown, WV 26506 (United States)] [Department of Basic Pharmaceutical Sciences, West Virginia University, Morgantown, WV 26506 (United States); Liu, Ling-Zhi, E-mail: ling-zhi.liu@jefferson.edu [Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107 (United States)] [Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107 (United States); Jiang, Bing-Hua, E-mail: bhjiang@jefferson.edu [Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107 (United States)] [Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107 (United States)

2011-10-28

29

TRAP1-dependent regulation of p70S6K is involved in the attenuation of protein synthesis and cell migration: Relevance in human colorectal tumors.  

PubMed

TNF receptor-associated protein 1 (TRAP1) is an HSP90 chaperone involved in stress protection and apoptosis in mitochondrial and extramitochondrial compartments. Remarkably, aberrant deregulation of TRAP1 function has been observed in several cancer types with potential new opportunities for therapeutic intervention in humans. Although previous studies by our group identified novel roles of TRAP1 in quality control of mitochondria-destined proteins through the attenuation of protein synthesis, molecular mechanisms are still largely unknown. To shed further light on the signaling pathways regulated by TRAP1 in the attenuation of protein synthesis, this study demonstrates that the entire pathway of cap-mediated translation is activated in cells following TRAP1 interference: consistently, expression and consequent phosphorylation of p70S6K and RSK1, two translation activating kinases, are increased upon TRAP1 silencing. Furthermore, we show that these regulatory functions affect the response to translational stress and cell migration in wound healing assays, processes involving both kinases. Notably, the regulatory mechanisms controlled by TRAP1 are conserved in colorectal cancer tissues, since an inverse correlation between TRAP1 and p70S6K expression is found in tumor tissues, thereby supporting the relevant role of TRAP1 translational regulation in vivo. Taken as a whole, these new findings candidate TRAP1 network for new anti-cancer strategies aimed at targeting the translational/quality control machinery of tumor cells. PMID:24962791

Matassa, Danilo Swann; Agliarulo, Ilenia; Amoroso, Maria Rosaria; Maddalena, Francesca; Sepe, Leandra; Ferrari, Maria Carla; Sagar, Vinay; D'Amico, Silvia; Loreni, Fabrizio; Paolella, Giovanni; Landriscina, Matteo; Esposito, Franca

2014-12-01

30

Fisetin inhibits human melanoma cell growth through direct binding to p70S6K and mTOR: findings from 3-D melanoma skin equivalents and computational modeling.  

PubMed

The incidence of melanoma continues to rise. Inspite of treatment advances, the prognosis remains grim once the disease has metastasized, emphasizing the need to explore additional therapeutic strategies. One such approach is through the use of mechanism-based dietary intervention. We previously showed that the flavonoid fisetin inhibits melanoma cell proliferation, in vitro and in vivo. Here, we studied fisetin-mediated regulation of kinases involved in melanoma growth and progression. Time-course analysis in 3-D melanoma constructs that transitioned from radial to vertical growth showed that fisetin treatment resulted in significant decrease in melanocytic lesions in contrast to untreated controls that showed large tumor nests and invading disseminated cells. Further studies in melanoma cultures and mouse xenografts showed that fisetin-mediated growth inhibition was associated with dephosphorylation of AKT, mTOR and p70S6K proteins. In silico modeling indicated direct interaction of fisetin with mTOR and p70S6K with favorable free energy values. These findings were validated by cell-free competition assays that established binding of fisetin to p70S6K and mTOR while little affinity was detected with AKT. Kinase activity studies reflected similar trend with % inhibition observed for p70S6K and mTOR at lower doses than AKT. Our studies characterized, for the first time, the differential interactions of any botanical agent with kinases involved in melanoma growth and demonstrate that fisetin inhibits mTOR and p70S6K through direct binding while the observed inhibitory effect of fisetin on AKT is mediated indirectly, through targeting interrelated pathways. PMID:24675012

Syed, Deeba N; Chamcheu, Jean-Christopher; Khan, Mohammad Imran; Sechi, Mario; Lall, Rahul K; Adhami, Vaqar M; Mukhtar, Hasan

2014-06-01

31

Octreotide and the mTOR Inhibitor RAD001 (Everolimus) Block Proliferation and Interact with the Akt-mTOR-p70S6K Pathway in a NeuroEndocrine Tumour Cell Line  

Microsoft Academic Search

Background\\/Aim: The mode of action of the somatostatin analog octreotide on neuro-endocrine tumour proliferation is largely unknown. Overexpression of the proto-oncogene Akt\\/PKB (protein kinase B) has been demonstrated in certain neuro-endocrine tumours: Akt activates downstream proteins including mTOR and p70S6K, which play an important role in cell proliferation. RAD001 (everolimus) is a novel agent that is being trialled in the

Simona Grozinsky-Glasberg; Giulia Franchi; Mabel Teng; Chrysanthia A. Leontiou; Antônio Ribeiro de Oliveira Jr.; Paolo Dalino; Nabila Salahuddin; Márta Korbonits; Ashley B. Grossman

2008-01-01

32

Anti-angiogenic effects of Siegesbeckia glabrescens are mediated by suppression of the Akt and p70S6K-dependent signaling pathways.  

PubMed

Siegesbeckia glabrescens (SG) Makino (Compositae) has been used as a traditional medicine for the treatment of allergic and inflammatory diseases. In the present study, we report the effects and molecular mechanism of an ethanolic extract of SG on cell proliferation, migration and tube formation in vascular endothelial growth factor-A (VEGF-A)-treated human umbilical vein endothelial cells. SG treatment inhibited VEGF-A-stimulated endothelial cell proliferation through downregulation of cyclin D and upregulation of cyclin-dependent kinase inhibitors such as p27Kip1 and p21WAF1/Cip1. In addition, SG inhibited VEGF?A-stimulated endothelial cell migration and tube formation. These anti-angiogenic activities of SG were mediated by inactivation of the Akt- and p70S6K-dependent signaling pathways. Collectively, our findings demonstrate the pharmacological roles and molecular mechanism of SG in regulating angiogenic responses and support further evaluation and development of SG as a potential therapeutic agent for the treatment and prevention of angiogenesis-related diseases including cancer. PMID:25434554

Kim, Hyeon-Ju; Ko, Hee-Young; Choi, Shin-Wook; Seo, Dong-Wan

2015-02-01

33

Peroxiredoxin 1 promotes tumorigenesis through regulating the activity of mTOR/p70S6K pathway in esophageal squamous cell carcinoma.  

PubMed

The biological function of Peroxiredoxin 1 (Prdx1) in cancer is still ambiguous, and its mechanism has not been elucidated so far. Previous studies have shown that Prdx1 functions as tumor suppressor in several types of cancers, but other studies have indicated that it is overexpressed in some types of human cancers, and inhibition of Prdx1 by shRNA contributes to radiosensitivity and chemosensitivity. In this study, a suppression subtractive hybridization cDNA library between esophageal squamous cell carcinoma (ESCC) cell line EC9706 and noncancerous esophageal epithelial cell line Het-1A was constructed, and 11 tumorigenesis-associated genes including Prdx1 were isolated. In addition, we further confirmed that Prdx1 was overexpressed in ESCC cells at the level of protein compared with Het-1A (P < 0.05). Inhibition of Prdx1 by shRNA lentivirus decreased cell proliferation and invasion, and induced cell apoptosis, but did not affect cell cycle distribution of EC9706 cells (P > 0.05). Importantly, the total proteins of mTOR and p70S6K, as well as the activity of mTOR/p70S6K signaling pathway, were decreased in Prdx1-depletion EC9706 cells. Furthermore, the activity of mTOR/p70S6K signaling pathway was increased in Prdx1-overexpressing Het-1A cells. These findings mentioned above demonstrate that Prdx1 may be involved in tumorigenesis through regulation of mTOR/p70S6K pathway in ESCC. PMID:25579166

Gong, Fanghua; Hou, Guiqin; Liu, Hongtao; Zhang, Mingzhi

2015-02-01

34

Alpha Lipoic Acid Modulated High Glucose-Induced Rat Mesangial Cell Dysfunction via mTOR/p70S6K/4E-BP1 Pathway  

PubMed Central

The aim of this study was to investigate whether alpha lipoic acid (LA) regulates high glucose-induced mesangial cell proliferation and extracellular matrix production via mTOR/p70S6K/4E-BP1 signaling. The effect of LA on high glucose-induced cell proliferation, fibronectin (FN), and collagen type I (collagen-I) expression and its mechanisms were examined in cultured rat mesangial cells by methylthiazol tetrazolium (MTT) assay, flow cytometry, ELISA assay, and western blot, respectively. LA at a relatively low concentration (0.25?mmol/L) acted as a growth factor in rat mesangial cells, promoted entry of cell cycle into S phase, extracellular matrix formation, and phosphorylated AKT, mTOR, p70S6K, and 4E-BP1. These effects disappeared when AKT expression was downregulated with PI3K/AKT inhibitor LY294002. Conversely, LA at a higher concentration (1.0?mmol/L) inhibited high glucose-induced rat mesangial cell proliferation, entry of cell cycle into S phase, and extracellular matrix exertion, as well as phosphorylation of mTOR, p70S6K, and 4E-BP1 but enhanced the activity of AMPK. However, these effects disappeared when AMPK activity was inhibited with CaMKK inhibitor STO-609. These results suggest that LA dose-dependently regulates mesangial cell proliferation and matrix protein secretion by mTOR/p70S6K/4E-BP1 signaling pathway under high glucose conditions.

Lv, Chuan; Wu, Can; Zhou, Yue-hong; Shao, Ying; Wang, Guan; Wang, Qiu-yue

2014-01-01

35

Ascofuranone suppresses EGF-induced HIF-1? protein synthesis by inhibition of the Akt/mTOR/p70S6K pathway in MDA-MB-231 breast cancer cells  

SciTech Connect

Hypoxia-inducible factor (HIF)-1 plays an important role in tumor progression, angiogenesis and metastasis. In this study, we investigated the potential molecular mechanisms underlying the anti-angiogenic effect of ascofuranone, an isoprenoid antibiotic from Ascochyta viciae, in epidermal growth factor (EGF)-1 responsive human breast cancer cells. Ascofuranone significantly and selectively suppressed EGF-induced HIF-1? protein accumulation, whereas it did not affect the expression of HIF-1?. Furthermore, ascofuranone inhibited the transcriptional activation of vascular endothelial growth factor (VEGF) by reducing protein HIF-1?. Mechanistically, we found that the inhibitory effects of ascofuranone on HIF-1? protein expression are associated with the inhibition of synthesis HIF-1? through an EGF-dependent mechanism. In addition, ascofuranone suppressed EGF-induced phosphorylation of Akt/mTOR/p70S6 kinase, but the phosphorylation of ERK/JNK/p38 kinase was not affected by ascofuranone. These results suggest that ascofuranone suppresses EGF-induced HIF-1? protein translation through the inhibition of Akt/mTOR/p70S6 kinase signaling pathways and plays a novel role in the anti-angiogenic action. - Highlights: • Inhibitory effect of ascofuranone on HIF-1? expression is EGF-specific regulation. • Ascofuranone decreases HIF-1? protein synthesis through Akt/mTOR pathways. • Ascofuranone suppresses EGF-induced VEGF production and tumor angiogenesis.

Jeong, Yun-Jeong; Cho, Hyun-Ji [Research Institute of Biomedical Engineering and Department of Medicine, Catholic University of Daegu School of Medicine, Daegu 705-718 (Korea, Republic of); Magae, Junji [Magae Bioscience Institute, 49-4 Fujimidai, Tsukuba 300-1263 (Japan); Lee, In-Kyu [Department of Internal Medicine, Kyungpook National University School of Medicine, Daegu 700-721 (Korea, Republic of); Park, Keun-Gyu, E-mail: kpark@knu.ac.kr [Department of Internal Medicine, Kyungpook National University School of Medicine, Daegu 700-721 (Korea, Republic of); Chang, Young-Chae, E-mail: ycchang@cu.ac.kr [Research Institute of Biomedical Engineering and Department of Medicine, Catholic University of Daegu School of Medicine, Daegu 705-718 (Korea, Republic of)

2013-12-15

36

MiR-145 is downregulated in human ovarian cancer and modulates cell growth and invasion by targeting p70S6K1 and MUC1  

SciTech Connect

Highlights: •MiR-145 is downregulated in human ovarian cancer. •MiR-145 targets p70S6K1 and MUC1. •p70S6K1 and MUC1 are involved in miR-145 mediated tumor cell growth and cell invasion, respectively. -- Abstract: MicroRNAs (miRNAs) are a family of small non-coding RNA molecules that regulate gene expression at post-transcriptional levels. Previous studies have shown that miR-145 is downregulated in human ovarian cancer; however, the roles of miR-145 in ovarian cancer growth and invasion have not been fully demonstrated. In the present study, Northern blot and qRT-PCR analysis indicate that miR-145 is downregulated in ovarian cancer tissues and cell lines, as well as in serum samples of ovarian cancer, compared to healthy ovarian tissues, cell lines and serum samples. Functional studies suggest that miR-145 overexpression leads to the inhibition of colony formation, cell proliferation, cell growth viability and invasion, and the induction of cell apoptosis. In accordance with the effect of miR-145 on cell growth, miR-145 suppresses tumor growth in vivo. MiR-145 is found to negatively regulate P70S6K1 and MUC1 protein levels by directly targeting their 3?UTRs. Importantly, the overexpression of p70S6K1 and MUC1 can restore the cell colony formation and invasion abilities that are reduced by miR-145, respectively. MiR-145 expression is increased after 5-aza-CdR treatment, and 5-aza-CdR treatment results in the same phenotype as the effect of miR-145 overexpression. Our study suggests that miR-145 modulates ovarian cancer growth and invasion by suppressing p70S6K1 and MUC1, functioning as a tumor suppressor. Moreover, our data imply that miR-145 has potential as a miRNA-based therapeutic target for ovarian cancer.

Wu, Huijuan [Department of Gynecological Oncology, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center of Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin 300060 (China)] [Department of Gynecological Oncology, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center of Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin 300060 (China); Xiao, ZhengHua [Department of gynecology, Yongchuan Affiliated Hospital of Chongqing Medical University, Chongqing City 404100 (China)] [Department of gynecology, Yongchuan Affiliated Hospital of Chongqing Medical University, Chongqing City 404100 (China); Wang, Ke; Liu, Wenxin [Department of Gynecological Oncology, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center of Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin 300060 (China)] [Department of Gynecological Oncology, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center of Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin 300060 (China); Hao, Quan, E-mail: quanhao2002@163.com [Department of Gynecological Oncology, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center of Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin 300060 (China)] [Department of Gynecological Oncology, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center of Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin 300060 (China)

2013-11-29

37

Tanshinone IIA induces autophagic cell death via activation of AMPK and ERK and inhibition of mTOR and p70 S6K in KBM-5 leukemia cells.  

PubMed

Although tanshinone IIA (Tan IIA) from Salviae miltiorrhizae was known to induce apoptosis in various cancers, its underlying mechanism of autophagic cell death was not reported yet. Thus, in the present study, the molecular mechanism of autophagic cell death by Tan IIA was investigated in KBM-5 leukemia cells. Tan IIA significantly increased the expression of microtubule-associated protein light chain 3 (LC3) II as a hallmark of autophagy in western blotting and immunofluorescence staining. Tan IIA augmented the phosphorylation of adenosine monophosphate-activated protein kinase (AMPK) and attenuated the phosphorylation of mammalian target of rapamycin (mTOR) and p70 S6K in a dose-dependent manner. Conversely, autophagy inhibitor 3-methyladenine partly reversed the cytotoxicity and the phosphorylation of AMPK, mTOR and p70 S6K induced by Tan IIA in KBM-5 leukemia cells. In addition, Tan IIA dramatically activated the extracellular signal regulated kinase (ERK) signaling pathway including Raf, ERK and p90 RSK in a dose-dependent and time-dependent manner. Consistently, ERK inhibitor PD184352 suppressed LC3-II activation induced by Tan IIA, whereas PD184352 and PD98059 did not affect poly (ADP-ribose) polymerase cleavage and sub-G1 accumulation induced by Tan IIA in KBM-5 leukemia cells. Furthermore, Tan IIA could induce autophagy via LC3-II activation in various cancer cells such as prostate (PC-3), multiple myeloma (U266), lung (NCI-H460), and breast (MDA-MB-231) cells. Overall, these findings suggest that Tan IIA induces autophagic cell death via activation of AMPK and ERK and inhibition of mTOR and p70 S6K in KBM-5 cells as a potent natural compound for leukemia treatment. PMID:23813779

Yun, Sun-Mi; Jung, Ji Hoon; Jeong, Soo-Jin; Sohn, Eun Jung; Kim, Bonglee; Kim, Sung-Hoon

2014-03-01

38

Inactivation of NF-?B p50 Leads to Insulin Sensitization in Liver through Post-translational Inhibition of p70S6K*  

PubMed Central

In this study, we investigated the metabolic phenotype of the NF-?B p50 knock-out (p50-KO) mice. Compared with wild type mice, the p50-KO mice had an increase in food intake, but a decrease in body fat content. On chow diet, their blood glucose dropped much more than the wild type (WT) mice in the insulin tolerance test. Their glucose infusion rate was 30% higher than that of the WT mice in the hyperinsulinemic-euglycemic clamp. Their hepatic glucose production was suppressed more actively by insulin, and their insulin-induced glucose uptake was not altered in skeletal muscle or adipose tissue. In the liver, their p70S6K (S6K1) protein was significantly lower, and tumor necrosis factor-? (TNF-?) expression was much higher. Their S6K1 protein was reduced by TNF-? treatment in the primary culture of hepatocytes. S6K1 reduction was blocked by the proteasome inhibitor MG132. In their livers, IKK2 (IKK?) activity was reduced together with IKK?. Their S6K1 degradation was dependent on IKK2 deficiency. Reconstitution of the S6K1 protein in their liver blocked the increase in insulin sensitivity. S6K1 degradation was not observed in hepatocytes of the WT mice. The data suggest that inactivation of NF-?B p50 leads to suppression of IKK2 activity in the liver. IKK2 deficiency leads to S6K1 inhibition through TNF-induced protein degradation. The S6K1 reduction may contribute to insulin sensitivity in p50-KO mice. This study suggests that hepatic S6K1 may be a drug target in the treatment of insulin resistance. PMID:19433583

Gao, Zhanguo; Yin, Jun; Zhang, Jin; He, Qing; McGuinness, Owen P.; Ye, Jianping

2009-01-01

39

?-santalol inhibits the angiogenesis and growth of human prostate tumor growth by targeting vascular endothelial growth factor receptor 2-mediated AKT/mTOR/P70S6K signaling pathway  

PubMed Central

Background VEGF receptor 2 (VEGFR2) inhibitors, as efficient antiangiogenesis agents, have been applied in the cancer treatment. However, recently, most of these anticancer drugs have some adverse effects. Discovery of novel VEGFR2 inhibitors as anticancer drug candidates is still needed. Methods We used ?-santalol and analyzed its inhibitory effects on human umbilical vein endothelial cells (HUVECs) and Prostate tumor cells (PC-3 or LNCaP) in vitro. Tumor xenografts in nude mice were used to examine the in vivo activity of ?-santalol. Results ?-santalol significantly inhibits HUVEC proliferation, migration, invasion, and tube formation. Western blot analysis indicated that ?-santalol inhibited VEGF-induced phosphorylation of VEGFR2 kinase and the downstream protein kinases including AKT, ERK, FAK, Src, mTOR, and pS6K in HUVEC, PC-3 and LNCaP cells. ?-santalol treatment inhibited ex vivo and in vivo angiogenesis as evident by rat aortic and sponge implant angiogenesis assay. ?-santalol significantly reduced the volume and the weight of solid tumors in prostate xenograft mouse model. The antiangiogenic effect by CD31 immunohistochemical staining indicated that ?-santalol inhibited tumorigenesis by targeting angiogenesis. Furthermore, ?-santalol reduced the cell viability and induced apoptosis in PC-3 cells, which were correlated with the downregulation of AKT, mTOR and P70S6K expressions. Molecular docking simulation indicated that ?-santalol form hydrogen bonds and aromatic interactions within the ATP-binding region of the VEGFR2 kinase unit. Conclusion ?-santalol inhibits angiogenesis by targeting VEGFR2 regulated AKT/mTOR/P70S6K signaling pathway, and could be used as a potential drug candidate for cancer therapy. PMID:24261856

2013-01-01

40

Fibronectin Stimulates Non-Small Cell Lung Carcinoma Cell Growth through Activation of Akt\\/Mammalian Target of Rapamycin\\/S6 Kinase and Inactivation of LKB1\\/AMP Activated Protein Kinase Signal Pathways  

Microsoft Academic Search

The Akt\\/mammalian target of rapamycin (mTOR)\\/ribosomal protein S6 kinase (p70S6K) pathway is considered a central regulator of protein synthesis and of cell proliferation, diffe- rentiation, and survival. However, the role of the Akt\\/mTOR\\/ p70S6K pathway in lung carcinoma remains unknown. We previously showed that fibronectin, a matrix glycoprotein highly expressed in tobacco-related lung disease, stimulates non-small cell lung carcinoma (NSCLC)

ShouWei Han; Fadlo R. Khuri; Jesse Roman

41

Dose-dependent increases in p70S6K phosphorylation and intramuscular branched-chain amino acids in older men following resistance exercise and protein intake.  

PubMed

Resistance exercise and whey protein supplementation are effective strategies to activate muscle cell anabolic signaling and ultimately promote increases in muscle mass and strength. In the current study, 46 healthy older men aged 60-75 (69.0 ± 0.55 years, 85.9 ± 1.8 kg, 176.8 ± 1.0 cm) performed a single bout of unaccustomed lower body resistance exercise immediately followed by ingestion of a noncaloric placebo beverage or supplement containing 10, 20, 30, or 40 g of whey protein concentrate (WPC). Intramuscular amino acid levels in muscle biopsy samples were measured by Gas Chromatography-Mass Spectrometry (GC-MS) at baseline (before exercise and WPC supplementation) plus at 2 h and 4 h post exercise. Additionally, the extent of p70S6K phosphorylation at Thr389 in muscle biopsy homogenates was assessed by western blot. Resistance exercise alone reduced intramuscular branch chain amino acid (BCAA; leucine, isoleucine, and valine) content. Supplementation with increasing doses of whey protein prevented this fall in muscle BCAAs during postexercise recovery and larger doses (30 g and 40 g) significantly augmented postexercise muscle BCAA content above that observed following placebo ingestion. Additionally, the fold change in the phosphorylation of p70S6K (Thr389) at 2 h post exercise was correlated with the dose of whey protein consumed (r = 0.51, P < 001) and was found to be significantly correlated with intramuscular leucine content (r = 0.32, P = 0.026). Intramuscular BCAAs, and leucine in particular, appear to be important regulators of anabolic signaling in aged human muscle during postexercise recovery via reversal of exercise-induced declines in intramuscular BCAAs. PMID:25107987

D'Souza, Randall F; Marworth, James F; Figueiredo, Vandre C; Della Gatta, Paul A; Petersen, Aaron C; Mitchell, Cameron J; Cameron-Smith, David

2014-08-01

42

Collaboration of geldanamycin-activated P70S6K and Hsp70 against beta-amyloid-induced hippocampal apoptosis: an approach to long-term memory and learning.  

PubMed

One of the neuropathological hallmarks of Alzheimer's disease (AD) is the accumulation of beta-amyloid peptides (A?) in senile plaques. A?-induced oxidative stress is believed to be responsible for degeneration and apoptosis of neurons and consequent cognitive and memory deficits. Here, we investigated the possible neuroprotective effect of the heat shock protein 90 (Hsp90) inhibitor geldanamycin (GA) against amyloid pathogenesis in adult male Wistar rats. GA or vehicle was injected into the lateral cerebral ventricles of rats 24 h before injection of A? (1-42) in CA1 area of hippocampus. The learning and memory of the rats were assessed 7 days after injection of A? using passive avoidance (PA) task. As potential contributing factors in A?-induced memory decline, we evaluated apoptotic markers and also used terminal-transferase UTP nick end labeling (TUNEL) technique to detect apoptosis in the hippocampus of A?-injected rats. Our behavioral data suggest that GA pretreatment can significantly suppress memory deficits in A?-injected rats. There was also not only a marked increase in Hsp70 level but also upregulated 70 kDa ribosomal protein S6 kinase (p70S6K) in the hippocampus of GA-treated groups with a reduction in apoptotic factors including caspase-3, poly (ADP-ribose) polymerase, Bax/Bcl-2 ratio, and TUNEL-positive cells as well. Thus, we conclude that GA exerts its protective effects against A? (1-42) toxicity and memory deficits, at least in part, by upregulating of Hsp70 and P70S6K. PMID:25576151

Zare, Nayereh; Motamedi, Fereshteh; Digaleh, Hadi; Khodagholi, Fariba; Maghsoudi, Nader

2015-03-01

43

Tangeretin and its metabolite 4?-hydroxytetramethoxyflavone attenuate EGF-stimulated cell cycle progression in hepatocytes; role of inhibition at the level of mTOR/p70S6K  

PubMed Central

BACKGROUND AND PURPOSE The mechanisms by which the dietary compound tangeretin has anticancer effects may include acting as a prodrug, forming an antiproliferative product in cancer cells. Here we show that tangeretin also inhibits cell cycle progression in hepatocytes and investigate the role of its primary metabolite 4?-hydroxy-5,6,7,8-tetramethoxyflavone (4?-OH-TMF) in this effect. EXPERIMENTAL APPROACH We used epidermal growth factor (EGF)-stimulated rat hepatocytes, with [3H]-thymidine incorporation into DNA as an index of progression to S-phase of the cell cycle, and Western blots for phospho-proteins involved in the cell signalling cascade. KEY RESULTS Incubation of tangeretin with microsomes expressing CYP1A, or with hepatocytes, generated a primary product we identified as 4?-OH-TMF. Low micromolar concentrations of tangeretin or 4?-OH-TMF gave a concentration-dependent inhibition of EGF-stimulated progression to S-phase while having little effect on cell viability. To determine whether time for conversion of tangeretin to an active metabolite would enhance the inhibitory effect we used long pre-incubations; this reduced the inhibitory effect, in parallel with a reduction in the concentration of tangeretin. The EGF-stimulation of hepatocyte cell cycle progression requires signalling through Akt/mTOR/p70S6K kinase cascades. The tangeretin metabolite 4?-OH-TMF selectively inhibited S6K phosphorylation in the absence of significant inhibition of upstream Akt activity, suggesting an effect at the level of mTOR. CONCLUSIONS AND IMPLICATIONS Tangeretin and 4?-OH-TMF both inhibit cell cycle progression in primary hepatocytes. The inhibition of p70S6K phosphorylation by 4?-OH-TMF raises the possibility that inhibition of the mTOR pathway may contribute to the anticancer influence of a flavonoid-rich diet. PMID:21198542

Cheng, Z; Surichan, S; Ruparelia, K; Arroo, R; Boarder, MR

2011-01-01

44

Tanshinone IIA Inhibits HIF-1? and VEGF Expression in Breast Cancer Cells via mTOR/p70S6K/RPS6/4E-BP1 Signaling Pathway  

PubMed Central

Hypoxia-inducible factor 1? (HIF-1?) and vascular endothelial growth factor (VEGF) play important roles in angiogenesis and tumor growth. Tanshinone IIA (T2A) is a novel antiangiogenic agent with promising antitumor effects; however, the molecular mechanism underlying the antiangiogenic effects of T2A remains unclear. In the present study, we provided evidence showing that T2A inhibited angiogenesis and breast cancer growth by down-regulating VEGF expression. Specifically, T2A repressed HIF-1? expression at the translational level and inhibited the transcriptional activity of HIF-1?, which led to the down-regulation of VEGF expression. Suppression of HIF-1? synthesis by T2A correlated with strong dephosphorylation of mammalian target of rapamycin (mTOR) and its effectors ribosomal protein S6 kinase (p70S6K) and eukaryotic initiation factor 4E-binding protein-1 (4E-BP1), a pathway regulating HIF-1? expression at the translational level. In addition, we also found that T2A inhibited the angiogenesis and growth of human breast cancer xenografts in nude mice through suppression of HIF-1? and VEGF. Our study provides novel perspectives and potential targets for the treatment of human breast cancer. PMID:25659153

Li, Guobing; Shan, Changyu; Liu, Lei; Zhou, Ting; Zhou, Jing; Hu, Xiaoye; Chen, Yibiao; Cui, Hongjuan; Gao, Ning

2015-01-01

45

The discovery of potent ribosomal S6 kinase inhibitors by high-throughput screening and structure-guided drug design  

PubMed Central

The ribosomal P70 S6 kinases play a crucial role in PI3K/mTOR regulated signalling pathways and are therefore potential targets for the treatment of a variety of diseases including diabetes and cancer. In this study we describe the identification of three series of chemically distinct S6K1 inhibitors. In addition, we report a novel PKA-S6K1 chimeric protein with five mutations in or near its ATP-binding site, which was used to determine the binding mode of two of the three inhibitor series, and provided a robust system to aid the optimisation of the oxadiazole-substituted benzimidazole inhibitor series. We show that the resulting oxadiazole-substituted aza-benzimidazole is a potent and ligand efficient S6 kinase inhibitor, which blocks the phosphorylation of RPS6 at Ser235/236 in TSC negative HCV29 human bladder cancer cells by inhibiting S6 kinase activity and thus provides a useful tool compound to investigate the function of S6 kinases. PMID:24072592

Kalusa, Andrew; Cano, Celine; Travers, Jon; Boxall, Kathy; Chow, Chiau Ling; Burns, Sam; Schmitt, Jessica; Pickard, Lisa; Barillari, Caterina; McAndrew, P. Craig; Clarke, Paul A.; Linardopoulos, Spiros; Griffin, Roger J.; Aherne, G. Wynne; Raynaud, Florence I.; Workman, Paul; Jones, Keith; van Montfort, Rob L.M.

2013-01-01

46

The acute effects of strength, endurance and concurrent exercises on the Akt/mTOR/p70S6K1 and AMPK signaling pathway responses in rat skeletal muscle  

PubMed Central

The activation of competing intracellular pathways has been proposed to explain the reduced training adaptations after concurrent strength and endurance exercises (CE). The present study investigated the acute effects of CE, strength exercises (SE), and endurance exercises (EE) on phosphorylated/total ratios of selected AMPK and Akt/mTOR/p70S6K1 pathway proteins in rats. Six animals per exercise group were killed immediately (0 h) and 2 h after each exercise mode. In addition, 6 animals in a non-exercised condition (NE) were killed on the same day and under the same conditions. The levels of AMPK, phospho-Thr172AMPK (p-AMPK), Akt, phospho-Ser473Akt (p-Akt), p70S6K1, phospho-Thr389-p70S6K1 (p-p70S6K1), mTOR, phospho-Ser2448mTOR (p-mTOR), and phospho-Thr1462-TSC2 (p-TSC2) expression were evaluated by immunoblotting in total plantaris muscle extracts. The only significant difference detected was an increase (i.e., 87%) in Akt phosphorylated/total ratio in the CE group 2 h after exercise compared to the NE group (P = 0.002). There were no changes in AMPK, TSC2, mTOR, or p70S6K1 ratios when the exercise modes were compared to the NE condition (P ? 0.05). In conclusion, our data suggest that low-intensity and low-volume CE might not blunt the training-induced adaptations, since it did not activate competing intracellular pathways in an acute bout of strength and endurance exercises in rat skeletal muscle. PMID:23598645

Souza, E.O.de; Tricoli, V.; Bueno, C.; Pereira, M.G.; Brum, P.C.; Oliveira, E.M.; Roschel, H.; Aoki, M.S.; Urginowitsch, C.

2013-01-01

47

4EBP1/eIF4E and p70S6K/RPS6 axes play critical and distinct roles in hepatocarcinogenesis driven by AKT and N-Ras proto-oncogenes in mice.  

PubMed

Concomitant expression of activated forms of v-akt murine thymoma viral oncogene homolog (AKT) and Ras in mouse liver (AKT/Ras) leads to rapid tumor development through strong activation of the mammalian target of rapamycin complex 1 (mTORC1) pathway. mTORC1 functions by regulating p70S6K/ribosomal protein S6 (RPS6) and eukaryotic translation initiation factor 4E-binding protein 1/ eukaryotic translation initiation factor 4E (4EBP1/eIF4E) cascades. How these cascades contribute to hepatocarcinogenesis remains unknown. Here, we show that inhibition of the RPS6 pathway by rapamycin effectively suppressed, whereas blockade of the 4EBP1/eIF4E cascade by 4EBP1A4, an unphosphorylatable form of 4EBP1, significantly delayed, AKT/Ras-induced hepatocarcinogenesis. Combined treatment with rapamycin and 4EBP1A4 completely inhibited AKT/Ras hepatocarcinogenesis. This strong antineoplastic effect was successfully recapitulated by ablating regulatory associated protein of mTORC1, the major subunit of mTORC1, in AKT/Ras-overexpressing livers. Furthermore, we demonstrate that overexpression of eIF4E, the proto-oncogene whose activity is specifically inhibited by 4EBP1, resulted in hepatocellular carcinoma (HCC) development in cooperation with activated Ras. Mechanistically, we identified the ectonucleoside triphosphate diphosphohydrolase 5/ adenylate kinase 1/cytidine monophosphate kinase 1 axis and the mitochondrial biogenesis pathway as targets of the 4EBP1/eIF4E cascade in AKT/Ras and Ras/eIF4E livers as well as in human HCC cell lines and tissues. Conclusions: Complete inhibition of mTORC1 is required to suppress liver cancer development induced by AKT and Ras proto-oncogenes in mice. The mTORC1 effectors, RPS6 and eIF4E, play distinct roles and are both necessary for AKT/Ras hepatocarcinogenesis. These new findings might open the way for innovative therapies against human HCC. (Hepatology 2014). PMID:25145583

Wang, Chunmei; Cigliano, Antonio; Jiang, Lijie; Li, Xiaolei; Fan, Biao; Pilo, Maria G; Liu, Yan; Gui, Bing; Sini, Marcella; Smith, Jeffrey W; Dombrowski, Frank; Calvisi, Diego F; Evert, Matthias; Chen, Xin

2014-08-22

48

Activation of the PI3K/Akt/mTOR/p70S6K Pathway is Involved in S100A4-induced Viability and Migration in Colorectal Cancer Cells  

PubMed Central

The S100 protein family member S100A4 regulates various cellular functions. Previous studies have shown that elevated expression of S100A4 is associated with progression and metastasis of colorectal cancer (CRC). However, little is known about whether and how S100A4 contributes to CRC development. In our present study, the elevated expression of S100A4 in CRC tissues compared to matched adjacent normal tissues was confirmed by immunohistochemistry, semi-quantitative RT-PCR and Western blot. Adenovirus-mediated S100A4 overexpression obviously enhanced viability and migration of CRC cells, which was detected by MTT assay and transwell assay, respectively. Additionally, S100A4 overexpression increased the phosphorylation levels of Akt, mTOR and p70S6K. These effects of S100A4 were abolished by treatment with either the specific PI3K/Akt inhibitor LY294002, or the specific mTOR/p70S6K inhibitor rapamycin. Furthermore, overexpression of S100A4 resulted in upregulation of VEGF and downregulation of E-cadherin, which were strongly reversed by either LY294002 or rapamycin. Altogether, our results demonstrate that activation of the PI3K/Akt/mTOR/p70S6K signaling pathway is involved in S100A4-induced viability, migration, upregulation of VEGF and downregulation of E-cadherin in CRC cells. PMID:24936148

Wang, Haiyan; Duan, Liang; Zou, Zhengyu; Li, Huan; Yuan, Shimei; Chen, Xian; Zhang, Yunyuan; Li, Xueru; Sun, Hui; Zha, He; Zhang, Yan; Zhou, Lan

2014-01-01

49

Inhibition of S6 kinase suppresses the apoptotic effect of eIF4E ablation by inducing TGF-?-dependent G1 cell cycle arrest.  

PubMed

The mammalian target of rapamycin complex 1 (mTORC1) is a critical regulator of cap-dependent translation through its direct activation of ribosomal protein p70 S6 kinase (S6 kinase) and indirect activation of eukaryotic initiation factor 4E (eIF4E). We recently reported that inhibition of eIF4E expression caused apoptosis in cancer cells in the absence of serum. This was indicated by treatment with the mTORC1 inhibitor rapamycin, which suppressed both S6 kinase and 4E-BP1 phosphorylation (dephosphorylated 4E-BP1 binds and inactivates eIF4E), or by knockdown of eIF4E. We report here that knockdown of eIF4E also causes apoptosis in the presence of serum. This was unexpected because rapamycin induces G1 cell cycle arrest in the presence of serum. Upon investigation, we have found that inactivated S6 kinase prevents the apoptotic effect observed by singular knockdown of eIF4E and results in G1 cell cycle arrest. This effect is dependent on TGF-? (transforming growth factor-?) signaling which contributes to G1 cell cycle arrest. Suppression of S6 kinase phosphorylation alone is insufficient to mediate cell cycle arrest, indicating that complete G1 cell cycle arrest is due to suppression of both S6 kinase and eIF4E. These data indicate that the cytostatic effect of rapamycin is suppression of both S6 kinase and eIF4E, while the cytotoxic effects are due suppression of eIF4E in the absence of S6 kinase-dependent activation of TGF-? signals. Our findings place an importance on the evaluating the activity/expression level of S6 kinase and eIF4E as readouts for rapamycin/rapalog efficacy. PMID:23376634

Yellen, Paige; Chatterjee, Amrita; Preda, Angela; Foster, David A

2013-06-10

50

Inhibition of S6 kinase suppresses the apoptotic effect of eIF4E ablation by inducing TGF-?-dependent G1 cell cycle arrest  

PubMed Central

The mammalian target of rapamycin complex 1 (mTORC1) is a critical regulator of cap-dependent translation through its direct activation of ribosomal protein p70 S6 kinase (S6 kinase) and indirect activation of eukaryotic initiation factor 4E (eIF4E). We recently reported that inhibition of eIF4E expression caused apoptosis in cancer cells in the absence of serum. This was indicated by treatment with the mTORC1 inhibitor rapamycin, which suppressed both S6 kinase and 4E-BP1 phosphorylation (dephosphorylated 4E-BP1 binds and inactivates eIF4E), or by knockdown of eIF4E. We report here that knockdown of eIF4E also causes apoptosis in the presence of serum. This was unexpected because rapamycin induces G1 cell cycle arrest in the presence of serum. Upon investigation, we have found that inactivated S6 kinase prevents the apoptotic effect observed by singular knockdown of eIF4E and results in G1 cell cycle arrest. This effect is dependent on TGF-? (transforming growth factor-?) signaling which contributes to G1 cell cycle arrest. Suppression of S6 kinase phosphorylation alone is insufficient to mediate cell cycle arrest, indicating that complete G1 cell cycle arrest is due to suppression of both S6 kinase and eIF4E. These data indicate that the cytostatic effect of rapamycin is suppression of both S6 kinase and eIF4E, while the cytotoxic effects are due suppression of eIF4E in the absence of S6 kinase-dependent activation of TGF-? signals. Our findings place an importance on the evaluating the activity/expression level of S6 kinase and eIF4E as readouts for rapamycin/rapalog efficacy. PMID:23376634

Yellen, Paige; Chatterjee, Amrita; Preda, Angela; Foster, David A.

2013-01-01

51

BI-D1870 is a specific inhibitor of the p90 RSK (ribosomal S6 kinase) isoforms in vitro and in vivo.  

PubMed

Hormones and growth factors induce the activation of a number of protein kinases that belong to the AGC subfamily, including isoforms of PKA, protein kinase B (also known as Akt), PKC, S6K p70 (ribosomal S6 kinase), RSK (p90 ribosomal S6 kinase) and MSK (mitogen- and stress-activated protein kinase), which then mediate many of the physiological processes that are regulated by these extracellular agonists. It can be difficult to assess the individual functions of each AGC kinase because their substrate specificities are similar. Here we describe the small molecule BI-D1870, which inhibits RSK1, RSK2, RSK3 and RSK4 in vitro with an IC(50) of 10-30 nM, but does not signi-ficantly inhibit ten other AGC kinase members and over 40 other protein kinases tested at 100-fold higher concentrations. BI-D1870 is cell permeant and prevents the RSK-mediated phorbol ester- and EGF (epidermal growth factor)-induced phosphoryl-ation of glycogen synthase kinase-3beta and LKB1 in human embry-onic kidney 293 cells and Rat-2 cells. In contrast, BI-D1870 does not affect the agonist-triggered phosphorylation of substrates for six other AGC kinases. Moreover, BI-D1870 does not suppress the phorbol ester- or EGF-induced phosphorylation of CREB (cAMP-response-element-binding protein), consistent with the genetic evidence indicating that MSK, and not RSK, isoforms mediate the mitogen-induced phosphorylation of this transcription factor. PMID:17040210

Sapkota, Gopal P; Cummings, Lorna; Newell, Felicity S; Armstrong, Christopher; Bain, Jennifer; Frodin, Morten; Grauert, Matthias; Hoffmann, Matthias; Schnapp, Gisela; Steegmaier, Martin; Cohen, Philip; Alessi, Dario R

2007-01-01

52

The role of 3-phosphoinositide-dependent protein kinase 1 in activating AGC kinases defined in embryonic stem cells  

Microsoft Academic Search

Background: Protein kinase B (PKB), and the p70 and p90 ribosomal S6 kinases (p70 S6 kinase and p90 Rsk, respectively), are activated by phosphorylation of two residues, one in the ‘T-loop’ of the kinase domain and, the other, in the hydrophobic motif carboxy terminal to the kinase domain. The 3-phosphoinositide-dependent protein kinase 1 (PDK1) activates many AGC kinases in vitro

Michayla R. Williams; J. Simon C. Arthur; Anudharan Balendran; Jeroen van der Kaay; Valeria Poli; Philip Cohen; Dario R. Alessi

2000-01-01

53

SHP-2 regulates cell growth by controlling the mTOR/S6 kinase 1 pathway.  

PubMed

Cell growth (accumulation in cell mass) ensues through the promotion of macromolecular biosynthesis. S 6 ribosomal kinase 1 (S6K1), which is activated by the mammalian target of rapamycin, is critical for cell growth. The early events that control S6K1 signaling remain unclear. Here we show that SHP-2 suppresses S6K1 activity under conditions of growth factor deprivation. We show that under conditions of growth factor deprivation, S6K1 activity was increased in fibroblasts lacking functional SHP-2 and in cells where knock down of SHP-2 expression was established by small interference RNA. Consistent with these findings, fibroblasts lacking functional SHP-2 exhibited increased cell size as compared with wild type cells. Growth factor deprivation reduces cellular energy, and the energy-sensing 5'-AMP-activated protein kinase (AMPK) negatively regulates S6K1. We found that SHP-2 promoted AMPK activity under conditions of growth factor deprivation (low energy), suggesting that SHP-2 negatively regulates S6K1 via an AMPK-dependent pathway. These results implicate SHP-2 as an early mediator in the S6K1 signaling pathway to limit cell growth in low energy states. PMID:17229738

Zito, Christina I; Qin, Hui; Blenis, John; Bennett, Anton M

2007-03-01

54

Proliferation and survival signaling from both Jak2-V617F and Lyn involving GSK3 and mTOR/p70S6K/4EBP1 in PVTL-1 cell line newly established from acute myeloid leukemia transformed from polycythemia vera.  

PubMed

The gain of function mutation JAK2-V617F is very frequently found in myeloproliferative neoplasms (MPNs) and is strongly implicated in pathogenesis of these and other hematological malignancies. Here we report establishment of a new leukemia cell line, PVTL-1, homozygous for JAK2-V617F from a 73-year-old female patient with acute myeloid leukemia (AML) transformed from MPN. PVTL-1 is positive for CD7, CD13, CD33, CD34, CD117, HLA-DR, and MPO, and has complex karyotypic abnormalities, 44,XX,-5q,-7,-8,add(11)(p11.2),add(11)(q23),-16,+21,-22,+mar1. Sequence analysis of JAK2 revealed only the mutated allele coding for Jak2-V617F. Proliferation of PVTL-1 was inhibited and apoptosis was induced by the pan-Jak inhibitor Jak inhibitor-1 (JakI-1) or dasatinib, which inhibits the Src family kinases as well as BCR/ABL. Consistently, the Src family kinase Lyn was constitutively activated with phosphorylation of Y396 in the activation loop, which was inhibited by dasatinib but not by JakI-1. Further analyses with JakI-1 and dasatinib indicated that Jak2-V617F phosphorylated STAT5 and SHP2 while Lyn phosphorylated SHP1, SHP2, Gab-2, c-Cbl, and CrkL to induce the SHP2/Gab2 and c-Cbl/CrkL complex formation. In addition, JakI-1 and dasatinib inactivated the mTOR/p70S6K/4EBP1 pathway and reduced the inhibitory phosphorylation of GSK3 in PVTL-1 cells, which correlated with their effects on proliferation and survival of these cells. Furthermore, inhibition of GSK3 by its inhibitor SB216763 mitigated apoptosis induced by dasatinib but not by JakI-1. Together, these data suggest that apoptosis may be suppressed in PVTL-1 cells through inactivation of GSK3 by Lyn as well as Jak2-V617F and additionally through activation of STAT5 by Jak2-V617F. It is also speculated that activation of the mTOR/p70S6K/4EBP1 pathway may mediate proliferation signaling from Jak2-V617F and Lyn. PVTL-1 cells may provide a valuable model system to elucidate the molecular mechanisms involved in evolution of Jak2-V617F-expressing MPN to AML and to develop novel therapies against this intractable condition. PMID:24404189

Nagao, Toshikage; Kurosu, Tetsuya; Umezawa, Yoshihiro; Nogami, Ayako; Oshikawa, Gaku; Tohda, Shuji; Yamamoto, Masahide; Miura, Osamu

2014-01-01

55

Cordycepin, 3'-deoxyadenosine, prevents rat hearts from ischemia/reperfusion injury via activation of Akt/GSK-3?/p70S6K signaling pathway and HO-1 expression.  

PubMed

Cordycepin (3'-deoxyadenosine) isolated from Cordyceps militaris, a species of the fungal genus Cordyceps, has been shown to exhibit many pharmacological functions, such as anticancer, anti-inflammatory, and antioxidant activities. In this study, we investigated the preventive role of cordycepin in ischemic/reperfusion (I/R) injury of isolated rat hearts and anesthetized rats. After Sprague-Dawley rats received cordycepin (3, 10, and 30 mg/kg) or control (0.5 % carboxyl methylcellulose) orally once a day for a week, hearts were isolated and mounted on Langendorff heart perfusion system. Isolated hearts were perfused with Krebs-Henseleit buffer for 15-min pre-ischemic stabilization period and subjected to 30-min global ischemia and 30-min reperfusion. Cordycepin administration (10 mg/kg, p.o.) significantly increased left ventricular developed pressure during the reperfusion period compared to that in the control group, but without any effect on coronary flow. Cordycepin (10 mg/kg, p.o.) significantly increased the phosphorylation of Akt/GSK-3?/p70S6K pathways, which are known to modulate multiple survival pathways. In addition, cordycepin decreased Bax and cleaved caspase-3 expression while increasing Bcl-2 expression, Bcl-2/Bax ratio, and heme oxygenase (HO-1) expression in isolated rat hearts. In anesthetized rats subjected to 30 min occlusion of left anterior descending coronary artery/2.5-h reperfusion, cordycepin (1, 3, and 10 mg/kg, i.v.) administered 15 min before the onset of ischemia dose-dependently decreased the infarct size in left ventricle. In conclusion, cordycepin could be an attractive therapeutic candidate with oral activity against I/R-associated heart diseases such as myocardial infarction. PMID:24178833

Park, Eun-Seok; Kang, Do-Hyun; Yang, Min-Kyu; Kang, Jun Chul; Jang, Yong Chang; Park, Jong Seok; Kim, Si-Kwan; Shin, Hwa-Sup

2014-03-01

56

Growth Inhibition by Bupivacaine Is Associated with Inactivation of Ribosomal Protein S6 Kinase 1  

PubMed Central

Bupivacaine is an amide type long acting local anesthetic used for epidural anesthesia and nerve blockade in patients. Use of bupivacaine is associated with severe cytotoxicity and apoptosis along with inhibition of cell growth and proliferation. Although inhibition of Erk, Akt, and AMPK seemingly appears to mediate some of the bupivacaine effects, potential downstream targets that mediate its effect remain unknown. S6 kinase 1 is a common downstream effector of several growth regulatory pathways involved in cell growth and proliferation known to be affected by bupivacaine. We have accordingly attempted to relate the growth inhibitory effects of bupivacaine with the status of S6K1 activity and we present evidence that decrease in cell growth and proliferation by bupivacaine is mediated through inactivation of S6 kinase 1 in a concentration and time dependent manner. We also show that ectopic expression of constitutively active S6 kinase 1 imparts substantial protection from bupivacaine induced cytotoxicity. Inactivation of S6K1 though associated with loss of putative mTOR mediated phosphorylation did not correspond with loss of similar phosphorylations in 4EBP1 indicating that S6K1 inhibition was not mediated through inactivation of mTORC1 signaling pathway or its down regulation. PMID:24605337

Beigh, Mushtaq Ahmad; Showkat, Mehvish; Bashir, Basharat; Bashir, Asma; Hussain, Mahboob ul; Andrabi, Khurshid Iqbal

2014-01-01

57

Role of the phosphatidylinositol 3-kinase\\/Akt and mTOR\\/P70S6-kinase pathways in the proliferation and apoptosis in multiple myeloma  

Microsoft Academic Search

Multiple myeloma (MM) is a plasma cell malignancy preliminary localized in the bone marrow and characterized by its capacity to disseminate. IL-6 and IGF-1 have been shown to mediate proliferative and anti-apoptotic signals in plasmocytes. However, in primary plasma-cell leukemia (PCL) and in end-stage aggressive extramedullar disease, the cytokine requirement for both effects may be not mandatory. This suggests that

Frédéric Pene; Yann-Erick Claessens; Odile Muller; Franck Viguié; Patrick Mayeux; François Dreyfus; Catherine Lacombe; Didier Bouscary

2002-01-01

58

Ribosomal Protein Mutations Induce Autophagy through S6 Kinase Inhibition of the Insulin Pathway  

PubMed Central

Mutations affecting the ribosome lead to several diseases known as ribosomopathies, with phenotypes that include growth defects, cytopenia, and bone marrow failure. Diamond-Blackfan anemia (DBA), for example, is a pure red cell aplasia linked to the mutation of ribosomal protein (RP) genes. Here we show the knock-down of the DBA-linked RPS19 gene induces the cellular self-digestion process of autophagy, a pathway critical for proper hematopoiesis. We also observe an increase of autophagy in cells derived from DBA patients, in CD34+ erythrocyte progenitor cells with RPS19 knock down, in the red blood cells of zebrafish embryos with RP-deficiency, and in cells from patients with Shwachman-Diamond syndrome (SDS). The loss of RPs in all these models results in a marked increase in S6 kinase phosphorylation that we find is triggered by an increase in reactive oxygen species (ROS). We show that this increase in S6 kinase phosphorylation inhibits the insulin pathway and AKT phosphorylation activity through a mechanism reminiscent of insulin resistance. While stimulating RP-deficient cells with insulin reduces autophagy, antioxidant treatment reduces S6 kinase phosphorylation, autophagy, and stabilization of the p53 tumor suppressor. Our data suggest that RP loss promotes the aberrant activation of both S6 kinase and p53 by increasing intracellular ROS levels. The deregulation of these signaling pathways is likely playing a major role in the pathophysiology of ribosomopathies. PMID:24875531

Pereboom, Tamara C.; Goos, Yvonne J.; Seinen, Cor W.; van Oirschot, Brigitte A.; van Dooren, Rowie; Gastou, Marc; Giles, Rachel H.; van Solinge, Wouter; Kuijpers, Taco W.; Gazda, Hanna T.; Bierings, Marc B.; Da Costa, Lydie; MacInnes, Alyson W.

2014-01-01

59

Deletion of Ribosomal S6 Kinases Does Not Attenuate Pathological, Physiological, or Insulin-Like Growth Factor 1 Receptor-Phosphoinositide 3-Kinase-Induced Cardiac Hypertrophy  

Microsoft Academic Search

Ribosomal S6 kinases (S6Ks) have been depicted as critical effectors downstream of growth factor pathways, which play an important role in the regulation of protein synthesis by phosphorylating the ribosomal protein, S6. The goal of this study was to determine whether S6Ks regulate heart size, are critical for the induction of cardiac hypertrophy in response to a pathological or physiological

Julie R. McMullen; Tetsuo Shioi; Li Zhang; Oleg Tarnavski; Megan C. Sherwood; Adam L. Dorfman; Sarah Longnus; Mario Pende; Kathleen A. Martin; John Blenis; George Thomas; Seigo Izumo

2004-01-01

60

MEK1-independent activation of MAPK and MEK1-dependent activation of p70 S6 kinase by stem cell factor (SCF) in ovarian cancer cells  

SciTech Connect

We discovered a stem cell factor (SCF)-triggered, MEK1-independent, and PI3K-dependent MAPK activation pathway in the Kit-expressing ovarian cancer cell line HEY. When we knocked down MEK1 with RNA interference (RNAi) to study the function of MEK1 on the proliferation and survival of ovarian cancer cells, we found that impaired cell growth still occurred after MEK1 expression had been suppressed, although MAPK activation remained intact. This suggests that there is MEK1-independent activation of MAPK in the SCF-induced ovarian cancer cell growth process, and that MEK1 still plays a crucial role in maintaining the malignant properties of ovarian cancer cells even when it fails to activate MAPK as expected.

Liu, Lian, E-mail: tounao@126.com [Department of Chemotherapy, Cancer Center, Qilu Hospital, Shandong University, 107 Wenhuaxi Road, Jinan 250012 (China) [Department of Chemotherapy, Cancer Center, Qilu Hospital, Shandong University, 107 Wenhuaxi Road, Jinan 250012 (China); Institute of Immunology, School of Medicine, Shandong University, Jinan 250012 (China); Zhang, Xin [Department of Chemotherapy, Cancer Center, Qilu Hospital, Shandong University, 107 Wenhuaxi Road, Jinan 250012 (China)] [Department of Chemotherapy, Cancer Center, Qilu Hospital, Shandong University, 107 Wenhuaxi Road, Jinan 250012 (China); Du, Chao; Zhang, Xiaoning; Hou, Nan; Zhao, Di [Institute of Immunology, School of Medicine, Shandong University, Jinan 250012 (China)] [Institute of Immunology, School of Medicine, Shandong University, Jinan 250012 (China); Sun, Jianzhi; Li, Li; Wang, Xiuwen [Department of Chemotherapy, Cancer Center, Qilu Hospital, Shandong University, 107 Wenhuaxi Road, Jinan 250012 (China)] [Department of Chemotherapy, Cancer Center, Qilu Hospital, Shandong University, 107 Wenhuaxi Road, Jinan 250012 (China); Ma, Chunhong [Institute of Immunology, School of Medicine, Shandong University, Jinan 250012 (China)] [Institute of Immunology, School of Medicine, Shandong University, Jinan 250012 (China)

2009-05-01

61

PDGF- and insulin-dependent pp70S6k activation mediated by phosphatidylinositol-3OH kinase  

Microsoft Academic Search

PLATELET-DERIVED growth factor receptor (PDGF-R) phosphory-lation at tyrosines 740\\/751 and insulin receptor phosphorylation of insulin receptor substrate-1 effects the recruitment and activation of phosphatidylinositol-3-OH kinase (PIK)1-5. Changes in PI(3)K activity correlate with cell growth but its downstream signal transducers are unknown4,5. Activation of the 70\\/85K S6 kinases (pp70S6k) by serine phosphorylation6,7 results in 40S ribosomal protein S6 phosphorylation and is

Jongkyeong Chung; Katherine P. Lemon; Andrius Kazlauskas; John Blenis

1994-01-01

62

Molecular Characterization and Expression Analysis of S6K1 in Cashmere Goats (Capra hircus).  

PubMed

p70 ribosomal S6 kinase (p70S6K) can integrate nutrient and growth factor signals to promote cell growth and survival. We report our molecular characterization of the complementary DNA (cDNA) that encodes the goat p70S6K gene 40S ribosomal S6 kinase 1 (S6K1) (GenBank accession GU144017) and its 3' noncoding sequence in Inner Mongolia Cashmere goats (Capra hircus). Goat S6K1 cDNA was 2,272 bp and include an open reading frame (ORF) of 1,578 bp, corresponding to a polypeptide of 525 amino acids, and a 694-residue 3' noncoding sequence with a polyadenylation signal at nucleotides 2,218 to 2,223. The relative abundance of S6K1 mRNA was measured by real-time PCR in 6 tissues, and p70S6K expression was examined by immunohistochemistry in heart and testis. The phosphorylation of p70S6K is regulated by mitogen-activated protein kinase (MAPK) signaling in fetal fibroblasts. PMID:25049885

Manlin, Wu; Wenlei, Bao; Xiyan, Hao; Xu, Zheng; Yanfeng, Wang; Zhigang, Wang

2013-08-01

63

Molecular Characterization and Expression Analysis of S6K1 in Cashmere Goats (Capra hircus)  

PubMed Central

p70 ribosomal S6 kinase (p70S6K) can integrate nutrient and growth factor signals to promote cell growth and survival. We report our molecular characterization of the complementary DNA (cDNA) that encodes the goat p70S6K gene 40S ribosomal S6 kinase 1 (S6K1) (GenBank accession GU144017) and its 3? noncoding sequence in Inner Mongolia Cashmere goats (Capra hircus). Goat S6K1 cDNA was 2,272 bp and include an open reading frame (ORF) of 1,578 bp, corresponding to a polypeptide of 525 amino acids, and a 694-residue 3? noncoding sequence with a polyadenylation signal at nucleotides 2,218 to 2,223. The relative abundance of S6K1 mRNA was measured by real-time PCR in 6 tissues, and p70S6K expression was examined by immunohistochemistry in heart and testis. The phosphorylation of p70S6K is regulated by mitogen-activated protein kinase (MAPK) signaling in fetal fibroblasts. PMID:25049885

Manlin, Wu; Wenlei, Bao; Xiyan, Hao; Xu, Zheng; Yanfeng, Wang; Zhigang, Wang

2013-01-01

64

S6 kinase inactivation impairs growth and translational target phosphorylation in muscle cells maintaining proper regulation of protein turnover.  

PubMed

A defect in protein turnover underlies multiple forms of cell atrophy. Since S6 kinase (S6K)-deficient cells are small and display a blunted response to nutrient and growth factor availability, we have hypothesized that mutant cell atrophy may be triggered by a change in global protein synthesis. By using mouse genetics and pharmacological inhibitors targeting the mammalian target of rapamycin (mTOR)/S6K pathway, here we evaluate the control of translational target phosphorylation and protein turnover by the mTOR/S6K pathway in skeletal muscle and liver tissues. The phosphorylation of ribosomal protein S6 (rpS6), eukaryotic initiation factor-4B (eIF4B), and eukaryotic elongation factor-2 (eEF2) is predominantly regulated by mTOR in muscle cells. Conversely, in liver, the MAPK and phosphatidylinositol 3-kinase pathways also play an important role, suggesting a tissue-specific control. S6K deletion in muscle mimics the effect of the mTOR inhibitor rapamycin on rpS6 and eIF4B phosphorylation without affecting eEF2 phosphorylation. To gain insight on the functional consequences of these modifications, methionine incorporation and polysomal distribution were assessed in muscle cells. Rates and rapamycin sensitivity of global translation initiation are not altered in S6K-deficient muscle cells. In addition, two major pathways of protein degradation, autophagy and expression of the muscle-specific atrophy-related E3 ubiquitin ligases, are not affected by S6K deletion. Our results do not support a role for global translational control in the growth defect due to S6K deletion, suggesting specific modes of growth control and translational target regulation downstream of mTOR. PMID:17494629

Mieulet, Virginie; Roceri, Mila; Espeillac, Catherine; Sotiropoulos, Athanassia; Ohanna, Mickael; Oorschot, Viola; Klumperman, Judith; Sandri, Marco; Pende, Mario

2007-08-01

65

The TORC1/P70S6K and TORC1/4EBP1 signaling pathways have a stronger contribution on skeletal muscle growth than MAPK/ERK in an early vertebrate: Differential involvement of the IGF system and atrogenes.  

PubMed

Knowledge about the underlying mechanisms, particularly the signaling pathways that account for muscle growth in vivo in early vertebrates is still scarce. Fish (Paralichthys adspersus) were fasted for 3weeks to induce a catabolic period of strong muscle atrophy. Subsequently, fish were refed for 2weeks to induce compensatory muscle hypertrophy. During refeeding, the fish were treated daily with either rapamycin (TORC blocker), PD98059 (MEK blocker), or PBS (V; vehicle), or were untreated (C; control). Rapamycin and PD98059 differentially impaired muscle cellularity in vivo, growth performance, and the expression of growth-related genes, and the inhibition of TORC1 had a greater impact on fish muscle growth than the inhibition of MAPK. Blocking TORC1 inhibited the phosphorylation of P70S6K and 4EBP1, two downstream components activated by TORC1, thus affecting protein contents in muscle. Concomitantly, the gene expression in muscle of igf-1, 2 and igfbp-4, 5 was down-regulated while the expression of atrogin-1, murf-1, and igfbp-2, 3 was up-regulated. Muscle hypertrophy was abolished and muscle atrophy was promoted, which finally affected body weight. TORC2 complex was not affected by rapamycin. On the other hand, the PD98059 treatment triggered ERK inactivation, a downstream component activated by MEK. mRNA contents of igf-1 in muscle were down-regulated, and muscle hypertrophy was partially impaired. The present study provides the first direct data on the in vivo contribution of TORC1/P70S6K, TORC1/4EBP1, and MAPK/ERK signaling pathways in the skeletal muscle of an earlier vertebrate, and highlights the transcendental role of TORC1 in growth from the cellular to organism level. PMID:25449137

Fuentes, Eduardo N; Einarsdottir, Ingibjörg Eir; Paredes, Rodolfo; Hidalgo, Christian; Valdes, Juan Antonio; Björnsson, Björn Thrandur; Molina, Alfredo

2015-01-01

66

Involvement of 90-kuD ribosomal S6 kinase in collagen type I expression in rat hepatic fibrosis  

Microsoft Academic Search

AIM: To investigate the relationship between 90-kuD ribosomal S6 kinase (p90RSK) and collagen type ? expression during the development of hepatic fibrosis in vivo and in vitro . METHODS: Rat hepatic fibrosis was induced by intraperitoneal injection of dimethylnitrosamine. The protein expression and cell location of p90RSK and their relationship with collagen type ? were determined by co-immunofluoresence and confocal

Miao-Fang Yang; Jun Xie; Xiao-Yi Gu; Xiao-Hua Zhang; Andrew K Davey; Shuang-Jie Zhang; Ji-Ping Wang; Ren-Min Zhu

2009-01-01

67

Control of Paip1-Eukayrotic Translation Initiation Factor 3 Interaction by Amino Acids through S6 Kinase  

PubMed Central

The simultaneous interaction of poly(A)-binding protein (PABP) with eukaryotic translation initiation factor 4G (eIF4G) and the mRNA 3? poly(A) tail promotes translation initiation. We previously showed that the interaction of PABP-interacting protein 1 (Paip1) with PABP and eukaryotic translation initiation factor 3 (eIF3; via the eIF3g subunit) further stimulates translation. Here, we demonstrate that the interaction of eIF3 with Paip1 is regulated by amino acids through the mTORC1 signaling pathway. The Paip1-eIF3 interaction is impaired by the mTORC1 inhibitors, rapamycin and PP242. We show that ribosomal protein S6 kinases 1 and 2 (S6K1/2) promote the interaction of eIF3 with Paip1. The enhancement of Paip1-eIF3 interaction by amino acids is abrogated by an S6K inhibitor or shRNA against S6K1/2. S6K1 interacts with eIF3f and, in vitro, phosphorylates eIF3. Finally, we show that S6K inhibition leads to a reduction in translation by Paip1. We propose that S6K1/2 phosphorylate eIF3 to stimulate Paip1-eIF3 interaction and consequent translation initiation. Taken together, these data demonstrate that eIF3 is a new translation target of the mTOR/S6K pathway. PMID:24396066

Martineau, Yvan; Wang, Xiaoshan; Alain, Tommy; Petroulakis, Emmanuel; Shahbazian, David; Fabre, Bertrand; Bousquet-Dubouch, Marie-Pierre; Monsarrat, Bernard

2014-01-01

68

Stimulation of ribosomal protein S6 kinase activity by pp60/sup v-src/ or by serum: dissociation from phorbol ester-stimulated activity  

SciTech Connect

Ribosomal protein S6 kinase activity was measured in lysates prepared from serum-deprived chicken embryo fibroblasts (CEF) treated for various times with phorbol 12-myristate 13-acetate (PMA). Maximal activity was observed within 15 min, and it declined to the initial level by 4 hr. Incubation of these cells with PMA 4-60 hr after the initial treatment did not result in an additional increase in S6 protein kinase activity. These results are consistent with down-regulation of the PMA receptor, protein kinase C, and the dependence of PMA-stimulated S6 kinase activity on this enzyme. Long-term pretreatment of CEF with PMA only partially attenuated the stimulation of the S6 protein kinase activity by serum or by expression of the Rous sarcoma virus transforming gene product, pp60/sup v-src/. A similar protein kinase activity also was stimulated in cells treated with cycloheximide or sodium vanadate. Pretreatment with PMA had little effect on this response. These data indicate that it is likely that there are at least two mechanisms through which S6 kinase activity can be regulated, one of which apparently utilizes protein kinase C whereas the other(s) does not. Additional experiments show PMA-stimulated glucose transport was not attenuated by long-term incubation with phorbol ester, suggesting that another mechanism, which is not dependent on the presence of protein kinase C, maintains this response after the proposed down-regulation of the PMA receptor.

Blenis, J.; Erikson, R.L.

1986-03-01

69

Structural Diversity of the Active N-Terminal Kinase Domain of p90 Ribosomal S6 Kinase 2  

SciTech Connect

The p90 ribosomal protein kinase 2 (RSK2) is a highly expressed Ser/Thr kinase activated by growth factors and is involved in cancer cell proliferation and tumor promoter-induced cell transformation. RSK2 possesses two non-identical kinase domains, and the structure of its N-terminal domain (NTD), which is responsible for phosphorylation of a variety of substrates, is unknown. The crystal structure of the NTD RSK2 was determined at 1.8 {angstrom} resolution in complex with AMP-PNP. The N-terminal kinase domain adopted a unique active conformation showing a significant structural diversity of the kinase domain compared to other kinases. The NTD RSK2 possesses a three-stranded {beta}B-sheet inserted in the N-terminal lobe, resulting in displacement of the {alpha}C-helix and disruption of the Lys-Glu interaction, classifying the kinase conformation as inactive. The purified protein was phosphorylated at Ser227 in the T-activation loop and exhibited in vitro kinase activity. A key characteristic is the appearance of a new contact between Lys216 ({beta}B-sheet) and the {beta}-phosphate of AMP-PNP. Mutation of this lysine to alanine impaired both NTDs in vitro and full length RSK2 ex vivo activity, emphasizing the importance of this interaction. Even though the N-terminal lobe undergoes structural re-arrangement, it possesses an intact hydrophobic groove formed between the {alpha}C-helix, the {beta}4-strand, and the {beta}B-sheet junction, which is occupied by the N-terminal tail. The presence of a unique {beta}B-sheet insert in the N-lobe suggests a different type of activation mechanism for RSK2.

Malakhova, Margarita; Kurinov, Igor; Liu, Kangdong; Zheng, Duo; D'Angelo, Igor; Shim, Jung-Hyun; Steinman, Valerie; Bode, Ann M.; Dong, Zigang; (Cornell); (CLS); (UMM); (CSB)

2010-10-08

70

Mechanism of Sustained Activation of Ribosomal S6 Kinase (RSK) and ERK by Kaposi Sarcoma-associated Herpesvirus ORF45 MULTIPROTEINCOMPLEXESRETAINACTIVEPHOSPHORYLATEDERKANDRSKAND PROTECTTHEMFROMDEPHOSPHORYLATION  

Microsoft Academic Search

As obligate intracellular parasites, viruses exploit diverse cel- lular signaling machineries, including the mitogen-activated protein-kinase pathway, during their infections. We have dem- onstrated previously that the open reading frame 45 (ORF45) of Kaposi sarcoma-associated herpesvirus interacts with p90 ribo- somal S6 kinases (RSKs) and strongly stimulates their kinase activities (Kuang, E., Tang, Q., Maul, G. G., and Zhu, F. (2008)

Ersheng Kuang; Fayi Wu; Fanxiu Zhu

71

Involvement of Heterogeneous Ribonucleoprotein F in the Regulation of Cell Proliferation via the Mammalian Target of Rapamycin/S6 Kinase 2 Pathway  

PubMed Central

The S6 kinases (S6Ks) have been linked to a number of cellular processes, including translation, insulin metabolism, cell survival, and RNA splicing. Signaling via the phosphotidylinositol 3-kinase and mammalian target of rapamycin (mTOR) pathways is critical in regulating the activity and subcellular localization of S6Ks. To date, nuclear functions of both S6K isoforms, S6K1 and S6K2, are not well understood. To better understand S6K nuclear roles, we employed affinity purification of S6Ks from nuclear preparations followed by mass spectrometry analysis for the identification of novel binding partners. In this study, we report that in contrast to S6K1, the S6K2 isoform specifically associates with a number of RNA-binding proteins, including heterogeneous ribonucleoproteins (hnRNPs). We focused on studying the mechanism and physiological relevance of the S6K2 interaction with hnRNP F/H. Interestingly, the S6K2-hnRNP F/H interaction was not affected by mitogenic stimulation, whereas mTOR binding to hnRNP F/H was induced by serum stimulation. In addition, we define a new role of hnRNP F in driving cell proliferation, which could be partially attenuated by rapamycin treatment. S6K2-driven cell proliferation, on the other hand, could be blocked by small interfering RNA-mediated down-regulation of hnRNP F. These results demonstrate that the specific interaction between mTOR and S6K2 with hnRNPs is implicated in the regulation of cell proliferation. PMID:20308064

Goh, Eddy T. H.; Pardo, Olivier E.; Michael, Nicholas; Niewiarowski, Andrew; Totty, Nick; Volkova, Dariya; Tsaneva, Irina R.; Seckl, Michael J.; Gout, Ivan

2010-01-01

72

Phosphorylation of KIBRA by the extracellular signal-regulated kinase (ERK)-ribosomal S6 kinase (RSK) cascade modulates cell proliferation and migration.  

PubMed

In mammals, KIBRA is defined as a memory performance-associated protein. The physiological function and regulation of KIBRA in non-neuronal cells are much less understood. Recent studies have identified KIBRA as a novel regulator of the Hippo signaling pathway, which plays a critical role in tumorigenesis by inhibiting cell proliferation and promoting apoptosis. We recently reported that KIBRA is phosphorylated by the mitotic kinases Aurora and cyclin-dependent kinase 1 during mitosis. In this current study, we show that KIBRA is also phosphorylated by the ERK (extracellular signal-regulated kinases)-RSK (p90 ribosomal S6 kinases) cascade. We demonstrated that ERK1/2 phosphorylate KIBRA at Ser(548) in cells as well as in vitro. Moreover, we found that RSK1/2 specifically phosphorylates KIBRA at two highly conserved sites (Thr(929) and Ser(947)) in vitro and in cells. RSK-mediated phosphorylation is required for KIBRA binding to RSK1, but not RSK2. Surprisingly, KIBRA knockdown impaired cell migration and proliferation in breast cancer cells. By using inducible-expression cell lines, we further show that phospho-regulation of KIBRA by ERK1/2 and RSK1/2 is required for proper cell proliferation and RSK-mediated phosphorylation also modulates KIBRA's migratory activity in MDA-MB-231 breast cancer cells. Our findings uncover unexpected results and a new mechanism through which KIBRA regulates cell migration and proliferation. PMID:24269383

Yang, Shuping; Ji, Ming; Zhang, Lin; Chen, Yuanhong; Wennmann, Dirk Oliver; Kremerskothen, Joachim; Dong, Jixin

2014-02-01

73

Effects of contraction and insulin on protein synthesis, AMP-activated protein kinase and phosphorylation state of translation factors in rat skeletal muscle  

Microsoft Academic Search

In rat epitrochlearis skeletal muscle, contraction inhibited the basal and insulin-stimulated rates of protein synthesis by\\u000a 75 and 70%, respectively, while increasing adenosine monophosphate-activated protein kinase (AMPK) activity. Insulin, on the\\u000a other hand, stimulated protein synthesis (by 30%) and increased p70 ribosomal protein S6 kinase (p70S6K) Thr389, 40S ribosomal\\u000a protein S6 (rpS6) Ser235\\/236, rpS6 Ser240\\/244 and eukaryotic initiation factor-4E-binding protein-1

Lisa Miranda; Sandrine Horman; Isabelle De Potter; Louis Hue; Jørgen Jensen; Mark H. Rider

2008-01-01

74

Psk1, an AGC kinase family member in fission yeast, is directly phosphorylated and controlled by TORC1 and functions as S6 kinase  

PubMed Central

Summary Target of rapamycin (TOR), an evolutionarily conserved serine/threonine protein kinase, plays pivotal roles in several important cellular processes in eukaryotes. In the fission yeast Schizosaccharomyces pombe, TOR complex 1 (TORC1), which includes Tor2 as a catalytic subunit, manages the switch between cell proliferation and differentiation by sensing nutrient availability. However, little is known about the direct target of TORC1 that plays key roles in nutrient-dependent TORC1 signaling in fission yeast. Here we report that in fission yeast, three AGC kinase family members, named Psk1, Sck1 and Sck2, which exhibit high homology with human S6K1, are phosphorylated under nutrient-rich conditions and are dephosphorylated by starvation conditions. Among these, Psk1 is necessary for phosphorylation of ribosomal protein S6. Furthermore, Psk1 phosphorylation is regulated by TORC1 in nutrient-dependent and rapamycin-sensitive manners in vivo. Three conserved regulatory motifs (the activation loop, the hydrophobic and the turn motifs) in Psk1 are phosphorylated and these modifications are required for Psk1 activity. In particular, phosphorylation of the hydrophobic motif is catalyzed by TORC1 in vivo and in vitro. Ksg1, a homolog of PDK1, is also important for Psk1 phosphorylation in the activation loop and for its activity. The TORC1 components Pop3, Toc1 and Tco89, are dispensable for Psk1 regulation, but disruption of pop3+ causes an increase in the sensitivity of TORC1 to rapamycin. Taken together, these results provide convincing evidence that TORC1/Psk1/Rps6 constitutes a nutrient-dependent signaling pathway in fission yeast. PMID:22976295

Nakashima, Akio; Otsubo, Yoko; Yamashita, Akira; Sato, Tatsuhiro; Yamamoto, Masayuki; Tamanoi, Fuyuhiko

2012-01-01

75

Psk1, an AGC kinase family member in fission yeast, is directly phosphorylated and controlled by TORC1 and functions as S6 kinase.  

PubMed

Target of rapamycin (TOR), an evolutionarily conserved serine/threonine protein kinase, plays pivotal roles in several important cellular processes in eukaryotes. In the fission yeast Schizosaccharomyces pombe, TOR complex 1 (TORC1), which includes Tor2 as a catalytic subunit, manages the switch between cell proliferation and differentiation by sensing nutrient availability. However, little is known about the direct target of TORC1 that plays key roles in nutrient-dependent TORC1 signaling in fission yeast. Here we report that in fission yeast, three AGC kinase family members, named Psk1, Sck1 and Sck2, which exhibit high homology with human S6K1, are phosphorylated under nutrient-rich conditions and are dephosphorylated by starvation conditions. Among these, Psk1 is necessary for phosphorylation of ribosomal protein S6. Furthermore, Psk1 phosphorylation is regulated by TORC1 in nutrient-dependent and rapamycin-sensitive manners in vivo. Three conserved regulatory motifs (the activation loop, the hydrophobic and the turn motifs) in Psk1 are phosphorylated and these modifications are required for Psk1 activity. In particular, phosphorylation of the hydrophobic motif is catalyzed by TORC1 in vivo and in vitro. Ksg1, a homolog of PDK1, is also important for Psk1 phosphorylation in the activation loop and for its activity. The TORC1 components Pop3, Toc1 and Tco89, are dispensable for Psk1 regulation, but disruption of pop3(+) causes an increase in the sensitivity of TORC1 to rapamycin. Taken together, these results provide convincing evidence that TORC1/Psk1/Rps6 constitutes a nutrient-dependent signaling pathway in fission yeast. PMID:22976295

Nakashima, Akio; Otsubo, Yoko; Yamashita, Akira; Sato, Tatsuhiro; Yamamoto, Masayuki; Tamanoi, Fuyuhiko

2012-12-01

76

p90 ribosomal S6 kinase 3 contributes to cardiac insufficiency in ?-tropomyosin Glu180Gly transgenic mice.  

PubMed

Myocardial interstitial fibrosis is an important contributor to the development of heart failure. Type 3 p90 ribosomal S6 kinase (RSK3) was recently shown to be required for concentric myocyte hypertrophy under in vivo pathological conditions. However, the role of RSK family members in myocardial fibrosis remains uninvestigated. Transgenic expression of ?-tropomyosin containing a Glu180Gly mutation (TM180) in mice of a mixed C57BL/6:FVB/N background induces a cardiomyopathy characterized by a small left ventricle, interstitial fibrosis, and diminished systolic and diastolic function. Using this mouse model, we now show that RSK3 is required for the induction of interstitial fibrosis in vivo. TM180 transgenic mice were crossed to RSK3 constitutive knockout (RSK3(-/-)) mice. Although RSK3 knockout did not affect myocyte growth, the decreased cardiac function and mild pulmonary edema associated with the TM180 transgene were attenuated by RSK3 knockout. The improved cardiac function was consistent with reduced interstitial fibrosis in the TM180;RSK3(-/-) mice as shown by histology and gene expression analysis, including the decreased expression of collagens. The specific inhibition of RSK3 should be considered as a potential novel therapeutic strategy for improving cardiac function and the prevention of sudden cardiac death in diseases in which interstitial fibrosis contributes to the development of heart failure. PMID:23913705

Passariello, Catherine L; Gayanilo, Marjorie; Kritzer, Michael D; Thakur, Hrishikesh; Cozacov, Zoharit; Rusconi, Francesca; Wieczorek, David; Sanders, Michael; Li, Jinliang; Kapiloff, Michael S

2013-10-01

77

Yeast 3-phosphoinositide-dependent protein kinase-1 (PDK1) orthologs Pkh1-3 differentially regulate phosphorylation of protein kinase A (PKA) and the protein kinase B (PKB)/S6K ortholog Sch9.  

PubMed

Pkh1, -2, and -3 are the yeast orthologs of mammalian 3-phosphoinositide-dependent protein kinase-1 (PDK1). Although essential for viability, their functioning remains poorly understood. Sch9, the yeast protein kinase B and/or S6K ortholog, has been identified as one of their targets. We now have shown that in vitro interaction of Pkh1 and Sch9 depends on the hydrophobic PDK1-interacting fragment pocket in Pkh1 and requires the complementary hydrophobic motif in Sch9. We demonstrated that Pkh1 phosphorylates Sch9 both in vitro and in vivo on its PDK1 site and that this phosphorylation is essential for a wild type cell size. In vivo phosphorylation on this site disappeared during nitrogen deprivation and rapidly increased again upon nitrogen resupplementation. In addition, we have shown here for the first time that the PDK1 site in protein kinase A is phosphorylated by Pkh1 in vitro, that this phosphorylation is Pkh-dependent in vivo and occurs during or shortly after synthesis of the protein kinase A catalytic subunits. Mutagenesis of the PDK1 site in Tpk1 abolished binding of the regulatory subunit and cAMP dependence. As opposed to PDK1 site phosphorylation of Sch9, phosphorylation of the PDK1 site in Tpk1 was not regulated by nitrogen availability. These results bring new insight into the control and prevalence of PDK1 site phosphorylation in yeast by Pkh protein kinases. PMID:21531713

Voordeckers, Karin; Kimpe, Marlies; Haesendonckx, Steven; Louwet, Wendy; Versele, Matthias; Thevelein, Johan M

2011-06-24

78

Growth-promoting effect of a protein-free hemodialysate used in situations of hypoxia and for tissue repair as measured via stimulation of S6-kinase.  

PubMed

Solcoseryl is the low-molecular weight fraction of calf blood as manufactured by counterflow dialysis. This hemodialysate (HD) is in clinical use in situations involving hypoxia and for the normalization of tissue repair. The influence of the HD on ZR-75 cells was tested. These cells preferably express receptors for Epidermal Growth Factor (EGF)/Transforming Growth Factor alpha (TGF-alpha) or Somatomedin C (SMC = insulin like growth factor I resp. ILA-I) and react upon stimulation by enhancement of their S6-kinase activity, the latter being a prerequisite for growth. The functional presence of one or several of these peptide growth factors should therefore reflect in a stimulation of S6-kinase activity. PMID:1418056

Fabbro, D; Imber, R; Huggel, K; Baschong, W

1992-07-01

79

Focal adhesion kinase is required for IGF-I-mediated growth of skeletal muscle cells via a TSC2/mTOR/S6K1-associated pathway  

PubMed Central

Focal adhesion kinase (FAK) is an attachment complex protein associated with the regulation of muscle mass through as-of-yet unclear mechanisms. We tested whether FAK is functionally important for muscle hypertrophy, with the hypothesis that FAK knockdown (FAK-KD) would impede cell growth associated with a trophic stimulus. C2C12 skeletal muscle cells harboring FAK-targeted (FAK-KD) or scrambled (SCR) shRNA were created using lentiviral transfection techniques. Both FAK-KD and SCR myotubes were incubated for 24 h with IGF-I (10 ng/ml), and additional SCR cells (±IGF-1) were incubated with a FAK kinase inhibitor before assay of cell growth. Muscle protein synthesis (MPS) and putative FAK signaling mechanisms (immunoblotting and coimmunoprecipitation) were assessed. IGF-I-induced increases in myotube width (+41 ± 7% vs. non-IGF-I-treated) and total protein (+44 ± 6%) were, after 24 h, attenuated in FAK-KD cells, whereas MPS was suppressed in FAK-KD vs. SCR after 4 h. These blunted responses were associated with attenuated IGF-I-induced FAK Tyr397 phosphorylation and markedly suppressed phosphorylation of tuberous sclerosis complex 2 (TSC2) and critical downstream mTOR signaling (ribosomal S6 kinase, eIF4F assembly) in FAK shRNA cells (all P < 0.05 vs. IGF-I-treated SCR cells). However, binding of FAK to TSC2 or its phosphatase Shp-2 was not affected by IGF-I or cell phenotype. Finally, FAK-KD-mediated suppression of cell growth was recapitulated by direct inhibition of FAK kinase activity in SCR cells. We conclude that FAK is required for IGF-I-induced muscle hypertrophy, signaling through a TSC2/mTOR/S6K1-dependent pathway via means requiring the kinase activity of FAK but not altered FAK-TSC2 or FAK-Shp-2 binding. PMID:23695213

Crossland, Hannah; Kazi, Abid A.; Lang, Charles H.; Timmons, James A.; Pierre, Philippe; Wilkinson, Daniel J.; Smith, Kenneth; Szewczyk, Nathaniel J.

2013-01-01

80

Activation of p90 ribosomal S6 kinase by ORF45 of Kaposi's sarcoma-associated herpesvirus and its role in viral lytic replication.  

PubMed

The extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase (MAPK) pathway is essential for infection by a variety of viruses. The p90 ribosomal S6 kinases (RSKs) are direct substrates of ERK and functional mediators of ERK MAPK signaling, but their roles in viral infection have never been examined. We demonstrate that ORF45 of Kaposi's sarcoma-associated herpesvirus (KSHV) interacts with RSK1 and RSK2 and strongly stimulates their kinase activities. The activation of RSK by ORF45 is correlated with ERK activation but does not require MEK. We further demonstrate that RSK1/RSK2 is activated during KSHV primary infection and reactivation from latency; a subset of RSK1/RSK2 is present in the viral replication compartment in the nucleus. Depletion of RSK1/RSK2 by small interfering RNA or the specific inhibitor BI-D1870 suppresses KSHV lytic gene expression and progeny virion production, suggesting an essential role of RSK1/RSK2 in KSHV lytic replication. PMID:18057234

Kuang, Ersheng; Tang, Qiyi; Maul, Gerd G; Zhu, Fanxiu

2008-02-01

81

Insulin Activates RSK (p90 Ribosomal S6 Kinase) to Trigger a New Negative Feedback Loop That Regulates Insulin Signaling for Glucose Metabolism*  

PubMed Central

We previously demonstrated that the mTORC1/S6K1 pathway is activated by insulin and nutrient overload (e.g. amino acids (AA)), which leads to the inhibition of the PI3K/Akt pathway via the inhibitory serine phosphorylation of IRS-1, notably on serine 1101 (Ser-1101). However, even in the absence of AA, insulin can still promote IRS-1 Ser-1101 phosphorylation by other kinases that remain to be fully characterized. Here, we describe a new negative regulator of IRS-1, the p90 ribosomal S6 kinase (RSK). Computational analyses revealed that Ser-1101 within IRS-1 falls into the consensus motif of RSK. Moreover, recombinant RSK phosphorylated IRS-1 C-terminal fragment on Ser-1101, which was prevented by mutations of this site or when a kinase-inactive mutant of RSK was used. Using antibodies directed toward the phosphorylation sites located in the activation segment of RSK (Ser-221 or Ser-380), we found that insulin activates RSK in L6 myocytes in the absence of AA overload. Inhibition of RSK using either the pharmacological inhibitor BI-D1870 or after adenoviral expression of a dominant negative RSK1 mutant (RSK1-DN) showed that RSK selectively phosphorylates IRS-1 on Ser-1101. Accordingly, expression of the RSK1-DN mutant in L6 myocytes and FAO hepatic cells improved insulin action on glucose uptake and glucose production, respectively. Furthermore, RSK1 inhibition prevented insulin resistance in L6 myocytes chronically exposed to high glucose and high insulin. These results show that RSK is a novel regulator of insulin signaling and glucose metabolism and a potential mediator of insulin resistance, notably through the negative phosphorylation of IRS-1 on Ser-1101. PMID:24036112

Smadja-Lamère, Nicolas; Shum, Michael; Déléris, Paul; Roux, Philippe P.; Abe, Jun-Ichi; Marette, André

2013-01-01

82

RhoA Kinase (Rock) and p90 Ribosomal S6 Kinase (p90Rsk) phosphorylation of the sodium hydrogen exchanger (NHE1) is required for lysophosphatidic acid-induced transport, cytoskeletal organization and migration.  

PubMed

The sodium hydrogen exchanger isoform one (NHE1) plays a critical role coordinating asymmetric events at the leading edge of migrating cells and is regulated by a number of phosphorylation events influencing both the ion transport and cytoskeletal anchoring required for directed migration. Lysophosphatidic acid (LPA) activation of RhoA kinase (Rock) and the Ras-ERK growth factor pathway induces cytoskeletal reorganization, activates NHE1 and induces an increase in cell motility. We report that both Rock I and II stoichiometrically phosphorylate NHE1 at threonine 653 in vitro using mass spectrometry and reconstituted kinase assays. In fibroblasts expressing NHE1 alanine mutants for either Rock (T653A) or ribosomal S6 kinase (Rsk; S703A) we show that each site is partially responsible for the LPA-induced increase in transport activity while NHE1 phosphorylation by either Rock or Rsk at their respective site is sufficient for LPA stimulated stress fiber formation and migration. Furthermore, mutation of either T653 or S703 leads to a higher basal pH level and a significantly higher proliferation rate. Our results identify the direct phosphorylation of NHE1 by Rock and suggest that both RhoA and Ras pathways mediate NHE1-dependent ion transport and migration in fibroblasts. PMID:25578862

Wallert, Mark A; Hammes, Daniel; Nguyen, Tony; Kiefer, Lea; Berthelsen, Nick; Kern, Andrew; Anderson-Tiege, Kristina; Shabb, John B; Muhonen, Wallace W; Grove, Bryon D; Provost, Joseph J

2015-03-01

83

Activation of AMP-activated protein kinase inhibits protein synthesis associated with hypertrophy in the cardiac myocyte.  

PubMed

A necessary mediator of cardiac myocyte enlargement is protein synthesis, which is controlled at the levels of both translation initiation and elongation. Eukaryotic elongation factor-2 (eEF2) mediates the translocation step of peptide-chain elongation and is inhibited through phosphorylation by eEF2 kinase. In addition, p70S6 kinase can regulate protein synthesis by phosphorylating eEF2 kinase or via phosphorylation of ribosomal protein S6. We have recently shown that eEF2 kinase is also controlled by phosphorylation by AMP-activated protein kinase (AMPK), a key regulator of cellular energy homeostasis. Moreover, the mammalian target of rapamycin has also been shown to be inhibited, indirectly, by AMPK, thus leading to the inhibition of p70S6 kinase. Although AMPK activation has been shown to modulate protein synthesis, it is unknown whether AMPK could also be a regulator of cardiac hypertrophic growth. Therefore, we investigated the role of AMPK activation in regulating protein synthesis during both phenylephrine- and Akt-induced cardiac hypertrophy. Metformin and 5-aminoimidazole-4-carboxamide 1-beta-D-ribofuranoside were used to activate AMPK in neonatal rat cardiac myocytes. Activation of AMPK significantly decreased protein synthesis induced by phenylephrine treatment or by expression of constitutively active Akt. Activation of AMPK also resulted in decreased p70S6 kinase phosphorylation and increased phosphorylation of eEF2, suggesting that inhibition of protein synthesis involves the eEF2 kinase/eEF2 axis and/or the p70S6 kinase pathway. Together, our data suggest that the inhibition of protein synthesis by pharmacological activation of AMPK may be a key regulatory mechanism by which hypertrophic growth can be controlled. PMID:15159410

Chan, Anita Y M; Soltys, Carrie-Lynn M; Young, Martin E; Proud, Christopher G; Dyck, Jason R B

2004-07-30

84

Haloperidol Regulates the State of Phosphorylation of Ribosomal Protein S6 via Activation of PKA and Phosphorylation of DARPP-32  

PubMed Central

Administration of typical antipsychotic drugs, such as haloperidol, promotes cAMP-dependent signaling in the medium spiny neurons (MSNs) of the striatum. In this study, we have examined the effect of haloperidol on the state of phosphorylation of the ribosomal protein S6 (rpS6), a component of the small 40S ribosomal subunit. We found that haloperidol increases the phosphorylation of rpS6 at the dual site Ser235/236, which is involved in the regulation of mRNA translation. This effect was exerted in the MSNs of the indirect pathway, which express specifically dopamine D2 receptors (D2Rs) and adenosine A2 receptors (A2ARs). The effect of haloperidol was decreased by blockade of A2ARs or by genetic attenuation of the G?olf protein, which couples A2ARs to activation of adenylyl cyclase. Moreover, stimulation of cAMP-dependent protein kinase A (PKA) increased Ser235/236 phosphorylation in cultured striatal neurons. The ability of haloperidol to promote rpS6 phosphorylation was abolished in knock-in mice deficient for PKA activation of the protein phosphatase-1 inhibitor, dopamine- and cAMP-regulated phosphoprotein of 32?kDa. In contrast, pharmacological or genetic inactivation of p70 rpS6 kinase 1, or extracellular signal-regulated kinases did not affect haloperidol-induced rpS6 phosphorylation. These results identify PKA as a major rpS6 kinase in neuronal cells and suggest that regulation of protein synthesis through rpS6 may be a potential target of antipsychotic drugs. PMID:21814187

Valjent, Emmanuel; Bertran-Gonzalez, Jesus; Bowling, Heather; Lopez, Sébastien; Santini, Emanuela; Matamales, Miriam; Bonito-Oliva, Alessandra; Hervé, Denis; Hoeffer, Charles; Klann, Eric; Girault, Jean-Antoine; Fisone, Gilberto

2011-01-01

85

ATM kinase is a master switch for the ?Np63? phosphorylation/degradation in human head and neck squamous cell carcinoma cells upon DNA damage  

PubMed Central

We previously found that the pro-apoptotic DNA damaging agent, cisplatin, mediated the proteasome-dependent degradation of ?Np63? associated with its increased phosphorylated status. Since ?Np63? usually plays an opposite role to p53 and TAp63 in human cancers, we tested the notion that phosphorylation events induced by DNA damage would affect the protein degradation of ?Np63? in HNSCC cells upon cisplatin exposure. We found that ?Np63? is phosphorylated in the time-dependent fashion at the following positions: S385, T397 and S466, which were surrounded by recognition motifs for ATM, CDK2 and p70s6K kinases, respectively. We showed that chemical agents or siRNA inhibiting the activity of ATM, CDK2 and p70s6K kinases blocked degradation of ?Np63? in HNSCC cells after cisplatin exposure. Site-specific mutagenesis of ?Np63? residues targeted for phosphorylation by ATM, CDK2 or p70s6k led to dramatic modulation of ?Np63? degradation. Finally, we demonstrated that the ?Np63? protein is a target for direct in vitro phosphorylation by ATM, CDK2 or p70s6K. Our results implicate specific kinases, and target phosphorylation sites in the degradation of ?Np63? following DNA damage. PMID:18769144

Huang, Yiping; Sen, Tanusree; Nagpal, Jatin; Upadhyay, Sunil; Trink, Barry; Ratovitski, Edward; Sidransky, David

2011-01-01

86

Mechanism of sustained activation of ribosomal S6 kinase (RSK) and ERK by kaposi sarcoma-associated herpesvirus ORF45: multiprotein complexes retain active phosphorylated ERK AND RSK and protect them from dephosphorylation.  

PubMed

As obligate intracellular parasites, viruses exploit diverse cellular signaling machineries, including the mitogen-activated protein-kinase pathway, during their infections. We have demonstrated previously that the open reading frame 45 (ORF45) of Kaposi sarcoma-associated herpesvirus interacts with p90 ribosomal S6 kinases (RSKs) and strongly stimulates their kinase activities ( Kuang, E., Tang, Q., Maul, G. G., and Zhu, F. (2008) J. Virol. 82, 1838-1850 ). Here, we define the mechanism by which ORF45 activates RSKs. We demonstrated that binding of ORF45 to RSK increases the association of extracellular signal-regulated kinase (ERK) with RSK, such that ORF45, RSK, and ERK formed high molecular mass protein complexes. We further demonstrated that the complexes shielded active pERK and pRSK from dephosphorylation. As a result, the complex-associated RSK and ERK were activated and sustained at high levels. Finally, we provide evidence that this mechanism contributes to the sustained activation of ERK and RSK in Kaposi sarcoma-associated herpesvirus lytic replication. PMID:19304659

Kuang, Ersheng; Wu, Fayi; Zhu, Fanxiu

2009-05-15

87

Proteasome inhibition-induced p38 MAPK/ERK signaling regulates autophagy and apoptosis through the dual phosphorylation of glycogen synthase kinase 3{beta}  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer MG132 induces the phosphorylation of GSK3{beta}{sup Ser9} and, to a lesser extent, of GSK3{beta}{sup Thr390}. Black-Right-Pointing-Pointer MG132 induces dephosphorylation of p70S6K{sup Thr389} and phosphorylation of p70S6K{sup Thr421/Ser424}. Black-Right-Pointing-Pointer Inactivation of p38 dephosphorylates GSK3{beta}{sup Ser9} and phosphorylates GSK3{beta}{sup Thr390}. Black-Right-Pointing-Pointer Inactivation of p38 phosphorylates p70S6K{sup Thr389} and increases the phosphorylation of p70S6K{sup Thr421/Ser424}. Black-Right-Pointing-Pointer Inactivation of p38 decreases autophagy and increases apoptosis induced by MG132. -- Abstract: Proteasome inhibition is a promising approach for cancer treatment; however, the underlying mechanisms involved have not been fully elucidated. Here, we show that proteasome inhibition-induced p38 mitogen-activated protein kinase regulates autophagy and apoptosis by modulating the phosphorylation status of glycogen synthase kinase 3{beta} (GSK3{beta}) and 70 kDa ribosomal S6 kinase (p70S6K). The treatment of MDA-MB-231 cells with MG132 induced endoplasmic reticulum stress through the induction of ATF6a, PERK phosphorylation, and CHOP, and apoptosis through the cleavage of Bax and procaspase-3. MG132 caused the phosphorylation of GSK3{beta} at Ser{sup 9} and, to a lesser extent, Thr{sup 390}, the dephosphorylation of p70S6K at Thr{sup 389}, and the phosphorylation of p70S6K at Thr{sup 421} and Ser{sup 424}. The specific p38 inhibitor SB203080 reduced the p-GSK3{beta}{sup Ser9} and autophagy through the phosphorylation of p70S6K{sup Thr389}; however, it augmented the levels of p-ERK, p-GSK3{beta}{sup Thr390}, and p-70S6K{sup Thr421/Ser424} induced by MG132, and increased apoptotic cell death. The GSK inhibitor SB216763, but not lithium, inhibited the MG132-induced phosphorylation of p38, and the downstream signaling pathway was consistent with that in SB203580-treated cells. Taken together, our data show that proteasome inhibition regulates p38/GSK{sup Ser9}/p70S6K{sup Thr380} and ERK/GSK3{beta}{sup Thr390}/p70S6K{sup Thr421/Ser424} kinase signaling, which is involved in cell survival and cell death.

Choi, Cheol-Hee [Research Center for Resistant Cells, Chosun University, Seosuk-dong, Dong-gu, Gwangju 501-759 (Korea, Republic of) [Research Center for Resistant Cells, Chosun University, Seosuk-dong, Dong-gu, Gwangju 501-759 (Korea, Republic of); Department of Pharmacology, College of Medicine, Chosun University, Seosuk-dong, Dong-gu, Gwangju 501-759 (Korea, Republic of); Lee, Byung-Hoon [College of Pharmacy and Multiscreening Center for Drug Development, Seoul National University, Seoul 151-742 (Korea, Republic of)] [College of Pharmacy and Multiscreening Center for Drug Development, Seoul National University, Seoul 151-742 (Korea, Republic of); Ahn, Sang-Gun [Department of Pathology, College of Dentistry, Chosun University, Gwangju 501-759 (Korea, Republic of)] [Department of Pathology, College of Dentistry, Chosun University, Gwangju 501-759 (Korea, Republic of); Oh, Seon-Hee, E-mail: oshccw@hanmail.net [Research Center for Resistant Cells, Chosun University, Seosuk-dong, Dong-gu, Gwangju 501-759 (Korea, Republic of)] [Research Center for Resistant Cells, Chosun University, Seosuk-dong, Dong-gu, Gwangju 501-759 (Korea, Republic of)

2012-02-24

88

Phosphorylation of eukaryotic translation initiation factor 4B (EIF4B) by open reading frame 45/p90 ribosomal S6 kinase (ORF45/RSK) signaling axis facilitates protein translation during Kaposi sarcoma-associated herpesvirus (KSHV) lytic replication.  

PubMed

Open reading frame 45 (ORF45) of Kaposi sarcoma-associated herpesvirus (KSHV) causes sustained activation of p90 ribosomal S6 kinase (RSK), which is crucial for KSHV lytic replication, but the exact functional roles remain to be determined. To characterize the biological consequence of persistent RSK activation by ORF45, we screened known cellular substrates of RSK. We found that ORF45 induced phosphorylation of eukaryotic translation initiation factor 4B (eIF4B), increased its assembly into translation initiation complex, and subsequently facilitated protein translation. The ORF45/RSK-mediated eIF4B phosphorylation was distinguishable from that caused by the canonical AKT/mammalian target of rapamycin/ribosomal S6 kinase and MEK/ERK/RSK pathways because it was resistant to both rapamycin (an mammalian target of rapamycin inhibitor) and U1026 (an MEK inhibitor). The rapamycin and U1026 doubly insensitive eIF4B phosphorylation was induced during KSHV reactivation but was abolished if either ORF45 or RSK1/2 were ablated by siRNA, a pattern that is correlated with reduced lytic gene expression as we observed previously. Ectopic expression of eIF4B but not its phosphorylation-deficient mutant form increased KSHV lytic gene expression and production of progeny viruses. Together, these results indicated that ORF45/RSK axis-induced eIF4B phosphorylation is involved in translational regulation and is required for optimal KSHV lytic replication. PMID:21994950

Kuang, Ersheng; Fu, Bishi; Liang, Qiming; Myoung, Jinjong; Zhu, Fanxiu

2011-12-01

89

Insights into the inhibition of the p90 ribosomal S6 kinase (RSK) by the flavonol glycoside SL010 from the 1.5 Å crystal structure of the N-terminal domain of RSK2 with bound inhibitor  

PubMed Central

The p90 ribosomal S6 family of kinases (RSK) are potential drug targets, due to their involvement in cancer and other pathologies. There are currently only two known selective inhibitors of RSK, but the basis for selectivity is not known. One of these inhibitors is a naturally occurring kaempferol-?-L-diacetylrhamnoside, SL0101. Here, we report the crystal structure of the complex of the N-terminal kinase domain of the RSK2 isoform with SL0101 at 1.5 Å resolution. The refined atomic model reveals unprecedented structural reorganization of the protein moiety, as compared to the nucleotide-bound form. The entire N-lobe, the hinge region and the ?D-helix undergo dramatic conformational changes resulting in a rearrangement of the nucleotide binding site with concomitant formation of a highly hydrophobic pocket spatially suited to accommodate SL0101. These unexpected results will be invaluable in further optimization of the SL0101 scaffold as a promising lead for a novel class of kinase inhibitors. PMID:22846040

Utepbergenov, Darkhan; Derewenda, Urszula; Olekhnovich, Natalya; Szukalska, Gabriela; Banerjee, Budhaditya; Hilinski, Michael K.; Lannigan, Deborah A.; Stukenberg, P. Todd; Derewenda, Zygmunt S.

2012-01-01

90

TGF? enforces activation of eukaryotic elongation factor-2 (eEF2) via inactivation of eEF2 kinase by p90 ribosomal S6 kinase (p90Rsk) to induce mesangial cell hypertrophy  

PubMed Central

eEF2 phosphorylation is under tight control to maintain mRNA translation elongation. We report that TGF? activates eEF2 by decreasing eEF2 phosphorylation and simultaneously increasing eEF2 kinase phosphorylation. Remarkably, inhibition of Erk1/2 blocked the TGF?-induced dephosphorylation and phosphorylation of eEF2 and eEF2 kinase. TGF? increased phosphorylation of p90Rsk in an Erk1/2-dependent manner. Inactive p90Rsk reversed TGF?-inhibited phosphorylation of eEF2 and suppressed eEF2 kinase activity. Finally, inactive p90Rsk significantly attenuated TGF?-induced protein synthesis and hypertrophy of mesangial cells. These results present the first evidence that TGF? utilizes the two layered kinase module Erk/p90Rsk to activate eEF2 for increased protein synthesis during cellular hypertrophy. PMID:20837011

Das, Falguni; Ghosh-Choudhury, Nandini; Kasinath, Balakuntalam S.; Choudhury, Goutam Ghosh

2010-01-01

91

TGF? enforces activation of eukaryotic elongation factor-2 (eEF2) via inactivation of eEF2 kinase by p90 ribosomal S6 kinase (p90Rsk) to induce mesangial cell hypertrophy.  

PubMed

eEF2 phosphorylation is under tight control to maintain mRNA translation elongation. We report that TGF? activates eEF2 by decreasing eEF2 phosphorylation and simultaneously increasing eEF2 kinase phosphorylation. Remarkably, inhibition of Erk1/2 blocked the TGF?-induced dephosphorylation and phosphorylation of eEF2 and eEF2 kinase. TGF? increased phosphorylation of p90Rsk in an Erk1/2-dependent manner. Inactive p90Rsk reversed TGF?-inhibited phosphorylation of eEF2 and suppressed eEF2 kinase activity. Finally, inactive p90Rsk significantly attenuated TGF?-induced protein synthesis and hypertrophy of mesangial cells. These results present the first evidence that TGF? utilizes the two layered kinase module Erk/p90Rsk to activate eEF2 for increased protein synthesis during cellular hypertrophy. PMID:20837011

Das, Falguni; Ghosh-Choudhury, Nandini; Kasinath, Balakuntalam S; Choudhury, Goutam Ghosh

2010-10-01

92

Pharmacogenet Genomics . Author manuscript Association of sirolimus adverse effects with m-TOR, p70S6K or Raptor  

E-print Network

-induced adverse events in kidney transplant recipients. This study included a first group of 113 patients.0370). Sirolimus trough levels were also associated with an increased risk for cutaneous adverse events (OR = = = 1 ; Graft Rejection ; Haplotypes ; Humans ; Immunosuppressive Agents ; adverse effects ; Kidney ; drug

Paris-Sud XI, Université de

93

Notch-induced T cell development requires phosphoinositide-dependent kinase 1.  

PubMed

Phosphoinositide-dependent kinase l (PDK1) phosphorylates and activates multiple AGC serine kinases, including protein kinase B (PKB), p70Ribosomal S6 kinase (S6K) and p90Ribosomal S6 kinase (RSK). PDK1 is required for thymocyte differentiation and proliferation, and herein, we explore the molecular basis for these essential functions of PDK1 in T lymphocyte development. A key finding is that PDK1 is required for the expression of key nutrient receptors in T cell progenitors: CD71 the transferrin receptor and CD98 a subunit of L-amino acid transporters. PDK1 is also essential for Notch-mediated trophic and proliferative responses in thymocytes. A PDK1 mutant PDK1 L155E, which supports activation of PKB but no other AGC kinases, can restore CD71 and CD98 expression in pre-T cells and restore thymocyte differentiation. However, PDK1 L155E is insufficient for thymocyte proliferation. The role of PDK1 in thymus development thus extends beyond its ability to regulate PKB. In addition, PDK1 phosphorylation of AGC kinases such as S6K and RSK is also necessary for thymocyte development. PMID:17599070

Kelly, April P; Finlay, David K; Hinton, Heather J; Clarke, Rosie G; Fiorini, Emma; Radtke, Freddy; Cantrell, Doreen A

2007-07-25

94

Effects of contraction and insulin on protein synthesis, AMP-activated protein kinase and phosphorylation state of translation factors in rat skeletal muscle.  

PubMed

In rat epitrochlearis skeletal muscle, contraction inhibited the basal and insulin-stimulated rates of protein synthesis by 75 and 70%, respectively, while increasing adenosine monophosphate-activated protein kinase (AMPK) activity. Insulin, on the other hand, stimulated protein synthesis (by 30%) and increased p70 ribosomal protein S6 kinase (p70S6K) Thr389, 40S ribosomal protein S6 (rpS6) Ser235/236, rpS6 Ser240/244 and eukaryotic initiation factor-4E-binding protein-1 (4E-BP1) Thr37/46 phosphorylation over basal values. Electrical stimulation had no effect on mammalian target of rapamycin complex 1 (mTORC1) signalling, as reflected by the lack of reduction in basal levels of p70S6K, rpS6 Ser235/236, rpS6 Ser240/244 and 4E-BP1 phosphorylation, but did antagonize mTORC1 signalling after stimulation of the pathway by insulin. Eukaryotic elongation factor-2 (eEF2) Thr56 phosphorylation increased rapidly on electrical stimulation reaching a maximum at 1 min, whereas AMPK Thr172 phosphorylation slowly increased to reach threefold after 30 min. Eukaryotic elongation factor-2 kinase (eEF2K) was not activated after 30 min of contraction when AMPK was activated. This could not be explained by the expression of a tissue-specific isoform of eEF2K in skeletal muscle lacking the Ser398 AMPK phosphorylation site. Therefore, in this skeletal muscle system, the contraction-induced inhibition of protein synthesis could not be attributed to a reduction in mTORC1 signalling but could be due to an increase in eEF2 phosphorylation independent of AMPK activation. PMID:17957382

Miranda, Lisa; Horman, Sandrine; De Potter, Isabelle; Hue, Louis; Jensen, Jørgen; Rider, Mark H

2008-03-01

95

Development of Organometallic S6K1 Inhibitors  

PubMed Central

Aberrant activation of S6 kinase 1 (S6K1) is found in many diseases, including diabetes, aging, and cancer. We developed ATP competitive organometallic kinase inhibitors, EM5 and FL772, which are inspired by the structure of the pan-kinase inhibitor staurosporine, to specifically inhibit S6K1 using a strategy previously used to target other kinases. Biochemical data demonstrate that EM5 and FL772 inhibit the kinase with IC50 value in the low nanomolar range at 100 ?M ATP and that the more potent FL772 compound has a greater than 100-fold specificity over S6K2. The crystal structures of S6K1 bound to staurosporine, EM5, and FL772 reveal that the EM5 and FL772 inhibitors bind in the ATP binding pocket and make S6K1-specific contacts, resulting in changes to the p-loop, ?C helix, and ?D helix when compared to the staurosporine-bound structure. Cellular data reveal that FL772 is able to inhibit S6K phosphorylation in yeast cells. Together, these studies demonstrate that potent, selective, and cell permeable S6K1 inhibitors can be prepared and provide a scaffold for future development of S6K inhibitors with possible therapeutic applications. PMID:25356520

Feng, Li; Salami, Jemilat; Barber-Rotenberg, Julie S.; Domsic, John; Reyes-Uribe, Patricia; Liu, Haiying; Dang, Weiwei; Berger, Shelley L.; Villanueva, Jessie; Meggers, Eric; Marmorstein, Ronen

2014-01-01

96

Development of Organometallic S6K1 Inhibitors.  

PubMed

Aberrant activation of S6 kinase 1 (S6K1) is found in many diseases, including diabetes, aging, and cancer. We developed ATP competitive organometallic kinase inhibitors, EM5 and FL772, which are inspired by the structure of the pan-kinase inhibitor staurosporine, to specifically inhibit S6K1 using a strategy previously used to target other kinases. Biochemical data demonstrate that EM5 and FL772 inhibit the kinase with IC50 value in the low nanomolar range at 100 ?M ATP and that the more potent FL772 compound has a greater than 100-fold specificity over S6K2. The crystal structures of S6K1 bound to staurosporine, EM5, and FL772 reveal that the EM5 and FL772 inhibitors bind in the ATP binding pocket and make S6K1-specific contacts, resulting in changes to the p-loop, ?C helix, and ?D helix when compared to the staurosporine-bound structure. Cellular data reveal that FL772 is able to inhibit S6K phosphorylation in yeast cells. Together, these studies demonstrate that potent, selective, and cell permeable S6K1 inhibitors can be prepared and provide a scaffold for future development of S6K inhibitors with possible therapeutic applications. PMID:25356520

Qin, Jie; Rajaratnam, Rajathees; Feng, Li; Salami, Jemilat; Barber-Rotenberg, Julie S; Domsic, John; Reyes-Uribe, Patricia; Liu, Haiying; Dang, Weiwei; Berger, Shelley L; Villanueva, Jessie; Meggers, Eric; Marmorstein, Ronen

2014-11-13

97

The N-terminal region of p27 inhibits HIF-1? protein translation in ribosomal protein S6-dependent manner by regulating PHLPP-Ras-ERK-p90RSK axis  

PubMed Central

P27 was identified as a tumor suppressor nearly two decades, being implicated in cell-cycle control, differentiation, senescence, apoptosis and motility. Our present study, for the first time to the best of our knowledge, revealed a potential role of p27 in inhibiting S6-mediated hypoxia-inducible factor-1? (HIF-1?) protein translation, which contributed to the protection from environmental carcinogen (sodium arsenite)-induced cell transformation. Our findings showed that depletion of p27 expression by knockout and knockdown approaches efficiently enhanced S6 phosphorylation in arsenite response via overactivating Ras/Raf/MEK/ERK pathway, which consequently resulted in the stimulation of p90RSK (90?kDa ribosomal S6 kinase), a direct kinase for S6 phosphorylation. Although PI3K/AKT pathway was also involved in S6 activation, blocking AKT and p70S6K activation did not attenuate arsenite-induced S6 activation in p27?/? cells, suggesting p27 specifically targeted Ras/ERK pathway rather than PI3K/AKT pathway for inhibition of S6 activation in response to arsenite exposure. Further functional studies found that p27 had a negative role in cell transformation induced by chronic low-dose arsentie exposure. Mechanistic investigations showed that HIF-1? translation was upregulated in p27-deficient cells in an S6 phosphorylation-dependent manner and functioned as a driving force in arsenite-induced cell transformation. Knockdown of HIF-1? efficiently reversed arsenite-induced cell transformation in p27-depleted cells. Taken together, our findings provided strong evidence showing that by targeting Ras/ERK pathway, p27 provided a negative control over HIF-1? protein synthesis in an S6-dependent manner, and abrogated arsenite-induced cell transformation via downregulation of HIF-1? translation. PMID:25412313

Zhang, D; Liu, J; Mi, X; Liang, Y; Li, J; Huang, C

2014-01-01

98

Gastrin Induces Sodium-Hydrogen Exchanger 3 Phosphorylation and mTOR Activation via a Phosphoinositide 3-Kinase-/Protein Kinase C-Dependent but AKT-Independent Pathway in Renal Proximal Tubule Cells Derived From a Normotensive Male Human  

PubMed Central

Gastrin is natriuretic, but its renal molecular targets and signal transduction pathways are not fully known. In this study, we confirmed the existence of CCKBR (a gastrin receptor) in male human renal proximal tubule cells and discovered that gastrin induced S6 phosphorylation, a downstream component of the phosphatidylinositol 3 kinase (PI3 kinase)-mammalian target of rapamycin pathway. Gastrin also increased the phosphorylation of sodium-hydrogen exchanger 3 (NHE3) at serine 552, caused its internalization, and decreased its expression at the cell surface and NHE activity. The phosphorylation of NHE3 and S6 was dependent on PI3 kinases because it was blocked by 2 different PI3-kinase inhibitors, wortmannin and LY294,002. The phosphorylation of NHE3 and S6 was not affected by the protein kinase A inhibitor H-89 but was blocked by a pan-PKC (chelerythrine) and a conventional PKC (cPKC) inhibitor (Gö6976) (10 ?M) and an intracellular calcium chelator, 1,2-bis-(o-aminophenoxy)ethane-N,N,N?,N?-tetraacetic acid, tetra(acetoxymethyl)-ester, suggesting the importance of cPKC and intracellular calcium in the gastrin signaling pathway. The cPKC involved was probably PKC? because it was phosphorylated by gastrin. The gastrin-mediated phosphorylation of NHE3, S6, and PKC? was via phospholipase C because it was blocked by a phospholipase C inhibitor, U73122 (10 ?M). The phosphorylation (activation) of AKT, which is usually upstream of mammalian target of rapamycin in the classic PI3 kinase-AKT-p70S6K signaling pathway, was not affected, suggesting that the gastrin-induced phosphorylation of NHE3 and S6 is dependent on both PI3 kinase and PKC? but not AKT. PMID:23275470

2013-01-01

99

Removal of S6K1 and S6K2 Leads to Divergent Alterations in Learning, Memory, and Synaptic Plasticity  

ERIC Educational Resources Information Center

Protein synthesis is required for the expression of enduring memories and long-lasting synaptic plasticity. During cellular proliferation and growth, S6 kinases (S6Ks) are activated and coordinate the synthesis of de novo proteins. We hypothesized that protein synthesis mediated by S6Ks is critical for the manifestation of learning, memory, and…

Antion, Marcia D.; Merhav, Maayan; Hoeffer, Charles A.; Reis, Gerald; Kozma, Sara C.; Thomas, George; Schuman Erin M.; Rosenblum, Kobi; Klann, Eric

2008-01-01

100

IL-8-INDUCED NEUTROPHIL CHEMOTAXIS IS MEDIATED BY JANUS KINASE 3 (JAK3)  

PubMed Central

Janus kinase 3 (JAK3) is a non-receptor tyrosine kinase vital to the regulation of T-cells. We report that JAK3 is a mediator of IL-8 stimulation of a different class of hematopoietic relevant cells: human neutrophils. IL-8 induced a time- and concentration-dependent activation of JAK3 activity in neutrophils and differentiated HL-60 leukemic cells. JAK3 was more robustly activated by IL-8 than other kinases: p70S6K, mTOR, MAPK or PKC. JAK3 silencing severely inhibited IL-8-mediated chemotaxis. Thus, IL-8 stimulates chemotaxis through a mechanism mediated by JAK3. Further, JAK3 activity and chemotaxis were inhibited by the flavonoid apigenin (4,5,7-trihydroxyflavone) at ~5 nM IC50. These new findings lay the basis for understanding the molecular mechanism of cell migration as it relates to neutrophil-mediated chronic inflammatory processes. PMID:21095188

Henkels, Karen M.; Frondorf, Kathleen; Gonzalez-Mejia, M. Elba; Doseff, Andrea L.; Gomez-Cambronero, Julian

2010-01-01

101

Generation of clinical grade dendritic cells with capacity to produce biologically active IL12p70  

Microsoft Academic Search

BACKGROUND: For optimal T cell activation it is desirable that dendritic cells (DCs) display peptides within MHC molecules as signal 1, costimulatory molecules as signal 2 and, in addition, produce IL-12p70 as signal 3. IL-12p70 polarizes T cell responses towards CD4+ T helper 1 cells, which then support the development of CD8+ cytotoxic T lymphocytes. We therefore developed new maturation

Anke Zobywalski; Miran Javorovic; Bernhard Frankenberger; Heike Pohla; Elisabeth Kremmer; Iris Bigalke; Dolores J Schendel

2007-01-01

102

Nijmegen breakage syndrome fibroblasts expressing the C-terminal truncated NBN(p70) protein undergo p38/MK2-dependent premature senescence.  

PubMed

Fibroblasts from the progeroid Nijmegen breakage syndrome that express a truncated version of the nibrin protein (NBN(p70)) undergo premature senescence and have an enlarged morphology with high levels of senescence-associated ?-galactosidase, although they do not have F-actin stress fibres. Growth of these fibroblasts in the continuous presence of p38 inhibitors resulted in a large increase in replicative capacity and changed the cellular morphology so that the cells resembled young normal fibroblasts. A similar effect was seen using an inhibitor of the p38 downstream effector kinase MK2. These data suggest that NBN(p70) expressing cells undergo a degree of stress-induced replicative senescence via p38/MK2 activation, potentially due to increased telomere dysfunction, that may play a role in the progeroid features seen in this syndrome. PMID:25214013

Davis, Terence; Tivey, Hannah S E; Brook, Amy J C; Kipling, David

2015-02-01

103

The mTOR effectors 4EBP1 and S6K2 are frequently coexpressed, and associated with a poor prognosis and endocrine resistance in breast cancer: a retrospective study including patients from the randomised Stockholm tamoxifen trials  

PubMed Central

Introduction mTOR and its downstream effectors the 4E-binding protein 1 (4EBP1) and the p70 ribosomal S6 kinases (S6K1 and S6K2) are frequently upregulated in breast cancer, and assumed to be driving forces in tumourigenesis, in close connection with oestrogen receptor (ER) networks. Here, we investigated these factors as clinical markers in five different cohorts of breast cancer patients. Methods The prognostic significance of 4EBP1, S6K1 and S6K2 mRNA expression was assessed with real-time PCR in 93 tumours from the treatment randomised Stockholm trials, encompassing postmenopausal patients enrolled between 1976 and 1990. Three publicly available breast cancer cohorts were used to confirm the results. Furthermore, the predictive values of 4EBP1 and p4EBP1_S65 protein expression for both prognosis and endocrine treatment benefit were assessed by immunohistochemical analysis of 912 node-negative breast cancers from the Stockholm trials. Results S6K2 and 4EBP1 mRNA expression levels showed significant correlation and were associated with a poor outcome in all cohorts investigated. 4EBP1 protein was confirmed as an independent prognostic factor, especially in progesterone receptor (PgR)-expressing cancers. 4EBP1 protein expression was also associated with a poor response to endocrine treatment in the ER/PgR positive group. Cross-talk to genomic as well as non-genomic ER/PgR signalling may be involved and the results further support a combination of ER and mTOR signalling targeted therapies. Conclusion This study suggests S6K2 and 4EBP1 as important factors for breast tumourigenesis, interplaying with hormone receptor signalling. We propose S6K2 and 4EBP1 as new potential clinical markers for prognosis and endocrine therapy response in breast cancer. PMID:24131622

2013-01-01

104

RhoA-dependent murine prostate cancer cell proliferation and apoptosis: role of protein kinase Czeta.  

PubMed

We previously showed that RhoA played an important role in the proliferation of murine We prostate cancer (TRAMP) cells (P. M. Ghosh et al., Oncogene, 18: 4120-4130, 1999). Untransfected TRAMP cells as well as those expressing constitutively active RhoA (Q63L) mutant protein (Q63L cells) were highly proliferative. In contrast, TRAMP cells expressing dominant-negative RhoA (T19N) mutant protein (T19N cells) were slow growing. In this study, we showed, in addition, that T19N cells displayed reduced rates of apoptotic cell death in response to serum deprivation, compared with TRAMP and Q63L cells, and we studied the mechanisms of the effects of RhoA on TRAMP cell proliferation and apoptosis. Both proliferation and apoptosis of TRAMP and Q63L cells were dependent on the activation of phosphatidylinositol 3-kinase (PI3K). The ubiquitous mitogen-activated Ser/Thr kinase, p70S6 kinase, a downstream effector of PI3K, was overexpressed in TRAMP and Q63L cells. Another PI3K effector, the cell survival protein Akt, displayed increased activity in T19N cells, which did not express active RhoA, compared with TRAMP and Q63L cells. The atypical protein kinase C (PKC) isoform PKCzeta, which is downstream of PI3K, was activated in cells expressing active RhoA. In addition, expression of constitutively activated PKCzeta in TRAMP cells enhanced proliferation and p70S6 kinase phosphorylation, whereas the inhibition of PKCzeta activation resulted in activation of Akt and enhanced cell survival. Thus, the effects of RhoA on TRAMP cell proliferation and apoptosis may be mediated by PKCzeta. PMID:11980660

Ghosh, Paramita M; Bedolla, Roble; Mikhailova, Margharita; Kreisberg, Jeffrey I

2002-05-01

105

AMP-activated protein kinase pathway: a potential therapeutic target in cardiometabolic disease  

PubMed Central

AMPK (AMP-activated protein kinase) is a heterotrimetric enzyme that is expressed in many tissues, including the heart and vasculature, and plays a central role in the regulation of energy homoeostasis. It is activated in response to stresses that lead to an increase in the cellular AMP/ATP ratio caused either by inhibition of ATP production (i.e. anoxia or ischaemia) or by accelerating ATP consumption (i.e. muscle contraction or fasting). In the heart, AMPK activity increases during ischaemia and functions to sustain ATP, cardiac function and myocardial viability. There is increasing evidence that AMPK is implicated in the pathophysiology of cardiovascular and metabolic diseases. A principle mode of AMPK activation is phosphorylation by upstream kinases [e.g. LKB1 and CaMK (Ca2+/calmodulin-dependent protein kinase], which leads to direct effects on tissues and phosphorylation of various downstream kinases [e.g. eEF2 (eukaryotic elongation factor 2) kinase and p70 S6 kinase]. These upstream and downstream kinases of AMPK have fundamental roles in glucose metabolism, fatty acid oxidation, protein synthesis and tumour suppression; consequently, they have been implicated in cardiac ischaemia, arrhythmias and hypertrophy. Recent mechanistic studies have shown that AMPK has an important role in the mechanism of action of MF (metformin), TDZs (thiazolinediones) and statins. Increased understanding of the beneficial effects of AMPK activation provides the rationale for targeting AMPK in the development of new therapeutic strategies for cardiometabolic disease. PMID:19275766

Wong, Aaron K. F.; Howie, Jacqueline; Petrie, John R.; Lang, Chim C.

2009-01-01

106

Cardiac regulation by phosphoinositide 3-kinases and PTEN.  

PubMed

The diverse effects mediated by PI3K/PTEN (phosphoinositide 3-kinase/phosphatase and tensin homologue deleted on chromosome 10) signalling in the heart clearly support an important biological and pathophysiological role for this signalling cascade. PI3Ks are a family of evolutionarily conserved lipid kinases that mediate many cellular responses to physiological and pathophysiological stimuli. Class I PI3K can be activated by either receptor tyrosine kinase/cytokine receptor activation (class IA) or G-protein-coupled receptors (class IB), leading to the generation of phosphatidyl inositol (3,4,5)P3 and recruitment and activation of Akt/protein kinase B, 3'-phosphoinositide-dependent kinase-1 (PDK1), or monomeric G-proteins, and phosphorylation of a wide range of downstream targets including glycogen synthase kinase 3beta (GSK3beta), mTOR (mammalian target of rapamycin), p70S6 kinase, endothelial nitric oxide synthase, and several anti-apoptotic effectors. Class IA (PI3Kalpha, beta, and delta) and class IB (PI3Kgamma) PI3Ks mediate distinct phenotypes in the heart under negative control by the 3'-lipid phosphatase PTEN, which dephosphorylates PtdIns(3,4,5)P3 to generate PtdIns(4,5)P2. PI3Kalpha, PI3Kgamma, and PTEN are expressed in cardiomyocytes, fibroblasts, endothelial cells, and vascular smooth muscle cells, where they modulate cell survival, hypertrophy, contractility, metabolism, and mechanotransduction. The PI3K/PTEN signalling pathways are involved in a wide variety of diseases including myocardial hypertrophy and contractility, heart failure, and preconditioning. In this review, we discuss the signalling pathways mediated by PI3K class I isoforms and PTEN and their roles in cardiac structure and function. PMID:19147653

Oudit, Gavin Y; Penninger, Josef M

2009-05-01

107

Learned stressor resistance requires extracellular signal-regulated kinase in the prefrontal cortex  

PubMed Central

Behaviorally controllable stressors confer protection from the neurochemical and behavioral consequences of future uncontrollable stressors, a phenomenon termed “behavioral immunization”. Recent data implicate protein synthesis within the ventromedial prefrontal cortex (mPFC) as critical to behavioral immunization. Adult, male Sprague-Dawley rats were exposed to a series of controllable tailshocks and 1 week later to uncontrollable tailshocks, followed 24 h later by social exploration and shuttlebox escape tests. To test the involvement of N-methyl-D-aspartate receptors (NMDARs) and the extracellular signal-regulated kinase (ERK) cascade in behavioral immunization, either D-AP5 or the MEK inhibitor U0126 was injected to the prelimbic (PL) or infralimbic (IL) mPFC prior to controllable stress exposure. Phosphorylated ERK and P70S6K, regulators of transcription and translation, were quantified by Western blot or immunohistochemistry after controllable or uncontrollable tailshocks. Prior controllable stress prevented the social exploration and shuttlebox performance deficits caused by the later uncontrollable stressor, and this effect was blocked by injections of D-AP5 into mPFC. A significant increase in phosphorylated ERK1 and ERK2, but not P70S6K, occurred within the PL and IL in rats exposed to controllable stress, but not to uncontrollable stress. However, U0126 only prevented behavioral immunization when injected to the PL. We provide evidence that NMDAR and ERK dependent signaling within the PL region is required for behavioral immunization, a learned form of stressor resistance. PMID:25324750

Christianson, John P.; Flyer-Adams, Johanna G.; Drugan, Robert C.; Amat, Jose; Daut, Rachel A.; Foilb, Allison R.; Watkins, Linda R.; Maier, Steven F.

2014-01-01

108

IL23 Compensates for the Absence of IL12p70 and Is Essential for the IL17 Response during Tuberculosis but Is Dispensable for Protection and Antigen-Specific IFN Responses if IL12p70 Is Available1  

Microsoft Academic Search

IL-12p70 induced IFN- is required to control Mycobacterium tuberculosis growth; however, in the absence of IL-12p70, an IL-12p40-dependent pathway mediates induction of IFN- and initial bacteriostatic activity. IL-23 is an IL-12p40-dependent cytokine containing an IL-12p40 subunit covalently bound to a p19 subunit that is implicated in the induction of CD4 T cells associated with autoimmunity and inflammation. We show that

Shabaana A. Khader; John E. Pearl; Kaori Sakamoto; Leigh Gilmartin; Guy K. Bell; Dawn M. Jelley-Gibbs; Nico Ghilardi; Andrea M. Cooper

109

WNK1, the kinase mutated in an inherited high-blood-pressure syndrome, is a novel PKB (protein kinase B)/Akt substrate.  

PubMed

Recent evidence indicates that mutations in the gene encoding the WNK1 [with no K (lysine) protein kinase-1] results in an inherited hypertension syndrome called pseudohypoaldosteronism type II. The mechanisms by which WNK1 is regulated or the substrates it phosphorylates are currently unknown. We noticed that Thr-60 of WNK1, which lies N-terminal to the catalytic domain, is located within a PKB (protein kinase B) phosphorylation consensus sequence. We found that PKB phosphorylated WNK1 efficiently compared with known substrates, and both peptide map and mutational analysis revealed that the major PKB site of phosphorylation was Thr-60. Employing a phosphospecific Thr-60 WNK1 antibody, we demonstrated that IGF1 (insulin-like growth factor) stimulation of HEK-293 cells induced phosphorylation of endogenously expressed WNK1 at Thr-60. Consistent with PKB mediating this phosphorylation, inhibitors of PI 3-kinase (phosphoinositide 3-kinase; wortmannin and LY294002) but not inhibitors of mammalian target of rapamycin (rapamycin) or MEK1 (mitogen-activated protein kinase kinase-1) activation (PD184352), inhibited IGF1-induced phosphorylation of endogenous WNK1 at Thr-60. Moreover, IGF1-induced phosphorylation of endogenous WNK1 did not occur in PDK1-/- ES (embryonic stem) cells, in which PKB is not activated. In contrast, IGF1 still induced normal phosphorylation of WNK1 in PDK1(L155E/L155E) knock-in ES cells in which PKB, but not S6K (p70 ribosomal S6 kinase) or SGK1 (serum- and glucocorticoid-induced protein kinase 1), is activated. Our study provides strong pharmacological and genetic evidence that PKB mediates the phosphorylation of WNK1 at Thr-60 in vivo. We also performed experiments which suggest that the phosphorylation of WNK1 by PKB is not regulating its kinase activity or cellular localization directly. These results provide the first connection between the PI 3-kinase/PKB pathway and WNK1, suggesting a mechanism by which this pathway may influence blood pressure. PMID:14611643

Vitari, Alberto C; Deak, Maria; Collins, Barry J; Morrice, Nick; Prescott, Alan R; Phelan, Anne; Humphreys, Sian; Alessi, Dario R

2004-02-15

110

Differential expression of S6K2 dictates tissue-specific requirement for S6K1 in mediating aberrant mTORC1 signaling and tumorigenesis  

PubMed Central

The S6K1 and S6K2 kinases are considered important mTOR signaling effectors, yet their contribution to tumorigenesis remains unclear. Aberrant mTOR activation is a frequent event in cancer, that commonly results from heterozygous loss of PTEN. Here, we show for the first time a differential protein expression between S6K1 and S6K2 in both mouse and human tissues. Additionally, the inactivation of S6k1 in the context of Pten heterozygosity (Pten+/-) suggests a differential requirement for this protein across multiple tissues. This tissue-specificity appears to be governed by the relative protein expression of S6k2. Accordingly, we find that deletion of S6k1 markedly impairs Pten+/- mediated adrenal tumorigenesis, specifically due to low expression of S6k2. Concomitant observation of low S6K2 levels in the human adrenal gland supports the development of S6K1-inhibitors for treatment of PTEN loss driven pheochromocytoma. PMID:21444676

Nardella, Caterina; Lunardi, Andrea; Fedele, Giuseppe; Clohessy, John G.; Alimonti, Andrea; Kozma, Sara C.; Thomas, George; Loda, Massimo; Pandolfi, Pier Paolo

2011-01-01

111

Phosphorylation of Eukaryotic Translation Initiation Factor 4B (EIF4B) by Open Reading Frame 45/p90 Ribosomal S6  

E-print Network

Ribosomal S6 Kinase (ORF45/RSK) Signaling Axis Facilitates Protein Translation during Kaposi Sarcoma Research, Emeryville, California 94608-2916 Background: ORF45 of Kaposi sarcoma-associated herpesvirus (KSHV) causes sustained activation of p90 ribosomal S6 kinases (RSKs). Results: ORF45 increases

Ronquist, Fredrik

112

Interleukin-12 p40/p70 ratio and in vivo responsiveness to IFN-alpha treatment in chronic hepatitis C.  

PubMed

To evaluate the relationship between cytokine balance and responsiveness to interferon-alpha (IFN-alpha), we investigated the production of IFN-gamma, interleukin-10 (IL-10), IL-12 p70, and IL-12 p40 by peripheral blood mononuclear cell (PBMC) cultures from patients with chronic hepatitis C (CHC) before and after 1 year of IFN-alpha treatment. Before the therapy, responder (R) patients exhibited lower IFN-gamma release, higher IL-10 production, and higher values of the IL12 p40/p70 ratio compared with nonresponders (NR). Increased sensitivity to the effects of IL-12 and IL-10, as well as higher IL-12-dependent IFN-gamma secretion, were also found in the R subset. After IFN-alpha therapy, an increase in IFN-gamma production and a decrease in the IL-12 p40/p70 ratio were observed in R patients, whereas opposite results were obtained in the NR group. Finally, the therapy induced downregulation of IL-10 production and cell responsiveness to recombinant IL-12 in all patients. These findings imply that predominance of a T helper 2 (Th2) cytokine profile in CHC patients favors the beneficial effects of IFN-alpha, thus suggesting a therapeutic role for Th1-driven stimulation of immune response. The findings also stress the primary importance of the IL-12 p40 and p70 balance in the modulation of immune responses to hepatitis C virus (HCV). PMID:11506737

Piazzolla, G; Tortorella, C; Fiore, G; Fanelli, M; Pisconti, A; Antonaci, S

2001-07-01

113

Decorin activates AMPK, an energy sensor kinase, to induce autophagy in endothelial cells.  

PubMed

The highly conserved eukaryotic process of macroautophagy (autophagy) is a non-specific bulk-degradation program critical for maintaining proper cellular homeostasis, and for clearing aged and damaged organelles. This decision is inextricably dependent upon prevailing metabolic demands and energy requirements of the cell. Soluble monomeric decorin functions as a natural tumor repressor that antagonizes a variety of receptor tyrosine kinases. Recently, we discovered that decorin induces endothelial cell autophagy, downstream of VEGFR2. This process was wholly dependent upon Peg3, a decorin-inducible genomically imprinted tumor suppressor gene. However, the signaling cascades responsible have remained elusive. In this report we discovered that Vps34, a class III phosphoinositide kinase, is an upstream kinase required for Peg3 induction. Moreover, decorin triggered differential formation of Vps34/Beclin 1 complexes with concomitant dissolution of inhibitive Bcl-2/Beclin 1 complexes. Further, decorin inhibited anti-autophagic signaling via suppression of Akt/mTOR/p70S6K activity with the concurrent activation of pro-autophagic AMPK-mediated signaling cascades. Mechanistically, AMPK is downstream of VEGFR2 and inhibition of AMPK signaling abrogated decorin-evoked autophagy. Collectively, these findings hint at the complexity of the underlying molecular relays necessary for decorin-evoked endothelial cell autophagy and reveal important therapeutic targets for augmenting autophagy and combatting tumor angiogenesis. PMID:24472739

Goyal, Atul; Neill, Thomas; Owens, Rick T; Schaefer, Liliana; Iozzo, Renato V

2014-02-01

114

Reprint of: Decorin activates AMPK, an energy sensor kinase, to induce autophagy in endothelial cells.  

PubMed

The highly conserved eukaryotic process of macroautophagy (autophagy) is a non-specific bulk-degradation program critical for maintaining proper cellular homeostasis, and for clearing aged and damaged organelles. This decision is inextricably dependent upon prevailing metabolic demands and energy requirements of the cell. Soluble monomeric decorin functions as a natural tumor repressor that antagonizes a variety of receptor tyrosine kinases. Recently, we discovered that decorin induces endothelial cell autophagy, downstream of VEGFR2. This process was wholly dependent upon Peg3, a decorin-inducible genomically imprinted tumor suppressor gene. However, the signaling cascades responsible have remained elusive. In this report we discovered that Vps34, a class III phosphoinositide kinase, is an upstream kinase required for Peg3 induction. Moreover, decorin triggered differential formation of Vps34/Beclin 1 complexes with concomitant dissolution of inhibitive Bcl-2/Beclin 1 complexes. Further, decorin inhibited anti-autophagic signaling via suppression of Akt/mTOR/p70S6K activity with the concurrent activation of pro-autophagic AMPK-mediated signaling cascades. Mechanistically, AMPK is downstream of VEGFR2 and inhibition of AMPK signaling abrogated decorin-evoked autophagy. Collectively, these findings hint at the complexity of the underlying molecular relays necessary for decorin-evoked endothelial cell autophagy and reveal important therapeutic targets for augmenting autophagy and combatting tumor angiogenesis. PMID:24726292

Goyal, Atul; Neill, Thomas; Owens, Rick T; Schaefer, Liliana; Iozzo, Renato V

2014-04-01

115

Signaling from Akt to FRAP\\/TOR Targets both 4EBP and S6K in Drosophila melanogaster  

Microsoft Academic Search

The eIF4E-binding proteins (4E-BPs) interact with translation initiation factor 4E to inhibit translation. Their binding to eIF4E is reversed by phosphorylation of several key Ser\\/Thr residues. In Drosophila, S6 kinase (dS6K) and a single 4E-BP (d4E-BP) are phosphorylated via the insulin and target of rapamycin (TOR) signaling pathways. Although S6K phosphorylation is independent of phosphoinositide 3-OH kinase (PI3K) and serine\\/threonine

Mathieu Miron; Paul Lasko; Nahum Sonenberg

2003-01-01

116

Identification of Ki (Ku, p70/p80) autoantigens and analysis of anti-Ki autoantibody reactivity  

SciTech Connect

Anti-Ki (Ku, p70/p80) autoantibodies, named after the prototype patient Kikuta by Tojo et al., occur in approximately 10% of patients with SLE, often in association with anti-Sm autoantibodies. Anti-Ki sera specifically immunoprecipitated two protein antigens, Ki/sub 86/ (M/sub r/ 86,000) and Ki/sub 66/ (M/sub r/ 66,000), from radiolabeled cell extracts. The Ki system was found to be immunologically identical to the Ku system described by Mimori et al. and the p70/p80 system described by Reeves. The Ki primary in vitro translation products were identified and proved similar in size to the cellular antigens. The Ki antigens were purified from human spleen by immunoaffinity chromatography followed by SDS-PAGE. The purified Ki antigens proved to be closely related by amino acid composition, and did not appear to be phosphorylated, glycosylated, or associated with RNA. The Ki antigens were found to bind to DNA, in agreement with the observations on the Ku and p70/p80 antigens. They were found to be widely conserved in mammals and were coordinately expressed in all tissues tested.

Francoeur, A.M.; Peebles, C.L.; Gompper, P.T.; Tan, E.M.

1986-03-01

117

Hydrogen Sulfide Inhibits High Glucose-induced Matrix Protein Synthesis by Activating AMP-activated Protein Kinase in Renal Epithelial Cells*?  

PubMed Central

Hydrogen sulfide, a signaling gas, affects several cell functions. We hypothesized that hydrogen sulfide modulates high glucose (30 mm) stimulation of matrix protein synthesis in glomerular epithelial cells. High glucose stimulation of global protein synthesis, cellular hypertrophy, and matrix laminin and type IV collagen content was inhibited by sodium hydrosulfide (NaHS), an H2S donor. High glucose activation of mammalian target of rapamycin (mTOR) complex 1 (mTORC1), shown by phosphorylation of p70S6 kinase and 4E-BP1, was inhibited by NaHS. High glucose stimulated mTORC1 to promote key events in the initiation and elongation phases of mRNA translation: binding of eIF4A to eIF4G, reduction in PDCD4 expression and inhibition of its binding to eIF4A, eEF2 kinase phosphorylation, and dephosphorylation of eEF2; these events were inhibited by NaHS. The role of AMP-activated protein kinase (AMPK), an inhibitor of protein synthesis, was examined. NaHS dose-dependently stimulated AMPK phosphorylation and restored AMPK phosphorylation reduced by high glucose. Compound C, an AMPK inhibitor, abolished NaHS modulation of high glucose effect on events in mRNA translation as well as global and matrix protein synthesis. NaHS induction of AMPK phosphorylation was inhibited by siRNA for calmodulin kinase kinase ?, but not LKB1, upstream kinases for AMPK; STO-609, a calmodulin kinase kinase ? inhibitor, had the same effect. Renal cortical content of cystathionine ?-synthase and cystathionine ?-lyase, hydrogen sulfide-generating enzymes, was significantly reduced in mice with type 1 diabetes or type 2 diabetes, coinciding with renal hypertrophy and matrix accumulation. Hydrogen sulfide is a newly identified modulator of protein synthesis in the kidney, and reduction in its generation may contribute to kidney injury in diabetes. PMID:22158625

Lee, Hak Joo; Mariappan, Meenalakshmi M.; Feliers, Denis; Cavaglieri, Rita C.; Sataranatarajan, Kavithalakshmi; Abboud, Hanna E.; Choudhury, Goutam Ghosh; Kasinath, Balakuntalam S.

2012-01-01

118

Biological Effects of the Pim Kinase Inhibitor, SGI-1776, in Multiple Myeloma  

PubMed Central

Pim kinases are constitutively active serine/threonine/tyrosine kinases that are overexpressed in hematological malignancies such as multiple myeloma. Pim kinase substrates are involved in transcription, protein translation, cell proliferation, and apoptosis. SGI-1776 is a potent Pim kinase inhibitor that has proven to be cytotoxic to leukemia and lymphoma cells. Based on this background, we hypothesized that SGI-1776 treatment would result in myeloma cytotoxicity. To test this, myeloma cell lines and primary CD138+ cells from myeloma patients were treated with SGI-1776 in a dose- and time-dependent manner and effect on cell death and proliferation, induction of autophagy, as wells as changes in cell cycle profile were measured. SGI-1776 treatment resulted in limited apoptosis in cell lines (mean 30%) and CD138+ cells (<10%) as assessed by Annexin-V/PI. Limited effect was observed in cell cycle profile or growth in cell lines. However, DNA synthesis was decreased by 70% at 3 ?M (all time points) in U266 though this was not observed in MM.1S. In accordance, immunoblot analyses revealed no change in transcription (c-Myc and H3), or apoptotic (Bad) proteins that are substrates of Pim kinases. In contrast, autophagy, as assessed by acridine orange staining, was induced with SGI-1776 treatment in both cell lines (U266 25-70%; MM.1S 8-52%) and CD138+ cells (19-21%). Immunoblot analyses of autophagy LC3b marker and translation initiation proteins (phospho p70S6K and 4E-BP1) corroborated autophagy induction. These data indicate that SGI-1776 treatment in myeloma cell lines and CD138+ myeloma cells elicits its deleterious effects through inhibition of translation and induction of autophagy. PMID:23988451

Cervantes-Gomez, Fabiola; Chen, Lisa S.; Orlowski, Robert Z.; Gandhi, Varsha

2013-01-01

119

Molecular Characterization and Expression Analysis of Ribosomal Protein S6 Gene in the Cashmere Goat (Capra hircus)  

PubMed Central

Ribosomal protein (rp) S6 is the substrate of ribosomal protein S6K (S6 kinase) and is involved in protein synthesis by mTOR/S6K/S6 signaling pathway. Some S6 cDNA have been cloned in mammals in recent years but has not been identified in the goat. To facilitate such studies, we cloned the cDNA encoding Cashmere goat (Capra hircus) S6 (GenBank accession GU131122) and then detected mRNA expression in seven tissues by real time PCR and protein expression in testis tissue by immunohistochemisty. Sequence analysis indicated that the obtained goat S6 was a 808 bp product, including a 3? untranslated region of 58 bp and an open reading frame of 750 bp which predicted a protein of 249 amino acids. The predicted amino acid sequence was highly homologous to cattle, human, mouse and rat S6. Expression analysis indicated S6 mRNA was expressed extensively in detected tissues and S6 protein was expressed in testis tissue. PMID:25049753

Wenlei, Bao; Xiyan, Hao; Xu, Zheng; Yan, Liang; Yuhao, Chen; Yanfeng, Wang; Zhigang, Wang

2013-01-01

120

Molecular Characterization and Expression Analysis of Ribosomal Protein S6 Gene in the Cashmere Goat (Capra hircus).  

PubMed

Ribosomal protein (rp) S6 is the substrate of ribosomal protein S6K (S6 kinase) and is involved in protein synthesis by mTOR/S6K/S6 signaling pathway. Some S6 cDNA have been cloned in mammals in recent years but has not been identified in the goat. To facilitate such studies, we cloned the cDNA encoding Cashmere goat (Capra hircus) S6 (GenBank accession GU131122) and then detected mRNA expression in seven tissues by real time PCR and protein expression in testis tissue by immunohistochemisty. Sequence analysis indicated that the obtained goat S6 was a 808 bp product, including a 3' untranslated region of 58 bp and an open reading frame of 750 bp which predicted a protein of 249 amino acids. The predicted amino acid sequence was highly homologous to cattle, human, mouse and rat S6. Expression analysis indicated S6 mRNA was expressed extensively in detected tissues and S6 protein was expressed in testis tissue. PMID:25049753

Wenlei, Bao; Xiyan, Hao; Xu, Zheng; Yan, Liang; Yuhao, Chen; Yanfeng, Wang; Zhigang, Wang

2013-11-01

121

Estrogenic regulation of S6K1 expression creates a positive regulatory loop in control of breast cancer cell proliferation  

PubMed Central

The 40S ribosomal S6 kinase 1 (S6K1) is an important regulator of cell growth. Expression of S6K1 is often elevated in breast cancer cells. However, the transcriptional mechanism of S6K1 overexpression is not understood. In this report, we demonstrate that estrogen activates expression of S6K1 via Estrogen Receptor (ER) ? in ER-positive breast cancer cells. We also show that estrogen acts on the proximal promoter of the S6K1 gene in a mechanism involving the transcriptional factor GATA-3. Finally, we provide data that support the importance of estrogenic regulation of S6K1 expression in breast cancer cell proliferation. S6K1 directly phosphorylates and regulates ligand-independent activity of ER?, while ER? upregulates S6K1 expression. This S6K1-ER? relationship creates a positive feed-forward loop in control of breast cancer cell proliferation. Furthermore, the co-dependent association between S6K1 and ER? may be exploited in the development of targeted breast cancer therapies. PMID:22286763

Maruani, D. Myriam; Spiegel, Tirtza N.; Harris, Emily N.; Shachter, Avielle S.; Unger, Helen A.; Herrero-González, Sandra; Holz, Marina K.

2012-01-01

122

Sirtuin 1 Is a Key Regulator of the Interleukin-12 p70/Interleukin-23 Balance in Human Dendritic Cells*  

PubMed Central

Stimulation of human dendritic cells with the fungal surrogate zymosan produces IL-23 and a low amount of IL-12 p70. Trans-repression of il12a transcription, which encodes IL-12 p35 chain, by proteins of the Notch family and lysine deacetylation reactions have been reported as the underlying mechanisms, but a number of questions remain to be addressed. Zymosan produced the location of sirtuin 1 (SIRT1) to the nucleus, enhanced its association with the il12a promoter, increased the nuclear concentration of the SIRT1 co-substrate NAD+, and decreased chromatin accessibility in the nucleosome-1 of il12a, which contains a ?B-site. The involvement of deacetylation reactions in the inhibition of il12a transcription was supported by the absence of Ac-Lys-14-histone H3 in dendritic cells treated with zymosan upon coimmunoprecipitation of transducin-like enhancer of split. In contrast, we did not obtain evidence of a possible effect of SIRT1 through the deacetylation of c-Rel, the central element of the NF-?B family involved in il12a regulation. These data indicate that an enhancement of SIRT1 activity in response to phagocytic stimuli may reduce the accessibility of c-Rel to the il12a promoter and its transcriptional activation, thus regulating the IL-12 p70/IL-23 balance and modulating the ongoing immune response. PMID:22893703

Alvarez, Yolanda; Rodríguez, Mario; Municio, Cristina; Hugo, Etzel; Alonso, Sara; Ibarrola, Nieves; Fernández, Nieves; Crespo, Mariano Sánchez

2012-01-01

123

WELDING RESEARCH JANUARY 2004-S6  

E-print Network

WELDING RESEARCH JANUARY 2004-S6 ABSTRACT. The influence of microstruc- ture on the fatigue crack effects as the fatigue crack propa- gated from the base metal into the weld metal. The results by welding, so knowledge of the fatigue behavior of the weld is also important. Although data exist

DuPont, John N.

124

Berberine regulates AMP-activated protein kinase signaling pathways and inhibits colon tumorigenesis in mice.  

PubMed

Colorectal cancer, a leading cause of cancer death, has been linked to inflammation and obesity. Berberine, an isoquinoline alkaloid, possesses anti-inflammatory, anti-diabetes and anti-tumor properties. In the azoxymethane initiated and dextran sulfate sodium (AOM/DSS) promoted colorectal carcinogenesis mouse model, berberine treated mice showed a 60% reduction in tumor number (P?=?0.009), a 48% reduction in tumors <2?mm, (P?=?0.05); 94% reduction in tumors 2-4?mm, (P?=?0.001), and 100% reduction in tumors >4?mm (P?=?0.02) compared to vehicle treated mice. Berberine also decreased AOM/DSS induced Ki-67 and COX-2 expression. In vitro analysis showed that in addition to its anti-proliferation activity, berberine also induced apoptosis in colorectal cancer cell lines. Berberine activated AMP-activated protein kinase (AMPK), a major regulator of metabolic pathways, and inhibited mammalian target of rapamycin (mTOR), a downstream target of AMPK. Furthermore, 4E-binding protein-1 and p70 ribosomal S6 kinases, downstream targets of mTOR, were down regulated by berberine treatment. Berberine did not affect Liver kinase B1 (LKB1) activity or the mitogen-activated protein kinase pathway. Berberine inhibited Nuclear Factor kappa-B (NF-?B) activity, reduced the expression of cyclin D1 and survivin, induced phosphorylation of p53 and increased caspase-3 cleavage in vitro. Berberine inhibition of mTOR activity and p53 phosphorylation was found to be AMPK dependent, while inhibition NF-?B was AMPK independent. In vivo, berberine also activated AMPK, inhibited mTOR and p65 phosphorylation and activated caspase-3 cleavage. Our data suggests that berberine suppresses colon epithelial proliferation and tumorigenesis via AMPK dependent inhibition of mTOR activity and AMPK independent inhibition of NF-?B. © 2014 Wiley Periodicals, Inc. PMID:24838344

Li, Weidong; Hua, Baojin; Saud, Shakir M; Lin, Hongsheng; Hou, Wei; Matter, Matthias S; Jia, Libin; Colburn, Nancy H; Young, Matthew R

2014-05-17

125

Specificity of receptor tyrosine kinase signaling: Transient versus sustained extracellular signal-regulated kinase activation  

Microsoft Academic Search

A number of different intracellular signaling pathways have been shown to be activated by receptor tyrosine kinases. These activation events include the phosphoinositide 3-kinase, 70 kDa S6 kinase, mitogen-activated protein kinase (MAPK), phospholipase C-?, and the Jak\\/STAT pathways. The precise role of each of these pathways in cell signaling remains to be resolved, but studies on the differentiation of mammalian

C. J. Marshall

1995-01-01

126

A Polymorphism in the Coding Region of Il12b promotes IL-12p70 and IL-23 Heterodimer Formation  

PubMed Central

Interleukin (IL)-12 and IL-23 are heterodimeric cytokines involved in the induction of Th1 and Th17 immune responses. Previous work indicated that a region on chromosome 11 encoding the IL-12 p40 subunit regulates strain differences in susceptibility to murine trinitrobenzene sulfonic acid (TNBS)-induced colitis. In addition, this region determines strain differences in LPS induced IL-12 responses. Here we investigated how polymorphisms in the coding region of murine Il12b influence IL-12 and IL-23 heterodimer formation. Transfection studies using constructs containing IL-12p35 linked to either IL-12p40 from the colitis-resistant C57Bl/6 strain or to the polymorphic p40 variant from the colitis-susceptible SJL/J strain demonstrated that SJL/J-derived p40 constructs synthesized significantly more IL-12p70 than constructs harboring the C57Bl/6-p40 variant. This could not be attributed to differences in synthesis rate or secretion implicating a higher affinity of SJL/J derived IL-12p40 for its IL-12p35 subunit. This higher affinity is also associated with increased IL-23 synthesis. In addition, C57Bl/6 mice transgenic for the SJL/J 40 variant synthesized significantly more IL-12p70 and were more prone to develop colonic inflammation than did C57Bl/6 mice transgenic for the C57Bl/6-p40 variant upon LPS challenge. The more efficient binding of the polymorphic Il12b variant to p35 and p19 is most likely due to conformational changes following differential glycosylation as a consequence of the polymorphism. The high synthesis rate of the mature cytokines resulting from this efficient binding can lead to rapid pro-inflammatory skewing of immune responses and distortion of the homeostatic balance underlying the higher susceptibility for colitis. PMID:21321105

Zwiers, Antonie; Fuss, Ivan J.; Seegers, Diana; Konijn, Tanja; Garcia-Vallejo, Juan J.; Samson, Janneke N.; Strober, Warren; Kraal, Georg; Bouma, Gerd

2012-01-01

127

The Role of Mitogen-Activated Protein Kinase-Activated Protein Kinases (MAPKAPKs) in Inflammation  

PubMed Central

Mitogen-activated protein kinase (MAPK) pathways are implicated in several cellular processes including proliferation, differentiation, apoptosis, cell survival, cell motility, metabolism, stress response and inflammation. MAPK pathways transmit and convert a plethora of extracellular signals by three consecutive phosphorylation events involving a MAPK kinase kinase, a MAPK kinase, and a MAPK. In turn MAPKs phosphorylate substrates, including other protein kinases referred to as MAPK-activated protein kinases (MAPKAPKs). Eleven mammalian MAPKAPKs have been identified: ribosomal-S6-kinases (RSK1-4), mitogen- and stress-activated kinases (MSK1-2), MAPK-interacting kinases (MNK1-2), MAPKAPK-2 (MK2), MAPKAPK-3 (MK3), and MAPKAPK-5 (MK5). The role of these MAPKAPKs in inflammation will be reviewed. PMID:24705157

Moens, Ugo; Kostenko, Sergiy; Sveinbjørnsson, Baldur

2013-01-01

128

Eukaryotic elongation factor-2 kinase (eEF2K): a potential therapeutic target in cancer.  

PubMed

Eukaryotic elongation factor-2 kinase (eEF2K), encoded by the EEF2K gene, is well-known to be a Ca(2+)/calmodulin (CaM)-dependent kinase which can negatively modulate protein synthesis. It is highly conserved among eukaryotes from mammals to invertebrates, of which human and mouse may have 99 % overall amino acid identity. This kinase can phosphorylate eukaryotic elongation factor-2 (eEF2) or undergo the process of autophosphorylation at multiple sites to inhibit its function in translation elongation. Due to the fact that regulation of eEF2 by eEF2K is an evolutionarily conserved mechanism, eEF2K activity may confer tumor cell adaption to metabolic stress under acute nutrient depletion, and the high expressed level of eEF2K has been found in several types of malignancies. eEF2K may modulate the expression of some apoptotic proteins such as XIAP, c-FLIPL, Bcl-XL, PI3KCI and p70(S6K) to inhibit apoptotic process in cancer. On the other hand, it plays a regulatory role in autophagy involved in mTORC1, AMPK and Atg8, thereby promoting cancer cell survival. Additionally, eEF2K may play a crucial role in the crosstalk between apoptosis and autophagy in cancer. Collectively, these findings have led to the conclusions that eEF2K may contribute to carcinogenesis, and thus being utilized as a potential target for future cancer therapy. PMID:25023961

Fu, L L; Xie, T; Zhang, S Y; Liu, B

2014-10-01

129

Planar dicyclic B6S6, B6S6 (-), and B6S6 (2-) clusters: Boron sulfide analogues of naphthalene.  

PubMed

Inorganic analogues of hydrocarbons or polycyclic aromatic hydrocarbons (PAHs) are of current interest in chemistry. Based upon global structural searches and B3LYP and CCSD(T) calculations, we present herein the perfectly planar dicyclic boron sulfide clusters: D2h B6S6 (1, (1)Ag), D2h B6S6 (-) (2, (2)B3u), and D2h B6S6 (2-) (3, (1)Ag). These are the global minima of the systems, being at least 0.73, 0.81, and 0.53 eV lower in energy, respectively, than their alternative isomers at the CCSD(T) level. The D2h structures feature twin B3S2 five-membered rings, which are fused together via a B2 unit and terminated by two BS groups. Bonding analyses show that the closed-shell B6S6 (2-) (3) cluster possesses 10 delocalized ? electrons, closely analogous to the bonding pattern of the aromatic naphthalene C10H8. The B6S6 (-) (2) and B6S6 (1) species are readily obtained upon removal of one or two ? electrons from B6S6 (2-) (3). The results build a new analogous relationship between boron sulfide clusters and their PAH counterparts. The B6S6 (-) (2) monoanion and B6S6 (2-) (3) dianion can be effectively stabilized in neutral LiB6S6 and Li2B6S6 salts, respectively. PMID:25573556

Li, Da-Zhi; Bai, Hui; Ou, Ting; Chen, Qiang; Zhai, Hua-Jin; Li, Si-Dian

2015-01-01

130

Black raspberry extracts inhibit benzo(a)pyrene diol-epoxide-induced activator protein 1 activation and VEGF transcription by targeting the phosphotidylinositol 3-kinase/Akt pathway.  

PubMed

Previous studies have shown that freeze-dried black raspberry extract fractions inhibit benzo(a)pyrene [B(a)P]-induced transformation of Syrian hamster embryo cells and benzo(a)pyrene diol-epoxide [B(a)PDE]-induced activator protein-1 (AP-1) activity in mouse epidermal Cl 41 cells. The phosphotidylinositol 3-kinase (PI-3K)/Akt pathway is critical for B(a)PDE-induced AP-1 activation in mouse epidermal Cl 41 cells. In the present study, we determined the potential involvement of PI-3K and its downstream kinases on the inhibition of AP-1 activation by black raspberry fractions, RO-FOO3, RO-FOO4, RO-ME, and RO-DM. In addition, we investigated the effects of these fractions on the expression of the AP-1 target genes, vascular endothelial growth factor (VEGF) and inducible nitric oxide synthase (iNOS). Pretreatment of Cl 41 cells with fractions RO-F003 and RO-ME reduced activation of AP-1 and the expression of VEGF, but not iNOS. In contrast, fractions RO-F004 and RO-DM had no effect on AP-1 activation or the expression of either VEGF or iNOS. Consistent with inhibition of AP-1 activation, the RO-ME fraction markedly inhibited activation of PI-3K, Akt, and p70 S6 kinase (p70(S6k)). In addition, overexpression of the dominant negative PI-3K mutant delta p85 reduced the induction of VEGF by B(a)PDE. It is likely that the inhibitory effects of fractions RO-FOO3 and RO-ME on B(a)PDE-induced AP-1 activation and VEGF expression are mediated by inhibition of the PI-3K/Akt pathway. In view of the important roles of AP-1 and VEGF in tumor development, one mechanism for the chemopreventive activity of black raspberries may be inhibition of the PI-3K/Akt/AP-1/VEGF pathway. PMID:16397275

Huang, Chuanshu; Li, Jingxia; Song, Lun; Zhang, Dongyun; Tong, Qiangsong; Ding, Min; Bowman, Linda; Aziz, Robeena; Stoner, Gary D

2006-01-01

131

Protein Kinases  

NSDL National Science Digital Library

This Teaching Resource provides lecture notes and slides for a class covering the structure and function of protein kinases and is part of the course "Cell Signaling Systems: A Course for Graduate Students." The lecture begins with a discussion of the genomics and evolutionary relationships among kinases and then proceeds to describe the structure-function relationships of specific kinases, the molecular mechanisms underlying substrate specificity, and selected issues in regulation of kinase activity.

Avrom Caplan (Mount Sinai School of Medicine;Department of Pharmacology and Biological Chemistry REV)

2005-02-22

132

A proliferation-inducing ligand mediates follicular lymphoma B-cell proliferation and cyclin D1 expression through phosphatidylinositol 3-kinase–regulated mammalian target of rapamycin activation  

PubMed Central

A proliferation-inducing ligand (APRIL), as well as its receptors transmembrane activator and calcium-modulating cyclophilin ligand (CAML) interactor (TACI) and B-cell maturation antigen (BCMA), has been shown to be important in B-cell biology, and overexpression of APRIL in mice results in development of lymphoma. Limited data are available on APRIL-specific signaling responses, but knockout models suggest that signaling through TACI is critical to B-cell homeostasis. To better understand the mechanism by which APRIL exerts its effects and how it may contribute to lymphomagenesis, we sought to characterize the outcome of APRIL-TACI interactions. In support of murine studies, we find that APRIL induces proliferation of human patient follicular lymphoma (FL) B cells in a TACI-dependent manner. This study also shows that APRIL is expressed within the tumor microenvironment and that, upon engagement with TACI, APRIL mediates activation of the phosphatidylinositol 3-kinase (PI3K) pathway. Activation of PI3K via APRIL results in phosphorylation of Akt and mammalian target of rapamycin (mTOR) and the mTOR-specific substrates p70S6 kinase and 4E-binding protein 1 in a TACI-dependent manner. APRIL-mediated signaling also results in phosphorylation of Rb and up-regulation of cyclin D1. These studies are the first to characterize APRIL-TACI–specific signaling and suggest a role for this ligand-receptor pair in FL B-cell growth. PMID:19321861

Gupta, Mamta; Dillon, Stacey R.; Ziesmer, Steven C.; Feldman, Andrew L.; Witzig, Thomas E.; Ansell, Stephen M.; Cerhan, James R.

2009-01-01

133

Ncf1 provides a reactive oxygen species-independent negative feedback regulation of TLR9-induced IL-12p70 in murine dendritic cells.  

PubMed

Permanent exposure to pathogens requires decisions toward tolerance or immunity as a prime task of dendritic cells. The molecular mechanisms preventing uncontrolled immune responses are not completely clear. We investigated the regulatory function of Ncf1, an organizing protein of NADPH oxidase, in the signaling cascade of Toll-like receptors. TLR9-stimulated spleen cells from both Ncf1-deficient and B10.Q mice with a point mutation in exon 8 of Ncf1 exhibited increased IL-12p70 secretion compared with controls. This finding was restricted to stimulatory CpG2216 and not induced by CpG2088. Because only CpG/TLR9-induced IL-12p70 was regulated by Ncf1, we used TRIF(-/-) and MyD88(-/-) cells to show that TLR9/MyD88 was primarily affected. Interestingly, additional experiments revealed that spleen cells from NOX2/gp91(phox)-deficient mice and the blocking of electron transfer by diphenylene iodonium had no influence on CpG-induced IL-12p70, confirming an NADPH oxidase-independent function of Ncf1. Finally, proving the in vivo relevance CpG adjuvant-guided OVA immunization resulted in a strong augmentation of IL-12p70-dependent Th1 IFN-gamma response only in Ncf1-deficient mice. These data suggest for the first time an important role for Ncf1 in the fine tuning of the TLR9/MyD88 pathway in vitro and in vivo that is independent of its role as an activator of NOX2. PMID:19299716

Richter, Cornelia; Juan, Martina Herrero San; Will, Jutta; Brandes, Ralf P; Kalinke, Ulrich; Akira, Shizuo; Pfeilschifter, Josef M; Hultqvist, Malin; Holmdahl, Rikard; Radeke, Heinfried H

2009-04-01

134

Serum Adiponectin, TNF-?, IL12p70, and IL13 Levels in Multiple Sclerosis and the Effects of Different Therapy Regimens  

Microsoft Academic Search

Objectives: Multiple sclerosis (MS) is a chronic inflammatory disease of the human central nervous system. In the present study, we aimed to determine adiponectin, tumor necrosis factor-?, interleukin (IL)-12p70, and IL-13 levels in the sera of patients with MS and to investigate the effects of interferon (IFN), glatiramer acetate (GA), and immunosuppressive treatment regimens on these parameters. Methods: Fifty-seven patients

Ugur Musabak; Seref Demirkaya; Gencer Genç; Rahsan Sagkan Ilikci; Zeki Odabasi

2011-01-01

135

Honokiol activates AMP-activated protein kinase in breast cancer cells via an LKB1-dependent pathway and inhibits breast carcinogenesis  

PubMed Central

Introduction Honokiol, a small-molecule polyphenol isolated from magnolia species, is widely known for its therapeutic potential as an antiinflammatory, antithrombosis, and antioxidant agent, and more recently, for its protective function in the pathogenesis of carcinogenesis. In the present study, we sought to examine the effectiveness of honokiol in inhibiting migration and invasion of breast cancer cells and to elucidate the underlying molecular mechanisms. Methods Clonogenicity and three-dimensional colony-formation assays were used to examine breast cancer cell growth with honokiol treatment. The effect of honokiol on invasion and migration of breast cancer cells was evaluated by using Matrigel invasion, scratch-migration, spheroid-migration, and electric cell-substrate impedance sensing (ECIS)-based migration assays. Western blot and immunofluorescence analysis were used to examine activation of the liver kinase B1 (LKB1)-AMP-activated protein kinase (AMPK) axis. Isogenic LKB1-knockdown breast cancer cell line pairs were developed. Functional importance of AMPK activation and LKB1 overexpression in the biologic effects of honokiol was examined by using AMPK-null and AMPK-wild type (WT) immortalized mouse embryonic fibroblasts (MEFs) and isogenic LKB1-knockdown cell line pairs. Finally, mouse xenografts, immunohistochemical and Western blot analysis of tumors were used. Results Analysis of the underlying molecular mechanisms revealed that honokiol treatment increases AMP-activated protein kinase (AMPK) phosphorylation and activity, as evidenced by increased phosphorylation of the downstream target of AMPK, acetyl-coenzyme A carboxylase (ACC) and inhibition of phosphorylation of p70S6kinase (pS6K) and eukaryotic translation initiation factor 4E binding protein 1 (4EBP1). By using AMPK-null and AMPK-WT (MEFs), we found that AMPK is required for honokiol-mediated modulation of pACC-pS6K. Intriguingly, we discovered that honokiol treatment increased the expression and cytoplasmic translocation of tumor-suppressor LKB1 in breast cancer cells. LKB1 knockdown inhibited honokiol-mediated activation of AMPK and, more important, inhibition of migration and invasion of breast cancer cells. Furthermore, honokiol treatment resulted in inhibition of breast tumorigenesis in vivo. Analysis of tumors showed significant increases in the levels of cytoplasmic LKB1 and phospho-AMPK in honokiol-treated tumors. Conclusions Taken together, these data provide the first in vitro and in vivo evidence of the integral role of the LKB1-AMPK axis in honokiol-mediated inhibition of the invasion and migration of breast cancer cells. In conclusion, honokiol treatment could potentially be a rational therapeutic strategy for breast carcinoma. PMID:22353783

2012-01-01

136

The serine-threonine kinase p90RSK is a new target of enzastaurin in follicular lymphoma cells  

PubMed Central

BACKGROUND AND PURPOSE Follicular lymphoma is the second most common non-Hodgkin's lymphoma and, despite the introduction of rituximab for its treatment, this disease is still considered incurable. Besides genetic alterations involving Bcl-2, Bcl-6 or c-Myc, follicular lymphoma cells often display altered B-cell receptor signalling pathways including overactive PKC and PI3K/Akt systems. EXPERIMENTAL APPROACH The effect of enzastaurin, an inhibitor of PKC, was evaluated both in vitro on follicular lymphoma cell lines and in vivo on a xenograft murine model. Using pharmacological inhibitors and siRNA transfection, we determined the different signalling pathways after enzastaurin treatment. KEY RESULTS Enzastaurin inhibited the serine-threonine kinase p90RSK which has downstream effects on GSK3?. Bad and p70S6K. These signalling proteins control follicular lymphoma cell survival and apoptosis; which accounted for the inhibition by enzastaurin of cell survival and its induction of apoptosis of follicular lymphoma cell lines in vitro. Importantly, these results were replicated in vivo where enzastaurin inhibited the growth of follicular lymphoma xenografts in mice. CONCLUSIONS AND IMPLICATIONS The targeting of p90RSK by enzastaurin represents a new therapeutic option for the treatment of follicular lymphoma. PMID:23992368

Kheirallah, S; Fruchon, S; Ysebaert, L; Blanc, A; Capilla, F; Marrot, A; AlSaati, T; Frenois, F X; Benhadji, K A; Fournié, J J; Laurent, G; Bezombes, C

2013-01-01

137

Saporin-S6: A Useful Tool in Cancer Therapy  

PubMed Central

Thirty years ago, the type 1 ribosome-inactivating protein (RIP) saporin-S6 (also known as saporin) was isolated from Saponaria officinalis L. seeds. Since then, the properties and mechanisms of action of saporin-S6 have been well characterized, and it has been widely employed in the construction of conjugates and immunotoxins for different purposes. These immunotoxins have shown many interesting results when used in cancer therapy, particularly in hematological tumors. The high enzymatic activity, stability and resistance to conjugation procedures and blood proteases make saporin-S6 a very useful tool in cancer therapy. High efficacy has been reported in clinical trials with saporin-S6-containing immunotoxins, at dosages that induced only mild and transient side effects, which were mainly fever, myalgias, hepatotoxicity, thrombocytopenia and vascular leak syndrome. Moreover, saporin-S6 triggers multiple cell death pathways, rendering impossible the selection of RIP-resistant mutants. In this review, some aspects of saporin-S6, such as the chemico-physical characteristics, the structural properties, its endocytosis, its intracellular routing and the pathogenetic mechanisms of the cell damage, are reported. In addition, the recent progress and developments of saporin-S6-containing immunotoxins in cancer immunotherapy are summarized, including in vitro and in vivo pre-clinical studies and clinical trials. PMID:24105401

Polito, Letizia; Bortolotti, Massimo; Mercatelli, Daniele; Battelli, Maria Giulia; Bolognesi, Andrea

2013-01-01

138

Venus Kinase Receptors Control Reproduction in the Platyhelminth Parasite Schistosoma mansoni  

PubMed Central

The Venus Kinase Receptor (VKR) is a single transmembrane molecule composed of an intracellular tyrosine kinase domain close to that of insulin receptor and an extracellular Venus Flytrap (VFT) structure similar to the ligand binding domain of many class C G Protein Coupled Receptors. This receptor tyrosine kinase (RTK) was first discovered in the platyhelminth parasite Schistosoma mansoni, then in a large variety of invertebrates. A single vkr gene is found in most genomes, except in S. mansoni in which two genes Smvkr1 and Smvkr2 exist. VKRs form a unique family of RTKs present only in invertebrates and their biological functions are still to be discovered. In this work, we show that SmVKRs are expressed in the reproductive organs of S. mansoni, particularly in the ovaries of female worms. By transcriptional analyses evidence was obtained that both SmVKRs fulfill different roles during oocyte maturation. Suppression of Smvkr expression by RNA interference induced spectacular morphological changes in female worms with a strong disorganization of the ovary, which was dominated by the presence of primary oocytes, and a defect of egg formation. Following expression in Xenopus oocytes, SmVKR1 and SmVKR2 receptors were shown to be activated by distinct ligands which are L-Arginine and calcium ions, respectively. Signalling analysis in Xenopus oocytes revealed the capacity of SmVKRs to activate the PI3K/Akt/p70S6K and Erk MAPK pathways involved in cellular growth and proliferation. Additionally, SmVKR1 induced phosphorylation of JNK (c-Jun N-terminal kinase). Activation of JNK by SmVKR1 was supported by the results of yeast two-hybrid experiments identifying several components of the JNK pathway as specific interacting partners of SmVKR1. In conclusion, these results demonstrate the functions of SmVKR in gametogenesis, and particularly in oogenesis and egg formation. By eliciting signalling pathways potentially involved in oocyte proliferation, growth and migration, these receptors control parasite reproduction and can therefore be considered as potential targets for anti-schistosome therapies. PMID:24875530

Cailliau, Katia; Morel, Marion; Hahnel, Steffen; Leutner, Silke; Beckmann, Svenja; Grevelding, Christoph G.; Dissous, Colette

2014-01-01

139

Venus kinase receptors control reproduction in the platyhelminth parasite Schistosoma mansoni.  

PubMed

The Venus kinase receptor (VKR) is a single transmembrane molecule composed of an intracellular tyrosine kinase domain close to that of insulin receptor and an extracellular Venus Flytrap (VFT) structure similar to the ligand binding domain of many class C G protein coupled receptors. This receptor tyrosine kinase (RTK) was first discovered in the platyhelminth parasite Schistosoma mansoni, then in a large variety of invertebrates. A single vkr gene is found in most genomes, except in S. mansoni in which two genes Smvkr1 and Smvkr2 exist. VKRs form a unique family of RTKs present only in invertebrates and their biological functions are still to be discovered. In this work, we show that SmVKRs are expressed in the reproductive organs of S. mansoni, particularly in the ovaries of female worms. By transcriptional analyses evidence was obtained that both SmVKRs fulfill different roles during oocyte maturation. Suppression of Smvkr expression by RNA interference induced spectacular morphological changes in female worms with a strong disorganization of the ovary, which was dominated by the presence of primary oocytes, and a defect of egg formation. Following expression in Xenopus oocytes, SmVKR1 and SmVKR2 receptors were shown to be activated by distinct ligands which are L-Arginine and calcium ions, respectively. Signalling analysis in Xenopus oocytes revealed the capacity of SmVKRs to activate the PI3K/Akt/p70S6K and Erk MAPK pathways involved in cellular growth and proliferation. Additionally, SmVKR1 induced phosphorylation of JNK (c-Jun N-terminal kinase). Activation of JNK by SmVKR1 was supported by the results of yeast two-hybrid experiments identifying several components of the JNK pathway as specific interacting partners of SmVKR1. In conclusion, these results demonstrate the functions of SmVKR in gametogenesis, and particularly in oogenesis and egg formation. By eliciting signalling pathways potentially involved in oocyte proliferation, growth and migration, these receptors control parasite reproduction and can therefore be considered as potential targets for anti-schistosome therapies. PMID:24875530

Vanderstraete, Mathieu; Gouignard, Nadège; Cailliau, Katia; Morel, Marion; Hahnel, Steffen; Leutner, Silke; Beckmann, Svenja; Grevelding, Christoph G; Dissous, Colette

2014-05-01

140

The nuts and bolts of AGC protein kinases  

Microsoft Academic Search

The AGC kinase subfamily of protein kinases contains 60 members, including PKA, PKG and PKC. The family comprises some intensely examined protein kinases (such as Akt, S6K, RSK, MSK, PDK1 and GRK) as well as many less well-studied enzymes (such as SGK, NDR, LATS, CRIK, SGK494, PRKX, PRKY and MAST). Research has shed new light onto the architecture and regulatory

Laura R. Pearce; David Komander; Dario R. Alessi

2010-01-01

141

Phosphorylation of ribosomal protein S6 mediates compensatory renal hypertrophy.  

PubMed

The molecular mechanism underlying renal hypertrophy and progressive nephron damage remains poorly understood. Here we generated congenic ribosomal protein S6 (rpS6) knock-in mice expressing nonphosphorylatable rpS6 and found that uninephrectomy-induced renal hypertrophy was significantly blunted in these knock-in mice. Uninephrectomy-induced increases in cyclin D1 and decreases in cyclin E in the remaining kidney were attenuated in the knock-in mice compared with their wild-type littermates. Uninephrectomy induced rpS6 phosphorylation in the wild-type mice; however, no rpS6 phosphorylation was detected in uninephrectomized or sham-operated knock-in mice. Nonetheless, uninephrectomy stimulated comparable 4E-BP1 phosphorylation in both knock-in and wild-type mice, indicating that mTORC1 was still activated in the knock-in mice. Moreover, the mTORC1 inhibitor rapamycin prevented both rpS6 and 4E-BP1 phosphorylation, significantly blunted uninephrectomy-induced renal hypertrophy in wild-type mice, but did not prevent residual renal hypertrophy despite inhibiting 4E-BP1 phosphorylation in uninephrectomized knock-in mice. Thus, both genetic and pharmacological approaches unequivocally demonstrate that phosphorylated rpS6 is a downstream effector of the mTORC1-S6K1 signaling pathway mediating renal hypertrophy. Hence, rpS6 phosphorylation facilitates the increase in cyclin D1 and decrease in cyclin E1 that underlie the hypertrophic nature of uninephrectomy-induced kidney growth.Kidney International advance online publication, 17 September 2014; doi:10.1038/ki.2014.302. PMID:25229342

Xu, Jinxian; Chen, Jianchun; Dong, Zheng; Meyuhas, Oded; Chen, Jian-Kang

2014-09-17

142

Characterization and response of newly developed high-grade glioma cultures to the tyrosine kinase inhibitors, erlotinib, gefitinib and imatinib  

SciTech Connect

High-grade gliomas (HGG), are the most common aggressive brain tumours in adults. Inhibitors targeting growth factor signalling pathways in glioma have shown a low clinical response rate. To accurately evaluate response to targeted therapies further in vitro studies are necessary. Growth factor pathway expression using epidermal growth factor receptor (EGFR), mutant EGFR (EGFRvIII), platelet derived growth factor receptor (PDGFR), C-Kit and C-Abl together with phosphatase and tensin homolog (PTEN) expression and downstream activation of AKT and phosphorylated ribosomal protein S6 (P70S6K) was analysed in 26 primary glioma cultures treated with the tyrosine kinase inhibitors (TKIs) erlotinib, gefitinib and imatinib. Response to TKIs was assessed using 50% inhibitory concentrations (IC{sub 50}). Response for each culture was compared with the EGFR/PDGFR immunocytochemical pathway profile using hierarchical cluster analysis (HCA) and principal component analysis (PCA). Erlotinib response was not strongly associated with high expression of the growth factor pathway components. PTEN expression did not correlate with response to any of the three TKIs. Increased EGFR expression was associated with gefitinib response; increased PDGFR-{alpha} expression was associated with imatinib response. The results of this in vitro study suggest gefitinib and imatinib may have therapeutic potential in HGG tumours with a corresponding growth factor receptor expression profile. -- Highlights: Black-Right-Pointing-Pointer Non-responders had low EGFR expression, high PDGFR-{beta}, and a low proliferation rate. Black-Right-Pointing-Pointer PTEN is not indicative of response to a TKI. Black-Right-Pointing-Pointer Erlotinib response was not associated with expression of the proteins examined. Black-Right-Pointing-Pointer Imatinib-response correlated with expression of PDGFR-{alpha}. Black-Right-Pointing-Pointer Gefitinib response correlated with increased expression of EGFR.

Kinsella, Paula, E-mail: paula.kinsella@dcu.ie [National Institute for Cellular Biotechnology, Dublin City University, Dublin 9 (Ireland)] [National Institute for Cellular Biotechnology, Dublin City University, Dublin 9 (Ireland); Howley, Rachel, E-mail: rhowley@rcsi.ie [Department of Neuropathology, Beaumont Hospital, Dublin 9 (Ireland)] [Department of Neuropathology, Beaumont Hospital, Dublin 9 (Ireland); Doolan, Padraig, E-mail: padraig.doolan@dcu.ie [National Institute for Cellular Biotechnology, Dublin City University, Dublin 9 (Ireland)] [National Institute for Cellular Biotechnology, Dublin City University, Dublin 9 (Ireland); Clarke, Colin, E-mail: colin.clarke@dcu.ie [National Institute for Cellular Biotechnology, Dublin City University, Dublin 9 (Ireland)] [National Institute for Cellular Biotechnology, Dublin City University, Dublin 9 (Ireland); Madden, Stephen F., E-mail: maddens@dcu.ie [National Institute for Cellular Biotechnology, Dublin City University, Dublin 9 (Ireland); Clynes, Martin, E-mail: Martin.Clynes@dcu.ie [National Institute for Cellular Biotechnology, Dublin City University, Dublin 9 (Ireland)] [National Institute for Cellular Biotechnology, Dublin City University, Dublin 9 (Ireland); Farrell, Michael, E-mail: michaelfarrell@beaumont.ie [Department of Neuropathology, Beaumont Hospital, Dublin 9 (Ireland)] [Department of Neuropathology, Beaumont Hospital, Dublin 9 (Ireland); Amberger-Murphy, Verena, E-mail: Verena.Murphy@icorg.ie [National Institute for Cellular Biotechnology, Dublin City University, Dublin 9 (Ireland) [National Institute for Cellular Biotechnology, Dublin City University, Dublin 9 (Ireland); All Ireland Co-operative, Oncology Research Group, 60 Fitzwilliam Square, Dublin 2 (Ireland)

2012-03-10

143

Maturation of monocyte derived dendritic cells with OK432 boosts IL-12p70 secretion and conveys strong T-cell responses  

PubMed Central

Background Design of tumour specific immunotherapies using the patients' own dendritic cells (DC) is a fast advancing scientific field. The functional qualities of the DC generated in vitro are critical, and today's gold standard for maturation is a cytokine cocktail consisting of IL-1?, IL-6, TNF-? and PGE2 generating cells lacking IL-12p70 production. OK432 is an immunotherapeutic agent derived from killed Streptococcus pyogenes that has been used clinically to treat malignant and benign neoplasms for decades. Methods In this study, we analysed the effects of OK432 on DC maturation, DC migration, cytokine and chemokine secretion as well as T-cell stimulatory capacity, and compared it to the cytokine cocktail alone and combinations of OK432 with the cytokine cocktail. Results OK432 induced a marked up-regulation of CD40 on the cell surface as well as a strong inflammatory response from the DC with significantly more secretion of 19 different cytokines and chemokines compared to the cytokine cocktail. Interestingly, secretion of IL-15 and IL-12p70 was detected at high concentrations after maturation of DC with OK432. However, the OK432 treated DC did not migrate as well as DC treated with cytokine cocktail in a transwell migration assay. During allogeneic T-cell stimulation OK432 treated DC induced proliferation of over 50 percent of CD4 and 30 percent of CD8 T-cells for more than two cell divisions, whereas cytokine cocktail treated DC induced proliferation of 12 and 11 percent of CD4 and CD8 T-cells, respectively. Conclusions The clinically approved compound OK432 has interesting properties that warrants its use in DC immunotherapy and should be considered as a potential immunomodulating agent in cancer immunotherapy. PMID:21208424

2011-01-01

144

AMP-activated protein kinase (AMPK) as a potential therapeutic target independent of PI3K/Akt signaling in prostate cancer  

PubMed Central

Depletion of cellular energy activates the AMP-activated kinase (AMPK) to favor energy-producing catabolic processes during tumorigenesis. Using a panel of in vitro cell lines and resected tumors, we investigated the therapeutic value of manipulating AMPK in prostate cancer (PC). Phospho-AMPK expression was significantly elevated in human PC cells and clinical PC samples. In clinical PC, we observed a trend for increasing phospho-AMPK with increasing Gleason sum score; Phospho-AMPK expression was associated with phospho-ACC (p=0.0023). Using the paired PC3 and PC3M cells to model progressive androgen-independent PC, treatment with either 5-aminoimidazole-4-carboxamide riboside (AICAR) or A-769662 suppressed proliferation, migration and invasion in both cell lines, and down-regulated mTOR and P70S6Ki levels regardless of the Akt status. Involvement of AMPK was confirmed by Compound C (AMPK inhibitor) and siRNA-mediated AMPK silencing. Despite similar functional responses in PC3 and PC3M cells, AMPK activation resulted in sustained phospho-Akt activation in PC3M cells, but not in PC3 cells. This prompted the addition of the PI3K inhibitor LY-294002 to AICAR treatment of PC3M cells in a proliferation assay. Interestingly, we found no synergistic effects upon combined treatment. Collectively, these findings support AMPK as a potential therapeutic target independent of PI3K/Akt signalling. PMID:25594043

Choudhury, Yashmin; Yang, Zichu; Ahmad, Imran; Nixon, Colin; Salt, Ian P.; Leung, Hing Y.

2014-01-01

145

Heat-Shock Response in Methanosarcina mazei S-6  

Microsoft Academic Search

.   The dnaK locus of Methanosarcina mazei S-6, a mesophilic organism of the phylogenetic domain Archaea, contains the heat-shock genes 5?–grpE–dnaK–dnaJ–3?. Parameters known to affect the response of these genes in organisms of the other two domains, Bacteria and Eucarya, were\\u000a tested to determine their effects on the archaeal homologs. The mRNA from the three genes increased after heat shock

Marianne Lange; Alberto J. L. Macario; Birgitte K. Ahring; Everly Conway de Macario

1997-01-01

146

Elongation factor-2 kinase regulates autophagy in human glioblastoma cells.  

PubMed

Elongation factor-2 kinase (eEF-2 kinase), also known as Ca(2+)/calmodulin-dependent kinase III, regulates protein synthesis by controlling the rate of peptide chain elongation. The activity of eEF-2 kinase is increased in glioblastoma and other malignancies, yet its role in neoplasia is uncertain. Recent evidence suggests that autophagy plays an important role in oncogenesis and that this can be regulated by mammalian target of rapamycin (mTOR). Because eEF-2 kinase lies downstream of mTOR, we studied the role of eEF-2 kinase in autophagy using human glioblastoma cell lines. Knockdown of eEF-2 kinase by RNA interference inhibited autophagy in glioblastoma cell lines, as measured by light chain 3 (LC3)-II formation, acidic vesicular organelle staining, and electron microscopy. In contrast, overexpression of eEF-2 kinase increased autophagy. Furthermore, inhibition of autophagy markedly decreased the viability of glioblastoma cells grown under conditions of nutrient depletion. Nutrient deprivation increased eEF-2 kinase activity and decreased the activity of S6 kinase, suggesting an involvement of mTOR pathway in the eEF-2 kinase regulation of autophagy. These results suggest that eEF-2 kinase plays a regulatory role in the autophagic process in tumor cells; and eEF-2 kinase is a downstream member of the mTOR signaling; eEF-2 kinase may promote cancer cell survival under conditions of nutrient deprivation through regulating autophagy. Therefore, eEF-2 kinase may be a part of a survival mechanism in glioblastoma and targeting this kinase may represent a novel approach to cancer treatment. PMID:16540650

Wu, Hao; Yang, Jin-Ming; Jin, Shengkan; Zhang, Haiyan; Hait, William N

2006-03-15

147

Expression of an active tobacco mitogen-activated protein kinase kinase kinase enhances freezing  

E-print Network

Expression of an active tobacco mitogen-activated protein kinase kinase kinase enhances freezing mitogen- activated protein kinase kinase kinase provided benefits in transgenic tobacco at freezing the effect of expressing a heter- ologous tobacco mitogen-activated protein kinase kinase kinase (Nicotiana

Sheen, Jen

148

Improved protocol to purify untagged amelogenin - Application to murine amelogenin containing the equivalent P70?T point mutation observed in human amelogenesis imperfecta.  

PubMed

Amelogenin is the predominant extracellular protein responsible for converting carbonated hydroxyapatite into dental enamel, the hardest and most heavily mineralized tissue in vertebrates. Despite much effort, the precise mechanism by which amelogenin regulates enamel formation is not fully understood. To assist efforts aimed at understanding the biochemical mechanism of enamel formation, more facile protocols to purify recombinantly expressed amelogenin, ideally without any tag to assist affinity purification, are advantageous. Here we describe an improved method to purify milligram quantities of amelogenin that exploits its high solubility in 2% glacial acetic acid under conditions of low ionic strength. The method involves heating the frozen cell pellet for two 15min periods at ?70°C with 2min of sonication in between, dialysis twice in 2% acetic acid (1:250 v/v), and reverse phase chromatography. A further improvement in yield is obtained by resuspending the frozen cell pellet in 6M guanidine hydrochloride in the first step. The acetic acid heating method is illustrated with a murine amelogenin containing the corresponding P70?T point mutation observed in an human amelogenin associated with amelogenesis imperfecta (P71T), while the guanidine hydrochloride heating method is illustrated with wild type murine amelogenin (M180). The self-assembly properties of P71T were probed by NMR chemical shift perturbation studies as a function of protein (0.1-1.8mM) and NaCl (0-367mM) concentration. Relative to similar studies with wild type murine amelogenin, P71T self-associates at lower protein or salt concentrations with the interactions initiated near the N-terminus. PMID:25306873

Buchko, Garry W; Shaw, Wendy J

2014-10-13

149

Association of IL-12p70 and IL-6:IL-10 ratio with autism-related behaviors in 22q11.2 deletion syndrome: a preliminary report  

PubMed Central

22q11.2 deletion syndrome (22q11DS) is a genetic disorder that conveys a significant risk for the development of social behavior disorders, including autism and schizophrenia. Also known as DiGeorge syndrome, 22q11DS is the second most common childhood genetic disorder and is characterized by an elevated risk for immune disorders, as 77% of individuals have an identifiable immune deficiency. We hypothesize that this immune dysfunction could contribute to the elevated risk of impaired social behavior seen in 22q11DS. The current study begins to elucidate these immune deficits and link them with the behavioral alterations associated with the disorder. Serum concentrations of a series of cytokines were examined, using a multiplex immunoassay, in sixteen individuals with 22q11DS and screened for autism-related behavior using the Autism Diagnostic Interview-Revised (ADI-R). This preliminary study examined correlations between specific immune proteins and each of the ADI-R algorithm scores (social, communication, and repetitive behavior). The inflammatory cytokine IL-1?, as well as the ratio between the inflammatory cytokine IL-6 and the anti-inflammatory cytokine IL-10, were correlated with social scores (r = 0.851, p = 0.004; r = 0.580, p = 0.018). In addition, the inflammatory cytokines interferon gamma and IL-12p70 were correlated with repetitive behaviors (r = 0.795, p = 0.033; r = 0.774, p = 0.002). Interestingly, IL-12 has been reported to be increased in autistic children. These data show a positive relationship between severity of autism-related behaviors and level of serum concentrations of inflammatory cytokines in individuals with 22q11DS, providing a basis for further inquiry. PMID:23353117

Ross, Heather; Guo, Ying; Coleman, Karlene; Ousley, Opal; Miller, Andrew

2013-01-01

150

Association of IL-12p70 and IL-6:IL-10 ratio with autism-related behaviors in 22q11.2 deletion syndrome: a preliminary report.  

PubMed

22q11.2 deletion syndrome (22q11DS) is a genetic disorder that conveys a significant risk for the development of social behavior disorders, including autism and schizophrenia. Also known as DiGeorge syndrome, 22q11DS is the second most common genetic disorder and is characterized by an elevated risk for immune dysfunction, up to 77% of individuals have an identifiable immune deficiency. We hypothesize that this immune dysfunction could contribute to the elevated risk of impaired social behavior seen in 22q11DS. The current study begins to elucidate these immune deficits and link them with the behavioral alterations associated with the disorder. Serum concentrations of a series of cytokines were examined, using a multiplex immunoassay, in sixteen individuals with 22q11DS and screened for autism-related behavior using the Autism Diagnostic Interview-Revised (ADI-R). This preliminary study examined correlations between specific immune proteins and each of the ADI-R algorithm scores (social, communication, and repetitive behavior). The inflammatory cytokine IL-1?, as well as the ratio between the inflammatory cytokine IL-6 and the anti-inflammatory cytokine IL-10, were correlated with social scores (r=0.851, p=0.004; r=0.580, p=0.018). In addition, the inflammatory cytokines interferon gamma and IL-12p70 were correlated with repetitive behaviors (r=0.795, p=0.033; r=0.774, p=0.002). Interestingly, IL-12 has been reported to be increased in autistic children. These data show a positive association between severity of autism-related behaviors and level of serum concentrations of inflammatory cytokines in individuals with 22q11DS, providing a basis for further inquiry. PMID:23353117

Ross, Heather E; Guo, Ying; Coleman, Karlene; Ousley, Opal; Miller, Andrew H

2013-07-01

151

Leptin induces macrophage lipid body formation by a phosphatidylinositol 3-kinase- and mammalian target of rapamycin-dependent mechanism.  

PubMed

Leptin is an adipocyte-derived hormone/cytokine that links nutritional status with neuroendocrine and immune functions. Lipid bodies (lipid droplets) are emerging as dynamic organelles with roles in lipid metabolism and inflammation. Here we investigated the roles of leptin in signaling pathways involved in cytoplasmic lipid body biogenesis and leukotriene B(4) synthesis in macrophages. Our results demonstrated that leptin directly activated macrophages and induced the formation of adipose differentiation-related protein-enriched lipid bodies. Newly formed lipid bodies were sites of 5-lipoxygenase localization and correlated with an enhanced capacity of leukotriene B(4) production. We demonstrated that leptin-induced macrophage activation was dependent on phosphatidylinositol 3-kinase (PI3K) activity, since the lipid body formation was inhibited by LY294002 and was absent in the PI3K knock-out mice. Leptin induces phosphorylation of p70(S6K) and 4EBP1 key downstream signaling intermediates of the mammalian target of rapamycin (mTOR) pathway in a rapamycin-sensitive mechanism. The mTOR inhibitor, rapamycin, inhibited leptin-induced lipid body formation, both in vivo and in vitro. In addition, rapamycin inhibited leptin-induced adipose differentiation-related protein accumulation in macrophages and lipid body-dependent leukotriene synthesis, demonstrating a key role for mTOR in lipid body biogenesis and function. Our results establish PI3K/mTOR as an important signaling pathway for leptin-induced cytoplasmic lipid body biogenesis and adipose differentiation-related protein accumulation. Furthermore, we demonstrate a previously unrecognized link between intracellular (mTOR) and systemic (leptin) nutrient sensors in macrophage lipid metabolism. Leptin-induced increased formation of cytoplasmic lipid bodies and enhanced inflammatory mediator production in macrophages may have implications for obesity-related cardiovascular diseases. PMID:18039669

Maya-Monteiro, Clarissa M; Almeida, Patricia E; D'Avila, Heloisa; Martins, Aline S; Rezende, Ana Paula; Castro-Faria-Neto, Hugo; Bozza, Patricia T

2008-01-25

152

The selectivity of protein kinase inhibitors: a further update  

PubMed Central

The specificities of 65 compounds reported to be relatively specific inhibitors of protein kinases have been profiled against a panel of 70–80 protein kinases. On the basis of this information, the effects of compounds that we have studied in cells and other data in the literature, we recommend the use of the following small-molecule inhibitors: SB 203580/SB202190 and BIRB 0796 to be used in parallel to assess the physiological roles of p38 MAPK (mitogen-activated protein kinase) isoforms, PI-103 and wortmannin to be used in parallel to inhibit phosphatidylinositol (phosphoinositide) 3-kinases, PP1 or PP2 to be used in parallel with Src-I1 (Src inhibitor-1) to inhibit Src family members; PD 184352 or PD 0325901 to inhibit MKK1 (MAPK kinase-1) or MKK1 plus MKK5, Akt-I-1/2 to inhibit the activation of PKB (protein kinase B/Akt), rapamycin to inhibit TORC1 [mTOR (mammalian target of rapamycin)–raptor (regulatory associated protein of mTOR) complex], CT 99021 to inhibit GSK3 (glycogen synthase kinase 3), BI-D1870 and SL0101 or FMK (fluoromethylketone) to be used in parallel to inhibit RSK (ribosomal S6 kinase), D4476 to inhibit CK1 (casein kinase 1), VX680 to inhibit Aurora kinases, and roscovitine as a pan-CDK (cyclin-dependent kinase) inhibitor. We have also identified harmine as a potent and specific inhibitor of DYRK1A (dual-specificity tyrosine-phosphorylated and -regulated kinase 1A) in vitro. The results have further emphasized the need for considerable caution in using small-molecule inhibitors of protein kinases to assess the physiological roles of these enzymes. Despite being used widely, many of the compounds that we analysed were too non-specific for useful conclusions to be made, other than to exclude the involvement of particular protein kinases in cellular processes. PMID:17850214

Bain, Jenny; Plater, Lorna; Elliott, Matt; Shpiro, Natalia; Hastie, C. James; Mclauchlan, Hilary; Klevernic, Iva; Arthur, J. Simon C.; Alessi, Dario R.; Cohen, Philip

2007-01-01

153

Raptor, a Binding Partner of Target of Rapamycin (TOR), Mediates TOR Action  

Microsoft Academic Search

mTOR controls cell growth, in part by regulating p70 S6 kinase ? (p70?) and eukaryotic initiation factor 4E binding protein 1 (4EBP1). Raptor is a 150 kDa mTOR binding protein that also binds 4EBP1 and p70?. The binding of raptor to mTOR is necessary for the mTOR-catalyzed phosphorylation of 4EBP1 in vitro, and it strongly enhances the mTOR kinase activity

Kenta Hara; Yoshiko Maruki; Xiaomeng Long; Ken-ichi Yoshino; Noriko Oshiro; Sujuti Hidayat; Chiharu Tokunaga; Joseph Avruch; Kazuyoshi Yonezawa

2002-01-01

154

Inhibition of mTOR Kinase by AZD8055 Can Antagonize Chemotherapy-induced Cell Death through Autophagy Induction and Down-regulation of p62/Sequestosome 1*  

PubMed Central

AZD8055 is an ATP-competitive inhibitor of mammalian target of rapamycin (mTOR) that forms two multiprotein complexes, mTORC1 and mTORC2, and negatively regulates autophagy. We demonstrate that AZD8055 stimulates and potentiates chemotherapy-mediated autophagy, as shown by LC3I-II conversion and down-regulation of the ubiquitin-binding protein p62/sequestosome 1. AZD8055-induced autophagy was pro-survival as shown by its ability to attenuate cell death and DNA damage (p-H2AX), and to enhance clonogenic survival by cytotoxic chemotherapy. Autophagy inhibition by siRNA against Beclin 1 or LC3B, or by chloroquine, partially reversed the cytoprotective effect of AZD8055 that was independent of cell cycle inhibition. The pro-survival role of autophagy was confirmed using ectopic expression of Beclin 1 that conferred cytoprotection. To determine whether autophagy-mediated down-regulation of p62/sequestosome 1 contributes to its pro-survival role, we generated p62 knockdown cells using shRNA that showed protection from chemotherapy-induced cell death and DNA damage. We also overexpressed wild-type (wt) p62 that promoted chemotherapy-induced cell death, whereas mutated p62 at functional domains (PB1, UBA) failed to do so. The ability of ectopic wt p62 to promote cell death was blocked by AZD8055. AZD8055 was shown to inhibit phosphorylation of the autophagy-initiating kinase ULK1 at Ser757 and inhibited known targets of mTORC1 (p-mTOR Ser2448, p70S6K, p-S6, p4EBP1) and mTORC2 (p-mTOR Ser2481, p-AKT Ser473). Knockdown of mTOR, but not Raptor or Rictor, reduced p-ULK1 at Ser757 and enhanced chemotherapy-induced autophagy that resulted in a similar cytoprotective effect as shown for AZD8055. In conclusion, AZD8055 inhibits mTOR kinase and ULK1 phosphorylation to induce autophagy whose pro-survival effect is due, in part, to down-regulation of p62. PMID:21949121

Huang, Shengbing; Yang, Zhineng J.; Yu, Chunrong; Sinicrope, Frank A.

2011-01-01

155

hnRNPA1 couples nuclear export and translation of specific mRNAs downstream of FGF-2/S6K2 signalling  

PubMed Central

The increased cap-independent translation of anti-apoptotic proteins is involved in the development of drug resistance in lung cancer but signalling events regulating this are poorly understood. Fibroblast growth factor 2 (FGF-2) signalling-induced S6 kinase 2 (S6K2) activation is necessary, but the downstream mediator(s) coupling this kinase to the translational response is unknown. Here, we show that S6K2 binds and phosphorylates hnRNPA1 on novel Ser4/6 sites, increasing its association with BCL-XL and XIAP mRNAs to promote their nuclear export. In the cytoplasm, phosphoS4/6-hnRNPA1 dissociates from these mRNAs de-repressing their IRES-mediated translation. This correlates with the phosphorylation-dependent association of hnRNPA1 with 14-3-3 leading to hnRNPA1 sumoylation on K183 and its re-import into the nucleus. A non-phosphorylatible, S4/6A mutant prevented these processes, hindering the pro-survival activity of FGF-2/S6K2 signalling. Interestingly, immunohistochemical staining of lung and breast cancer tissue samples demonstrated that increased S6K2 expression correlates with decreased cytoplasmic hnRNPA1 and increased BCL-XL expression. In short, phosphorylation on novel N-term sites of hnRNPA1 promotes translation of anti-apoptotic proteins and is indispensable for the pro-survival effects of FGF-2. PMID:25324306

Roy, Rajat; Durie, Danielle; Li, Hui; Liu, Bing-Qian; Skehel, John Mark; Mauri, Francesco; Cuorvo, Lucia Veronica; Barbareschi, Mattia; Guo, Lin; Holcik, Martin; Seckl, Michael J.; Pardo, Olivier E.

2014-01-01

156

A novel mTOR-regulated phosphorylation site in elongation factor 2 kinase modulates the activity of the kinase and its binding to calmodulin.  

PubMed

Eukaryotic elongation factor 2 (eEF2) kinase is an unusual calcium- and calmodulin-dependent protein kinase that is regulated by insulin through the rapamycin-sensitive mTOR pathway. Here we show that insulin decreases the ability of eEF2 kinase to bind calmodulin in a rapamycin-sensitive manner. We identify a novel phosphorylation site in eEF2 kinase (Ser78) that is located immediately next to its calmodulin-binding motif. Phosphorylation of this site is increased by insulin in a rapamycin-sensitive fashion. Regulation of the phosphorylation of Ser78 also requires amino acids and the protein kinase phosphoinositide-dependent kinase 1. Mutation of this site to alanine strongly attenuates the effects of insulin and rapamycin both on the binding of calmodulin to eEF2 kinase and on eEF2 kinase activity. Phosphorylation of Ser78 is thus likely to link insulin and mTOR signaling to the control of eEF2 phosphorylation and chain elongation. This site is not a target for known kinases in the mTOR pathway, e.g., the S6 kinases, implying that it is phosphorylated by a novel mTOR-linked protein kinase that serves to couple hormones and amino acids to the control of translation elongation. eEF2 kinase is thus a target for mTOR signaling independently of previously known downstream components of the pathway. PMID:15024086

Browne, Gareth J; Proud, Christopher G

2004-04-01

157

Mycobacterium tuberculosis promotes Th17 expansion via regulation of human dendritic cells toward a high CD14 and low IL-12p70 phenotype that reprograms upon exogenous IFN-?.  

PubMed

The capacity to develop protective immunity against mycobacteria is heterogeneously distributed among human beings, and it is currently unknown why the initial immune response induced against Mycobacterium tuberculosis (Mtb) does not provide proper clearance of this pathogen. Dendritic cells (DCs) are some of the first cells to interact with Mtb and they play an essential role in development of protective immunity against Mtb. Given that Mtb-infected macrophages have difficulties in degrading Mtb, they need help from IFN-?-producing CD4+ T cells propagated via IL-12p70-producing DCs. Here we report that Mtb modifies human DC plasticity by expanding a CD14+ DC subset with weak IL-12p70-producing capacity. The CD14+ Mtb-promoted subset was furthermore poor inducers of IFN-? by naive CD4+ T cells, but instead prompted IL-17A-producing ROR?T+ CD4+ T cells. Mtb-derived peptidoglycan and mannosylated lipoarabinomannan partly recapitulated the subset partition induced by Mtb. Addition of IFN-?, but neither IL-17A nor IL-22, which are potentially produced by Mtb-exposed ?/?-T cells in mucosal linings, inhibited the differentiation toward CD14+ DCs and promoted high-level IL-12p70 in Mtb-challenged DCs. We conclude that Mtb exploits DC plasticity to reduce production of IL-12p70, and that this process is entirely divertible by exogenous IFN-?. These data suggest that strategies to increase local IFN-? production in the lungs of tuberculosis patients may boost host immunity toward Mtb. PMID:25223368

Søndergaard, Jonas Nørskov; Laursen, Janne Marie; Rosholm, Lisbeth Buus; Brix, Susanne

2014-12-01

158

TOR signalling and control of cell growth  

Microsoft Academic Search

TOR, phosphatidylinositol 3-kinase, p70s6k, and 4E-BP1 have recently emerged as components of a major signalling pathway that is dedicated to protein translation and thus to cell growth. This pathway appears to be conserved, at least in part, in yeast, slime molds, plants, flies, and mammals. TOR and phosphatidylinositol 3-kinase control p70s6k and 4E-BP1, which, in turn, directly control the translation

George Thomas; Michael N Hall

1997-01-01

159

KEA: kinase enrichment analysis  

PubMed Central

Motivation: Multivariate experiments applied to mammalian cells often produce lists of proteins/genes altered under treatment versus control conditions. Such lists can be projected onto prior knowledge of kinase–substrate interactions to infer the list of kinases associated with a specific protein list. By computing how the proportion of kinases, associated with a specific list of proteins/genes, deviates from an expected distribution, we can rank kinases and kinase families based on the likelihood that these kinases are functionally associated with regulating the cell under specific experimental conditions. Such analysis can assist in producing hypotheses that can explain how the kinome is involved in the maintenance of different cellular states and can be manipulated to modulate cells towards a desired phenotype. Summary: Kinase enrichment analysis (KEA) is a web-based tool with an underlying database providing users with the ability to link lists of mammalian proteins/genes with the kinases that phosphorylate them. The system draws from several available kinase–substrate databases to compute kinase enrichment probability based on the distribution of kinase–substrate proportions in the background kinase–substrate database compared with kinases found to be associated with an input list of genes/proteins. Availability: The KEA system is freely available at http://amp.pharm.mssm.edu/lib/kea.jsp Contact: avi.maayan@mssm.edu PMID:19176546

Lachmann, Alexander; Ma'ayan, Avi

2009-01-01

160

Planar dicyclic B6S6, B6S6-, and B6S62- clusters: Boron sulfide analogues of naphthalene  

NASA Astrophysics Data System (ADS)

Inorganic analogues of hydrocarbons or polycyclic aromatic hydrocarbons (PAHs) are of current interest in chemistry. Based upon global structural searches and B3LYP and CCSD(T) calculations, we present herein the perfectly planar dicyclic boron sulfide clusters: D2h B6S6 (1, 1Ag), D2h B6S6- (2, 2B3u), and D2h B6S62- (3, 1Ag). These are the global minima of the systems, being at least 0.73, 0.81, and 0.53 eV lower in energy, respectively, than their alternative isomers at the CCSD(T) level. The D2h structures feature twin B3S2 five-membered rings, which are fused together via a B2 unit and terminated by two BS groups. Bonding analyses show that the closed-shell B6S62- (3) cluster possesses 10 delocalized ? electrons, closely analogous to the bonding pattern of the aromatic naphthalene C10H8. The B6S6- (2) and B6S6 (1) species are readily obtained upon removal of one or two ? electrons from B6S62- (3). The results build a new analogous relationship between boron sulfide clusters and their PAH counterparts. The B6S6- (2) monoanion and B6S62- (3) dianion can be effectively stabilized in neutral LiB6S6 and Li2B6S6 salts, respectively.

Li, Da-Zhi; Bai, Hui; Ou, Ting; Chen, Qiang; Zhai, Hua-Jin; Li, Si-Dian

2015-01-01

161

GSK3? regulates milk synthesis in and proliferation of dairy cow mammary epithelial cells via the mTOR/S6K1 signaling pathway.  

PubMed

Glycogen synthase kinase 3 (GSK3) is a serine/threonine kinase, whose activity is inhibited by AKT phosphorylation. This inhibitory phosphorylation of GSK3? can in turn play a regulatory role through phosphorylation of several proteins (such as mTOR, elF2B) to promote protein synthesis. mTOR is a key regulator in protein synthesis and cell proliferation, and recent studies have shown that both GSK3? and mTORC1 can regulate SREBP1 to promote fat synthesis. Thus far, however, the cross talk between GSK3? and the mTOR pathway in the regulation of milk synthesis and associated cell proliferation is not well understood. In this study the interrelationship between GSK3? and the mTOR/S6K1 signaling pathway leading to milk synthesis and proliferation of dairy cow mammary epithelial cells (DCMECs) was analyzed using techniques including GSK3? overexpression by transfection, GSK3? inhibition, mTOR inhibition and methionine stimulation. The analyses revealed that GSK3? represses the mTOR/S6K1 pathway leading to milk synthesis and cell proliferation of DCMECs, whereas GSK3? phosphorylation enhances this pathway. Conversely, the activated mTOR/S6K1 signaling pathway downregulates GSK3? expression but enhances GSK3? phosphorylation to increase milk synthesis and cell proliferation, whereas inhibition of mTOR leads to upregulation of GSK3? and repression of GSK3? phosphorylation, which in turn decreases milk synthesis, and cell proliferation. These ?ndings indicate that GSK3? and phosphorylated GSK3? regulate milk synthesis and proliferation of DCMECs via the mTOR/S6K1 signaling pathway. These findings provide new insight into the mechanisms of milk synthesis. PMID:24995926

Zhang, Xia; Zhao, Feng; Si, Yu; Huang, Yuling; Yu, Cuiping; Luo, Chaochao; Zhang, Na; Li, Qingzhang; Gao, Xuejun

2014-01-01

162

Expression of S6K1 in human visceral adipose tissue is upregulated in obesity and related to insulin resistance and inflammation.  

PubMed

The ribosomal protein S6 kinase 1 (S6K1) is a component of the insulin signalling pathway that has been proposed as a key molecular factor in insulin resistance development under conditions of nutrient overload. The aim was to evaluate the involvement of S6K1 in obesity as well as to explore their association with visceral adipose tissue (VAT) inflammation. Samples obtained from 40 subjects were used. Gene expression levels of RPS6KB1 and key inflammatory markers were analysed in VAT. The effect of insulin on transcript levels of RPS6KB1 in human differentiated adipocytes was also explored. RPS6KB1 mRNA levels in VAT were increased (P < 0.05) in obese patients. Insulin treatment significantly enhanced (P < 0.01) gene expression levels of RPS6KB1 and a positive association (P < 0.05) of RPS6KB1 expression with different markers of insulin resistance was observed. Moreover, RPS6KB1 gene expression levels were positively correlated with VAT gene expression levels of the inflammatory markers CCL2, CD68, MMP2, MMP9, VEGFA and CHI3L1 as well as with mRNA levels of MTOR and MAPK8, representative players involved in signalling pathways related to S6K1. The increased levels of S6K1 in obesity and its positive association with insulin resistance and inflammation suggest a role for this protein in the changes that take place in VAT in obesity establishing a link between inflammation and a higher risk for the development of metabolic diseases. PMID:25118997

Catalán, Victoria; Gómez-Ambrosi, Javier; Rodríguez, Amaia; Ramírez, Beatriz; Andrada, Patricia; Rotellar, Fernando; Valentí, Víctor; Moncada, Rafael; Martí, Pablo; Silva, Camilo; Salvador, Javier; Frühbeck, Gema

2014-08-14

163

Repression of GCN5 Histone Acetyltransferase Activity via Bromodomain-Mediated Binding and Phosphorylation by the Ku-DNA-Dependent Protein Kinase Complex  

Microsoft Academic Search

GCN5, a putative transcriptional adapter in humans and yeast, possesses histone acetyltransferase (HAT) activity which has been linked to GCN5's role in transcriptional activation in yeast. In this report, we dem- onstrate a functional interaction between human GCN5 (hGCN5) and the DNA-dependent protein kinase (DNA-PK) holoenzyme. Yeast two-hybrid screening detected an interaction between the bromodomain of hGCN5 and the p70

NICKOLAI A. BARLEV; VLADIMIR POLTORATSKY; TOM OWEN-HUGHES; CAROL YING; LIN LIU; JERRY L. WORKMAN; SHELLEY L. BERGER

164

HemoHIM ameliorates the persistent down-regulation of Th1-like immune responses in fractionated ?-irradiated mice by modulating the IL-12p70-STAT4 signaling pathway.  

PubMed

Whole body irradiated mice appear to experience a down-regulation of the helper T (Th)1-like immune response, and maintain a persistent immunological imbalance. In the current study, we evaluated the effect of HemoHIM (an herbal product made from Angelica Radix, Cnidium officinale , and Paeonia japonica cultivated in Korea) to ameliorate the immunological imbalance induce in fractionated ?-irradiated mice. The mice were exposed to ? rays twice a week (0.5 Gy fractions) for a total dose of 5 Gy, and HemoHIM was administrated orally from 1 week before the first irradiation to 1 week before the final analysis. All experiments were performed 4 and 6 months after their first exposure. HemoHIM ameliorated the Th1- and Th2-related immune responses normally occur in irradiated mice with or without dinitrophenylated keyhole limpet hemocyanin immunization. HemoHIM also restored the natural killer cell activities without changing the percentage of natural killer cells in irradiated mice. Furthermore, the administration of HemoHIM prevented the reduction in levels of interleukin-12p70 in irradiated mice. Finally, we found that HemoHIM enhanced the phosphorylation of signal transducer and activator of transcription (STAT) 4 that was reduced in irradiated mice. Our findings suggest that HemoHIM ameliorates the persistent down-regulation of Th1-like immune responses by modulating the IL-12p70/pSTAT4 signaling pathway. PMID:22439601

Park, Hae-Ran; Jo, Sung-Kee; Choi, Nam-Hee; Jung, Uhee

2012-05-01

165

Mitogen-Activated Protein Kinase-Activated Kinase RSK2 Plays a Role in Innate Immune Responses to Influenza Virus Infection  

Microsoft Academic Search

Viral infections induce signaling pathways in mammalian cells that stimulate innate immune responses and affect cellular processes, such as apoptosis, mitosis, and differentiation. Here, we report that the ribosomal protein S6 kinase alpha 3 (RSK2), which is activated through the \\

Satoshi Kakugawa; Masayuki Shimojima; Hideo Goto; Taisuke Horimoto; Naoki Oshimori; Gabriele Neumann; Tadashi Yamamoto; Yoshihiro Kawaoka

2009-01-01

166

Defective regulation of mitogen-activated protein kinase activity in a 3T3 cell variant mitogenically nonresponsive to tetradecanoyl phorbol acetate.  

PubMed Central

Mitogen-activated protein (MAP) kinase is a serine/threonine-specific protein kinase which is activated in response to various mitogenic agonists (e.g., epidermal growth factor, insulin, and the tumor promoter tetradecanoyl phorbol acetate [TPA]) and requires both threonine and tyrosine phosphorylation for activity. This enzyme has recently been shown to be identical or closely related to pp42, a protein which becomes tyrosine phosphorylated in response to mitogenic stimulation. Neither the kinases which regulate MAP kinase/pp42 nor the in vivo substrates for this enzyme are known. Because MAP MAP kinase is activated and phosphorylated in response both to agents which stimulate tyrosine kinase receptors and to agents which stimulate protein kinase C, a serine/threonine kinase, we have examined the regulation and phosphorylation of this enzyme in 3T3-TNR9 cells, a variant cell line partially defective in protein kinase C-mediated signalling. In this communication, we show that in the 3T3-TNR9 variant cell line, TPA does not cause the characteristically rapid phosphorylation of pp42 or the activation and phosphorylation of MAP kinase. This defective response is not due to the absence of the MAP kinase/pp42 protein itself because both tyrosine phosphorylation of MAP kinase/pp42 and its enzymatic activation could be induced by platelet-derived growth factor in the 3T3-TNR9 cells. Thus, the defect in these variant cells apparently resides in some aspect of the regulation of MAP kinase phosphorylation. Since the 3T3-TNR9 cells are also defective with respect to the TPA-induced increase in ribosomal protein S6 kinase, these in vivo results reinforce the earlier in vitro finding that MAP kinase can regulate S6 kinase activity. These findings suggest a key role for MAP kinase in a kinase cascade cascade involved in the control of cell proliferation. Images PMID:1990261

L'Allemain, G; Sturgill, T W; Weber, M J

1991-01-01

167

S6K1 promotes invasiveness of breast cancer cells in a model of metastasis of triple-negative breast cancer  

PubMed Central

Breast cancer is the second-leading cause of oncology-related death in US women. Of all invasive breast cancers, patients with tumors lacking expression of the estrogen and progesterone hormone receptors and overexpression of human epidermal growth factor receptor 2 have the poorest clinical prognosis. These referred to as triple-negative breast cancer (TNBC) represent an aggressive form of disease that is marked by early-onset metastasis, high tumor recurrence rate, and low overall survival during the first three years post-diagnosis. In this report, we discuss a novel model of early-onset TNBC metastasis to bone and lungs, derived from MDA-MB-231 cells. Breast cancer cells injected intravenously produced rapid, osteolytic metastases in long bones and spines of athymic nude mice, with concurrent metastasis to lungs, liver, and soft tissues. From the bone metastases, we developed a highly metastatic luciferase-tagged cell line variant named MDA-231-LUC Met. In this report, we demonstrate that the Akt/mTOR/S6K1 axis is hyperactivated in these cells, leading to a dramatic increase in phosphorylation of S6 ribosomal protein at Ser235/236. Lastly, we provide evidence that inhibition of the furthest downstream kinase in the mTOR pathway, S6K1, with a highly specific inhibitor PF-4708671 inhibits cell migration, and thus may provide a potent anti-metastatic adjuvant therapy approach. PMID:25075253

Khotskaya, Yekaterina B; Goverdhan, Aarthi; Shen, Jia; Ponz-Sarvise, Mariano; Chang, Shih-Shin; Hsu, Ming-Chuan; Wei, Yongkun; Xia, Weiya; Yu, Dihua; Hung, Mien-Chie

2014-01-01

168

Phosphorylated S6 as an immunohistochemical biomarker of vulvar intraepithelial neoplasia.  

PubMed

As life expectancy lengthens, cases of non-viral-associated vulvar squamous cell carcinoma and its precursor lesion, so-called differentiated vulvar intraepithelial neoplasia (VIN), continue to increase in frequency. Differentiated VIN often is difficult to recognize and failure to detect it before invasion results in morbidity and mortality. Thus, identification of a reliable biomarker for this type of lesion would be of great clinical benefit. Our recent studies have identified activation (ser235/236 phosphorylation) of ribosomal protein S6 (p-S6) in basal epithelial cells as an event that precedes and accompanies laminin ?(2) overexpression in most preinvasive oral dysplasias. To test this as a potential biomarker of vulvar dysplasia, we immunostained seven differentiated VINs and nine papillomavirus-related 'classic' VINs, most of which were associated with carcinoma, for p-S6. All carcinomas, all differentiated VINs, and most classic VINs contained regions of p-S6 staining in the basal layer, whereas basal and parabasal cells of normal vulvar epithelium and hyperplastic and inflamed lesions lacking cellular atypia were p-S6 negative. Laminin ?(2) was expressed in a subset of VINs, always occurring within basal p-S6 positive regions, as we had found previously for oral dysplasias. Lichen sclerosus is considered a potential precursor of vulvar carcinoma. Two lichen sclerosus lesions of patients with a concurrent carcinoma and one of six lichen sclerosus lesions without atypia or known concurrent carcinoma were basal p-S6 positive. In summary, there is a distinct difference in p-S6 basal cell layer staining between benign and neoplastic vulvar squamous epithelium, with consistent staining of differentiated VIN and of some lichen sclerosus lesions. These results support further studies to assess the potential of p-S6 as a biomarker to identify vulvar lesions at risk of progressing to invasive cancer. PMID:23765247

Pinto, Alvaro P; Degen, Martin; Barron, Patricia; Crum, Christopher P; Rheinwald, James G

2013-11-01

169

Electronic Structure and Phase Transition in Ferroelectic Sn2P2S6 Crystal  

PubMed Central

An analysis of the P2S6 cluster electronic structure and its comparison with the crystal valence band in the paraelectric and ferroelectric phases has been done by first-principles calculations for Sn2P2S6 ferroelectrics. The origin of ferroelectricity has been outlined. It was established that the spontaneous polarization follows from the stereochemical activity of the electron lone pair of tin cations, which is determined by hybridization with P2S6 molecular orbitals. The chemical bonds covalence increase and rearrangement are related to the valence band changes at transition from the paraelectric phase to the ferroelectric phase. PMID:23203069

Glukhov, Konstantin; Fedyo, Kristina; Banys, Juras; Vysochanskii, Yulian

2012-01-01

170

Substrates of Mitotic Kinases  

NSDL National Science Digital Library

Most signaling pathways in cells involve numerous phosphorylation reactions. Some of the rules for kinase-substrate specificity are known, but a complete description of all substrates is missing. Research published in Science Signaling addresses the process of mitosis and asks how the relevant kinases recognize substrate sequence motifs and, in the cellular context, what substrates are phosphorylated and where. The results increase our molecular understanding of how individual events are coordinated during the process of cell division and show the importance of both sequence epitopes for kinase specificity and the notion of a sense of place through localization in subcellular compartments.

Louise N. Johnson (University of Oxford; Department of Biochemistry REV)

2011-06-28

171

Phosphorylation of ribosomal protein S6 confers PARP inhibitor resistance in BRCA1-deficient cancers  

PubMed Central

Inhibition of poly(ADP-ribose) polymerase (PARP) is a promising therapeutic strategy for BRCA1 deficient cancers, however, the development of drug resistance limits clinical efficacy. Previously we found that the BRCA1-AKT1 pathway contributes to tumorigenesis and that the AKT1/mTOR is a novel therapeutic target for BRCA1-deficient cancers. Here, we report that phosphorylation of ribosomal protein S6, a mTOR downstream effector, is greatly increased in BRCA1 deficient cells resistant to PARP inhibition. Phosphorylation of S6 is associated with DNA damage and repair signaling during PARP inhibitor treatment. In BRCA1 deficient cells, expression of S6 lacking all five phosphorylatable sites renders the cells sensitive to PARP inhibitor and increases DNA damage signals. In addition, the S6 mutations reduce tumor formation induced by Brca1-deficiency in mice. Inhibition of S6 phosphorylation by rapamycin restores PARP sensitivity to resistant cells. Combined treatment with rapamycin and PARP inhibitor effectively suppresses BRCA1-deficient tumor growth in mice. These results provide evidence for a novel mechanism by which BRCA1 deficient cancers acquire drug resistance and suggest a new therapeutic strategy to circumvent resistance. PMID:24831086

Xiang, Tao; Chen, Qianming; Pandita, Tej K.; Huang, Yuping; Hu, Mickey C.T.; Yang, Qin

2014-01-01

172

Phosphoinositide 3-kinase C2alpha is activated upon smooth muscle cell migration and regulated by alpha(v)beta(3) integrin engagement.  

PubMed

The involvement of phosphoinositide 3-kinase C2alpha in vascular smooth muscle cell migration was investigated. Products of phosphoinositide 3-kinase, phosphatidylinositol-3-phosphate, and phosphatidylinositol-3,4-bis-phosphate were increased upon smooth muscle cell migration but their synthesis was affected only partially by phosphoinositide 3-kinase inhibitors, wortmannin and LY-294002. Using specific antibody, we showed that the wortmannin/LY-294002 poorly sensitive phosphoinositide 3-kinase C2alpha is expressed in smooth muscle cells. Measurement of phosphoinositide 3-kinase C2alpha activity in vitro, after immunoprecipitation, clearly demonstrated its activation upon smooth muscle cell migration. Moreover, for the first time, phosphoinositide 3-kinase C2alpha was found to be differentially regulated by alpha(v)beta(3) and alpha(v)beta(5) integrin engagement. Finally, we have identified two new potential phosphoinositide 3-kinase C2alpha-binding proteins, p70 and p110, which both may be tyrosine phosphorylated. Thus, phosphoinositide 3-kinase C2alpha might represent a new regulatory pathway of cell migration downstream of integrin engagement. PMID:12237112

Paulhe, Frédérique; Perret, Bertrand; Chap, Hugues; Iberg, Niggi; Morand, Olivier; Racaud-Sultan, Claire

2002-09-20

173

Activity-based kinase profiling of approved tyrosine kinase inhibitors.  

PubMed

The specificities of nine approved tyrosine kinase inhibitors (imatinib, dasatinib, nilotinib, gefitinib, erlotinib, lapatinib, sorafenib, sunitinib, and pazopanib) were determined by activity-based kinase profiling using a large panel of human recombinant active kinases. This panel consisted of 79 tyrosine kinases, 199 serine/threonine kinases, three lipid kinases, and 29 disease-relevant mutant kinases. Many potential targets of each inhibitor were identified by kinase profiling at the K(m) for ATP. In addition, profiling at a physiological ATP concentration (1 mm) was carried out, and the IC(50) values of the inhibitors against each kinase were compared with the estimated plasma-free concentration (calculated from published pharmacokinetic parameters of plasma C(trough) and C(max) values). This analysis revealed that the approved kinase inhibitors were well optimized for their target kinases. This profiling also implicates activity at particular off-target kinases in drug side effects. Thus, large-scale kinase profiling at both K(m) and physiological ATP concentrations could be useful in characterizing the targets and off-targets of kinase inhibitors. PMID:23279183

Kitagawa, Daisuke; Yokota, Koichi; Gouda, Masaki; Narumi, Yugo; Ohmoto, Hiroshi; Nishiwaki, Eiji; Akita, Kensaku; Kirii, Yasuyuki

2013-02-01

174

Ponderosa pine Current Figure S6a. Projected habitat of ponderosa pine (Pinus ponderosa Douglas ex Lawson & C.  

E-print Network

Ponderosa pine ­ Current Figure S6a. Projected habitat of ponderosa pine (Pinus ponderosa Figure S6d. Projected habitat of ponderosa pine (Pinus ponderosa) for the 2071­2100 normal period-2006 Recent Average1961-1990 Climate Normal #12;Ponderosa Pine ­ 2020s Figure S6b

Hamann, Andreas

175

Activation and function of the MAPKs and their substrates, the MAPK-activated protein kinases.  

PubMed

The mitogen-activated protein kinases (MAPKs) regulate diverse cellular programs by relaying extracellular signals to intracellular responses. In mammals, there are more than a dozen MAPK enzymes that coordinately regulate cell proliferation, differentiation, motility, and survival. The best known are the conventional MAPKs, which include the extracellular signal-regulated kinases 1 and 2 (ERK1/2), c-Jun amino-terminal kinases 1 to 3 (JNK1 to -3), p38 (?, ?, ?, and ?), and ERK5 families. There are additional, atypical MAPK enzymes, including ERK3/4, ERK7/8, and Nemo-like kinase (NLK), which have distinct regulation and functions. Together, the MAPKs regulate a large number of substrates, including members of a family of protein Ser/Thr kinases termed MAPK-activated protein kinases (MAPKAPKs). The MAPKAPKs are related enzymes that respond to extracellular stimulation through direct MAPK-dependent activation loop phosphorylation and kinase activation. There are five MAPKAPK subfamilies: the p90 ribosomal S6 kinase (RSK), the mitogen- and stress-activated kinase (MSK), the MAPK-interacting kinase (MNK), the MAPK-activated protein kinase 2/3 (MK2/3), and MK5 (also known as p38-regulated/activated protein kinase [PRAK]). These enzymes have diverse biological functions, including regulation of nucleosome and gene expression, mRNA stability and translation, and cell proliferation and survival. Here we review the mechanisms of MAPKAPK activation by the different MAPKs and discuss their physiological roles based on established substrates and recent discoveries. PMID:21372320

Cargnello, Marie; Roux, Philippe P

2011-03-01

176

Activation and Function of the MAPKs and Their Substrates, the MAPK-Activated Protein Kinases  

PubMed Central

Summary: The mitogen-activated protein kinases (MAPKs) regulate diverse cellular programs by relaying extracellular signals to intracellular responses. In mammals, there are more than a dozen MAPK enzymes that coordinately regulate cell proliferation, differentiation, motility, and survival. The best known are the conventional MAPKs, which include the extracellular signal-regulated kinases 1 and 2 (ERK1/2), c-Jun amino-terminal kinases 1 to 3 (JNK1 to -3), p38 (?, ?, ?, and ?), and ERK5 families. There are additional, atypical MAPK enzymes, including ERK3/4, ERK7/8, and Nemo-like kinase (NLK), which have distinct regulation and functions. Together, the MAPKs regulate a large number of substrates, including members of a family of protein Ser/Thr kinases termed MAPK-activated protein kinases (MAPKAPKs). The MAPKAPKs are related enzymes that respond to extracellular stimulation through direct MAPK-dependent activation loop phosphorylation and kinase activation. There are five MAPKAPK subfamilies: the p90 ribosomal S6 kinase (RSK), the mitogen- and stress-activated kinase (MSK), the MAPK-interacting kinase (MNK), the MAPK-activated protein kinase 2/3 (MK2/3), and MK5 (also known as p38-regulated/activated protein kinase [PRAK]). These enzymes have diverse biological functions, including regulation of nucleosome and gene expression, mRNA stability and translation, and cell proliferation and survival. Here we review the mechanisms of MAPKAPK activation by the different MAPKs and discuss their physiological roles based on established substrates and recent discoveries. PMID:21372320

Cargnello, Marie; Roux, Philippe P.

2011-01-01

177

Orphan kinases turn eccentric  

PubMed Central

PCTAIRE kinases (PCTK) are a highly conserved, but poorly characterized, subgroup of cyclin-dependent kinases (CDK). They are characterized by a conserved catalytic domain flanked by N- and C-terminal extensions that are involved in cyclin binding. Vertebrate genomes contain three highly similar PCTAIRE kinases (PCTK1,2,3, a.k.a., CDK16,17,18), which are most abundant in post-mitotic cells in brain and testis. Consistent with this restricted expression pattern, PCTK1 (CDK16) has recently been shown to be essential for spermatogenesis. PCTAIREs are activated by cyclin Y (CCNY), a highly conserved single cyclin fold protein. By binding to N-myristoylated CCNY, CDK16 is targeted to the plasma membrane. Unlike conventional cyclin-CDK interactions, binding of CCNY to CDK16 not only requires the catalytic domain, but also domains within the N-terminal extension. Interestingly, phosphorylation within this domain blocks CCNY binding, providing a novel means of cyclin-CDK regulation. By using these functional characteristics, we analyzed “PCTAIRE” sequence containing protein kinase genes in genomes of various organisms and found that CCNY and CCNY-dependent kinases are restricted to eumetazoa and possibly evolved along with development of a central nervous system. Here, we focus on the structure and regulation of PCTAIREs and discuss their established functions. PMID:22895054

Mikolcevic, Petra; Rainer, Johannes; Geley, Stephan

2012-01-01

178

Antinociceptive activity of (-)-(2S,6S)-(6-ethyl-tetrahydropyran-2-yl)-formic acid on acute pain in mice.  

PubMed

Pain is a major cause of distress, both physical and psychological. There is a continuous search for new pharmacologically active analgesic agents with minor adverse effects. Recently, the synthesis of (-)-(2S,6S)-(6-ethyl-tetrahydropyran-2-yl)-formic acid [tetrahydropyran derivative (TD)] was described. The objective of this study was to investigate antinociceptive effects of TD. Its activity was compared with the activity of morphine. The effects of TD and morphine were evaluated in models of inflammatory and noninflammatory pain. TD (6-1200 ?mol/kg, intraperitoneally) significantly reduced the nociceptive effects induced by acetic acid or formalin in mice. TD also demonstrated an antinociceptive effect in the tail-flick and hot-plate model. The opioid receptor antagonist, naloxone (at 15 ?mol/kg, intraperitoneally), reversed the antinociceptive activity of TD in all the models evaluated. Morphine and TD induced tolerance in mice. However, the onset of tolerance to TD was delayed compared with that induced by morphine. These results indicate that TD develops significant antinociceptive activity and, at least part of its effects seems to be mediated by the opioid system. PMID:21562408

Marinho, Bruno Guimarães; Miranda, Leandro S M; Meireles, Bruno A; Vasconcellos, Mário L A A; Matheus, Maria E; Pereira, Vera L P; Fernandes, Patricia D

2011-09-01

179

A&S 6/28/12 Form E-1-A for Boston College Undergraduate Programs  

E-print Network

in other disciplines in the liberal arts (literature, theology, music, dance, philosophy) and to applyA&S 6/28/12 Form E-1-A for Boston College Undergraduate Programs Program: Art History 1) Have of art in its entirety from pre-history to the present. 2) Ability to identify the medium, chronological

Huang, Jianyu

180

Drug Design: Protein Kinases  

NSDL National Science Digital Library

In this activity, by the Concord Consortium's Molecular Literacy project, students "review protein structure and hydrophilic/phobic interactions, and then study kinases, small proteins that regulate numerous cell processes." The activity itself is a java-based interactive resource built upon the free, open source Molecular Workbench software. In the activity, students are allowed to explore at their own pace in a digital environment of demonstrations and simulations which allow them to print reports of data captured. There are six pages: an Introduction, Inter/intramolecular attractions: Types of Bonds, Inter/intramolecular attractions: Hydrophobic Interactions, Inter/intramolecular attractions: Hydrophilic Interactions, Protein Kinase Example: Tertiary Structure, and Protein Kinase Example: Ligand Bonding and Drug Design.

181

Secreted protein kinases  

PubMed Central

Protein kinases constitute one of the largest gene families and they control many aspects of cellular life. In retrospect, the first indication for their existence was reported 130 years ago when the secreted protein, casein, was shown to contain phosphate. Despite its identification as the first phosphoprotein, the responsible kinase has remained obscure. This conundrum was solved with the discovery of a novel family of atypical protein kinases that are secreted and appear to phosphorylate numerous extracellular proteins, including casein. Fam20C, the archetypical member, phosphorylates secreted proteins within Ser-x-Glu/pSer motifs. This discovery has solved a 130-year-old mystery and has shed light on several human disorders of biomineralization. PMID:23276407

Tagliabracci, Vincent S.; Pinna, Lorenzo A.; Dixon, Jack E.

2013-01-01

182

Venus Kinase Receptors: Prospects in Signaling and Biological Functions of These Invertebrate Kinases  

PubMed Central

Venus kinase receptors (VKRs) form a family of invertebrate receptor tyrosine kinases (RTKs) initially discovered in the parasitic platyhelminth Schistosoma mansoni. VKRs are single transmembrane receptors that contain an extracellular venus fly trap structure similar to the ligand-binding domain of G protein-coupled receptors of class C, and an intracellular tyrosine kinase domain close to that of insulin receptors. VKRs are found in a large variety of invertebrates from cnidarians to echinoderms and are highly expressed in larval stages and in gonads, suggesting a role of these proteins in embryonic and larval development as well as in reproduction. VKR gene silencing could demonstrate the function of these receptors in oogenesis as well as in spermatogenesis in S. mansoni. VKRs are activated by amino acids and are highly responsive to arginine. As many other RTKs, they form dimers when activated by ligands and induce intracellular pathways involved in protein synthesis and cellular growth, such as MAPK and PI3K/Akt/S6K pathways. VKRs are not present in vertebrates or in some invertebrate species. Questions remain open about the origin of this little-known RTK family in evolution and its role in emergence and specialization of Metazoa. What is the meaning of maintenance or loss of VKR in some phyla or species in terms of development and physiological functions? The presence of VKRs in invertebrates of economical and medical importance, such as pests, vectors of pathogens, and platyhelminth parasites, and the implication of these RTKs in gametogenesis and reproduction processes are valuable reasons to consider VKRs as interesting targets in new programs for eradication/control of pests and infectious diseases, with the main advantage in the case of parasite targeting that VKR counterparts are absent from the vertebrate host kinase panel. PMID:24860549

Dissous, Colette; Morel, Marion; Vanderstraete, Mathieu

2014-01-01

183

Nucleoside diphosphate kinase as protein histidine kinase.  

PubMed

Like phosphorylation of serine, threonine, and tyrosine residues in many organisms, reversible histidine phosphorylation is a well-known regulatory signal in prokaryotes and lower eukaryotes. In vertebrates, phosphohistidine has been mainly described as a phosphorylated intermediate in enzymatic reactions, and it was believed that regulatory histidine phosphorylation is of minor importance. During the last decade, it became evident however, that nucleoside diphosphate kinase (NDPK), an ubiquitously expressed enzyme required for nucleotide homeostasis, can additionally act as a protein histidine kinase. Especially for the isoform NDPK B, at least three defined substrates, the ? subunit of heterotrimeric G proteins (G?), the intermediate conductance potassium channel KCa3.1, and the Ca(2+)-conducting TRP channel family member, TRPV5, have been identified. In all three proteins, the phosphorylation of a specific histidine residue is of regulatory importance for protein function, and these phosphohistidines are cleaved by a counteracting 14 kDa phosphohistidine phosphatase (PHP). This article will therefore give an overview of our current knowledge on protein histidine phosphorylation in prokaryotes and lower eukaryotes and compare it with the regulatory phosphorylation and dephosphorylation of histidine residues in vertebrates by NDPK and PHP, respectively. PMID:24961462

Attwood, Paul V; Wieland, Thomas

2015-02-01

184

Identification of a Dual Specificity Kinase That Activates the Jun Kinases and p38-Mpk2  

Microsoft Academic Search

One Ras-dependent protein kinase cascade leading from growth factor receptors to the ERK (extracellular signal-regulated kinases) subgroup of mitogen-activated protein kinases (MAPKs) is dependent on the protein kinase Raf-1, which activates the MEK (MAPK or ERK kinase) dual specificity kinases. A second protein kinase cascade leading to activation of the Jun kinases (JNKs) is dependent on MEKK (MEK kinase). A

Anning Lin; Audrey Minden; Horacio Martinetto; Francois-Xavier Claret; Carol Lange-Carter; Frank Mercurio; Gary L. Johnson; Michael Karin

1995-01-01

185

Static properties of the S=1 one-dimensional antiferromagnet AgVP2S6  

NASA Astrophysics Data System (ADS)

NMR frequency shift has been measured at 51V and 31P sites in a single crystal of the one-dimensional spin-1 antiferromagnet AgVP2S6. Parameters in the single-ion spin Hamiltonian were determined from the orbital (van Vleck) shift at V sites. Temperature dependence of the spin shift (spin susceptibility) is consistent with the theoretical prediction and the magnitude of the Haldane gap determined from neutron-scattering experiments.

Takigawa, M.; Asano, T.; Ajiro, Y.; Mekata, M.

1995-11-01

186

Distinct subdomains of the KCNQ1 S6 segment determine channel modulation by different KCNE subunits.  

PubMed

Modulation of voltage-gated potassium (KV) channels by the KCNE family of single transmembrane proteins has physiological and pathophysiological importance. All five KCNE proteins (KCNE1-KCNE5) have been demonstrated to modulate heterologously expressed KCNQ1 (KV7.1) with diverse effects, making this channel a valuable experimental platform for elucidating structure-function relationships and mechanistic differences among members of this intriguing group of accessory subunits. Here, we specifically investigated the determinants of KCNQ1 inhibition by KCNE4, the least well-studied KCNE protein. In CHO-K1 cells, KCNQ1, but not KCNQ4, is strongly inhibited by coexpression with KCNE4. By studying KCNQ1-KCNQ4 chimeras, we identified two adjacent residues (K326 and T327) within the extracellular end of the KCNQ1 S6 segment that determine inhibition of KCNQ1 by KCNE4. This dipeptide motif is distinct from neighboring S6 sequences that enable modulation by KCNE1 and KCNE3. Conversely, S6 mutations (S338C and F340C) that alter KCNE1 and KCNE3 effects on KCNQ1 do not abrogate KCNE4 inhibition. Further, KCNQ1-KCNQ4 chimeras that exhibited resistance to the inhibitory effects of KCNE4 still interact biochemically with this protein, implying that accessory subunit binding alone is not sufficient for channel modulation. These observations indicate that the diverse functional effects observed for KCNE proteins depend, in part, on structures intrinsic to the pore-forming subunit, and that distinct S6 subdomains determine KCNQ1 responses to KCNE1, KCNE3, and KCNE4. PMID:19687231

Vanoye, Carlos G; Welch, Richard C; Daniels, Melissa A; Manderfield, Lauren J; Tapper, Andrew R; Sanders, Charles R; George, Alfred L

2009-09-01

187

On J-parallel totally real three-dimensional submanifolds of S6(1)  

NASA Astrophysics Data System (ADS)

In this paper, we study totally real submanifolds of the nearly Kähler six-dimensional unit sphere. Since in this case also, parallel submanifolds are totally geodesic, we introduce a weaker condition, namely that for any tangent vector v <(?h)(v,v,v),Jv>=0. We obtain a complete classification of totally real three-dimensional submanifolds of S6(1) satisfying the above condition.

Djori?, Mirjana; Vrancken, Luc

2010-02-01

188

EFFET STARK DES NIVEAUX DE LA CONFIGURATION 6s6d DU MERCURE  

E-print Network

293 EFFET STARK DES NIVEAUX DE LA CONFIGURATION 6s6d DU MERCURE M. CHANTEPIE Laboratoire de avons présenté un certain nombre de résultats expérimentaux concernant l'effet Stark des niveaux 6 3D3Di. L'interprétation théorique des résultats montre que l'effet Stark de ces niveaux est

Paris-Sud XI, Université de

189

Growth of aligned Mo6S6 nanowires on a Cu(111)  

NASA Astrophysics Data System (ADS)

We report the possibility of using the Cu(111) surface for growing molybdenum sulfide nanowire (Mo6S6) based on density functional theory and scanning tunneling microscopy investigations [1]. A small lattice mismatch between the nanowires and strong substrate interactions lead to epitaxial growth of the nanowires at alignment with the substrate crystallographic axes and at a preferred inter-wire separation.[4pt] [1] Duy Le, Dezheng Sun, Wenhao Lu, Maral Aminpour, Chen Wang, Quan Ma, Talat S. Rahman, Ludwig Bartels

Aminpour, Maral; Le, Duy; Sun, Dezheng; Lu, Wenhao; Wang, Chen; Ma, Quan; Bartels, Ludwig; Rahman, Talat S.

2013-03-01

190

Elastic properties of (Pb y Sn1- y )2P2S6 solid solutions  

NASA Astrophysics Data System (ADS)

Elastic properties of (Pb y Sn1- y )2P2S6 solid solutions were studied using Brillouin scattering technique. Different scattering geometries were used for sound velocities determination that make it possible to find all components of the stiffness tensor. The concentration dependencies of volume compressibility, the Grüneisen parameter and Debye temperature were investigated. The results obtained were used to analyze chemical bonding with substitution of tin by lead at room temperature in the crystals under consideration.

Bilanych, Rostyslav M.; Yevych, Ruslan M.; Kohutych, Anton A.; Perechinskii, Sergij I.; Stoika, Ivan M.; Vysochanskii, Yulian M.

2014-09-01

191

Oncoprotein protein kinase  

DOEpatents

An isolated polypeptide (JNK) characterized by having a molecular weight of 46kD as determined by reducing SDS-PAGE, having serine and threonine kinase activity, phosphorylating the c-Jun N-terminal activation domain and polynucleotide sequences and method of detection of JNK are provided herein. JNK phosphorylates c-Jun N-terminal activation domain which affects gene expression from AP-1 sites.

Karin, Michael (2565 Chalcedony, San Diego, CA 92122); Hibi, Masahiko (7528 Charmant Dr., No. 418, San Diego, CA 92122); Lin, Anning (8655 Via Mallorca Dr., Apt. 93, La Jolla, CA 92093)

1997-01-01

192

Oncoprotein protein kinase  

DOEpatents

An isolated polypeptide (JNK) characterized by having a molecular weight of 46 kD as determined by reducing SDS-PAGE is disclosed. The polypeptide has serine and threonine kinase activity, phosphorylating the c-Jun N-terminal activation domain and polynucleotide sequences. The method of detection of JNK is also provided. JNK phosphorylates c-Jun N-terminal activation domain which affects gene expression from AP-1 sites. 44 figs.

Karin, M.; Hibi, M.; Lin, A.

1997-02-25

193

S6:S18 ribosomal protein complex interacts with a structural motif present in its own mRNA  

PubMed Central

Prokaryotic ribosomal protein genes are typically grouped within highly conserved operons. In many cases, one or more of the encoded proteins not only bind to a specific site in the ribosomal RNA, but also to a motif localized within their own mRNA, and thereby regulate expression of the operon. In this study, we computationally predicted an RNA motif present in many bacterial phyla within the 5? untranslated region of operons encoding ribosomal proteins S6 and S18. We demonstrated that the S6:S18 complex binds to this motif, which we hereafter refer to as the S6:S18 complex-binding motif (S6S18CBM). This motif is a conserved CCG sequence presented in a bulge flanked by a stem and a hairpin structure. A similar structure containing a CCG trinucleotide forms the S6:S18 complex binding site in 16S ribosomal RNA. We have constructed a 3D structural model of a S6:S18 complex with S6S18CBM, which suggests that the CCG trinucleotide in a specific structural context may be specifically recognized by the S18 protein. This prediction was supported by site-directed mutagenesis of both RNA and protein components. These results provide a molecular basis for understanding protein-RNA recognition and suggest that the S6S18CBM is involved in an auto-regulatory mechanism. PMID:23980204

Matelska, Dorota; Purta, Elzbieta; Panek, Sylwia; Boniecki, Michal J.; Bujnicki, Janusz M.; Dunin-Horkawicz, Stanislaw

2013-01-01

194

Erlotinib antagonizes constitutive activation of SRC family kinases and mTOR in acute myeloid leukemia.  

PubMed

Tyrosine kinases such as SRC family kinases (SFKs) as well as the mammalian target of rapamycin (mTOR) serine/threonine kinase are often constitutively activated in acute myeloid leukemia (AML) and hence constitute potential therapeutic targets. Here we demonstrate that the epidermal growth factor receptor (EGFR) inhibitor erlotinib, which has previously been shown to mediate antiproliferative/cytotoxic off-target effects in myelodysplastic syndrome (MDS) and AML blasts, reduces SFK overactivation. Erlotinib induced an arrest in the G 1 phase of the cell cycle that, in cells with constitutive SFK activation, could be recapitulated by chemical inhibition of SFKs with 3-(4-chlorophenyl)1-(1,1-dimethylethyl)-1H-pyrazolo[3,4-?]pyrimidin-4-amine (PP2). Moreover, erlotinib inhibited the phosphorylation of mTOR targets like p70 (SK6) , stimulated the maturation of the autophagic marker LC3 and promoted the formation of autophagosomes. Notably, PP2 and the mTOR inhibitor rapamycin had a similar cell cycle-arresting activity to erlotinib, but neither of these compounds alone induced significant levels of cell death. Altogether, these results suggest that the therapeutic off-target effect of erlotinib may be linked to, yet cannot be entirely explained by, the inhibition of oncogenic signaling via SFKs and mTOR. Thus, combination therapies with erlotinib and rapamycin might be beneficial for MDS and AML patients. PMID:21897118

Boehrer, Simone; Galluzzi, Lorenzo; Lainey, Elodie; Bouteloup, Cyrielle; Tailler, Maximilien; Harper, Francis; Pierron, Gérard; Adès, Lionel; Thépot, Sylvain; Sébert, Marie; Gardin, Claude; de Botton, Stéphane; Fenaux, Pierre; Kroemer, Guido

2011-09-15

195

Reduced Ribosomal Protein S6 Phosphorylation following Progressive Resistance Exercise in Growing Adolescent Rats  

PubMed Central

The purpose of the present study was to investigate moderate intensity progressive resistance exercise (PRE) in growing adolescent rats and its effect on muscle hypertrophy (defined as an increase in fiber cross-sectional area). We hypothesized that in adolescent animals moderate intensity PRE would increase: 1) fiber cross-sectional area (CSA); 2) myosin heavy chain (MyHC) content; and 3) expression and phosphorylation of cell signaling molecules involved in translational regulation, compared to age-matched sedentary controls (SED). In the PRE group, three-week old male rats were trained to climb a vertical ladder as a mode of PRE training such that by 10 weeks, all animals in the PRE group had progressed to carry an additional 80% of body weight per climb. In agreement with our hypotheses, we observed that 10 weeks of moderate PRE in adolescent animals was sufficient to increase CSA of muscle fibers and increase MyHC content. Average muscle fiber CSA increased by greater than 10% and total MyHC content increased by 35% (p<0.05) in the PRE group compared to SED animals. Concurrently, we investigated sustained changes in the expression and phosphorylation of key signaling molecules that are previously identified regulators of hypertrophy in adult animal models. Contrary to our hypotheses, expression and phosphorylation of the translational regulators mTOR and Akt were not increased in the PRE group. In addition, we observed that the ratio of phosphorylated-to-unphosphorylated ribosomal protein S6 (rpS6) was reduced over six-fold in PRE animals (p<0.05) and total rpS6 protein levels were unchanged between PRE and sedentary animals (p>0.05). We conclude that moderate intensity PRE is sufficient to induce muscle hypertrophy in adolescent animals while the signaling mechanisms associated with muscle hypertrophy may differ between growing adolescents and adults. PMID:22614147

Hellyer, Nathan J.; Nokleby, Jessica J.; Thicke, Bethany M.; Zhan, Wen-Zhi; Sieck, Gary C.; Mantilla, Carlos B.

2011-01-01

196

Reduced ribosomal protein s6 phosphorylation after progressive resistance exercise in growing adolescent rats.  

PubMed

The purpose of this study was to investigate moderate intensity progressive resistance exercise (PRE) in growing adolescent rats and its effect on muscle hypertrophy (defined as an increase in fiber cross-sectional area [CSA]). We hypothesized that in adolescent animals moderate intensity PRE would increase (a) fiber CSA; (b) myosin heavy chain (MyHC) content; and (c) expression and phosphorylation of cell signaling molecules involved in translational regulation, compared with that in age-matched sedentary (SED) controls. In the PRE group, 3-week-old male rats were trained to climb a vertical ladder as a mode of PRE training such that by 10 weeks all animals in the PRE group had progressed to carry an additional 80% of their body weight per climb. In agreement with our hypotheses, we observed that 10 weeks of moderate PRE in adolescent animals was sufficient to increase the CSA of muscle fibers and increase MyHC content. The average muscle fiber CSA increased by >10%, and the total MyHC content increased by 35% (p < 0.05) in the PRE group compared with that in the SED animals. Concurrently, we investigated sustained changes in the expression and phosphorylation of key signaling molecules that are previously identified regulators of hypertrophy in adult animal models. Contrary to our hypotheses, expression and phosphorylation of the translational regulators mammalian target of rapamycin and Akt were not increased in the PRE group. In addition, we observed that the ratio of phosphorylated-to-unphosphorylated ribosomal protein S6 (rpS6) was reduced over sixfold in PRE animals (p < 0.05) and that total rpS6 protein levels were unchanged between PRE and SED animals (p > 0.05). We conclude that moderate intensity PRE is sufficient to induce muscle hypertrophy in adolescent animals, whereas the signaling mechanisms associated with muscle hypertrophy may differ between growing adolescents and adults. PMID:22614147

Hellyer, Nathan J; Nokleby, Jessica J; Thicke, Bethany M; Zhan, Wen-Zhi; Sieck, Gary C; Mantilla, Carlos B

2012-06-01

197

FACTEURS DE LAND DES NIVEAUX DE LA CONFIGURATION 6s 6d M. HUET (*)  

E-print Network

facteurs de Lande g. 2. Mesures d'effet Zeeman par interférométrie Fabry-Pérot. - L'analyse de la lumiere 6 configurations 6s 6p et 6s 7s du mercure sont d6jA connues avec une bonne precision, de l'ordre de 10-4, par des puis analys6es avec un inter- f6rom6tre de Fabry-P6rot, plan, a cales fixes, place Article published

Boyer, Edmond

198

Mechanical stretch activates signaling events for protein translation initiation and elongation in C2C12 myoblasts.  

PubMed

It has been proposed that mechanically induced tension is the critical factor in the induction of muscle hypertrophy. However, the molecular mechanisms involved in this process are still under investigation. In the present study, the effect of mechanical stretch on intracellular signaling for protein translation initiation and elongation was studied in C2C12 myoblasts. Cells were grown on a silicone elastomer chamber and subjected to 30-min of 5 or 15% constant static or cyclic (60 cycles/min) uniaxial stretch. Western blot analyses revealed that p70 S6 kinase (p70S6K) and eukaryotic elongation factor 2 (eEF2), which are the markers for translation initiation and peptide chain elongation, respectively, were activated by both static and cyclic stretch. The magnitude of activation was greater in response to the 15% cyclic stretch. Cyclic stretch also increased the phosphorylation of MAP kinases (p38 MAPK, ERK1/2 and JNK). However, the pharmacological inhibition of MAP kinases did not block the stretch-induced activation of p70S6K and eEF2. An inhibitor of the mammalian target of rapamycin (mTOR) blocked the stretch-induced phosphorylation of p70S6K but did not affect the eEF2 activation. A broad-range tyrosine kinase inhibitor, genistein, blocked the stretch-induced activation of p70S6K and eEF2, whereas Src tyrosine kinase and Janus kinase (JAK) inhibitors did not. These results suggest that the stretch-induced activation of protein translation initiation and elongation in mouse myoblast cell lines is mediated by tyrosine kinase(s), except for Src kinase or JAK. PMID:20957453

Nakai, Naoya; Kawano, Fuminori; Oke, Yoshihiko; Nomura, Sachiko; Ohira, Takashi; Fujita, Ryo; Ohira, Yoshinobu

2010-12-01

199

The anti-tumor activator sMEK1 and paclitaxel additively decrease expression of HIF-1? and VEGF via mTORC1-S6K/4E-BP-dependent signaling pathways  

PubMed Central

Recently, we found that sMEK1 effectively regulates pro-apoptotic activity when combined with a traditional chemotherapeutic drug. Therefore, combinational therapeutic strategies targeting critical molecular and cellular mechanisms are urgently required. In this present work, we evaluated whether sMEK1 enhanced the pro-apoptotic activity of chemotherapeutic drugs in ovarian carcinoma cells. Combined with a chemotherapeutic drug, sMEK1 showed an additive effect on the suppression of ovarian cancer cell growth by inducing cell cycle arrest and apoptosis and regulating related gene expression levels or protein activities. In addition, the phosphoinositide-3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway was strongly inhibited by the combined treatment, showing de-repression of the tuberous sclerosis complex (TSC) and suppression of ras homolog enriched in the brain (Rheb) and mTOR and raptor in aggressive ovarian carcinoma cells and mouse xenograft models. Treatment with sMEK1 and paclitaxel reduced phosphorylation of ribosomal S6 kinase (S6K) and 4E-binding protein (4E-BP), two critical downstream targets of the mTOR-signaling pathway. Furthermore, both sMEK1 and paclitaxel significantly inhibited the expression of signaling components downstream of S6K/4E-BP, such as hypoxia-inducible factor-1? (HIF-1?) and vascular endothelial growth factor (VEGF), both in vitro and in vivo. Therefore, our data suggest that the combination of sMEK1 and paclitaxel is a promising and effective targeted therapy for chemotherapy-resistant or recurrent ovarian cancers. PMID:25153728

Byun, Hyun-Jung; Seo, Seung Hee; Lee, Seung-Hoon; Rho, Seung Bae

2014-01-01

200

Tau-tubulin kinase  

PubMed Central

Tau-tubulin kinase (TTBK) belongs to casein kinase superfamily and phosphorylates microtubule-associated protein tau and tubulin. TTBK has two isoforms, TTBK1 and TTBK2, which contain highly homologous catalytic domains but their non-catalytic domains are distinctly different. TTBK1 is expressed specifically in the central nervous system and is involved in phosphorylation and aggregation of tau. TTBK2 is ubiquitously expressed in multiple tissues and genetically linked to spinocerebellar ataxia type 11. TTBK1 directly phosphorylates tau protein, especially at Ser422, and also activates cycline-dependent kinase 5 in a unique mechanism. TTBK1 protein expression is significantly elevated in Alzheimer’s disease (AD) brains, and genetic variations of the TTBK1 gene are associated with late-onset Alzheimer’s disease in two cohorts of Chinese and Spanish populations. TTBK1 transgenic mice harboring the entire 55-kilobase genomic sequence of human TTBK1 show progression of tau accumulation, neuroinflammation, and neurodegeneration when crossed with tau mutant mice. Our recent study shows that there is a striking switch in mononuclear phagocyte and activation phenotypes in the anterior horn of the spinal cord from alternatively activated (M2-skewed) microglia in P301L tau mutant mice to pro-inflammatory (M1-skewed) infiltrating peripheral monocytes by crossing the tau mice with TTBK1 transgenic mice. TTBK1 is responsible for mediating M1-activated microglia-induced neurotoxicity, and its overexpression induces axonal degeneration in vitro. These studies suggest that TTBK1 is an important molecule for the inflammatory axonal degeneration, which may be relevant to the pathobiology of tauopathy including AD. PMID:24808823

Ikezu, Seiko; Ikezu, Tsuneya

2014-01-01

201

The fruit juice of Morinda citrifolia (noni) downregulates HIF-1? protein expression through inhibition of PKB, ERK-1/2, JNK-1 and S6 in manganese-stimulated A549 human lung cancer cells.  

PubMed

High exposure of manganese is suggested to be a risk factor for many lung diseases. Evidence suggests anticancerous and antiangiogenic effects by products derived from Morinda citrifolia (noni) fruit. In this study, we investigated the effect of noni fruit juice (NFJ) on the expression of HIF-1?, a tumor angiogenic transcription factor in manganese-chloride (manganese)-stimulated A549 human lung carcinoma cells. Treatment with manganese largely induced expression of HIF-1? protein but did not affect HIF-1? mRNA expression in A549 cells, suggesting the metal-mediated co- and/or post-translational HIF-1? upregulation. Manganese treatment also led to increased phosphorylation of extracellular-regulated protein kinase-1/2 (ERK-1/2), c-Jun N-terminal kinase-1 (JNK-1), protein kinase B (PKB), S6 and eukaryotic translation initiation factor-2? (eIF-2?) in A549 cells. Of note, the exposure of NFJ inhibited the manganese-induced HIF-1? protein upregulation in a concentration-dependent manner. Importantly, as assessed by results of pharmacological inhibition and siRNA transfection studies, the effect of NFJ on HIF-1? protein downregulation seemed to be largely associated with the ability of NFJ to interfere with the metal's signaling to activate PKB, ERK-1/2, JNK-1 and S6 in A549 cells. It was further shown that NFJ could repress the induction of HIF-1? protein by desferoxamine or interleukin-1? (IL-1?), another HIF-1? inducer in A549 cells. Thus, the present study provides the first evidence that NFJ has the ability to strongly downregulate manganese-induced HIF-1? protein expression in A549 human lung cancer cells, which may suggest the NFJ-mediated beneficial effects on lung pathologies in which manganese and HIF-1? overexpression play pathogenic roles. PMID:22179285

Jang, Byeong-Churl

2012-03-01

202

Phorbol ester, serum, and rous sarcoma virus transforming gene product induce similar phosphorylations of ribosomal protein S6.  

PubMed Central

The addition of phorbol 12-myristate 13-acetate (PMA), a potent tumor promoter, to serum-starved quiescent chicken embryo fibroblasts (CEF) or C127 murine cells resulted in increased phosphorylation of 40S ribosomal protein S6. The effect of PMA on S6 phosphorylation in quiescent CEF was half-maximal at approximately equal to 100 nM and was readily observed at 16 nM. In addition, S6 phosphorylation was increased in serum-starved CEF incubated with the diacylglycerol derivative, 1-oleoyl-2-acetylglycerol. S6 phosphorylation in PMA-stimulated, serum-stimulated, and serum-starved Rous sarcoma virus-transformed CEF was analyzed by phospho amino acid analysis, two-dimensional polyacrylamide gel electrophoresis, limited proteolysis with V8 protease, and two-dimensional thin-layer electrophoresis of chymotryptic digests. Comparison of S6 phosphorylation by these methods suggests that phosphorylation of S6 stimulated by PMA, serum, or oncogenic transformation with Rous sarcoma virus occurs through common pathways. This is further supported by the observation that the simultaneous addition of PMA and serum to CEF or of either PMA or serum to Rous sarcoma virus-transformed CEF did not significantly further increase the incorporation of phosphate into S6. Images PMID:6093101

Blenis, J; Spivack, J G; Erikson, R L

1984-01-01

203

Histidine kinases in plants  

PubMed Central

Two-component signaling pathways involve sensory histidine kinases (HK), histidine phosphotransfer proteins (HpT) and response regulators (RR). Recent advancements in genome sequencing projects for a number of plant species have established the TCS family to be multigenic one. In plants, HKs operate through the His–Asp phosphorelay and control many physiological and developmental processes throughout the lifecycle of plants. Despite the huge diversity reported for the structural features of the HKs, their functional redundancy has also been reported via mutant approach. Several sensory HKs having a CHASE domain, transmembrane domain(s), transmitter domain and receiver domain have been reported to be involved in cytokinin and ethylene signaling. On the other hand, there are also increasing evidences for some of the sensory HKs to be performing their role as osmosensor, clearly indicating toward a possible cross-talk between hormone and stress responsive cascades. In this review, we bring out the latest knowledge about the structure and functions of histidine kinases in cytokinin and ethylene signaling and their role(s) in development and the regulation of environmental stress responses. PMID:22902699

Nongpiur, Ramsong; Soni, Praveen; Karan, Ratna; Singla-Pareek, Sneh L.; Pareek, Ashwani

2012-01-01

204

Hsp90 promotes kinase evolution.  

PubMed

Heat-shock protein 90 (Hsp90) promotes the maturation and stability of its client proteins, including many kinases. In doing so, Hsp90 may allow its clients to accumulate mutations as previously proposed by the capacitor hypothesis. If true, Hsp90 clients should show increased evolutionary rate compared with nonclients; however, other factors, such as gene expression and protein connectivity, may confound or obscure the chaperone's putative contribution. Here, we compared the evolutionary rates of many Hsp90 clients and nonclients in the human protein kinase superfamily. We show that Hsp90 client status promotes evolutionary rate independently of, but in a small magnitude similar to that of gene expression and protein connectivity. Hsp90's effect on kinase evolutionary rate was detected across mammals, specifically relaxing purifying selection. Hsp90 clients also showed increased nucleotide diversity and harbored more damaging variation than nonclient kinases across humans. These results are consistent with the central argument of the capacitor hypothesis that interaction with the chaperone allows its clients to harbor genetic variation. Hsp90 client status is thought to be highly dynamic with as few as one amino acid change rendering a protein dependent on the chaperone. Contrary to this expectation, we found that across protein kinase phylogeny Hsp90 client status tends to be gained, maintained, and shared among closely related kinases. We also infer that the ancestral protein kinase was not an Hsp90 client. Taken together, our results suggest that Hsp90 played an important role in shaping the kinase superfamily. PMID:25246701

Lachowiec, Jennifer; Lemus, Tzitziki; Borenstein, Elhanan; Queitsch, Christine

2015-01-01

205

A diastereoselective route to 2,6-syn-disubstituted tetrahydropyrans: synthesis of the civet compound (+)-2-((2S,6S)-6-methyltetrahydro-2H-pyran-2-yl) acetic acid.  

PubMed

A diastereoselective synthesis of 2,6-syn-disubstituted tetrahydropyrans has been developed based on the ability of furanyl-ether chiral centres to epimerise readily under acidic conditions. This novel methodology was applied to the synthesis of (+)-2-((2S,6S)-6-methyltetrahydro-2H-pyran-2-yl) acetic acid, a component of the African civet cat's glandular marking secretion. PMID:18997951

O'Brien, Matthew; Cahill, Shane; Evans, Lyndsay A

2008-11-21

206

17 CFR 239.16 - Form S-6, for unit investment trusts registered on Form N-8B-2.  

Code of Federal Regulations, 2011 CFR

...S-6, for unit investment trusts registered on Form N-8B-2...239.16 Commodity and Securities Exchanges SECURITIES...registration under the Securities Act of 1933 of securities of any unit investment trust registered under...

2011-04-01

207

17 CFR 239.16 - Form S-6, for unit investment trusts registered on Form N-8B-2.  

...S-6, for unit investment trusts registered on Form N-8B-2...239.16 Commodity and Securities Exchanges SECURITIES...registration under the Securities Act of 1933 of securities of any unit investment trust registered under...

2014-04-01

208

17 CFR 239.16 - Form S-6, for unit investment trusts registered on Form N-8B-2.  

Code of Federal Regulations, 2012 CFR

...S-6, for unit investment trusts registered on Form N-8B-2...239.16 Commodity and Securities Exchanges SECURITIES...registration under the Securities Act of 1933 of securities of any unit investment trust registered under...

2012-04-01

209

17 CFR 239.16 - Form S-6, for unit investment trusts registered on Form N-8B-2.  

Code of Federal Regulations, 2010 CFR

...S-6, for unit investment trusts registered on Form N-8B-2...239.16 Commodity and Securities Exchanges SECURITIES...registration under the Securities Act of 1933 of securities of any unit investment trust registered under...

2010-04-01

210

17 CFR 239.16 - Form S-6, for unit investment trusts registered on Form N-8B-2.  

Code of Federal Regulations, 2013 CFR

...S-6, for unit investment trusts registered on Form N-8B-2...239.16 Commodity and Securities Exchanges SECURITIES...registration under the Securities Act of 1933 of securities of any unit investment trust registered under...

2013-04-01

211

Antigenic reactivity of ribosomal protein S6 and the calcium-binding ATPase inhibitor protein of mammalian mitochondria  

Microsoft Academic Search

Phosphorylation of ribosomal protein S6 of mammals precedes activation of cell growth in numerous biological systems. We have cloned a cDNA for ribosomal protein S6 from T-47D human breast cancer cells by immunoscreening a ?gt11 expression library with antibody raised against the mitochondrial Ca2+-binding ATPase inhibitor protein (CaBI) of bovine heart mitochondria (Yamada & Huzel: J Biol Chem 263: 11498–11503,

C. Gail Penner; Leigh C. Murphy; Norman J. Huzel; Esther W. Yamada

1991-01-01

212

Molecular characterization of the genome segments S4, S6 and S7 of rice gall dwarf virus  

Microsoft Academic Search

Summary  Rice gall dwarf virus (RGDV) is a member of the genus Phytoreovirus within the family Reovirdae. Its genome has 12 segments of double-stranded RNA (dsRNA), of which the nucleotide sequences of segments S4, S6, and S7\\u000a were determined, providing the first complete genome sequence of RGDV. Each of the segments S4, S6, and S7 contained conserved\\u000a terminal sequences conforming to

H. M. Zhang; J. Yang; X. Xin; J. P. Chen; M. J. Adams

2007-01-01

213

Drugging sphingosine kinases.  

PubMed

The transfer of the gamma phosphate from ATP to sphingosine (Sph) to generate a small signaling molecule, sphingosine 1-phosphate (S1P), is catalyzed by sphingosine kinases (SphK), which exist as two isoforms, SphK1 and SphK2. SphK is a key regulator of S1P and the S1P:Sph/ceramide ratio. Increases in S1P levels have been linked to diseases including sickle cell disease, cancer, and fibrosis. Therefore, SphKs are potential targets for drug discovery. However, the current chemical biology toolkit needed to validate these enzymes as drug targets is inadequate. With this review, we survey in vivo active SphK inhibitors and highlight the need for developing more potent and selective inhibitors. PMID:25384187

Santos, Webster L; Lynch, Kevin R

2015-01-16

214

The DAP-kinase interactome.  

PubMed

DAP-kinase (DAPK) is a Ca(2+)/calmodulin regulated Ser/Thr kinase that activates a diverse range of cellular activities. It is subject to multiple layers of regulation involving both intramolecular signaling, and interactions with additional proteins, including other kinases and phosphatases. Its protein stability is modulated by at least three distinct ubiquitin-dependent systems. Like many kinases, DAPK participates in several signaling cascades, by phosphorylating additional kinases such as ZIP-kinase and protein kinase D (PKD), or Pin1, a phospho-directed peptidyl-prolyl isomerase that regulates the function of many phosphorylated proteins. Other substrate targets have more direct cellular effects; for example, phosphorylation of the myosin II regulatory chain and tropomyosin mediate some of DAPK's cytoskeletal functions, including membrane blebbing during cell death and cell motility. DAPK induces distinct death pathways of apoptosis, autophagy and programmed necrosis. Among the substrates implicated in these processes, phosphorylation of PKD, Beclin 1, and the NMDA receptor has been reported. Interestingly, not all cellular effects are mediated by DAPK's catalytic activity. For example, by virtue of protein-protein interactions alone, DAPK activates pyruvate kinase isoform M2, the microtubule affinity regulating kinases and inflammasome protein NLRP3, to promote glycolysis, influence microtubule dynamics, and enhance interleukin-1? production, respectively. In addition, a number of other substrates and interacting proteins have been identified, the physiological significance of which has not yet been established. All of these substrates, effectors and regulators together comprise the DAPK interactome. By presenting the components of the interactome network, this review will clarify both the mechanisms by which DAPK function is regulated, and by which it mediates its various cellular effects. PMID:24220855

Bialik, Shani; Kimchi, Adi

2014-02-01

215

Peptides Targeting Protein Kinases: Strategies and Implications  

NSDL National Science Digital Library

Protein kinases are important key regulators in most, if not all, biological processes and are linked with many human diseases. Protein kinases thus became attractive targets for drug design. Intracellularly active peptides that selectively interfere with kinase function and or kinase-mediated signaling pathways are potential drug compounds with therapeutic implications.

2006-12-01

216

PI 3-kinase, Akt and cell survival  

Microsoft Academic Search

Phosphoinositide 3-OH kinase (PI 3-kinase) provides cells with a survival signal that allows them to withstand apoptotic stimuli. Many tumour cells display elevated levels of PI 3-kinase products as a result of deletion of the phosphatase PTEN, activation of Ras or expression of autocrine growth factors. As a result they are relatively resistant to apoptosis. The mechanisms for PI 3-kinase

Julian Downward

2004-01-01

217

A small molecule–kinase interaction map for clinical kinase inhibitors  

Microsoft Academic Search

Kinase inhibitors show great promise as a new class of therapeutics. Here we describe an efficient way to determine kinase inhibitor specificity by measuring binding of small molecules to the ATP site of kinases. We have profiled 20 kinase inhibitors, including 16 that are approved drugs or in clinical development, against a panel of 119 protein kinases. We find that

Miles A Fabian; William H Biggs III; Daniel K Treiber; Corey E Atteridge; Mihai D Azimioara; Michael G Benedetti; Todd A Carter; Pietro Ciceri; Philip T Edeen; Mark Floyd; Julia M Ford; Margaret Galvin; Jay L Gerlach; Robert M Grotzfeld; Sanna Herrgard; Darren E Insko; Michael A Insko; Andiliy G Lai; Jean-Michel Lélias; Shamal A Mehta; Zdravko V Milanov; Anne Marie Velasco; Lisa M Wodicka; Hitesh K Patel; Patrick P Zarrinkar; David J Lockhart

2005-01-01

218

Tyrosine kinase gene rearrangements in epithelial malignancies  

PubMed Central

Chromosomal rearrangements that lead to oncogenic kinase activation are observed in many epithelial cancers. These cancers express activated fusion kinases that drive the initiation and progression of malignancy, and often have a considerable response to small-molecule kinase inhibitors, which validates these fusion kinases as ‘druggable’ targets. In this Review, we examine the aetiologic, pathogenic and clinical features that are associated with cancers harbouring oncogenic fusion kinases, including anaplastic lymphoma kinase (ALK), ROS1 and RET. We discuss the clinical outcomes with targeted therapies and explore strategies to discover additional kinases that are activated by chromosomal rearrangements in solid tumours. PMID:24132104

Shaw, Alice T.; Hsu, Peggy P.; Awad, Mark M.; Engelman, Jeffrey A.

2014-01-01

219

Neuronal migration and protein kinases  

PubMed Central

The formation of the six-layered structure of the mammalian cortex via the inside-out pattern of neuronal migration is fundamental to neocortical functions. Extracellular cues such as Reelin induce intracellular signaling cascades through the protein phosphorylation. Migrating neurons also have intrinsic machineries to regulate cytoskeletal proteins and adhesion properties. Protein phosphorylation regulates these processes. Moreover, the balance between phosphorylation and dephosphorylation is modified by extracellular cues. Multipolar-bipolar transition, radial glia-guided locomotion and terminal translocation are critical steps of radial migration of cortical pyramidal neurons. Protein kinases such as Cyclin-dependent kinase 5 (Cdk5) and c-Jun N-terminal kinases (JNKs) involve these steps. In this review, I shall give an overview the roles of protein kinases in neuronal migration. PMID:25628530

Ohshima, Toshio

2015-01-01

220

A SiPM-based ZnS:$^6$LiF scintillation neutron detector  

E-print Network

In the work presented here we built and evaluated a single-channel neutron detection unit consisting of a ZnS:$^6$LiF scintillator with embedded WLS fibers readout by a SiPM. The unit has a sensitive volume of 2.4 x 2.8 x 50 mm$^3$; 12 WLS fibers of diameter 0.25 mm are uniformly distributed over this volume and are coupled to a 1 x 1 mm$^2$ active area SiPM. We report the following performance parameters: neutron detection efficiency $\\sim 65\\,$% at $1.2\\,\\AA$, background count rate $< 10^{-3}$ Hz, gamma-sensitivity with $^{60}$Co source $< 10^{-6}$, dead time $\\sim 20\\,\\mu$s, multi-count ratio $< 1\\,$%. All these parameters were achieved up to the SiPM dark count rate of $\\sim 2\\,$MHz. We consider such detection unit as an elementary building block for realization of one-dimensional multichannel detectors for applications in the neutron scattering experimental technique. The dimensions of the unit and the number of embedded fibers can be varied to meet the specific application requirements. The upp...

Stoykov, A; Greuter, U; Hildebrandt, M; Schlumpf, N

2014-01-01

221

Occurrence of Lysophosphatides in Bacteriophage T4rII-Infected Escherichia coli S/6  

PubMed Central

Hydrolysis of phospholipids was observed to start about 15 min after Escherichia coli S/6 cells were infected with T4rII bacteriophage mutants. Hydrolysis continued through the latent period and well past the time when cell lysis occurs. The hydrolytic products that accumulated were free fatty acids, 2-acyl lysophosphatidylethanolamine, and various lysocardiolipins. These products indicated the action of phospholipase A1. From 15 to 22 min after infection, there were equivalent amounts of fatty acids and lysophosphatides in extracts of cellular lipids. Thereafter, free fatty acids were produced in excess. This suggests that lysophospholipase was active at the later time. We also observed a stoichiometric relation between loss of phosphatidylglycerol and increase of cardiolipin plus lysocardiolipins. This continued well past the normal lysis time (25 min). The appearance of lipase activities during the latent period seems to be specific to infection with rII mutants. Neither the wild-type bacteriophage nor rI mutants produced similar activities by 22 min after infection. PMID:5002011

Bradley, W. E. C.; Astrachan, L.

1971-01-01

222

Hsp90 Promotes Kinase Evolution  

PubMed Central

Heat-shock protein 90 (Hsp90) promotes the maturation and stability of its client proteins, including many kinases. In doing so, Hsp90 may allow its clients to accumulate mutations as previously proposed by the capacitor hypothesis. If true, Hsp90 clients should show increased evolutionary rate compared with nonclients; however, other factors, such as gene expression and protein connectivity, may confound or obscure the chaperone’s putative contribution. Here, we compared the evolutionary rates of many Hsp90 clients and nonclients in the human protein kinase superfamily. We show that Hsp90 client status promotes evolutionary rate independently of, but in a small magnitude similar to that of gene expression and protein connectivity. Hsp90’s effect on kinase evolutionary rate was detected across mammals, specifically relaxing purifying selection. Hsp90 clients also showed increased nucleotide diversity and harbored more damaging variation than nonclient kinases across humans. These results are consistent with the central argument of the capacitor hypothesis that interaction with the chaperone allows its clients to harbor genetic variation. Hsp90 client status is thought to be highly dynamic with as few as one amino acid change rendering a protein dependent on the chaperone. Contrary to this expectation, we found that across protein kinase phylogeny Hsp90 client status tends to be gained, maintained, and shared among closely related kinases. We also infer that the ancestral protein kinase was not an Hsp90 client. Taken together, our results suggest that Hsp90 played an important role in shaping the kinase superfamily. PMID:25246701

Lachowiec, Jennifer; Lemus, Tzitziki; Borenstein, Elhanan; Queitsch, Christine

2015-01-01

223

Glucose phosphorylation is required for insulin-dependent mTOR signalling in the heart  

PubMed Central

Objective: Insulin regulates both glucose uptake and postnatal cardiac growth. The anabolic effects of insulin are mediated by the mammalian target of rapamycin (mTOR), an evolutionarily conserved kinase which is also a convergence point between nutrient sensing and cell growth. We postulated that mTOR signalling in the heart requires the metabolism of glucose. Methods: We interrogated the insulin-mediated mTOR signalling pathway in response to different metabolic interventions regulating substrate metabolism in the isolated working rat heart and in isolated cardiomyocytes. Results: Although insulin enhanced Akt activity, phosphorylation of mTOR and its downstream targets (p70S6K and 4EBP1) required the addition of glucose. Glucose-dependent p70S6K phosphorylation was independent of the hexosamine biosynthetic pathway, the AMP kinase pathway, and the pentose phosphate pathway. However, inhibition of glycolysis downstream of hexokinase markedly enhanced p70S6K phosphorylation. Furthermore, 2-deoxyglucose activated p70S6K suggesting that phosphorylation of glucose is required for carbohydrate-mediated mTOR signalling in the heart. Lastly, we also found enhanced p70S6K phosphorylation in the hearts of diabetic rats. Conclusion: Phosphorylation of glucose is necessary for insulin-dependent mTOR activity in the heart, suggesting a link between intermediary metabolism and cardiac growth. PMID:17553476

Sharma, Saumya; Guthrie, Patrick; Chan, Suzanne; Haq, Syed; Taegtmeyer, Heinrich

2008-01-01

224

Priming IKK? kinase for action.  

PubMed

IKK? (I?B kinase ?) is a core component of signalling pathways that control the activation of NF-?B (nuclear factor ?B) transcription factors, which regulate many physiological processes, including cell survival, immunity and DNA-damage responses. Like many kinases, activation of IKK? requires phosphorylation of the activation loop of its kinase domain. Different upstream protein kinases, and IKK? itself, have been reported to directly phosphorylate and activate IKK? in vitro, but the exact molecular mechanism of IKK? activation in cells has remained unclear. In a recent article in the Biochemical Journal, Zhang and co-workers showed that IKK? is activated by two sequential phosphorylations of its activation loop in response to TNF (tumour necrosis factor), IL-1 (interleukin-1) and TLR (Toll-like receptor) ligands. Using a combination of biochemical and genetic approaches, they demonstrate that IKK? is first phosphorylated by the upstream kinase TAK1 [TGF? (transforming growth factor ?)-activated kinase-1] at Ser177, which then serves as a priming signal for subsequent IKK? autophosphorylation at Ser181. This study resolves two apparently conflicting earlier models of IKK? activation into a single unified model, and suggests that the IKK? activation loop may integrate distinct 'upsteam' signals to activate NF-?B. PMID:25195736

Ley, Steven C; Beyaert, Rudi

2014-10-01

225

Functionally distinct PI 3-kinase pathways regulate myelination in the peripheral nervous system.  

PubMed

The PI 3-kinase (PI 3-K) signaling pathway is essential for Schwann cell myelination. Here we have characterized PI 3-K effectors activated during myelination by probing myelinating cultures and developing nerves with an antibody that recognizes phosphorylated substrates for this pathway. We identified a discrete number of phospho-proteins including the S6 ribosomal protein (S6rp), which is down-regulated at the onset of myelination, and N-myc downstream-regulated gene-1 (NDRG1), which is up-regulated strikingly with myelination. We show that type III Neuregulin1 on the axon is the primary activator of S6rp, an effector of mTORC1. In contrast, laminin-2 in the extracellular matrix (ECM), signaling through the ?6?4 integrin and Sgk1 (serum and glucocorticoid-induced kinase 1), drives phosphorylation of NDRG1 in the Cajal bands of the abaxonal compartment. Unexpectedly, mice deficient in ?6?4 integrin signaling or Sgk1 exhibit hypermyelination during development. These results identify functionally and spatially distinct PI 3-K pathways: an early, pro-myelinating pathway driven by axonal Neuregulin1 and a later-acting, laminin-integrin-dependent pathway that negatively regulates myelination. PMID:24687281

Heller, Bradley A; Ghidinelli, Monica; Voelkl, Jakob; Einheber, Steven; Smith, Ryan; Grund, Ethan; Morahan, Grant; Chandler, David; Kalaydjieva, Luba; Giancotti, Filippo; King, Rosalind H; Fejes-Toth, Aniko Naray; Fejes-Toth, Gerard; Feltri, Maria Laura; Lang, Florian; Salzer, James L

2014-03-31

226

Crystal structure of SsfS6, the putative C-glycosyltransferase involved in SF2575 biosynthesis  

PubMed Central

The molecule known as SF2575 from Streptomyces sp. is a tetracycline polyketide natural product that displays antitumor activity against murine leukemia P388 in vivo. In the SF2575 biosynthetic pathway, SsfS6 has been implicated as the crucial C-glycosyltransferase (C-GT) that forms the C-C glycosidic bond between the sugar and the SF2575 tetracycline-like scaffold. Here, we report the crystal structure of SsfS6 in the free form and in complex with TDP, both at 2.4 Å resolution. The structures reveal SsfS6 to adopt a GT-B fold wherein the TDP and docked putative aglycon are consistent with the overall C-glycosylation reaction. As one of only a few existing structures for C-glycosyltransferases, the structures described herein may serve as a guide to better understand and engineer C-glycosylation. PMID:23526584

Wang, Fengbin; Zhou, Maoquan; Singh, Shanteri; Yennamalli, Ragothaman M.; Bingman, Craig A.; Thorson, Jon S.; Phillips, George N.

2014-01-01

227

Oscillator strength measurements of the 5s6s S10?5snp P11 Rydberg transitions of strontium  

NASA Astrophysics Data System (ADS)

We report the experimentally determined oscillator strengths for the 5s6s S10?5snp P11 Rydberg transitions of strontium using two-step excitation in conjunction with a thermionic diode ion detector. The absolute photoionization cross section from the 5s6s S10 excited state has been determined by adjusting the polarization vector of the ionizing laser beam parallel, perpendicular, and at the magic angle with respect to that of the exciting dye laser. The measured absolute value of the photoionization cross section 0.9±0.2Mb at the 5s threshold is used to extract the f values of the 5s6s S10?5snp P11 (26?n?73) Rydberg transitions. The oscillator strength in the discrete region merges smoothly to the oscillator strength density at the ionization threshold.

Haq, S. U.; Kalyar, M. A.; Rafiq, M.; Ali, R.; Piracha, N. K.; Baig, M. A.

2009-04-01

228

Effect of spin ordering on structure and structural transitions in the (MnS)6 magic cluster  

NASA Astrophysics Data System (ADS)

Many manganese-based magnetic materials exhibit exciting technologically important properties (e.g. colossal magnetoresistance, giant magnetocaloric effect) but, as yet, relatively little is known at the nanoscale. Recently, manganese sulfide clusters were produced in a laser ablation experiment, revealing sizes with special stability, i.e. magic clusters. Here, we use density functional calculations to investigate the (MnS)6 magic cluster. Specifically, the interplay between magnetism, structure and energetic stability in nine low lying minima (MnS)6 structures is investigated and rationalized. We further calculate the energetic barriers for interconversion between the two lowest lying (MnS)6 isomers and discuss their possible relevance to premelting cluster dynamics.

Lewoczko, April D.; BelBruno, Joseph J.; Bromley, Stefan T.

2013-01-01

229

A Genome-wide RNAi Screen for Polypeptides that Alter rpS6 Phosphorylation  

PubMed Central

Mammalian target of rapamycin (mTOR) is a giant protein kinase that controls cell proliferation, growth, and metabolism. mTOR is regulated by nutrient availability, by mitogens, and by stress, and operates through two independently regulated hetero-oligomeric complexes. We have attempted to identify the cellular components necessary to maintain the activity of mTOR complex 1 (mTORC1), the amino acid-dependent, rapamycin-inhibitable complex, using a whole genome approach involving RNAi-induced depletion of cellular polypeptides. We have used a pancreatic ductal adenocarcinoma (PDAC) cell line, Mia-PaCa for this screen; as with many pancreatic cancers, these cells exhibit constitutive activation of mTORC1. PDAC is the most common form of pancreatic cancer and the 5-year survival rate remains 3–5% despite current nonspecific and targeted therapies. Although rapamycin-related mTOR inhibitors have yet to demonstrate encouraging clinical responses, it is now evident that this class of compounds is capable of only partial mTORC1 inhibition. Identifying previously unappreciated proteins needed for maintenance of mTORC1 activity may provide new targets and lead to the development of beneficial therapies for pancreatic cancer. PMID:22125066

Papageorgiou, Angela; Avruch, Joseph

2012-01-01

230

Tyrosine Kinase Inhibitors in Lung Cancer  

PubMed Central

SYNOPSIS ‘Driver mutations’ are essential for carcinogenesis as well as tumor progression as they confer a selective growth advantage to cancer cells. Identification of driver mutations in growth related protein kinases, especially tyrosine kinases have led to clinical development of an array of tyrosine kinase inhibitors in various malignancies, including lung cancer. Inhibition of epidermal growth factor receptor and anaplastic lymphoma kinase tyrosine kinases have proven to be of meaningful clinical benefit, while inhibition of several other tyrosine kinases have been of limited clinical benefit, thus far. An improved understanding of tyrosine kinase biology has also led to faster drug development, identification of resistance mechanisms and ways to overcome resistance. In this review, we discuss the clinical data supporting the use and practical aspects of management of patients on epidermal growth factor receptor and anaplastic lymphoma kinase tyrosine kinase inhibitors. PMID:22520981

Thomas, Anish; Rajan, Arun; Giaccone, Giuseppe

2012-01-01

231

Protein Kinases Curb Cell Death  

NSDL National Science Digital Library

Networks of aspartic acid–directed caspases play a major role in the execution of programmed cell death. Studies have provided evidence that caspases or their substrates are subjected to phosphorylation, which suggests a potential convergence of protein kinase and caspase signaling pathways. Various caspase substrates, but also several procaspases, are protected from cleavage when they are phosphorylated at sites adjacent to caspase cleavage sites. Whereas many distinct protein kinases could potentially protect substrates from caspase-mediated cleavage, a study has identified protein kinase CK2 as the most prominent kinase that exerts a global inhibition of caspase signaling pathways. CK2 is a component of protein kinase networks that are involved in tumors derived from various tissues. Its dysregulation in many cancers, together with its dual function in promoting cell growth and in suppressing apoptosis, is particularly relevant to its oncogenic potential. Thus, this study suggests that the ability of CK2 to contribute to tumorigenesis resides, at least in part, in its ability to phosphorylate caspases or their targets.

Odile Filhol (Grenoble;INSERM REV); Claude Cochet (Grenoble;INSERM REV)

2011-05-10

232

Frank Masci (1)MIPS D/L Review (S6), August 7, 2001 24m Latent-Image Flagging  

E-print Network

determines the number of electron traps released. iLi startTendTT )()( -= ),,T_EXP()( iiLipred TDNfLDN = Lipred xLDN >)( Lx #12;Frank Masci (5)MIPS D/L Review (S6), August 7, 2001 Require from Instrument Team l

Masci, Frank

233

Electronic, optical properties, surface energies and work functions of Ag8SnS6: First-principles method  

NASA Astrophysics Data System (ADS)

Ternary metal chalcogenide semiconductor Ag8SnS6, which is an efficient photocatalyst under visible light radiation, is studied by plane-wave pseudopotential density functional theory. After geometry optimization, the electronic and optical properties are studied. A scissor operator value of 0.81 eV is introduced to overcome the underestimation of the calculation band gaps. The contribution of different bands is analyzed by virtue of total and partial density of states. Furthermore, in order to understand the optical properties of Ag8SnS6, the dielectric function, absorption coefficient, and refractive index are also performed in the energy range from 0 to 11 eV. The absorption spectrum indicates that Ag8SnS6 has a good absorbency in visible light area. Surface energies and work functions of , , , and (112) orientations have been calculated. These results reveal the reason for an outstanding photocatalytic activity of Ag8SnS6. Project supported by the Science and Technology Development Foundation of China (Grant Nos. 2012A0302015 and 2012B0302050).

Lu, Chun-Lin; Zhang, Lin; Zhang, Yun-Wang; Liu, Shen-Ye; Mei, Yang

2015-01-01

234

*Current address: School of Resource & Environmental Management, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6.  

E-print Network

of Canada found that shellfish from coastal areas close to pulp and paper mills in British Columbia (BC, British Columbia, Canada V5A 1S6. **Corresponding author: Clare Wiseman, Center for Environmental Research and/or issued advisories for a number of shellfish fisheries in coastal areas of British Columbia

Gobas, Frank

235

Nucleocytoplasmic traffic of MAP kinases.  

PubMed

MAPK pathways represent a unique extracellular signal response system. An important feature of such a multicomponent system appears to be the spatial intracellular organization of individual components. Recent studies demonstrate that the MAP kinases of such pathways are the molecular link between the plasma membrane sensors and the nuclear transcription factors. Stimulation of several MAPK pathways induces rapid and transient nuclear accumulation of MAP kinases. Investigations on the mode of regulation of this process using higher eukaryotes Erk2 and lower eukaryotes Hog1 and Sty1/Spc1 have revealed that at least three events contribute to signal-induced nuclear localization of these MAP kinases: activation by phosphorylation, regulated nuclear import and export, and nuclear retention. PMID:10440225

Reiser, V; Ammerer, G; Ruis, H

1999-01-01

236

Phosphoinositol 3-kinase, a novel target molecule for the inhibitory effects of juglone on TPA-induced cell transformation.  

PubMed

Juglone (5-hydroxy-1,4-naphthalenedione) from black walnut trees induces apoptosis and inhibits proliferation of various malignant cells. Here, we investigated whether juglone affects 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced cell transformation through the phosphoinositol 3-kinase (PI3K) pathway. The results showed that TPA- and endothelial growth factor (EGF)-induced anchorage-independent colony formation were suppressed in a dose-dependent manner by treatment of JB6 CI41 mouse skin epidermal cells with juglone (2.5 and 5 µM). We demonstrated that juglone suppressed PI3K activity via direct binding to PI3K by sepharose 4B pull-down assay and western blot analysis. Juglone significantly suppressed TPA-induced protein kinase B (AKT) and c-Jun phosphorylation and c-fos activation, but not mitogen-activated protein-kinase kinase (MEK), extracellular signaling-regulated kinase (ERK) or 90 kDa ribosomal protein S6 kinase (RSK) phosphorylation. Juglone significantly blocked activator protein-1 (AP-1) and cyclooxygenase-2 (COX-2) activation more than the PI3K inhibitors LY294002 and wortmannin. Overall, these results showed the anticancer efficacy of juglone targeting PI3K to prevent TPA-induced tumorigenesis. PMID:22505246

Chae, Jung-Il; Cho, Jin Hyoung; Kim, Dong Joon; Lee, Kyung-Ae; Cho, Moon-Kyun; Nam, Hae-Seon; Woo, Kee-Min; Lee, Sang-Han; Shim, Jung-Hyun

2012-07-01

237

rpS6 Regulates Blood-Testis Barrier Dynamics By Affecting F-Actin Organization and Protein Recruitment  

PubMed Central

During spermatogenesis, preleptotene spermatocytes residing near the basement membrane of the seminiferous tubule must traverse the blood-testis barrier (BTB) at stage VIII–IX of the epithelial cycle to continue their development in the adluminal compartment. Unlike other blood-tissue barriers (e.g. the blood-brain barrier) that are created by the endothelial tight junction (TJ) barrier of capillaries, the BTB is created by specialized junctions between Sertoli cells in which TJ coexists with basal ectoplasmic specialization (basal ES, a testis-specific adherens junction). The basal ES is typified by the presence of tightly packed actin filament bundles sandwiched between cisternae of endoplasmic reticulum and the apposing plasma membranes of Sertoli cells. These actin filament bundles also confer unusual adhesive strength to the BTB. Yet the mechanisms by which these filamentous actin (F-actin) networks are regulated from the bundled to the debundled state to facilitate the transit of spermatocytes remain elusive. Herein, we provide evidence that ribosomal protein S6 (rpS6), the downstream signaling molecule of the mammalian target of rapamycin complex 1 (mTORC1) pathway, is a major regulator of F-actin organization and adhesion protein recruitment at the BTB. rpS6 is restrictively and spatiotemporally activated at the BTB during the epithelial cycle. An activation of rpS6 led to a disruption of the Sertoli cell TJ barrier and BTB integrity. Its silencing in vitro or in vivo by using small interfering RNA duplexes or short hairpin RNA was found to promote the Sertoli cell TJ permeability barrier by the recruitment of adhesion proteins (e.g. claudin-11 and occludin) to the BTB. Thus, rpS6 in the mTORC1 pathway regulates BTB restructuring via its effects on the F-actin organization and protein recruitment at the BTB. PMID:22948214

Mok, Ka-Wai; Mruk, Dolores D.; Silvestrini, Bruno

2012-01-01

238

SIRT1 Overexpression Antagonizes Cellular Senescence with Activated ERK/S6k1 Signaling in Human Diploid Fibroblasts  

PubMed Central

Sir2, a NAD-dependent deacetylase, modulates lifespan in yeasts, worms and flies. The SIRT1, mammalian homologue of Sir2, regulates signaling for favoring survival in stress. But whether SIRT1 has the function to influence cell viability and senescence under non-stressed conditions in human diploid fibroblasts is far from unknown. Our data showed that enforced SIRT1 expression promoted cell proliferation and antagonized cellular senescence with the characteristic features of delayed Senescence-Associated ?-galactosidase (SA-?-gal) staining, reduced Senescence-Associated Heterochromatic Foci (SAHF) formation and G1 phase arrest, increased cell growth rate and extended cellular lifespan in human fibroblasts, while dominant-negative SIRT1 allele (H363Y) did not significantly affect cell growth and senescence but displayed a bit decreased lifespan.. Western blot results showed that SIRT1 reduced the expression of p16INK4A and promoted phosphorylation of Rb. Our data also exposed that overexpression of SIRT1 was accompanied by enhanced activation of ERK and S6K1 signaling. These effects were mimicked in both WI38 cells and 2BS cells by concentration-dependent resveratrol, a SIRT1 activator. It was noted that treatment of SIRT1-.transfected cells with Rapamycin, a mTOR inhibitor, reduced the phosphorylation of S6K1 and the expression of Id1, implying that SIRT1-induced phosphorylation of S6K1 may be partly for the decreased expression of p16INK4A and promoted phosphorylation of Rb in 2BS. It was also observed that the expression of SIRT1 and phosphorylation of ERK and S6K1 was declined in senescent 2BS. These findings suggested that SIRT1-promoted cell proliferation and antagonized cellular senescence in human diploid fibroblasts may be, in part, via the activation of ERK/ S6K1 signaling. PMID:18320031

Huang, Jing; Gan, Qini; Han, Limin; Li, Jian; Zhang, Hai; Sun, Ying; Zhang, Zongyu; Tong, Tanjun

2008-01-01

239

Redox regulation of Janus kinase  

PubMed Central

The redox regulation of Janus kinases (JAKs) is a complex subject. Due to other redox-sensitive kinases in the kinome, redox-sensitive phosphatases, and cellular antioxidant systems and reactive oxygen species (ROS) production systems, the net biological outcomes of oxidative stress on JAK-dependent signal transduction vary according to the specific biological system examined. This review begins with a discussion of the biochemical evidence for a cysteine-based redox switch in the catalytic domain of JAKs, proceeds to consider direct and indirect regulatory mechanisms involved in biological experiments, and ends with a discussion of the role(s) of redox regulation of JAKs in various diseases. PMID:24416654

Duhé, Roy J

2013-01-01

240

SIGNAL TRANSDUCTION: Capturing Polo Kinase  

NSDL National Science Digital Library

Access to the article is free, however registration and sign-in are required. The interactions of kinases in signaling cascades and cell cycle pathways are so complex that it can be difficult to identify the protein binding domains that mediate these interactions. In a Perspective, Silljé and Nigg discuss a new proteomic screen (Elia et al.) that identifies the Polo-box binding domain of the mitotic kinase Plk1 as the domain that binds to phosphorylated sites in docking proteins such as Cdc25.

Herman H. W. Silljé (Max Planck Institute of Biochemistry;Department of Cell Biology); Erich A. Nigg (Max Planck Institute of Biochemistry;Department of Cell Biology)

2003-02-21

241

A Mathematical Exploration of MAP Kinase Behavior  

NASA Astrophysics Data System (ADS)

Mitogen-Activated Protein (MAP) kinase pathways are highly conserved from yeast to humans and are implicated in cell survival and cell death. Signaling through these pathways starts with the phosphorylation of the most upstream component (MAP kinase kinase kinase, MAPKKK), continues with phosphorylation of a MAP kinase kinase (MAPKK), and ends with phosphorylation of the target MAP kinase (MAPK). Theoretical studies over the past few decades have generated important insights into the dynamical behavior and signal processing capability of these pathways, including bistability, oscillations, signal amplification, etc. Prompted by the possibility of complex behavior in simpler signaling units than a full MAP kinase pathway, we investigate the possibility of In-Band Detection (IBD) within a single step of the cascade. We show that a basal rate of target phosphorylation can lead to IBD in a simpler system than the one described before, and define a precise relationship between the various reaction rates that is necessary to obtain IBD.

Adams, Rhys; Balazsi, Gabor

2008-03-01

242

Genetics Home Reference: Phosphoglycerate kinase deficiency  

MedlinePLUS

... have been reported in the scientific literature. What genes are related to phosphoglycerate kinase deficiency? Phosphoglycerate kinase deficiency is caused by mutations in the PGK1 gene. This gene provides instructions for making an enzyme ...

243

Regulation of ion channels by CAMP-dependent protein kinase and A-kinase anchoring proteins  

E-print Network

-dependent protein kinase is achieved, in part, through association with A-kinase anchoring proteins (AKAPs). Recent evidence suggests that specific AKAPs direct the kinase to submembrane sites to facilitate phosphorylation and modulation of a variety of ion channels. A new membrane-anchored AKAP targets CAMP-dependent protein kinase

Scott, John D.

244

Isolation of ATMEKK1 (a MAP Kinase Kinase Kinase)Interacting Proteins and Analysis of a MAP Kinase Cascade in Arabidopsis  

Microsoft Academic Search

In plants, a number of MAP kinase (MAPK), MAPK kinase (MAPKK), and MAPKK kinase (MAPKKK) homologues have been reported. However, there have been no reports of protein–protein interactions between these kinases or molecular analysis of MAPK cascades in higher plants. To analyze a possible MAPK cascade inArabidopsis thaliana,we took two molecular approaches. One is the two-hybrid screening of ATMEKK1 (a

Kazuya Ichimura; Tsuyoshi Mizoguchi; Kenji Irie; Peter Morris; Jérôme Giraudat; Kunihiro Matsumoto; Kazuo Shinozaki

1998-01-01

245

Degradation of Activated Protein Kinases by Ubiquitination  

PubMed Central

Protein kinases are important regulators of intracellular signal transduction pathways and play critical roles in diverse cellular functions. Once a protein kinase is activated, its activity is subsequently downregulated through a variety of mechanisms. Accumulating evidence indicates that the activation of protein kinases commonly initiates their downregulation via the ubiquitin/proteasome pathway. Failure to regulate protein kinase activity or expression levels can cause human diseases. PMID:19489726

Lu, Zhimin; Hunter, Tony

2009-01-01

246

The mitogenic and myogenic actions of insulin-like growth factors utilize distinct signaling pathways.  

PubMed

It is well established that mitogens inhibit differentiation of skeletal muscle cells, but the insulin-like growth factors (IGFs), acting through a single receptor, stimulate both proliferation and differentiation of myoblasts. Although the IGF-I mitogenic signaling pathway has been extensively studied in other cell types, little is known about the signaling pathway leading to differentiation in skeletal muscle. By using specific inhibitors of the IGF signal transduction pathway, we have begun to define the signaling intermediates mediating the two responses to IGFs. We found that PD098059, an inhibitor of mitogen-activated protein (MAP) kinase kinase activation, inhibited IGF-stimulated proliferation of L6A1 myoblasts and the events associated with it, such as phosphorylation of the MAP kinases and elevation of c-fos mRNA and cyclin D protein. Surprisingly, PD098059 caused a dramatic enhancement of differentiation, evident both at a morphological (fusion of myoblasts into myotubes) and biochemical level (elevation of myogenin and p21 cyclin-dependent kinase inhibitor expression, as well as creatine kinase activity). In sharp contrast, LY294002, an inhibitor of phosphatidylinositol 3-kinase, and rapamycin, an inhibitor of the activation of p70 S6 kinase (p70(S6k)), completely abolished IGF stimulation of L6A1 differentiation. We found that p70(S6k) activity increased substantially during differentiation, and this increase was further enhanced by PD098059. Our results demonstrate that the MAP kinase pathway plays a primary role in the mitogenic response and is inhibitory to the myogenic response in L6A1 myoblasts, while activation of the phosphatidylinositol 3-kinase/p70(S6k) pathway is essential for IGF-stimulated differentiation. Thus, it appears that signaling from the IGF-I receptor utilizes two distinct pathways leading either to proliferation or differentiation. PMID:9045696

Coolican, S A; Samuel, D S; Ewton, D Z; McWade, F J; Florini, J R

1997-03-01

247

Latest progress in tyrosine kinase inhibitors  

PubMed Central

Here we discuss the latest progress in development of some kinase inhibitors such as inhibitors of c-MET, LIM and Bcr-Abl kinases. Importantly, many oncogenic kinases signal via the mTOR pathway, suggesting a common target for drug combinations. PMID:24727648

Pospelova, Tatiana V.; Pospelov, Valery A.

2014-01-01

248

Targeting cancer with small molecule kinase inhibitors  

Microsoft Academic Search

Deregulation of kinase activity has emerged as a major mechanism by which cancer cells evade normal physiological constraints on growth and survival. To date, 11 kinase inhibitors have received US Food and Drug Administration approval as cancer treatments, and there are considerable efforts to develop selective small molecule inhibitors for a host of other kinases that are implicated in cancer

Jianming Zhang; Priscilla L. Yang; Nathanael S. Gray

2009-01-01

249

Protein Kinases (PowerPoint Slides)  

NSDL National Science Digital Library

The lecture begins with a discussion of the genomics and evolutionary relationships among kinases and then proceeds to describe the structure-function relationships of specific kinases, the molecular mechanisms underlying substrate specificity, and selected issues in regulation of kinase activity.

Avrom Caplan (Department of Pharmacology and Biological Chemistry, Mount Sinai School of Medicine; )

2005-02-22

250

A quantitative analysis of kinase inhibitor selectivity  

Microsoft Academic Search

Kinase inhibitors are a new class of therapeutics with a propensity to inhibit multiple targets. The biological consequences of multi-kinase activity are poorly defined, and an important step toward understanding the relationship between selectivity, efficacy and safety is the exploration of how inhibitors interact with the human kinome. We present interaction maps for 38 kinase inhibitors across a panel of

Mazen W Karaman; Sanna Herrgard; Daniel K Treiber; Paul Gallant; Corey E Atteridge; Brian T Campbell; Katrina W Chan; Pietro Ciceri; Mindy I Davis; Philip T Edeen; Raffaella Faraoni; Mark Floyd; Jeremy P Hunt; Daniel J Lockhart; Zdravko V Milanov; Michael J Morrison; Gabriel Pallares; Hitesh K Patel; Stephanie Pritchard; Lisa M Wodicka; Patrick P Zarrinkar

2008-01-01

251

Inhibitors of CLK Protein Kinases Suppress Cell Growth and Induce Apoptosis by Modulating Pre-mRNA Splicing  

PubMed Central

Accumulating evidence has demonstrated the importance of alternative splicing in various physiological processes, including the development of different diseases. CDC-like kinases (CLKs) and serine-arginine protein kinases (SRPKs) are components of the splicing machinery that are crucial for exon selection. The discovery of small molecule inhibitors against these kinases is of significant value, not only to delineate the molecular mechanisms of splicing, but also to identify potential therapeutic opportunities. Here we describe a series of small molecules that inhibit CLKs and SRPKs and thereby modulate pre-mRNA splicing. Treatment with these small molecules (Cpd-1, Cpd-2, or Cpd-3) significantly reduced the levels of endogenous phosphorylated SR proteins and caused enlargement of nuclear speckles in MDA-MB-468 cells. Additionally, the compounds resulted in splicing alterations of RPS6KB1 (S6K), and subsequent depletion of S6K protein. Interestingly, the activity of compounds selective for CLKs was well correlated with the activity for modulating S6K splicing as well as growth inhibition of cancer cells. A comprehensive mRNA sequencing approach revealed that the inhibitors induced splicing alterations and protein depletion for multiple genes, including those involved in growth and survival pathways such as S6K, EGFR, EIF3D, and PARP. Fluorescence pulse-chase labeling analyses demonstrated that isoforms with premature termination codons generated after treatment with the CLK inhibitors were degraded much faster than canonical mRNAs. Taken together, these results suggest that CLK inhibitors exhibit growth suppression and apoptosis induction through splicing alterations in genes involved in growth and survival. These small molecule inhibitors may be valuable tools for elucidating the molecular machinery of splicing and for the potential development of a novel class of antitumor agents. PMID:25581376

Araki, Shinsuke; Dairiki, Ryo; Nakayama, Yusuke; Murai, Aiko; Miyashita, Risa; Iwatani, Misa; Nomura, Toshiyuki; Nakanishi, Osamu

2015-01-01

252

The Origin and Evolution of G Protein-Coupled Receptor Kinases  

PubMed Central

G protein-coupled receptor (GPCR) kinases (GRKs) play key role in homologous desensitization of GPCRs. GRKs phosphorylate activated receptors, promoting high affinity binding of arrestins, which precludes G protein coupling. Direct binding to active GPCRs activates GRKs, so that they selectively phosphorylate only the activated form of the receptor regardless of the accessibility of the substrate peptides within it and their Ser/Thr-containing sequence. Mammalian GRKs were classified into three main lineages, but earlier GRK evolution has not been studied. Here we show that GRKs emerged at the early stages of eukaryotic evolution via an insertion of a kinase similar to ribosomal protein S6 kinase into a loop in RGS domain. GRKs in Metazoa fall into two clades, one including GRK2 and GRK3, and the other consisting of all remaining GRKs, split into GRK1-GRK7 lineage and GRK4-GRK5-GRK6 lineage in vertebrates. One representative of each of the two ancient clades is found as early as placozoan Trichoplax adhaerens. Several protists, two oomycetes and unicellular brown algae have one GRK-like protein, suggesting that the insertion of a kinase domain into the RGS domain preceded the origin of Metazoa. The two GRK families acquired distinct structural units in the N- and C-termini responsible for membrane recruitment and receptor association. Thus, GRKs apparently emerged before animals and rapidly expanded in true Metazoa, most likely due to the need for rapid signalling adjustments in fast-moving animals. PMID:22442725

Mushegian, Arcady; Gurevich, Vsevolod V.; Gurevich, Eugenia V.

2012-01-01

253

Isotope shifts for the 5 d 56 s7 s and 5 d 56 s6 d configurations of Re I  

NASA Astrophysics Data System (ADS)

The isotope shift and hyperfine structure in a rhenium hollow cathode discharge was studied for transitions of the type 5 d 56 s7 s ? 5 d 56 s6 p and 5 d 56 s6 d ? 5 d 56 s6 p through Doppler-free saturation absorption laserspectroscopy and high resolution interferometry. Taking configuration mixing in the lower levels of 5 d 56 s6 p under consideration, we obtain average configuration isotope shift values for 5 d 56 s7 s of -1760(100) MHz and for 5 d 56 s6 d of -1970(200) MHz. These experimental values compare extremely well with the theoretically predicted configuration isotope shifts in rhenium, based on pseudo-relativistic Hartree-Fock calculations, of -1710 MHz and -1940 MHz, resp. In addition hyperfine structure constants for rhenium levels of 5 d 56 s6 d are reported here for the first time.

Kronfieldt, H.-D.; Ashkenasi, D.; Basar, G.; Neale, L.; Wilson, M.

1993-09-01

254

EGFR-dependent and independent activation of Akt\\/mTOR cascade in bone and soft tissue tumors  

Microsoft Academic Search

To gain the insight into the involvement of signaling mediated by the mammalian target of rapamycin (mTOR) in the phenotype and biological profiles of tumors and tumor-like lesions of the bone and soft tissue, we analyzed the expression and phosphorylation (activation) of mTOR and its correlation with the status of upstream and downstream modulator proteins Akt, p70S6-kinase (S6K), and eukaryotic

Yoh Dobashi; Shioto Suzuki; Eiichi Sato; Yoshiki Hamada; Takashi Yanagawa; Akishi Ooi

2009-01-01

255

Targeting conformational plasticity of protein kinases.  

PubMed

The quest for ever more selective kinase inhibitors as potential future drugs has yielded a large repertoire of chemical probes that are selective for specific kinase conformations. These probes have been useful tools to obtain structural snapshots of kinase conformational plasticity. Similarly, kinetic and thermodynamic inhibitor binding experiments provide glimpses at the time scales and energetics of conformational interconversions. These experimental insights are complemented by computational predictions of conformational energy landscapes and simulations of conformational transitions and of the process of inhibitors binding to the protein kinase domain. A picture emerges in which highly selective inhibitors capitalize on the dynamic nature of kinases. PMID:25486330

Tong, Michael; Seeliger, Markus A

2015-01-16

256

Synthesis and characterization of Ag8(Ge1-x,Snx )(S6-y ,Sey) colloidal nanocrystals.  

PubMed

A facile colloidal approach to synthesize Ag8 (Ge1-x ,Snx )(S6-y ,Sey ) nanocrystals (NCs) in a highly controlled way across the entire compositional ranges (0?x?1, 0?y?6) has been developed. The NCs exhibit a uniform size distribution, highly crystalline structure, over 1?g scalable synthesis, and tunable band gaps in the range of 0.88-1.45?eV by varying their chemical compositions. The Ag8 GeS6 NCs with a band gap of approximately 1.45?eV were employed as a model light harvester to assess their applicability in solar cells by a full solution-processing device, yielding an efficiency of 0.28?% under AM1.5 illumination, demonstrating their application potential in solar energy utilization. PMID:25116162

Zhou, Bin; Xing, Yedi; Miao, Shu; Li, Mingrun; Zhang, Wen-Hua; Li, Can

2014-09-22

257

Three-dimensional characteristics of focal fault of 1995 M S =6.5 Wuding earthquake occurring in Yunnan Province  

Microsoft Academic Search

By means of the hypocenter distribution and focal mechanism of Wuding M\\u000a S=6.5 earthquake sequence occurred in 1995, the space orientation and activity characteristics of focal fault of Wuding earthquake\\u000a have been studied from the three-dimensional space-time process. The results indicate that the focal fault of Wuding earthquake\\u000a is a subsurface, NWW-trending, upright and right-lateral strike slip fault which is

Gui-Ling Diao; Si-Chang Zhang; Shao-Jin Wang; Xiao-Fan Long; Jun-Guo Wang

1999-01-01

258

Characterization of Methanosarcina barkeri MST and 227, Methanosarcina mazei S-6T, and Methanosarcina vacuolata Z-76IT  

Microsoft Academic Search

Members of the genus Methanosarcina are recognized as major aceticlastic methanogens, and several species which thrive in low-salt, pH-neutral culture medium at mesophilic temperatures have been described. However, the environmental conditions which support the fastest growth of these species (Methanosarcina barkeri MST (T = type strain) and 227, Methanosarcina mazei S-6T, and Methanosarcina vacuolata Z-761T) have not been reported previously.

GLORIA M. MAESTROJUAN; DAVID R. BOONE

259

Structure, organization, and expression of genes coding for envelope components in the archaeon Methanosarcina mazei S-6  

Microsoft Academic Search

The antigenic mosaics of archaeal species are complex and lead to the distinction of different immunotypes. We began the\\u000a dissection of the antigenic mosaic of the methanogen Methanosarcina mazei S-6 by gene cloning and sequencing. The analysis of the sequence, organization, and in vitro (heterologous) and in vivo expression\\u000a of two three-gene clusters that encode proteins localized to the cell

Linda E. Mayerhofer; Everly Conway de Macario; Rong Yao; Alberto J. L. Macario

1998-01-01

260

In Situ Reverse Transcription-PCR for Monitoring Gene Expression in Individual Methanosarcina mazei S-6 Cells  

Microsoft Academic Search

An in situ reverse transcription-PCR protocol for detecting specific mRNA in Methanosarcina mazei S-6 is described. This method allowed us to detect heat shock-induced increases in the intracellular levels of the transcript of the universal stress gene dnaK. The cell walls of paraformaldehyde-fixed cells were permeabilized by a thermal cycling procedure or by lysozyme treatment, and the cellular DNA was

MARIANNE LANGE; TIM TOLKER-NIELSEN; SØREN MOLIN; BIRGITTE K. AHRING

2000-01-01

261

Increased transcripts of the dnaK locus genes in Methanosarcina mazei S-6 exposed to supraoptimal concentrations of ammonia  

Microsoft Academic Search

The effect of supraoptimal concentrations of ammonia on cell growth and stress genes of the dnaK locus was investigated in Methanosarcina mazei S-6, a methanogen important for anaerobic digestion in bioreactors. When the concentration of NH4Cl was increased 25 times above the optimal for growth, the lag phase lengthened, growth occurred at a decreased rate, and a stress response was

Marianne Lange; Alberto J. L Macario; Birgitte K Ahring; Everly Conway de Macario

1997-01-01

262

Time Courses of Changes in Phospho- and Total- MAP Kinases in the Cochlea after Intense Noise Exposure  

PubMed Central

Mitogen-activated protein kinases (MAP kinases) are intracellular signaling kinases activated by phosphorylation in response to a variety of extracellular stimuli. Mammalian MAP kinase pathways are composed of three major pathways: MEK1 (mitogen-activated protein kinase kinase 1)/ERK 1/2 (extracellular signal-regulated kinases 1/2)/p90 RSK (p90 ribosomal S6 kinase), JNK (c-Jun amino (N)-terminal kinase)/c-Jun, and p38 MAPK pathways. These pathways coordinately mediate physiological processes such as cell survival, protein synthesis, cell proliferation, growth, migration, and apoptosis. The involvement of MAP kinase in noise-induced hearing loss (NIHL) has been implicated in the cochlea; however, it is unknown how expression levels of MAP kinase change after the onset of NIHL and whether they are regulated by transient phosphorylation or protein synthesis. CBA/J mice were exposed to 120-dB octave band noise for 2 h. Auditory brainstem response confirmed a component of temporary threshold shift within 0–24 h and significant permanent threshold shift at 14 days after noise exposure. Levels and localizations of phospho- and total- MEK1/ERK1/2/p90 RSK, JNK/c-Jun, and p38 MAPK were comprehensively analyzed by the Bio-Plex® Suspension Array System and immunohistochemistry at 0, 3, 6, 12, 24 and 48 h after noise exposure. The phospho-MEK1/ERK1/2/p90 RSK signaling pathway was activated in the spiral ligament and the sensory and supporting cells of the organ of Corti, with peaks at 3–6 h and independently of regulations of total-MEK1/ERK1/2/p90 RSK. The expression of phospho-JNK and p38 MAPK showed late upregulation in spiral neurons at 48 h, in addition to early upregulations with peaks at 3 h after noise trauma. Phospho-p38 MAPK activation was dependent on upregulation of total-p38 MAPK. At present, comprehensive data on MAP kinase expression provide significant insight into understanding the molecular mechanism of NIHL, and for developing therapeutic models for acute sensorineural hearing loss. PMID:23484051

Maeda, Yukihide; Fukushima, Kunihiro; Omichi, Ryotaro; Kariya, Shin; Nishizaki, Kazunori

2013-01-01

263

Theoretical study on the photophysical properties of hexapyrrolidine C60 adducts with Th, D3, and S6 symmetries.  

PubMed

The equilibrium geometries of three isomeric hexapyrrolidine C(60) adducts with T(h), D(3), and S(6) symmetries are optimized by means of the B3LYP method at the 6-31G basis sets in this paper. On the basis of the optimized structures, the excited state and third-order nonlinear optical properties, such as third-harmonic generation (THG), electric-field-induced second-harmonic generation (EFISHG), and degenerate four-wave mixing (DFWM), and two-photon absorption (TPA) cross sections, delta, are calculated by using the TDB3LYP model based on the 6-31G level coupled with the sum-over-states (SOS) method. The computational results show that the transition energies from S(0) to S(1) of the T(h) hexaadduct and the D(3) hexaadduct have a remarkable blue shift by comparison with that of the C(60) parent. These results are in agreement with experimental ones. However, the first singlet excitation energy of the S(6) hexaadduct has a red shift compared with that of the C(60) parent. Accordingly, we predict that different positions located by six addends may result in the different spectrum properties. Finally, the two-photon absorption cross sections indicate that the largest average value of resonant TPA, delta, of the D(3) hexaadduct has a red shift compared with those of the T(h) and S(6) hexaadducts. PMID:16851599

Li, X-D; Cheng, W-D; Wu, D-S; Lan, Y-Z; Zhang, H; Gong, Y-J; Li, F-F; Shen, J

2005-03-31

264

Discovery of a novel Raf kinase inhibitor.  

PubMed

We discuss the biology of Ras signal transduction and the epidemiology of ras mutations in association with disease as a background for the development of a Raf kinase inhibitor, BAY 43-9006. Knowledge of Ras effector pathways has permitted genetic validation of numerous targets involved in the Ras signaling cascade. A key Ras effector pathway involves the kinase cascade RAF/MEK/ERK (MEK: MAP/ERK kinase; ERK: extracellular signal related kinase). Indeed, we present studies of cell lines stably expressing mutant MEK constructs, which point to Raf kinase as a target for therapeutics with selective anti-tumor activity. Finally, a small molecule drug discovery program based on inhibition of Raf kinase activity is outlined and the initial pre-clinical development process of the Raf kinase inhibitor BAY 43-9006 is discussed. PMID:11566613

Lyons, J F; Wilhelm, S; Hibner, B; Bollag, G

2001-09-01

265

Oncoprotein protein kinase antibody kit  

DOEpatents

An isolated polypeptide (JNK) characterized by having a molecular weight of 46 kD as determined by reducing SDS-PAGE, having serine and threonine kinase activity, phosphorylating the c-Jun N-terminal activation domain and polynucleotide sequences and method of detection of JNK are provided herein. JNK phosphorylates c-Jun N-terminal activation domain which affects gene expression from AP-1 sites.

Karin, Michael (San Diego, CA); Hibi, Masahiko (San Diego, CA); Lin, Anning (La Jolla, CA)

2008-12-23

266

Acetate kinase activity in mycoplasmas.  

PubMed

Acetate kinase activity was assayed in 13 mycoplasmas. Nine species exhibited the enzymic activity in the direction of either synthesis of acetylphosphate or adenosine triphosphate. On the other hand Mycoplasma orale, Mycoplasma arthritidis, Ureaplasma urealyticum (10 serotypes), and two strains of Anaeroplasma species exhibited only minimal levels of the enzymic activity. In these four species, the enzyme does not seem to play a key role in adenosine triphosphate formation. PMID:6263869

Muhlrad, A; Peleg, I; Robertson, J A; Robinson, I M; Kahane, I

1981-07-01

267

Self-incompatibility (S) locus region of the mutated S6-haplotype of sour cherry (Prunus cerasus) contains a functional pollen S allele and a non-functional pistil S allele.  

PubMed

This study characterizes the S6m-haplotype, a mutated S6-haplotype with an altered HindIII cut site, of sour cherry (Prunus cerasus). Inheritance and pollination studies of S-haplotypes from reciprocal crosses between 'Erdi Botermo' (EB; S4S6mSa) and 'Rheinische Schattenmorelle' (RS; S6SaSbSc) revealed that the S6m-haplotype conferred unilateral incompatibility with a non-functional pistil component and a functional pollen component. Expression analyses of S6-RNase and SFB6, a candidate gene for pollen-S, in the S6m-haplotype showed that SFB6 was transcribed in EB pollen, but S6-RNase was not transcribed in EB styles. These results were consistent with data from the inheritance and pollination studies. Inverse PCR for the flanking regions of S6-RNase in the S6- and S6m-haplotypes revealed an approximately 2600 bp insertion present at approximately 800 bp upstream of the S6-RNase in the S6m-haplotype, which is responsible for the alternation of the HindIII cut site and a possible cause of inhibition of the transcription of S6-RNase. SFB6 was present downstream of S6-RNase in both the S6- and S6m-haplotypes and expressed in the same way, supporting the idea that SFB is a good candidate for pollen-S in Prunus. PMID:14512382

Yamane, Hisayo; Ikeda, Kazuo; Hauck, Nathanael R; Iezzoni, Amy F; Tao, Ryutaro

2003-11-01

268

Regulation of mTORC1 signaling by Src kinase activity is Akt1-independent in RSV-transformed cells.  

PubMed

Increased activity of the Src tyrosine protein kinase that has been observed in a large number of human malignancies appears to be a promising target for drug therapy. In the present study, a critical role of the Src activity in the deregulation of mTOR signaling pathway in Rous sarcoma virus (RSV)-transformed hamster fibroblasts, H19 cells, was shown using these cells treated with the Src-specific inhibitor, SU6656, and clones of fibroblasts expressing either the active Src or the dominant-negative Src kinase-dead mutant. Disruption of the Src kinase activity results in substantial reduction of the phosphorylation and activity of the Akt/protein kinase B (PKB), phosphorylation of tuberin (TSC2), mammalian target of rapamycin (mTOR), S6K1, ribosomal protein S6, and eukaryotic initiation factor 4E-binding protein 4E-BP1. The ectopic, active Akt1 that was expressed in Src-deficient cells significantly enhanced phosphorylation of TSC2 in these cells, but it failed to activate the inhibited components of the mTOR pathway that are downstream of TSC2. The data indicate that the Src kinase activity is essential for the activity of mTOR-dependent signaling pathway and suggest that mTOR targets may be controlled by Src independently of Akt1/TSC2 cascade in cells expressing hyperactive Src protein. These observations might have an implication in drug resistance to mTOR inhibitor-based cancer therapy in certain cell types. PMID:18283331

Vojtechová, Martina; Turecková, Jolana; Kucerová, Dana; Sloncová, Eva; Vachtenheim, Jirí; Tuhácková, Zdena

2008-02-01

269

Identification of Direct Tyrosine Kinase Substrates Based on Protein Kinase Assay-Linked Phosphoproteomics*  

PubMed Central

Protein kinases are implicated in multiple diseases such as cancer, diabetes, cardiovascular diseases, and central nervous system disorders. Identification of kinase substrates is critical to dissecting signaling pathways and to understanding disease pathologies. However, methods and techniques used to identify bona fide kinase substrates have remained elusive. Here we describe a proteomic strategy suitable for identifying kinase specificity and direct substrates in high throughput. This approach includes an in vitro kinase assay-based substrate screening and an endogenous kinase dependent phosphorylation profiling. In the in vitro kinase reaction route, a pool of formerly phosphorylated proteins is directly extracted from whole cell extracts, dephosphorylated by phosphatase treatment, after which the kinase of interest is added. Quantitative proteomics identifies the rephosphorylated proteins as direct substrates in vitro. In parallel, the in vivo quantitative phosphoproteomics is performed in which cells are treated with or without the kinase inhibitor. Together, proteins phosphorylated in vitro overlapping with the kinase-dependent phosphoproteome in vivo represents the physiological direct substrates in high confidence. The protein kinase assay-linked phosphoproteomics was applied to identify 25 candidate substrates of the protein-tyrosine kinase SYK, including a number of known substrates and many novel substrates in human B cells. These shed light on possible new roles for SYK in multiple important signaling pathways. The results demonstrate that this integrated proteomic approach can provide an efficient strategy to screen direct substrates for protein tyrosine kinases. PMID:23793017

Xue, Liang; Geahlen, Robert L.; Tao, W. Andy

2013-01-01

270

Compartment-specific, differential regulation of eukaryotic elongation factor 2 and its kinase within Aplysia sensory neurons.  

PubMed

Long-term facilitation (LTF) in Aplysia is a leading model for elucidating the biochemical mechanisms of synaptic plasticity underlying learning. LTF requires translational control downstream of target of rapamycin complex 1. Our lab has previously shown that treatment with the facilitating neurotransmitter, 5-hydroxytryptamine (5-HT), causes a target of rapamycin complex 1-mediated decrease in phosphorylation of eukaryotic elongation factor 2 (eEF2) within the neurites of sensory neurons involved in LTF. Here, we characterize the Aplysia orthologue of eEF2 kinase (eEF2K). We show that the Aplysia eEF2K orthologue contains an S6 kinase phosphorylation site and that a serine-to-alanine mutation at this site blocks the ability of 5-HT to decrease eEF2 phosphorylation in neurites. We also show that within the soma, 5-HT has the opposite effect, decreasing eEF2K phosphorylation at the S6 kinase site and, concomitantly, increasing eEF2 phosphorylation. Surprisingly, while eEF2K over-expression inhibits translation of a marker for internal ribosome entry site-dependent translation, it stimulates the translation of a marker for cap-dependent translation. This study demonstrates that eEF2 is differentially regulated in separate compartments and contributes to a growing body of evidence that inhibition of elongation can stimulate the translation of certain transcripts. PMID:21426346

Weatherill, Daniel B; McCamphill, Patrick K; Pethoukov, Eugenia; Dunn, Tyler W; Fan, Xiaotang; Sossin, Wayne S

2011-06-01

271

Intracellular signaling specificity in response to uniaxial vs. multiaxial stretch: implications for mechanotransduction.  

PubMed

Several lines of evidence suggest that muscle cells can distinguish between specific mechanical stimuli. To test this concept, we subjected C(2)C(12) myotubes to cyclic uniaxial or multiaxial stretch. Both types of stretch induced an increase in extracellular signal-regulated kinase (ERK) and protein kinase B (PKB/Akt) phosphorylation, but only multiaxial stretch induced ribosomal S6 kinase (p70(S6k)) phosphorylation. Further results demonstrated that the signaling events specific to multiaxial stretch (p70(S6k) phosphorylation) were elicited by forces delivered through the elastic culture membrane and were not due to greater surface area deformations or localized regions of large tensile strain. Experiments performed using medium that was conditioned by multiaxial stretched myotubes indicated that a release of paracrine factors was not sufficient for the induction of signaling to p70(S6k). Furthermore, incubation with gadolinium(III) chloride (500 microM), genistein (250 microM), PD-98059 (250 microM), bisindolylmaleimide I (20 microM), or LY-294002 (100 microM ) did not block the multiaxial stretch-induced signaling to p70(S6k). However, disrupting the actin cytoskeleton with cytochalasin D did block the multiaxial signaling to p70(S6k), with no effect on signaling to PKB/Akt. These results demonstrate that specific types of mechanical stretch activate distinct signaling pathways, and we propose that this occurs through direct mechanosensory-mechanotransduction mechanisms and not through previously defined growth factor/receptor binding pathways. PMID:15371259

Hornberger, Troy A; Armstrong, Dustin D; Koh, Timothy J; Burkholder, Thomas J; Esser, Karyn A

2005-01-01

272

Effects of peroxisome proliferator-activated receptor alpha (PPARalpha) agonists on leucine-induced phosphorylation of translational targets in C2C12 cells.  

PubMed

Effect of peroxisome proliferator-activated receptor alpha (PPARalpha) agonists, WY-14,643 (WY) and/or clofibrate, on the leucine-induced phosphorylation of translational targets in C2C12 myoblasts was studied. C2C12 cells were treated with WY or clofibrate for 24 h prior to stimulation with leucine. Western blot analyses revealed that the leucine-induced phosphorylation of p70 S6 kinase (p70S6K), a key regulator of translation initiation, was significantly higher in WY-treated cells than in control and clofibrate-treated cells. Phosphorylation of extracellular-regulated kinase (ERK1/2) was higher in WY-treated cells. WY treatment also increased the leucine-induced phosphorylation of ribosomal protein S6 and eukaryotic initiation factor 4B. In contrast, eukaryotic elongation factor 2, a marker for peptide chain elongation process, was significantly activated (dephosphorylated) only in leucine-stimulated control cells. Pre-treatment of the cells with PD98059 (ERK1/2 kinase inhibitor) prevented the phosphorylation of ERK1/2 and decreased the leucine-induced phosphorylation of p70S6K. It is concluded that WY increased the leucine-induced phosphorylation of target proteins involving in translation initiation via ERK/p70S6K pathway, but impaired the signaling for elongation process, suggesting that p70S6K phosphorylation may be essential, but not sufficient for the activation of entire targets for protein translation in WY-treated cells. PMID:18602970

Nakai, Naoya; Kawano, Fuminori; Terada, Masahiro; Oke, Yoshihiko; Ohira, Takashi; Ohira, Yoshinobu

2008-10-01

273

Receptor Tyrosine Kinases in Drosophila Development  

PubMed Central

Tyrosine phosphorylation plays a significant role in a wide range of cellular processes. The Drosophila genome encodes more than 20 receptor tyrosine kinases and extensive studies in the past 20 years have illustrated their diverse roles and complex signaling mechanisms. Although some receptor tyrosine kinases have highly specific functions, others strikingly are used in rather ubiquitous manners. Receptor tyrosine kinases regulate a broad expanse of processes, ranging from cell survival and proliferation to differentiation and patterning. Remarkably, different receptor tyrosine kinases share many of the same effectors and their hierarchical organization is retained in disparate biological contexts. In this comprehensive review, we summarize what is known regarding each receptor tyrosine kinase during Drosophila development. Astonishingly, very little is known for approximately half of all Drosophila receptor tyrosine kinases. PMID:23732470

Sopko, Richelle; Perrimon, Norbert

2014-01-01

274

Spectroscopic investigation on thallium 6 s6 p 2 configuration at electron-atom collisions: II. Excitation functions  

NASA Astrophysics Data System (ADS)

We have measured the excitation functions of the Tl I 221.1, 258.0, and 231.6 nm lines having clearly pronounced features above the ionization potential. The nature of these features, including the resonance mechanism and postcollisional interaction with the participation of autoionizing states of the 6 s6 p 2 configuration, has been discussed. A high-energy feature (at 12.7 eV) revealed in the excitation function of the 221.1 nm line is associated with the shape resonance formed at excitation of the autoionizing state of the configuration 6 p 3.

Bohachov, G. G.; Remeta, E. Yu.

2012-12-01

275

Roles for motifs of cell cycle regulating kinases beyond substrate selection of individual kinases  

E-print Network

Errors in the cell cycle, particularly during mitosis, have recently been implicated in tumorigenesis and cancer formation. Several protein kinases, including the major mitotic kinases Cdkl, Aurora A, Aurora B, Nek2, and ...

Alexander, Jes

2008-01-01

276

Regulation of Mitogen-Activated Protein Kinases by a Calcium\\/Calmodulin-Dependent Protein Kinase Cascade  

Microsoft Academic Search

Membrane depolarization of NG108 cells gives rapid (<5 min) activation of Ca2+\\/calmodulin-dependent protein kinase IV (CaM-KIV), as well as activation of c-Jun N-terminal kinase (JNK). To investigate whether the Ca2+-dependent activation of mitogen-activated protein kinases (ERK, JNK, and p38) might be mediated by the CaM kinase cascade, we have transfected PC12 cells, which lack CaM-KIV, with constitutively active mutants of

Herve Enslen; Hiroshi Tokumitsu; Philip J. S. Stork; Roger J. Davis; Thomas R. Soderling

1996-01-01

277

Tyrosine kinases in inflammatory dermatologic disease  

PubMed Central

Tyrosine kinases are enzymes that catalyze the phosphorylation of tyrosine residues on protein substrates. They are key components of signaling pathways that drive an array of cellular responses including proliferation, differentiation, migration, and survival. Specific tyrosine kinases have recently been identified as critical to the pathogenesis of several autoimmune and inflammatory diseases. Small-molecule inhibitors of tyrosine kinases are emerging as a novel class of therapy that may provide benefit in certain patient subsets. In this review, we highlight tyrosine kinase signaling implicated in inflammatory dermatologic diseases, evaluate strategies aimed at inhibiting these aberrant signaling pathways, and discuss prospects for future drug development. PMID:20584561

Paniagua, Ricardo T.; Fiorentino, David; Chung, Lorinda; Robinson, William H.

2010-01-01

278

Nuclear import of protein kinases and cyclins.  

PubMed

Karyophilic and acidic clusters were found in most nonmembrane serine/threonine protein kinases whose primary structure was examined. These karyophilic clusters might mediate the anchoring of the kinase molecules to transporter proteins for their regulated nuclear import and might constitute the nuclear localization signals (NLS) of the kinase molecules. In contrast to protein transcription factors that are exclusively nuclear possessing strong karyophilic peptides composed of at least four arginines (R) and lysines (K) within an hexapeptide flanked by proline and glycine helix-breakers, protein kinases often contain one histidine and three K+R residues; this is proposed to specify a weak NLS structure resulting in the nuclear import of a fraction of the total cytoplasmic kinase molecules as well as in their weak retention in the different ionic strength nuclear environment. Putative NLS peptides in protein kinases may also contain hydrophobic or bulky aromatic amino acids proposed to further diminish their capacity to act as strong NLS. Most kinases lacking karyophilic clusters (c-Mos, v-Mos, sea star MAP, and yeast KIN28, SRA1, SRA3, TPK1, TPK2) also lack acidic clusters, which is in contrast to most kinases containing both acidic and karyophilic peptides; this and the presence of R/K clusters in the transporter proteins supports a role of acidic clusters on kinases in nuclear import. Cyclins B lack karyophilic signals and are proposed to be imported into nuclei via their association with Cdc2. PMID:8825417

Boulikas, T

1996-01-01

279

Determinants for substrate phosphorylation by Dictyostelium myosin II heavy chain kinases A and B and eukaryotic elongation factor-2 kinase  

Microsoft Academic Search

The ? kinases are a widespread family of atypical protein kinases characterized by a novel type of catalytic domain. In this paper the peptide substrate recognition motifs for three ? kinases, Dictyostelium discoideum myosin heavy chain kinase (MHCK) A and MHCK B and mammalian eukaryotic elongation factor-2 kinase (eEF-2K), were characterized by incorporating amino acid substitutions into a previously identified

Scott W. Crawley; Graham P. Côté

2008-01-01

280

Phosphorylation of Canine Distemper Virus P Protein by Protein Kinase C-? and Casein Kinase II  

Microsoft Academic Search

Transcription by nonsegmented negative-strand RNA viruses is mediated by the viral RNA-dependent RNA polymerase and transcriptional cofactor P. The P protein is activated by phosphorylation, an event initiated by cellular kinases. The kinase used differs among this group of RNA viruses; vesicular stomatitis virus and respiratory syncytial virus utilize casein kinase II (CKII), whereas human parainfluenza virus type 3 utilizes

Zheng Liu; Clayton C. Huntley; Bishnu P. De; Tapas Das; Amiya K. Banerjee; Michael J. Oglesbee

1997-01-01

281

Crystal structure of the protein kinase domain of yeast AMP-activated protein kinase Snf1  

E-print Network

Crystal structure of the protein kinase domain of yeast AMP-activated protein kinase Snf1 Michael J of the protein kinase domain (KD) of the catalytic subunit of yeast AMPK (commonly known as SNF1). The Snf1-KD by phosphatases. AMPK is found in all eukaryotes. Yeast AMPK is more commonly known as SNF1 [1,6,7]. SNF1 has

Tong, Liang

282

Photoluminescence properties of new deep red-emitting Mn2+-activated CaLaGa3S6O phosphors  

NASA Astrophysics Data System (ADS)

A new deep red-emitting Mn2+-activated CaLaGa3S6O phosphor was prepared by using a solidstate reaction method. X-ray diffraction studies confirm a tetragonal structure with space group P21 m. The emission spectrum showed a broad band with an emission maximum at 676 nm under a host excitation of 332 nm. The optimum PL emission intensity was obtained at a concentration of 0.03 mole of Mn2+. The fluorescence lifetime of Mn2+ was calculated to be 0.368 ms for CaLaGa3S6O:0.03Mn2+. The Commission Internationale de I'Eclairage (CIE) chromaticity coordinates showed that the phosphors emissions were in the deep red region and were very near to the National Television Standards Committee (NTSC) standard values for red. Since the phosphor excitation lies in the near-UV excitable region, giving a deep red emission, it can be used for applications in near-UV phosphor converted white LED lighting and display devices.

Yu, Ruijin; Yang, Hyun Kyoung; Moon, Byung Kee; Choi, Byung Chun; Jeong, Jung Hyun

2012-10-01

283

Nucleotide sequences of genome segments S6, S7 and S10 of Dendrolimus punctatus cypovirus 1.  

PubMed

The nucleotide sequences of genome segments S6, S7 and S10 of Dendrolimus punctatus cypovirus 1 Hunan I (DpCPV-HN(I)) and DpCPV-HN(I)-Se(3) (DpCPV-HN(I) passed three times in Spodoptera exigua) were determined. Segment S10 was 944 nucleotides in length and encoded a polyhedrin of 248 amino acids (28,439 Da). Only two nucleotide mutations were found between DpCPV-HN(I) S10 and DpCPV-HN(I)-Se3 S10, and the deduced amino acid sequences of the polyhedrin proteins were identical. Segment S7, 1 501 nucleotides, encoded a protein of 448 amino acids ( approximately 50 kDa; p50). Thirty-one nucleotide mutations were found between DpCPV-HN(I) S7 and DpCPV-HN(I)-Se3 S7, but these resulted in only four amino acid changes. DpCPV-HN(I) S6 encoded a protein of 561 amino acids (63,688 Da; p64). The amino acid sequence of p64, had a high leucine content (10%), and contained a leucine zipper motif and one ATP/GTP-binding site motif. PMID:14689283

Hong, J J; Duan, J L; Zhao, S L; Xu, H G; Peng, H Y

2004-01-01

284

Essential role for the putative S6 inner pore region in the activation gating of the human TRPA1 channel.  

PubMed

The ankyrin transient receptor potential channel TRPA1 is a sensory neuron-specific channel that is gated by various proalgesic agents such as allyl isothiocyanate (AITC), deep cooling or highly depolarizing voltages. How these disparate stimuli converge on the channel protein to open/close its ion-conducting pore is unknown. We identify several residues within the S6 inner pore-forming region of human TRPA1 that contribute to AITC and voltage-dependent gating. Alanine substitution in the conserved mid-S6 proline (P949A) strongly affected the activation/deactivation and ion permeation. The P949A was functionally restored by substitution with a glycine but not by the introduction of a proline at positions -1, -2 or +1, which indicates that P949 is structurally required for the normal functioning of the TRPA1 channel. Mutation N954A generated a constitutively open phenotype, suggesting a role in stabilizing the closed conformation. Alanine substitutions in the distal GXXXG motif decreased the relative permeability of the channel for Ca(2+) and strongly affected its activation/deactivation properties, indicating that the distal G962 stabilizes the open conformation. G958, on the other hand, provides additional tuning leading to decreased channel activity. Together these findings provide functional support for the critical role of the putative inner pore region in controlling the conformational changes that determine the transitions between the open and close states of the TRPA1 channel. PMID:19422860

Benedikt, Jan; Samad, Abdul; Ettrich, Rudiger; Teisinger, Jan; Vlachova, Viktorie

2009-07-01

285

The Phosphoinositide 3-Kinase Pathway  

NSDL National Science Digital Library

Phosphorylated lipids are produced at cellular membranes during signaling events and contribute to the recruitment and activation of various signaling components. The role of phosphoinositide 3-kinase (PI3K), which catalyzes the production of phosphatidylinositol-3,4,5-trisphosphate, in cell survival pathways; the regulation of gene expression and cell metabolism; and cytoskeletal rearrangements are highlighted. The PI3K pathway is implicated in human diseases including diabetes and cancer, and understanding the intricacies of this pathway may provide new avenues for therapuetic intervention.

Lewis Cantley (Beth Israel Deaconess Medical Center;Department of Cell Biology, Harvard Medical School and Division of Signal Transduction)

2002-05-31

286

Phosphatidylinositol 3-Kinase (PI3K) and Phosphatidylinositol 3-Kinase-Related Kinase (PIKK) Inhibitors: Importance of the Morpholine Ring.  

PubMed

Phosphatidylinositol 3-kinases (PI3Ks) and phosphatidylinositol 3-kinase-related protein kinases (PIKKs) are two related families of kinases that play key roles in regulation of cell proliferation, metabolism, migration, survival, and responses to diverse stresses including DNA damage. To design novel efficient strategies for treatment of cancer and other diseases, these kinases have been extensively studied. Despite their different nature, these two kinase families have related origin and share very similar kinase domains. Therefore, chemical inhibitors of these kinases usually carry analogous structural motifs. The most common feature of these inhibitors is a critical hydrogen bond to morpholine oxygen, initially present in the early nonspecific PI3K and PIKK inhibitor 3 (LY294002), which served as a valuable chemical tool for development of many additional PI3K and PIKK inhibitors. While several PI3K pathway inhibitors have recently shown promising clinical responses, inhibitors of the DNA damage-related PIKKs remain thus far largely in preclinical development. PMID:25387153

Andrs, Martin; Korabecny, Jan; Jun, Daniel; Hodny, Zdenek; Bartek, Jiri; Kuca, Kamil

2015-01-01

287

Yeast Pak1 Kinase Associates with and Activates Snf1  

Microsoft Academic Search

Members of the Snf1\\/AMP-activated protein kinase family are activated under conditions of nutrient stress by a distinct upstream kinase. Here we present evidence that the yeast Pak1 kinase functions as a Snf1- activating kinase. Pak1 associates with the Snf1 kinase in vivo, and the association is greatly enhanced under glucose-limiting conditions when Snf1 is active. Snf1 kinase complexes isolated from

Nandita Nath; Rhonda R. McCartney; Martin C. Schmidt

2003-01-01

288

Activation of the mitogen-activated protein kinase pathway by bone sialoprotein regulates osteoblast differentiation.  

PubMed

Bone sialoprotein (BSP) is an abundant protein in the extracellular matrix of bone that has been suggested to have several different physiological functions, including the nucleation of hydroxyapatite (HA), promotion of cell attachment and binding of collagen. Studies in our lab have demonstrated that increased expression of BSP in osteoblast cells can increase expression of the osteoblast-related genes Runx2 and Osx as well as alkaline phosphatase and osteocalcin and increase matrix mineralization. To determine the molecular mechanisms responsible for the BSP-mediated increase in osteoblastic differentiation, several functional domain mutants of BSP were expressed in primary rat bone osteoblastic cells, including the contiguous glutamic acid sequences (polyGlu) and the arginine-glycine-aspartic acid (RGD) motif. Markers of osteoblast differentiation, including matrix mineralization and alkaline phosphatase staining, were increased in cells expressing BSP mutants of the polyGlu sequences but not in cells expressing RGD-mutated BSP. We also determined the dependence on integrin-associated pathways in promoting BSP-mediated differentiation responses in osteoblasts by demonstrating the activation of focal adhesion kinase, MAP kinase-associated proteins ERK1/2, ribosomal s6 kinase 2 and the AP-1 protein cFos. Thus, the mechanism regulating osteoblast differentiation by BSP was determined to be dependent on integrin-mediated intracellular signaling pathways. PMID:18728350

Gordon, Jonathan A R; Hunter, Graeme K; Goldberg, Harvey A

2009-01-01

289

mTORC1 Phosphorylates the ULK1-mAtg13-FIP200 Autophagy Regulatory Complex  

NSDL National Science Digital Library

High nutrient availability stimulates the mammalian target of rapamycin complex 1 (mTORC1) to coordinately activate anabolic processes, such as protein synthesis, while inhibiting the cellular catabolism of autophagy. Positive regulation of protein synthesis through the mTORC1 substrates p70 ribosomal S6 kinase (p70S6K) and eukaryotic initiation factor 4E binding protein 1 (4E-BP1) has been well characterized. The complementary inhibitory mechanism in which mTORC1 phosphorylates the autophagy regulatory complex containing unc-51-like kinase 1 (ULK1), the mammalian Atg13 protein, and focal adhesion kinase interacting protein of 200 kD (FIP200) has also been elucidated.

Edmond Y. Chan (University of Strathclyde;Strathclyde Institute of Pharmacy and Biomedical Sciences REV)

2009-08-18

290

Modulating noncatalytic function with kinase inhibitors.  

PubMed

In this issue of Chemistry & Biology, Hari and colleagues show that conformation-selective ATP-competitive kinase inhibitors have distinct noncatalytic effects on Erk2, including the ability to modulate protein-protein interactions outside the ATP-binding site. These findings enhance our knowledge about the diverse array of activities in which kinase inhibitors can target signaling pathways. PMID:24856138

Agius, Michael P; Soellner, Matthew B

2014-05-22

291

Receptor tyrosine kinases and respiratory motor plasticity  

Microsoft Academic Search

Protein kinases are a family of enzymes that transfer a phosphate group from adenosine tri-phosphate to an amino acid residue on a protein. The receptor tyrosine kinases (RTKs) are expressed on the outer cell membrane, bind extracellular protein ligands, and phosphorylate tyrosine residues on other proteins—essentially permitting communication between cells. Such activity regulates multiple aspects of cellular physiology including cell

Francis J. Golder

2008-01-01

292

Ruthenium Complexes as Protein Kinase Inhibitors  

E-print Network

Ruthenium Complexes as Protein Kinase Inhibitors Lilu Zhang, Patrick Carroll, and Eric Meggers* Uni. A strategy is introduced for the creation of ruthenium complex-based protein kinase inhibitors 1 (X ) CO organic molecules. Our efforts are focused on ruthenium complex scaffolds because ruthenium offers

Meggers, Eric

293

The Human Nm23\\/Nucleoside Diphosphate Kinases  

Microsoft Academic Search

Biochemical experiments over the past 40 years have shown that nucleoside diphosphate(NDP) kinase activity, which catalyzes phosphoryl transfer from a nucleoside triphosphate toa nucleoside diphosphate, is ubiquitously found in organisms from bacteria to human. Overthe past 10 years, eight human genes of the nm23\\/NDP kinase family have been discoveredthat can be separated into two groups based on analysis of their

Marie-Lise Laurence Lacombe; Annie Munier; James G. Mehus; David O. Lambeth

2000-01-01

294

Interlayer Magnetoresistance due to Chiral Soliton Lattice Formation in Hexagonal Chiral Magnet CrNb3S6  

NASA Astrophysics Data System (ADS)

We investigate the interlayer magnetoresistance (MR) along the chiral crystallographic axis in the hexagonal chiral magnet CrNb3S6. In a region below the incommensurate-commensurate phase transition between the chiral soliton lattice and the forced ferromagnetic state, a negative MR is obtained in a wide range of temperature, while a small positive MR is found very close to the Curie temperature. Normalized data of the negative MR almost falls into a single curve and is well fitted by a theoretical equation of the soliton density, meaning that the origin of the MR is ascribed to the magnetic scattering of conduction electrons by a nonlinear, periodic, and countable array of magnetic soliton kinks.

Togawa, Y.; Kousaka, Y.; Nishihara, S.; Inoue, K.; Akimitsu, J.; Ovchinnikov, A. S.; Kishine, J.

2013-11-01

295

Degradation of Si-Al aluminide coating after service of turbine blades made of ZhS6K superalloy  

NASA Astrophysics Data System (ADS)

Aero engine turbine blades made of nickel-based superalloys are characterized by very good mechanical properties, but their hot corrosion resistance is insufficient. Therefore, various protective coatings must be applied. These coatings are typically made of diffusive aluminide coatings based on the ?-NiAl intermetallic phase. Although the oxidation resistance and hot corrosion resistance of these coatings are very good, their thermal resistance is relatively poor. As a result, turbine blades with aluminide coatings are prone to degradation in case of overheating. In this paper we study the degradation of the Si-Al aluminide coating on turbine blades made of ZhS6K superalloy during overheating in the DV2 jet engine.

Chmiela, B.; Kianicová, M.; Soza?ska, M.; Swad?ba, L.

2012-05-01

296

Pore helix-S6 interactions are critical in governing current amplitudes of KCNQ3 K+ channels.  

PubMed

Two mechanisms have been postulated to underlie KCNQ3 homomeric current amplitudes, which are small compared with those of KCNQ4 homomers and KCNQ2/Q3 heteromers. The first involves differential channel expression governed by the D-helix within the C-terminus. The second suggests similar channel surface expression but an intrinsically unstable KCNQ3 pore. Here, we find H2O2-enhanced oligomerization of KCNQ4 subunits, as reported by nondenaturing polyacrylamide gel electrophoresis, at C643 at the end of the D-helix, where KCNQ3 possesses a histidine. However, H2O2-mediated enhancement of KCNQ4 currents was identical in the C643A mutant, and KCNQ3 H646C produced homomeric or heteromeric (with KCNQ2) currents similar to those of wild-type KCNQ3, ruling out this divergent residue as underlying the small KCNQ3 amplitudes. In KcsA, F103 in S6 is critical for pore-mediated destabilization of the conductive pathway. We found that mutations at the analogous F344 in KCNQ3 dramatically decreased the KCNQ3 currents. Total internal reflection fluorescence imaging revealed only minor differential surface expression among the wild-type and mutant channels. Homology modeling suggests that the effects of the F344 mutants arise from the disruption of the interaction between F344 and A315 in the pore helix. These data support a secondary role of the C-terminus, compared with pore helix-S6 interactions, in governing KCNQ3 current amplitudes. PMID:22713565

Choveau, Frank S; Bierbower, Sonya M; Shapiro, Mark S

2012-06-01

297

Optical inter-satellite communication with dynamically reconfigurable optical device using Sn2P2S6 crystal  

NASA Astrophysics Data System (ADS)

Since the optical inter-satellite communication has attractive advantages such as high-speed transmission with high confidence, almost no electronic magnetic interference, and low power consumption, it has been activity investigated. However, directivity control of the laser beams requires a bulky and complicated system in satellite mobile communications. A more flexible and high accurate system with small and simple mechanism has been desired. In this study, we propose a new method of optical inter-satellite communication with a dynamically reconfigurable optical directional device in which diffraction gratings are automatically rewritten and reorganized in response of incident conditions by moving satellites. For realizing such a device, we have developed Sn2P2S6 crystals which have a high sensitive photorefractivity and dynamic reconfigurable property. Furthermore, this crystal has hundreds times faster response than conventional photorefractive materials such as BaTiO3. These features are extremely advantageous to construct a high-speed and flexible communication system with a large tolerance to displacement of moving satellites. To investigate the possibility of the dynamically reconfigurable optical inter-satellite communication system, we experimentally evaluate the temporal and spatial characteristics of Sn2P2S6 crystals for the variation of the beam incident angle. Moreover, the diffraction beam from the crystal has phase conjugate wavefronts of the beam entering from the counter direction. We try to utilize this behavior to suppress the beam spread and to reduce the background light such as sunlight with a spatial filtering technique that has sensitivity in wavefront differences of the signal and background light.

Nishimaki, Kaori; Okamoto, Atsushi; Fujita, Tomohiro; Grabar, Alexander A.; Takabayashi, Masanori; Uozumi, Jun; Tomita, Akihisa; Takayama, Yoshihisa

2011-03-01

298

Discovery of Type II Inhibitors of TGF?-Activated Kinase 1 (TAK1) and Mitogen-Activated Protein Kinase Kinase Kinase Kinase 2 (MAP4K2).  

PubMed

We developed a pharmacophore model for type II inhibitors that was used to guide the construction of a library of kinase inhibitors. Kinome-wide selectivity profiling of the library resulted in the identification of a series of 4-substituted 1H-pyrrolo[2,3-b]pyridines that exhibited potent inhibitory activity against two mitogen-activated protein kinases (MAPKs), TAK1 (MAP3K7) and MAP4K2, as well as pharmacologically well interrogated kinases such as p38? (MAPK14) and ABL. Further investigation of the structure-activity relationship (SAR) resulted in the identification of potent dual TAK1 and MAP4K2 inhibitors such as 1 (NG25) and 2 as well as MAP4K2 selective inhibitors such as 16 and 17. Some of these inhibitors possess good pharmacokinetic properties that will enable their use in pharmacological studies in vivo. A 2.4 Å cocrystal structure of TAK1 in complex with 1 confirms that the activation loop of TAK1 assumes the DFG-out conformation characteristic of type II inhibitors. PMID:25075558

Tan, Li; Nomanbhoy, Tyzoon; Gurbani, Deepak; Patricelli, Matthew; Hunter, John; Geng, Jiefei; Herhaus, Lina; Zhang, Jianming; Pauls, Eduardo; Ham, Youngjin; Choi, Hwan Geun; Xie, Ting; Deng, Xianming; Buhrlage, Sara J; Sim, Taebo; Cohen, Philip; Sapkota, Gopal; Westover, Kenneth D; Gray, Nathanael S

2014-07-30

299

Temperature-orientation dependence of charateristics of short-term strength, Young's modulus, and linear expansion coefficient of single crystals of ZhS6F alloy  

Microsoft Academic Search

Conclusions 1.The short-term mechanical properties, i.e., tensile and yield strength elongation of the single crystals of the creep-resisting ZhS6F alloy are highly anisotropic up to 900°C. The maximum tensile and yield strength values were recorded for the single crystals with orientation, the minimum values for the single crystals with orientation. At 950°C, the properties become isotropic.2.The single crystals of ZhS6F

I. L. Svetlov; N. N. Sukhanov; A. I. Krivko; I. M. Roshchina; I. M. Khatsinskaya; A. I. Samoilov

1987-01-01

300

Turnover of the Active Fraction of IRS1 Involves Raptor-mTOR- and S6K1Dependent Serine Phosphorylation in Cell Culture Models of Tuberous Sclerosis  

Microsoft Academic Search

The TSC1-TSC2\\/Rheb\\/Raptor-mTOR\\/S6K1 cell growth cassette has recently been shown to regulate cell autonomous insulin and insulin-like growth factor I (IGF-I) sensitivity by transducing a negative feedback signal that targets insulin receptor substrates 1 and 2 (IRS1 and -2). Using two cell culture models of the familial hamartoma syndrome, tuberous sclerosis, we show here that Raptor-mTOR and S6K1 are required for

O. Jameel Shah; Tony Hunter

2006-01-01

301

Physiological roles of mitogen-activated-protein-kinase-activated p38-regulated/activated protein kinase  

PubMed Central

Mitogen-activated protein kinases (MAPKs) are a family of proteins that constitute signaling pathways involved in processes that control gene expression, cell division, cell survival, apoptosis, metabolism, differentiation and motility. The MAPK pathways can be divided into conventional and atypical MAPK pathways. The first group converts a signal into a cellular response through a relay of three consecutive phosphorylation events exerted by MAPK kinase kinases, MAPK kinase, and MAPK. Atypical MAPK pathways are not organized into this three-tiered cascade. MAPK that belongs to both conventional and atypical MAPK pathways can phosphorylate both non-protein kinase substrates and other protein kinases. The latter are referred to as MAPK-activated protein kinases. This review focuses on one such MAPK-activated protein kinase, MAPK-activated protein kinase 5 (MK5) or p38-regulated/activated protein kinase (PRAK). This protein is highly conserved throughout the animal kingdom and seems to be the target of both conventional and atypical MAPK pathways. Recent findings on the regulation of the activity and subcellular localization, bona fide interaction partners and physiological roles of MK5/PRAK are discussed. PMID:21666810

Kostenko, Sergiy; Dumitriu, Gianina; Lægreid, Kari Jenssen; Moens, Ugo

2011-01-01

302

A Human MAP Kinase Interactome  

PubMed Central

Mitogen Activated Protein Kinase (MAPK) pathways form the backbone of signal transduction within the mammalian cell. Here, we apply a systematic experimental and computational approach to map 2,269 interactions between human MAPK-related proteins and other cellular machinery and to assemble these data into functional modules. A core network of 641 interactions is supported by multiple lines of evidence including conservation with yeast. Using siRNA knockdowns, we reveal that a significant number of novel interactors can modulate MAPK mediated signaling. We uncover the Na-H exchanger NHE1 as a scaffold for a novel set of MAPKs, link HSP90 chaperones to MAPK pathways, and identify MUC12 as the human analogue to the yeast signaling mucin Msb2. This study makes available a large resource of MAPK interactions along with the accompanying clone libraries. It illustrates a methodology for probing signaling networks based on functional refinement of experimentally-derived protein interaction maps. PMID:20936779

Bandyopadhyay, Sourav; Chiang, Chih-yuan; Srivastava, Jyoti; Gersten, Merril; White, Suhaila; Bell, Russell; Kurschner, Cornelia; Martin, Christopher H.; Smoot, Mike; Sahasrabudhe, Sudhir; Barber, Diane L.; Chanda, Sumit K.; Ideker, Trey

2010-01-01

303

Self-incompatibility (S) locus region of the mutated S6-haplotype of sour cherry (Prunus cerasus) contains a functional pollen S allele and a non-functional pistil S allele  

Microsoft Academic Search

This study characterizes the S6m-haplotype, a mutated S6-haplotype with an altered HindIII cut site, of sour cherry (Prunus cerasus). Inheritance and pollination studies of S-haplotypes from reciprocal crosses between 'Erdi Botermo' (EB; S4S6mSa) and 'Rheinische Schattenmorelle' (RS; S6SaSbSc) revealed that the S6m-haplotype conferred unilateral incompati- bility with a non-functional pistil component and a functional pollen component. Expression analyses of S6-RNase

Hisayo Yamane; Kazuo Ikeda; Nathanael R. Hauck; Amy F. Iezzoni; Ryutaro Tao

2003-01-01

304

Dynamic architecture of a protein kinase.  

PubMed

Protein kinases are dynamically regulated signaling proteins that act as switches in the cell by phosphorylating target proteins. To establish a framework for analyzing linkages between structure, function, dynamics, and allostery in protein kinases, we carried out multiple microsecond-scale molecular-dynamics simulations of protein kinase A (PKA), an exemplar active kinase. We identified residue-residue correlated motions based on the concept of mutual information and used the Girvan-Newman method to partition PKA into structurally contiguous "communities." Most of these communities included 40-60 residues and were associated with a particular protein kinase function or a regulatory mechanism, and well-known motifs based on sequence and secondary structure were often split into different communities. The observed community maps were sensitive to the presence of different ligands and provide a new framework for interpreting long-distance allosteric coupling. Communication between different communities was also in agreement with the previously defined architecture of the protein kinase core based on the "hydrophobic spine" network. This finding gives us confidence in suggesting that community analyses can be used for other protein kinases and will provide an efficient tool for structural biologists. The communities also allow us to think about allosteric consequences of mutations that are linked to disease. PMID:25319261

McClendon, Christopher L; Kornev, Alexandr P; Gilson, Michael K; Taylor, Susan S

2014-10-28

305

Protein kinase A is central for forward transport of two-pore domain potassium channels K2P3.1 and K2P9.1.  

PubMed

Acid-sensitive two-pore domain potassium channels (K2P3.1 and K2P9.1) play key roles in both physiological and pathophysiological mechanisms, the most fundamental of which is control of resting membrane potential of cells in which they are expressed. These background "leak" channels are constitutively active once expressed at the plasma membrane, and hence tight control of their targeting and surface expression is fundamental to the regulation of K(+) flux and cell excitability. The chaperone protein, 14-3-3, binds to a critical phosphorylated serine in the channel C termini of K2P3.1 and K2P9.1 (Ser(393) and Ser(373), respectively) and overcomes retention in the endoplasmic reticulum by ?COP. We sought to identify the kinase responsible for phosphorylation of the terminal serine in human and rat variants of K2P3.1 and K2P9.1. Adopting a bioinformatic approach, three candidate protein kinases were identified: cAMP-dependent protein kinase, ribosomal S6 kinase, and protein kinase C. In vitro phosphorylation assays were utilized to determine the ability of the candidate kinases to phosphorylate the channel C termini. Electrophysiological measurements of human K2P3.1 transiently expressed in HEK293 cells and cell surface assays of GFP-tagged K2P3.1 and K2P9.1 enabled the determination of the functional implications of phosphorylation by specific kinases. All of our findings support the conclusion that cAMP-dependent protein kinase is responsible for the phosphorylation of the terminal serine in both K2P3.1 and K2P9.1. PMID:21357689

Mant, Alexandra; Elliott, David; Eyers, Patrick A; O'Kelly, Ita M

2011-04-22

306

Exploring phosphatidylinositol 5-phosphate 4-kinase function  

E-print Network

correlation between low PI5P4K? expression in human breast tumors and reduced patient survival. The mechanism is not yet fully revealed and is clearly complex, involving among other things the regulation of E-cadherin. In the other study, Jude et al (Jude et... of Type II phosphatidylinositol phosphate kinase (phosphatidylinositol 5-phosphate 4-kinase) by its ?-helix 7. Biochem J. 2000;364:587-91. Clarke JH, Emson PC, Irvine RF. Localization of phosphatidylinositol phosphate kinase IIgamma in kidney to a membrane...

Bulley, Simon J.; Clarke, Jonathan H.; Droubi, Alaa; Giudici, Maria-Luisa; Robin F., Irvine

2014-10-02

307

Viral Serine/Threonine Protein Kinases ?  

PubMed Central

Phosphorylation represents one the most abundant and important posttranslational modifications of proteins, including viral proteins. Virus-encoded serine/threonine protein kinases appear to be a feature that is unique to large DNA viruses. Although the importance of these kinases for virus replication in cell culture is variable, they invariably play important roles in virus virulence. The current review provides an overview of the different viral serine/threonine protein kinases of several large DNA viruses and discusses their function, importance, and potential as antiviral drug targets. PMID:21084474

Jacob, Thary; Van den Broeke, Céline; Favoreel, Herman W.

2011-01-01

308

Distinct signalling pathways mediate insulin and phorbol ester-stimulated eukaryotic initiation factor 4F assembly and protein synthesis in HEK 293 cells.  

PubMed

Stimulation of serum-starved human embryonic kidney (HEK) 293 cells with either the phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA), or insulin resulted in increases in the phosphorylation of 4E-BP1 and p70 S6 kinase, eIF4F assembly, and protein synthesis. All these effects were blocked by rapamycin, a specific inhibitor of mTOR. Phosphatidylinositol 3-kinase and protein kinase B were activated by insulin but not by TPA. Therefore TPA can induce eIF4F assembly, protein synthesis, and the phosphorylation of p70 S6 kinase and 4E-BP1 independently of both phosphatidylinositol 3-kinase and protein kinase B. Using two structurally unrelated inhibitors of MEK (PD098059 and U0126), we provide evidence that Erk activation is important in TPA stimulation of eIF4F assembly and the phosphorylation of p70 S6 kinase and 4E-BP1 and that basal MEK activity is important for basal, insulin, and TPA-stimulated protein synthesis. Transient transfection of constitutively active mitogen-activated protein kinase interacting kinase 1 (the eIF4E kinase) indicated that inhibition of protein synthesis and eIF4F assembly by PD098059 is not through inhibition of eIF4E phosphorylation but of other signals emanating from MEK. This report also provides evidence that increased eIF4E phosphorylation alone does not affect the assembly of the eIF4F complex or general protein synthesis. PMID:10753934

Herbert, T P; Kilhams, G R; Batty, I H; Proud, C G

2000-04-14

309

Tyrosine Kinase Inhibition: An Approach to Drug Development  

Microsoft Academic Search

Protein tyrosine kinases (PTKs) regulate cell proliferation, cell differentiation, and signaling processes in the cells of the immune system. Uncontrolled signaling from receptor tyrosine kinases and intracellular tyrosine kinases can lead to inflammatory responses and to diseases such as cancer, atherosclerosis, and psoriasis. Thus, inhibitors that block the activity of tyrosine kinases and the signaling pathways they activate may provide

Alexander Levitzki; Aviv Gazit

1995-01-01

310

Rac-1 and Raf-1 kinases, components of distinct signaling pathways, activate myotonic dystrophy protein kinase  

NASA Technical Reports Server (NTRS)

Myotonic dystrophy protein kinase (DMPK) is a serine-threonine protein kinase encoded by the myotonic dystrophy (DM) locus on human chromosome 19q13.3. It is a close relative of other kinases that interact with members of the Rho family of small GTPases. We show here that the actin cytoskeleton-linked GTPase Rac-1 binds to DMPK, and coexpression of Rac-1 and DMPK activates its transphosphorylation activity in a GTP-sensitive manner. DMPK can also bind Raf-1 kinase, the Ras-activated molecule of the MAP kinase pathway. Purified Raf-1 kinase phosphorylates and activates DMPK. The interaction of DMPK with these distinct signals suggests that it may play a role as a nexus for cross-talk between their respective pathways and may partially explain the remarkable pleiotropy of DM.

Shimizu, M.; Wang, W.; Walch, E. T.; Dunne, P. W.; Epstein, H. F.

2000-01-01

311

Phosphoinositide-dependent protein kinase-1 (PDK1)-independent activation of the protein kinase C substrate, protein kinase D.  

PubMed

Phosphoinoisitide dependent kinase l (PDK1) is proposed to phosphorylate a key threonine residue within the catalytic domain of the protein kinase C (PKC) superfamily that controls the stability and catalytic competence of these kinases. Hence, in PDK1-null embryonic stem cells intracellular levels of PKCalpha, PKCbeta1, PKCgamma, and PKCepsilon are strikingly reduced. Although PDK1-null cells have reduced endogenous PKC levels they are not completely devoid of PKCs and the integrity of downstream PKC effector pathways in the absence of PDK1 has not been determined. In the present report, the PDK1 requirement for controlling the phosphorylation and activity of a well characterised substrate for PKCs, the serine kinase protein kinase D, has been examined. The data show that in embryonic stem cells and thymocytes loss of PDK1 does not prevent PKC-mediated phosphorylation and activation of protein kinase D. These results reveal that loss of PDK1 does not functionally inactivate all PKC-mediated signal transduction. PMID:17617409

Wood, C David; Kelly, April P; Matthews, Sharon A; Cantrell, Doreen A

2007-07-24

312

Atypical mitogen-activated protein kinases: structure, regulation and functions.  

PubMed

Mitogen-activated protein (MAP) kinases are a family of serine/threonine kinases that play a central role in transducing extracellular cues into a variety of intracellular responses ranging from lineage specification to cell division and adaptation. Fourteen MAP kinase genes have been identified in the human genome, which define 7 distinct MAP kinase signaling pathways. MAP kinases can be classified into conventional or atypical enzymes, based on their ability to get phosphorylated and activated by members of the MAP kinase kinase (MAPKK)/MEK family. Conventional MAP kinases comprise ERK1/ERK2, p38s, JNKs, and ERK5, which are all substrates of MAPKKs. Atypical MAP kinases include ERK3/ERK4, NLK and ERK7. Much less is known about the regulation, substrate specificity and physiological functions of atypical MAP kinases. PMID:17161475

Coulombe, Phillipe; Meloche, Sylvain

2007-08-01

313

A systematic interaction map of validated kinase inhibitors with Ser/Thr kinases  

PubMed Central

Protein kinases play a pivotal role in cell signaling, and dysregulation of many kinases has been linked to disease development. A large number of kinase inhibitors are therefore currently under investigation in clinical trials, and so far seven inhibitors have been approved as anti-cancer drugs. In addition, kinase inhibitors are widely used as specific probes to study cell signaling, but systematic studies describing selectivity of these reagents across a panel of diverse kinases are largely lacking. Here we evaluated the specificity of 156 validated kinase inhibitors, including inhibitors used in clinical trials, against 60 human Ser/Thr kinases using a thermal stability shift assay. Our analysis revealed many unexpected cross-reactivities for inhibitors thought to be specific for certain targets. We also found that certain combinations of active-site residues in the ATP-binding site correlated with the detected ligand promiscuity and that some kinases are highly sensitive to inhibition using diverse chemotypes, suggesting them as preferred intervention points. Our results uncovered also inhibitor cross-reactivities that may lead to alternate clinical applications. For example, LY333?531, a PKC? inhibitor currently in phase III clinical trials, efficiently inhibited PIM1 kinase in our screen, a suggested target for treatment of leukemia. We determined the binding mode of this inhibitor by x-ray crystallography and in addition showed that LY333?531 induced cell death and significantly suppressed growth of leukemic cells from acute myeloid leukemia patients. PMID:18077363

Fedorov, Oleg; Marsden, Brian; Pogacic, Vanda; Rellos, Peter; Müller, Susanne; Bullock, Alex N.; Schwaller, Juerg; Sundström, Michael; Knapp, Stefan

2007-01-01

314

Redundant kinase activation and resistance of EGFR-tyrosine kinase inhibitors  

PubMed Central

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) have shown dramatic effects against that tumors harboring EGFR activating mutations in the EGFR intracytoplasmic tyrosine kinase domain and resulted in cell apoptosis. Unfortunately, a number of patients ultimately developed resistance by multiple mechanisms. Thus, elucidation of the mechanism of resistance to EGFR-TKIs can provide strategies for blocking or reversing the situation. Recent studies suggested that redundant kinase activation plays pivotal roles in escaping from the effects of EGFR-TKIs. Herein, we aimed to characterize several molecular events involved in the resistance to EGFR-TKIs mediated by redundant kinase activation. PMID:25520855

Luo, Min; Fu, Li-Wu

2014-01-01

315

Meriolins, a New Class of Cell Death-Inducing Kinase Inhibitors with Enhanced Selectivity for Cyclin-Dependent Kinases  

Microsoft Academic Search

Protein kinases represent promising anticancer drug targets. We describe here the meriolins, a new family of inhibitors of cyclin-dependent kinases (CDK). Meriolins represent a chem- ical structural hybrid between meridianins and variolins, two families of kinase inhibitors extracted from various marine invertebrates. Variolin B is currently in preclinical evaluation as an antitumor agent. A selectivity study done on 32 kinases

Karima Bettayeb; Oscar M. Tirado; Severine Marionneau-Lambot; Olivier Lozach; Jonathan C. Morris; Silvia Mateo-Lozano; Peter Drueckes; Christoph Schachtele; Francois Liger; Bernard Marquet; Benoit Joseph; Aude Echalier; Jane A. Endicott; Vicente Notario; Laurent Meijer

2007-01-01

316

Systems Biology of AGC Kinases in Fungi  

NSDL National Science Digital Library

This STKE Review discusses the evidence that Sch9 is the yeast Saccharomyces cerevesiae homolog of mammalian protein kinase B. Protein kinase B and Sch9 are members of the AGC family of protein kinases, which are involved in diverse cellular functions, including nutrient-sensitive signaling that affects cell survival, cell size, cell cycle progression, and cellular response to stress. With 3 figures, 1 table, and 55 citations, this review provides a discussion of the methods for investigating AGC kinase function, with special emphasis on the challenges presented by the essential nature of these enzymes and their functional redundancy. There is also a discussion of how yeast cells can be used to study aging and longevity, with a description of the evidence for a role for Sch9 in aging and nutrient-sensitive processes.

Alex Sobko (Ontario; Iogen Corporation, Ottawa REV)

2006-09-12

317

Magnetically stabilized Fe8(?4-S)6S8 clusters in Ba6Fe25S27.  

PubMed

We have prepared Ba6Fe25S27, and studied its magnetic properties and electronic structure. Single crystal diffraction revealed a cubic phase (Pm3[combining macron]m) with a = 10.2057(9) Å and Z = 1. Within the large cubic cell, tetrahedrally coordinated Fe atoms arrange into octonuclear Fe8(?4-S)6(S8) clusters, which can be described as a cube of Fe atoms with six face-capping and eight terminal S atoms. SQUID magnetometry measurements reveal an antiferromagnetic transition at 25 K and anomalous high-temperature dependence of magnetic susceptibility that is non-Curie like-two magnetic signatures which mimic behavior seen in the parent phases of Fe-based superconductors. Using a combined DFT and molecular orbital based approach, we provide an interpretation of the bonding and stability within Ba6M25S27 (M = Fe, Co, Ni) and related M9S8 phases. Through a ?-bonding molecular orbital model of the transition metal coordination environments, we illustrate how the local stability can be enhanced through addition of Ba. In addition, we perform spin-polarized DFT calculations on Ba6Fe25S27 to determine the effect of adopting an antiferromagnetic spin state on its electronic structure. By studying the magnetic properties from an empirical and computational perspective, we hope to elucidate what aspects of the magnetic structure are significant to bonding. PMID:25140897

Stacey, Timothy E; Borg, Christopher K H; Zavalij, Peter J; Rodriguez, Efrain E

2014-10-21

318

Ribosomal Protein S6 Interacts with the Latency-Associated Nuclear Antigen of Kaposi's Sarcoma-Associated Herpesvirus ?  

PubMed Central

The latency-associated nuclear antigen (LANA) is central to the maintenance of Kaposi's sarcoma-associated herpesvirus (KSHV) and to the survival of KSHV-carrying tumor cells. In an effort to identify interaction partners of LANA, we purified authentic high-molecular-weight complexes of LANA by conventional chromatography followed by immunoprecipitation from the BC-3 cell line. This is the first analysis of LANA-interacting partners that is not based on forced ectopic expression of LANA. Subsequent tandem mass spectrometry (MS/MS) analysis identified many of the known LANA-interacting proteins. We confirmed LANA's interactions with histones. Three classes of proteins survived our stringent four-step purification procedure (size, heparin, anion, and immunoaffinity chromatography): two heat shock proteins (Hsp70 and Hsp96 precursor), signal recognition particle 72 (SRP72), and 10 different ribosomal proteins. These proteins are likely involved in structural interactions within LANA high-molecular-weight complexes. Here, we show that ribosomal protein S6 (RPS6) interacts with LANA. This interaction is mediated by the N-terminal domain of LANA and does not require DNA or RNA. Depletion of RPS6 from primary effusion lymphoma (PEL) cells dramatically decreases the half-life of full-length LANA. The fact that RPS6 has a well-established nuclear function beyond its role in ribosome assembly suggests that RPS6 (and by extension other ribosomal proteins) contributes to the extraordinary stability of LANA. PMID:21734034

Chen, Wuguo; Dittmer, Dirk P.

2011-01-01

319

Crystal structure of bovine procarboxypeptidase A-S6 subunit III, a highly structured truncated zymogen E.  

PubMed Central

Subunit III, a defective serine endopeptidase lacking the typical N-terminal hydrophobic dipeptide is secreted by the pancreas of ruminant species as part of the bovine ternary complex procarboxypeptidase A-S6. Two monoclinic crystal forms were obtained and subsequently used to solve its X-ray structure. The highest resolution model of subunit III was refined at 1.7 A resolution to a crystallographic R-factor of 18.4%, with r.m.s. bond deviations from ideality of 0.012 A. About 80% of the model presents the characteristic architecture of trypsin-like proteases. The remaining zones, however, have well-defined, unique conformations. The regions from residues 70 to 80 and from 140 to 155 present maximum distances of 16 and 18 A relative to serine proteases and zymogens. Comparisons with the structures of porcine elastase 1 and chymotrypsinogen A indicate that the specific binding pocket of subunit III adopts a zymogen-like conformation and thus provide a basis for its inactivity. In general, the structural analysis of subunit III strongly suggests that it corresponds to a truncated version of a new class of highly structured elastase-like zymogen molecules. Based on the structures of subunit III and elastase 1, it is concluded that large concerted movements are necessary for the activation of zymogen E. Images PMID:8168476

Pignol, D; Gaboriaud, C; Michon, T; Kerfelec, B; Chapus, C; Fontecilla-Camps, J C

1994-01-01

320

Glycogen Synthase Kinase 3? Is Tyrosine Phosphorylated by PYK2  

Microsoft Academic Search

Glycogen synthase kinase 3? (GSK3?) is a Ser\\/Thr kinase that is involved in numerous cellular activities. GSK3? is activated by tyrosine phosphorylation. However, very little is known about the tyrosine kinases that are responsible for phosphorylating GSK3?. In this report, we investigated the ability of the calcium-dependent tyrosine kinase, proline-rich tyrosine kinase 2 (PYK2) to tyrosine phosphorylate GSK3?. In transfected

Judith A. Hartigan; Wen-Cheng Xiong; Gail V. W. Johnson

2001-01-01

321

A Structural Basis for Substrate Specificities of Protein Ser\\/Thr Kinases: Primary Sequence Preference of Casein Kinases I and II, NIMA, Phosphorylase Kinase, Calmodulin Dependent Kinase II, CDK5, and Erk1  

Microsoft Academic Search

We have developed a method to study the primary sequence specificities of protein kinases by using an orienteddegeneratepeptidelibrary.WereportherethesubstratespecificitiesofeightproteinSer\\/Thrkinases. All of the kinases studied selected distinct optimal substrates. The identified substrate specificities of these kinases, together with known crystal structures of protein kinase A, CDK2, Erk2, twitchin, and casein kinase I, provide a structural basis for the substrate recognition of protein

Z. SONGYANG; KUN PING LU; YOUNG T. KWON; LI-HUEI TSAI; ODILE FILHOL; CLAUDE COCHET; DEBRA A. BRICKEY; THOMAS R. SODERLING; CHERYL BARTLESON; DONALD J. GRAVES; ANTHONY J. DEMAGGIO; MERL F. HOEKSTRA; JOHN BLENIS; TONY HUNTER; ANDLEWIS C. CANTLEY

1996-01-01

322

The diglyceride kinase of rat cerebral cortex  

PubMed Central

1. Formation of phosphatidic acid by diglyceride kinase (EC 2.7.1.-) in the presence of ATP and Mg2+ was shown in a homogenate and subcellular fractions of rat cerebral cortex. 2. The kinase was activated by Mg2+. Ca2+ activated to a smaller extent but was inhibitory in the presence of optimum concentration of Mg2+. Activity was greatly increased in the presence of added 1,2-diglyceride. 3. Sodium deoxycholate markedly stimulated the reaction, but other detergents (Cutscum and Triton X-100) did not. 4. Diglyceride kinase was concentrated in the supernatant and microsomal fractions from rat cerebral cortex. The distribution of the kinase in the particulate fractions resembled that of acetylcholinesterase and 5?-nucleotidase. 5. The rate of phosphatidic acid synthesis by the diglyceride kinase route was much greater than reported rates for acylation of 3-glycerophosphate and was also very rapid in comparison with the rates of other steps in the synthesis of phosphoinositides. 6. Acetylcholine had no stimulatory effect on diglyceride kinase of isolated intact nerve-ending particles or of nerve-ending membranes obtained after osmotic shock. PMID:5117567

Lapetina, E. G.; Hawthorne, J. N.

1971-01-01

323

Arsenic Toxicity to Saccharomyces cerevisiae Is a Consequence of Inhibition of the TORC1 Kinase Combined with a Chronic Stress Response  

PubMed Central

The conserved Target Of Rapamycin (TOR) growth control signaling pathway is a major regulator of genes required for protein synthesis. The ubiquitous toxic metalloid arsenic, as well as mercury and nickel, are shown here to efficiently inhibit the rapamycin-sensitive TORC1 (TOR complex 1) protein kinase. This rapid inhibition of the TORC1 kinase is demonstrated in vivo by the dephosphorylation and inactivation of its downstream effector, the yeast S6 kinase homolog Sch9. Arsenic, mercury, and nickel cause reduction of transcription of ribosome biogenesis genes, which are under the control of Sfp1, a TORC1-regulated transcriptional activator. We report that arsenic stress deactivates Sfp1 as it becomes dephosphorylated, dissociates from chromatin, and exits the nucleus. Curiously, whereas loss of SFP1 function leads to increased arsenic resistance, absence of TOR1 or SCH9 has the opposite effect suggesting that TORC1 has a role beyond down-regulation of Sfp1. Indeed, we show that arsenic activates the transcription factors Msn2 and Msn4 both of which are targets of TORC1 and protein kinase A (PKA). In contrast to TORC1, PKA activity is not repressed during acute arsenic stress. A normal level of PKA activity might serve to dampen the stress response since hyperactive Msn2 will decrease arsenic tolerance. Thus arsenic toxicity in yeast might be determined by the balance between chronic activation of general stress factors in combination with lowered TORC1 kinase activity. PMID:19073887

Hosiner, Dagmar; Lempiäinen, Harri; Reiter, Wolfgang; Urban, Joerg; Loewith, Robbie; Ammerer, Gustav; Schweyen, Rudolf

2009-01-01

324

Diacylglycerol Kinase Delta Promotes Lipogenesis†  

PubMed Central

We have studied the relationship between diacylglycerol kinase delta (DGK?) and lipogenesis. There is a marked increase in the expression of DGK? during the differentiation of 3T3-L1 cells to adipocytes, as well as in the synthesis of neutral and polar lipids. When 3T3-L1 undifferentiated fibroblasts are transfected to express DGK? there is increased triglyceride synthesis without differentiation to adipocytes. Hence, expression of DGK? promotes lipogenesis. Lipid synthesis is decreased in DGK? knockout mouse embryo fibroblasts, especially for lipids with shorter acyl chains and limited unsaturation. This reduction occurs for both neutral and polar lipids. These findings suggest reduced de novo lipid synthesis. This is confirmed by measuring the incorporation of glycerol into polar and neutral lipids that is higher in the wild type cells than in the DGK? knockouts. In comparison, there was no change in lipid synthesis in DGK? knockout mouse embryo fibroblasts. We also demonstrate that the DGK? knockout cells had a lower expression of acetyl-CoA carboxylase and fatty acid synthase as well as a lower degree of activation by phosphorylation of ATP citrate lyase. These three enzymes are involved in the synthesis of long chain fatty acids. Our results demonstrate that DGK? markedly increases lipid synthesis, at least in part as a result of promoting the de novo synthesis of fatty acids. PMID:24090246

Shulga, Yulia V.; Loukov, Dessi; Ivanova, Pavlina T.; Milne, Stephen B.; Myers, David S.; Hatch, Grant M.; Umeh, G.; Jalan, Divyanshi; Fullerton, Morgan D.; Steinberg, Gregory R.; Topham, Matthew K.; Brown, H. Alex; Epand, Richard M.

2013-01-01

325

The Roles of Two IB Kinase-related Kinases in Lipopolysaccharide and Double Stranded RNA Signaling and Viral Infection  

Microsoft Academic Search

Viral infection and stimulation with lipopolysaccharide (LPS) or double stranded RNA (dsRNA) induce phosphorylation of interferon (IFN) regulatory factor (IRF)-3 and its translo- cation to the nucleus, thereby leading to the IFN- ? gene induction. Recently, two IB kinase (IKK)-related kinases, inducible IB kinase (IKK- i ) and TANK-binding kinase 1 (TBK1), were suggested to act as IRF-3 kinases and

Hiroaki Hemmi; Osamu Takeuchi; Shintaro Sato; Masahiro Yamamoto; Tsuneyasu Kaisho; Hideki Sanjo; Taro Kawai; Katsuaki Hoshino; Kiyoshi Takeda; Shizuo Akira

326

Class III phosphoinositide 3-kinase--Beclin1 complex mediates the amino acid-dependent regulation of autophagy in C2C12 myotubes.  

PubMed

Increased proteolysis contributes to muscle atrophy that prevails in many diseases. Elucidating the signalling pathways responsible for this activation is of obvious clinical importance. Autophagy is a ubiquitous degradation process, induced by amino acid starvation, that delivers cytoplasmic components to lysosomes. Starvation markedly stimulates autophagy in myotubes, and the present studies investigate the mechanisms of this regulation. In C(2)C(12) myotubes incubated with serum growth factors, amino acid starvation stimulated autophagic proteolysis independently of p38 and p42/p44 mitogen-activated protein kinases, but in a PI3K (phosphoinositide 3-kinase)-dependent manner. Starvation, however, did not alter activities of class I and class II PI3Ks, and was not sufficient to affect major signalling proteins downstream from class I PI3K (glycogen synthase kinase, Akt/protein kinase B and protein S6). In contrast, starvation increased class III PI3K activity in whole-myotube extracts. In fact, this increase was most pronounced for a population of class III PI3K that coimmunoprecipitated with Beclin1/Apg6 protein, a major determinant in the initiation of autophagy. Stimulation of proteolysis was reproduced by feeding myotubes with synthetic dipalmitoyl-PtdIns3 P, the class III PI3K product. Conversely, protein transfection of anti-class III PI3K inhibitory antibody into starved myotubes inverted the induction of proteolysis. Therefore, independently of class I PI3K/Akt, protein S6 and mitogen-activated protein kinase pathways, amino acid starvation stimulates proteolysis in myotubes by regulating class III PI3K-Beclin1 autophagic complexes. PMID:12967324

Tassa, Amina; Roux, Marie Paule; Attaix, Didier; Bechet, Daniel M

2003-12-15

327

Class III phosphoinositide 3-kinase--Beclin1 complex mediates the amino acid-dependent regulation of autophagy in C2C12 myotubes.  

PubMed Central

Increased proteolysis contributes to muscle atrophy that prevails in many diseases. Elucidating the signalling pathways responsible for this activation is of obvious clinical importance. Autophagy is a ubiquitous degradation process, induced by amino acid starvation, that delivers cytoplasmic components to lysosomes. Starvation markedly stimulates autophagy in myotubes, and the present studies investigate the mechanisms of this regulation. In C(2)C(12) myotubes incubated with serum growth factors, amino acid starvation stimulated autophagic proteolysis independently of p38 and p42/p44 mitogen-activated protein kinases, but in a PI3K (phosphoinositide 3-kinase)-dependent manner. Starvation, however, did not alter activities of class I and class II PI3Ks, and was not sufficient to affect major signalling proteins downstream from class I PI3K (glycogen synthase kinase, Akt/protein kinase B and protein S6). In contrast, starvation increased class III PI3K activity in whole-myotube extracts. In fact, this increase was most pronounced for a population of class III PI3K that coimmunoprecipitated with Beclin1/Apg6 protein, a major determinant in the initiation of autophagy. Stimulation of proteolysis was reproduced by feeding myotubes with synthetic dipalmitoyl-PtdIns3 P, the class III PI3K product. Conversely, protein transfection of anti-class III PI3K inhibitory antibody into starved myotubes inverted the induction of proteolysis. Therefore, independently of class I PI3K/Akt, protein S6 and mitogen-activated protein kinase pathways, amino acid starvation stimulates proteolysis in myotubes by regulating class III PI3K-Beclin1 autophagic complexes. PMID:12967324

Tassa, Amina; Roux, Marie Paule; Attaix, Didier; Bechet, Daniel M

2003-01-01

328

Kinase-independent mechanisms of resistance of leukemia stem cells to tyrosine kinase inhibitors.  

PubMed

Tyrosine kinase inhibitors such as imatinib mesylate have changed the clinical course of chronic myeloid leukemia; however, the observation that these inhibitors do not target the leukemia stem cell implies that patients need to maintain lifelong therapy. The mechanism of this phenomenon is unclear: the question of whether tyrosine kinase inhibitors are inactive inside leukemia stem cells or whether leukemia stem cells do not require breakpoint cluster region (Bcr)-Abl signaling is currently under debate. Herein, I propose an alternative model: perhaps the leukemia stem cell requires Bcr-Abl, but is dependent on its kinase-independent functions. Kinases such as epidermal growth factor receptor and Janus kinase 2 possess kinase-independent roles in regulation of gene expression; it is worth investigating whether Bcr-Abl has similar functions. Mechanistically, Bcr-Abl is able to activate the Ras, phosphatidylinositol 3-kinase/Akt, and/or the Src-kinase Hck/Stat5 pathways in a scaffolding-dependent manner. Whereas the scaffolding activity of Bcr-Abl with Grb2 is dependent on autophosphorylation, kinases such as Hck can use Bcr-Abl as substrate, inducing phosphorylation of Y177 to enable scaffolding ability in the absence of Bcr-Abl catalytic activity. It is worth investigating whether leukemia stem cells exclusively express kinases that are able to use Bcr-Abl as substrate. A kinase-independent role for Bcr-Abl in leukemia stem cells would imply that drugs that target Bcr-Abl's scaffolding ability or its DNA-binding ability should be used in conjunction with current therapeutic regimens to increase their efficacy and eradicate the stem cells of chronic myeloid leukemia. PMID:24598782

Ichim, Christine Victoria

2014-04-01

329

Survey of tyrosine kinase signaling reveals ROS kinase fusions in human cholangiocarcinoma.  

PubMed

Cholangiocarcinoma, also known as bile duct cancer, is the second most common primary hepatic carcinoma with a median survival of less than 2 years. The molecular mechanisms underlying the development of this disease are not clear. To survey activated tyrosine kinases signaling in cholangiocarcinoma, we employed immunoaffinity profiling coupled to mass spectrometry and identified DDR1, EPHA2, EGFR, and ROS tyrosine kinases, along with over 1,000 tyrosine phosphorylation sites from about 750 different proteins in primary cholangiocarcinoma patients. Furthermore, we confirmed the presence of ROS kinase fusions in 8.7% (2 out of 23) of cholangiocarcinoma patients. Expression of the ROS fusions in 3T3 cells confers transforming ability both in vitro and in vivo, and is responsive to its kinase inhibitor. Our data demonstrate that ROS kinase is a promising candidate for a therapeutic target and for a diagnostic molecular marker in cholangiocarcinoma. The identification of ROS tyrosine kinase fusions in cholangiocarcinoma, along with the presence of other ROS kinase fusions in lung cancer and glioblastoma, suggests that a more broadly based screen for activated ROS kinase in cancer is warranted. PMID:21253578

Gu, Ting-Lei; Deng, Xiaxing; Huang, Feizhou; Tucker, Meghan; Crosby, Katherine; Rimkunas, Victoria; Wang, Yi; Deng, Gang; Zhu, Lei; Tan, Zhiping; Hu, Yerong; Wu, Chunlin; Nardone, Julie; MacNeill, Joan; Ren, Jianmin; Reeves, Cynthia; Innocenti, Gregory; Norris, Brett; Yuan, Jin; Yu, Jian; Haack, Herbert; Shen, Baiyong; Peng, Chenghong; Li, Hongwei; Zhou, Xinmin; Liu, Xunyang; Rush, John; Comb, Michael J

2011-01-01

330

The SH2 domain of Abl kinases regulates kinase autophosphorylation by controlling activation loop accessibility.  

PubMed

The activity of protein kinases is regulated by multiple molecular mechanisms, and their disruption is a common driver of oncogenesis. A central and almost universal control element of protein kinase activity is the activation loop that utilizes both conformation and phosphorylation status to determine substrate access. In this study, we use recombinant Abl tyrosine kinases and conformation-specific kinase inhibitors to quantitatively analyse structural changes that occur after Abl activation. Allosteric SH2-kinase domain interactions were previously shown to be essential for the leukemogenesis caused by the Bcr-Abl oncoprotein. We find that these allosteric interactions switch the Abl activation loop from a closed to a fully open conformation. This enables the trans-autophosphorylation of the activation loop and requires prior phosphorylation of the SH2-kinase linker. Disruption of the SH2-kinase interaction abolishes activation loop phosphorylation. Our analysis provides a molecular mechanism for the SH2 domain-dependent activation of Abl that may also regulate other tyrosine kinases. PMID:25399951

Lamontanara, Allan Joaquim; Georgeon, Sandrine; Tria, Giancarlo; Svergun, Dmitri I; Hantschel, Oliver

2014-01-01

331

The protein kinase C and protein kinase C related gene families  

Microsoft Academic Search

Protein kinase C is an important target enzyme for lipid second messengers. Recent developments have focused on the tertiary structure analysis of domains present in protein kinase C and in combination with functional approaches such as mutagenesis and domain expression have generated a detailed understanding of the modular mechanism by which lipids cause activation. This provides a reference for the

Lodewijk V Dekker; Ruth H Palmer; Peter J Parker

1995-01-01

332

Number % of Total Undergraduate Number % of Total Freshman** (1s & 2s) 6,461 18% Resident 19,165 67%  

E-print Network

% Sophomore (3s & 4s) 7,171 20% Nonresident 9,343 33% Junior (5s & 6s) 6,900 19% Graduate Senior (7s, 8s & 9s) 7,571 21% Resident 1,561 24% Nondegree 405 1% Nonresident 4,952 76% TOTAL UNDERGRADUATE 28,508 79,236 8,266 1,345 775 299 431 28,508 Graduate 0 12 606 1,278 2,420 1,200 997 6,513 Professional 1 92 285

Ginzel, Matthew

333

Protein kinase C and Src family kinases mediate angiotensin II-induced protein kinase D activation and acute aldosterone production.  

PubMed

Recent evidence has shown a role for the serine/threonine protein kinase D (PKD) in the regulation of acute aldosterone secretion upon angiotensin II (AngII) stimulation. However, the mechanism by which AngII activates PKD remains unclear. In this study, using both pharmacological and molecular approaches, we demonstrate that AngII-induced PKD activation is mediated by protein kinase C (PKC) and Src family kinases in primary bovine adrenal glomerulosa cells and leads to increased aldosterone production. The pan PKC inhibitor Ro 31-8220 and the Src family kinase inhibitors PP2 and Src-1 inhibited both PKD activation and acute aldosterone production. Additionally, like the dominant-negative serine-738/742-to-alanine PKD mutant that cannot be phosphorylated by PKC, the dominant-negative tyrosine-463-to-phenylalanine PKD mutant, which is not phosphorylatable by the Src/Abl pathway, inhibited acute AngII-induced aldosterone production. Taken together, our results demonstrate that AngII activates PKD via a mechanism involving Src family kinases and PKC, to underlie increased aldosterone production. PMID:24859649

Olala, Lawrence O; Shapiro, Brian A; Merchen, Todd C; Wynn, James J; Bollag, Wendy B

2014-07-01

334

Arabidopsis Putative MAP Kinase Kinase Kinases Raf10 and Raf11 are Positive Regulators of Seed Dormancy and ABA Response.  

PubMed

We isolated an Arabidopsis ABA-insensitive mutant, ais143, by activation tagging screen. T-DNA was found to be located in the coding region of a putative mitogen-activated protein (MAP) kinase kinase kinase (MAP3K) gene, Raf10, thereby abolishing its expression in the mutant. ais143 exhibited reduced seed dormancy as well as reduced ABA sensitivity. The phenotypes were complemented by the wild-type Raf10 gene, and the overexpression (OX) of Raf10 resulted in delayed seed germination and enhanced ABA sensitivity. Raf10 has high sequence identity to another MAP3K, Raf11. Parallel analysis of Raf11 knockout (KO) and OX lines showed that their phenotypes were similar to those of Raf10 KO and OX lines. An ais143 raf11 double mutant exhibited stronger phenotypes than single mutants, indicating the functional redundancy between Raf10 and Raf11. Transcript analysis revealed that the expression of many ABA-associated genes, including the key regulatory genes ABI3 and ABI5, was altered in the Raf10 and Raf11 OX lines. Recombinant Raf10 and Raf11 proteins exhibited kinase activity, which was inhibited by the MAP3K inhibitor BAY 43-9006 but not by the MAP2K inhibitor U0126. Collectively, our data indicate that Raf10 and Raf11 kinases are important regulators of seed dormancy and ABA response and that they affect the expression of ABI3, ABI5 and other ABA-regulated genes. PMID:25324504

Lee, Sun-Ji; Lee, Mi Hun; Kim, Jeong-Il; Kim, Soo Young

2015-01-01

335

Hepatoma Cells from Mice Deficient in Glycine N-Methyltransferase Have Increased RAS Signaling and Activation of Liver Kinase B1  

PubMed Central

Background & Aims Patients with cirrhosis are at high risk for developing hepatocellular carcinoma (HCC), and their liver tissues have abnormal levels of adenosylmethionine (SAMe). Glycine N-methyltransferase (GNMT) catabolizes SAMe but its expression is downregulated in HCC cells. Mice that lack GNMT develop fibrosis and hepatomas and have alterations in signaling pathways involved in carcinogenesis. We investigated the role of GNMT in human HCC cell lines and in liver carcinogenesis in mice. Methods We studied hepatoma cells from GNMT knockout mice and analyzed the roles of liver kinase B1 (LKB1, STK11) signaling via 5'-AMP-activated protein kinase (AMPK) and Ras in regulating proliferation and transformation. Results Hepatoma cells from GNMT mice had defects in LKB1 signaling to AMPK, making them resistant to induction of apoptosis by cAMP activation of protein kinase A and calcium/calmodulin-dependent protein kinase kinase-2. Ras-mediated hyperactivation of LKB1 promoted proliferation of GNMT-deficient hepatoma cells, and required mitogen-activated protein kinase-2 (ERK) and ribosomal protein S6 kinase polypeptide-2 (p90RSK). Ras activation of LKB1 required expression of RAS guanyl releasing protein-3 (RASGRP3). Reduced levels of GNMT and phosphorylation of AMPK? at Thr172 and increased levels of Ras, LKB1, and RASGRP3 in HCC samples from patients were associated with shorter survival times. Conclusions Reduced expression of GNMT in mouse hepatoma cells and human HCC cells appears to increase activity of LKB1 and RAS; activation of RAS signaling to LKB1 and RASGRP3, via ERK and p90RSK, might be involved in liver carcinogenesis and be used as a prognostic marker. Reagents that disrupt this pathway might be developed to treat patients with HCC. PMID:22687285

Martínez-López, Nuria; García-Rodríguez, Juan L; Varela-Rey, Marta; Gutiérrez, Virginia; Fernández-Ramos, David; Beraza, Naiara; Aransay, Ana M; Schlangen, Karin; Lozano, Juan Jose; Aspichueta, Patricia; Luka, Zigmund; Wagner, Conrad; Evert, Matthias; Calvisi, Diego F; Lu, Shelly C; Mato, José M; Martínez-Chantar, María L

2012-01-01

336

Differently Spliced cDNAs of Human Leukocyte Tyrosine Kinase Receptor Tyrosine Kinase Predict Receptor Proteins with and without a Tyrosine Kinase Domain and a Soluble Receptor Protein  

Microsoft Academic Search

Leukocyte tyrosine kinase (LTK) is a tyrosine kinase that has been suggested to be specific for hematopoietic cells and neuronal cells and reported as an unusual membrane protein lacking an extracellular domain. Here we report the cloning of a human LTK cDNA clone containing the complete open reading frame of a putative receptor tyrosine kinase protein. The extracellular domain of

Hideo Toyoshima; Hiroyuki Kozutsumi; Yoshiro Maru; Koichi Hagiwara; Akiko Furuya; Hiroyuki Mioh; Nobuo Hanai; Fumimaro Takaku; Yoshio Yazaki; Hisamaru Hirai

1993-01-01

337

Crystal Structure of Cryptosporidium parvum Pyruvate Kinase  

PubMed Central

Pyruvate kinase plays a critical role in cellular metabolism of glucose by serving as a major regulator of glycolysis. This tetrameric enzyme is allosterically regulated by different effector molecules, mainly phosphosugars. In response to binding of effector molecules and substrates, significant structural changes have been identified in various pyruvate kinase structures. Pyruvate kinase of Cryptosporidium parvum is exceptional among known enzymes of protozoan origin in that it exhibits no allosteric property in the presence of commonly known effector molecules. The crystal structure of pyruvate kinase from C. parvum has been solved by molecular replacement techniques and refined to 2.5 Å resolution. In the active site a glycerol molecule is located near the ?-phosphate site of ATP, and the protein structure displays a partially closed active site. However, unlike other structures where the active site is closed, the ?6' helix in C. parvum pyruvate kinase unwinds and assumes an extended conformation. In the crystal structure a sulfate ion is found at a site that is occupied by a phosphate of the effector molecule in many pyruvate kinase structures. A new feature of the C. parvum pyruvate kinase structure is the presence of a disulfide bond cross-linking the two monomers in the asymmetric unit. The disulfide bond is formed between cysteine residue 26 in the short N-helix of one monomer with cysteine residue 312 in a long helix (residues 303–320) of the second monomer at the interface of these monomers. Both cysteine residues are unique to C. parvum, and the disulfide bond remained intact in a reduced environment. However, the significance of this bond, if any, remains unknown at this time. PMID:23056503

Cook, William J.; Senkovich, Olga; Aleem, Khadijah; Chattopadhyay, Debasish

2012-01-01

338

Activation of AMP-Activated Protein Kinase by AICAR Prevents Leucine Stimulated Protein Synthesis in Rat Skeletal Muscle1  

PubMed Central

Several stress conditions are characterized by activation of 5?-AMP-protein kinase (AMPK) and the development of leucine resistance in skeletal muscle. The present study determined whether direct activation of the AMPK by AICAR prevents the characteristic leucine-induced increase in protein synthesis by altering mTOR (mammalian target of rapamycin) signal transduction. Rats were injected with AICAR or saline and 1 h thereafter received an oral gavage of leucine (or saline). Efficacy of AICAR was verified by increased AMPK phosphorylation. AICAR decreased basal in vivo muscle (gastrocnemius) protein synthesis and completely prevented the leucine-induced increase, independent of a change in muscle adenine nucleotide concentration. AICAR also prevented the hyperphosphorylation of eukaryotic initiation factor (eIF) 4E binding protein (4E-BP1), ribosomal protein S6 kinase (S6K1), S6, and eIF4G in response to leucine suggesting a decrease in mTOR activity. Moreover, AICAR prevented the leucine-induced redistribution of eIF4E from the inactive eIF4E·4E-BP1 to the active eIF4E·eIF4G complex. This ability of AICAR to produce muscle leucine resistance could not be attributed to a change in phosphorylation of tuberous sclerosis complex (TSC)2, the formation of a TSC1·TSC2 complex, or the binding of raptor with mTOR, or the phosphorylation of eukaryotic elongation factor-2. However, the inhibitory actions of AICAR were associated with a reduction in the phosphorylation of proline-rich Akt substrate (PRAS)-40 and increased phosphorylation of raptor, and these represent potential mechanisms by which AICAR might be expected to inhibit leucine-induced increases in mTOR activity and protein synthesis under in vivo conditions. PMID:18806097

Pruznak, Anne M.; Kazi, Abid A.; Frost, Robert A.; Vary, Thomas C.; Lang, Charles H.

2008-01-01

339

Sphingosine kinase inhibition exerts both pro- and anti-atherogenic effects in low-density lipoprotein receptor-deficient (LDL-R(-/-)) mice.  

PubMed

Sphingosine 1-phosphate (S1P), a lysosphingolipid associated with high-density lipoprotein (HDL), contributes to the anti-atherogenic potential attributed to this lipoprotein. This study examined whether a reduction of S1P plasma levels affects atherosclerosis in a murine model of disease. LDL-R(-/-)mice on Western diet were given ABC294640, an inhibitor of sphingosine kinase (SphK) for 16 weeks. ABC294640 decreased plasma S1P by approximately 30%. However, ABC294640 failed to affect atherosclerotic lesion formation. Plasma triglycerides were reduced whereas total and HDL-cholesterol remained unchanged in course of ABC294640 treatment. ABC294640 increased plasma interleukin (IL)-12p70 and RANTES concentration as well as IL-12p70, RANTES and interferon (IFN)-? production by peritoneal cells and this was paralleled by enhanced activity of peritoneal and spleen dendritic cells as evidenced by up-regulation of CD86 and MHC-II on CD11c(+) cells. As a consequence, increased T-cell activation was noted in ABC294640-treated mice as indicated by enhanced CD4(+) splenocyte proliferation, IFN-? and IL-2 production, and CD69 expression. Concomitantly, however, ABC294640 treatment redistributed CD4(+) and CD8(+) cells from blood to lymphatic organs and reduced T-cell number within atherosclerotic lesions. In addition, plasma sVCAM-1, sICAM-1, and MCP-1 levels as well as in vivo leukocyte adhesion and CCL19-induced T-cell penetration into peritoneum were lower in ABC294640-treated animals. In vitro experiments demonstrated reduced VCAM-1 and ICAM-1 expression and lymphocyte adhesion to endothelial cells exposed to ABC294640. In conclusion, treatment with SphK inhibitor leads to both pro- and anti-atherogenic effects in LDL-R(-/-) mice. As a consequence, SphK inhibition fails to affect atherosclerosis despite significant S1P reduction in plasma. PMID:22234485

Poti, Francesco; Bot, Martine; Costa, Sara; Bergonzini, Valeria; Maines, Lynn; Varga, Georg; Freise, Hendrik; Robenek, Horst; Simoni, Manuela; Nofer, Jerzy-Roch

2012-03-01

340

Working Without Kinase Activity: Phosphotransfer-Independent Functions of Extracellular Signal-Regulated Kinases  

NSDL National Science Digital Library

Extracellular signal–regulated kinase 1 (ERK1) and ERK2 are typical serine and threonine kinases that are members of the family of mitogen-activated protein kinases and are involved in the regulation of key cellular processes, including proliferation, differentiation, and survival, through the phosphorylation of nearly 200 substrates. However, accumulating evidence demonstrates that ERK1 and ERK2 can also function independently of their kinase activities in the control of critical biochemical and biological events, such as chromatin remodeling, DNA transcription, and cell cycle regulation. In this Review, which contains 1 figure and 72 references, we summarize findings from a number of studies that underline the importance of these kinase-independent roles of the ERKs.

Javier Rodriguez (Spain; Universidad de Cantabria REV)

2011-10-25

341

X-Ray Crystal Structure of Bone Marrow Kinase in the X Chromosome: A Tec Family Kinase  

SciTech Connect

Bone marrow kinase in the X chromosome, a member of the Tec family of tyrosine kinases, plays a role in both monocyte/macrophage trafficking as well as cytokine secretion. Although the structures of Tec family kinases Bruton's tyrosine kinase and IL-2-inducible T-cell kinase are known, the crystal structures of other Tec family kinases have remained elusive. We report the X-ray crystal structures of bone marrow kinase in the X chromosome in complex with dasatinib at 2.4 {angstrom} resolution and PP2 at 1.9 {angstrom} resolution. The bone marrow kinase in the X chromosome structures reveal a typical kinase protein fold; with well-ordered protein conformation that includes an open/extended activation loop and a stabilized DFG-motif rendering the kinase in an inactive conformation. Dasatinib and PP2 bind to bone marrow kinase in the X chromosome in the ATP binding pocket and display similar binding modes to that observed in other Tec and Src protein kinases. The bone marrow kinase in the X chromosome structures identify conformational elements of the DFG-motif that could potentially be utilized to design potent and/or selective bone marrow kinase in the X chromosome inhibitors.

Muckelbauer, Jodi; Sack, John S.; Ahmed, Nazia; Burke, James; Chang, ChiehYing Y.; Gao, Mian; Tino, Joseph; Xie, Dianlin; Tebben, Andrew J. (BMS)

2012-06-27

342

A PI3-Kinase–Mediated Negative Feedback Regulates Neuronal Excitability  

PubMed Central

Use-dependent downregulation of neuronal activity (negative feedback) can act as a homeostatic mechanism to maintain neuronal activity at a particular specified value. Disruption of this negative feedback might lead to neurological pathologies, such as epilepsy, but the precise mechanisms by which this feedback can occur remain incompletely understood. At one glutamatergic synapse, the Drosophila neuromuscular junction, a mutation in the group II metabotropic glutamate receptor gene (DmGluRA) increased motor neuron excitability by disrupting an autocrine, glutamate-mediated negative feedback. We show that DmGluRA mutations increase neuronal excitability by preventing PI3 kinase (PI3K) activation and consequently hyperactivating the transcription factor Foxo. Furthermore, glutamate application increases levels of phospho-Akt, a product of PI3K signaling, within motor nerve terminals in a DmGluRA-dependent manner. Finally, we show that PI3K increases both axon diameter and synapse number via the Tor/S6 kinase pathway, but not Foxo. In humans, PI3K and group II mGluRs are implicated in epilepsy, neurofibromatosis, autism, schizophrenia, and other neurological disorders; however, neither the link between group II mGluRs and PI3K, nor the role of PI3K-dependent regulation of Foxo in the control of neuronal excitability, had been previously reported. Our work suggests that some of the deficits in these neurological disorders might result from disruption of glutamate-mediated homeostasis of neuronal excitability. PMID:19043547

Howlett, Eric; Lin, Curtis Chun-Jen; Lavery, William; Stern, Michael

2008-01-01

343

Gibberellin-regulated expression in oat aleurone cells of two kinases that show homology to MAP kinase and a ribosomal protein kinase  

Microsoft Academic Search

cDNA fragments from ten different protein kinases expressed in Avena sativa aleurone cells were amplified from mRNA by RT-PCR with degenerate primers. These could be classified into five groups: Aspk1-3 showed homology to the Snf1-related protein kinases, Aspk4-5 to a wheat ABA up-regulated protein kinase, Aspk6-8 to the Ca-dependent, calmodulin-independent protein kinase family, Aspk9 encoded a MAP kinase and Aspk10

Alison K. Huttly; Andrew L. Phillips

1995-01-01

344

Activation of mammalian target of rapamycin contributes to pain nociception induced in rats by BmK I, a sodium channel-specific modulator.  

PubMed

The mammalian target of rapamycin (mTOR) pathway is essential for maintenance of the sensitivity of certain adult sensory neurons. Here, we investigated whether the mTOR cascade is involved in scorpion envenomation-induced pain hypersensitivity in rats. The results showed that intraplantar injection of a neurotoxin from Buthus martensii Karsch, BmK I (10 ?g), induced the activation of mTOR, as well as its downstream molecules p70 ribosomal S6 protein kinase (p70 S6K) and eukaryotic initiation factor 4E-binding protein 1 (4E-BP1), in lumbar 5-6 dorsal root ganglia neurons on both sides in rats. The activation peaked at 2 h and recovered 1 day after injection. Compared with the control group, the ratios of p-mTOR/p-p70 S6K/p-4EBP1 in three types of neurons changed significantly. The cell typology of p-mTOR/p-p70 S6K/p-4E-BP1 immuno-reactive neurons also changed. Intrathecal administration of deforolimus, a specific inhibitor of mTOR, attenuated BmK I-induced pain responses (spontaneous flinching, paroxysmal pain-like behavior, and mechanical hypersensitivity). Together, these results imply that the mTOR signaling pathway is mobilized by and contributes to experimental scorpion sting-induced pain. PMID:24132796

Jiang, Feng; Hua, Li-Ming; Jiao, Yun-Lu; Ye, Pin; Fu, Jin; Cheng, Zhi-Jun; Ding, Gang; Ji, Yong-Hua

2014-02-01

345

Structural Evolution of the Protein Kinase–Like Superfamily  

PubMed Central

The protein kinase family is large and important, but it is only one family in a larger superfamily of homologous kinases that phosphorylate a variety of substrates and play important roles in all three superkingdoms of life. We used a carefully constructed structural alignment of selected kinases as the basis for a study of the structural evolution of the protein kinase–like superfamily. The comparison of structures revealed a “universal core” domain consisting only of regions required for ATP binding and the phosphotransfer reaction. Remarkably, even within the universal core some kinase structures display notable changes, while still retaining essential activity. Hence, the protein kinase–like superfamily has undergone substantial structural and sequence revision over long evolutionary timescales. We constructed a phylogenetic tree for the superfamily using a novel approach that allowed for the combination of sequence and structure information into a unified quantitative analysis. When considered against the backdrop of species distribution and other metrics, our tree provides a compelling scenario for the development of the various kinase families from a shared common ancestor. We propose that most of the so-called “atypical kinases” are not intermittently derived from protein kinases, but rather diverged early in evolution to form a distinct phyletic group. Within the atypical kinases, the aminoglycoside and choline kinase families appear to share the closest relationship. These two families in turn appear to be the most closely related to the protein kinase family. In addition, our analysis suggests that the actin-fragmin kinase, an atypical protein kinase, is more closely related to the phosphoinositide-3 kinase family than to the protein kinase family. The two most divergent families, ?-kinases and phosphatidylinositol phosphate kinases (PIPKs), appear to have distinct evolutionary histories. While the PIPKs probably have an evolutionary relationship with the rest of the kinase superfamily, the relationship appears to be very distant (and perhaps indirect). Conversely, the ?-kinases appear to be an exception to the scenario of early divergence for the atypical kinases: they apparently arose relatively recently in eukaryotes. We present possible scenarios for the derivation of the ?-kinases from an extant kinase fold. PMID:16244704

2005-01-01

346

Role of Protein Kinase C, PI3-kinase and Tyrosine Kinase in Activation of MAP Kinase by Glucose and Agonists of G-protein Coupled Receptors in INS-1 Cells  

PubMed Central

MAP (mitogen-activated protein) kinase (also called Erk 1/2) plays a crucial role in cell proliferation and differentiation. Its impact on secretory events is less well established. The interplay of protein kinase C (PKC), PI3-kinase nd cellular tyrosine kinase with MAP kinase activity using inhibitors and compounds such as glucose, phorbol 12-myristate 13-acetate (PMA) and agonists of G-protein coupled receptors like gastrin releasing peptide (GRP), oxytocin (OT) and glucose-dependent insulinotropic peptide (GIP) was investigated in INS-1 cells, an insulin secreting cell line. MAP kinase activity was determined by using a peptide derived from the EGF receptor as a MAP kinase substrate and [ P 32 ]ATP. Glucose as well as GRP, OT and GIP exhibited a time-dependent increase in MAP kinase activity with a maximum at time point 2.5 min. All further experiments were performed using 2.5 min incubations. The flavone PD 098059 is known to bind to the inactive forms of MEK1 (MAPK/ERK-Kinase) thus preventing activation by upstream activators. 20 ?M PD 098059 ( IC 50 =51 ?M) inhibited MAP kinase stimulated by either glucose, GRP, OT, GIP or PMA. Inhibiton (“downregulation”) of PKC by a long term (22h) pretreatment with 1 ?M PMA did not influence MAP kinase activity when augmented by either of the above mentioned compound. To investigate whether PI3-kinase and cellular tyrosine kinase are involved in G-protein mediated effects on MAP kinase, inhibitors were used: 100 nM wortmannin (PI3-kinase inhibitor) reduced the effects of GRP, OT and GIP but not that of PMA; 100 ?M genistein (tyrosine kinase inhibitor) inhibited the stimulatory effect of either above mentioned compound on MAP kinase activation. Inhibition of MAP kinase by 20 ?M PD 098059 did not influence insulin secretion modulated by either compound (glucose, GRP, OT or GIP). [ H 3 ]Thymidine incorporation, however, was severely inhibited by PD 098059. Thus MAP kinase is important for INS-1 cell proliferation but not for its insulin secretory response with respect to major initiators and modulators of insulin release. The data indicate that MAP kinase is active and under the control of MAP kinase. PKC is upstream of a genisteinsensitive tyrosine kinase and probably downstream of a PI3-kinase in INS-1 cells. PMID:12369712

Böcker, Dietmar

2001-01-01

347

Role of protein kinase C, PI3-kinase and tyrosine kinase in activation of MAP kinase by glucose and agonists of G-protein coupled receptors in INS-1 cells.  

PubMed

MAP (mitogen-activated protein) kinase (also called Erk 1/2) plays a crucial role in cell proliferation and differentiation. Its impact on secretory events is less well established. The interplay of protein kinase C (PKC), PI3-kinase and cellular tyrosine kinase with MAP kinase activity using inhibitors and compounds such as glucose, phorbol 12-myristate 13-acetate (PMA) and agonists of G-protein coupled receptors like gastrin releasing peptide (GRP), oxytocin (OT) and glucose-dependent insulinotropic peptide (GIP) was investigated in INS-1 cells, an insulin secreting cell line. MAP kinase activity was determined by using a peptide derived from the EGF receptor as a MAP kinase substrate and [32P]ATP. Glucose as well as GRP, OT and GIP exhibited a time-dependent increase in MAP kinase activity with a maximum at time point 2.5 min. All further experiments were performed using 2.5 min incubations. The flavone PD 098059 is known to bind to the inactive forms of MEK1 (MAPK/ERK-Kinase) thus preventing activation by upstream activators. 20 microM PD 098059 (IC50 = 5 microM) inhibited MAP kinase stimulated by either glucose, GRP, OT, GIP or PMA. Inhibiton ("downregulation") of PKC by a long term (22 h) pretreatment with 1 microM PMA did not influence MAP kinase activity when augmented by either of the above mentioned compound. To investigate whether PI3-kinase and cellular tyrosine kinase are involved in G-protein mediated effects on MAP kinase, inhibitors were used: 100 nM wortmannin (PI3-kinase inhibitor) reduced the effects of GRP, OT and GIP but not that of PMA; 100 microM genistein (tyrosine kinase inhibitor) inhibited the stimulatory effect of either above mentioned compound on MAP kinase activation. Inhibition of MAP kinase by 20 microM PD 098059 did not influence insulin secretion modulated by either compound (glucose, GRP, OT or GIP). [3H]Thymidine incorporation, however, was severely inhibited by PD 098059. Thus MAP kinase is important for INS-1 cell proliferation but not for its insulin secretory response with respect to major initiators and modulators of insulin release. The data indicate that MAP kinase is active and under the control of MAP kinase. PKC is upstream of a genistein-sensitive tyrosine kinase and probably downstream of a PI3-kinase in INS-1 cells. PMID:12369712

Böcker, D; Verspohl, E J

2001-01-01

348

Targeting protein kinase C in sarcoma.  

PubMed

Protein kinase C (PKC) is a family of serine/threonine tyrosine kinases that regulate many cellular processes including division, proliferation, survival, anoikis and polarity. PKC is abundant in many human cancers and aberrant PKC signalling has been demonstrated in cancer models. On this basis, PKC has become an attractive target for small molecule inhibition within oncology drug development programmes. Sarcoma is a heterogeneous group of mesenchymal malignancies. Due to their relative insensitivity to conventional chemotherapies and the increasing recognition of the driving molecular events of sarcomagenesis, sarcoma provides an excellent platform to test novel therapeutics. In this review we provide a structure-function overview of the PKC family, the rationale for targeting these kinases in sarcoma and the state of play with regard to PKC inhibition in the clinic. PMID:25453364

Martin-Liberal, J; Cameron, A J; Claus, J; Judson, I R; Parker, P J; Linch, M

2014-12-01

349

Exploring the scaffold universe of kinase inhibitors.  

PubMed

The scaffold concept was applied to systematically determine, analyze, and compare core structures of kinase inhibitors. From publicly available inhibitors of the human kinome, scaffolds and cyclic skeletons were systematically extracted and organized taking activity data, structural relationships, and retrosynthetic criteria into account. Scaffold coverage varied greatly across the kinome, and many scaffolds representing compounds with different activity profiles were identified. The majority of kinase inhibitor scaffolds were involved in well-defined yet distinct structural relationships, which had different consequences on compound activity. Scaffolds exclusively representing highly potent compounds were identified as well as structurally analogous scaffolds with very different degrees of promiscuity. Scaffold relationships presented herein suggest a variety of hypotheses for inhibitor design. Our detailed organization of the kinase inhibitor scaffold universe with respect to different activity and structural criteria, all scaffolds, and the original compound data assembled for our analysis are made freely available. PMID:25192260

Hu, Ye; Bajorath, Jürgen

2015-01-01

350

Kinase signaling in the spindle checkpoint.  

PubMed

The spindle checkpoint is a cell cycle surveillance system that ensures the fidelity of chromosome segregation. In mitosis, it elicits the "wait anaphase" signal to inhibit the anaphase-promoting complex or cyclosome until all chromosomes achieve bipolar microtubule attachment and align at the metaphase plate. Because a single kinetochore unattached to microtubules activates the checkpoint, the wait anaphase signal is thought to be generated by this kinetochore and is then amplified and distributed throughout the cell to inhibit the anaphase-promoting complex/cyclosome. Several spindle checkpoint kinases participate in the generation and amplification of this signal. Recent studies have begun to reveal the activation mechanisms of these checkpoint kinases. Increasing evidence also indicates that the checkpoint kinases not only help to generate the wait anaphase signal but also actively correct kinetochore-microtubule attachment defects. PMID:19228686

Kang, Jungseog; Yu, Hongtao

2009-06-01

351

Dual-specificity MAP kinase phosphatases (MKPs)  

PubMed Central

Dual-specificity MAP kinase phosphatases (MKPs) provide a complex negative regulatory network that acts to shape the duration, magnitude and spatiotemporal profile of MAP kinase activities in response to both physiological and pathological stimuli. Individual MKPs may exhibit either exquisite specificity towards a single mitogen-activated protein kinase (MAPK) isoform or be able to regulate multiple MAPK pathways in a single cell or tissue. They can act as negative feedback regulators of MAPK activity, but can also provide mechanisms of crosstalk between distinct MAPK pathways and between MAPK signalling and other intracellular signalling modules. In this review, we explore the current state of knowledge with respect to the regulation of MKP expression levels and activities, the mechanisms by which individual MKPs recognize and interact with different MAPK isoforms and their role in the spatiotemporal regulation of MAPK signalling. PMID:22812510

Caunt, Christopher J; Keyse, Stephen M

2013-01-01

352

Long term exposure to L-arginine accelerates endothelial cell senescence through arginase-II and S6K1 signaling.  

PubMed

L-arginine supplementation is proposed to improve health status or as adjunct therapy for diseases including cardiovascular diseases. However, controversial results and even detrimental effects of L-arginine supplementation are reported. We investigate potential mechanisms of L-arginine-induced detrimental effects on vascular endothelial cells. Human endothelial cells were exposed to a physiological (0.1 mmol/L) or pharmacological (0.5 mmol/L) concentration of L-arginine for 30 minutes (acute) or 7 days (chronic). The effects of L-arginine supplementation on endothelial senescence phenotype, i.e., levels of senescence-associated beta-galactosidase, expression of vascular cell adhesion molecule-1 and intercellular adhesion molecule-1, eNOS-uncoupling, arginase-II expression/activity, and mTORC1-S6K1 activity were analyzed. While acute L-arginine treatment enhances endothelial NO production accompanied with superoxide production and activation of S6K1 but no up-regulation of arginase-II, chronic L-arginine supplementation causes endothelial senescence, up-regulation of the adhesion molecule expression, and eNOS-uncoupling (decreased NO and enhanced superoxide production), which are associated with S6K1 activation and up-regulation of arginase-II. Silencing either S6K1 or arginase-II inhibits up-regulation/activation of each other, prevents endothelial dysfunction, adhesion molecule expression, and senescence under the chronic L-arginine supplementation condition. These results demonstrate that S6K1 and arginase-II form a positive circuit mediating the detrimental effects of chronic L-arginine supplementation on endothelial cells. PMID:24860943

Xiong, Yuyan; Fru, Michael Forbiteh; Yu, Yi; Montani, Jean-Pierre; Ming, Xiu-Fen; Yang, Zhihong

2014-05-01

353

Phosphorylation of the kinase interaction motif in mitogen-activated protein (MAP) kinase phosphatase-4 mediates cross-talk between protein kinase A and MAP kinase signaling pathways.  

PubMed

MAP kinase phosphatase 4 (DUSP9/MKP-4) plays an essential role during placental development and is one of a subfamily of three closely related cytoplasmic dual-specificity MAPK phosphatases, which includes the ERK-specific enzymes DUSP6/MKP-3 and DUSP7/MKP-X. However, unlike DUSP6/MKP-3, DUSP9/MKP-4 also inactivates the p38? MAP kinase both in vitro and in vivo. Here we demonstrate that inactivation of both ERK1/2 and p38? by DUSP9/MKP-4 is mediated by a conserved arginine-rich kinase interaction motif located within the amino-terminal non-catalytic domain of the protein. Furthermore, DUSP9/MKP-4 is unique among these cytoplasmic MKPs in containing a conserved PKA consensus phosphorylation site (55)RRXSer-58 immediately adjacent to the kinase interaction motif. DUSP9/MKP-4 is phosphorylated on Ser-58 by PKA in vitro, and phosphorylation abrogates the binding of DUSP9/MKP-4 to both ERK2 and p38? MAP kinases. In addition, although mutation of Ser-58 to either alanine or glutamic acid does not affect the intrinsic catalytic activity of DUSP9/MKP-4, phospho-mimetic (Ser-58 to Glu) substitution inhibits both the interaction of DUSP9/MKP-4 with ERK2 and p38? in vivo and its ability to dephosphorylate and inactivate these MAP kinases. Finally, the use of a phospho-specific antibody demonstrates that endogenous DUSP9/MKP-4 is phosphorylated on Ser-58 in response to the PKA agonist forskolin and is also modified in placental tissue. We conclude that DUSP9/MKP-4 is a bona fide target of PKA signaling and that attenuation of DUSP9/MKP-4 function can mediate cross-talk between the PKA pathway and MAPK signaling through both ERK1/2 and p38? in vivo. PMID:21908610

Dickinson, Robin J; Delavaine, Laurent; Cejudo-Marín, Rocío; Stewart, Graeme; Staples, Christopher J; Didmon, Mark P; Trinidad, Antonio Garcia; Alonso, Andrés; Pulido, Rafael; Keyse, Stephen M

2011-11-01

354

Purification and characterization of a casein kinase 2-type protein kinase from pea nuclei  

NASA Technical Reports Server (NTRS)

Almost all the polyamine-stimulated protein kinase activity associated with the chromatin fraction of nuclei purified from etiolated pea (Pisum sativum L.) plumules is present in a single enzyme that can be extracted from chromatin by 0.35 molar NaCl. This protein kinase can be further purified over 2000-fold by salt fractionation and anion-exchange and casein-agarose column chromatography, after which it is more than 90% pure. The purified kinase has a specific activity of about 650 nanomoles per minute per milligram protein in the absence of polyamines, with either ATP or GTP as phosphoryl donor. Spermidine can stimulate its activity fourfold, with half-maximal activation at about 2 millimolar. Spermine and putrescine also stimulate activity, although somewhat less effectively. This kinase has a tetrameric alpha 2 beta 2 structure with a native molecular weight of 130,000, and subunit molecular weights of 36,000 for the catalytic subunit (alpha) and 29,000 for the regulatory subunit (beta). In western blot analyses, only the alpha subunit reacts strongly with polyclonal antibodies to a Drosophila casein kinase II. The pea kinase can use casein and phosvitin as artificial substrates, phosphorylating both the serine and threonine residues of casein. It has a pH optimum near 8.0, a Vmax of 1.5 micromoles per minute per milligram protein, and a Km for ATP of approximately 75 micromolar. Its activity can be almost completely inhibited by heparin at 5 micrograms per milliliter, but is relatively insensitive to concentrations of staurosporine, K252a, and chlorpromazine that strongly antagonize Ca(2+) -regulated protein kinases. These results are discussed in relation to recent findings that casein kinase 2-type kinases may phosphorylate trans-acting factors that bind to light-regulated promoters in plants.

Li, H.; Roux, S. J.

1992-01-01

355

The landscape of kinase fusions in cancer  

PubMed Central

Human cancer genomes harbour a variety of alterations leading to the deregulation of key pathways in tumour cells. The genomic characterization of tumours has uncovered numerous genes recurrently mutated, deleted or amplified, but gene fusions have not been characterized as extensively. Here we develop heuristics for reliably detecting gene fusion events in RNA-seq data and apply them to nearly 7,000 samples from The Cancer Genome Atlas. We thereby are able to discover several novel and recurrent fusions involving kinases. These findings have immediate clinical implications and expand the therapeutic options for cancer patients, as approved or exploratory drugs exist for many of these kinases. PMID:25204415

Stransky, Nicolas; Cerami, Ethan; Schalm, Stefanie; Kim, Joseph L.; Lengauer, Christoph

2014-01-01

356

SIGNAL TRANSDUCTION: Routing MAP Kinase Cascades  

NSDL National Science Digital Library

Access to the article is free, however registration and sign-in are required. Cells need to convey information from signals on their surface to a variety of intracellular targets, including transcription factors, contractile proteins, and enzymes. To do so efficiently, they construct information pathways with enzymes called kinases, using the same enzymes over and over. But what prevents cross talk between pathways? In her Perspective, Elion discusses new results in this issue by Whitmarsh et al. and Schaeffer et al., who identify proteins that act as scaffolds in mouse cells, binding certain kinases to make a pathway for a specific function that is insulated from the rest of the cell.

Elaine A. Elion (Harvard Medical School;Department of Biological Chemistry)

1998-09-11

357

Microfluidic bead-based sensing platform for monitoring kinase activity.  

PubMed

Protein kinases control cellular functions by regulating protein phosphorylation. Monitoring protein kinase activity is essential for medical diagnosis and drug screening. Here, we present a novel microfluidic device for performing simple and versatile protein kinase assays, which utilizes a microbead-based chemosensor. An automatic mix-and-measure technique was achieved using integrated pneumatic valves. After mixing each reagent for the kinase assay, the mixture was transferred to the sensing chamber. Then, phosphorylated and fluorescence-labeled peptides were captured and detected by the chemosensor. A fluorescence signal was observed depending on the presence of the kinase. Furthermore, activities of various kinases in the cell lysate and the inhibitory effect of specific chemicals on the kinases were monitored. These results indicate that chemosensor-based microfluidic chips can be developed as a versatile kinase assay system. PMID:24534574

Lee, Seung Hwan; Rhee, Hyun-Woo; van Noort, Danny; Lee, Hong Jai; Park, Hee Ho; Shin, Ik-Soo; Hong, Jong-In; Park, Tai Hyun

2014-07-15

358

A semisynthetic Eph receptor tyrosine kinase provides insight into ligand-induced kinase activation  

PubMed Central

SUMMARY We have developed a methodology for generating milligram amounts of functional Eph tyrosine kinase receptor using the protein engineering approach of expressed protein ligation. Stimulation with ligand induces efficient autophosphorylation of the semisynthetic Eph construct. The in vitro phosphorylation of key Eph tyrosine residues upon ligand-induced activation was monitored via time-resolved, quantitative phosphoproteomics, suggesting a precise and unique order of phosphorylation of the Eph tyrosines in the kinase activation process. To our knowledge, this work represents the first reported semisynthesis of a receptor tyrosine kinase and provides a potentially general method for producing single-pass membrane proteins for structural and biochemical characterization. PMID:21439481

Singla, Nikhil; Erdjument-Bromage, Hediye; Himanen, Juha P.; Muir, Tom W.; Nikolov, Dimitar B.

2011-01-01

359

Inositol pyrophosphates regulate cell death and telomere length through phosphoinositide 3-kinase-related protein kinases.  

PubMed

Inositol pyrophosphates physiologically regulate vesicular endocytosis, ribosomal disposition, and directly phosphorylate proteins. Here we demonstrate roles in cell death and regulation of telomere length. Lethal actions of wortmannin and caffeine are selectively abolished in yeast mutants that cannot synthesize inositol pyrophosphates. Wortmannin and caffeine appear to act through the phosphoinositide 3-kinase-related protein kinases Tel1 and Mec1, known regulators of telomere length. Inositol pyrophosphates physiologically antagonize the actions of these kinases, which is demonstrated by the fact that yeast mutants with reduced or elevated levels of inositol pyrophosphates, respectively, display longer and shorter telomeres. PMID:15665079

Saiardi, Adolfo; Resnick, Adam C; Snowman, Adele M; Wendland, Beverly; Snyder, Solomon H

2005-02-01

360

Inositol pyrophosphates regulate cell death and telomere length through phosphoinositide 3-kinase-related protein kinases  

PubMed Central

Inositol pyrophosphates physiologically regulate vesicular endocytosis, ribosomal disposition, and directly phosphorylate proteins. Here we demonstrate roles in cell death and regulation of telomere length. Lethal actions of wortmannin and caffeine are selectively abolished in yeast mutants that cannot synthesize inositol pyrophosphates. Wortmannin and caffeine appear to act through the phosphoinositide 3-kinase-related protein kinases Tel1 and Mec1, known regulators of telomere length. Inositol pyrophosphates physiologically antagonize the actions of these kinases, which is demonstrated by the fact that yeast mutants with reduced or elevated levels of inositol pyrophosphates, respectively, display longer and shorter telomeres. PMID:15665079

Saiardi, Adolfo; Resnick, Adam C.; Snowman, Adele M.; Wendland, Beverly; Snyder, Solomon H.

2005-01-01

361

Contribution of casein kinase 2 and spleen tyrosine kinase to CFTR trafficking and protein kinase A-induced activity.  

PubMed

Previously, the pleiotropic "master kinase" casein kinase 2 (CK2) was shown to interact with CFTR, the protein responsible for cystic fibrosis (CF). Moreover, CK2 inhibition abolished CFTR conductance in cell-attached membrane patches, native epithelial ducts, and Xenopus oocytes. CFTR possesses two CK2 phosphorylation sites (S422 and T1471), with unclear impact on its processing and trafficking. Here, we investigated the effects of mutating these CK2 sites on CFTR abundance, maturation, and degradation coupled to effects on ion channel activity and surface expression. We report that CK2 inhibition significantly decreased processing of wild-type (wt) CFTR, with no effect on F508del CFTR. Eliminating phosphorylation at S422 and T1471 revealed antagonistic roles in CFTR trafficking: S422 activation versus T1471 inhibition, as evidenced by a severe trafficking defect for the T1471D mutant. Notably, mutation of Y512, a consensus sequence for the spleen tyrosine kinase (SYK) possibly acting in a CK2 context adjacent to the common CF-causing defect F508del, had a strong effect on both maturation and CFTR currents, allowing the identification of this kinase as a novel regulator of CFTR. These results reinforce the importance of CK2 and the S422 and T1471 residues for regulation of CFTR and uncover a novel regulation of CFTR by SYK, a recognized controller of inflammation. PMID:21930781

Luz, Simão; Kongsuphol, Patthara; Mendes, Ana Isabel; Romeiras, Francisco; Sousa, Marisa; Schreiber, Rainer; Matos, Paulo; Jordan, Peter; Mehta, Anil; Amaral, Margarida D; Kunzelmann, Karl; Farinha, Carlos M

2011-11-01

362

CZK3, a MAP kinase kinase kinase homolog in Cercospora zeae-maydis, regulates cercosporin biosynthesis, fungal development, and pathogenesis.  

PubMed

The fungus Cercospora zeae-maydis causes gray leaf spot of maize and produces cercosporin, a photosensitizing perylenequinone with toxic activity against a broad spectrum of organisms. However, little is known about the biosynthetic pathway or factors that regulate cercosporin production. Analysis of a cDNA subtraction library comprised of genes that are up-regulated during cercosporin synthesis revealed a sequence highly similar to mitogen-activated protein (MAP) kinases in other fungi. Sequencing and conceptual translation of the full-length genomic sequence indicated that the gene, which we designated CZK3, contains a 4,119-bp open reading frame devoid of introns and encodes a 1,373-amino acid sequence that is highly similar to Wis4, a MAP kinase kinase kinase in Schizosaccharomyces pombe. Targeted disruption of CZK3 suppressed expression of genes predicted to participate in cercosporin biosynthesis and abolished cercosporin production. The disrupted mutants grew faster on agar media than the wild type but were deficient in conidiation and elicited only small chlorotic spots on inoculated maize leaves compared with rectangular necrotic lesions incited by the wild type. Complementation of disruptants with the CZK3 open reading frame and flanking sequences restored wild-type levels of conidiation, growth rate, and virulence as well as the ability to produce cercosporin. The results suggest that cercosporin is a virulence factor in C. zeae-maydis during maize pathogenesis, but the pleiotropic effects of CZK3 disruption precluded definitive conclusions. PMID:12971599

Shim, Won-Bo; Dunkle, Larry D

2003-09-01

363

Kinase detection with gallium nitride based high electron mobility transistors  

NASA Astrophysics Data System (ADS)

A label-free kinase detection system was fabricated by the adsorption of gold nanoparticles functionalized with kinase inhibitor onto AlGaN/GaN high electron mobility transistors (HEMTs). The HEMTs were operated near threshold voltage due to the greatest sensitivity in this operational region. The Au NP/HEMT biosensor system electrically detected 1 pM SRC kinase in ionic solutions. These results are pertinent to drug development applications associated with kinase sensing.

Makowski, Matthew S.; Bryan, Isaac; Sitar, Zlatko; Arellano, Consuelo; Xie, Jinqiao; Collazo, Ramon; Ivanisevic, Albena

2013-07-01

364

Issues and progress with protein kinase inhibitors for cancer treatment  

Microsoft Academic Search

Identification of the key roles of protein kinases in cancer has led to extensive efforts to develop kinase inhibitors for the treatment of a wide range of cancers, and more than 30 such agents are now in clinical trials. Here, we consider the crucial issues in the development of kinase inhibitors for cancer, and discuss strategies to address the challenges

Janet Dancey; Edward A. Sausville

2003-01-01

365

The Roles of Protein Kinases in Learning and Memory  

ERIC Educational Resources Information Center

In the adult mammalian brain, more than 250 protein kinases are expressed, but only a few of these kinases are currently known to enable learning and memory. Based on this information it appears that learning and memory-related kinases either impact on synaptic transmission by altering ion channel properties or ion channel density, or regulate…

Giese, Karl Peter; Mizuno, Keiko

2013-01-01

366

Mnk kinase pathway: Cellular functions and biological outcomes  

PubMed Central

The mitogen-activated protein kinase (MAPK) interacting protein kinases 1 and 2 (Mnk1 and Mnk2) play important roles in controlling signals involved in mRNA translation. In addition to the MAPKs (p38 or Erk), multiple studies suggest that the Mnk kinases can be regulated by other known kinases such as Pak2 and/or other unidentified kinases by phosphorylation of residues distinct from the sites phosphorylated by the MAPKs. Several studies have established multiple Mnk protein targets, including PSF, heterogenous nuclear ribonucleoprotein A1, Sprouty 2 and have lead to the identification of distinct biological functions and substrate specificity for the Mnk kinases. In this review we discuss the pathways regulating the Mnk kinases, their known substrates as well as the functional consequences of engagement of pathways controlled by Mnk kinases. These kinases play an important role in mRNA translation via their regulation of eukaryotic initiation factor 4E (eIF4E) and their functions have important implications in tumor biology as well as the regulation of drug resistance to anti-oncogenic therapies. Other studies have identified a role for the Mnk kinases in cap-independent mRNA translation, suggesting that the Mnk kinases can exert important functional effects independently of the phosphorylation of eIF4E. The role of Mnk kinases in inflammation and inflammation-induced malignancies is also discussed. PMID:25225600

Joshi, Sonali; Platanias, Leonidas C

2014-01-01

367

Structural Evolution of the Protein Kinase-Like Superfamily  

Microsoft Academic Search

The protein kinase family is large and important, but it is only one family in a larger superfamily of homologous kinases that phosphorylate a variety of substrates and play important roles in all three superkingdoms of life. We used a carefully constructed structural alignment of selected kinases as the basis for a study of the structural evolution of the protein

Eric D. Scheeff; Philip E. Bourne

2005-01-01

368

The Energy Landscape Analysis of Cancer Mutations in Protein Kinases  

Microsoft Academic Search

The growing interest in quantifying the molecular basis of protein kinase activation and allosteric regulation by cancer mutations has fueled computational studies of allosteric signaling in protein kinases. In the present study, we combined computer simulations and the energy landscape analysis of protein kinases to characterize the interplay between oncogenic mutations and locally frustrated sites as important catalysts of allostetric

Anshuman Dixit; Gennady M. Verkhivker; Jie Zheng

2011-01-01

369

Problem-Solving Test: "In Vitro" Protein Kinase A Reaction  

ERIC Educational Resources Information Center

Phosphorylation of proteins by protein kinases is an important mechanism in the regulation of protein activity. Among hundreds of protein kinases present in human cells, PKA, the first kinase discovered, belongs to the most important and best characterized group of these enzymes. The author presents an experiment that analyzes the "in vitro"…

Szeberenyi, Jozsef

2009-01-01

370

Update on Calcium Signaling Calcium Signaling through Protein Kinases. The  

E-print Network

Update on Calcium Signaling Calcium Signaling through Protein Kinases. The Arabidopsis Calcium protein kinase activities occur through calcium-dependent protein kinases (CDPKs). These novel calcium provides a valuable opportunity to understand the plant calcium-signaling network. Calcium is a ubiquitous

Sheen, Jen

371

Nephrin mediates actin reorganization via phosphoinositide 3-kinase in podocytes  

Microsoft Academic Search

Nephrin is a slit diaphragm protein critical for structural and functional integrity of visceral glomerular epithelial cells (podocytes) and is known to be tyrosine phosphorylated by Src family kinases. We studied the role of phosphoinositide 3-kinase (PI3K), activated via the phosphorylation of nephrin, in actin cytoskeletal reorganization of cultured rat podocytes. Phosphorylation of rat nephrin by the Fyn kinase markedly

J Zhu; N Sun; L Aoudjit; H Li; H Kawachi; S Lemay; T Takano

2008-01-01

372

The Dictyostelium Mitogen-activated Protein Kinase ERK2  

E-print Network

The Dictyostelium Mitogen- activated Protein Kinase ERK2 Is Regulated by Ras and cAMP- dependent kinase ERK2 activity (1). In this study we show that other pathways required for aggregation, including Ras and cAMP-dependent protein kinase (PKA), are impor- tant regulators of ERK2 activation

Devreotes, Peter

373

An integrated pharmacokineticpharmacodynamic model for an Aurora kinase inhibitor  

E-print Network

An integrated pharmacokinetic­pharmacodynamic model for an Aurora kinase inhibitor Hiroko Kamei of chromosomes prior to cell division at mitosis. Aurora kinases play critical roles in mitotic progression and hence small-molecule inhibitors of Aurora kinases have been developed as a new class of potential anti

Davidson, Fordyce A.

374

Regulation of the mitogen-activated protein kinase kinase (MEK)-1 by NAD(+)-dependent deacetylases.  

PubMed

Sirtuins are class III deacetylases that regulate many essential processes, including cellular stress, genome stability and metabolism. Although these NAD(+)-dependent deacetylases control adaptive cellular responses, identification of sirtuin-regulated signaling targets remain under-studied. Here, we demonstrate that acetylation of the mitogen-activated protein kinase kinase-1 (MEK1) stimulates its kinase activity, and that acetylated MEK1 is under the regulatory control of the sirtuin family members SIRT1 and SIRT2. Treatment of cells with sirtuin inhibitors, or siRNA knockdown of SIRT1 or SIRT2 proteins, increases MEK1 acetylation and subsequent phosphorylation of the extracellular signal-regulated kinase. Generation of an acetyl-specific MEK1 antibody demonstrates that endogenous acetylated MEK1 is extensively enriched in the nucleus following epidermal growth factor  stimulation. An acetyl-mimic of MEK1 increases inappropriate growth properties, suggesting that acetylation of MEK1 has oncogenic potential. PMID:24681949

Yeung, F; Ramsey, C S; Popko-Scibor, A E; Allison, D F; Gray, L G; Shin, M; Kumar, M; Li, D; McCubrey, J A; Mayo, M W

2015-02-01

375

Crystal Structure of the Protein Kinase Domain of Yeast AMP-Activated Protein Kinase Snf1  

SciTech Connect

AMP-activated protein kinase (AMPK) is a master metabolic regulator, and is an important target for drug development against diabetes, obesity, and other diseases. AMPK is a hetero-trimeric enzyme, with a catalytic ({alpha}) subunit, and two regulatory ({beta} and {gamma}) subunits. Here we report the crystal structure at 2.2 Angstrom resolution of the protein kinase domain (KD) of the catalytic subunit of yeast AMPK (commonly known as SNF1). The Snf1-KD structure shares strong similarity to other protein kinases, with a small N-terminal lobe and a large C-terminal lobe. Two negative surface patches in the structure may be important for the recognition of the substrates of this kinase.

Rudolph,M.; Amodeo, G.; Bai, Y.; Tong, L.

2005-01-01

376

Mitogen-Activated Protein Kinase Pathways Mediated by ERK, JNK, and p38 Protein Kinases  

NSDL National Science Digital Library

Multicellular organisms have three well-characterized subfamilies of mitogen-activated protein kinases (MAPKs) that control a vast array of physiological processes. These enzymes are regulated by a characteristic phosphorelay system in which a series of three protein kinases phosphorylate and activate one another. The extracellular signalâÂÂregulated kinases (ERKs) function in the control of cell division, and inhibitors of these enzymes are being explored as anticancer agents. The c-Jun amino-terminal kinases (JNKs) are critical regulators of transcription, and JNK inhibitors may be effective in control of rheumatoid arthritis. The p38 MAPKs are activated by inflammatory cytokines and environmental stresses and may contribute to diseases like asthma and autoimmunity.

Gary Johnson (University of Colorado Health Sciences Center;Department of Pharmacology); Razvan Lapadat (University of Colorado Health Sciences Center;Department of Pharmacology)

2002-12-06

377

Evidence that phosphatidylinositol 3-kinase is involved in sperm-induced tyrosine kinase signaling in Xenopus egg fertilization  

Microsoft Academic Search

BACKGROUND: Studies have examined the function of PI 3-kinase in the early developmental processes that operate in oocytes or early embryos of various species. However, the roles of egg-associated PI 3-kinase and Akt, especially in signal transduction at fertilization, are not well understood. RESULTS: Here we show that in Xenopus eggs, a potent inhibitor of phosphatidylinositol 3-kinase (PI 3-kinase), LY294002

Gunay Mammadova; Tetsushi Iwasaki; Alexander A Tokmakov; Yasuo Fukami; Ken-ichi Sato

2009-01-01

378

Multisite Phosphorylation of the alpha Subunit of Transducin by the Insulin Receptor Kinase and Protein Kinase C  

Microsoft Academic Search

The GDP-bound alpha subunit of transducin, but not the guanosine 5'-[gamma -thio]triphosphate-bound one, undergoes phosphorylation on tyrosine residues by the insulin receptor kinase and on serine residues by protein kinase C. Holotransducin is poorly phosphorylated by the insulin receptor kinase and is not phosphorylated by protein kinase C. Neither holotransducin nor any of its subunits were phosphorylated by the cAMP-dependent

Yehiel Zick; Ronit Sagi-Eisenberg; Mark Pines; Peter Gierschik; Allen M. Spiegel

1986-01-01

379

Mycobacterium tuberculosis Serine/Threonine Protein Kinases.  

PubMed

The Mycobacterium tuberculosis genome encodes 11 serine/threonine protein kinases (STPKs). A similar number of two-component systems are also present, indicating that these two signal transduction mechanisms are both important in the adaptation of this bacterial pathogen to its environment. The M. tuberculosis phosphoproteome includes hundreds of Ser- and Thr-phosphorylated proteins that participate in all aspects of M. tuberculosis biology, supporting a critical role for the STPKs in regulating M. tuberculosis physiology. Nine of the STPKs are receptor type kinases, with an extracytoplasmic sensor domain and an intracellular kinase domain, indicating that these kinases transduce external signals. Two other STPKs are cytoplasmic and have regulatory domains that sense changes within the cell. Structural analysis of some of the STPKs has led to advances in our understanding of the mechanisms by which these STPKs are activated and regulated. Functional analysis has provided insights into the effects of phosphorylation on the activity of several proteins, but for most phosphoproteins the role of phosphorylation in regulating function is unknown. Major future challenges include characterizing the functional effects of phosphorylation for this large number of phosphoproteins, identifying the cognate STPKs for these phosphoproteins, and determining the signals that the STPKs sense. Ultimately, combining these STPK-regulated processes into larger, integrated regulatory networks will provide deeper insight into M. tuberculosis adaptive mechanisms that contribute to tuberculosis pathogenesis. Finally, the STPKs offer attractive targets for inhibitor development that may lead to new therapies for drug-susceptible and drug-resistant tuberculosis. PMID:25429354

Prisic, Sladjana; Husson, Robert N

2014-10-01

380

The Protein Kinase Complementof the Human Genome  

Microsoft Academic Search

We have catalogued the protein kinase complement of the human genome (the ``kinome'') using public and proprietary genomic, complementary DNA, and expressed sequence tag (EST) sequences. This provides a starting point for comprehensive analysis of protein phosphorylation in normal and disease states, as well as a detailed view of the current state of human genome analysis through a focus on

G. Manning; D. B. Whyte; R. Martinez; T. Hunter; S. Sudarsanam

2002-01-01

381

Protein Kinase C Isoform Diversity in Preconditioning  

Microsoft Academic Search

Protein kinase C (PKC) appears to be a common intracellular effector and signal collector during cardiac preconditioning; however, it remains unknown whether agonists that activate different PKC isoforms are also linked to select aspects of myocardial protection. Using agonists that are known to activate unique combinations of PKC isoforms, we interogated the relationship between isoform activation and the different aspects

Daniel R. Meldrum; Joseph C. Cleveland; Xianzhong Meng; Brett C. Sheridan; Fabia Gamboni; Brian S. Cain; Alden H. Harken; Anirban Banerjee

1997-01-01

382

Growth Factor and Receptor Tyrosine Kinases  

NSDL National Science Digital Library

This Teaching Resource provides lecture notes and slides for a graduate-level class on ligand regulation of signaling by receptor tyrosine kinases and receptors involved in the Wnt canonical pathway. It is part of a series of lectures that constitute the Cell Signaling Systems course. A description of the lecture, along with a set of slides used to present this information, is provided.

Stuart Aaronson (Mount Sinai School of Medicine;Department of Oncological Sciences REV)

2005-02-22

383

Tyr728 in the Kinase Domain of the Murine Kinase Suppressor of RAS 1 Regulates Binding and Activation of the Mitogen-activated Protein Kinase Kinase*  

PubMed Central

In metazoans, the highly conserved MAPK signaling pathway regulates cell fate decision. Aberrant activation of this pathway has been implicated in multiple human cancers and some developmental disorders. KSR1 functions as an essential scaffold that binds the individual components of the cascade and coordinates their assembly into multiprotein signaling platforms. The mechanism of KSR1 regulation is highly complex and not completely understood. In this study, we identified Tyr728 as a novel regulatory phosphorylation site in KSR1. We show that Tyr728 is phosphorylated by LCK, uncovering an additional and unexpected link between Src kinases and MAPK signaling. To understand how phosphorylation of Tyr728 may regulate the role of KSR1 in signal transduction, we integrated structural modeling and biochemical studies. We demonstrate that Tyr728 is involved in maintaining the conformation of the KSR1 kinase domain required for binding to MEK. It also affects phosphorylation and activation of MEK by RAF kinases and consequently influences cell proliferation. Moreover, our studies suggest that phosphorylation of Tyr728 may affect the intrinsic kinase activity of KSR1. Together, we propose that phosphorylation of Tyr728 may regulate the transition between the scaffolding and the catalytic function of KSR1 serving as a control point used to fine-tune cellular responses. PMID:24158441

Sibilski, Claudia; Mueller, Thomas; Kollipara, Laxmikanth; Zahedi, René P.; Rapp, Ulf R.; Rudel, Thomas; Baljuls, Angela

2013-01-01

384

Studies and Perspectives of Protein Kinase C  

Microsoft Academic Search

Protein kinase C, an enzyme that is activated by the receptor-mediated hydrolysis of inositol phospholipids, relays information in the form of a variety of extracellular signals across the membrane to regulate many Ca2+-dependent processes. At an early phase of cellular responses, the enzyme appears to have a dual effect, providing positive forward as well as negative feedback controls over various

Yasutomi Nishizuka

1986-01-01

385

Aurora-kinase inhibitors as anticancer agents  

Microsoft Academic Search

Errors in mitosis can provide a source of the genomic instability that is typically associated with tumorigenesis. Many mitotic regulators are aberrantly expressed in tumour cells. These proteins could therefore make useful therapeutic targets. The kinases Aurora-A, -B and -C represent a family of such targets and several small-molecule inhibitors have been shown to block their function. Not only have

Stephen Taylor; Nicholas Keen

2004-01-01

386

IQGAP1 scaffold-kinase interaction blockade selectively targets RAS-MAP kinase–driven tumors  

PubMed Central

Upregulation of the ERK1 and ERK2 (ERK1/2) MAP kinase (MAPK) cascade occurs in >30% of cancers1, often through mutational activation of receptor tyrosine kinases or other upstream genes, including KRAS and BRAF 2. Efforts to target endogenous MAPKs are challenged by the fact that these kinases are required for viability in mammals3,4. Additionally, the effectiveness of new inhibitors of mutant BRAF has been diminished by acquired tumor resistance through selection for BRAF-independent mechanisms of ERK1/2 induction2,5,6. Furthermore, recently identified ERK1/2-inducing mutations in MEK1 and MEK2 (MEK1/2) MAPK genes in melanoma confer resistance to emerging therapeutic MEK inhibitors, underscoring the challenges facing direct kinase inhibition in cancer7,8. MAPK scaffolds, such as IQ motif–containing GTPase activating protein 1 (IQGAP1)9,10, assemble pathway kinases to affect signal transmission11–13, and disrupting scaffold function therefore offers an orthogonal approach to MAPK cascade inhibition. Consistent with this, we found a requirement for IQGAP1 in RAS-driven tumorigenesis in mouse and human tissue. In addition, the ERK1/2-binding14 IQGAP1 WW domain peptide disrupted IQGAP1-ERK1/2 interactions, inhibited RAS- and RAF-driven tumorigenesis, bypassed acquired resistance to the BRAF inhibitor vemurafenib (PLX-4032) and acted as a systemically deliverable therapeutic to significantly increase the lifespan of tumor-bearing mice. Scaffold-kinase interaction blockade acts by a mechanism