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Dae-sik Lim - One of the best experts on this subject based on the ideXlab platform.

  • Thioredoxin-1 functions as a molecular switch regulating the oxidative stress-induced activation of MST1.
    Free radical biology & medicine, 2012
    Co-Authors: Ji Soo Chae, Dae-sik Lim, Sang Gil Hwang, Eui Ju Choi
    Abstract:

    The mammalian STE20-like kinase-1 (MST1), a multifunctional serine-threonine kinase in mammalian cells, has been recently implicated in the mediation of oxidative stress-induced signaling processes that lead to cell death. However, the molecular mechanism by which oxidative stress induces the stimulation of MST1 remains unclear. In this study, we found that thioredoxin-1 was physically associated with MST1 in intact cells and that this interaction was abolished by H2O2. Thioredoxin-1, by binding to the SARAH domain of MST1, inhibited the homodimerization and autophosphorylation of MST1, thereby preventing its activation. Furthermore, TNF-α prevented the physical interaction between thioredoxin-1 and MST1 and promoted the homodimerization and activation of MST1. The effect of TNF-α on MST1 activation was reversed by the reducing agent N-acetyl-l-cysteine. Taken together, our results suggest that thioredoxin-1 functions as a molecular switch to turn off the oxidative stress-induced activation of MST1.

  • MST1 limits the kinase activity of aurora B to promote stable kinetochore-microtubule attachment.
    Current biology : CB, 2010
    Co-Authors: Mi Ju Kim, Su Jung Song, Tackhoon Kim, Dongjun Lee, Seung Hae Kwon, Eui Ju Choi, Dae-sik Lim
    Abstract:

    The establishment and maintenance of proper attachment of kinetochores to microtubules are required to prevent chromosome missegregation and consequent chromosomal instability and tumorigenesis. Although MST1 (mammalian sterile 20-like kinase 1) has been implicated in many aspects of cell cycle regulation and tumor suppression [1], its precise mechanism of action has remained largely unknown. We now show that MST1 promotes accurate kinetochore-microtubule attachment by modulating the kinase activity of Aurora B. HeLa cells depleted of MST1 failed to develop stable end-on kinetochore-microtubule attachment, giving rise to unaligned mitotic chromosomes. The misaligned chromosomes activated the Mad2- and BubR1-dependent spindle checkpoint response, resulting in a delay in anaphase onset. The kinase activity of Aurora B, which promotes destabilization of kinetochore-microtubule attachment [2-4], was increased in cells depleted of MST1 or NDR1, a downstream kinase of MST1. MST1 and NDR1 associated with Aurora B. Moreover, MST1 directly phosphorylated Aurora B and inhibited its kinase activity in vitro. Depletion of Aurora B restored the stability of kinetochore-microtubule attachment in cells depleted of MST1 or NDR1. MST1 is thus a key regulator of Aurora B activity that ensures mitotic chromosome congression and accurate chromosome segregation.

  • Role of the tumor suppressor RASSF2 in regulation of MST1 kinase activity.
    Biochemical and biophysical research communications, 2009
    Co-Authors: Hoogeun Song, Dae-sik Lim
    Abstract:

    The tumor suppressor, RASSF2 (Ras association domain family 2), is frequently downregulated in a number of cancers. Although exogenously expressed RASSF2 induces apoptotic cell death, the precise roles of RASSF2 under pro-apoptotic conditions remain largely unknown. Here, we demonstrate that MST1 (mammalian sterile 20-like kinase 1) regulates RASSF2 protein stability. Knockdown of MST1 in cancer cells markedly destabilizes RASSF2, and MST1-deficient mice show reduced Rassf2 protein levels in several organs. Conversely, RASSF2 activates MST1 kinase activity through formation of a RASSF2-MST1 complex, which inhibits the MST-FOXO3 signaling pathway. RASSF2 also engages the JNK pathway and induces apoptosis in an MST1-independent manner. Collectively, these findings indicate that MST1 is a major determinant of RASSF2 protein stability, and suggest that RASSF2 acts in a complex manner that extends beyond simple protein-protein association to play an important role in MST1 regulation.

  • MST1-FoxO signaling protects Naïve T lymphocytes from cellular oxidative stress in mice.
    PloS one, 2009
    Co-Authors: Juhyun Choi, Dongjun Lee, Jik Young Park, Sean Bong Lee, Dae-sik Lim
    Abstract:

    Background The Ste-20 family kinase Hippo restricts cell proliferation and promotes apoptosis for proper organ development in Drosophila. In C. elegans, Hippo homolog also regulates longevity. The mammalian Ste20-like protein kinase, MST1, plays a role in apoptosis induced by various types of apoptotic stress. MST1 also regulates peripheral naive T cell trafficking and proliferation in mice. However, its functions in mammals are not fully understood. Methodology/Principal Findings Here, we report that the MST1-FoxO signaling pathway plays a crucial role in survival, but not apoptosis, of naive T cells. In MST1−/− mice, peripheral T cells showed impaired FoxO1/3 activation and decreased FoxO protein levels. Consistently, the FoxO targets, Sod2 and catalase, were significantly down-regulated in MST1−/− T cells, thereby resulting in elevated levels of intracellular reactive oxygen species (ROS) and induction of apoptosis. Expression of constitutively active FoxO3a restored MST1−/− T cell survival. Crossing MST1 transgenic mice (MST1 Tg) with MST1−/− mice reduced ROS levels and restored normal numbers of peripheral naive T cells in MST1 Tg;MST1−/− progeny. Interestingly, peripheral T cells from MST1−/− mice were hypersensitive to γ-irradiation and paraquat-induced oxidative stresses, whereas those from MST1 Tg mice were resistant. Conclusions/Significance These data support the hypothesis that tolerance to increased levels of intracellular ROS provided by the MST1-FoxOs signaling pathway is crucial for the maintenance of naive T cell homeostasis in the periphery.

  • Crucial Role for MST1 and Mst2 Kinases in Early Embryonic Development of the Mouse
    Molecular and cellular biology, 2009
    Co-Authors: Dongjun Lee, Tackhoon Kim, Tae Shin Kim, Chae Young Hwang, Young-yun Kong, Ki Sun Kwon, Dae-sik Lim
    Abstract:

    Mammalian sterile 20-like kinases 1 and 2 (MST1 and Mst2, respectively) are potent serine/threonine kinases that are involved in cell proliferation and cell death. To investigate the physiological functions of MST1 and Mst2, we generated MST1 and Mst2 mutant mice. MST1−/− and Mst2−/− mice were viable and fertile and developed normally, suggesting possible functional overlaps between the two genes. A characterization of heterozygous and homozygous combinations of MST1 and Mst2 mutant mice showed that mice containing a single copy of either gene underwent normal organ development; however, MST1−/−; Mst2−/− mice lacking both MST1 and Mst2 genes started dying in utero at approximately embryonic day 8.5. MST1−/−; Mst2−/− mice exhibited severe growth retardation, failed placental development, impaired yolk sac/embryo vascular patterning and primitive hematopoiesis, increased apoptosis in placentas and embryos, and disorganized proliferating cells in the embryo proper. These findings indicate that both MST1 and Mst2 kinases play essential roles in early mouse development, regulating placental development, vascular patterning, primitive hematopoiesis, and cell proliferation and survival.

Tatsuo Kinashi - One of the best experts on this subject based on the ideXlab platform.

  • MST1/2 Balance Immune Activation and Tolerance by Orchestrating Adhesion, Transcription, and Organelle Dynamics in Lymphocytes
    Frontiers in immunology, 2020
    Co-Authors: Yoshihiro Ueda, Naoyuki Kondo, Tatsuo Kinashi
    Abstract:

    The STE20-like serine/threonine kinases MST1 and MST2 (MST1/2) are mammalian homologs of Hippo in flies. MST1/2 regulate organ size by suppressing the transcription factor YAP, which promotes proliferation. MST1 is predominantly expressed in immune cells, where it plays distinct roles. Here, we review the functions of MST1/2 in immune cells, uncovered by a series of recent studies, and discuss the connection between MST1/2 function and immune responses. MST1/2 regulate lymphocyte development, trafficking, survival, and antigen recognition by naive T cells. MST1/2 also regulate the function of regulatory T cells and effector T cell differentiation, thus acting to balance immune activation and tolerance. Interestingly, MST1/2 elicit these functions not by the "canonical" Hippo pathway, but by the non-canonical Hippo pathway or alternative pathways. In these pathways, MST1/2 regulates cellular processes relating to immune response, such as chemotaxis, cell adhesion, immunological synapse, gene transcriptions. Recent advances in our understanding of the molecular mechanisms of these processes have revealed important roles of MST1/2 in regulating cytoskeleton remodeling, integrin activation, and vesicular transport in lymphocytes. We discuss the significance of the MST1/2 signaling in lymphocytes in the regulation of organelle dynamics.

  • Enhanced cytotoxic T-cell function and inhibition of tumor progression by MST1 deficiency.
    FEBS letters, 2016
    Co-Authors: Kaneki Yasuda, Yoshihiro Ueda, Madoka Ozawa, Tadashi Matsuda, Tatsuo Kinashi
    Abstract:

    Mammalian ste-20 like kinase MST1 plays important roles during apoptosis, proliferation, cell polarity, and migration. Here, we report a novel role of MST1 for cytotoxic T-cell responses and tumor suppression. The defect of MST1 caused decreased levels of FoxO, and promoted cytotoxicity in vitro. MST1(-/-) cytotoxic T cells also exhibited enhanced T-bet expression that was associated with elevated expression levels of IFNγ and granzyme B. Moreover, MST1(-/-) cytotoxic T cells suppressed tumor growth in vivo. The data suggest that MST1 inhibits cytotoxicity via T-bet suppression by FoxO1 and FoxO3a. Thus, MST1 is a potential therapeutic target for tumor immunotherapy.

  • Hypermethylation of MST1 in IgG4-related autoimmune pancreatitis and rheumatoid arthritis.
    Biochemical and biophysical research communications, 2015
    Co-Authors: Takataro Fukuhara, Yoshihiro Ueda, Kaneki Yasuda, Takashi Tomiyama, Yoshio Ozaki, Yonsu Son, Shosaku Nomura, Kazushige Uchida, Kazuichi Okazaki, Tatsuo Kinashi
    Abstract:

    The serine/threonine kinase MST1 plays important roles in the control of immune cell trafficking, proliferation, and differentiation. Previously, we reported that MST1 was required for thymocyte selection and regulatory T-cell functions, thereby the prevention of autoimmunity in mice. In humans, MST1 null mutations cause T-cell immunodeficiency and hypergammaglobulinemia with autoantibody production. RASSF5C(RAPL) is an activator of MST1 and it is frequently methylated in some tumors. Herein, we investigated methylation of the promoter regions of MST1 and RASSF5C(RAPL) in leukocytes from patients with IgG4-related autoimmune pancreatitis (AIP) and rheumatoid arthritis (RA). Increased number of CpG methylation in the 5' region of MST1 was detected in AIP patients with extrapancreatic lesions, whereas AIP patients without extrapancreatic lesions were similar to controls. In RA patients, we detected a slight increased CpG methylation in MST1, although the overall number of methylation sites was lower than that of AIP patients with extrapancreatic lesions. There were no significant changes of the methylation levels of the CpG islands in the 5' region of RASSF5C(RAPL) in leukocytes from AIP and RA patients. Consistently, we found a significantly down-regulated expression of MST1 in regulatory T cells of AIP patients. Our results suggest that the decreased expression of MST1 in regulatory T cells due to hypermethylation of the promoter contributes to the pathogenesis of IgG4-related AIP.

  • MST1 controls lymphocyte trafficking and interstitial motility within lymph nodes.
    The EMBO journal, 2009
    Co-Authors: Koko Katagiri, Yoshihiro Ueda, Tomoya Katakai, Yukihiko Ebisuno, Takaharu Okada, Tatsuo Kinashi
    Abstract:

    The regulation of lymphocyte adhesion and migration plays crucial roles in lymphocyte trafficking during immunosurveillance. However, our understanding of the intracellular signalling that regulates these processes is still limited. Here, we show that the Ste20-like kinase MST1 plays crucial roles in lymphocyte trafficking in vivo. MST1−/− lymphocytes exhibited an impairment of firm adhesion to high endothelial venules, resulting in an inefficient homing capacity. In vitro lymphocyte adhesion cascade assays under physiological shear flow revealed that the stopping time of MST1−/− lymphocytes on endothelium was markedly reduced, whereas their L-selectin-dependent rolling/tethering and transition to LFA-1-mediated arrest were not affected. MST1−/− lymphocytes were also defective in the stabilization of adhesion through α4 integrins. Consequently, MST1−/− mice had hypotrophic peripheral lymphoid tissues and reduced marginal zone B cells and dendritic cells in the spleen, and defective emigration of single positive thymocytes. Furthermore, MST1−/− lymphocytes had impaired motility over lymph node-derived stromal cells and within lymph nodes. Thus, our data indicate that MST1 is a key enzyme involved in lymphocyte entry and interstitial migration.

  • Spatiotemporal regulation of the kinase MST1 by binding protein RAPL is critical for lymphocyte polarity and adhesion
    Nature Immunology, 2006
    Co-Authors: Koko Katagiri, Masashi Imamura, Tatsuo Kinashi
    Abstract:

    RAPL, a protein that binds the small GTPase Rap1, is required for efficient immune cell trafficking. Here we have identified the kinase MST1 as a critical effector of RAPL. RAPL regulated the localization and kinase activity of MST1. 'Knockdown' of the gene encoding MST1 demonstrated its requirement for the induction of both a polarized morphology and integrin LFA-1 clustering and adhesion triggered by chemokines and T cell receptor ligation. RAPL and MST1 localized to vesicular compartments and dynamically translocated with LFA-1 to the leading edge upon Rap1 activation, suggesting a regulatory function for the RAPL-MST1 complex in intracellular transport of LFA-1. Our study demonstrates a previously unknown function for MST1 of relaying the Rap1-RAPL signal to induce cell polarity and adhesion of lymphocytes.

Wufan Tao - One of the best experts on this subject based on the ideXlab platform.

  • MST1 positively regulates B-cell receptor signaling via CD19 transcriptional levels.
    Blood advances, 2016
    Co-Authors: Xiaoming Bai, Lu Huang, Xiaoyu Sun, Yongjie Zhang, Jinzhi Wang, Heather Miller, Linlin Niu, Hongyan Jiang, Zhi-yong Zhang, Wufan Tao
    Abstract:

    As a key regulator of hippo signaling pathway, Mst kinases are emerging as one of the key signaling molecules that influence cell proliferation, organ size, cell migration, and cell polarity. In B lymphocytes, MST1 deficiency causes the developmental defect of marginal zone (MZ) B cells, but how MST1 regulates B-cell receptor (BCR) activation and differentiation remains elusive. Using genetically manipulated mouse models and total internal reflection fluorescence microscopy, we have demonstrated that MST1 positively regulates BCR signaling via modulating CD19 transcriptional levels. Consistent with this, MST1-deficient mice exhibited reduced BCR signaling, which is concurrent with defective BCR clustering and B-cell spreading on stimulatory lipid bilayers. The disruption of CD19-mediated Btk signaling by MST1 deficiency leads to the severe defect in the differentiation of MZ and germinal center B cells. Mechanistic analysis showed that MST1 upregulates the messenger RNA level of CD19 via regulating the transcriptional factor TEAD2 that directly binds to the consensus motif in the 3′ untranslated region of cd19 . Overall, our results reveal a new function of MST1 in B cells and the mechanism by which MST1 regulates the activation and differentiation of peripheral B cells.

  • hippo MST1 signaling mediates microglial activation following acute cerebral ischemia reperfusion injury
    Brain Behavior and Immunity, 2016
    Co-Authors: Siqi Zhao, Jie Yin, Lujun Zhou, Feng Yan, Li Huang, Shengyi Peng, Junying Jia, Jinbo Cheng, Hong Chen, Wufan Tao
    Abstract:

    Cerebral ischemia-reperfusion injury is a major public health concern that causes high rates of disability and mortality in adults. Microglial activation plays a crucial role in ischemic stroke-induced alteration of the immune microenvironment. However, the mechanism underlying the triggering of microglial activation by ischemic stroke remains to be elucidated. Previously, we demonstrated that the protein kinase Hippo/MST1 plays an important role in oxidative stress-induced cell death in mammalian primary neurons and that the protein kinase c-Abl phosphorylates MST1 at Y433, which increases MST1 kinase activity. Microglial activation has been implicated as a secondary detrimental cellular response that contributes to neuronal cell death in ischemic stroke. Here, we are the first, to our knowledge, to demonstrate that MST1 mediates stroke-induced microglial activation by directly phosphorylating IκBα at residues S32 and S36. We further demonstrate that Src kinase functions upstream of MST1-IκB signaling during microglial activation. Specific deletion of MST1 in microglia mitigates stroke-induced brain injury. Therefore, we propose that Src-MST1-IκB signaling plays a critical role in stroke-induced microglial activation. Together with our previous work demonstrating that MST1 is important for oxidative stress-induced neuronal cell death, our results indicate that MST1 could represent a potent therapeutic target for ischemic stroke.

  • MST1 regulates hepatic lipid metabolism by inhibiting Sirt1 ubiquitination in mice.
    Biochemical and biophysical research communications, 2016
    Co-Authors: Chao Geng, Yinliang Zhang, Yong Gao, Wufan Tao, Huabing Zhang, Xiaojun Liu, Fude Fang, Yongsheng Chang
    Abstract:

    Previous study showed mammalian Ste20-like kinase (MST1) may serve as target for the development of new therapies for diabetes. However, the function of MST1 involved in liver lipid metabolism has remained elusive. In this study, we report that the liver of MST1 knockout (MST1(-/-)) mice showed more severe liver metabolic damage under fasting and high-fat diet than that of control mice. And fasting induced hepatic MST1 expression. MST1 overexpression inhibited Srebp-1c expression and increased the expression of antioxidant genes in primary hepatocytes. We also found that fasting-induced expression of hepatic Sirt1 was attenuated in MST1(-/-) mice. MST1 overexpression promoted Sirt1 expression, probably due to inhibiting Sirt1 ubiquitination. In summary, our study suggests that MST1 regulates hepatic lipid metabolism by inhibiting Sirt1 ubiquitination in mice.

  • MST1 and Mst2 Are Essential Regulators of Trophoblast Differentiation and Placenta Morphogenesis
    PloS one, 2014
    Co-Authors: Yongli Dong, Hao Shi, Shanshan Kong, Donghua Shi, Ling V. Sun, Kejing Deng, Wufan Tao
    Abstract:

    The placenta is essential for survival and growth of the fetus because it promotes the delivery of nutrients and oxygen from the maternal circulation as well as fetal waste disposal. MST1 and Mst2 (MST1/2), key components of the mammalian hpo/Mst signaling pathway, encode two highly conserved Ser/Thr kinases and play important roles in the prevention of tumorigenesis and autoimmunity, control of T cell development and trafficking, and embryonic development. However, their functions in placental development are not fully understood, and the underlying cellular and molecular mechanisms remain elusive. Here, we investigated the functions of MST1/2 in mouse placental development using both conventional and conditional (endothelial) MST1/2 double knockout mice. We found that the number of trophoblast giant cells dramatically increased while spongiotrophoblast cells almost completely disappeared in MST1/2 deficient placentas. We showed that MST1/2 deficiency down regulated the expression of Mash2, which is required for suppressing the differentiation of trophoblast giant cells. Furthermore, we demonstrated that endothelial-specific deletion of MST1/2 led to impaired placental labyrinthine vasculature and embryonic lethality at E11.5, but neither affected vasculature in yolk sac and embryo proper nor endocardium development. Collectively, our findings suggest that MST1/2 regulate placental development by control of trophoblast cell differentiation and labyrinthine vasculature at midgestation and MST1/2 control labyrinth morphogenesis in trophoblast- and fetal endothelial-dependent manners. Thus, our studies have defined novel roles of MST1/2 in mouse placental development.

  • MST1 Promotes Apoptosis through Regulating Sirt1-dependent p53 Deacetylation
    The Journal of biological chemistry, 2011
    Co-Authors: Fang Yuan, Yongli Dong, Wufan Tao, Qi Xie, Yujie Bai, Beibei Mao, Yan Wang
    Abstract:

    Mammalian Sterile 20-like kinase 1 (MST1) protein kinase plays an important role in the apoptosis induced by a variety of stresses. The MST1 is a serine/threonine kinase that is activated upon apoptotic stimulation, which in turn activates its downstream targets, JNK/p38, histone H2B and FOXO. It has been reported that overexpression of MST1 initiates apoptosis by activating p53. However, the molecular mechanisms underlying MST1-p53 signaling during apoptosis are unclear. Here, we report that MST1 promotes genotoxic agent-induced apoptosis in a p53-dependent manner. We found that MST1 increases p53 acetylation and transactivation by inhibiting the deacetylation of Sirtuin 1 (Sirt1) and its interaction with p53 and that Sirt1 can be phosphorylated by MST1 leading to the inhibition of Sirt1 activity. Collectively, these findings define a novel regulatory mechanism involving the phosphorylation of Sirt1 by MST1 kinase which leads to p53 activation, with implications for our understanding of signaling mechanisms during DNA damage-induced apoptosis.

Maria Praskova - One of the best experts on this subject based on the ideXlab platform.

  • the nore1b MST1 complex restrains antigen receptor induced proliferation of naive t cells
    Proceedings of the National Academy of Sciences of the United States of America, 2008
    Co-Authors: Dawang Zhou, Maria Praskova, Benjamin D. Medoff, Lanfen Chen, Xian-feng Zhang, Matthew Liu, Aimee Landry, Richard S. Blumberg, Vassiliki A. Boussiotis, Ramnik J Xavier
    Abstract:

    The MST1 and Mst2 protein kinases are the mammalian homologs of hippo, a major inhibitor of cell proliferation in Drosophila. MST1 is most abundant in lymphoid tissues. Mice lacking MST1 exhibit markedly reduced levels of the MST1 regulatory protein Nore1B/RAPL in lymphoid cells, whereas Mst2 abundance is unaltered. MST1-null mice exhibit normal T cell development but low numbers of mature naive T cells with relatively normal numbers of effector/memory T cells. In vitro, the MST1-deficient naive T cells exhibit markedly greater proliferation in response to stimulation of the T cell receptor whereas the proliferative responses of the MST1-null effector/memory T cell cohort is similar to wild type. Thus, elimination of MST1 removes a barrier to the activation and proliferative response of naive T cells. The levels of MST1 and Nore1B/RAPL in wild-type effector/memory T cells are approximately 10% those seen in wild-type naive T cells, which may contribute to the enhanced proliferative responses of the former. Freshly isolated MST1-null T cells exhibit high rates of ongoing apoptosis, a likely basis for their low numbers in vivo; they also exhibit defective clustering of LFA-1, as previously observed for Nore1B/RAPL-deficient T cells. Among known MST1 substrates, only the phosphorylation of the cell cycle inhibitory proteins MOBKL1A/B is lost entirely in TCR-stimulated, MST1-deficient T cells. MST1/2-catalyzed MOBKL1A/B phosphorylation slows proliferation and is therefore a likely contributor to the anti-proliferative action of MST1 in naive T cells. The Nore1B/RAPL-MST1 complex is a negative regulator of naive T cell proliferation.

  • The Nore1B/MST1 complex restrains antigen receptor-induced proliferation of naïve T cells
    Proceedings of the National Academy of Sciences of the United States of America, 2008
    Co-Authors: Dawang Zhou, Maria Praskova, Benjamin D. Medoff, Lanfen Chen, Xian-feng Zhang, Matthew Liu, Aimee Landry, Richard S. Blumberg, Vassiliki A. Boussiotis
    Abstract:

    The MST1 and Mst2 protein kinases are the mammalian homologs of hippo, a major inhibitor of cell proliferation in Drosophila. MST1 is most abundant in lymphoid tissues. Mice lacking MST1 exhibit markedly reduced levels of the MST1 regulatory protein Nore1B/RAPL in lymphoid cells, whereas Mst2 abundance is unaltered. MST1-null mice exhibit normal T cell development but low numbers of mature naive T cells with relatively normal numbers of effector/memory T cells. In vitro, the MST1-deficient naive T cells exhibit markedly greater proliferation in response to stimulation of the T cell receptor whereas the proliferative responses of the MST1-null effector/memory T cell cohort is similar to wild type. Thus, elimination of MST1 removes a barrier to the activation and proliferative response of naive T cells. The levels of MST1 and Nore1B/RAPL in wild-type effector/memory T cells are approximately 10% those seen in wild-type naive T cells, which may contribute to the enhanced proliferative responses of the former. Freshly isolated MST1-null T cells exhibit high rates of ongoing apoptosis, a likely basis for their low numbers in vivo; they also exhibit defective clustering of LFA-1, as previously observed for Nore1B/RAPL-deficient T cells. Among known MST1 substrates, only the phosphorylation of the cell cycle inhibitory proteins MOBKL1A/B is lost entirely in TCR-stimulated, MST1-deficient T cells. MST1/2-catalyzed MOBKL1A/B phosphorylation slows proliferation and is therefore a likely contributor to the anti-proliferative action of MST1 in naive T cells. The Nore1B/RAPL-MST1 complex is a negative regulator of naive T cell proliferation.

  • MOBKL1A/MOBKL1B Phosphorylation by MST1 and MST2 Inhibits Cell Proliferation
    Current biology : CB, 2008
    Co-Authors: Maria Praskova, Fan Xia, Joseph Avruch
    Abstract:

    Summary Background MST1 and MST2 are the mammalian Ste20-related protein kinases most closely related to Drosophila Hippo, a major regulator of cell proliferation and survival during development. Overexpression of MST1 or MST2 in mammalian cells is proapototic; however, little is known concerning the physiologic regulation of the endogenous MST1/MST2 kinases, their role in mammalian cell proliferation, or the identity of the MST1/MST2 substrates critical to proliferative regulation. Results We show that MST1 and MST2 activity increases during mitosis, especially in nocodazole-arrested mitotic cells, where these kinases exhibit both an increase in both abundance and activation. MST1 and MST2 also can be activated nonphysiologically by okadaic acid or H 2 O 2 . The MOBKL1A and MOBKL1B polypeptides, homologs of the Drosophila MATS polypeptide, are identified as preferred MST1/MST2 substrates in vitro and are phosphorylated in cells in an MST1/MST2-dependent manner in mitosis and in response to okadaic acid or H 2 O 2 . MST1/MST2-catalyzed MOBKL1A/MOBKL1B phosphorylation alters the ability of MOBKL1A/MOBKL1B to bind and regulate downstream targets such as the NDR-family protein kinases. Thus, MOBKL1A/MOBKL1B phosphorylation in cells promotes MOBKL1A/MOBKL1B binding to the LATS1 kinase and enables H 2 O 2 -stimulated LATS1 activation loop phosphorylation. Most importantly, replacement of endogenous MOBKL1A/MOBKL1B by a nonphosphorylatable mutant is sufficient to accelerate cell proliferation substantially by speeding progression through G1/S as well as mitotic exit. Conclusions These results establish that MST1 and MST2 are activated in mitosis and catalyze the mitotic phosphorylation of MOBKL1A/MOBKL1B. MOBKL1A/MOBKL1B phosphorylation, in turn, is sufficient to inhibit proliferation through actions at several points in the cell cycle.

  • mobkl1a mobkl1b phosphorylation by MST1 and mst2 inhibits cell proliferation
    Current Biology, 2008
    Co-Authors: Maria Praskova, Fan Xia, Joseph Avruch
    Abstract:

    Summary Background MST1 and MST2 are the mammalian Ste20-related protein kinases most closely related to Drosophila Hippo, a major regulator of cell proliferation and survival during development. Overexpression of MST1 or MST2 in mammalian cells is proapototic; however, little is known concerning the physiologic regulation of the endogenous MST1/MST2 kinases, their role in mammalian cell proliferation, or the identity of the MST1/MST2 substrates critical to proliferative regulation. Results We show that MST1 and MST2 activity increases during mitosis, especially in nocodazole-arrested mitotic cells, where these kinases exhibit both an increase in both abundance and activation. MST1 and MST2 also can be activated nonphysiologically by okadaic acid or H 2 O 2 . The MOBKL1A and MOBKL1B polypeptides, homologs of the Drosophila MATS polypeptide, are identified as preferred MST1/MST2 substrates in vitro and are phosphorylated in cells in an MST1/MST2-dependent manner in mitosis and in response to okadaic acid or H 2 O 2 . MST1/MST2-catalyzed MOBKL1A/MOBKL1B phosphorylation alters the ability of MOBKL1A/MOBKL1B to bind and regulate downstream targets such as the NDR-family protein kinases. Thus, MOBKL1A/MOBKL1B phosphorylation in cells promotes MOBKL1A/MOBKL1B binding to the LATS1 kinase and enables H 2 O 2 -stimulated LATS1 activation loop phosphorylation. Most importantly, replacement of endogenous MOBKL1A/MOBKL1B by a nonphosphorylatable mutant is sufficient to accelerate cell proliferation substantially by speeding progression through G1/S as well as mitotic exit. Conclusions These results establish that MST1 and MST2 are activated in mitosis and catalyze the mitotic phosphorylation of MOBKL1A/MOBKL1B. MOBKL1A/MOBKL1B phosphorylation, in turn, is sufficient to inhibit proliferation through actions at several points in the cell cycle.

  • Regulation of the MST1 kinase by autophosphorylation, by the growth inhibitory proteins, RASSF1 and NORE1, and by Ras.
    The Biochemical journal, 2004
    Co-Authors: Maria Praskova, Sara Ortiz-vega, Andrei Khoklatchev, Joseph Avruch
    Abstract:

    MST1 (mammalian Sterile20-like 1) and MST2 are closely related Class II GC (protein Ser/Thr) kinases that initiate apoptosis when transiently overexpressed in mammalian cells. In the present study, we show that recombinant MST1/2 undergo a robust autoactivation in vitro, mediated by an intramolecular autophosphorylation of a single site [MST1(Thr183)/MST2(Thr180)] on the activation loop of an MST dimer. Endogenous full-length MST1 is activated by a variety of stressful stimuli, accompanied by the secondary appearance of a 36 kDa Thr183-phosphorylated, caspase-cleaved catalytic fragment. Recombinant MST1 exhibits only 2-5% activation during transient expression; endogenous MST1 in the cycling HeLa or KB cells has a similar low fractional activation, but 2 h incubation with okadaic acid (1 mM) results in 100% activation. Endogenous MST1 immunoprecipitated from KB cells is specifically associated with substoichiometric amounts of the growth inhibitory polypeptides RASSF1A and NORE1A (novel Ras effector 1A; a Ras-GTP-binding protein). Co-expression of RASSF1A, RASSF1C, NORE1A and NORE1B with MST1 markedly suppresses MST1(Thr183) phosphorylation in vivo and abolishes the ability of MST1 to undergo Mg-ATP-mediated autoactivation in vitro; direct addition of purified NORE1A in vitro also inhibits MST1 activation. In contrast, co-transfection of MST1 with NORE1A modified by the addition of a C-terminal CAAX motif results in a substantial increase in MST1(Thr183) phosphorylation, as does fusion of a myristoylation motif directly on to the MST1 N-terminus. Moreover, MST1 polypeptides, bound via wild-type NORE1A to Ras(G12V) (where G12V stands for Gly12Val), exhibit higher Thr183 phosphorylation compared with MST1 bound to NORE1A alone. Nevertheless, serum stimulation of KB cells does not detectably increase the activation state of endogenous MST1 or MST2 despite promoting the recruitment of the endogenous NORE1-MST1 complex to endogenous Ras. We propose that the NORE1/RASSF1 polypeptides, in addition to their role in maintaining the low activity of MST1 in vivo, direct MST1 to sites of activation and perhaps co-localization with endogenous substrates.

Joseph Avruch - One of the best experts on this subject based on the ideXlab platform.

  • MST1 and mst2 maintain hepatocyte quiescence and suppress hepatocellular carcinoma development through inactivation of the yap1 oncogene
    Cancer Cell, 2009
    Co-Authors: Dawang Zhou, Claudius Conrad, Fan Xia, Ji Sun Park, Bernhard Payer, Yi Yin, Gregory Y Lauwers, Wolfgang Thasler, Jeannie T Lee, Joseph Avruch
    Abstract:

    Hippo-Lats-Yorkie signaling regulates tissue overgrowth and tumorigenesis in Drosophila. We show that the MST1 and Mst2 protein kinases, the mammalian Hippo orthologs, are cleaved and constitutively activated in the mouse liver. Combined MST1/2 deficiency in the liver results in loss of inhibitory Ser127 phosphorylation of the Yorkie ortholog, Yap1, massive overgrowth, and hepatocellular carcinoma (HCC). Reexpression of MST1 in HCC-derived cell lines promotes Yap1 Ser127 phosphorylation and inactivation and abrogates their tumorigenicity. Notably, MST1/2 inactivates Yap1 in liver through an intermediary kinase distinct from Lats1/2. Approximately 30% of human HCCs show low Yap1(Ser127) phosphorylation and a majority exhibit loss of cleaved, activated MST1. MST1/2 inhibition of Yap1 is an important pathway for tumor suppression in liver relevant to human HCC.

  • MOBKL1A/MOBKL1B Phosphorylation by MST1 and MST2 Inhibits Cell Proliferation
    Current biology : CB, 2008
    Co-Authors: Maria Praskova, Fan Xia, Joseph Avruch
    Abstract:

    Summary Background MST1 and MST2 are the mammalian Ste20-related protein kinases most closely related to Drosophila Hippo, a major regulator of cell proliferation and survival during development. Overexpression of MST1 or MST2 in mammalian cells is proapototic; however, little is known concerning the physiologic regulation of the endogenous MST1/MST2 kinases, their role in mammalian cell proliferation, or the identity of the MST1/MST2 substrates critical to proliferative regulation. Results We show that MST1 and MST2 activity increases during mitosis, especially in nocodazole-arrested mitotic cells, where these kinases exhibit both an increase in both abundance and activation. MST1 and MST2 also can be activated nonphysiologically by okadaic acid or H 2 O 2 . The MOBKL1A and MOBKL1B polypeptides, homologs of the Drosophila MATS polypeptide, are identified as preferred MST1/MST2 substrates in vitro and are phosphorylated in cells in an MST1/MST2-dependent manner in mitosis and in response to okadaic acid or H 2 O 2 . MST1/MST2-catalyzed MOBKL1A/MOBKL1B phosphorylation alters the ability of MOBKL1A/MOBKL1B to bind and regulate downstream targets such as the NDR-family protein kinases. Thus, MOBKL1A/MOBKL1B phosphorylation in cells promotes MOBKL1A/MOBKL1B binding to the LATS1 kinase and enables H 2 O 2 -stimulated LATS1 activation loop phosphorylation. Most importantly, replacement of endogenous MOBKL1A/MOBKL1B by a nonphosphorylatable mutant is sufficient to accelerate cell proliferation substantially by speeding progression through G1/S as well as mitotic exit. Conclusions These results establish that MST1 and MST2 are activated in mitosis and catalyze the mitotic phosphorylation of MOBKL1A/MOBKL1B. MOBKL1A/MOBKL1B phosphorylation, in turn, is sufficient to inhibit proliferation through actions at several points in the cell cycle.

  • mobkl1a mobkl1b phosphorylation by MST1 and mst2 inhibits cell proliferation
    Current Biology, 2008
    Co-Authors: Maria Praskova, Fan Xia, Joseph Avruch
    Abstract:

    Summary Background MST1 and MST2 are the mammalian Ste20-related protein kinases most closely related to Drosophila Hippo, a major regulator of cell proliferation and survival during development. Overexpression of MST1 or MST2 in mammalian cells is proapototic; however, little is known concerning the physiologic regulation of the endogenous MST1/MST2 kinases, their role in mammalian cell proliferation, or the identity of the MST1/MST2 substrates critical to proliferative regulation. Results We show that MST1 and MST2 activity increases during mitosis, especially in nocodazole-arrested mitotic cells, where these kinases exhibit both an increase in both abundance and activation. MST1 and MST2 also can be activated nonphysiologically by okadaic acid or H 2 O 2 . The MOBKL1A and MOBKL1B polypeptides, homologs of the Drosophila MATS polypeptide, are identified as preferred MST1/MST2 substrates in vitro and are phosphorylated in cells in an MST1/MST2-dependent manner in mitosis and in response to okadaic acid or H 2 O 2 . MST1/MST2-catalyzed MOBKL1A/MOBKL1B phosphorylation alters the ability of MOBKL1A/MOBKL1B to bind and regulate downstream targets such as the NDR-family protein kinases. Thus, MOBKL1A/MOBKL1B phosphorylation in cells promotes MOBKL1A/MOBKL1B binding to the LATS1 kinase and enables H 2 O 2 -stimulated LATS1 activation loop phosphorylation. Most importantly, replacement of endogenous MOBKL1A/MOBKL1B by a nonphosphorylatable mutant is sufficient to accelerate cell proliferation substantially by speeding progression through G1/S as well as mitotic exit. Conclusions These results establish that MST1 and MST2 are activated in mitosis and catalyze the mitotic phosphorylation of MOBKL1A/MOBKL1B. MOBKL1A/MOBKL1B phosphorylation, in turn, is sufficient to inhibit proliferation through actions at several points in the cell cycle.

  • Regulation of the MST1 kinase by autophosphorylation, by the growth inhibitory proteins, RASSF1 and NORE1, and by Ras.
    The Biochemical journal, 2004
    Co-Authors: Maria Praskova, Sara Ortiz-vega, Andrei Khoklatchev, Joseph Avruch
    Abstract:

    MST1 (mammalian Sterile20-like 1) and MST2 are closely related Class II GC (protein Ser/Thr) kinases that initiate apoptosis when transiently overexpressed in mammalian cells. In the present study, we show that recombinant MST1/2 undergo a robust autoactivation in vitro, mediated by an intramolecular autophosphorylation of a single site [MST1(Thr183)/MST2(Thr180)] on the activation loop of an MST dimer. Endogenous full-length MST1 is activated by a variety of stressful stimuli, accompanied by the secondary appearance of a 36 kDa Thr183-phosphorylated, caspase-cleaved catalytic fragment. Recombinant MST1 exhibits only 2-5% activation during transient expression; endogenous MST1 in the cycling HeLa or KB cells has a similar low fractional activation, but 2 h incubation with okadaic acid (1 mM) results in 100% activation. Endogenous MST1 immunoprecipitated from KB cells is specifically associated with substoichiometric amounts of the growth inhibitory polypeptides RASSF1A and NORE1A (novel Ras effector 1A; a Ras-GTP-binding protein). Co-expression of RASSF1A, RASSF1C, NORE1A and NORE1B with MST1 markedly suppresses MST1(Thr183) phosphorylation in vivo and abolishes the ability of MST1 to undergo Mg-ATP-mediated autoactivation in vitro; direct addition of purified NORE1A in vitro also inhibits MST1 activation. In contrast, co-transfection of MST1 with NORE1A modified by the addition of a C-terminal CAAX motif results in a substantial increase in MST1(Thr183) phosphorylation, as does fusion of a myristoylation motif directly on to the MST1 N-terminus. Moreover, MST1 polypeptides, bound via wild-type NORE1A to Ras(G12V) (where G12V stands for Gly12Val), exhibit higher Thr183 phosphorylation compared with MST1 bound to NORE1A alone. Nevertheless, serum stimulation of KB cells does not detectably increase the activation state of endogenous MST1 or MST2 despite promoting the recruitment of the endogenous NORE1-MST1 complex to endogenous Ras. We propose that the NORE1/RASSF1 polypeptides, in addition to their role in maintaining the low activity of MST1 in vivo, direct MST1 to sites of activation and perhaps co-localization with endogenous substrates.

  • Death-associated protein 4 binds MST1 and augments MST1-induced apoptosis.
    The Journal of biological chemistry, 2002
    Co-Authors: Yenshou Lin, Andrei Khokhlatchev, Daniel Figeys, Joseph Avruch
    Abstract:

    Abstract The protein kinase MST1 is proapoptotic when overexpressed in an active form, however, its physiologic regulation and cellular targets are unknown. An overexpressed inactive MST1 mutant associates in COS-7 cells with an endogenous 761-amino acid polypeptide known as “death-associated protein 4” (DAP4). The DAPs are a functionally heterogeneous array of polypeptides previously isolated by Kimchi and colleagues (Kimchi, A. (1998) Biochim. Biophys. Acta 1377, F13–F33 in a screen for elements involved in the interferon γ-induced apoptosis of HeLa cells. DAP4, which is encoded by a member of a vertebrate-only gene family, contains no identifiable domains, but is identical over its amino-terminal 488 amino acids to p52rIPK, a putative modulator of protein kinase R. DAP4 is a widely expressed, constitutively nuclear polypeptide that homodimerizes through its amino terminus and binds MST1 through its carboxyl-terminal segment. MST1 is predominantly cytoplasmic, but cycles continuously through the nucleus, as evidenced by its rapid accumulation in the nucleus after addition of the Crm1 inhibitor, leptomycin B. Overexpression of DAP4 does not cause apoptosis, however, coexpression of DAP4 with a submaximal amount of MST1 enhances MST1-induced apoptosis in a dose-dependent fashion. DAP4 is not significantly phosphorylated by MST1 nor does it alter MST1 kinase activity in vivo or in vitro. MST1-induced apoptosis is suppressed by a dominant interfering mutant of p53. MST1 is unable to directly phosphorylate p53, however, DAP4 binds endogenous and recombinant p53. DAP4 may promote MST1-induced apoptosis by enabling colocalization of MST with p53.