Developmental cardiac tissue is regenerative while operating under low oxygen. After birth, ambient oxygen is associated with cardiomyocyte cell cycle exit and regeneration. Likewise, cardiac metabolism undergoes a shift with cardiac maturation. Whether there are common regulators of cardiomyocyte cell cycle linking metabolism to oxygen tension remains unknown. The objective of the study is to determine whether mitochondrial UCP2 is a metabolic oxygen sensor regulating cardiomyocyte cell cycle. Neonatal rat ventricular myocytes (NRVMs) under moderate hypoxia showed increased cell cycle activity and UCP2 expression. NRVMs exhibited a metabolic shift towards glycolysis, reduced citrate synthase, mtDNA, ΔΨm and DNA damage/oxidative stress while loss of UCP2 reversed this phenotype. Next, WT and UCP2KO mice kept under hypoxia for 4 weeks showed significant decline in cardiac function that was more pronounced in UCP2KO animals. Cardiomyocyte cell cycle activity was reduced while fibrosis and DNA damage was significantly increased in UCP2KO animals compared to WT under hypoxia. Mechanistically, UCP2 increased acetyl-CoA levels, histone acetylation and altered chromatin modifiers linking metabolism to cardiomyocyte cell cycle under hypoxia. Here, we show a novel role for mitochondrial UCP2 as an oxygen sensor regulating cardiomyocyte cell cycle activity, acetyl-CoA levels and histone acetylation in response to moderate hypoxia.
Vagner O.C. Rigaud, Clare Zarka, Justin Kurian, Daria Harlamova, Andrea Elia, Nicole Kasatkin, Jaslyn Johnson, Michael Behanan, Lindsay Kraus, Hannah Pepper, Nathaniel W. Snyder, Sadia Mohsin, Steven Houser, Mohsin Khan
Ciliopathies are a class of genetic diseases resulting in cilia dysfunction in multiple organ systems, including the olfactory system. Currently, there are no available curative treatments for olfactory dysfunction and other symptoms in ciliopathies. The loss or shortening of olfactory cilia, as seen in multiple mouse models of the ciliopathy Bardet-Biedl syndrome (BBS), results in olfactory dysfunction. However, the underlying mechanism of the olfactory cilia reduction is unknown, thus limiting the development of therapeutic approaches for BBS and other ciliopathies. Here, we demonstrated that PI(4,5)P2, a phosphoinositide typically excluded from olfactory cilia, aberrantly redistributed into the residual cilia of BBS mouse models, which caused F-actin ciliary infiltration. Importantly, PI(4,5)P2 and F-actin were necessary for olfactory cilia shortening. Using a gene therapeutic approach, the hydrolyzation of PI(4,5)P2 by overexpression of INPP5E restored cilia length, and rescued odor detection and odor perception in BBS. Together, our data indicate that PI(4,5)P2 and F-actin-dependent cilia disassembly is a common mechanism contributing to the loss of olfactory cilia in BBS and provide valuable pan therapeutic intervention targets for the treatment of ciliopathies.
Chao Xie, Julien C. Habif, Kirill Ukhanov, Cedric R. Uytingco, Lian Zhang, Robert J. Campbell, Jeffrey R. Martens
Striated preferentially expressed protein kinase (SPEG), a myosin light chain kinase, is mutated in centronuclear myopathy (CNM) and/or dilated cardiomyopathy. No precise therapies are available against this disorder, and gene replacement therapy is not a feasible option due to the large size of SPEG. We evaluated the potential of dynamin-2 (DNM2) reduction as a potential therapeutic strategy as it has been shown to revert muscle phenotypes in mouse models of CNM caused by MTM1, DNM2, and BIN1 mutations. We determined that SPEGβ interacts with DNM2, and SPEG deficiency causes an increase in DNM2 levels. The DNM2 reduction strategy in Speg-KO mice was associated with an increase in life span, body weight, and motor performance. Additionally, it normalized the distribution of triadic proteins, triad ultrastructure, and triad number, and restored phosphatidylinositol-3-phosphate levels in SPEG-deficient skeletal muscles. While DNM2 reduction rescued the myopathy phenotype, it did not improve cardiac dysfunction, indicating a differential tissue-specific function. Combining DNM2 reduction with other strategies may be needed to target both the cardiac and skeletal defects associated with SPEG deficiency. DNM2 reduction should be explored as a therapeutic strategy against other genetic myopathies (and dystrophies) associated with a high level of DNM2.
Qifei Li, Jasmine Lin, Jeffrey J. Widrick, Shiyu Luo, Gu Li, Yuanfan Zhang, Jocelyn Laporte, Mark A. Perrella, Xiaoli Liu, Pankaj B. Agrawal
Integrins, the principal extracellular matrix (ECM) receptors of the cell, promote cell adhesion, migration, and proliferation, which are key events for cancer growth and metastasis. To date, most integrin-targeted cancer therapeutics have disrupted integrin-ECM interactions, which are viewed as critical for integrin functions. However, such agents have failed to improve cancer patient outcomes. We show that the highly expressed integrin β1 subunit is required for lung adenocarcinoma development in a carcinogen-induced mouse model. Likewise, human lung adenocarcinoma cell lines with integrin β1 deletion failed to form colonies in soft agar and tumors in mice. Mechanistically, we demonstrate that these effects do not require integrin β1-mediated adhesion to ECM but are dependent on integrin β1 cytoplasmic tail-mediated activation of focal adhesion kinase (FAK). Together, these studies support a critical role for integrin β1 in lung tumorigenesis that is mediated through constitutive, ECM-binding independent signaling involving the cytoplasmic tail.
Scott M. Haake, Erin J. Plosa, Jonathan A. Kropski, Lindsay A. Venton, Anupama Reddy, Fabian Bock, Betty T. Chang, Allen J. Luna, Kateryna Nabukhotna, Zhi-Qi Xu, Rebecca A. Prather, Sharon Lee, Harikrishna Tanjore, Vasiliy V. Polosukhin, Olga M. Viquez, Angela Jones, Wentian Luo, Matthew H. Wilson, W. Kimryn Rathmell, Pierre P. Massion, Ambra Pozzi, Timothy S. Blackwell, Roy Zent
Disrupted liver regeneration following hepatectomy represents an “undruggable” clinical challenge associated with poor patient outcomes. Yes-associated protein (YAP), a transcriptional co-activator which is repressed by the Hippo pathway, is instrumental in liver regeneration. We have previously described an alternative, Hippo-independent mechanism of YAP activation mediated by tyrosine-protein phosphatase non-receptor type 11 (SHP2) inhibition. Herein, we examined the effects of YAP activation with a selective SHP1/SHP2 inhibitor, NSC-87877, on liver regeneration in murine partial hepatectomy models. In our studies, NSC-87877 led to accelerated hepatocyte proliferation, improved liver regeneration, and decreased markers of injury following partial hepatectomy. The effects of NSC-87877 were lost in mice with hepatocyte-specific Yap/Taz deletion, which demonstrated dependence on these molecules for the enhanced regenerative response. Furthermore, administration of NSC-87877 to murine models of non-alcoholic steatohepatitis was associated with improved survival and decreased markers of injury post-hepatectomy. Evaluation of transcriptomic changes in the context of NSC-87877 administration revealed reduction in fibrotic signaling and augmentation of cell cycle signaling. Cytoprotective changes included downregulation of Nr4a1, an apoptosis inducer. Collectively, the data suggest that SHP2 inhibition induces a pro-proliferative and cytoprotective enhancement of liver regeneration dependent on YAP.
Ryan D. Watkins, EeeLN H. Buckarma, Jennifer L. Tomlinson, Chantal E. McCabe, Jennifer A. Yonkus, Nathan W. Werneburg, Rachel L. Bayer, Patrick P. Starlinger, Keith D. Robertson, Chen Wang, Gregory J. Gores, Rory L. Smoot
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