Salah Aburahess, Laiji Li, Aashiq Hussain, Marya Obeidat, Parnian Alavi, Abul K Azad, Nadia Jahroudi, Barbara J Ballermann
{"title":"Hypoxia-induced TIMAP upregulation in endothelial cells and TIMAP-dependent tumor angiogenesis.","authors":"Salah Aburahess, Laiji Li, Aashiq Hussain, Marya Obeidat, Parnian Alavi, Abul K Azad, Nadia Jahroudi, Barbara J Ballermann","doi":"10.1152/ajpcell.00054.2024","DOIUrl":null,"url":null,"abstract":"<p><p>TGFβ-inhibited membrane associated protein (TIMAP), the endothelial cell-predominant protein phosphatase 1β regulatory subunit also known as PPP1R16B, promotes in vitro endothelial cell proliferation and angiogenic sprouting. TIMAP was first identified as a target of TGF-β1-mediated repression, but the molecular pathways regulating its expression in endothelial cells are not well-defined. This study examined the role of bone morphogenetic factor 9 (BMP9), hypoxia, and angiogenic growth factors in the regulation of TIMAP expression and determined whether TIMAP plays a role in tumor angiogenesis and growth in vivo. BMP9, which potently activated the SMAD1/5/8 pathway in endothelial cells, significantly reduced TIMAP mRNA and protein expression. Conversely, hypoxia and the prolyl hydroxylase inhibitor Roxadustat raised TIMAP mRNA and protein levels by inhibiting the SMAD1/5/8 pathway. Angiogenic growth factors, including VEGFA and IGF-I, raised endothelial TIMAP levels partly by attenuating SMAD1/5/8 pathway activation, but also through SMAD1/5/8-independent mechanisms. Cultured breast cancer E0771 cells released mediators that raised TIMAP expression in endothelial cells, effects that were inhibited by the VEGF inhibitor Sunitinib in conjunction with the IGF-1 inhibitor Picropodophyllin. In the mouse E0771 breast cancer model in vivo, tumor growth and tumor angiogenesis were markedly attenuated in TIMAP deficient, compared with wild-type littermates. These findings indicate that TIMAP plays a critical proangiogenic function during tumor angiogenesis in vivo, likely through hypoxia-driven inhibition of the SMAD1/5/8 pathway and through the elaboration of angiogenic growth factors by tumor cells.<b>NEW & NOTEWORTHY</b> The protein phosphatase 1 regulatory subunit TGFβ-inhibited membrane associated protein (TIMAP), known to activate AKT in endothelial cells (EC), was shown here to be repressed by bone morphogenetic factor 9 (BMP9). Hypoxia and angiogenic growth factors induced TIMAP expression by inhibiting the BMP9 pathway. In a mouse breast cancer model, TIMAP deletion inhibited tumor angiogenesis and tumor growth. Therefore, the proangiogenic functions of TIMAP are induced by hypoxia and angiogenic growth factors.</p>","PeriodicalId":7585,"journal":{"name":"American journal of physiology. Cell physiology","volume":null,"pages":null},"PeriodicalIF":5.0000,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"American journal of physiology. Cell physiology","FirstCategoryId":"99","ListUrlMain":"https://doi.org/10.1152/ajpcell.00054.2024","RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"2024/9/30 0:00:00","PubModel":"Epub","JCR":"Q2","JCRName":"CELL BIOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
TGFβ-inhibited membrane associated protein (TIMAP), the endothelial cell-predominant protein phosphatase 1β regulatory subunit also known as PPP1R16B, promotes in vitro endothelial cell proliferation and angiogenic sprouting. TIMAP was first identified as a target of TGF-β1-mediated repression, but the molecular pathways regulating its expression in endothelial cells are not well-defined. This study examined the role of bone morphogenetic factor 9 (BMP9), hypoxia, and angiogenic growth factors in the regulation of TIMAP expression and determined whether TIMAP plays a role in tumor angiogenesis and growth in vivo. BMP9, which potently activated the SMAD1/5/8 pathway in endothelial cells, significantly reduced TIMAP mRNA and protein expression. Conversely, hypoxia and the prolyl hydroxylase inhibitor Roxadustat raised TIMAP mRNA and protein levels by inhibiting the SMAD1/5/8 pathway. Angiogenic growth factors, including VEGFA and IGF-I, raised endothelial TIMAP levels partly by attenuating SMAD1/5/8 pathway activation, but also through SMAD1/5/8-independent mechanisms. Cultured breast cancer E0771 cells released mediators that raised TIMAP expression in endothelial cells, effects that were inhibited by the VEGF inhibitor Sunitinib in conjunction with the IGF-1 inhibitor Picropodophyllin. In the mouse E0771 breast cancer model in vivo, tumor growth and tumor angiogenesis were markedly attenuated in TIMAP deficient, compared with wild-type littermates. These findings indicate that TIMAP plays a critical proangiogenic function during tumor angiogenesis in vivo, likely through hypoxia-driven inhibition of the SMAD1/5/8 pathway and through the elaboration of angiogenic growth factors by tumor cells.NEW & NOTEWORTHY The protein phosphatase 1 regulatory subunit TGFβ-inhibited membrane associated protein (TIMAP), known to activate AKT in endothelial cells (EC), was shown here to be repressed by bone morphogenetic factor 9 (BMP9). Hypoxia and angiogenic growth factors induced TIMAP expression by inhibiting the BMP9 pathway. In a mouse breast cancer model, TIMAP deletion inhibited tumor angiogenesis and tumor growth. Therefore, the proangiogenic functions of TIMAP are induced by hypoxia and angiogenic growth factors.
期刊介绍:
The American Journal of Physiology-Cell Physiology is dedicated to innovative approaches to the study of cell and molecular physiology. Contributions that use cellular and molecular approaches to shed light on mechanisms of physiological control at higher levels of organization also appear regularly. Manuscripts dealing with the structure and function of cell membranes, contractile systems, cellular organelles, and membrane channels, transporters, and pumps are encouraged. Studies dealing with integrated regulation of cellular function, including mechanisms of signal transduction, development, gene expression, cell-to-cell interactions, and the cell physiology of pathophysiological states, are also eagerly sought. Interdisciplinary studies that apply the approaches of biochemistry, biophysics, molecular biology, morphology, and immunology to the determination of new principles in cell physiology are especially welcome.