Browsing by Subject "YAP1"

Now showing 1 - 3 of 3
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    Maternal hepatocytes heterogeneously and dynamically exhibit developmental phenotypes partially via yes-associated protein 1 during pregnancy
    (American Physiological Society, 2023) Nambiar, Shashank Manohar; Lee, Joonyong; Yanum, Jennifer Abla; Garcia, Veronica; Jiang, Huaizhou; Dai, Guoli; Biology, School of Science
    Pregnancy induces reprogramming of maternal physiology to support fetal development and growth. Maternal hepatocytes undergo hypertrophy and hyperplasia to drive maternal liver growth and alter their gene expression profiles simultaneously. This study aimed to further understand maternal hepatocyte adaptation to pregnancy. Timed pregnancies were generated in mice. In a nonpregnant state, most hepatocytes expressed Cd133, α-fetal protein (Afp) and epithelial cell adhesion molecule (Epcam) mRNAs, whereas overall, at the protein level, they exhibited a CD133-/AFP- phenotype; however, pericentral hepatocytes were EpCAM+. As pregnancy advanced, although most maternal hepatocytes retained Cd133, Afp, and Epcam mRNA expression, they generally displayed a phenotype of CD133+/AFP+, and EpCAM protein expression was switched from pericentral to periportal maternal hepatocytes. In addition, we found that the Hippo/yes-associated protein (YAP) pathway does not respond to pregnancy. Yap1 gene deletion specifically in maternal hepatocytes did not affect maternal liver growth or metabolic zonation. However, the absence of Yap1 gene eliminated CD133 protein expression without interfering with Cd133 transcript expression in maternal livers. We demonstrated that maternal hepatocytes acquire heterogeneous and dynamic developmental phenotypes, resembling fetal hepatocytes, partially via YAP1 through a posttranscriptional mechanism. Moreover, maternal liver is a new source of AFP. In addition, maternal liver grows and maintains its metabolic zonation independent of the Hippo/YAP1 pathway. Our findings revealed a novel and gestation-dependent phenotypic plasticity in adult hepatocytes. NEW & NOTEWORTHY: We found that maternal hepatocytes exhibit developmental phenotypes in a temporal and spatial manner, similarly to fetal hepatocytes. They acquire this new property partially via yes-associated protein 1.
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    Molecular mechanisms of acquired gemcitabine resistance in pancreatic cancer
    (2014-11) Qin, Li; Zhang, Jian-Ting
    Most pancreatic cancer patients receiving gemcitabine chemotherapy eventually develop resistance to gemcitabine. To improve survival and prognosis of pancreatic cancer patients, better understanding the mechanisms of gemcitabine resistance and discovery of new therapeutic targets are required. In this study, I investigated the molecular mechanisms of acquired gemcitabine resistance using a stepwise gemcitabine-selected pancreatic cancer cell line in comparison to the parental cell line. I found that 14-3-3σ is up-regulated in the drug resistant cell line due to demethylation in its first exon, and the up-regulation of 14-3-3σ gene expression, in turn, contributes to gemcitabine resistance. Intriguingly, I found that demethylation of the 14-3-3σ gene in gemcitabine resistant cells is reversibly regulated by DNMT1 and UHRF1. Furthermore, I found that 14-3-3σ over-expression causes gemcitabine resistance by inhibiting gemcitabine-induced apoptosis and caspase-8 activation possibly via binding to YAP1. The finding of demethylation of the 14-3-3σ gene in gemcitabine resistant cells led to a hypothesis that other genes may also be changed epigenetically following gemcitabine selection. By RRBS (Reduced Representation Bisulfite Sequencing) analysis, 845 genes were found to have altered methylation. One of these genes, PDGFD, was further investigated and found to have reversible demethylation at its promoter region in the drug resistant cells and contribute to gemcitabine resistance possibly via autocrine activation of the STAT3 signaling pathway. Together, these findings not only provide evidence that 14-3-3σ and PDGFD over-expression contribute to acquired gemcitabine resistance and that reversible epigenetic changes may play an important role in acquired gemcitabine resistance, but also demonstrate that the molecular mechanisms of acquired gemcitabine resistance in pancreatic cancer cells are complex and multifaceted.
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    Sphingosine Kinase 1 Deficiency in Smooth Muscle Cells Protects against Hypoxia-Mediated Pulmonary Hypertension via YAP1 Signaling
    (MDPI, 2022-11-22) Chen, Jiwang; Lockett, Angelia; Zhao, Shuangping; Huang, Long Shuang; Wang, Yifan; Wu, Weiwen; Tang, Ming; Haider, Shahzaib; Velez Rendon, Daniela; Khan, Raheel; Liu, Bing; Felesena, Nicholas; Sysol, Justin R.; Valdez-Jasso, Daniela; Tang, Haiyan; Bai, Yang; Natarajan, Viswanathan; Machado, Roberto F.; Medicine, School of Medicine
    Sphingosine kinase 1 (SPHK1) and the sphingosine-1-phosphate (S1P) signaling pathway have been shown to play a role in pulmonary arterial hypertension (PAH). S1P is an important stimulus for pulmonary artery smooth muscle cell (PASMC) proliferation and pulmonary vascular remodeling. We aimed to examine the specific roles of SPHK1 in PASMCs during pulmonary hypertension (PH) progression. We generated smooth muscle cell-specific, Sphk1-deficient (Sphk1f/f TaglnCre+) mice and isolated Sphk1-deficient PASMCs from SPHK1 knockout mice. We demonstrated that Sphk1f/f TaglnCre+ mice are protected from hypoxia or hypoxia/Sugen-mediated PH, and pulmonary vascular remodeling and that Sphk1-deficient PASMCs are less proliferative compared with ones isolated from wild-type (WT) siblings. S1P or hypoxia activated yes-associated protein 1 (YAP1) signaling by enhancing its translocation to the nucleus, which was dependent on SPHK1 enzymatic activity. Further, verteporfin, a pharmacologic YAP1 inhibitor, attenuated the S1P-mediated proliferation of hPASMCs, hypoxia-mediated PH, and pulmonary vascular remodeling in mice and hypoxia/Sugen-mediated severe PH in rats. Smooth muscle cell-specific SPHK1 plays an essential role in PH via YAP1 signaling, and YAP1 inhibition may have therapeutic potential in treating PH.