Platelet‐derived growth factor regulates YAP transcriptional activity via Src family kinase dependent tyrosine phosphorylation

• Published in: Journal of cellular biochemistry Vol. 119; no. 1; pp. 824 - 836
• Main Authors: Smoot, Rory L., Werneburg, Nathan W., Sugihara, Takaaki, Hernandez, Matthew C., Yang, Lin, Mehner, Christine, Graham, Rondell P., Bronk, Steven F., Truty, Mark J., Gores, Gregory J.
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01-01-2018
• Subjects: Adaptor Proteins, Signal Transducing - metabolism; Animals; Bile Duct Neoplasms - genetics; Bile Duct Neoplasms - metabolism; Biotechnology; Cell death; Cell Line, Tumor; Cell lines; Cell Nucleus - genetics; Cell Nucleus - metabolism; Cholangiocarcinoma; Cholangiocarcinoma - genetics; Cholangiocarcinoma - metabolism; Crosstalk; Cytosol; Gene expression; Gene Expression Regulation, Neoplastic; Genes; Growth factors; Hippo; Humans; Inhibition; Kinases; Localization; Malignancy; Mcl-1 protein; Mice; Neoplasm Transplantation; Nuclei; Nuclei (cytology); Pathogenesis; Pharmacology; Phosphoproteins - metabolism; Phosphorylation; Platelet-derived growth factor; Platelet-Derived Growth Factor - metabolism; Receptor, Platelet-Derived Growth Factor beta - metabolism; Serine; Signal Transduction; Signaling; siRNA; Src kinase family; Src protein; Transcription activation; Transcription Factors; Transcription, Genetic; Tyrosine; Up-Regulation; Xenografts; Yes-associated protein; platelet derived growth factor; Src kinase family; cholangiocarcinoma; Hippo
• ISSN: 0730-2312; 1097-4644
• DOI: 10.1002/jcb.26246

The Hippo pathway effector YAP is implicated in the pathogenesis of cholangiocarcinoma (CCA). The Hippo pathway relies on signaling cross talk for its regulation. Given the importance of platelet derived growth factor receptor (PDGFR) signaling in CCA biology, our aim was to examine potential YAP regulation by PDGFR. We employed human and mouse CCA specimens and cell lines for these studies. Initially, we confirmed upregulation of PDGFRβ and PDGFR ligands in human and mouse CCA specimens and cell lines. YAP, a transcriptional co‐activator, was localized to the nucleus in human CCA specimens and a cell line, as well as patient derived xenografts (PDX). PDGFR pharmacologic inhibition led to a redistribution of YAP from the nucleus to cytosol and downregulation of YAP target genes in a human CCA cell line. siRNA silencing of PDGFR‐β similarly downregulated YAP target genes. YAP activation (nuclear localization and target gene expression) was regulated by Src family kinases (SFKs) downstream of PDGFR. SFK activity resulted in phosphorylation of YAP on tyrosine357 (YAPY357). The importance of YAPY357 phosphorylation in regulating YAP activation was confirmed utilizing the SB‐1 cell line, a mouse cell line expressing YAP S127A precluding canonical serine phosphorylation. PDGFR inhibition decreased cellular abundance of the survival protein Mcl‐1, a known YAP target gene, and accordingly increased cell death in CCA cells in vitro and in vivo. These preclinical data demonstrate that a PDGFR‐SFK cascade regulates YAP activation via tyrosine phosphorylation in CCA. Inhibiting this cascade may provide a viable therapeutic strategy for this human malignancy.
Platelet derived growth factor inhibition decreases YAP nuclear localization and transcriptional activity. Tyrosine phosphorylation of YAP by Src family kinases determines subcellular localization in our models of cholangiocarcinoma. Inhibition of platelet derived growth factor signaling decreases cholangiocarcinoma cell viability.