Insulin Modulates Hippo Signaling by Impairing YAP Function

Abstract

Yes‐associated protein (YAP) is the main transcriptional coactivator of the Hippo pathway, which regulates organ size, tissue homeostasis, and regeneration. YAP integrates multiple inputs from different signaling cascades. Recent evidence implicates YAP also in the control of nutrient and energy status of the cell, but the mechanisms underlying this function are unclear. In this study, we show that insulin modulates YAP activity in classic insulin target cells. We found by subcellular fractionation and Western blotting that insulin increases YAP phosphorylation, with a significant decrease in the abundance of YAP in the nuclei of HepG2 liver cells. Further, this regulation is likely mediated through the insulin receptor (IR), as overexpression of IR increased YAP phosphorylation. Proximity ligation assay analysis revealed a marked reduction in the interaction of YAP with TEA domain (TEAD) transcription factors in the nuclei of insulin‐treated cells. Consistent with these findings, insulin significantly impaired YAP/TEAD‐mediated transcription as measured by a dual luciferase assay in both HepG2 and C2C12 muscle cells. Further, quantitative PCR of HepG2 cells treated with insulin revealed reduced transcription of YAP regulated genes. Insulin alters transcription of numerous genes relevant to energy homeostasis, and we observed that knockdown of YAP by siRNA alters expression of genes in gluconeogenesis. Insulin stimulates activation of the phosphoinositide 3‐kinase (PI3K) pathway. The inhibitory effect of insulin on YAP transcription was abrogated by small‐molecule inhibitors of PI3K. Collectively, our results identify insulin as a previously undescribed suppressor of YAP activity and provide insight into an important link between the insulin and Hippo pathways.Support or Funding InformationThis work was supported by the National Institutes of Health Intramural Research Program.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.