Fundamental Role for HIF‐2‐regulated Creatine Kinase Pathway in Epithelial Apical Junctional Integrity

Abstract

Intestinal epithelia of the lower GI tract are subjected to frequent, pronounced fluctuations in oxygen tension, particularly in inflammation. Adaptive responses to hypoxia are driven largely by hypoxia‐inducible factor (HIF). Given the co‐expression of HIF‐1α and HIF‐2α in intestinal epithelial cells (IECs), we sought to comprehensively define the contribution of HIF‐1/‐2 transactivation to IEC homeostasis. A ChIP‐on‐chip screen of HIF‐1/‐2‐enriched chromatin identified creatine kinase (CK) isozymes and the creatine transporter as novel HIF‐2 targets. CK enzymes temporally regulate ATP regeneration through transfer of high‐energy phosphate from phosphocreatine (PCr) to ADP. Promoter‐reporter and ChIP‐qPCR analyses confirmed HIF‐2 CK binding and transactivation. Immunolocalization studies revealed that CK's localize to cell and tissue adherens junctions (AJ). Pharmacological inhibition of CK significantly attenuated AJ assembly and functionally attenuated epithelial barrier. In vivo, dietary Cr supplementation in two murine models of colitis significantly ameliorated disease. Further analyses in human IBD tissues revealed reduced expression of CK isoforms. These results support a prominent role for HIF‐2‐regulated CK in IEC junctional homeostasis, and implicate a fundamental link between cellular energy and junctional integrity. (Funding: NIH, CCFA)