Regulated intramembrane proteolysis contributes to control of the osmoprotective transcription factor, NFAT5

Abstract

Nuclear Factor of Activated T‐Cells 5 (NFAT5, also TonEBP or OREBP) increases transcription of osmoprotective genes in response to hypertonicity. Regulated intramembrane proteolysis (RIP) is involved in a number of intracellular and extracellular signaling pathways. The present studies were aimed at testing for a possible role of RIP in controlling NFAT5 activity. RIP is activated by sheddases and intramembrane cleaving proteases (iCLiPs). We studied the effects of inhibitors of those proteases on NFAT5 transcriptional and transactivating activities, using luciferase reporters in HEK293 cells. We screened inhibitors of sheddases and iCLiPS, namely ADAM, MMP, β‐secretase, γ‐secretase, SPP, zinc metalloprotease, and rhomboid. Zinc metalloprotease inhibitor (1, 10 phenanthroline monohydrate) and rhomboid inhibitor (tosyl phenylalanine chloromethyl ketone: TPCK) inhibit hypertonicity induced NFAT5 transcriptional and transactivating activity in a dose dependent manner. Further, zinc metalloprotease inhibitor, but not rhomboid inhibitor, reduces hypertonicity‐induced increase of NFAT5 protein abundance. We conclude that RIP contributes to hypertonicity‐induced increase of NFAT5 activity. The research is funded by The Intramural Research Program of NHLBI, NIH.