Regulation of Transient Receptor Potential Canonical 4 Activity by Phospholipase C-δ1

Abstract Transient receptor potential canonical (TRPC) channels are non-selective calcium-permeable cation channels. It is suggested that TRPC4β and TRPC5 channels are regulated by phospholipase C (PLC) signaling, and are especially maintained by phosphatidylinositol 4,5-bisphosphate (PIP 2 ). The PLCδ subtype is the most Ca 2+ -sensitive form among the isozymes which cleaves phospholipids to respond to the calcium rise. In this study, we investigated the regulation mechanism of TRPC channel by Ca 2+ , PLCδ1 and PIP 2 signaling cascades. The interaction between TRPC4β and PLCδ1 was identified through the Fӧster resonance energy transfer (FRET) and co-immunoprecipitation (Co-IP). With the electrophysiological experiments, we found that TRPC4β-bound PLCδ1 reduces the overall whole-cell current of channel. The Ca 2+ -via opened channel promotes the activation of PLCδ1, which subsequently decreases PIP 2 level. By comparison TRPC4β activity with or without PLCδ1 using differently [Ca 2+ ] i buffered solution, we demonstrated that PLCδ1 functions in normal condition with physiological calcium range. The negative regulation effect of PLCδ1 on TRPC4β helps to elucidate the roles of each PIP 2 binding residues whether they are concerned in channel maintenance or inhibition of channel activity.