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 (PIP2). The PLCδ subtype is the most Ca2+-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 Ca2+, PLCδ1 and PIP2 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 Ca2+-via opened channel promotes the activation of PLCδ1, which subsequently decreases PIP2 level. By comparison TRPC4β activity with or without PLCδ1 using differently [Ca2+]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 PIP2 binding residues whether they are concerned in channel maintenance or inhibition of channel activity.