Impact of C-Terminal PKC Phosphorylation on TRPC6 Current Kinetics

Transient receptor potential canonical 6 (TRPC6) channels are promising drug targets for kidney, lung, and neurological diseases, making a detailed understanding of their regulation crucial to developing novel channel modulators with more precise modes of action. TRPC6 channels are commonly accepted as calcium-permeable, receptor-operated cation channels activated by diacylglycerol (DAG) downstream of phospholipase C (PLC) signaling. DAG, the endogenous activator of TRPC channels, also activates protein kinase C (PKC), which can phosphorylate TRPC6 and potentially modify its function. This study examined whether five putative PKC phosphorylation sites located in the C-terminus of TRPC6 affect channel gating. Using whole-cell patch-clamp recordings and utilizing photopharmacology with photoswitchable TRPC6 activators (OptoBI-1 and OptoDArG), we analyzed the activation, inactivation, and deactivation kinetics. Pharmacological modulation of PKC activity and strategic mutation of the phosphorylation sites—either to prevent or mimic phosphorylation—altered the current kinetics as well as the normalized slope conductances that were used to quantify differences in the curve progression of current–voltage relations, even when maximally induced current density amplitudes were unchanged. Our findings reveal activator-specific differences in TRPC6 current kinetics associated with C-terminal amino acid exchanges and PKC-dependent signaling, suggesting that phosphorylation-related mechanisms may fine-tune channel activity.