Dynamic PKCδ‐Mediated Trafficking of TRPM4 Regulates Smooth Muscle Excitability

Abstract

The melastatin Transient Receptor Potential (TRP) channel TRPM4 is vital for pressure‐induced smooth muscle cell (SMC) depolarization and constriction of cerebral arteries. Protein kinase C (PKC) activity contributes to SMC excitability by a number of mechanisms, including TRPM4 activation. Although strong evidence shows a correlation between PKC, TRPM4 activity, and subsequent depolarization, the mechanisms underlying regulation of TRPM4 are unclear. Several TRP channels are regulated by dynamic, directed movement of channel protein into/out of the plasma membrane. Thus, we hypothesized that rapid insertion of TRPM4 into the plasma membrane in response to PKC activity regulates channel dynamics and controls SMC excitability. Consistent with this hypothesis, live‐cell fluorescence recovery after photobleaching (FRAP) analysis of GFP‐tagged TRPM4 indicate that the channel is mobile. Cell surface biotinylation and total internal reflection (TIRF) microscopy reveal that TRPM4 is rapidly inserted into the plasma membrane in response to PKCδ activity. Pressure‐myograph studies of intact cerebral arteries demonstrate that TRPM4 and PKCδ are involved in PKC‐induced constriction. We conclude that stimulation of PKCδ activity leads to membrane depolarization and vasoconstriction by increasing the number of TRPM4 channels in the sarcolemma. AHA0535226N