A PLCγ1-Dependent, Force-Sensitive Signaling Network in the Myogenic Constriction of Cerebral Arteries

Maintaining constant blood flow in the face of fluctuations in blood pressure is a critical autoregulatory feature of cerebral arteries. An increase in pressure within the artery lumen causes the vessel to constrict through depolarization and contraction of the encircling smooth muscle cells. This pressure-sensing mechanism involves activation of two types of transient receptor potential (TRP) channels: TRPC6 and TRPM4. We provide evidence that the activation of the gamma 1 isoform of phospholipase C (PLC gamma 1) is critical for pressure sensing in cerebral arteries. Inositol 1,4,5-trisphosphate (IP3), generated by PLC gamma 1 in response to pressure, sensitized IP3 receptors (IP(3)Rs) to Ca2+ influx mediated by the mechanosensitive TRPC6 channel, synergistically increasing IP3R-mediated Ca2+ release to activate TRPM4 currents, leading to smooth muscle depolarization and constriction of isolated cerebral arteries. Proximity ligation assays demonstrated colocalization of PLC gamma 1 and TRPC6 with TRPM4, suggesting the presence of a force-sensitive, local signaling network comprising PLC gamma 1, TRPC6, TRPM4, and IP(3)Rs. Src tyrosine kinase activity was necessary for stretch-induced TRPM4 activation and myogenic constriction, consistent with the ability of Src to activate PLC gamma isoforms. We conclude that contraction of cerebral artery smooth muscle cells requires the integration of pressure-sensing signaling pathways and their convergence on IP(3)Rs, which mediate localized Ca2+-dependent depolarization through the activation of TRPM4.