Dynamic Response of Arterial Cerebral Ca V 1.2 Channels to Intravascular Pressure

Abstract

Intravascular pressure elicits arterial constriction by elevating intracellular [Ca2+] in vascular smooth muscle cells (SMCs). Past studies have argued that this rise is singularly linked to depolarization and the voltage-dependent gating of L-type (CaV1.2) Ca2+ channels. While important, pressure might also directly modulate CaV1.2 activity by promoting functional coupling among subunits, a response that enhances Ca2+ sparklets generation. In this regard, the study goal was to define the mechanosensitivity of CaV1.2 channels using a range of electrophysiological approaches. Beginning with whole-cell patch clamp electrophysiology, we show that SMCs stretching by a hypoosmotic challenge (from 300 to 200 mOsm) leads to a marked rise in total Ca2+ current (around 40%) without changing voltage-dependent activation/inactivation properties. This mechanosensitive response reflects augmented functional coupling, as revealed through recordings of single channel activity. Ongoing work has further revealed that the rise in functional coupling was intimately linked to caveolin-1, caveolae forming membrane protein tied to the cytoskeleton dynamics and signal transduction. This protein-protein relationship was also observed at the immunohistochemical level, with the proximity ligation assay showing that CaV1.2 colocalizes with caveolin-1 when SMCs are stretched by the hypoosmotic challenge. In closing, the current work reveals that CaV1.2 channels are a dynamic target of intravascular pressure and likely integral to a robust myogenic response. Continuing work will define the composition of the pressure-sensitive signaling complex and how it is impacted by disease.