Blood Pressure Regulates Functional Coupling of L-Type Ca2+ Channels: Reimaging the Foundation of Cerebral Blood Flow Control.
The myogenic response is the key autoregulatory mechanism setting cerebral blood flow and its mechanistic foundation is intimately tied to depolarization and the voltage gating of L-type Ca2+ channels (CaV1.2). While critical, this study argues for an additional mechanism, that of pressure itself enhancing CaV1.2 activity via cooperative gating and perimembrane trafficking of channels subunits. These novel insights were pursued at the cell level using patch-clamp electrophysiology and advanced microscopy, and then functionally in pressurized arteries through measures of tone and intracellular [Ca2+]i. Key findings were confirmed in mutant mice with disrupted functional coupling and translated into arteries procured from human brain tissue. From cerebral blood flow simulations of semi-realistic microvascular networks, we predict that loss of this alternative mechanism leads to maldistribution of brain blood flow and potentially a diminishment of cognitive function. This study reveals previously unrecognized pressure-sensitive CaV1.2 regulatory mechanism that advances understanding of cerebral blood flow. SignificanceBlood pressure sets base arterial constriction - a response critical for blood flow control in brain. This response is tied to CaV1.2 channels and their presumptive and exclusive activation by voltage, reasoning now under great scrutiny. We establish herein with advance methods, a second mode of CaV1.2 pressure regulation, that of enhanced functional cooperativity among neighboring channels. This novel mechano-response is tied to PKC and its ability to set channel phosphorylation and CaV1.2 trafficking. CaV1.2 pressure regulation was observed in human tissues and its disruption (mutant mice) impaired myogenic tone in the presence of preserved voltage control. Cerebral microvascular modeling highlights that losing this mechanism destabilizes blood flow distribution in brain, the knock-on effect being comprised cognitive function.