PSD95 scaffolding of the Shaker‐type K⁺ channel enables PKA‐dependent phosphorylation and vasodilation of cerebral arteries (1057.7)

Abstract

Postsynaptic density‐95 (PSD95) is a membrane‐associated scaffolding protein in rat cerebral vascular smooth muscle cells (cVSMC), which associates with voltage‐gated, Shaker‐type K+ (KV1) channels at the plasma membrane. Here, we used a membrane‐permeable peptide (KV1‐C) that competes with KV1.2 subunits for PSD95 binding to demonstrate the physiologic role of PSD95‐KV1.2 association in cVSMC. Application of 10 µM KV1‐C peptide to pressurized cerebral arteries (CA) induced vasoconstriction (23 ± 2%); the KV1 channel blocker, 5‐(4‐phenylalkoxypsoralen (100 nM psora4), did not further constrict these CA. Vasoconstriction by 1 µM linopirdine or 30 µM BaCl was unaffected by KV1‐C, suggesting that KV1‐C does not interfere with the dilator function of KV7 or KIR channels, respectively. cVSMCs in pressurized CA depolarized by 12 ± 2 mV in response to KV1‐C and psora4‐sensitive K+ current was reduced ~40% by KV1‐C peptide in cVSMCs. CA visualized in cranial windows in vivo also constricted (17 ± 3%) in response to KV1‐C. Finally, Western blots employing a phospho‐PKA substrate antibody revealed markedly less phosphorylation of KV1 channels in CA exposed to KV1‐C, and phosphatase inhibitors partially blunted KV1‐C mediated vasoconstriction. These results suggest that the PSD95 scaffold exerts a basal vasodilator influence in rat CA by enabling the phosphorylation ‐dependent and selective opening of KV1 channels. Grant Funding Source: Supported by NIH R01 HL097107 (SWR) and American Heart Association 13PRE17070035 (CLM)