Postsynaptic density-95 (PSD95) is a scaffolding protein in cerebral vascular smooth muscle cells (cVSMCs), which binds to Shaker-type K(+) (KV1) channels and facilitates channel opening through phosphorylation by protein kinase A. β1-Adrenergic receptors (β1ARs) also have a binding motif for PSD95. Functional association of β1AR with KV1 channels through PSD95 may represent a novel vasodilator complex in cerebral arteries (CA). We explored whether a β1AR-PSD95-KV1 complex is a determinant of rat CA dilation. RT-PCR and western blots revealed expression of β1AR in CA. Isoproterenol induced a concentration-dependent dilation of isolated, pressurized rat CA that was blocked by the β1AR blocker CGP20712. Cranial window imaging of middle cerebral arterioles in situ showed isoproterenol- and norepinephrine-induced dilation that was blunted by β1AR blockade. Isoproterenol-induced hyperpolarization of cVSMCs in pressurized CA was blocked by CGP20712. Confocal images of cVSMCs immunostained with antibodies against β1AR and PSD95 indicated strong colocalization, and PSD95 co-immunoprecipitated with β1AR in CA lysate. Blockade of KV1 channels, β1AR or disruption of PSD95-KV1 interaction produced similar blunting of isoproterenol-induced dilation in pressurized CA. These findings suggest that PSD95 mediates a vasodilator complex with β1AR and KV1 channels in cVSMCs. This complex may be critical for proper vasodilation in rat CA.

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)