Beta1-Adrenergic Receptor-Mediated Dilation of Rat Cerebral Artery Requires Shaker-Type K_V1 Channels on PSD95 Scaffold

Abstract

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.

Molecular determinants of beta‐adrenergic signaling to voltage‐gated K+ channels in the cerebral circulation

“…Additionally, isoproterenol‐induced dilation was inhibited by the K v 1‐C peptide that disrupts PSD95‐K v 1 channel association and by a PKA inhibitor . Collectively, these results suggest that a β1AR‐PSD95‐K v 1 signalosome (Figure ) mediates the vasodilator response of cerebral arteries and arterioles to endogenous catecholamines or exogenous β‐AR agonists …”

“…Considering these facts, we recently proposed that a β1AR‐PSD95‐K v 1 complex in cVSMCs enables β1AR to signaling through PKA‐mediated phosphorylation of K v 1 channels, which mediates NE‐induced dilation of rat cerebral arteries . Notably, the expression of β1AR and its association with PSD95 in rat cerebral arteries were confirmed by real‐time RT‐PCR, Western blots, co‐immunoprecipitation, and confocal microscopy of cVSMCs . Indeed, NE and isoproterenol (Iso) dilated rat cerebral arteries in vivo (Figure A‐B), and similarly dilated and hyperpolarized rat cerebral arteries in vitro (Figure C‐D).…”

“…Interestingly, studies dating back to the 1980's report β1AR‐mediated dilation in cerebral arteries of rats and other mammals, instead of prevalent dilation by β2AR . Because β1AR has a C‐terminus PDZ‐binding motif (‐ESKV) that binds to the PDZ3 domain of PSD95, this receptor has surfaced as a prime candidate to be a member of the PSD95‐K v 1 vasodilator complex in cVSMCs (Figure ) . The predominance of β1AR in cVSMCs has important relevance for the regulation of cerebral blood flow, because: (i) β1AR but not β2AR contains the C‐terminus PDZ‐binding motif required for binding to PSD95; (ii) NE as an endogenous mixed adrenergic agonist has high affinity for α‐AR and β1AR, but not for β2AR; and (iii) the most widely used β‐AR‐blocking drug, metoprolol, selectively blocks β1AR over β2AR…”

“…SAP97 is known to interact with Kir channels that contribute to neurovascular coupling, and impaired function of Kir channels has been implicated in a poor blood flow response to transient global cerebral ischemia . The initial reports detailing scaffolding proteins in the rat cerebral circulation, including AKAP150 scaffolding of voltage‐gated Ca 2+ channels, and PSD95‐mediated association of β1AR and K v 1 channels, may provide impetus to explore MAGUK‐scaffolded signalosomes in other vascular beds. A clear definition of these vascular macromolecular complexes may represent an immediate opportunity to better decipher the complex networks that regulate vascular tone and affect pharmacological responses to medications, thereby impacting the lives of millions of patients with cardiovascular disorders.…”

Pharmacogenetic Associations of β1-Adrenergic Receptor Polymorphisms With Cardiovascular Outcomes in the SPS3 Trial (Secondary Prevention of Small Subcortical Strokes)

“…In smaller arteries such as small mesenteric resistance arteries 25–27 and cerebral arteries 28 , vasodilation may primarily depend upon β 1 AR stimulation. Another study showed that agonist-induced vasodilation of cerebral arteries is blunted by β 1 AR blockade 29 . If β 1 AR plays a similar role in small subcortical arteries as it does in peripheral resistance arteries and cerebral arteries, it is possible that perturbing the normal functioning of β 1 AR may attenuate its vasodilating effects in small subcortical arteries.…”