β-blockers augment L-type Ca2+ channel activity by targeting spatially restricted β2AR signaling in neurons

Abstract

G protein-coupled receptors (GPCRs) transduce pleiotropic intracellular signals in mammalian cells. Here, we report neuronal excitability of β-blockers carvedilol and alprenolol at clinically relevant nanomolar concentrations. Carvedilol and alprenolol activate β2AR, which promote G protein signaling and cAMP/PKA activities without action of G protein receptor kinases (GRKs). The cAMP/PKA activities are restricted within the immediate vicinity of activated β2AR, leading to selectively enhance PKA-dependent phosphorylation and stimulation of endogenous L-type calcium channel (LTCC) but not AMPA receptor in rat hippocampal neurons. Moreover, we have engineered a mutant β2AR that lacks the catecholamine binding pocket. This mutant is preferentially activated by carvedilol but not the orthosteric agonist isoproterenol. Carvedilol activates the mutant β2AR in mouse hippocampal neurons augmenting LTCC activity through cAMP/PKA signaling. Together, our study identifies a mechanism by which β-blocker-dependent activation of GPCRs promotes spatially restricted cAMP/PKA signaling to selectively target membrane downstream effectors such as LTCC in neurons.

beta-blocker reverses inhibition of beta-2 adrenergic receptor resensitization by hypoxia

“…β2AR-HEK 293 cells were pre-treated with β-blocker propranolol followed by either hypoxia or normoxia and phosphorylation of β2AR was assessed by immunoblotting. Consistent with previous studies [28], significant phosphorylation of β2ARs was observed in normoxia in response to β-blocker (n=5) [ Fig. 6A & B ].…”

Subcellular Organization of the cAMP Signaling Pathway

“…The hypothesis is that the impact of G α subunits on receptor membrane distribution could account for receptor-biased pharmacology such that a specific ligand could promote different conformations of the GPCR/G protein complexes, with different outputs depending on their compartmentalization at the cell surface. How biased signaling intersects with compartmentalized cAMP signaling is an important question that remains largely unexplored ( Shen et al, 2019 ).…”

Nanoscale regulation of L-type calcium channels differentiates between ischemic and dilated cardiomyopathies.

“…It has been proposed that bAR-induced stimulation of Cav1.2 does not need PKA targeting the subunits of the channel, rather an additional protein, Rad is shown to be involved [47]. The specific interaction between b2AR and Cav1.2 has also been unraveled in recent years, from an essential residue in the Cav1.2 for b2AR binding [48], to the activation of different pathways by nano-molar concentrations of b-blockers [49]. CaMKII could also play an important role as a secondary mechanism.…”