Differential regulation of β2-adrenoceptor and adenosine A2B receptor signalling by GRK and arrestin proteins in arterial smooth muscle.

Abstract Generation of cAMP through G s -coupled G protein-coupled receptor (GPCR) [ e.g. β 2 -adrenoceptor (β 2 AR), adenosine A 2B receptor (A 2B R)] activation, induces arterial smooth muscle relaxation, counteracting the actions of vasoconstrictors. G s -coupled GPCR signalling is regulated by G protein-coupled receptor kinases (GRK) and arrestin proteins, and dysregulation of Gs/GPCR signalling is thought play a role in the development of hypertension, which may be a consequence of enhanced GRK2 and/or arrestin expression. However, despite numerous studies indicating that β 2 AR and A 2B R can be substrates for GRK/arrestin proteins, currently little is known regarding GRK/arrestin regulation of these endogenous receptors in arterial smooth muscle. Here, endogenous GRK isoenzymes and arrestin proteins were selectively depleted using RNA-interference in rat arterial smooth muscle cells (RASM) and the consequences of this for β 2 AR- and A 2B R-mediated adenylyl cyclase (AC) signalling were determined by assessing cAMP accumulation. GRK2 or GRK5 depletion enhanced and prolonged β 2 AR/AC signalling, while combined deletion of GRK2/5 has an additive effect. Conversely, activation of AC by A 2B R was regulated by GRK5, but not GRK2. β 2 AR desensitization was attenuated following combined GRK2/GRK5 knockdown, but not by depletion of individual GRKs, arrestins, or by inhibiting PKA. Arrestin3 (but not arrestin2) depletion enhanced A 2B R-AC signalling and attenuated A 2B R desensitization, while β 2 AR-AC signalling was regulated by both arrestin isoforms. This study provides a first demonstration of how different complements of GRK and arrestin proteins contribute to the regulation of signalling and desensitization of these important receptors mediating vasodilator responses in arterial smooth muscle. Graphical abstract Unlabelled Image Highlights • Depletion of GRK2 or GRK5 enhanced and prolonged β 2 AR adenylyl cyclase activity. • Combined GRK2/GRK5 knockdown further enhanced β 2 AR adenylyl cyclase activity. • Combined knockdown of GRK2 and GRK5 attenuated β 2 AR receptor desensitization. • Depletion of GRK5 enhanced acute adenosine A 2B -stimulated adenylyl cyclase activity. • Adenosine A 2B receptor desensitization was GRK5 and arrestin3 dependent. [ABSTRACT FROM AUTHOR]