Endothelin Receptor Heterodimerization Inhibits β-arrestin Function

Abstract

Dimerization of G-protein coupled receptors (GPCRs) can affect receptor dynamics at many stages of the GPCR life cycle. Endothelin receptors A (ETA) and B (ETB) are co-expressed in vascular smooth muscle cells, and are key to microvascular autoregulation through paracrine signalling following local release of endothelin (ET-1) by endothelial cells. Heterodimerization between ETA and ETB prolongs downstream signalling. We hypothesized in this study that endothelin receptor heterodimerization inhibits β-arrestin function, an important mediator in GPCR desensitization, thereby leading to temporal changes in signaling. Using BRET2 technology, the ETB homodimer and ETA/ETB heterodimer were found to form high affinity interactions, while ETA homodimerization did not occur. The heterodimer reduced and delayed recruitment of β-arrestin-2, and inhibited β-arrestin-1-dependent ERK signalling as assayed with In-Cell Western®. Thus, this study provides novel insights into how endothelin receptor heterodimerization could be affecting the physiological response to ET-1 in tissues co-expressing both receptor subtypes.