RGS2 protein degradation is mediated by a novel multiprotein E3 ligase containing Cullin 4b and F box 44

Abstract

Regulator of G protein signaling 2 (RGS2) is highly expressed in both heart and vascular smooth muscle and selectively regulates Gαq signaling. RGS2 KO mice are hypertensive, show increased responses to angiotensin and α‐adrenergic agonists as well as enhanced cardiomyocyte hypertrophy and death in heart failure models. RGS2 is rapidly degraded through the proteasome, but the exact mechanism for RGS2 protein degradation is not known. We hypothesize that stabilizing RGS2 protein expression could be a novel route in treating cardiovascular disease. RGS proteins are difficult drug targets. Therefore, identifying a more druggable protein within the degradation pathway could be a way to increase RGS2 protein function. The PathHunterTM ProLabel detection assay is a β‐galactosidase complementation assay that efficiently quantifies levels of proteins. Using this assay in a high‐throughput siRNA screen we identified several components of the ubiquitin protein degradation machinery and our results indicate that RGS2 is degraded through a cullin‐RING E3 ligase (CRL) containing Cullin 4B and F box protein 44. Furthermore, our results show that RGS2 and the closely related RGS4 utilize different degradation pathways. Increased understanding of RGS2 protein degradation should help identify new RGS2 modulators for cardiovascular disease. (Supported by NIH‐DA023252 and The Swedish Heart‐and Lung Foundation).