The β 2-adrenergic receptor antagonist carvedilol recruits MARCH2, a unique E3 ubiquitin ligase, to promote receptor endocytosis and lysosomal trafficking.
Lysosomal degradation of ubiquitinated β 2-adrenergic receptors (β 2ARs) serves as a major mechanism of long-term desensitization in response to prolonged agonist stimulation. Surprisingly, the βAR antagonist carvedilol also induced ubiquitination and lysosomal trafficking of both endogenously expressed β 2ARs in vascular smooth muscle cells (VSMCs) and overexpressed Flag-β 2ARs in HEK-293 cells. Carvedilol prevented β 2AR recycling, blocked recruitment of Nedd4 E3 ligase, and promoted the dissociation of the deubiquitinases USP20 and USP33. Using proteomics approaches (liquid chromatography–tandem mass spectrometry), we identified that the E3 ligase MARCH2 interacted with carvedilol-bound β 2AR. The association of MARCH2 with internalized β 2ARs was stabilized by carvedilol and did not involve β-arrestin. Small interfering RNA–mediated down-regulation of MARCH2 ablated carvedilol-induced ubiquitination, endocytosis, and degradation of endogenous β 2ARs in VSMCs. These findings strongly suggest that specific ligands recruit distinct E3 ligase machineries to activated cell surface receptors and direct their intracellular itinerary. In response to β blocker therapy with carvedilol, MARCH2 E3 ligase activity regulates cell surface β 2AR expression and, consequently, its signaling.