HACE1 localized in recycling endosome regulates the recycling and degradation of β_1-adrenergic receptor via Rab11 and Rab12.

Abstract

β_1-adrenergic receptor (β₁AR) is a potent regulator of cardiac function. Previously, we showed that recycling endosome (RE) is key organelle of the intracellular trafficking of β₁AR induced by ligand stimulus. Here, we found that HACE1, an E3 ligase, is localized in RE and ubiquitinates β₁AR internalized by the ligand isoproterenol (Iso). Silencing of HACE1 by siRNA resulted in a decline of β₁AR on the cell surface at steady state. Given that the ubiquitinated Rab11 functions as a recycling factor, ubiquitinated Rab11 mediated by HACE1 might recycle β₁AR to the cell surface. Ubiquitination of β₁AR was increased by Iso treatment, which was further enhanced with either bafilomycin A₁(BafA₁), a lysosome inhibitor or MG132, a proteasome inhibitor. β₁AR was co-localized with Rab12 at RE and lysosome and interacted with each other. The co-localization at lysosome was strengthened in the presence of BafA₁, and the interaction was enhanced by Iso stimulus. Silencing of Rab12 led to stabilization of β₁AR with or without Iso. These data suggest that Rab11 and Rab12 were involved in the recycling and degradation of β₁AR through ubiquitination of Rab11and β₁AR mediated by HACE1 in RE, respectively.