α2B-Adrenergic receptor interaction with tubulin controls its transport from the endoplasmic reticulum to the cell surface

Abstract

It is well recognized that the C terminus (CT) plays a crucial role in modulating G protein-coupled receptor (GPCR) transport from the endoplasmic reticulum (ER) to the cell surface. However the molecular mechanisms that govern CT-dependent ER export remain elusive. To address this issue, we used α2Badrenergic receptor (α2B-AR) as a model GPCR to search for proteins interacting with the CT. By using peptide-conjugated affinity matrix combined with proteomics and glutathione S-transferase fusion protein pull-down assays, we identified tubulin directly interacting with the α2B-AR CT. The interaction domains were mapped to the acidic CT of tubulin and the basic Arg residues in the α2B-AR CT, particularly Arg-437, Arg-441, and Arg-446. More importantly, mutation of these Arg residues to disrupt tubulin interaction markedly inhibited α2B-AR transport to the cell surface and strongly arrested the receptor in the ER. These data provide the first evidence indicating that the α2B-AR C-terminal Arg cluster mediates its association with tubulin to coordinate its ER-to-cell surface traffic and suggest a novel mechanism of GPCR export through physical contact with microtubules.