Rab1 interacts directly with the β2-adrenergic receptor to regulate receptor anterograde trafficking.
ABSTRACT Very little is understood about the trafficking of G protein-coupled receptors (GPCRs) from the endoplasmic reticulum (ER) to the plasma membrane. Rab guanosine triphosphatases (GTPases) are known to participate in the trafficking of various GPCRs via a direct interaction during the endocytic pathway, but whether this occurs in the anterograde pathway is unknown. We evaluated the potential interaction of Rab1, a GTPase known to regulate β2-adrenergic receptor (β2AR) trafficking, and its effect on export from the ER. Our results show that GTP-bound Rab1 interacts with the F(x)(6)LL motif of β2AR. Receptors lacking the interaction motif fail to traffic properly, suggesting that a direct interaction with Rab1 is required for β2AR anterograde trafficking.
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ABSTRACT: Export from the endoplasmic reticulum (ER) represents an initial step in intracellular trafficking of G protein-coupled receptors (GPCRs). However, the underlying molecular mechanisms remain poorly understood. We have previously demonstrated that a highly conserved Leu residue on the first intracellular loop (ICL1) is required for exit of several GPCRs from the ER. Here we found that, in addition to Leu64 residue in the ICL1, the neighboring positively charged residue Lys65also modulates the cell-surface transport of α(2A)-adrenergic receptor (α(2A)-AR). Mutation of Lys65 to Ala, Glu and Gln significantly attenuated, whereas mutation of Lys65 to Arg strongly augmented α(2A)-AR expression at the cell surface. Consistent with the effects on the cell-surface expression of α(2A)-AR, mutation of Lys65 to Ala and Arg produced opposing effects on α(2A)-AR-mediated ERK1/2 activation. Furthermore, confocal microscopy revealed that the α(2A)-AR mutant K65A displayed a strong intracellular expression pattern and was extensively co-localized with the ER marker DsRed2-ER, suggestive of ER accumulation. These data provide the first evidence indicating an important function for a single Lys residue on the ICL1 in the ER export and cell-surface expression of α(2A)-AR. These data also suggest that the ICL1 may possess multiple signals that control the cell-surface targeting of GPCRs via distinct mechanisms.PLoS ONE 01/2012; 7(12):e50416. · 3.73 Impact Factor