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Differential regulation of the export of G protein‐coupled receptors from the endoplasmic reticulum by a GTP‐restricted Sar1 GTPase mutant
Author(s) -
Zhou Fuguo,
Wu Guangyu
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a249
Subject(s) - endoplasmic reticulum , microbiology and biotechnology , gtpase , golgi apparatus , g protein coupled receptor , receptor , copii , transport protein , g protein , intracellular , chemistry , small gtpase , gtp' , biology , signal transduction , secretory pathway , biochemistry , enzyme
The molecular mechanism underlying the export trafficking of G protein‐coupled receptors (GPCRs) remains poorly defined. We have previously demonstrated that the Ras‐like small GTPase Rab1 selectively regulates the transport from the endoplasmic reticulum (ER) to the cell surface of angiotensin II type 1 (AT1R) and β 2 adrenergic receptors (β 2 ‐AR). In contrast, the cell surface transport of α 2 B‐AR is independent of Rab1, indicating that there are distinct pathways mediating GPCR movement from the ER to the cell surface. In this report, we investigated the role of Sar1 GTPase in the exit from the ER of AT1R, β2‐AR and α 2 B‐AR in HEK293 cells. Sar1 is a crucial regulator in the assembly of the COPII‐coated vesicles that mediate protein transport exclusively from the ER to the Golgi. Expression of the dominant‐negative GTP‐restricted Sar1H79G mutant significantly inhibited the cell‐surface expression of AT1R, β 2 ‐AR and α 2 B‐AR as measured by intact cell ligand binding, suggesting that the cell‐surface transport of three receptors is dependent on Sar1 function. The receptors were accumulated in the perinuclear region, consistent with the Sar1 function in the ER‐Golgi transport. Subcellular co‐localization of the receptors with intracellular organelle markers revealed that expression of Sar1H79G induced a marked accumulation of AT1R and α 2 BAR in the ER export sites without altering their exit from the ER. In contrast, Sar1H79G completely blocked β 2 ‐AR exit from the ER and β 2 ‐AR was completely unable to reach the ER exit sites. These data demonstrate that efficient GTP hydrolysis by Sar1 GTPase differentially regulates the export of AT1R, β 2 ‐AR and α 2 B‐AR at the ER membrane. These data suggest that the ER export may be a site for selective regulation of GPCR targeting to the cell surface (P20RR018766).