title: Role of C-terminal membrane-proximal basic residues in cell surface trafficking of HIV coreceptor GPR15 protein.
abstract: Cell surface density of G protein-coupled receptors (GPCRs) is controlled by dynamic molecular interactions that often involve recognition of the distinct sequence signals on the cargo receptors. We reported previously that the RXR-type dibasic motif in the distal C-terminal tail of an HIV coreceptor GPR15 negatively regulates the cell surface expression by mediating the coatomer protein I complex-dependent retrograde transport to the endoplasmic reticulum (ER). Here we demonstrate that another pair of basic residues (Arg(310)-Arg(311)) in the membrane-proximal region of the C-terminal tail plays a pivotal role in mediating the anterograde trafficking of GPR15. The Ala mutation of the C-terminal membrane-proximal basic residues (MPBRs) (R310/311A) abolished the O-glycosylation and cell surface expression of GPR15. The subcellular fractionation and immunocytochemistry assays indicated that the R310/311A mutant was more localized in the ER but much less in the trans-Golgi when compared with the wild-type GPR15, suggesting the positive role of Arg(310)-Arg(311) in the ER-to-Golgi transport of GPR15. Sequence analysis on human GPCRs showed that the basic residues are frequent in the membrane-proximal region of the C-terminal tail. Similar to GPR15, mutation of the C-terminal MPBRs resulted in a marked reduction of the cell surface expression in multiple different GPCRs. Our results suggest that the C-terminal MPBRs are critically involved in mediating the anterograde trafficking of a broad range of membrane proteins, including GPCRs.
authors: Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL 60607, USA.
authors: Yukari
authors: Y
authors: Okamoto
authors: Joshua David
authors: JD
authors: Bernstein
authors: Sojin
authors: S
authors: Shikano
mesh_terms: D000409:Alanine / Q000378:metabolism; D000595:Amino Acid Sequence; D002462:Cell Membrane / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005434:Flow Cytometry / Q000379:methods; D006056:Golgi Apparatus / Q000378:metabolism; D057809:HEK293 Cells; D006678:HIV / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D020559:Monomeric GTP-Binding Proteins / Q000378:metabolism; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*; D018000:Receptors, Peptide / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D033921:Vesicular Transport Proteins / Q000378:metabolism
chemical_list: C103539:GPR15 protein, human; D043562:Receptors, G-Protein-Coupled; D018000:Receptors, Peptide; C512739:SEC23A protein, human; C530638:SEC24A protein, human; D033921:Vesicular Transport Proteins; C493083:SAR1A protein, human; D020559:Monomeric GTP-Binding Proteins; D000409:Alanine