title: Identification of a transferable two-amino-acid motif (GT) present in the C-terminal tail of the human lutropin receptor that redirects internalized G protein-coupled receptors from a degradation to a recycling pathway.
abstract: Although highly homologous in amino acid sequence, the agonist-receptor complexes formed by the human lutropin receptor (hLHR) and rat (r) LHR follow different intracellular routes. The agonist-rLHR complex is routed mostly to a lysosomal degradation pathway whereas a substantial portion of the agonist-hLHR complex is routed to a recycling pathway. In a previous study, we showed that grafting a five-residue sequence (GTALL) present in the C-terminal tail of the hLHR into the equivalent position of the rLHR redirects a substantial portion of the internalized agonist-rLHR complex to a recycling pathway. Using a number of mutations of the GTALL motif, we now show that only the first two residues (GT) of this motif are necessary and sufficient to induce recycling of the internalized agonist-rLHR complex. Phosphoamino acid analysis and mutations of the GT motif show that phosphorylation of the threonine residue is not necessary for recycling. Lastly, we show that addition of portions of the C-terminal tail of the hLHR that include the GT motif to the C-terminal tails of the rat follitropin or murine delta-opioid receptors promotes the post-endocytotic recycling of these G protein-coupled receptors.We conclude that the GT motif present in the C-terminal tail of the hLHR is a transferable motif that promotes the postendocytotic recycling of several G protein-coupled receptors and that the GT-induced recycling does not require the phosphorylation of the threonine residue.
authors.affiliation: Department of Pharmacology, The University of Iowa, Iowa City, Iowa 52242-1109, USA.
authors.forename: Colette
authors.initials: C
authors.lastname: Galet
authors.forename: Le
authors.initials: L
authors.lastname: Min
authors.forename: Ramesh
authors.initials: R
authors.lastname: Narayanan
authors.forename: Mikiko
authors.initials: M
authors.lastname: Kishi
authors.forename: Nancy L
authors.initials: NL
authors.lastname: Weigel
authors.forename: Mario
authors.initials: M
authors.lastname: Ascoli
mesh_terms: D020816:Amino Acid Motifs / Q000502:physiology; D000595:Amino Acid Sequence; D000818:Animals; D002402:Cathepsin D / Q000378:metabolism; D002478:Cells, Cultured; D006063:Chorionic Gonadotropin / Q000378:metabolism; D015536:Down-Regulation / Q000502:physiology; D015180:Electrophoresis, Gel, Two-Dimensional; D004705:Endocytosis / Q000502:physiology; D005640:Follicle Stimulating Hormone / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D019606:Phosphoamino Acids / Q000032:analysis; D011233:Precipitin Tests; D051381:Rats; D011974:Receptors, LH / Q000235:genetics / Q000378:metabolism*; D017465:Receptors, Opioid, delta / Q000378:metabolism*; D016415:Sequence Alignment; D020696:rab5 GTP-Binding Proteins / Q000378:metabolism
chemical_list: D006063:Chorionic Gonadotropin; D019606:Phosphoamino Acids; D011974:Receptors, LH; D017465:Receptors, Opioid, delta; D005640:Follicle Stimulating Hormone; D002402:Cathepsin D; D019204:GTP-Binding Proteins; D020696:rab5 GTP-Binding Proteins