title: Postendocytotic traffic of the galanin R1 receptor: a lysosomal signal motif on the cytoplasmic terminus.
abstract: The neuropeptide galanin R1 receptor (GalR1) was tagged at its C terminus with EGFP (GalR1-EGFP) to study receptor localization and trafficking. In PC12 and HEK293 cells, functional GalR1-EGFP was expressed on the plasma membrane and internalized into cytoplasmic vesicles after galanin stimulation. The internalization was blocked by 0.4 M sucrose and by silencing of clathrin with siRNA methodology. Internalized GalR1-EGFP and LysoTracker, a lysosomal marker, overlapped in intracellular vesicles after prolonged galanin stimulation. This colocalization was strongly reduced after site-directed mutagenesis of the motif YXXØ on the C terminus of GalR1 (where Ø is a bulky hydrophobic residue and X any amino acid). Taken together, these data suggest that GalR1 is internalized via the clathrin-dependent, endocytic pathway and then, to a large extent, delivered to lysosomes for degradation through the lysosome-targeting signal YXXØ.
authors.affiliation: Departments of Neuroscience and Physiology and Pharmacology, Karolinska Institutet, S-171 77 Stockholm, Sweden.
authors.forename: Sheng
authors.initials: S
authors.lastname: Xia
authors.forename: Xing-Peng
authors.initials: XP
authors.lastname: Dun
authors.forename: Ping-Sheng
authors.initials: PS
authors.lastname: Hu
authors.forename: Svend
authors.initials: S
authors.lastname: Kjaer
authors.forename: Kang
authors.initials: K
authors.lastname: Zheng
authors.forename: Yu
authors.initials: Y
authors.lastname: Qian
authors.forename: Christina
authors.initials: C
authors.lastname: Solén
authors.forename: Tao
authors.initials: T
authors.lastname: Xu
authors.forename: Bertil
authors.initials: B
authors.lastname: Fredholm
authors.forename: Tomas
authors.initials: T
authors.lastname: Hökfelt
authors.forename: Zhi-Qing David
authors.initials: ZQ
authors.lastname: Xu
mesh_terms: D020816:Amino Acid Motifs / Q000502:physiology; D002460:Cell Line; D002966:Clathrin; D003593:Cytoplasm / Q000378:metabolism; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism; D019004:Galanin / Q000494:pharmacology; D049452:Green Fluorescent Proteins; D006801:Humans; D008247:Lysosomes / Q000378:metabolism*; D021381:Protein Transport; D044091:Receptor, Galanin, Type 1 / Q000378:metabolism*; D013395:Sucrose
chemical_list: D002966:Clathrin; D044091:Receptor, Galanin, Type 1; D049452:Green Fluorescent Proteins; D013395:Sucrose; D019004:Galanin