title: Differential regulation of CXCR2 trafficking by Rab GTPases.
abstract: Intracellular trafficking of chemokine receptors plays an important role in fine-tuning the functional responses of neutrophils and lymphocytes in the inflammatory process and HIV infection. Although many chemokine receptors internalize through clathrin-coated pits, regulation of the receptor trafficking is not fully understood. The present study demonstrated that CXCR2 was colocalized with transferrin and low-density lipoprotein (LDL) after agonist treatment for different periods of time, suggesting 2 intracellular trafficking pathways for this receptor. CXCR2 was colocalized with Rab5 and Rab11a, which are localized in early and recycling endosomes, respectively, in response to agonist stimulation for a short period of time, suggesting a recycling pathway for the receptor trafficking. However, overexpression of a dominant-negative Rab5-S34N mutant significantly attenuated CXCR2 sequestration. The internalized CXCR2 was recycled back to the cell surface after removal of the agonist and recovery of the cells, but receptor recycling was inhibited by overexpression of a dominant-negative Rab11a-S25N mutant. After prolonged (4-hour) agonist treatment, CXCR2 exhibited significantly increased colocalization with Rab7, which is localized in late endosomes. The colocalization of CXCR2 with LDL and LAMP-1 suggests that CXCR2 is targeted to lysosomes for degradation after prolonged ligand treatment. However, the colocalization of CXCR2 with Lamp1 was blocked by the overexpression of a dominant-negative Rab7-T22N mutant. In cells overexpressing Rab7-T22N, CXCR2 was retained in the Rab5- and Rab11a-positive endosomes after prolonged (4-hour) agonist treatment. Our data suggest that the intracellular trafficking of CXCR2 is differentially regulated by Rab proteins.
authors.affiliation: Department of Veterans Affairs, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
authors.forename: Guo-Huang
authors.initials: GH
authors.lastname: Fan
authors.forename: Lynne A
authors.initials: LA
authors.lastname: Lapierre
authors.forename: James R
authors.initials: JR
authors.lastname: Goldenring
authors.forename: Ann
authors.initials: A
authors.lastname: Richmond
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000032:analysis; D001692:Biological Transport; D002460:Cell Line; D004622:Embryo, Mammalian; D011992:Endosomes / Q000737:chemistry / Q000378:metabolism; D015870:Gene Expression; D049452:Green Fluorescent Proteins; D006801:Humans; D007668:Kidney; D015471:Leukemia, Basophilic, Acute; D008077:Lipoproteins, LDL / Q000032:analysis; D008164:Luminescent Proteins / Q000235:genetics; D052118:Lysosomal-Associated Membrane Protein 1; D051907:Lysosomal Membrane Proteins; D008247:Lysosomes / Q000378:metabolism; D018613:Microscopy, Confocal; D009154:Mutation; D051381:Rats; D023063:Receptors, Interleukin-8B / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D014168:Transferrin / Q000032:analysis; D014407:Tumor Cells, Cultured; D020691:rab GTP-Binding Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D020696:rab5 GTP-Binding Proteins / Q000032:analysis / Q000235:genetics; D000090802:rab7 GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins
chemical_list: D015703:Antigens, CD; D049452:Green Fluorescent Proteins; D008077:Lipoproteins, LDL; D008164:Luminescent Proteins; D052118:Lysosomal-Associated Membrane Protein 1; D051907:Lysosomal Membrane Proteins; D023063:Receptors, Interleukin-8B; D014168:Transferrin; D020691:rab GTP-Binding Proteins; D020696:rab5 GTP-Binding Proteins; D000090802:rab7 GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins; C000716463:rab7 GTP-binding proteins, human; C000716466:rab7 GTP-binding proteins, rat