title: Impaired recruitment of Grk6 and beta-Arrestin 2 causes delayed internalization and desensitization of a WHIM syndrome-associated CXCR4 mutant receptor.
abstract: WHIM (warts, hypogammaglobulinemia, infections, and myelokatexis) syndrome is a rare immunodeficiency syndrome linked to heterozygous mutations of the chemokine receptor CXCR4 resulting in truncations of its cytoplasmic tail. Leukocytes from patients with WHIM syndrome display impaired CXCR4 internalization and enhanced chemotaxis in response to its unique ligand SDF-1/CXCL12, which likely contribute to the clinical manifestations. Here, we investigated the biochemical mechanisms underlying CXCR4 deficiency in WHIM syndrome. We report that after ligand activation, WHIM-associated mutant CXCR4 receptors lacking the carboxy-terminal 19 residues internalize and activate Erk 1/2 slower than wild-type (WT) receptors, while utilizing the same trafficking endocytic pathway. Recruitment of beta-Arrestin 2, but not beta-Arrestin 1, to the active WHIM-mutant receptor is delayed compared to the WT CXCR4 receptor. In addition, while both kinases Grk3 and Grk6 bind to WT CXCR4 and are critical to its trafficking to the lysosomes, Grk6 fails to associate with the WHIM-mutant receptor whereas Grk3 associates normally. Since beta-Arrestins and Grks play critical roles in phosphorylation and internalization of agonist-activated G protein-coupled receptors, these results provide a molecular basis for CXCR4 dysfunction in WHIM syndrome.
authors: The Laboratory of Cellular Oncology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America. mccormpe@mail.nih.gov
authors: Peter J
authors: PJ
authors: McCormick
authors: Marta
authors: M
authors: Segarra
authors: Paola
authors: P
authors: Gasperini
authors: A Virginia
authors: AV
authors: Gulino
authors: Giovanna
authors: G
authors: Tosato
mesh_terms: D000595:Amino Acid Sequence; D019390:Arrestins / Q000378:metabolism*; D004705:Endocytosis; D005434:Flow Cytometry; D054770:G-Protein-Coupled Receptor Kinase 3 / Q000378:metabolism; D054768:G-Protein-Coupled Receptor Kinases / Q000378:metabolism*; D020868:Gene Silencing; D006367:HeLa Cells; D006801:Humans; D007153:Immunologic Deficiency Syndromes / Q000201:enzymology* / Q000473:pathology*; D008024:Ligands; D020935:MAP Kinase Signaling System; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport; D019718:Receptors, CXCR4 / Q000737:chemistry / Q000378:metabolism*; D014161:Transduction, Genetic; D000071559:beta-Arrestin 1; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins
chemical_list: C000605253:ARRB1 protein, human; C000605254:ARRB2 protein, human; D019390:Arrestins; D008024:Ligands; D050505:Mutant Proteins; D019718:Receptors, CXCR4; D000071559:beta-Arrestin 1; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins; D054770:G-Protein-Coupled Receptor Kinase 3; C517848:GRK3 protein, human; D054768:G-Protein-Coupled Receptor Kinases; C089176:G-protein-coupled receptor kinase 6