title: Defective lymphocyte chemotaxis in beta-arrestin2- and GRK6-deficient mice.
abstract: Lymphocyte chemotaxis is a complex process by which cells move within tissues and across barriers such as vascular endothelium and is usually stimulated by chemokines such as stromal cell-derived factor-1 (CXCL12) acting via G protein-coupled receptors. Because members of this receptor family are regulated ("desensitized") by G protein-coupled receptor kinase (GRK)-mediated receptor phosphorylation and beta-arrestin binding, we examined signaling and chemotactic responses in splenocytes derived from knockout mice deficient in various beta-arrestins and GRKs, with the expectation that these responses might be enhanced. Knockouts of beta-arrestin2, GRK5, and GRK6 were examined because all three proteins are expressed at high levels in purified mouse CD3+ T and B220+ B splenocytes. CXCL12 stimulation of membrane GTPase activity was unaffected in splenocytes derived from GRK5-deficient mice but was increased in splenocytes from the beta-arrestin2- and GRK6-deficient animals. Surprisingly, however, both T and B cells from beta-arrestin2-deficient animals and T cells from GRK6-deficient animals were strikingly impaired in their ability to respond to CXCL12 both in transwell migration assays and in transendothelial migration assays. Chemotactic responses of lymphocytes from GRK5-deficient mice were unaffected. Thus, these results indicate that beta-arrestin2 and GRK6 actually play positive regulatory roles in mediating the chemotactic responses of T and B lymphocytes to CXCL12.
authors.affiliation: Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Alan M
authors.initials: AM
authors.lastname: Fong
authors.forename: Richard T
authors.initials: RT
authors.lastname: Premont
authors.forename: Ricardo M
authors.initials: RM
authors.lastname: Richardson
authors.forename: Yen-Rei A
authors.initials: YR
authors.lastname: Yu
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Lefkowitz
authors.forename: Dhavalkumar D
authors.initials: DD
authors.lastname: Patel
mesh_terms: D000818:Animals; D019390:Arrestins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D002634:Chemotaxis, Leukocyte / Q000235:genetics / Q000502:physiology*; D003433:Crosses, Genetic; D054774:G-Protein-Coupled Receptor Kinase 5; D054768:G-Protein-Coupled Receptor Kinases; D019204:GTP-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D005786:Gene Expression Regulation; D007700:Kinetics; D016131:Lymphocyte Subsets / Q000502:physiology; D008214:Lymphocytes / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D000071557:beta-Arrestins
chemical_list: D019390:Arrestins; D000071557:beta-Arrestins; D017346:Protein Serine-Threonine Kinases; D054774:G-Protein-Coupled Receptor Kinase 5; D054768:G-Protein-Coupled Receptor Kinases; C089176:G-protein-coupled receptor kinase 6; C517895:Grk5 protein, mouse; D019204:GTP-Binding Proteins