title: Rac GTPase isoform-specific regulation of NADPH oxidase and chemotaxis in murine neutrophils in vivo. Role of the C-terminal polybasic domain.
abstract: The Rho family GTPase Rac acts as a molecular switch for signal transduction to regulate various cellular functions. Mice deficient in the hematopoietic-specific Rac2 isoform exhibit agonist-specific defects in neutrophil chemotaxis and superoxide production, despite expression of the highly homologous Rac1 isoform. To examine whether functional defects in rac2(-/-) neutrophils reflect effects of an overall decrease in total cellular Rac or an isoform-specific role for Rac2, retroviral vectors were used to express exogenous Rac1 or Rac2 at levels similar to endogenous. In rac2(-/-) neutrophils differentiated from transduced myeloid progenitors in vitro, increasing cellular Rac levels by expression of either exogenous Rac1 or Rac2 increased formylmethionylleucylphenylalanine- or phorbol ester-stimulated NADPH oxidase activity. Of note, placement of an epitope tag on the N terminus of Rac1 or Rac2 blunted reconstitution of responses in rac2(-/-) neutrophils. In rac2(-/-) neutrophils isolated from mice transplanted with Rac-transduced bone marrow cells, superoxide production and chemotaxis were fully reconstituted by expression of exogenous Rac2, but not Rac1. A chimeric Rac1 protein in which the Rac1 C-terminal polybasic domain, which contains six lysines or arginines, was replaced with that of the human Rac2 polybasic domain containing only three basic residues, also reconstituted superoxide production and chemotaxis, whereas expression of a Rac2 derivative in which the polybasic domain was replaced with that of Rac1 did not and resulted in disoriented cell motility. Thus, the composition of the polybasic domain is sufficient for determining Rac isoform specificity in the production of superoxide and chemotaxis in murine neutrophils in vivo.
authors.affiliation: Herman B Wells Center for Pediatric Research, the Department of Pediatrics (Hematology/Oncology), James Whitcomb Riley Hospital for Children, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA.
authors.forename: Akira
authors.initials: A
authors.lastname: Yamauchi
authors.forename: Christophe C
authors.initials: CC
authors.lastname: Marchal
authors.forename: Jason
authors.initials: J
authors.lastname: Molitoris
authors.forename: Nancy
authors.initials: N
authors.lastname: Pech
authors.forename: Ulla
authors.initials: U
authors.lastname: Knaus
authors.forename: Jason
authors.initials: J
authors.lastname: Towe
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Atkinson
authors.forename: Mary C
authors.initials: MC
authors.lastname: Dinauer
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002454:Cell Differentiation; D002634:Chemotaxis, Leukocyte / Q000187:drug effects; D007527:Isoenzymes / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D019255:NADPH Oxidases / Q000378:metabolism*; D018375:Neutrophil Activation / Q000187:drug effects; D009504:Neutrophils / Q000166:cytology* / Q000201:enzymology / Q000276:immunology / Q000378:metabolism*; D012190:Retroviridae / Q000235:genetics; D014161:Transduction, Genetic; D020744:rac GTP-Binding Proteins / Q000145:classification* / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D000097766:RAC2 GTP-Binding Protein
chemical_list: D007527:Isoenzymes; D009240:N-Formylmethionine Leucyl-Phenylalanine; D019255:NADPH Oxidases; D020744:rac GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein; D000097766:RAC2 GTP-Binding Protein