title: Signaling requirements for translocation of P-Rex1, a key Rac2 exchange factor involved in chemoattractant-stimulated human neutrophil function.
abstract: PI 3,4,5-trisphosphate [PI(3,4,5)P3; PIP3]-dependent Rac exchanger 1 (P-Rex1) is a Rac-specific guanine nucleotide exchange factor abundant in neutrophils and myeloid cells. As a selective catalyst for Rac2 activation, P-Rex1 serves as an important regulator of human neutrophil NADPH oxidase activity and chemotaxis in response to a variety of extracellular stimuli. The exchange activity of P-Rex1 is synergistically activated by the binding of PIP3 and betagamma subunits of heterotrimeric G proteins in vitro, suggesting that the association of P-Rex1 with membranes is a prerequisite for cellular activation. However, the spatial regulation of endogenous P-Rex1 has not been well defined, particularly in human neutrophils activated through G protein-coupled receptors. Upon stimulation of neutrophil chemoattractant receptors, we observed that P-Rex1 translocated from cytoplasm to the leading edge of polarized cells in a G protein betagamma subunit- and PIP3-dependent manner, where it colocalized with F-actin and its substrate, Rac2. Redistribution of P-Rex1 to the leading edge was also dependent on tyrosine kinase activity and was modulated by cell adhesion. Furthermore, we observed that activation of cAMP-dependent protein kinase A (PKA), which phosphorylates and inactivates P-Rex1, inhibited its translocation. Our data indicate that endogenous P-Rex1 translocates to areas of Rac2 and cytoskeletal activation at the leading edge in response to chemoattractant stimuli in human neutrophils and that this translocation can be negatively modulated by activation of PKA and by cell adhesion.
authors.affiliation: Department of Immunology, IMM14, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: Tieming
authors.initials: T
authors.lastname: Zhao
authors.forename: Perihan
authors.initials: P
authors.lastname: Nalbant
authors.forename: Mikio
authors.initials: M
authors.lastname: Hoshino
authors.forename: Xuemei
authors.initials: X
authors.lastname: Dong
authors.forename: Dianqing
authors.initials: D
authors.lastname: Wu
authors.forename: Gary M
authors.initials: GM
authors.lastname: Bokoch
mesh_terms: D002448:Cell Adhesion; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D002630:Chemotactic Factors / Q000494:pharmacology*; D019204:GTP-Binding Proteins / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D006801:Humans; D009504:Neutrophils / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D021381:Protein Transport; D015398:Signal Transduction; D020744:rac GTP-Binding Proteins / Q000378:metabolism*; D000097766:RAC2 GTP-Binding Protein
chemical_list: D002630:Chemotactic Factors; D019204:GTP-Binding Proteins; D020662:Guanine Nucleotide Exchange Factors; D019869:Phosphatidylinositol 3-Kinases; D011494:Protein Kinases; D020744:rac GTP-Binding Proteins; D000097766:RAC2 GTP-Binding Protein; C453280:PREX1 protein, human