Abstract
The p21-activated kinase-1 (PAK1) is best known for its role in the regulation of cytoskeletal and transcriptional signaling pathways. We show here in the microglia cell line Ra2 that PAK1 regulates NADPH oxidase (NOX-2) activity in a stimulus-specific manner. Thus, conditional expression of PAK1 dominant-positive mutants enhanced, whereas dominant-negative mutants inhibited, NADPH oxidase-mediated superoxide generation following formyl-methionyl-leucylphenylalanine or phorbol 12-myristate 13-acetate stimulation. Both Rac1 and the GTP exchange factor VAV1 were required as upstream signaling proteins in the formyl-methionyl-leucyl-phenylalanine-induced activation of endogenous PAK1. In contrast, PAK1 mutants had no effect on superoxide generation downstream of FcgammaR signaling during phagocytosis of IgG-immune complexes. We further present evidence that the effect of PAK1 on the respiratory burst is mediated through phosphorylation of p47(Phox), and we show that expression of a p47(Phox) (S303D/S304D/S320D) mutant, which mimics phosphorylation by PAK1, induced basal superoxide generation in vivo. In contrast PAK1 substrates LIMK-1 or RhoGDI are not likely to contribute to the PAK1 effect on NADPH oxidase activation. Collectively, our findings define a VAV1-Rac1-PAK1 signaling axis in mononuclear phagocytes regulating superoxide production in a stimulus-dependent manner.
Publication types
-
Research Support, N.I.H., Extramural
-
Research Support, Non-U.S. Gov't
MeSH terms
-
Amino Acid Substitution
-
Animals
-
Antigen-Antibody Complex / metabolism
-
Antigen-Antibody Complex / pharmacology
-
Carcinogens / pharmacology
-
Cell Line
-
Guanine Nucleotide Dissociation Inhibitors / genetics
-
Guanine Nucleotide Dissociation Inhibitors / metabolism
-
Humans
-
Lim Kinases / genetics
-
Lim Kinases / metabolism
-
Membrane Glycoproteins / genetics
-
Membrane Glycoproteins / metabolism*
-
Mice
-
Microglia / cytology
-
Microglia / metabolism
-
Mutation, Missense
-
N-Formylmethionine Leucyl-Phenylalanine / pharmacology
-
NADPH Oxidase 2
-
NADPH Oxidases / genetics
-
NADPH Oxidases / metabolism*
-
Neuropeptides / genetics
-
Neuropeptides / metabolism*
-
Phagocytes / metabolism
-
Proto-Oncogene Proteins c-vav / genetics
-
Proto-Oncogene Proteins c-vav / metabolism*
-
Receptors, IgG / genetics
-
Receptors, IgG / metabolism
-
Respiratory Burst
-
Signal Transduction / drug effects
-
Signal Transduction / physiology*
-
Superoxides / metabolism
-
Tetradecanoylphorbol Acetate / pharmacology
-
p21-Activated Kinases / genetics
-
p21-Activated Kinases / metabolism*
-
rac GTP-Binding Proteins / genetics
-
rac GTP-Binding Proteins / metabolism*
-
rac1 GTP-Binding Protein / genetics
-
rac1 GTP-Binding Protein / metabolism*
-
rho Guanine Nucleotide Dissociation Inhibitor alpha
-
rho-Specific Guanine Nucleotide Dissociation Inhibitors
Substances
-
ARHGDIA protein, human
-
Antigen-Antibody Complex
-
Carcinogens
-
Guanine Nucleotide Dissociation Inhibitors
-
Membrane Glycoproteins
-
Neuropeptides
-
Proto-Oncogene Proteins c-vav
-
RAC1 protein, human
-
Rac1 protein, mouse
-
Receptors, IgG
-
VAV1 protein, human
-
Vav1 protein, mouse
-
rho Guanine Nucleotide Dissociation Inhibitor alpha
-
rho-Specific Guanine Nucleotide Dissociation Inhibitors
-
Superoxides
-
N-Formylmethionine Leucyl-Phenylalanine
-
CYBB protein, human
-
Cybb protein, mouse
-
NADPH Oxidase 2
-
NADPH Oxidases
-
neutrophil cytosolic factor 1
-
LIMK1 protein, human
-
Lim Kinases
-
Limk1 protein, mouse
-
PAK1 protein, human
-
Pak1 protein, mouse
-
p21-Activated Kinases
-
rac GTP-Binding Proteins
-
rac1 GTP-Binding Protein
-
Tetradecanoylphorbol Acetate