TNF-alpha stimulates increased plasma membrane guanine nucleotide binding protein activity in polymorphonuclear leukocytes.
TNF-alpha enhances the response of polymorphonuclear leukocytes (PMN) to chemoattractants: however, the mechanism by which this occurs is unclear. We addressed the hypothesis that TNF-alpha enhances the PMN response to chemoattractants by increasing chemoattractant receptor transmembrane signaling, using fMLP as the model chemoattractant. fMLP-stimulated guanine nucleotide binding (G) protein activation was significantly increased in plasma membranes isolated from PMNs exposed to TNF-alpha 100 U/ml for 10 minutes (TNF-M), compared to membranes from control cells (CM). Formyl peptide receptor number and affinity were not significantly different in CM and TNF-M. Gi and Gs content were increased in TNF-M as measured by pertussis toxin and cholera toxin (CT) catalyzed ADP-ribosylation, respectively. The increased Gi was coupled to the formyl peptide receptor as shown by receptor-specific CT labeling of Gi. Immunoblot analysis showed that both G alpha i2 and G alpha 3 were increased in TNF-M. The functional activity of the increased G protein content was demonstrated by increased NaF-stimulated phospholipase D activity in TNF-alpha-treated PMNs. We conclude that TNF-alpha rapidly stimulates increased PMN plasma membrane expression of G proteins that couple formyl peptide receptors to effector enzymes. Regulation of G protein expression may be a significant mechanism by which TNF regulates PMN function.
Klein
J B
JB
Department of Medicine, University of Louisville Health Sciences Center, Kentucky 40292.
Scherzer
J A
JA
Harding
G
G
Jacobs
A A
AA
McLeish
K R
KR
D002462:Cell Membrane / Q000378:metabolism; D002772:Cholera Toxin / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D005459:Fluorides / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006150:Guanine Nucleotides / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D009504:Neutrophils / Q000378:metabolism*; D037342:Pertussis Toxin; D010739:Phospholipase D / Q000378:metabolism; D044042:Receptors, Formyl Peptide; D011971:Receptors, Immunologic / Q000378:metabolism*; D018000:Receptors, Peptide / Q000378:metabolism*; D015398:Signal Transduction; D013481:Superoxides / Q000378:metabolism; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D010566:Virulence Factors, Bordetella / Q000378:metabolism
D006150:Guanine Nucleotides; D044042:Receptors, Formyl Peptide; D011971:Receptors, Immunologic; D018000:Receptors, Peptide; D014409:Tumor Necrosis Factor-alpha; D010566:Virulence Factors, Bordetella; D013481:Superoxides; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D002772:Cholera Toxin; D037342:Pertussis Toxin; D010739:Phospholipase D; D019204:GTP-Binding Proteins; D005459:Fluorides