Chemoattractant-stimulated GTPase activity is decreased on membranes from polymorphonuclear leukocytes incubated in chemoattractant.
Polymorphonuclear leukocytes, PMNs, incubated in a chemoattractant undergo a time-dependent decrease in responsiveness to the chemoattractant; i.e. they desensitize or adapt. We have examined the role of ligand-induced changes at early steps in signal transduction for adaptation of PMNs to chemoattractants. The chemoattractant stimulation of a pertussis toxin-sensitive GTPase activity on PMN membranes was used as an assay of signal transduction. We find a decreased basal GTPase activity and a decrease in the ability of N-formylnorleucylleucylphenylalanine (FN-LLP) to stimulate this activity on membranes prepared from PMNs incubated with the chemotactic peptide FNLLP. The basal GTPase activity is decreased by up to 70% and the peptide-stimulated GTPase activity by up to 95% on membranes from PMNs incubated for 20 min at 37 degrees C in 10(-7) M FNLLP. The decrease in peptide-stimulated GTPase activity cannot be accounted for by the decreased number of FNLLP receptors on the membranes. Rather, receptors that remain available for binding stimulate the GTPase activity with a decreased efficiency. The ligand-induced change in GTPase activity is not stimulus specific. GTPase activity stimulated by both C5a and LTB4 was decreased on membranes from PMNs incubated in FNLLP. The decrease in chemoattractant-stimulated GTPase activity is partially reversed if cells are subsequently incubated at 37 degrees C in the absence of peptide prior to membrane preparation. We detected no quantitative or qualitative change in either pertussis toxin substrates or immunoreactive G proteins when membranes from control and FNLLP-treated cells were compared.
Wilde
M W
MW
Department of Biology, University of Pennsylvania, Philadelphia 19104-6018.
Carlson
K E
KE
Manning
D R
DR
Zigmond
S H
SH
D000818:Animals; D002462:Cell Membrane / Q000201:enzymology; D002634:Chemotaxis, Leukocyte; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D007700:Kinetics; D009504:Neutrophils / Q000187:drug effects / Q000201:enzymology*; D009842:Oligopeptides / Q000494:pharmacology*; D037342:Pertussis Toxin; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D011817:Rabbits; D015398:Signal Transduction; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D009842:Oligopeptides; D010566:Virulence Factors, Bordetella; C024998:N-formylnorleucyl-leucyl-4-phenylalanine; D037342:Pertussis Toxin; D010744:Phosphoric Monoester Hydrolases; D020558:GTP Phosphohydrolases