Chemoattractant receptor-specific differences in G protein activation rates regulate effector enzyme and functional responses.
The hypothesis that disparate neutrophil functional responses to various chemoattractants are regulated by receptor-specific rates of G protein activation was examined in HL-60 granulocytes. The initial rates of G protein activation and the affinity of receptor-stimulated G proteins for GTP gamma S in HL-60 membranes stimulated by fMet-Leu-Phe, C5a, and leukotriene B4 (LTB4) differed significantly among the chemoattractants, with a rank order of fMet-Leu-Phe > C5a > LTB4. Equilibrium GTP gamma S binding showed that all three chemoattractants activated a common pool of G proteins. Stimulation of phospholipase D activation, measured as phosphatidylethanol generation, and superoxide release in intact cells also occurred with a rank order of fMet-Leu-Phe > C5a > LTB4. On the other hand, the rank order of receptor affinities for ligand and of the EC50 of chemoattractant stimulation of GTP gamma S binding was C5a > LTB4 > fMet-Leu-Phe. C5a and LTB4 receptor densities were similar but were less than formyl peptide receptor density. Graded pertussis toxin treatment proportionally reduced superoxide release and phospholipase D activation to all three chemoattractants. The results suggest that receptor-specific differences in G protein affinity for guanine nucleotides lead to different rates of guanine nucleotide exchange and, thereby, contribute to disparate effector enzyme and functional responses.
Jacobs
A A
AA
Department of Medicine, University of Louisville, KY 40292, USA.
Huber
J L
JL
Ward
R A
RA
Klein
J B
JB
McLeish
K R
KR
D000595:Amino Acid Sequence; D002630:Chemotactic Factors / Q000378:metabolism / Q000494:pharmacology; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D006098:Granulocytes / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D007951:Leukemia, Myeloid; D008969:Molecular Sequence Data; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000378:metabolism / Q000494:pharmacology; D010739:Phospholipase D / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D044042:Receptors, Formyl Peptide; D011971:Receptors, Immunologic / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D018000:Receptors, Peptide / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D013268:Stimulation, Chemical; D013379:Substrate Specificity
D002630:Chemotactic Factors; D044042:Receptors, Formyl Peptide; D011971:Receptors, Immunologic; D018000:Receptors, Peptide; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D009240:N-Formylmethionine Leucyl-Phenylalanine; D010739:Phospholipase D; D019204:GTP-Binding Proteins