CHEMOATTRACTION OF NEUTROPHILS BY SUBSTANCE-P AND TRANSFORMING GROWTH-FACTOR-BETA-1 IS INADEQUATELY EXPLAINED BY CURRENT MODELS OF LIPID REMODELING

'Classical'' chemoattractants, such as FMLP, C5a, or leukotriene B4, n ot only elicit directed motility but activate neutrophils (degranulati on, release of active oxygen species). Signal transduction after ligat ion of receptors for these classical chemoattractants is mediated by p ertussis toxin (PT)-sensitive, heterotrimeric G proteins and the early production of lipid messengers via phospholipases. In contrast, we ha ve previously shown that substance P (SP) and transforming growth fact or-beta1 (TGF-beta1) are ''pure'' chemoattractants in that they elicit chemotaxis without activating neutrophils. Paradoxically, pure chemoa ttractants also activate G proteins (plasmalemmal GTPase activity) wit hout eliciting increments in cytosolic calcium ([Ca]i) and thus inosit ol trisphosphate. We therefore determined lipid remodeling and signal transduction in response to pure chemoattractants. Increments in plasm alemmal GTPase activated by SP (0.1 muM) and TGF-beta1 (40 fM), like t hat after FMLP, were PT-sensitive (SP = 6.6 +/- 2 pm/mg/min vs SP + PT = 1.1 +/- 0.9 over basal activity; TGF-beta1 = 4.3 +/- 1.6 vs TGF-bet a1 + PT = 2.3 +/- 0.9). In parallel, treatment of PMN with PT (1 mug/m l, 30 min) inhibited chemotaxis (under agarose) after FMLP (2175 +/- 1 76 (SEM) mum vs 726 +/- 267) and SP (411 +/- 99 pm vs 103 +/- 62 pm) a nd TGF-beta1 (40 fM, 375 +/- 53 mum vs 83 +/- 47). However, G proteins coupled to receptors for SP and TGF-beta1, unlike FMLP, did not appea r to be linked to phospholipases in that neither increments in diacylg lycerol were detected after receptor ligation (FMLP = 152 +/- 22% rest ing levels; SP = 101 +/- 5%; TGF-beta1 = 105 +/- 4%) nor was alkylacyl glycerol increased by exposure to SP or TGF-beta1 (SP = 92 +/- 4%; TGF -beta1 = 101 +/- 8%; FMLP = 226 +/- 40%). Moreover, polymorphonuclear leukocytes failed to generate phosphatidates (PA) of either species af ter SP (DA-PA = 79 +/- 9% resting at 60 s; EA-PA = 103 +/- 4%) or TGF- beta1 (DA-PA = 101 +/- 5%; EA-PA = 98 +/- 9%) in contrast to FMLP (DA- PA = 155 +/- 22%; EA-PA = 149 +/- 16%). The data clearly contravene th e current dogma that all chemoattractants use inositol trisphosphate a nd diglycerides as intracellular signals and suggest the presence of a unique subset of PT-sensitive G proteins, not coupled to ''classical' ' phospholipases, transduce chemoattraction.