Relationship between arachidonate release and exocytosis in permeabilized human neutrophils stimulated with formylmethionyl-leucyl-phenylalanine (fMetLeuPhe), guanosine 5'-[gamma-thio]triphosphate (GTP[S]) and Ca2+.
The role of two G-proteins, Gp and Ge, in the stimulus-secretion pathway has been proposed on the basis of studies where GTP analogues have been introduced into permeabilized cell preparations. In this study, evidence is provided that two G-proteins are also involved when a receptor-directed agonist is used. Intact human neutrophils were made refractory to formylmethionyl-leucyl-phenylalanine (fMetLeuPhe) stimulation by metabolic inhibition and then permeabilized with streptolysin O to compare the intracellular requirements for exocytosis from specific and azurophilic granules and arachidonate release. In the presence of 1 microM-Ca2+ and 1 mM-MgATP, fMetLeuPhe or guanosine 5'-[gamma-thio]triphosphate (GTP[S]) induce secretion from both granule types as well as arachidonate release. Secretion and arachidonate release owing to fMetLeuPhe can occur in the absence of ATP, conditions under which G-protein-mediated activation of phospholipase C is suppressed. GTP[S]-induced secretion can also occur in the absence of MgATP, but GTP[S]-induced arachidonate release cannot. It is concluded that fMetLeuPhe, like GTP[S], stimulates secretion by interacting with another G-protein-mediated reaction apart from Gp. Evidence is provided that a possible target for the second G-protein-mediated reaction involved in fMetLeuPhe-induced secretion (but not GTP[S]-induced secretion) is phospholipase A2.
Cockcroft
S
S
Department of Physiology, University College London, U.K.
D000255:Adenosine Triphosphate / Q000494:pharmacology; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000097:blood*; D002118:Calcium / Q000494:pharmacology*; D002463:Cell Membrane Permeability; D005089:Exocytosis; D005966:Glucuronidase / Q000097:blood; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology*; D006801:Humans; D009113:Muramidase / Q000097:blood; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology*; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*
D001095:Arachidonic Acids; D016718:Arachidonic Acid; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D009240:N-Formylmethionine Leucyl-Phenylalanine; D000255:Adenosine Triphosphate; D009113:Muramidase; D005966:Glucuronidase; D002118:Calcium