Multiple signaling pathways control stimulus-secretion coupling in rat peritoneal mast cells.
Fura-2 and membrane capacitance measurements were performed to investigate intracellular Ca2+ concentration [( Ca2+]i) and secretory responses of rat peritoneal mast cells following secretagogue stimulation. Compound 48/80 and internally applied guanosine 5'-[gamma-thio]triphosphate (GTP[gamma-S]) induced transient rises in [Ca2+]i and caused membrane capacitance increases as secretion occurred. The 48/80-induced Ca2+ transients and secretory responses were blocked by guanosine 5'-[beta-thio]diphosphate and neomycin, indicating that inositolphospholipid breakdown mediated by guanine nucleotide-binding regulatory protein (G protein) plays an important role in stimulus-secretion coupling. However, pertussis toxin did not block Ca2+ transients induced by 48/80 or GTP[gamma-S], whereas secretory responses were either abolished (48/80) or developed only after a considerable delay (GTP[gamma-S]). Similar effects were obtained by perfusing cells with cAMP: (i) Ca2+ transients following stimulation with 48/80 remained unaffected by cAMP, but secretory responses were abolished; (ii) GTP[gamma-S] induced normal Ca2+ transients and degranulation in the presence of cAMP. Pretreatment of mast cells with phorbol 12-myristate 13-acetate (PMA) abolished 48/80- and GTP[gamma-S]-induced Ca2+ transients (but not inositol trisphosphate-induced Ca2+ transients), whereas secretion still occurred. At the same time, the Ca2+ requirement for secretion was reduced by PMA. These results indicate that secretion in mast cells is under control of an as yet unidentified signaling pathway that involves a G protein. This pathway is distinct from inositolphospholipid turnover and may provide the triggering mechanism for secretion, whereas the inositolphospholipid pathway serves to increase [Ca2+]i and renders the secretory process more sensitive to [Ca2+]i by activating protein kinase C. Persistent activation of protein kinase C through phorbol ester imposes negative feedback control on the inositolphospholipid pathway, whereas cAMP may inhibit the unidentified signaling pathway.
Penner
R
R
Max-Planck-Institut für Biophysikalische Chemie, Göttingen, Federal Republic of Germany.
D000818:Animals; D001572:Benzofurans; D002118:Calcium / Q000378:metabolism; D016257:Fura-2; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism; D008407:Mast Cells / Q000502:physiology*; D008954:Models, Biological; D009355:Neomycin / Q000494:pharmacology; D010537:Peritoneum / Q000166:cytology*; D037342:Pertussis Toxin; D051381:Rats; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013873:Thionucleotides / Q000378:metabolism / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology; D003189:p-Methoxy-N-methylphenethylamine / Q000494:pharmacology
D001572:Benzofurans; D013873:Thionucleotides; D010566:Virulence Factors, Bordetella; D006153:Guanosine Diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D003189:p-Methoxy-N-methylphenethylamine; C023427:guanosine 5'-O-(2-thiodiphosphate); D006160:Guanosine Triphosphate; D037342:Pertussis Toxin; D009355:Neomycin; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium; D016257:Fura-2