title: Do porins inhibit the macrophage phagocyting activity by stimulating the adenylate cyclase?
abstract: Porins interact with macrophage membranes and inhibit their phagocyting activity. We have tested the porin effect on a biologically relevant membrane-bound enzymic activity, the adenylate cyclase system, which appears to be stimulated both in the presence of Mn2+ and Mg2+ or Mg2+ + Gpp(NH)p. Moreover, for mice macrophages incubated in the presence of porins, there is an increase in the intracellular cAMP content after 5 min of incubation, with a maximum after 15 min of incubation. The results shown suggest that the porin effects on the adenylate cyclase can represent the molecular basis of the porin-dependent inhibition of the macrophages phagocytosis. Our point of view, which proposes a cAMP role in inhibiting the phagocyting activity in macrophages, is supported also by the results of the experiments carried out in the presence of both dibutyryl-cAMP or aminophylline. The phagocyting activity is inhibited in all cases and independently of the bacteria to be phagocyted.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism*; D000628:Aminophylline / Q000494:pharmacology; D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000302:isolation & purification / Q000494:pharmacology*; D003994:Bucladesine / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D007473:Ion Channels / Q000502:physiology; D007700:Kinetics; D008264:Macrophages / Q000201:enzymology / Q000502:physiology*; D008274:Magnesium / Q000494:pharmacology; D051379:Mice; D010587:Phagocytosis / Q000187:drug effects*; D018272:Porins
chemical_list: D001425:Bacterial Outer Membrane Proteins; D007473:Ion Channels; D018272:Porins; D000628:Aminophylline; D006165:Guanylyl Imidodiphosphate; D003994:Bucladesine; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D008274:Magnesium