Inhibition of pertussis toxin catalyzed ADP-ribosylation of G-proteins by membrane depolarization in rat brain synaptoneurosomes.
Rat brainstem synaptoneurosomes at resting and depolarization potentials were subjected to ADP-ribosylation in the presence of pertussis toxin (PTX). Subsequent [32P]ADP-ribosylation of synaptoneurosomal membranes revealed labeling of a 39-kDa protein band which reacted with antibodies to the alpha-subunit of G-proteins, mainly Go. ADP-ribosylation of the G-proteins was completely achieved in synaptoneurosomes at resting potential ( [K+] = 4.7 mM). In the depolarized synaptoneurosomes, however, the higher the membrane potential the lower the extent of ADP-ribosylation achieved (46% and 11% in K+ concentrations of 50 and 100 mM, respectively). A similar effect of membrane depolarization on PTX-catalyzed ADP-ribosylation was expressed in the functional coupling between G-protein activation and changes induced in the muscarinic receptor affinity. These findings may indicate a depolarization-induced inhibition of PTX-catalyzed ADP-ribosylation of G-proteins.
Cohen-Armon
M
M
Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Israel.
Sokolovsky
M
M
D000109:Acetylcholine / Q000378:metabolism; D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000818:Animals; D001345:Autoradiography; D001933:Brain Stem / Q000502:physiology; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009243:NAD / Q000378:metabolism*; D037342:Pertussis Toxin; D010761:Phosphorus Radioisotopes; D051381:Rats; D011919:Rats, Inbred Strains; D011976:Receptors, Muscarinic / Q000378:metabolism; D013574:Synaptosomes / Q000187:drug effects / Q000502:physiology*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
D010761:Phosphorus Radioisotopes; D011976:Receptors, Muscarinic; D010566:Virulence Factors, Bordetella; D009243:NAD; D000246:Adenosine Diphosphate Ribose; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D000109:Acetylcholine