Action of Pasteurella multocida toxin on Galpha(q) is persistent and independent of interaction with G-protein-coupled receptors.
Pasteurella multocida toxin (PMT) activates Galpha(q) and facilitates stimulation of inositol phosphate accumulation induced by agonists via G(q)-coupled membrane receptors. Here, we studied the effects of PMT on agonist-induced GTPgammaS binding to G(q) in cell membranes and a role of G-protein-coupled receptors in the action of PMT. Pre-treatment of Swiss 3T3 cells with PMT increased bombesin or vasopressin-induced GTPgammaS-binding in cell membranes by about 50 to 150%. Increase in agonist-stimulated GTPgammaS-binding caused by PMT pretreatment was specific for Galpha(q) and not observed with Galpha(11). PMT-induced effects on GTPgammaS-binding were persistent after removing the toxin or in the presence of anti-PMT antibody. Stimulation of agonist-induced GTPgammaS-binding by PMT was independent of phosphorylation of the C-terminal tyrosine356 of Galpha(q). Activation of phospholipase C by PMT occurred via Galpha(q) which was fused to the alpha(1b)-adrenoceptor and also with a C-terminally deleted Galpha(q), which is not able to interact with G protein-coupled membrane receptors. The data indicate that activation of Galpha(q) by PMT is persistent and independent of a functional interaction of G(q) with G-protein-coupled receptors.
Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Albert-Ludwigs-Universität Freiburg, Albertstrasse 25, D-79104 Freiburg, Germany.
Joachim H C
JH
Orth
Simona
S
Lang
Inga
I
Preuss
Graeme
G
Milligan
Klaus
K
Aktories
D000818:Animals; D001426:Bacterial Proteins / Q000494:pharmacology*; D001427:Bacterial Toxins / Q000494:pharmacology*; D001839:Bombesin / Q000494:pharmacology; D002460:Cell Line; D004357:Drug Synergism; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006801:Humans; D051379:Mice; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*; D041701:Swiss 3T3 Cells; D014667:Vasopressins / Q000494:pharmacology
D001426:Bacterial Proteins; D001427:Bacterial Toxins; C062258:Pasteurella multocida toxin; D043562:Receptors, G-Protein-Coupled; D014667:Vasopressins; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D001839:Bombesin