8 research outputs found
Action of Pasteurella multocida toxin on G alpha(q) is persistent and independent of interaction with G-protein-coupled receptors
Modification of Heterotrimeric G-Proteins in Swiss 3T3 Cells Stimulated with <em>Pasteurella multocida</em> Toxin
<div><p>Many bacterial toxins covalently modify components of eukaryotic signalling pathways in a highly specific manner, and can be used as powerful tools to decipher the function of their molecular target(s). The <em>Pasteurella multocida</em> toxin (PMT) mediates its cellular effects through the activation of members of three of the four heterotrimeric G-protein families, G<sub>q</sub>, G<sub>12</sub> and G<sub>i</sub>. PMT has been shown by others to lead to the deamidation of recombinant Gα<sub>i</sub> at Gln-205 to inhibit its intrinsic GTPase activity. We have investigated modification of native Gα subunits mediated by PMT in Swiss 3T3 cells using 2-D gel electrophoresis and antibody detection. An acidic change in the isoelectric point was observed for the Gα subunit of the G<sub>q</sub> and G<sub>i</sub> families following PMT treatment of Swiss 3T3 cells, which is consistent with the deamidation of these Gα subunits. Surprisingly, PMT also induced a similar modification of Gα<sub>11</sub>, a member of the G<sub>q</sub> family of G-proteins that is not activated by PMT. Furthermore, an alkaline change in the isoelectric point of Gα<sub>13</sub> was observed following PMT treatment of cells, suggesting differential modification of this Gα subunit by PMT. G<sub>s</sub> was not affected by PMT treatment. Prolonged treatment with PMT led to a reduction in membrane-associated Gα<sub>i</sub>, but not Gα<sub>q</sub>. We also show that PMT inhibits the GTPase activity of G<sub>q</sub>.</p> </div