Wolfson Centre for Age Related Diseases, King's College London, Guy's Campus, London SE1 1UL, UK.
Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK.
Neuropharmacology. 2014 Feb;77:9-18. doi: 10.1016/j.neuropharm.2013.09.005. Epub 2013 Sep 18.
Pasteurella multocida toxin (PMT) activates the G-proteins Gαi(₁₋₃), Gα(q), Gα₁₁, Gα₁₂ and Gα₁₃ by deamidation of specific glutamine residues. A number of these alpha subunits have signalling roles in neurones. Hence we studied the action of this toxin on rat superior cervical ganglion (SCG) neurones and NG108-15 neuronal cells. Both Gα(q) and Gα₁₁ could be identified in SCGs with immunocytochemistry. PMT had no direct action on Kv7 or Cav2 channels in SCGs. However PMT treatment enhanced muscarinic receptor mediated inhibition of M-current (Kv7.2 + 7. 3) as measured by a 19-fold leftward shift in the oxotremorine-M concentration-inhibition curve. Agonists of other receptors, such as bradykinin or angiotensin, that inhibit M-current did not produce this effect. However the amount of PIP₂ hydrolysis could be enhanced by PMT for all three agonists. In a transduction system in SCGs that is unlikely to be affected by PMT, Go mediated inhibition of calcium current, PMT was ineffective whereas the response was blocked by pertussis toxin as expected. M1 muscarinic receptor evoked calcium mobilisation in transformed NG108-15 cells was enhanced by PMT. The calcium rises evoked by uridine triphosphate acting on endogenous P2Y₂ receptors in NG108-15 cells were enhanced by PMT. The time and concentration dependence of the PMT effect was different for the resting calcium compared to the calcium rise produced by activation of P2Y₂ receptors. PMT's action on these neuronal cells would suggest that if it got into the brain, symptoms of a hyperexcitable nature would be seen, such as seizures.
多杀巴斯德菌毒素（PMT）通过脱酰胺特定谷氨酰胺残基激活 G 蛋白 Gαi(₁₋₃)、Gα(q)、Gα₁₁、Gα₁₂和 Gα₁₃。这些α亚基中的许多在神经元中具有信号作用。因此，我们研究了这种毒素对大鼠颈上神经节（SCG）神经元和 NG108-15 神经元细胞的作用。免疫细胞化学可鉴定出 SCG 中的 Gα(q)和 Gα₁₁。PMT 对 SCG 中的 Kv7 或 Cav2 通道没有直接作用。然而，PMT 处理增强了毒蕈碱受体介导的 M 电流（Kv7.2 + 7.3）抑制作用，表现为 oxotremorine-M 浓度-抑制曲线向左移动 19 倍。激动其他受体（如缓激肽或血管紧张素），抑制 M 电流的激动剂不会产生这种效应。然而，PMT 可以增强所有三种激动剂的 PIP₂ 水解量。在 SCG 中的一种不太可能受到 PMT 影响的转导系统中，Go 介导的钙电流抑制，PMT 无效，而如预期的那样，百日咳毒素阻断了这种反应。PMT 增强了转化的 NG108-15 细胞中 M1 毒蕈碱受体引发的钙动员。PMT 增强了 NG108-15 细胞中内源性 P2Y₂ 受体激活引起的三磷酸尿苷引起的钙上升。与激活 P2Y₂ 受体引起的钙上升相比，PMT 对静息钙的作用的时间和浓度依赖性不同。PMT 对这些神经元细胞的作用表明，如果它进入大脑，可能会出现兴奋性过高的症状，如癫痫发作。
