Meza Ulises, Thapliyal Ashish, Bannister Roger A, Adams Brett A
Department of Biology, Utah State University, 5305 Old Main Hill, Logan, UT 84322, USA.
Mol Pharmacol. 2007 Jan;71(1):284-93. doi: 10.1124/mol.106.028530. Epub 2006 Oct 18.
Neurokinin (NK) 1 receptors and CaV2.3 calcium channels are both expressed in nociceptive neurons, and mice lacking either protein display altered responses to noxious stimuli. Here, we examined modulation of CaV2.3 through NK1 receptors expressed in human embryonic kidney 293 cells. We find that NK1 receptors generate complex modulation of CaV2.3. In particular, weak activation of these receptors evokes mainly stimulation of CaV2.3, whereas strong receptor activation elicits profound inhibition that overlaps with channel stimulation. Unlike R-type channels encoded by CaV2.3, L-type (CaV1.3), N-type (CaV2.2), and P/Q-type (CaV2.1) channels are inhibited, but not stimulated, through NK1 receptors. Pharmacological experiments show that protein kinase C (PKC) mediates stimulation of CaV2.3 through NK1 receptors. The signaling mechanisms underlying inhibition were explored by expressing proteins that buffer either Galpha(q/11) (regulator of G protein signaling protein 3T and carboxyl-terminal region of phospholipase C-beta1) or Gbeta gamma subunits (transducin and the carboxyl-terminal region of bovine G-protein-coupled receptor kinase). A fast component of inhibition was attenuated by buffering Gbeta gamma, whereas a slow component of inhibition was reduced by buffering Galpha(q/11). When both Gbeta gamma and Galpha(q/11) were simultaneously buffered in the same cells, inhibition was virtually eliminated, but receptor activation still triggered substantial stimulation of CaV2.3. We also report that NK1 receptors accelerate the inactivation kinetics of CaV2.3 currents. Altogether, our results indicate that NK1 receptors modulate CaV2.3 using three different signaling mechanisms: a fast inhibition mediated by Gbeta gamma, a slow inhibition mediated by Galpha(q/11), and a slow stimulation mediated by PKC. This new information concerning R-type calcium channels and NK1 receptors may help in understanding nociception, synaptic plasticity, and other physiological processes.
神经激肽（NK）1受体和CaV2.3钙通道均在伤害性神经元中表达，缺乏这两种蛋白的小鼠对伤害性刺激的反应均发生改变。在此，我们研究了通过人胚肾293细胞中表达的NK1受体对CaV2.3的调节作用。我们发现NK1受体对CaV2.3产生复杂的调节作用。具体而言，这些受体的弱激活主要引起CaV2.3的刺激，而强受体激活则引发与通道刺激重叠的深度抑制。与由CaV2.3编码的R型通道不同，L型（CaV1.3）、N型（CaV2.2）和P/Q型（CaV2.1）通道通过NK1受体被抑制而非刺激。药理学实验表明，蛋白激酶C（PKC）介导通过NK1受体对CaV2.3的刺激。通过表达缓冲Gα(q/11)（G蛋白信号调节蛋白3T和磷脂酶C-β1的羧基末端区域）或Gβγ亚基（转导蛋白和牛G蛋白偶联受体激酶的羧基末端区域）的蛋白来探索抑制的信号传导机制。通过缓冲Gβγ可减弱抑制的快速成分，而通过缓冲Gα(q/11)可减少抑制的缓慢成分。当在同一细胞中同时缓冲Gβγ和Gα(q/11)时，抑制几乎消除，但受体激活仍引发CaV2.3的大量刺激。我们还报告NK1受体加速CaV2.3电流的失活动力学。总之，我们的结果表明NK1受体使用三种不同的信号传导机制调节CaV2.3：由Gβγ介导的快速抑制、由Gα(q/11)介导的缓慢抑制以及由PKC介导的缓慢刺激。关于R型钙通道和NK1受体的这一新信息可能有助于理解伤害感受、突触可塑性和其他生理过程。
