A interacting protein specific to alpha-1 adrenoceptor modifies the receptor's function

蛋白质与蛋白质之间的相互作用是受体生物学的主题之一。我们假设α_<1A>-肾上腺素受体（α_<1A>-AR）在天然组织中伴随着一种调节受体功能的相互作用蛋白。为了分离与α_<1A>-AR相互作用的候选蛋白，我们以α_<1A>-AR受体为诱饵，采用酵母双杂交法检索人脑cDNA文库。结果，确定了SNARE复合体的结合伙伴Snapin。在PC12细胞的质膜上，Snapin与α_<1A>-AR相互作用并共定位。此外，我们发现在PC12细胞中，当Snapin与α_<1A>-AR共表达时，α_<1A>-AR激活时钙的进入明显增加。另一方面，Snapin与TRPC6通道相互作用，现在认为TRPC6通道是受体操作的钙通道之一。α_<1A>-AR的激活诱导了受体之间的相互作用，增加了TRPC6向细胞表面的募集。我们的数据提示了一种新的受体操作的信号机制，其中Snapin将α_<1A>-AR连接到TRPC6，通过受体操作的钙通道增强钙内流。

Protein-to-protein interaction is one of the topics in receptor biology. We hypothesized that the α_<1A>-adrenoceptor (α_<1A>-AR) is accompanied with an interacting protein which modulates a receptor's function in native tissues. To isolate candidate proteins interacting with α_<1A>-AR, we searched human brain cDNA library by yeast two-hybrid method using the receptor as bait. As a result, Snapin, known as a binding partner of SNARE complex was identified. Snapin interacts and co-localizes with the α_<1A>-AR on plasma membrane of PC12 cells. Additionally, we found that the calcium entry upon α_<1A>-AR activation was significantly augmented when Snapin was co-expressed with the α_<1A>-AR in PC12 cells. On the other hand, Snapin interacts with TRPC6 channel which is now believed to be one of the receptor-operated calcium channels. Activation of the α_<1A>-AR induced the interaction between the receptor, increasing the recruitment of TRPC6 to the cell surface. Our data suggest a new receptor-operated signaling mechanism, where Snapin links the α_<1A>-AR to TRPC6, augmented calcium influx via receptor-operated calcium channels.