Pannexin-1 (Panx1) forms plasma membrane channels that allow the exchange of small molecules between the intracellular and extracellular compartments, and are involved in diverse physiological and pathological responses in the nervous system. However, the signaling mechanisms that induce their opening still remain elusive. Here, we propose a new mechanism for Panx1 channel activation through a functional crosstalk with the highly Ca²⁺ permeable α7 nicotinic acetylcholine receptor (nAChR). Consistent with this hypothesis, we found that activation of α7 nAChRs induces Panx1-mediated dye uptake and ATP release in the neuroblastoma cell line SH-SY5Y-α7. Using membrane permeant Ca²⁺ chelators, total internal reflection fluorescence microscopy in SH-SY5Y-α7 cells expressing a membrane-tethered GCAMP3, and Src kinase inhibitors, we further demonstrated that Panx1 channel opening depends on Ca²⁺ signals localized in submembrane areas, as well as on Src kinases. In turn, Panx1 channels amplify cytosolic Ca²⁺ signals induced by the activation of α7 nAChRs, by a mechanism that seems to involve ATP release and P2X7 receptor activation, as hydrolysis of extracellular ATP with apyrase or blockage of P2X7 receptors with oxidized ATP significantly reduces the α7 nAChR-Ca²⁺ signal. The physiological relevance of this crosstalk was also demonstrated in neuroendocrine chromaffin cells, wherein Panx1 channels and P2X7 receptors contribute to the exocytotic release of catecholamines triggered by α7 nAChRs, as measured by amperometry. Together these findings point to a functional coupling between α7 nAChRs, Panx1 channels and P2X7 receptors with physiological relevance in neurosecretion.

中文翻译：

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α7 烟碱乙酰胆碱受体、pannexin-1 通道和 P2X7 受体之间的相互作用引起嗜铬细胞的胞吐作用

Pannexin-1 (Panx1) 形成质膜通道，允许细胞内和细胞外区室之间的小分子交换，并参与神经系统中的各种生理和病理反应。然而，诱导它们开放的信号机制仍然难以捉摸。在这里，我们提出了一种通过与高 Ca ²⁺渗透性 α7 烟碱乙酰胆碱受体 (nAChR)的功能性串扰来激活 Panx1 通道的新机制。与这一假设一致，我们发现 α7 nAChRs 的激活诱导了神经母细胞瘤细胞系 SH-SY5Y-α7 中 Panx1 介导的染料摄取和 ATP 释放。使用膜渗透剂 Ca ²⁺螯合剂、表达膜系留 GCAMP3 的 SH-SY5Y-α7 细胞中的全内反射荧光显微镜和 Src 激酶抑制剂，我们进一步证明 Panx1 通道的开放依赖于位于亚膜区域的Ca ²⁺信号，以及 Src 激酶. 反过来，Panx1 通道放大由 α7 nAChR 激活诱导的胞质 Ca ²⁺信号，其机制似乎涉及 ATP 释放和 P2X7 受体激活，因为胞外 ATP 用腺苷三磷酸双磷酸酶水解或用氧化 ATP 阻断 P2X7 受体显着降低α7 nAChR-Ca ²⁺信号。这种串扰的生理相关性也在神经内分泌嗜铬细胞中得到证实，其中 Panx1 通道和 P2X7 受体有助于由 α7 nAChRs 触发的儿茶酚胺的胞吐释放，如通过电流测定法测量的。这些发现共同表明 α7 nAChR、Panx1 通道和 P2X7 受体之间的功能耦合与神经分泌的生理相关。