Regulation of Ca²⁺ homeostasis is essential for neuronal function and its survival. Recent data suggest that TRPC1 function as the endogenous store-mediated Ca²⁺ entry channel in dopaminergic cells, and loss of TRPC1 function leads to neurodegeneration; however, its regulation is not fully identified. Here we provide evidence that the sigma 1 receptor contributes to the loss of dopaminergic cells by blocking TRPC1-mediated Ca²⁺ entry. Importantly, downregulation of sigma 1 receptor expression significantly decreased neurotoxin-induced loss of dopaminergic cells as measured by MTT assays and caspase activity was also inhibited. Importantly, sigma 1 receptor inhibited TRPC1-mediated Ca²⁺ entry and silencing of sigma 1 receptor significantly restored store-dependent Ca²⁺ influx. Although co-immunoprecipitation failed to show an interaction between the TRPC1 and sigma 1 receptor, store depletion promoted a decrease in the sigma 1 receptor-STIM1 association. Neurotoxin-induced loss of Ca²⁺ entry was significantly restored in cells that had decreased sigma 1 receptor expression. Furthermore, TRPC1 or STIM1 silencing inhibited store-mediated Ca²⁺ entry, which was further increased upon the downregulation of the sigma 1 receptor expression. TRPC1 silencing prevented the increased neuroprotection and caspase activity observed upon the downregulation of sigma 1 receptor. Finally, sigma 1 receptor activation also significantly decreased TRPC1-mediated Ca²⁺ entry and lead to an increase in neurodegeneration. In contrast, addition of sigma 1 receptor antagonist prevented neurotoxin-induced neurodegeneration and facilitated TRPC1-mediated Ca²⁺ influx. Together these results suggest that the sigma 1 receptor is involved in the inhibition of TRPC1- mediated Ca²⁺ entry, which leads to the degeneration in the dopaminergic cells, and prevention of sigma 1 receptor function could protect neuronal cell death as observed in Parkinson’s disease.

Ca ²⁺稳态的调节对于神经元功能及其生存至关重要。最近的数据表明，TRPC1 在多巴胺能细胞中充当内源性存储介导的 Ca ²⁺进入通道，TRPC1 功能的丧失会导致神经变性。然而，其监管尚未完全确定。在这里，我们提供的证据表明，sigma 1 受体通过阻断 TRPC1 介导的 Ca ²⁺进入而导致多巴胺能细胞的损失。重要的是，通过 MTT 测定测量，sigma 1 受体表达下调显着减少了神经毒素诱导的多巴胺能细胞损失，并且 caspase 活性也受到抑制。重要的是，sigma 1 受体抑制 TRPC1 介导的 Ca ²⁺进入，并且 sigma 1 受体的沉默显着恢复了储存依赖性 Ca ²⁺流入。尽管免疫共沉淀未能显示 TRPC1 和 sigma 1 受体之间的相互作用，但储存耗尽促进了 sigma 1 受体-STIM1 关联的减少。在 sigma 1 受体表达降低的细胞中，神经毒素诱导的 Ca ²⁺进入丧失显着恢复。此外，TRPC1 或 STIM1 沉默抑制了钙池介导的 Ca ²⁺内流，这种作用在 sigma 1 受体表达下调后进一步增加。 TRPC1 沉默阻止了在 sigma 1 受体下调时观察到的神经保护和 caspase 活性的增加。最后，sigma 1 受体激活还显着减少 TRPC1 介导的 Ca ²⁺进入，并导致神经变性增加。 相反，添加 sigma 1 受体拮抗剂可防止神经毒素诱导的神经变性并促进 TRPC1 介导的 Ca ²⁺流入。这些结果共同表明，sigma 1 受体参与抑制 TRPC1 介导的 Ca ²⁺进入，从而导致多巴胺能细胞变性，并且预防 sigma 1 受体功能可以保护神经元细胞死亡，如帕金森病中观察到的那样。