Mitochondrial-associated endoplasmic reticulum (ER) membranes (MAMs) play a key role in several physiological functions, including calcium ion (Ca²⁺) transfer and autophagy; however, the molecular mechanism controlling this interaction in cadmium (Cd)-induced neurotoxicity is unknown. This study shows that Cd induces alterations in MAMs and mitochondrial Ca²⁺ levels in PC12 cells and primary neurons. Ablation or silencing of mitofusin 2 (Mfn2) in PC12 cells or primary neurons blocks the colocalization of ER and mitochondria while reducing the efficiency of mitochondrial Ca²⁺ uptake. Moreover, Mfn2 defects reduce interactions or colocalization between GRP75 and VDAC1. Interestingly, the enhancement of autophagic protein levels, colocalization of LC3 and Lamp2, and GFP-LC3 puncta induced by Cd decreased in Mfn2^−/− or Grp75^−/− PC12 cells and Mfn2- or Grp75-silenced primary neurons. Notably, the specific Ca²⁺ uniporter inhibitor RuR blocked both mitochondrial Ca²⁺ uptake and autophagy induced by Cd. Finally, this study proves that the mechanism by which IP3R-Grp75-VDAC1 tethers in MAMs is associated with the regulation of autophagy by Mfn2 and involves their role in mediating mitochondrial Ca²⁺ uptake from ER stores. These results give new evidence into the organelle metabolic process by demonstrating that Ca²⁺ transport between ER-mitochondria is important in autophagosome formation in Cd-induced neurodegeneration.

Graphical abstract

中文翻译：

---

通过神经元细胞中 ER-线粒体束缚复合物的 Ca2+ 转移有助于镉诱导的自噬

^{线粒体相关内质网 (ER) 膜 (MAM) 在钙离子 (Ca 2+} ) 转移和自噬等多种生理功能中发挥着关键作用；然而，在镉（Cd）诱导的神经毒性中控制这种相互作用的分子机制尚不清楚。该研究表明，Cd 诱导 PC12 细胞和原代神经元中 MAM 和线粒体 Ca ²⁺水平的改变。PC12 细胞或原代神经元中 mitofusin 2 (Mfn2) 的消融或沉默会阻断 ER 和线粒体的共定位，同时降低线粒体 Ca ^2+的效率摄取。此外，Mfn2 缺陷减少了 GRP75 和 VDAC1 之间的相互作用或共定位。^{有趣的是，在 Mfn2 -/-}或 Grp75 ^-/- PC12 细胞和 Mfn2- 或 Grp75- 沉默的原代神经元中，Cd 诱导的自噬蛋白水平的增强、LC3 和 Lamp2 的共定位以及 GFP-LC3 斑点降低。值得注意的是，特定的 Ca ²⁺单向转运体抑制剂 RuR 阻断了Cd 诱导的线粒体 Ca ^{2+摄取和自噬。}最后，本研究证明了IP3R-Grp75-VDAC1在MAMs中的束缚机制与Mfn2对自噬的调节有关，并涉及它们在介导线粒体Ca ^{2+中的作用。}从急诊室商店摄取。这些结果通过证明 ER-线粒体之间的 Ca ²⁺转运在 Cd 诱导的神经变性中的自噬体形成中很重要，为细胞器代谢过程提供了新的证据。

图形概要