Department of Pharmacology and New Drug Development Research Institute, Chonbuk National University Medical School, Jeonju, Republic of Korea.
Severance Biomedical Science Institute and Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea.
Autophagy. 2021 Mar;17(3):761-778. doi: 10.1080/15548627.2020.1732161. Epub 2020 Mar 13.
Lysosomal Ca contributes to macroautophagy/autophagy, an intracellular process for the degradation of cytoplasmic material and organelles in the lysosomes to protect cells against stress responses. TMBIM6 (transmembrane BAX inhibitor motif containing 6) is a Ca channel-like protein known to regulate ER stress response and apoptosis. In this study, we examined the as yet unknown role of TMBIM6 in regulating lysosomal Ca levels. The Ca efflux from the ER through TMBIM6 was found to increase the resting lysosomal Ca level, in which ITPR-independent regulation of Ca status was observed. Further, TMBIM6 regulated the local release of Ca through lysosomal MCOLN1/TRPML1 channels under nutrient starvation or MTOR inhibition. The local Ca efflux through MCOLN1 channels was found to activate PPP3/calcineurin, triggering TFEB (transcription factor EB) nuclear translocation, autophagy induction, and lysosome biogenesis. Upon genetic inactivation of TMBIM6, lysosomal Ca and the associated TFEB nuclear translocation were decreased. Furthermore, autophagy flux was significantly enhanced in the liver or kidney from starved mice compared with that in the counter mice. Together, our observations indicated that under stress conditions, TMBIM6 increases lysosomal Ca release, leading to PPP3/calcineurin-mediated TFEB activation and subsequently enhanced autophagy. Thus, TMBIM6, an ER membrane protein, is suggested to be a lysosomal Ca modulator that coordinates with autophagy to alleviate metabolism stress.: AVs: autophagic vacuoles; CEPIA: calcium-measuring organelle-entrapped protein indicator; ER: endoplasmic reticulum; GPN: glycyl-L-phenylalanine-beta-naphthylamide; ITPR/IP3R: inositol 1,4,5-trisphosphate receptor; LAMP1: lysosomal associated membrane protein 1; MCOLN/TRPML: mucolipin; MEF: mouse embryonic fibroblast; ML-SA1: mucolipin synthetic agonist 1; MTORC1: mechanistic target of rapamycin kinase complex 1; RPS6KB1: ribosomal protein S6 kinase B1; SQSTM1: sequestosome 1; TFEB: transcription factor EB; TKO: triple knockout; TMBIM6/BI-1: transmembrane BAX inhibitor motif containing 6.
溶酶体 Ca 参与巨自噬/自噬，这是一种细胞内过程，用于降解细胞质物质和溶酶体中的细胞器，以保护细胞免受应激反应的影响。TMBIM6（包含跨膜 BAX 抑制剂基序 6 的跨膜蛋白）是一种已知调节内质网应激反应和细胞凋亡的 Ca 通道样蛋白。在这项研究中，我们研究了 TMBIM6 在调节溶酶体 Ca 水平方面的未知作用。发现通过 TMBIM6 从内质网中排出 Ca 会增加静止溶酶体 Ca 水平，其中观察到 Ca 状态的 ITPR 非依赖性调节。此外，在营养饥饿或 MTOR 抑制下，TMBIM6 通过溶酶体 MCOLN1/TRPML1 通道调节局部 Ca 释放。发现通过 MCOLN1 通道的局部 Ca 外排会激活 PPP3/calcineurin，触发 TFEB（转录因子 EB）核易位、自噬诱导和溶酶体生物发生。当 TMBIM6 发生遗传失活时，溶酶体 Ca 和相关的 TFEB 核易位减少。此外，与对照小鼠相比，饥饿小鼠的肝脏或肾脏中的自噬通量明显增强。总之，我们的观察结果表明，在应激条件下，TMBIM6 增加溶酶体 Ca 释放，导致 PPP3/calcineurin 介导的 TFEB 激活，随后增强自噬。因此，内质网膜蛋白 TMBIM6 被认为是一种溶酶体 Ca 调节剂，它与自噬协同作用以缓解代谢应激。
