Macroautophagy (autophagy) is an evolutionarily conserved recycling and stress response mechanism. Active at basal levels in eukaryotes, autophagy is upregulated under stress providing cells with building blocks such as amino acids. A lysosome-integrated sensor system composed of RRAG GTPases and MTOR complex 1 (MTORC1) regulates lysosome biogenesis and autophagy in response to amino acid availability. Stress-mediated inhibition of MTORC1 results in the dephosphorylation and nuclear translocation of the TFE/MITF family of transcriptional factors, and triggers an autophagy- and lysosomal-related gene transcription program. The role of family members TFEB and TFE3 have been studied in detail, but the importance of MITF proteins in autophagy regulation is not clear so far. Here we introduce for the first time a specific role for MITF in autophagy control that involves upregulation of MIR211. We show that, under stress conditions including starvation and MTOR inhibition, a MITF-MIR211 axis constitutes a novel feed-forward loop that controls autophagic activity in cells. Direct targeting of the MTORC2 component RICTOR by MIR211 led to the inhibition of the MTORC1 pathway, further stimulating MITF translocation to the nucleus and completing an autophagy amplification loop. In line with a ubiquitous function, MITF and MIR211 were co-expressed in all tested cell lines and human tissues, and the effects on autophagy were observed in a cell-type independent manner. Thus, our study provides direct evidence that MITF has rate-limiting and specific functions in autophagy regulation. Collectively, the MITF-MIR211 axis constitutes a novel and universal autophagy amplification system that sustains autophagic activity under stress conditions. Abbreviations: ACTB: actin beta; AKT: AKT serine/threonine kinase; AKT1S1/PRAS40: AKT1 substrate 1; AMPK: AMP-activated protein kinase; ATG: autophagy-related; BECN1: beclin 1; DEPTOR: DEP domain containing MTOR interacting protein; GABARAP: GABA type A receptor-associated protein; HIF1A: hypoxia inducible factor 1 subunit alpha; LAMP1: lysosomal associated membrane protein 1; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MAPKAP1/SIN1: mitogen-activated protein kinase associated protein 1; MITF: melanogenesis associated transcription factor; MLST8: MTOR associated protein, LST8 homolog; MRE: miRNA response element; MTOR: mechanistic target of rapamycin kinase; MTORC1: MTOR complex 1; MTORC2: MTOR complex 2; PRR5/Protor 1: proline rich 5; PRR5L/Protor 2: proline rich 5 like; RACK1: receptor for activated C kinase 1; RPTOR: regulatory associated protein of MTOR complex 1; RICTOR: RPTOR independent companion of MTOR complex 2; RPS6KB/p70S6K: ribosomal protein S6 kinase; RT-qPCR: quantitative reverse transcription-polymerase chain reaction; SQSTM1: sequestosome 1; STK11/LKB1: serine/threonine kinase 11; TFE3: transcription factor binding to IGHM enhancer 3; TFEB: transcription factor EB; TSC1/2: TSC complex subunit 1/2; ULK1: unc-51 like autophagy activating kinase 1; UVRAG: UV radiation resistance associated; VIM: vimentin; VPS11: VPS11, CORVET/HOPS core subunit; VPS18: VPS18, CORVET/HOPS core subunit; WIPI1: WD repeat domain, phosphoinositide interacting 1.

中文翻译：

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MITF-MIR211轴是细胞应激期间的新型自噬放大器系统。

宏观自噬（自噬）是一种进化上保守的循环和应激反应机制。自噬在真核生物中处于基础水平，在压力作用下自噬被上调，从而为细胞提供了诸如氨基酸之类的结构单元。溶酶体集成的传感器系统由RRAG GTPases和MTOR复合体1（MTORC1）组成，可调节溶酶体的生物发生和自噬，以响应氨基酸的利用。应力介导的MTORC1抑制导致TFE / MITF转录因子家族的去磷酸化和核易位，并触发自噬和溶酶体相关的基因转录程序。已经详细研究了家族成员TFEB和TFE3的作用，但是到目前为止，MITF蛋白在自噬调节中的重要性尚不清楚。在这里，我们首次介绍了MITF在涉及MIR211上调的自噬控制中的特定作用。我们表明，在包括饥饿和MTOR抑制在内的应激条件下，MITF-MIR211轴构成了控制细胞自噬活性的新型前馈环。MIR211直接靶向MTORC2组分RICTOR导致MTORC1途径受到抑制，进一步刺激MITF易位至核并完成自噬扩增环。与普遍存在的功能一致，MITF和MIR211在所有测试的细胞系和人体组织中共表达，并且以细胞类型独立的方式观察到对自噬的影响。因此，我们的研究提供了直接证据表明MITF在自噬调节中具有限速作用和特定功能。总的来说，MITF-MIR211轴构成了一种新颖的通用自噬扩增系统，可在压力条件下维持自噬活性。缩写：ACTB：肌动蛋白beta；AKT：AKT丝氨酸/苏氨酸激酶；AKT1S1 / PRAS40：AKT1基板1；AMPK：AMP激活的蛋白激酶；ATG：自噬相关；BECN1：beclin 1；DEPTOR：含有MTOR相互作用蛋白的DEP结构域；GABARAP：GABA A型受体相关蛋白；HIF1A：缺氧诱导因子1亚基α；LAMP1：溶酶体相关膜蛋白1；MAP1LC3B / LC3B：微管相关蛋白1轻链3 beta；MAPKAP1 / SIN1：丝裂原激活的蛋白激酶相关蛋白1；MITF：黑色素生成相关转录因子；MLST8：MTOR相关蛋白，LST8同源物；MRE：miRNA反应元件；MTOR：雷帕霉素激酶的机制靶标；MTORC1：MTOR复合体1；MTORC2：MTOR复合体2；PRR5 / Protor 1：脯氨酸丰富5; PRR5L / Protor 2：脯氨酸丰富5喜欢；RACK1：活化的C激酶1的受体；RPTOR：MTOR复合物1的调节相关蛋白；RICTOR：MTOR 2号楼的RPTOR独立伴侣；RPS6KB / p70S6K：核糖体蛋白S6激酶；RT-qPCR：定量逆转录聚合酶链反应；SQSTM1：螯合体1；STK11 / LKB1：丝氨酸/苏氨酸激酶11；TFE3：与IGHM增强子3结合的转录因子；TFEB：转录因子EB；TSC1 / 2：TSC复合亚基1/2；ULK1：unc-51样自噬激活激酶1；UVRAG：与抗紫外线辐射有关；VIM：波形蛋白；VPS11：VPS11，CORVET / HOPS核心子单元；VPS18：VPS18，CORVET / HOPS核心子单元；WIPI1：WD重复域，磷酸肌醇相互作用1。脯氨酸丰富5喜欢; RACK1：活化的C激酶1的受体；RPTOR：MTOR复合物1的调节相关蛋白；RICTOR：MTOR 2号楼的RPTOR独立伴侣；RPS6KB / p70S6K：核糖体蛋白S6激酶；RT-qPCR：定量逆转录聚合酶链反应；SQSTM1：螯合体1；STK11 / LKB1：丝氨酸/苏氨酸激酶11；TFE3：与IGHM增强子3结合的转录因子；TFEB：转录因子EB；TSC1 / 2：TSC复合亚基1/2；ULK1：unc-51样自噬激活激酶1；UVRAG：与抗紫外线辐射有关；VIM：波形蛋白；VPS11：VPS11，CORVET / HOPS核心子单元；VPS18：VPS18，CORVET / HOPS核心子单元；WIPI1：WD重复域，磷酸肌醇相互作用1。脯氨酸丰富5喜欢; RACK1：活化的C激酶1的受体；RPTOR：MTOR复合物1的调节相关蛋白；RICTOR：MTOR 2号楼的RPTOR独立伴侣；RPS6KB / p70S6K：核糖体蛋白S6激酶；RT-qPCR：定量逆转录聚合酶链反应；SQSTM1：螯合体1；STK11 / LKB1：丝氨酸/苏氨酸激酶11；TFE3：与IGHM增强子3结合的转录因子；TFEB：转录因子EB；TSC1 / 2：TSC复合亚基1/2；ULK1：unc-51样自噬激活激酶1；UVRAG：与抗紫外线辐射有关；VIM：波形蛋白；VPS11：VPS11，CORVET / HOPS核心子单元；VPS18：VPS18，CORVET / HOPS核心子单元；WIPI1：WD重复域，磷酸肌醇相互作用1。MTOR复合体2的RPTOR独立伴侣；RPS6KB / p70S6K：核糖体蛋白S6激酶；RT-qPCR：定量逆转录聚合酶链反应；SQSTM1：螯合体1；STK11 / LKB1：丝氨酸/苏氨酸激酶11；TFE3：与IGHM增强子3结合的转录因子；TFEB：转录因子EB；TSC1 / 2：TSC复合亚基1/2；ULK1：unc-51样自噬激活激酶1；UVRAG：与抗紫外线辐射有关；VIM：波形蛋白；VPS11：VPS11，CORVET / HOPS核心子单元；VPS18：VPS18，CORVET / HOPS核心子单元；WIPI1：WD重复域，磷酸肌醇相互作用1。MTOR复合体2的RPTOR独立伙伴；RPS6KB / p70S6K：核糖体蛋白S6激酶；RT-qPCR：定量逆转录聚合酶链反应；SQSTM1：螯合体1；STK11 / LKB1：丝氨酸/苏氨酸激酶11；TFE3：与IGHM增强子3结合的转录因子；TFEB：转录因子EB；TSC1 / 2：TSC复合亚基1/2；ULK1：unc-51样自噬激活激酶1；UVRAG：与抗紫外线辐射有关；VIM：波形蛋白；VPS11：VPS11，CORVET / HOPS核心子单元；VPS18：VPS18，CORVET / HOPS核心子单元；WIPI1：WD重复域，磷酸肌醇相互作用1。转录因子EB；TSC1 / 2：TSC复合亚基1/2；ULK1：unc-51样自噬激活激酶1；UVRAG：与抗紫外线辐射有关；VIM：波形蛋白；VPS11：VPS11，CORVET / HOPS核心子单元；VPS18：VPS18，CORVET / HOPS核心子单元；WIPI1：WD重复域，磷酸肌醇相互作用1。转录因子EB；TSC1 / 2：TSC复合亚基1/2；ULK1：unc-51样自噬激活激酶1；UVRAG：与抗紫外线辐射有关；VIM：波形蛋白；VPS11：VPS11，CORVET / HOPS核心子单元；VPS18：VPS18，CORVET / HOPS核心子单元；WIPI1：WD重复域，磷酸肌醇相互作用1。