Kamble Kajal, Kumar Ujjwal, Aahra Harsh, Yadav Mohit, Bhola Sumnil, Gupta Sarika
Molecular Sciences Lab, National Institute of Immunology, New Delhi, India.
Structural Immunology Lab, International Centre for Genetic Engineering and Biotechnology, New Delhi, India.
Autophagy. 2025 Mar;21(3):598-618. doi: 10.1080/15548627.2024.2410670. Epub 2024 Oct 24.
Prion disease is a fatal and infectious neurodegenerative disorder caused by the trans-conformation conversion of PRNP/PrP to PRNP/PrP. Accumulated PRNP/PrP-induced ER stress causes chronic unfolded protein response (UPR) activation, which is one of the fundamental steps in prion disease progression. However, the role of various ER-resident proteins in prion-induced ER stress is elusive. This study demonstrated that ARL6IP5 is compensatory upregulated in response to chronically activated UPR in the cellular prion disease model (RML-ScN2a). Furthermore, overexpression of ARL6IP5 overcomes ER stress by lowering the expression of chronically activated UPR pathway proteins. We discovered that ARL6IP5 induces reticulophagy to reduce the PRNP/PrP burden by releasing ER stress. Conversely, the knockdown of ARL6IP5 leads to inefficient macroautophagic/autophagic flux and elevated PRNP/PrP burden. Our study also uncovered that ARL6IP5-induced reticulophagy depends on Ca-mediated AMPK activation and can induce 3 MA-inhibited autophagic flux. The detailed mechanistic study revealed that ARL6IP5-induced reticulophagy involves interaction with soluble reticulophagy receptor CALCOCO1 and lysosomal marker LAMP1, leading to degradation in lysosomes. Here, we delineate the role of ARL6IP5 as a novel ER stress regulator and reticulophagy inducer that can effectively reduce the misfolded PRNP/PrP burden. Our research opens up a new avenue of selective autophagy in prion disease and represents a potential therapeutic target.: ARL6IP5: ADP ribosylation factor-like GTPase 6 interacting protein 5; AMPK: adenosine 5'-monophosphate (AMP)-activated protein kinase; CALCOCO1: calcium binding and coiled-coil domain 1; CQ: chloroquine; DAPI: 4'6-diamino-2-phenylindole; ER: endoplasmic reticulum; ERPHS: reticulophagy/ER-phagy sites; KD: knockdown; KD-CON: knockdown control; LAMP1: lysosomal-associated membrane protein 1; MAP1LC3/LC3, microtubule-associated protein 1 light chain 3; MTOR: mechanistic target of rapamycin kinase; MβCD: methyl beta cyclodextrin; 3 MA: 3-methyladenine; OE: overexpression; OE-CON: empty vector control; PrDs: prion diseases; PRNP/PrP: cellular prion protein (Kanno blood group); PRNP/PrP: infectious scrapie misfolded PRNP; Tm: tunicamycin; UPR: unfolded protein response; UPS: ubiquitin-proteasome system.
朊病毒病是一种由PRNP/PrP向PRNP/PrP的转构象转化引起的致命性传染性神经退行性疾病。积累的PRNP/PrP诱导的内质网应激导致慢性未折叠蛋白反应（UPR）激活，这是朊病毒病进展的基本步骤之一。然而，各种内质网驻留蛋白在朊病毒诱导的内质网应激中的作用尚不清楚。本研究表明，在细胞朊病毒病模型（RML-ScN2a）中，ARL6IP5响应慢性激活的UPR而代偿性上调。此外，ARL6IP5的过表达通过降低慢性激活的UPR途径蛋白的表达来克服内质网应激。我们发现ARL6IP5通过释放内质网应激诱导网织自噬以减轻PRNP/PrP负担。相反，ARL6IP5的敲低导致低效的巨自噬/自噬通量和PRNP/PrP负担增加。我们的研究还发现，ARL6IP5诱导的网织自噬依赖于钙介导的AMPK激活，并且可以诱导3-MA抑制的自噬通量。详细的机制研究表明，ARL6IP5诱导的网织自噬涉及与可溶性网织自噬受体CALCOCO1和溶酶体标志物LAMP1的相互作用，导致在溶酶体中降解。在这里，我们描述了ARL6IP5作为一种新型内质网应激调节剂和网织自噬诱导剂的作用，它可以有效减轻错误折叠的PRNP/PrP负担。我们的研究开辟了朊病毒病中选择性自噬的新途径，并代表了一个潜在的治疗靶点。：ARL6IP5：ADP核糖基化因子样GTP酶6相互作用蛋白5；AMPK：腺苷5'-单磷酸（AMP）激活的蛋白激酶；CALCOCO1：钙结合和卷曲螺旋结构域1；CQ：氯喹；DAPI：4'6-二氨基-2-苯基吲哚；内质网：内质网；ERPHS：网织自噬/内质网自噬位点；KD：敲低；KD-CON：敲低对照；LAMP1：溶酶体相关膜蛋白1；MAP1LC3/LC3，微管相关蛋白1轻链3；MTOR：雷帕霉素激酶的机制靶点；MβCD：甲基-β-环糊精；3-MA：3-甲基腺嘌呤；OE：过表达；OE-CON：空载体对照；PrDs：朊病毒病；PRNP/PrP：细胞朊蛋白（神户血型）；PRNP/PrP：传染性羊瘙痒病错误折叠的PRNP；Tm：衣霉素；UPR：未折叠蛋白反应；UPS：泛素-蛋白酶体系统
