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Qian D, Cong Y, Wang R, Chen Q, Yan C, Gong D. Structural insight into the human SID1 transmembrane family member 2 reveals its lipid hydrolytic activity. Nat Commun 2023; 14:3568. [PMID: 37322007 PMCID: PMC10272179 DOI: 10.1038/s41467-023-39335-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Accepted: 06/08/2023] [Indexed: 06/17/2023] Open
Abstract
The systemic RNAi-defective (SID) transmembrane family member 2 (SIDT2) is a putative nucleic acid channel or transporter that plays essential roles in nucleic acid transport and lipid metabolism. Here, we report the cryo-electron microscopy (EM) structures of human SIDT2, which forms a tightly packed dimer with extensive interactions mediated by two previously uncharacterized extracellular/luminal β-strand-rich domains and the unique transmembrane domain (TMD). The TMD of each SIDT2 protomer contains eleven transmembrane helices (TMs), and no discernible nucleic acid conduction pathway has been identified within the TMD, suggesting that it may act as a transporter. Intriguingly, TM3-6 and TM9-11 form a large cavity with a putative catalytic zinc atom coordinated by three conserved histidine residues and one aspartate residue lying approximately 6 Å from the extracellular/luminal surface of the membrane. Notably, SIDT2 can hydrolyze C18 ceramide into sphingosine and fatty acid with a slow rate. The information presented advances the understanding of the structure-function relationships in the SID1 family proteins.
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Affiliation(s)
- Dandan Qian
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, Tianjin, 300350, China
| | - Ye Cong
- School of Life Sciences, Tsinghua University, Beijing, 100084, China
- Tsinghua-Peking Joint Center for Life Sciences, Tsinghua University, Beijing, 100084, China
- Beijing Frontier Research Center for Biological Structure, Beijing Advanced Innovation Center for Structural Biology, Tsinghua University, Beijing, 100084, China
- State Key Laboratory of Membrane Biology, Tsinghua University, Beijing, 100084, China
| | - Runhao Wang
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, Tianjin, 300350, China
| | - Quan Chen
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, Tianjin, 300350, China.
| | - Chuangye Yan
- School of Life Sciences, Tsinghua University, Beijing, 100084, China.
- Tsinghua-Peking Joint Center for Life Sciences, Tsinghua University, Beijing, 100084, China.
- Beijing Frontier Research Center for Biological Structure, Beijing Advanced Innovation Center for Structural Biology, Tsinghua University, Beijing, 100084, China.
- State Key Laboratory of Membrane Biology, Tsinghua University, Beijing, 100084, China.
| | - Deshun Gong
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, Tianjin, 300350, China.
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Sidt2 is a key protein in the autophagy-lysosomal degradation pathway and is essential for the maintenance of kidney structure and filtration function. Cell Death Dis 2021; 13:7. [PMID: 34923568 PMCID: PMC8684554 DOI: 10.1038/s41419-021-04453-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 11/18/2021] [Accepted: 12/02/2021] [Indexed: 12/24/2022]
Abstract
The regulation and homeostasis of autophagy are essential for maintaining organ morphology and function. As a lysosomal membrane protein, the effect of Sidt2 on kidney structure and renal autophagy is still unknown. In this study, we found that the kidneys of Sidt2-/- mice showed changes in basement membrane thickening, foot process fusion, and mitochondrial swelling, suggesting that the structure of the kidney was damaged. Increased urine protein at 24 h indicated that the kidney function was also damaged. At the same time, the absence of Sidt2 caused a decrease in the number of acidic lysosomes, a decrease in acid hydrolase activity and expression in the lysosome, and an increase of pH in the lysosome, suggesting that lysosomal function was impaired after Sidt2 deletion. The accumulation of autophagolysosomes, increased LC3-II and P62 protein levels, and decreased P62 mRNA levels indicated that the absence of the Sidt2 gene caused abnormal autophagy pathway flow. Chloroquine experiment, immunofluorescence autophagosome, and lysosome fusion assay, and Ad-mcherry-GFP-LC3B further indicated that, after Sidt2 deletion, the production of autophagosomes did not increase, but the fusion of autophagosomes and lysosomes and the degradation of autophagolysosomes were impaired. When incubating Sidt2-/- cells with the autophagy activator rapamycin, we found that it could activate autophagy, which manifested as an increase in autophagosomes, but it could not improve autophagolysosome degradation. Meanwhile, it further illustrated that the Sidt2 gene plays an important role in the smooth progress of autophagolysosome processes. In summary, the absence of the Sidt2 gene caused impaired lysosome function and a decreased number of acidic lysosomes, leading to formation and degradation disorders of the autophagolysosomes, which eventually manifested as abnormal kidney structure and function. Sidt2 is essential in maintaining the normal function of the lysosomes and the physiological stability of the kidneys.
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耿 梦, 王 李, 章 尧, 裴 文, 漆 梦, 杨 梦, 许 家, 梁 洋, 吕 坤, 何 春, 高 家. [Lysosomal membrane protein Sidt2 deletion impairs autophagy in human hepatocytes]. NAN FANG YI KE DA XUE XUE BAO = JOURNAL OF SOUTHERN MEDICAL UNIVERSITY 2021; 41:1207-1213. [PMID: 34549712 PMCID: PMC8527224 DOI: 10.12122/j.issn.1673-4254.2021.08.12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Indexed: 11/24/2022]
Abstract
OBJECTIVE To study the effect of lysosomal membrane protein Sidt2 deletion on autophagy in human hepatocytes. METHODS Crispr-Cas9 technology was used to construct a human hepatocyte (HL7702) model of Sidt2 knockout (Sidt2-/-), and the expression levels of the key autophagy proteins LC3II/I, P62 and autophagy-related proteins Atg5, Atg7, and Atg12 were detected.The co-localization of LC3B and P62 in the cells were analyzed with immunofluorescence assay to assess the identification and storage of P62 cargo proteins by the autophagosomes and the degradation of the autophagolysosomes.The co-localization of LC3B and LAMP1 was also determined with immunofluorescence assay to detect the fusion of the autophagosomes with the lysosomes, and LysoTracker was used to trace the acidic lysosomes. RESULTS We successfully constructed a HL7702 cell model of Sidt2+/+ and Sidt2-/-, and compared with Sidt2+/+ cells, the Sidt2-/- cell model showed significantly increased expressions of LC3-II/I and P62 (P < 0.01).Immunofluorescence assay showed a significant increase of LC3B and P62 expressions (P < 0.001) and obviously lowered expressions of Atg5, Atg7, and Atg12 in Sidt2-/- cells (P < 0.05).The co-localization of LC3B and P62 and that of LC3B and LAMP1 were both reduced and the number of acidic lysosomes was significantly lowered in Sidt2-/- cells (P < 0.05). CONCLUSION Sidt2 gene deletion disturbs the recognition and sequestration of P62 cargo protein by autophagosomes in human hepatocytes.At the same time, the decreased number of acidic lysosomes and the dysfunction of autophagosome and lysosome fusion cause the block of the autophagy-lysosome pathway, leading eventually to LC3B and P62 accumulation and impaired autophagy in the hepatocytes.
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Affiliation(s)
- 梦雅 耿
- 皖南医学院弋矶山医院内分泌科, 安徽 芜湖 241002Department of Endocrinology and Genetic Metabolism, Wannan Medical College, Wuhu 241002, China
- 皖南医学院弋矶山医院内分泌糖尿病研究所, 安徽 芜湖 241002Institute of Endocrine and Metabolic Diseases, Yijishan Hospital of Wannan Medical College, Wuhu 241002, China
- 皖南医学院临床医学院, 安徽 芜湖 241002School of Clinical Medicine, Wannan Medical College, Wuhu 241002, China
| | - 李卓 王
- 皖南医学院安徽省活性生物大分子研究安徽省重点实验室, 安徽 芜湖 241002Anhui Provincial Key Laboratory of Biological Macro-molecules Research, Wannan Medical College, Wuhu 241002, China
- 皖南医学院基础医学院生化教研室, 安徽 芜湖 241002Department of Biochemistry and Molecular Biology, Wannan Medical College, Wuhu 241002, China
| | - 尧 章
- 皖南医学院安徽省活性生物大分子研究安徽省重点实验室, 安徽 芜湖 241002Anhui Provincial Key Laboratory of Biological Macro-molecules Research, Wannan Medical College, Wuhu 241002, China
- 皖南医学院基础医学院生化教研室, 安徽 芜湖 241002Department of Biochemistry and Molecular Biology, Wannan Medical College, Wuhu 241002, China
| | - 文俊 裴
- 皖南医学院安徽省活性生物大分子研究安徽省重点实验室, 安徽 芜湖 241002Anhui Provincial Key Laboratory of Biological Macro-molecules Research, Wannan Medical College, Wuhu 241002, China
| | - 梦湘 漆
- 皖南医学院临床医学院, 安徽 芜湖 241002School of Clinical Medicine, Wannan Medical College, Wuhu 241002, China
| | - 梦 杨
- 皖南医学院临床医学院, 安徽 芜湖 241002School of Clinical Medicine, Wannan Medical College, Wuhu 241002, China
| | - 家豪 许
- 皖南医学院临床医学院, 安徽 芜湖 241002School of Clinical Medicine, Wannan Medical College, Wuhu 241002, China
| | - 洋洋 梁
- 皖南医学院临床医学院, 安徽 芜湖 241002School of Clinical Medicine, Wannan Medical College, Wuhu 241002, China
| | - 坤 吕
- 皖南医学院中心实验室, 安徽 芜湖 241002Central Laboratory, Wannan Medical College, Wuhu 241002, China
- 皖南医学院重大疾病非编码RNA转化研究安徽普通高校重点实验室, 安徽 芜湖 241002Anhui Provincial College Key Laboratory of Non-coding RNA Transformation Research on Critical Diseases, Wannan Medical College, Wuhu 241002, China
| | - 春玲 何
- 皖南医学院弋矶山医院内分泌科, 安徽 芜湖 241002Department of Endocrinology and Genetic Metabolism, Wannan Medical College, Wuhu 241002, China
| | - 家林 高
- 皖南医学院弋矶山医院内分泌科, 安徽 芜湖 241002Department of Endocrinology and Genetic Metabolism, Wannan Medical College, Wuhu 241002, China
- 皖南医学院弋矶山医院内分泌糖尿病研究所, 安徽 芜湖 241002Institute of Endocrine and Metabolic Diseases, Yijishan Hospital of Wannan Medical College, Wuhu 241002, China
- 皖南医学院安徽省活性生物大分子研究安徽省重点实验室, 安徽 芜湖 241002Anhui Provincial Key Laboratory of Biological Macro-molecules Research, Wannan Medical College, Wuhu 241002, China
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Abstract
Autophagy is a major intracellular degradation system that derives its degradative abilities from the lysosome. The most well-studied form of autophagy is macroautophagy, which delivers cytoplasmic material to lysosomes via the double-membraned autophagosome. Other forms of autophagy, namely chaperone-mediated autophagy and microautophagy, occur directly on the lysosome. Besides providing the means for degradation, lysosomes are also involved in autophagy regulation and can become substrates of autophagy when damaged. During autophagy, they exhibit notable changes, including increased acidification, enhanced enzymatic activity, and perinuclear localization. Despite their importance to autophagy, details on autophagy-specific regulation of lysosomes remain relatively scarce. This review aims to provide a summary of current understanding on the behaviour of lysosomes during autophagy and outline unexplored areas of autophagy-specific lysosome research.
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Affiliation(s)
- Willa Wen-You Yim
- Department of Biochemistry and Molecular Biology, Graduate School and Faculty of Medicine, The University of Tokyo, Tokyo, 113-0033 Japan
| | - Noboru Mizushima
- Department of Biochemistry and Molecular Biology, Graduate School and Faculty of Medicine, The University of Tokyo, Tokyo, 113-0033 Japan
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