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Wu Y, Zheng W, Xu G, Zhu L, Li Z, Chen J, Wang L, Chen S. C9orf72 controls hepatic lipid metabolism by regulating SREBP1 transport. Cell Death Differ 2024; 31:1070-1084. [PMID: 38816580 PMCID: PMC11303392 DOI: 10.1038/s41418-024-01312-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Revised: 04/26/2024] [Accepted: 05/07/2024] [Indexed: 06/01/2024] Open
Abstract
Sterol regulatory element binding transcription factors (SREBPs) play a crucial role in lipid homeostasis. They are processed and transported to the nucleus via COPII, where they induce the expression of lipogenic genes. COPII maintains the homeostasis of organelles and plays an essential role in the protein secretion pathways in eukaryotes. The formation of COPII begins at endoplasmic reticulum exit sites (ERES), and is regulated by SEC16A, which provides a platform for the assembly of COPII. However, there have been few studies on the changes in SEC16A protein levels. The repetitive expansion of the hexanucleotide sequence GGGGCC within the chromosome 9 open reading frame 72 (C9orf72) gene is a prevalent factor in the development of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Here, we found that the absence of C9orf72 leads to a decrease in SEC16A protein levels, resulting in reduced localization of the guanine nucleotide exchange factor SEC12 at the ERES. Consequently, the small GTP binding protein SAR1 is unable to bind the endoplasmic reticulum normally, impairing the assembly of COPII. Ultimately, the disruption of SREBPs transport decreases de novo lipogenesis. These results suggest that C9orf72 acts as a novel role in regulating lipid homeostasis and may serve as a potential therapeutic target for obesity.
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Affiliation(s)
- Yachen Wu
- Brain Center, Department of Neurosurgery, Ministry of Education Key Laboratory of Combinatorial Biosynthesis and Drug Discovery, Zhongnan Hospital of Wuhan University, School of Pharmaceutical Sciences, Wuhan University, Wuhan, 430071, China
- Department of Infectious Diseases, Institute of Pediatrics, Shenzhen Children's Hospital, Shenzhen, 518038, Guangdong, China
| | - Wenzhong Zheng
- Brain Center, Department of Neurosurgery, Ministry of Education Key Laboratory of Combinatorial Biosynthesis and Drug Discovery, Zhongnan Hospital of Wuhan University, School of Pharmaceutical Sciences, Wuhan University, Wuhan, 430071, China
| | - Guofeng Xu
- Brain Center, Department of Neurosurgery, Ministry of Education Key Laboratory of Combinatorial Biosynthesis and Drug Discovery, Zhongnan Hospital of Wuhan University, School of Pharmaceutical Sciences, Wuhan University, Wuhan, 430071, China
| | - Lijun Zhu
- Brain Center, Department of Neurosurgery, Ministry of Education Key Laboratory of Combinatorial Biosynthesis and Drug Discovery, Zhongnan Hospital of Wuhan University, School of Pharmaceutical Sciences, Wuhan University, Wuhan, 430071, China
| | - Zhiqiang Li
- Brain Center, Department of Neurosurgery, Ministry of Education Key Laboratory of Combinatorial Biosynthesis and Drug Discovery, Zhongnan Hospital of Wuhan University, School of Pharmaceutical Sciences, Wuhan University, Wuhan, 430071, China
| | - Jincao Chen
- Brain Center, Department of Neurosurgery, Ministry of Education Key Laboratory of Combinatorial Biosynthesis and Drug Discovery, Zhongnan Hospital of Wuhan University, School of Pharmaceutical Sciences, Wuhan University, Wuhan, 430071, China
| | - Lianrong Wang
- Brain Center, Department of Neurosurgery, Ministry of Education Key Laboratory of Combinatorial Biosynthesis and Drug Discovery, Zhongnan Hospital of Wuhan University, School of Pharmaceutical Sciences, Wuhan University, Wuhan, 430071, China.
- Department of Infectious Diseases, Institute of Pediatrics, Shenzhen Children's Hospital, Shenzhen, 518038, Guangdong, China.
| | - Shi Chen
- Brain Center, Department of Neurosurgery, Ministry of Education Key Laboratory of Combinatorial Biosynthesis and Drug Discovery, Zhongnan Hospital of Wuhan University, School of Pharmaceutical Sciences, Wuhan University, Wuhan, 430071, China.
- Department of Burn and Plastic Surgery, Shenzhen Institute of Translational Medicine, Shenzhen Key Laboratory of Microbiology in Genomic Modification & Editing and Application, Guangdong Provincial Key Laboratory of Systems Biology and Synthetic Biology for Urogenital Tumors, Shenzhen University Medical School, Shenzhen Second People's Hospital, The First Affiliated Hospital of Shenzhen University, Shenzhen, 518035, China.
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2
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Hendrix S, Kingma J, Ottenhoff R, Valiloo M, Svecla M, Zijlstra LF, Sachdev V, Kovac K, Levels JHM, Jongejan A, de Boer JF, Kuipers F, Rimbert A, Norata GD, Loregger A, Zelcer N. Hepatic SREBP signaling requires SPRING to govern systemic lipid metabolism in mice and humans. Nat Commun 2023; 14:5181. [PMID: 37626055 PMCID: PMC10457316 DOI: 10.1038/s41467-023-40943-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Accepted: 08/11/2023] [Indexed: 08/27/2023] Open
Abstract
The sterol regulatory element binding proteins (SREBPs) are transcription factors that govern cholesterol and fatty acid metabolism. We recently identified SPRING as a post-transcriptional regulator of SREBP activation. Constitutive or inducible global ablation of Spring in mice is not tolerated, and we therefore develop liver-specific Spring knockout mice (LKO). Transcriptomics and proteomics analysis reveal attenuated SREBP signaling in livers and hepatocytes of LKO mice. Total plasma cholesterol is reduced in male and female LKO mice in both the low-density lipoprotein and high-density lipoprotein fractions, while triglycerides are unaffected. Loss of Spring decreases hepatic cholesterol and triglyceride content due to diminished biosynthesis, which coincides with reduced very-low-density lipoprotein secretion. Accordingly, LKO mice are protected from fructose diet-induced hepatosteatosis. In humans, we find common genetic SPRING variants that associate with circulating high-density lipoprotein cholesterol and ApoA1 levels. This study positions SPRING as a core component of hepatic SREBP signaling and systemic lipid metabolism in mice and humans.
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Affiliation(s)
- Sebastian Hendrix
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences and Gastroenterology and Metabolism, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands
| | - Jenina Kingma
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences and Gastroenterology and Metabolism, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands
| | - Roelof Ottenhoff
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences and Gastroenterology and Metabolism, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands
| | - Masoud Valiloo
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences and Gastroenterology and Metabolism, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands
| | - Monika Svecla
- Department of Pharmacological and Biomolecular Sciences, Università degli Studi di Milano, Via Balzaretti 9, 20133, Milan, Italy
| | - Lobke F Zijlstra
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences and Gastroenterology and Metabolism, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands
| | - Vinay Sachdev
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences and Gastroenterology and Metabolism, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands
| | - Kristina Kovac
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences and Gastroenterology and Metabolism, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands
| | - Johannes H M Levels
- Department of Experimental Vascular Medicine, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands
| | - Aldo Jongejan
- Department of Epidemiology and Data Science, Bioinformatics Laboratory, of Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands
| | - Jan F de Boer
- Department of Pediatrics, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
- Department of Laboratory Medicine, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Folkert Kuipers
- Department of Pediatrics, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
- European Research Institute for the Biology of Ageing (ERIBA), University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Antoine Rimbert
- l'institut du thorax, Nantes Université, CNRS, INSERM, F-44000, Nantes, France
| | - Giuseppe D Norata
- Department of Pharmacological and Biomolecular Sciences, Università degli Studi di Milano, Via Balzaretti 9, 20133, Milan, Italy
| | - Anke Loregger
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences and Gastroenterology and Metabolism, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands
- Myllia Biotechnology GmbH, Am Kanal 27, 1110, Vienna, Austria
| | - Noam Zelcer
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences and Gastroenterology and Metabolism, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands.
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3
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In vitro reconstitution of COPII vesicles from Arabidopsis thaliana suspension-cultured cells. Nat Protoc 2023; 18:810-830. [PMID: 36599961 DOI: 10.1038/s41596-022-00781-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Accepted: 08/23/2022] [Indexed: 01/06/2023]
Abstract
Transport vesicles mediate protein traffic between endomembrane organelles in a highly selective and efficient manner. In vitro reconstitution systems have been widely used for studying mechanisms of vesicle formation, polar trafficking, and cargo specificity in mammals and yeast. However, this technique has not yet been applied to plants because of the large lytic vacuoles and rigid cell walls. Here, we describe an Arabidopsis-derived in vitro vesicle formation system to reconstitute, purify and characterize plant-derived coat protein complex II (COPII) vesicles. In this protocol, we provide a detailed method for the isolation of microsomes and cytosol from Arabidopsis thaliana suspension-cultured cells (7-8 h), in vitro COPII vesicle reconstitution and purification (4-5 h) and biochemical and microscopic analysis using specific antibodies against COPII cargo molecules for reconstitution efficiency evaluation (2 h). We also include detailed sample-preparation steps for analyzing vesicle morphology by cryogenic electron microscopy (1 h) and vesicle cargoes by quantitative proteomics (4 h). Routinely, the whole procedure takes ~18-20 h of operation time and enables plant researchers without specific expertise to achieve organelle purification or vesicle reconstitution for further characterization.
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4
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Qiu Z, Lin Z, Hu A, Liu Y, Zeng W, Zhao X, Shi X, Luo J, Song B. GRAMD1/ASTER-mediated cholesterol transport promotes Smoothened cholesterylation at the endoplasmic reticulum. EMBO J 2023; 42:e111513. [PMID: 36524353 PMCID: PMC9890235 DOI: 10.15252/embj.2022111513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2022] [Revised: 11/28/2022] [Accepted: 12/05/2022] [Indexed: 12/23/2022] Open
Abstract
Hedgehog (Hh) signaling pathway plays a pivotal role in embryonic development. Hh binding to Patched1 (PTCH1) derepresses Smoothened (SMO), thereby activating the downstream signal transduction. Covalent SMO modification by cholesterol in its cysteine-rich domain (CRD) is essential for SMO function. SMO cholesterylation is a calcium-accelerated autoprocessing reaction, and STIM1-ORAI1-mediated store-operated calcium entry promotes cholesterylation and activation of endosome-localized SMO. However, it is unknown whether the Hh-PTCH1 interplay regulates the activity of the endoplasmic reticulum (ER)-localized SMO. Here, we found that PTCH1 inhibited the COPII-dependent export of SMO from the ER, whereas Hh promoted this process. The RRxWxR amino acid motif in the cytosolic tail of SMO was essential for COPII recognition, ciliary localization, and signal transduction activity. Hh and PTCH1 regulated cholesterol modification of the ER-localized SMO, and SMO cholesterylation accelerated its exit from ER. The GRAMD1/ASTER sterol transport proteins facilitated cholesterol transfer to ER from PM, resulting in increased SMO cholesterylation and enhanced Hh signaling. Collectively, we reveal a regulatory role of GRAMD-mediated cholesterol transport in ER-resident SMO maturation and Hh signaling.
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Affiliation(s)
- Zhi‐Ping Qiu
- College of Life Sciences, Taikang Center for Life and Medical Sciences, Taikang Medical School, Hubei Key Laboratory of Cell HomeostasisWuhan UniversityWuhanChina
| | - Zi‐Cun Lin
- College of Life Sciences, Taikang Center for Life and Medical Sciences, Taikang Medical School, Hubei Key Laboratory of Cell HomeostasisWuhan UniversityWuhanChina
| | - Ao Hu
- College of Life Sciences, Taikang Center for Life and Medical Sciences, Taikang Medical School, Hubei Key Laboratory of Cell HomeostasisWuhan UniversityWuhanChina
| | - Yuan‐Bin Liu
- College of Life Sciences, Taikang Center for Life and Medical Sciences, Taikang Medical School, Hubei Key Laboratory of Cell HomeostasisWuhan UniversityWuhanChina
| | - Wan‐Er Zeng
- College of Life Sciences, Taikang Center for Life and Medical Sciences, Taikang Medical School, Hubei Key Laboratory of Cell HomeostasisWuhan UniversityWuhanChina
| | - Xiaolu Zhao
- College of Life Sciences, Taikang Center for Life and Medical Sciences, Taikang Medical School, Hubei Key Laboratory of Cell HomeostasisWuhan UniversityWuhanChina
| | - Xiong‐Jie Shi
- College of Life Sciences, Taikang Center for Life and Medical Sciences, Taikang Medical School, Hubei Key Laboratory of Cell HomeostasisWuhan UniversityWuhanChina
| | - Jie Luo
- College of Life Sciences, Taikang Center for Life and Medical Sciences, Taikang Medical School, Hubei Key Laboratory of Cell HomeostasisWuhan UniversityWuhanChina
| | - Bao‐Liang Song
- College of Life Sciences, Taikang Center for Life and Medical Sciences, Taikang Medical School, Hubei Key Laboratory of Cell HomeostasisWuhan UniversityWuhanChina
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5
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Chen D, Zhou X, Yan P, Yang C, Li Y, Han L, Ren X. Lipid metabolism reprogramming in colorectal cancer. J Cell Biochem 2023; 124:3-16. [PMID: 36334309 DOI: 10.1002/jcb.30347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Revised: 10/20/2022] [Accepted: 10/26/2022] [Indexed: 11/06/2022]
Abstract
The hallmark feature of metabolic reprogramming is now considered to be widespread in many malignancies, including colorectal cancer (CRC). Of the gastrointestinal tumors, CRC is one of the most common with a high metastasis rate and long insidious period. The incidence and mortality of CRC has increased in recent years. Metabolic reprogramming also has a significant role in the development and progression of CRC, especially lipid metabolic reprogramming. Many studies have reported that lipid metabolism reprogramming is similar to the Warburg effect with typical features affecting tumor biology including proliferation, migration, local invasion, apoptosis, and other biological behaviors of cancer cells. Therefore, studying the role of lipid metabolism in the occurrence and development of CRC will increase our understanding of its pathogenesis, invasion, metastasis, and other processes and provide new directions for the treatment of CRC. In this paper, we mainly describe the molecular mechanism of lipid metabolism reprogramming and its important role in the occurrence and development of CRC. In addition, to provide reference for subsequent research and clinical diagnosis and treatment we also review the treatments of CRC that target lipid metabolism.
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Affiliation(s)
- Dan Chen
- Department of Pathology & Cancer Research Center, Yanbian University Medical College, Yanji, China.,Key Laboratory of Pathobiology, Yanbian University, State Ethnic Affairs Commission, Yanji, China
| | - Xuebing Zhou
- Department of Pathology & Cancer Research Center, Yanbian University Medical College, Yanji, China.,Key Laboratory of Pathobiology, Yanbian University, State Ethnic Affairs Commission, Yanji, China
| | - PengYu Yan
- Department of Urology, First Hospital of Shanxi Medical University, Taiyuan, China
| | - Chunyu Yang
- Department of Pathology & Cancer Research Center, Yanbian University Medical College, Yanji, China.,Key Laboratory of Pathobiology, Yanbian University, State Ethnic Affairs Commission, Yanji, China
| | - Yuan Li
- Department of Pathology & Cancer Research Center, Yanbian University Medical College, Yanji, China.,Key Laboratory of Pathobiology, Yanbian University, State Ethnic Affairs Commission, Yanji, China
| | - Longzhe Han
- Key Laboratory of Pathobiology, Yanbian University, State Ethnic Affairs Commission, Yanji, China.,Department of Pathology, Affiliated Hospital of Yanbian University, Yanji, China
| | - Xiangshan Ren
- Department of Pathology & Cancer Research Center, Yanbian University Medical College, Yanji, China.,Key Laboratory of Pathobiology, Yanbian University, State Ethnic Affairs Commission, Yanji, China
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6
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Saito H, Tachiura W, Nishimura M, Shimizu M, Sato R, Yamauchi Y. Hydroxylation site-specific and production-dependent effects of endogenous oxysterols on cholesterol homeostasis: Implications for SREBP-2 and LXR. J Biol Chem 2022; 299:102733. [PMID: 36423680 PMCID: PMC9792893 DOI: 10.1016/j.jbc.2022.102733] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 10/26/2022] [Accepted: 11/14/2022] [Indexed: 11/23/2022] Open
Abstract
The cholesterol metabolites, oxysterols, play central roles in cholesterol feedback control. They modulate the activity of two master transcription factors that control cholesterol homeostatic responses, sterol regulatory element-binding protein-2 (SREBP-2) and liver X receptor (LXR). Although the role of exogenous oxysterols in regulating these transcription factors has been well established, whether endogenously synthesized oxysterols similarly control both SREBP-2 and LXR remains poorly explored. Here, we carefully validate the role of oxysterols enzymatically synthesized within cells in cholesterol homeostatic responses. We first show that SREBP-2 responds more sensitively to exogenous oxysterols than LXR in Chinese hamster ovary cells and rat primary hepatocytes. We then show that 25-hydroxycholesterol (25-HC), 27-hydroxycholesterol, and 24S-hydroxycholesterol endogenously synthesized by CH25H, CYP27A1, and CYP46A1, respectively, suppress SREBP-2 activity at different degrees by stabilizing Insig (insulin-induced gene) proteins, whereas 7α-hydroxycholesterol has little impact on SREBP-2. These results demonstrate the role of site-specific hydroxylation of endogenous oxysterols. In contrast, the expression of CH25H, CYP46A1, CYP27A1, or CYP7A1 fails to induce LXR target gene expression. We also show the 25-HC production-dependent suppression of SREBP-2 using a tetracycline-inducible CH25H expression system. To induce 25-HC production physiologically, murine macrophages are stimulated with a Toll-like receptor 4 ligand, and its effect on SREBP-2 and LXR is examined. The results also suggest that de novo synthesis of 25-HC preferentially regulates SREBP-2 activity. Finally, we quantitatively determine the specificity of the four cholesterol hydroxylases in living cells. Based on our current findings, we conclude that endogenous side-chain oxysterols primarily regulate the activity of SREBP-2, not LXR.
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Affiliation(s)
- Hodaka Saito
- Laboratory of Food Biochemistry, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Wakana Tachiura
- Laboratory of Food Biochemistry, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Mizuki Nishimura
- Laboratory of Food Biochemistry, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Makoto Shimizu
- Nutri-Life Science Laboratory, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Ryuichiro Sato
- Laboratory of Food Biochemistry, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan,Nutri-Life Science Laboratory, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan,AMED-CREST, Japan Agency for Medical Research and Development, Tokyo, Japan
| | - Yoshio Yamauchi
- Laboratory of Food Biochemistry, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan,Nutri-Life Science Laboratory, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan,AMED-CREST, Japan Agency for Medical Research and Development, Tokyo, Japan,For correspondence: Yoshio Yamauchi
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7
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Wang Y, Guo Y, Duan C, Li J, Ji S, Yan H, Liu Y, Zhang Y. LncGSAR Controls Ovarian Granulosa Cell Steroidogenesis via Sponging MiR-125b to Activate SCAP/SREBP Pathway. Int J Mol Sci 2022; 23:ijms232012132. [PMID: 36293007 PMCID: PMC9603659 DOI: 10.3390/ijms232012132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 09/30/2022] [Accepted: 09/30/2022] [Indexed: 11/30/2022] Open
Abstract
Long non-coding RNAs (lncRNAs) have been shown to play important roles in livestock fecundity, and many lncRNAs that affect follicular development and reproductive diseases have been identified in the ovary. However, only a few of them have been functionally annotated and mechanistically validated. In this study, we identified a new lncRNA (lncGSAR) and investigated its effects on the proliferation and steroidogenesis of ovine granulosa cells (GCs). High concentrations of glucose (add 33.6 mM glucose) caused high expression of lncGSAR in GCs by regulating its stability, and lncGSAR overexpression promoted GCs proliferation, estrogen secretion, and inhibited progesterone secretion, whereas interference with lncGASR had the opposite effect. Next, we found that the RNA molecules of lncGSAR act on MiR-125b as competitive endogenous RNA (ceRNA), and SREBP-cleavage-activating protein (SCAP) was verified as a target of MiR-125b. LncGASR overexpression increased the expression of SCAP, SREBP, and steroid hormone-related proteins, which can be attenuated by MiR-125b. Our results demonstrated that lncGSAR can act as a ceRNA to activate SCAP/SREBP signaling by sponging MiR-125b to regulate steroid hormone secretion in GCs. These findings provide new insights into the mechanisms of nutrient-regulated follicle development in ewes.
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Affiliation(s)
- Yong Wang
- Laboratory of Small Ruminant Genetics, Breeding and Reproduction, College of Animal Science and Technology, Hebei Agricultural University, Baoding 071000, China
| | - Yunxia Guo
- College of Life Science, Hebei Agricultural University, Baoding 071000, China
| | - Chunhui Duan
- Laboratory of Small Ruminant Genetics, Breeding and Reproduction, College of Animal Science and Technology, Hebei Agricultural University, Baoding 071000, China
| | - Junjie Li
- Laboratory of Small Ruminant Genetics, Breeding and Reproduction, College of Animal Science and Technology, Hebei Agricultural University, Baoding 071000, China
| | - Shoukun Ji
- Laboratory of Small Ruminant Genetics, Breeding and Reproduction, College of Animal Science and Technology, Hebei Agricultural University, Baoding 071000, China
| | - Huihui Yan
- Laboratory of Small Ruminant Genetics, Breeding and Reproduction, College of Animal Science and Technology, Hebei Agricultural University, Baoding 071000, China
| | - Yueqin Liu
- Laboratory of Small Ruminant Genetics, Breeding and Reproduction, College of Animal Science and Technology, Hebei Agricultural University, Baoding 071000, China
| | - Yingjie Zhang
- Laboratory of Small Ruminant Genetics, Breeding and Reproduction, College of Animal Science and Technology, Hebei Agricultural University, Baoding 071000, China
- Correspondence: ; Tel.: +86-31-2752-8366; Fax: +86-31-2752-8886
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8
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Faulkner R, Jo Y. Synthesis, function, and regulation of sterol and nonsterol isoprenoids. Front Mol Biosci 2022; 9:1006822. [PMID: 36275615 PMCID: PMC9579336 DOI: 10.3389/fmolb.2022.1006822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Accepted: 09/06/2022] [Indexed: 11/30/2022] Open
Abstract
Cholesterol, the bulk end-product of the mevalonate pathway, is a key component of cellular membranes and lipoproteins that transport lipids throughout the body. It is also a precursor of steroid hormones, vitamin D, and bile acids. In addition to cholesterol, the mevalonate pathway yields a variety of nonsterol isoprenoids that are essential to cell survival. Flux through the mevalonate pathway is tightly controlled to ensure cells continuously synthesize nonsterol isoprenoids but avoid overproducing cholesterol and other sterols. Endoplasmic reticulum (ER)-localized 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase (HMGCR), the rate limiting enzyme in the mevalonate pathway, is the focus of a complex feedback regulatory system governed by sterol and nonsterol isoprenoids. This review highlights transcriptional and post-translational regulation of HMGCR. Transcriptional regulation of HMGCR is mediated by the Scap-SREBP pathway. Post-translational control is initiated by the intracellular accumulation of sterols, which causes HMGCR to become ubiquitinated and subjected to proteasome-mediated ER-associated degradation (ERAD). Sterols also cause a subfraction of HMGCR molecules to bind the vitamin K2 synthetic enzyme, UbiA prenyltransferase domain-containing protein-1 (UBIAD1). This binding inhibits ERAD of HMGCR, which allows cells to continuously synthesize nonsterol isoprenoids such as geranylgeranyl pyrophosphate (GGPP), even when sterols are abundant. Recent studies reveal that UBIAD1 is a GGPP sensor, dissociating from HMGCR when GGPP thresholds are met to allow maximal ERAD. Animal studies using genetically manipulated mice disclose the physiological significance of the HMGCR regulatory system and we describe how dysregulation of these pathways contributes to disease.
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9
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Zhang W, Yang X, Li Y, Yu L, Zhang B, Zhang J, Cho WJ, Venkatarangan V, Chen L, Burugula BB, Bui S, Wang Y, Duan C, Kitzman JO, Li M. GCAF(TMEM251) regulates lysosome biogenesis by activating the mannose-6-phosphate pathway. Nat Commun 2022; 13:5351. [PMID: 36096887 PMCID: PMC9468337 DOI: 10.1038/s41467-022-33025-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Accepted: 08/29/2022] [Indexed: 11/09/2022] Open
Abstract
The mannose-6-phosphate (M6P) biosynthetic pathway for lysosome biogenesis has been studied for decades and is considered a well-understood topic. However, whether this pathway is regulated remains an open question. In a genome-wide CRISPR/Cas9 knockout screen, we discover TMEM251 as the first regulator of the M6P modification. Deleting TMEM251 causes mistargeting of most lysosomal enzymes due to their loss of M6P modification and accumulation of numerous undigested materials. We further demonstrate that TMEM251 localizes to the Golgi and is required for the cleavage and activity of GNPT, the enzyme that catalyzes M6P modification. In zebrafish, TMEM251 deletion leads to severe developmental defects including heart edema and skeletal dysplasia, which phenocopies Mucolipidosis Type II. Our discovery provides a mechanism for the newly discovered human disease caused by TMEM251 mutations. We name TMEM251 as GNPTAB cleavage and activity factor (GCAF) and its related disease as Mucolipidosis Type V.
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Affiliation(s)
- Weichao Zhang
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Xi Yang
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Yingxiang Li
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Linchen Yu
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Bokai Zhang
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Jianchao Zhang
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Woo Jung Cho
- BRCF Microscopy Core, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Varsha Venkatarangan
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Liang Chen
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Bala Bharathi Burugula
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Sarah Bui
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Yanzhuang Wang
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Cunming Duan
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Jacob O Kitzman
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Ming Li
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, 48109, USA.
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10
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Kou Y, Geng F, Guo D. Lipid Metabolism in Glioblastoma: From De Novo Synthesis to Storage. Biomedicines 2022; 10:1943. [PMID: 36009491 PMCID: PMC9405736 DOI: 10.3390/biomedicines10081943] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 08/01/2022] [Accepted: 08/06/2022] [Indexed: 12/12/2022] Open
Abstract
Glioblastoma (GBM) is the most lethal primary brain tumor. With limited therapeutic options, novel therapies are desperately needed. Recent studies have shown that GBM acquires large amounts of lipids for rapid growth through activation of sterol regulatory element-binding protein 1 (SREBP-1), a master transcription factor that regulates fatty acid and cholesterol synthesis, and cholesterol uptake. Interestingly, GBM cells divert substantial quantities of lipids into lipid droplets (LDs), a specific storage organelle for neutral lipids, to prevent lipotoxicity by increasing the expression of diacylglycerol acyltransferase 1 (DGAT1) and sterol-O-acyltransferase 1 (SOAT1), which convert excess fatty acids and cholesterol to triacylglycerol and cholesteryl esters, respectively. In this review, we will summarize recent progress on our understanding of lipid metabolism regulation in GBM to promote tumor growth and discuss novel strategies to specifically induce lipotoxicity to tumor cells through disrupting lipid storage, a promising new avenue for treating GBM.
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Affiliation(s)
- Yongjun Kou
- Department of Radiation Oncology, Ohio State Comprehensive Cancer Center, Arthur G. James Cancer Hospital and Richard J. Solove Research Institute, College of Medicine at The Ohio State University, Columbus, OH 43012, USA
| | - Feng Geng
- Department of Radiation Oncology, Ohio State Comprehensive Cancer Center, Arthur G. James Cancer Hospital and Richard J. Solove Research Institute, College of Medicine at The Ohio State University, Columbus, OH 43012, USA
| | - Deliang Guo
- Department of Radiation Oncology, Ohio State Comprehensive Cancer Center, Arthur G. James Cancer Hospital and Richard J. Solove Research Institute, College of Medicine at The Ohio State University, Columbus, OH 43012, USA
- Center for Cancer Metabolism, James Comprehensive Cancer Center at The Ohio State University, Columbus, OH 43210, USA
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11
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Cheng C, Geng F, Li Z, Zhong Y, Wang H, Cheng X, Zhao Y, Mo X, Horbinski C, Duan W, Chakravarti A, Cheng X, Guo D. Ammonia stimulates SCAP/Insig dissociation and SREBP-1 activation to promote lipogenesis and tumour growth. Nat Metab 2022; 4:575-588. [PMID: 35534729 PMCID: PMC9177652 DOI: 10.1038/s42255-022-00568-y] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Accepted: 03/30/2022] [Indexed: 12/31/2022]
Abstract
Tumorigenesis is associated with elevated glucose and glutamine consumption, but how cancer cells can sense their levels to activate lipid synthesis is unknown. Here, we reveal that ammonia, released from glutamine, promotes lipogenesis via activation of sterol regulatory element-binding proteins (SREBPs), endoplasmic reticulum-bound transcription factors that play a central role in lipid metabolism. Ammonia activates the dissociation of glucose-regulated, N-glycosylated SREBP-cleavage-activating protein (SCAP) from insulin-inducible gene protein (Insig), an endoplasmic reticulum-retention protein, leading to SREBP translocation and lipogenic gene expression. Notably, 25-hydroxycholesterol blocks ammonia to access its binding site on SCAP. Mutating aspartate D428 to alanine prevents ammonia binding to SCAP, abolishes SREBP-1 activation and suppresses tumour growth. Our study characterizes the unknown role, opposite to sterols, of ammonia as a key activator that stimulates SCAP-Insig dissociation and SREBP-1 activation to promote tumour growth and demonstrates that SCAP is a critical sensor of glutamine, glucose and sterol levels to precisely control lipid synthesis.
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Affiliation(s)
- Chunming Cheng
- Department of Radiation Oncology, Ohio State Comprehensive Cancer Center, Arthur G. James Cancer Hospital and Richard J. Solove Research Institute, and College of Medicine at The Ohio State University, Columbus, OH, USA
| | - Feng Geng
- Department of Radiation Oncology, Ohio State Comprehensive Cancer Center, Arthur G. James Cancer Hospital and Richard J. Solove Research Institute, and College of Medicine at The Ohio State University, Columbus, OH, USA
| | - Zoe Li
- Division of Medicinal Chemistry and Pharmacognosy, College of Pharmacy at The Ohio State University, Columbus, OH, USA
| | - Yaogang Zhong
- Department of Radiation Oncology, Ohio State Comprehensive Cancer Center, Arthur G. James Cancer Hospital and Richard J. Solove Research Institute, and College of Medicine at The Ohio State University, Columbus, OH, USA
| | - Huabao Wang
- Department of Radiation Oncology, Ohio State Comprehensive Cancer Center, Arthur G. James Cancer Hospital and Richard J. Solove Research Institute, and College of Medicine at The Ohio State University, Columbus, OH, USA
| | - Xiang Cheng
- Department of Radiation Oncology, Ohio State Comprehensive Cancer Center, Arthur G. James Cancer Hospital and Richard J. Solove Research Institute, and College of Medicine at The Ohio State University, Columbus, OH, USA
| | - Yue Zhao
- Bioinformatics Shared Resource Group, Department of Biomedical Informatics, College of Medicine at The Ohio State University, Columbus, OH, USA
| | - Xiaokui Mo
- Biostatistic Center and Department of Biomedical Informatics, College of Medicine at The Ohio State University, Columbus, OH, USA
| | - Craig Horbinski
- Departments of Pathology and Neurosurgery, Feinberg School of Medicine at Northwestern University, Chicago, IL, USA
| | - Wenrui Duan
- Department of Human and Molecular Genetics, Herbert Wertheim College of Medicine at the Florida International University, Miami, FL, USA
| | - Arnab Chakravarti
- Department of Radiation Oncology, Ohio State Comprehensive Cancer Center, Arthur G. James Cancer Hospital and Richard J. Solove Research Institute, and College of Medicine at The Ohio State University, Columbus, OH, USA
| | - Xiaolin Cheng
- Division of Medicinal Chemistry and Pharmacognosy, College of Pharmacy at The Ohio State University, Columbus, OH, USA
- Translational Data Analytics Institute (TDAI) at The Ohio State University, Columbus, OH, USA
| | - Deliang Guo
- Department of Radiation Oncology, Ohio State Comprehensive Cancer Center, Arthur G. James Cancer Hospital and Richard J. Solove Research Institute, and College of Medicine at The Ohio State University, Columbus, OH, USA.
- Center for Cancer Metabolism, James Comprehensive Cancer Center at The Ohio State University, Columbus, OH, USA.
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12
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Yan R, Cao P, Song W, Li Y, Wang T, Qian H, Yan C, Yan N. Structural basis for sterol sensing by Scap and Insig. Cell Rep 2021; 35:109299. [PMID: 34192549 DOI: 10.1016/j.celrep.2021.109299] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Revised: 04/29/2021] [Accepted: 06/03/2021] [Indexed: 11/30/2022] Open
Abstract
The sterol regulatory element-binding protein (SREBP) pathway monitors the cellular cholesterol level through sterol-regulated association between the SREBP cleavage-activating protein (Scap) and the insulin-induced gene (Insig). Despite structural determination of the Scap and Insig-2 complex bound to 25-hydroxycholesterol, the luminal domains of Scap remain unresolved. In this study, combining cryogenic electron microscopy (cryo-EM) analysis and artificial intelligence-facilitated structural prediction, we report the structure of the human Scap/Insig-2 complex purified in digitonin. The luminal domain loop 1 and a co-folded segment in loop 7 of Scap resemble those of the luminal/extracellular domain in NPC1 and related proteins, providing clues to the cholesterol-regulated interaction of loop 1 and loop 7. An additional luminal interface is observed between Scap and Insig. We also show that Scap(D428A), which inhibits SREBP activation even under sterol depletion, exhibits an identical conformation with the wild-type protein when complexed with Insig-2, and its constitutive suppression of the SREBP pathway may also involve a later step in protein trafficking.
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Affiliation(s)
- Renhong Yan
- Westlake Laboratory of Life Sciences and Biomedicine, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, 18 Shilongshan Road, Hangzhou 310024, Zhejiang Province, China; Institute of Biology, Westlake Institute for Advanced Study, 18 Shilongshan Road, Hangzhou 310024, Zhejiang Province, China.
| | - Pingping Cao
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Wenqi Song
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Yaning Li
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Tongtong Wang
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Hongwu Qian
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Chuangye Yan
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China.
| | - Nieng Yan
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.
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13
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Kim S, Khoriaty R, Li L, McClune M, Kalfa TA, Wu J, Peltier D, Fujiwara H, Sun Y, Oravecz-Wilson K, King RA, Ginsburg D, Reddy P. ER-to-Golgi transport and SEC23-dependent COPII vesicles regulate T cell alloimmunity. J Clin Invest 2021; 131:136574. [PMID: 33463537 DOI: 10.1172/jci136574] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Accepted: 11/12/2020] [Indexed: 01/24/2023] Open
Abstract
T cell-mediated responses are dependent on their secretion of key effector molecules. However, the critical molecular determinants of the secretion of these proteins are largely undefined. Here, we demonstrate that T cell activation increases trafficking via the ER-to-Golgi pathway. To study the functional role of this pathway, we generated mice with a T cell-specific deletion in SEC23B, a core subunit of coat protein complex II (COPII). We found that SEC23B critically regulated the T cell secretome following activation. SEC23B-deficient T cells exhibited a proliferative defect and reduced effector functions in vitro, as well as in experimental models of allogeneic and xenogeneic hematopoietic cell transplantation in vivo. However, T cells derived from 3 patients with congenital dyserythropoietic anemia II (CDAII), which results from Sec23b mutation, did not exhibit a similar phenotype. Mechanistic studies demonstrated that unlike murine KO T cells, T cells from patients with CDAII harbor increased levels of the closely related paralog, SEC23A. In vivo rescue of murine KO by expression of Sec23a from the Sec23b genomic locus restored T cell functions. Together, our data demonstrate a critical role for the COPII pathway, with evidence for functional overlap in vivo between SEC23 paralogs in the regulation of T cell immunity in both mice and humans.
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Affiliation(s)
- Stephanie Kim
- Department of Internal Medicine, Division of Hematology and Oncology.,Medical Scientist Training Program, and
| | - Rami Khoriaty
- Department of Internal Medicine, Division of Hematology and Oncology.,Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Lu Li
- Department of Internal Medicine, Division of Hematology and Oncology
| | - Madison McClune
- Department of Internal Medicine, Division of Hematology and Oncology
| | - Theodosia A Kalfa
- Cancer and Blood Diseases Institute, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA.,Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Julia Wu
- Department of Internal Medicine, Division of Hematology and Oncology.,Medical Scientist Training Program, and
| | - Daniel Peltier
- Department of Pediatrics, Division of Hematology and Oncology
| | - Hideaki Fujiwara
- Department of Internal Medicine, Division of Hematology and Oncology
| | - Yaping Sun
- Department of Internal Medicine, Division of Hematology and Oncology
| | | | - Richard A King
- Department of Internal Medicine, Division of Hematology and Oncology
| | - David Ginsburg
- Department of Internal Medicine, Division of Hematology and Oncology.,Department of Pediatrics, Division of Hematology and Oncology.,Department of Human Genetics.,Life Sciences Institute.,Howard Hughes Medical Institute, and.,Department of Internal Medicine, Division of Genetic Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | - Pavan Reddy
- Department of Internal Medicine, Division of Hematology and Oncology
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14
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Yan R, Cao P, Song W, Qian H, Du X, Coates HW, Zhao X, Li Y, Gao S, Gong X, Liu X, Sui J, Lei J, Yang H, Brown AJ, Zhou Q, Yan C, Yan N. A structure of human Scap bound to Insig-2 suggests how their interaction is regulated by sterols. Science 2021; 371:science.abb2224. [PMID: 33446483 DOI: 10.1126/science.abb2224] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2020] [Revised: 07/31/2020] [Accepted: 01/06/2021] [Indexed: 12/22/2022]
Abstract
The sterol regulatory element-binding protein (SREBP) pathway controls cellular homeostasis of sterols. The key players in this pathway, Scap and Insig-1 and -2, are membrane-embedded sterol sensors. The 25-hydroxycholesterol (25HC)-dependent association of Scap and Insig acts as the master switch for the SREBP pathway. Here, we present cryo-electron microscopy analysis of the human Scap and Insig-2 complex in the presence of 25HC, with the transmembrane (TM) domains determined at an average resolution of 3.7 angstrom. The sterol-sensing domain in Scap and all six TMs in Insig-2 were resolved. A 25HC molecule is sandwiched between the S4 to S6 segments in Scap and TMs 3 and 4 in Insig-2 in the luminal leaflet of the membrane. Unwinding of the middle of the Scap-S4 segment is crucial for 25HC binding and Insig association.
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Affiliation(s)
- Renhong Yan
- Westlake Laboratory of Life Sciences and Biomedicine, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou 310024, Zhejiang Province, China.,Institute of Biology, Westlake Institute for Advanced Study, Hangzhou 310024, Zhejiang Province, China
| | - Pingping Cao
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Wenqi Song
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Hongwu Qian
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Ximing Du
- School of Biotechnology and Biomolecular Science, University of New South Wales, Sydney, NSW 2052, Australia
| | - Hudson W Coates
- School of Biotechnology and Biomolecular Science, University of New South Wales, Sydney, NSW 2052, Australia
| | - Xin Zhao
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Yaning Li
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Shuai Gao
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Xin Gong
- Department of Biology, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Ximing Liu
- National Institute of Biological Sciences (NIBS), Beijing 102206, China
| | - Jianhua Sui
- National Institute of Biological Sciences (NIBS), Beijing 102206, China.,Tsinghua Institute of Multidisciplinary Biomedical Research, Tsinghua University, Beijing 102206, China
| | - Jianlin Lei
- Technology Center for Protein Sciences, Ministry of Education Key Laboratory of Protein Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Hongyuan Yang
- School of Biotechnology and Biomolecular Science, University of New South Wales, Sydney, NSW 2052, Australia
| | - Andrew J Brown
- School of Biotechnology and Biomolecular Science, University of New South Wales, Sydney, NSW 2052, Australia
| | - Qiang Zhou
- Westlake Laboratory of Life Sciences and Biomedicine, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou 310024, Zhejiang Province, China.,Institute of Biology, Westlake Institute for Advanced Study, Hangzhou 310024, Zhejiang Province, China
| | - Chuangye Yan
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China.
| | - Nieng Yan
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.
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15
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Zheng M, Wang W, Liu J, Zhang X, Zhang R. Lipid Metabolism in Cancer Cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1316:49-69. [PMID: 33740243 DOI: 10.1007/978-981-33-6785-2_4] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Metabolic reprogramming is one of the most critical hallmarks in cancer cells. In the past decades, mounting evidence has demonstrated that, besides the Warburg Effect, lipid metabolism dysregulation is also one of the essential characteristics of cancer cell metabolism. Lipids are water-insoluble molecules with diverse categories of phosphoglycerides, triacylglycerides, sphingolipids, sterols, etc. As the major utilization for energy storage, fatty acids are the primary building blocks for synthesizing triacylglycerides. And phosphoglycerides, sphingolipids, and sterols are the main components constructing biological membranes. More importantly, lipids play essential roles in signal transduction by functioning as second messengers or hormones. Much evidence has shown specific alterations of lipid metabolism in cancer cells. Consequently, the structural configuration of biological membranes, the energy homeostasis under nutrient stress, and the abundance of lipids in the intracellular signal transduction are affected by these alterations. Furthermore, lipid droplets accumulate in cancer cells and function adaptively to different types of harmful stress. This chapter reviews the regulation, functions, and therapeutic benefits of targeting lipid metabolism in cancer cells. Overall, this chapter highlights the significance of exploring more potential therapeutic strategies for malignant diseases by unscrambling lipid metabolism regulation in cancer cells.
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Affiliation(s)
- Minhua Zheng
- Department of Medical Genetics and Developmental Biology, The Fourth Military Medical University, Xi'an, People's Republic of China
| | - Wei Wang
- Department of Immunology, The Fourth Military Medical University, Xi'an, People's Republic of China
| | - Jun Liu
- Department of Biochemistry and Molecular Biology, The Fourth Military Medical University, Xi'an, People's Republic of China
| | - Xiao Zhang
- Department of Biochemistry and Molecular Biology, The Fourth Military Medical University, Xi'an, People's Republic of China
| | - Rui Zhang
- Department of Immunology, The Fourth Military Medical University, Xi'an, People's Republic of China.
- Department of Biochemistry and Molecular Biology, The Fourth Military Medical University, Xi'an, People's Republic of China.
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16
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Abstract
Cholesterol is an important component of lipids in animal membranes. All living cells can synthesize cholesterol, but the amount of synthesis is not sufficient, and therefore cholesterol synthesized in the liver is delivered to extrahepatic tissues as a form of LDL. The liver is a primary organ to not only synthesize but also catabolize cholesterol into bile acids, which ends up to excrete with the feces. The synthetic and catabolic pathways are precisely regulated under the negative-feedback control system under the transcriptional regulation driven by several transcription factors such as the sterol regulatory element-binding proteins (SREBPs), the liver x receptor, and the farnesoid x receptor. This review summarizes various findings including our recent discoveries in the molecular mechanism of activation of SREBP that is involved in the regulation of hepatic cholesterol biosynthesis, and a novel function of the metabolic end product of cholesterol, bile acids, in skeletal muscles.
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Affiliation(s)
- Ryuichiro Sato
- Department of Applied Biological Chemistry, The University of Tokyo , Tokyo, Japan
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17
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The Pivotal Role of the Dysregulation of Cholesterol Homeostasis in Cancer: Implications for Therapeutic Targets. Cancers (Basel) 2020; 12:cancers12061410. [PMID: 32486083 DOI: 10.3390/cancers12061410] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Revised: 05/23/2020] [Accepted: 05/28/2020] [Indexed: 12/12/2022] Open
Abstract
Cholesterol plays an important role in cellular homeostasis by maintaining the rigidity of cell membranes, providing a medium for signaling transduction, and being converted into other vital macromolecules, such as sterol hormones and bile acids. Epidemiological studies have shown the correlation between cholesterol content and cancer incidence worldwide. Accumulating evidence has shown the emerging roles of the dysregulation of cholesterol metabolism in cancer development. More specifically, recent reports have shown the distinct role of cholesterol in the suppression of immune cells, regulation of cell survival, and modulation of cancer stem cells in cancer. Here, we provide a comprehensive review of the epidemiological analysis, functional roles, and mechanistic action of cholesterol homeostasis in regard to its contribution to cancer development. Based on the existing data, cholesterol homeostasis is identified to be a new key player in cancer pathogenesis. Lastly, we also discuss the therapeutic implications of natural compounds and cholesterol-lowering drugs in cancer prevention and treatment. In conclusion, intervention in cholesterol metabolism may offer a new therapeutic avenue for cancer treatment.
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18
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The cellular function of SCAP in metabolic signaling. Exp Mol Med 2020; 52:724-729. [PMID: 32385422 PMCID: PMC7272406 DOI: 10.1038/s12276-020-0430-0] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2019] [Revised: 03/26/2020] [Accepted: 03/31/2020] [Indexed: 12/16/2022] Open
Abstract
Sterol regulatory element binding protein (SREBP) cleavage activating protein (SCAP) is a key regulator of SREBP maturation. SCAP induces translocation of SREBP from the endoplasmic reticulum to the Golgi apparatus, allowing it to regulate cellular triglyceride and cholesterol levels. Previous studies have shown that suppression of SREBP activation in SCAP conditional knockout mice reduced the accumulation of intracellular triglycerides, which eventually causes the development of metabolic diseases such as atherosclerosis, diabetes, hepatic steatosis, and insulin resistance. However, despite the significance of SCAP as a regulator of SREBP, its function has not been thoroughly discussed. In this review, we have summarized the function of SCAP and its regulatory proteins. Furthermore, we discuss recent studies regarding SCAP as a possible therapeutic target for hypertriglyceridemia and hyperlipidemia.
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19
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Kiatpakdee B, Sato K, Otsuka Y, Arashiki N, Chen Y, Tsumita T, Otsu W, Yamamoto A, Kawata R, Yamazaki J, Sugimoto Y, Takada K, Mohandas N, Inaba M. Cholesterol-binding protein TSPO2 coordinates maturation and proliferation of terminally differentiating erythroblasts. J Biol Chem 2020; 295:8048-8063. [PMID: 32358067 PMCID: PMC7278357 DOI: 10.1074/jbc.ra119.011679] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 04/20/2020] [Indexed: 02/02/2023] Open
Abstract
TSPO2 (translocator protein 2) is a transmembrane protein specifically expressed in late erythroblasts and has been postulated to mediate intracellular redistribution of cholesterol. We identified TSPO2 as the causative gene for the HK (high-K+) trait with immature red cell phenotypes in dogs and investigated the effects of the TSPO2 defects on erythropoiesis in HK dogs with the TSPO2 mutation and Tspo2 knockout (Tspo2−/−) mouse models. Bone marrow–derived erythroblasts from HK dogs showed increased binucleated and apoptotic cells at various stages of maturation and shed large nuclei with incomplete condensation when cultured in the presence of erythropoietin, indicating impaired maturation and cytokinesis. The canine TSPO2 induces cholesterol accumulation in the endoplasmic reticulum and could thereby regulate cholesterol availability by changing intracellular cholesterol distribution in erythroblasts. Tspo2−/− mice consistently showed impaired cytokinesis with increased binucleated erythroblasts, resulting in compensated anemia, and their red cell membranes had increased Na,K-ATPase, resembling the HK phenotype in dogs. Tspo2-deficient mouse embryonic stem cell–derived erythroid progenitor (MEDEP) cells exhibited similar morphological defects associated with a cell-cycle arrest at the G2/M phase, resulting in decreased cell proliferation and had a depletion in intracellular unesterified and esterified cholesterol. When the terminal maturation was induced, Tspo2−/− MEDEP cells showed delays in hemoglobinization; maturation-associated phenotypic changes in CD44, CD71, and TER119 expression; and cell-cycle progression. Taken together, these findings imply that TSPO2 is essential for coordination of maturation and proliferation of erythroblasts during normal erythropoiesis.
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Affiliation(s)
- Benjaporn Kiatpakdee
- Laboratory of Molecular Medicine, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
| | - Kota Sato
- Laboratory of Molecular Medicine, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
| | - Yayoi Otsuka
- Laboratory of Molecular Medicine, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
| | - Nobuto Arashiki
- Laboratory of Molecular Medicine, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
| | - Yuqi Chen
- Laboratory of Molecular Medicine, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
| | - Takuya Tsumita
- Laboratory of Molecular Medicine, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
| | - Wataru Otsu
- Laboratory of Molecular Medicine, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
| | - Akito Yamamoto
- Laboratory of Molecular Medicine, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
| | - Reo Kawata
- Laboratory of Molecular Medicine, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
| | - Jumpei Yamazaki
- Laboratory of Molecular Medicine, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
| | | | - Kensuke Takada
- Laboratory of Molecular Medicine, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
| | - Narla Mohandas
- Red Cell Physiology Laboratory, New York Blood Center, New York, New York, USA
| | - Mutsumi Inaba
- Laboratory of Molecular Medicine, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
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20
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Tao Y, Yang Y, Zhou R, Gong T. Golgi Apparatus: An Emerging Platform for Innate Immunity. Trends Cell Biol 2020; 30:467-477. [PMID: 32413316 DOI: 10.1016/j.tcb.2020.02.008] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 02/24/2020] [Accepted: 02/24/2020] [Indexed: 12/23/2022]
Abstract
The Golgi apparatus serves as a receiving station where proteins from the endoplasmic reticulum (ER) are further processed before being sent to other cellular compartments. In addition to its well-appreciated roles in vesicular trafficking and protein/lipid secretion, recent studies have demonstrated that the Golgi acts as a signaling platform to facilitate multiple innate immune pathways. Moreover, the membranous networks that connect the Golgi with the ER, mitochondria, endosomes, and autophagosomes provide convenient access to innate immune signal transduction and subsequent effector responses. Here, we review the emerging knowledge about the roles of the Golgi in the initiation and activation of innate immune signaling. Moreover, microbial hijacking strategies that inhibit Golgi-associated innate immune responses will also be discussed.
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Affiliation(s)
- Ye Tao
- Department of Otolaryngology-Head and Neck Surgery, the First Affiliated Hospital of Anhui Medical University, Hefei 230022, China; Hefei National Laboratory for Physical Sciences at Microscale, the CAS Key Laboratory of Innate Immunity and Chronic Disease, School of Basic Medical Science, Division of Life Science and Medicine, University of Science and Technology of China, Hefei 230027, China
| | - Yanqing Yang
- Department of Clinical Laboratory, the First Affiliated Hospital of Bengbu Medical College, Bengbu 233004, China
| | - Rongbin Zhou
- Hefei National Laboratory for Physical Sciences at Microscale, the CAS Key Laboratory of Innate Immunity and Chronic Disease, School of Basic Medical Science, Division of Life Science and Medicine, University of Science and Technology of China, Hefei 230027, China.
| | - Tao Gong
- Hefei National Laboratory for Physical Sciences at Microscale, the CAS Key Laboratory of Innate Immunity and Chronic Disease, School of Basic Medical Science, Division of Life Science and Medicine, University of Science and Technology of China, Hefei 230027, China.
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21
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Loregger A, Raaben M, Nieuwenhuis J, Tan JME, Jae LT, van den Hengel LG, Hendrix S, van den Berg M, Scheij S, Song JY, Huijbers IJ, Kroese LJ, Ottenhoff R, van Weeghel M, van de Sluis B, Brummelkamp T, Zelcer N. Haploid genetic screens identify SPRING/C12ORF49 as a determinant of SREBP signaling and cholesterol metabolism. Nat Commun 2020; 11:1128. [PMID: 32111832 PMCID: PMC7048761 DOI: 10.1038/s41467-020-14811-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Accepted: 02/03/2020] [Indexed: 02/07/2023] Open
Abstract
The sterol-regulatory element binding proteins (SREBP) are central transcriptional regulators of lipid metabolism. Using haploid genetic screens we identify the SREBP Regulating Gene (SPRING/C12ORF49) as a determinant of the SREBP pathway. SPRING is a glycosylated Golgi-resident membrane protein and its ablation in Hap1 cells, Hepa1-6 hepatoma cells, and primary murine hepatocytes reduces SREBP signaling. In mice, Spring deletion is embryonic lethal yet silencing of hepatic Spring expression also attenuates the SREBP response. Mechanistically, attenuated SREBP signaling in SPRINGKO cells results from reduced SREBP cleavage-activating protein (SCAP) and its mislocalization to the Golgi irrespective of the cellular sterol status. Consistent with limited functional SCAP in SPRINGKO cells, reintroducing SCAP restores SREBP-dependent signaling and function. Moreover, in line with the role of SREBP in tumor growth, a wide range of tumor cell lines display dependency on SPRING expression. In conclusion, we identify SPRING as a previously unrecognized modulator of SREBP signaling.
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Affiliation(s)
- Anke Loregger
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences and Gastroenterology and Metabolism, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands
| | - Matthijs Raaben
- Oncode Institute, Division of Biochemistry, The Netherlands Cancer Institute, Plesmanlaan 121, 1066CX, Amsterdam, The Netherlands
| | - Joppe Nieuwenhuis
- Oncode Institute, Division of Biochemistry, The Netherlands Cancer Institute, Plesmanlaan 121, 1066CX, Amsterdam, The Netherlands
| | - Josephine M E Tan
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences and Gastroenterology and Metabolism, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands
| | - Lucas T Jae
- Oncode Institute, Division of Biochemistry, The Netherlands Cancer Institute, Plesmanlaan 121, 1066CX, Amsterdam, The Netherlands.,Gene Center and Department of Biochemistry, Ludwig-Maximilians-Universität München, Feodor Lynen-Str. 25, 81377, Munich, Germany
| | - Lisa G van den Hengel
- Oncode Institute, Division of Biochemistry, The Netherlands Cancer Institute, Plesmanlaan 121, 1066CX, Amsterdam, The Netherlands
| | - Sebastian Hendrix
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences and Gastroenterology and Metabolism, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands
| | - Marlene van den Berg
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences and Gastroenterology and Metabolism, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands
| | - Saskia Scheij
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences and Gastroenterology and Metabolism, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands
| | - Ji-Ying Song
- Division of Experimental Animal Pathology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066CX, Amsterdam, The Netherlands
| | - Ivo J Huijbers
- Mouse Clinic for Cancer and Aging (MCCA) Transgenic Facility, The Netherlands Cancer Institute, Plesmanlaan 121, 1066CX, Amsterdam, The Netherlands
| | - Lona J Kroese
- Mouse Clinic for Cancer and Aging (MCCA) Transgenic Facility, The Netherlands Cancer Institute, Plesmanlaan 121, 1066CX, Amsterdam, The Netherlands
| | - Roelof Ottenhoff
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences and Gastroenterology and Metabolism, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands
| | - Michel van Weeghel
- Laboratory of Genetic and Metabolic Diseases and Core Facility Metabolomics, Academic Medical Center of the University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands
| | - Bart van de Sluis
- Department of Pediatrics, University Medical Center Groningen, Antonius Deusinglaan 1, 9713AV, Groningen, The Netherlands.,iPSC/CRISPR Center Groningen, University Medical Center Groningen, Antonius Deusinglaan 1, 9713AV, Groningen, The Netherlands
| | - Thijn Brummelkamp
- Oncode Institute, Division of Biochemistry, The Netherlands Cancer Institute, Plesmanlaan 121, 1066CX, Amsterdam, The Netherlands. .,CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14, A-1090, Vienna, Austria. .,Cancer Genomics Center, Amsterdam, The Netherlands.
| | - Noam Zelcer
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences and Gastroenterology and Metabolism, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands.
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22
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Liu Y, Hua W, Li Y, Xian X, Zhao Z, Liu C, Zou J, Li J, Fang X, Zhu Y. Berberine suppresses colon cancer cell proliferation by inhibiting the SCAP/SREBP-1 signaling pathway-mediated lipogenesis. Biochem Pharmacol 2019; 174:113776. [PMID: 31874145 DOI: 10.1016/j.bcp.2019.113776] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Accepted: 12/19/2019] [Indexed: 02/07/2023]
Abstract
Lipid metabolism is a significant section of energy homeostasis, and it affects the development of various cancers. Previous studies have revealed that berberine has strong anticancer and blood lipid-lowering effects. Here, we further investigated the effects of berberine on cell proliferation and lipogenesis in colon cancer cells and the relationship between the two effects. We found that berberine inhibited cell proliferation by inducing G0/G1 phase cell cycle arrest in colon cancer cells. Moreover, the expressions of key lipogenic enzymes were down-regulated by berberine and led to the suppressed lipid synthesis, which was linked to cell proliferation via Wnt/β-catenin pathway. Importantly, berberine inhibited sterol regulatory element-binding protein-1 (SREBP-1) activation and SREBP cleavage-activating protein (SCAP) expression, resulting in the downregulation of these lipogenic enzymes. Knockdown of SCAP by shRNA could abolish the effect of berberine on SREBP-1 activation. Besides the inhibitory effects in vitro, berberine suppressed the growth and lipogenesis of colon cancer xenograft in a SCAP-dependent manner as well. Together, our results suggest that berberine may serve as a candidate against tumor growth of colon cancer partially through targeting SCAP/SREBP-1 pathway driving lipogenesis.
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Affiliation(s)
- Yunxin Liu
- Department of Pharmacy, Nanjing First Hospital, Nanjing Medical University, Nanjing 210029, PR China; School of Basic Medicine & Clinical Pharmacy, China Pharmaceutical University, Nanjing 211198, PR China
| | - Weiwei Hua
- School of Basic Medicine & Clinical Pharmacy, China Pharmaceutical University, Nanjing 211198, PR China; Department of Pharmacy, Institute of Dermatology, Chinese Academy of Medical Sciences and Peking Union Medical College, Nanjing 210042, PR China
| | - Yao Li
- School of Basic Medicine & Clinical Pharmacy, China Pharmaceutical University, Nanjing 211198, PR China
| | - Xirui Xian
- School of Basic Medicine & Clinical Pharmacy, China Pharmaceutical University, Nanjing 211198, PR China
| | - Zheng Zhao
- Department of Pharmacy, Nanjing First Hospital, Nanjing Medical University, Nanjing 210029, PR China; School of Basic Medicine & Clinical Pharmacy, China Pharmaceutical University, Nanjing 211198, PR China
| | - Chao Liu
- Department of Pharmacy, Nanjing First Hospital, Nanjing Medical University, Nanjing 210029, PR China; School of Basic Medicine & Clinical Pharmacy, China Pharmaceutical University, Nanjing 211198, PR China
| | - Jianjun Zou
- Department of Pharmacy, Nanjing First Hospital, Nanjing Medical University, Nanjing 210029, PR China; School of Basic Medicine & Clinical Pharmacy, China Pharmaceutical University, Nanjing 211198, PR China
| | - Jun Li
- Department of Pharmacy, Nanjing First Hospital, Nanjing Medical University, Nanjing 210029, PR China; School of Basic Medicine & Clinical Pharmacy, China Pharmaceutical University, Nanjing 211198, PR China
| | - Xianjun Fang
- Department of Pharmacy, The First Affiliated Hospital of Anhui Medical University, Hefei 230022, PR China.
| | - Yubing Zhu
- Department of Pharmacy, Nanjing First Hospital, Nanjing Medical University, Nanjing 210029, PR China; School of Basic Medicine & Clinical Pharmacy, China Pharmaceutical University, Nanjing 211198, PR China.
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23
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Jo S, Fonseca TL, Bocco BMLC, Fernandes GW, McAninch EA, Bolin AP, Da Conceição RR, Werneck-de-Castro JP, Ignacio DL, Egri P, Németh D, Fekete C, Bernardi MM, Leitch VD, Mannan NS, Curry KF, Butterfield NC, Bassett JD, Williams GR, Gereben B, Ribeiro MO, Bianco AC. Type 2 deiodinase polymorphism causes ER stress and hypothyroidism in the brain. J Clin Invest 2019; 129:230-245. [PMID: 30352046 PMCID: PMC6307951 DOI: 10.1172/jci123176] [Citation(s) in RCA: 72] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Accepted: 10/11/2018] [Indexed: 12/31/2022] Open
Abstract
Levothyroxine (LT4) is a form of thyroid hormone used to treat hypothyroidism. In the brain, T4 is converted to the active form T3 by type 2 deiodinase (D2). Thus, it is intriguing that carriers of the Thr92Ala polymorphism in the D2 gene (DIO2) exhibit clinical improvement when liothyronine (LT3) is added to LT4 therapy. Here, we report that D2 is a cargo protein in ER Golgi intermediary compartment (ERGIC) vesicles, recycling between ER and Golgi. The Thr92-to-Ala substitution (Ala92-D2) caused ER stress and activated the unfolded protein response (UPR). Ala92-D2 accumulated in the trans-Golgi and generated less T3, which was restored by eliminating ER stress with the chemical chaperone 4-phenyl butyric acid (4-PBA). An Ala92-Dio2 polymorphism-carrying mouse exhibited UPR and hypothyroidism in distinct brain areas. The mouse refrained from physical activity, slept more, and required additional time to memorize objects. Enhancing T3 signaling in the brain with LT3 improved cognition, whereas restoring proteostasis with 4-PBA eliminated the Ala92-Dio2 phenotype. In contrast, primary hypothyroidism intensified the Ala92-Dio2 phenotype, with only partial response to LT4 therapy. Disruption of cellular proteostasis and reduced Ala92-D2 activity may explain the failure of LT4 therapy in carriers of Thr92Ala-DIO2.
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Affiliation(s)
- Sungro Jo
- Division of Endocrinology and Metabolism, Rush University Medical Center, Chicago, Illinois, USA
| | - Tatiana L. Fonseca
- Section of Adult and Pediatric Endocrinology, Diabetes & Metabolism, Department of Medicine, University of Chicago, Chicago, Illinois, USA
| | - Barbara M. L. C. Bocco
- Section of Adult and Pediatric Endocrinology, Diabetes & Metabolism, Department of Medicine, University of Chicago, Chicago, Illinois, USA
| | - Gustavo W. Fernandes
- Section of Adult and Pediatric Endocrinology, Diabetes & Metabolism, Department of Medicine, University of Chicago, Chicago, Illinois, USA
| | - Elizabeth A. McAninch
- Division of Endocrinology and Metabolism, Rush University Medical Center, Chicago, Illinois, USA
| | - Anaysa P. Bolin
- Division of Endocrinology and Metabolism, Rush University Medical Center, Chicago, Illinois, USA
- Department of Pharmacology, Biomedical Science Institute, University of São Paulo, and
| | - Rodrigo R. Da Conceição
- Division of Endocrinology and Metabolism, Rush University Medical Center, Chicago, Illinois, USA
- Laboratory of Molecular and Translational Endocrinology, Department of Medicine, Federal University of São Paulo, São Paulo, SP, Brazil
| | | | - Daniele L. Ignacio
- Division of Endocrinology and Metabolism, Rush University Medical Center, Chicago, Illinois, USA
| | - Péter Egri
- Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Dorottya Németh
- Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Csaba Fekete
- Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Maria Martha Bernardi
- Graduate Program of Environmental and Experimental Pathology, Graduate Program of Dentistry, Universidade Paulista, São Paulo, SP, Brazil
| | - Victoria D. Leitch
- Molecular Endocrinology Laboratory, Department of Medicine, Imperial College London, London, United Kingdom
| | - Naila S. Mannan
- Molecular Endocrinology Laboratory, Department of Medicine, Imperial College London, London, United Kingdom
| | - Katharine F. Curry
- Molecular Endocrinology Laboratory, Department of Medicine, Imperial College London, London, United Kingdom
| | - Natalie C. Butterfield
- Molecular Endocrinology Laboratory, Department of Medicine, Imperial College London, London, United Kingdom
| | - J.H. Duncan Bassett
- Molecular Endocrinology Laboratory, Department of Medicine, Imperial College London, London, United Kingdom
| | - Graham R. Williams
- Molecular Endocrinology Laboratory, Department of Medicine, Imperial College London, London, United Kingdom
| | - Balázs Gereben
- Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Miriam O. Ribeiro
- Developmental Disorders Program, Center of Biological Science and Health, Mackenzie Presbyterian University, São Paulo, SP, Brazil
| | - Antonio C. Bianco
- Section of Adult and Pediatric Endocrinology, Diabetes & Metabolism, Department of Medicine, University of Chicago, Chicago, Illinois, USA
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24
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Cheng C, Geng F, Cheng X, Guo D. Lipid metabolism reprogramming and its potential targets in cancer. Cancer Commun (Lond) 2018; 38:27. [PMID: 29784041 PMCID: PMC5993136 DOI: 10.1186/s40880-018-0301-4] [Citation(s) in RCA: 438] [Impact Index Per Article: 73.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Accepted: 05/12/2018] [Indexed: 12/13/2022] Open
Abstract
Reprogramming of lipid metabolism is a newly recognized hallmark of malignancy. Increased lipid uptake, storage and lipogenesis occur in a variety of cancers and contribute to rapid tumor growth. Lipids constitute the basic structure of membranes and also function as signaling molecules and energy sources. Sterol regulatory element-binding proteins (SREBPs), a family of membrane-bound transcription factors in the endoplasmic reticulum, play a central role in the regulation of lipid metabolism. Recent studies have revealed that SREBPs are highly up-regulated in various cancers and promote tumor growth. SREBP cleavage-activating protein is a key transporter in the trafficking and activation of SREBPs as well as a critical glucose sensor, thus linking glucose metabolism and de novo lipid synthesis. Targeting altered lipid metabolic pathways has become a promising anti-cancer strategy. This review summarizes recent progress in our understanding of lipid metabolism regulation in malignancy, and highlights potential molecular targets and their inhibitors for cancer treatment.
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Affiliation(s)
- Chunming Cheng
- Department of Radiation Oncology, The Ohio State University James Comprehensive Cancer Center and College of Medicine, Columbus, OH, 43210, USA
| | - Feng Geng
- Department of Radiation Oncology, The Ohio State University James Comprehensive Cancer Center and College of Medicine, Columbus, OH, 43210, USA
| | - Xiang Cheng
- Department of Radiation Oncology, The Ohio State University James Comprehensive Cancer Center and College of Medicine, Columbus, OH, 43210, USA
| | - Deliang Guo
- Department of Radiation Oncology, The Ohio State University James Comprehensive Cancer Center and College of Medicine, Columbus, OH, 43210, USA.
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25
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TFG facilitates outer coat disassembly on COPII transport carriers to promote tethering and fusion with ER-Golgi intermediate compartments. Proc Natl Acad Sci U S A 2017; 114:E7707-E7716. [PMID: 28851831 DOI: 10.1073/pnas.1709120114] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The conserved coat protein complex II (COPII) mediates the initial steps of secretory protein trafficking by assembling onto subdomains of the endoplasmic reticulum (ER) in two layers to generate cargo-laden transport carriers that ultimately fuse with an adjacent ER-Golgi intermediate compartment (ERGIC). Here, we demonstrate that Trk-fused gene (TFG) binds directly to the inner layer of the COPII coat. Specifically, the TFG C terminus interacts with Sec23 through a shared interface with the outer COPII coat and the cargo receptor Tango1/cTAGE5. Our findings indicate that TFG binding to Sec23 outcompetes these other associations in a concentration-dependent manner and ultimately promotes outer coat dissociation. Additionally, we demonstrate that TFG tethers vesicles harboring the inner COPII coat, which contributes to their clustering between the ER and ERGIC in cells. Together, our studies define a mechanism by which COPII transport carriers are retained locally at the ER/ERGIC interface after outer coat disassembly, which is a prerequisite for fusion with ERGIC membranes.
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26
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Brown MS, Radhakrishnan A, Goldstein JL. Retrospective on Cholesterol Homeostasis: The Central Role of Scap. Annu Rev Biochem 2017; 87:783-807. [PMID: 28841344 DOI: 10.1146/annurev-biochem-062917-011852] [Citation(s) in RCA: 302] [Impact Index Per Article: 43.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Scap is a polytopic membrane protein that functions as a molecular machine to control the cholesterol content of membranes in mammalian cells. In the 21 years since our laboratory discovered Scap, we have learned how it binds sterol regulatory element-binding proteins (SREBPs) and transports them from the endoplasmic reticulum (ER) to the Golgi for proteolytic processing. Proteolysis releases the SREBP transcription factor domains, which enter the nucleus to promote cholesterol synthesis and uptake. When cholesterol in ER membranes exceeds a threshold, the sterol binds to Scap, triggering several conformational changes that prevent the Scap-SREBP complex from leaving the ER. As a result, SREBPs are no longer processed, cholesterol synthesis and uptake are repressed, and cholesterol homeostasis is restored. This review focuses on the four domains of Scap that undergo concerted conformational changes in response to cholesterol binding. The data provide a molecular mechanism for the control of lipids in cell membranes.
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Affiliation(s)
- Michael S Brown
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA; ;
| | - Arun Radhakrishnan
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA; ;
| | - Joseph L Goldstein
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA; ;
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27
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Luchetti F, Crinelli R, Cesarini E, Canonico B, Guidi L, Zerbinati C, Di Sario G, Zamai L, Magnani M, Papa S, Iuliano L. Endothelial cells, endoplasmic reticulum stress and oxysterols. Redox Biol 2017; 13:581-587. [PMID: 28783588 PMCID: PMC5545768 DOI: 10.1016/j.redox.2017.07.014] [Citation(s) in RCA: 92] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 07/21/2017] [Accepted: 07/28/2017] [Indexed: 12/13/2022] Open
Abstract
Oxysterols are bioactive lipids that act as regulators of lipid metabolism, inflammation, cell viability and are involved in several diseases, including atherosclerosis. Mounting evidence linked the atherosclerosis to endothelium dysfunction; in fact, the endothelium regulates the vascular system with roles in processes such as hemostasis, cell cholesterol, hormone trafficking, signal transduction and inflammation. Several papers shed light the ability of oxysterols to induce apoptosis in different cell lines including endothelial cells. Apoptotic endothelial cell and endothelial denudation may constitute a critical step in the transition to plaque erosion and vessel thrombosis, so preventing the endothelial damaged has garnered considerable attention as a novel means of treating atherosclerosis. Endoplasmic reticulum (ER) is the site where the proteins are synthetized and folded and is necessary for most cellular activity; perturbations of ER homeostasis leads to a condition known as endoplasmic reticulum stress. This condition evokes the unfolded protein response (UPR) an adaptive pathway that aims to restore ER homeostasis. Mounting evidence suggests that chronic activation of UPR leads to cell dysfunction and death and recently has been implicated in pathogenesis of endothelial dysfunction. Autophagy is an essential catabolic mechanism that delivers misfolded proteins and damaged organelles to the lysosome for degradation, maintaining basal levels of autophagic activity it is critical for cell survival. Several evidence suggests that persistent ER stress often results in stimulation of autophagic activities, likely as a compensatory mechanism to relieve ER stress and consequently cell death. In this review, we summarize evidence for the effect of oxysterols on endothelial cells, especially focusing on oxysterols-mediated induction of endoplasmic reticulum stress. Endothelial cells dysfunction is critical in the process of atherothrombosis. Endoplasmic reticulum stress is a key component in endothelial cell dysfunction. Oxysterols are oxidation products of cholesterol found in atherosclerosis lesions. Oxysterols are potential modulators of endoplasmic reticulum stress.
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Affiliation(s)
- F Luchetti
- Departments of Biomolecular Sciences, University of Urbino Carlo Bo, Urbino, Italy.
| | - R Crinelli
- Departments of Biomolecular Sciences, University of Urbino Carlo Bo, Urbino, Italy
| | - E Cesarini
- Departments of Biomolecular Sciences, University of Urbino Carlo Bo, Urbino, Italy
| | - B Canonico
- Departments of Biomolecular Sciences, University of Urbino Carlo Bo, Urbino, Italy
| | - L Guidi
- Departments of Biomolecular Sciences, University of Urbino Carlo Bo, Urbino, Italy
| | - C Zerbinati
- Department of Medico-Surgical Sciences and Biotechnologies Vascular Biology, Atherothrombosis & Mass Spectrometry, Sapienza University of Rome, Latina, Italy
| | - G Di Sario
- Departments of Biomolecular Sciences, University of Urbino Carlo Bo, Urbino, Italy
| | - L Zamai
- Departments of Biomolecular Sciences, University of Urbino Carlo Bo, Urbino, Italy
| | - M Magnani
- Departments of Biomolecular Sciences, University of Urbino Carlo Bo, Urbino, Italy
| | - S Papa
- Departments of Biomolecular Sciences, University of Urbino Carlo Bo, Urbino, Italy
| | - L Iuliano
- Department of Medico-Surgical Sciences and Biotechnologies Vascular Biology, Atherothrombosis & Mass Spectrometry, Sapienza University of Rome, Latina, Italy
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28
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Ru P, Guo D. microRNA-29 mediates a novel negative feedback loop to regulate SCAP/SREBP-1 and lipid metabolism. RNA & DISEASE 2017; 4. [PMID: 28664184 DOI: 10.14800/rd.1525] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The membrane-bound transcription factors, SREBPs (sterol regulatory element-binding proteins), play a central role in regulating lipid metabolism. The transcriptional activation of SREBPs requires the key protein SCAP (SREBP-cleavage activating protein) to translocate their precursors from the endoplasmic reticulum to the Golgi for subsequent proteolytic activation, a process tightly regulated by a cholesterol-mediated negative feedback loop. Our previous work showed that the SCAP/SREBP-1 pathway is significantly upregulated in human glioblastoma (GBM), the most deadly brain cancer, and that glucose-mediated N-glycosylation of SCAP is a prerequisite step for SCAP/SREBP trafficking. More recently, we demonstrated that microRNA-29 (miR-29) mediates a previously unrecognized negative feedback loop in SCAP/SREBP-1 signaling to control lipid metabolism. We found that SREBP-1, functioning as a transcription factor, promotes the expression of the miR-29 family members, miR-29a, -29b and -29c. In turn, the miR-29 isoforms reversely repress the expression of SCAP and SREBP-1. Moreover, treatment with miR-29 mimics effectively suppressed GBM tumor growth by inhibiting SCAP/SREBP-1 and de novo lipid synthesis. These findings, recently published in Cell Reports, strongly suggest that delivery of miR-29 in vivo may be a promising approach to treat cancer and metabolic diseases by suppressing SCAP/SREBP-1-regulated lipid metabolism.
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Affiliation(s)
- Peng Ru
- Department of Radiation Oncology, The Ohio State University James Comprehensive Cancer Center and College of Medicine, Columbus, OH 43210, USA
| | - Deliang Guo
- Department of Radiation Oncology, The Ohio State University James Comprehensive Cancer Center and College of Medicine, Columbus, OH 43210, USA
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29
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Giampietro C, Lionetti MC, Costantini G, Mutti F, Zapperi S, La Porta CAM. Cholesterol impairment contributes to neuroserpin aggregation. Sci Rep 2017; 7:43669. [PMID: 28255164 PMCID: PMC5334643 DOI: 10.1038/srep43669] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Accepted: 01/27/2017] [Indexed: 01/05/2023] Open
Abstract
Intraneural accumulation of misfolded proteins is a common feature of several neurodegenerative pathologies including Alzheimer's and Parkinson's diseases, and Familial Encephalopathy with Neuroserpin Inclusion Bodies (FENIB). FENIB is a rare disease due to a point mutation in neuroserpin which accelerates protein aggregation in the endoplasmic reticulum (ER). Here we show that cholesterol depletion induced either by prolonged exposure to statins or by inhibiting the sterol reg-ulatory binding-element protein (SREBP) pathway also enhances aggregation of neuroserpin proteins. These findings can be explained considering a computational model of protein aggregation under non-equilibrium conditions, where a decrease in the rate of protein clearance improves aggregation. Decreasing cholesterol in cell membranes affects their biophysical properties, including their ability to form the vesicles needed for protein clearance, as we illustrate by a simple mathematical model. Taken together, these results suggest that cholesterol reduction induces neuroserpin aggregation, even in absence of specific neuroserpin mutations. The new mechanism we uncover could be relevant also for other neurodegenerative diseases associated with protein aggregation.
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Affiliation(s)
| | - Maria Chiara Lionetti
- Center for Complexity and Biosystems, Department of Biosciences, University of Milano, via Celoria 26, 20133 Milano, Italy
| | - Giulio Costantini
- Center for Complexity and Biosystems, Department of Physics, University of Milano, via Celoria 16, 20133 Milano, Italy
| | - Federico Mutti
- Center for Complexity and Biosystems, Department of Biosciences, University of Milano, via Celoria 26, 20133 Milano, Italy
| | - Stefano Zapperi
- Center for Complexity and Biosystems, Department of Physics, University of Milano, via Celoria 16, 20133 Milano, Italy
- CNR - Consiglio Nazionale delle Ricerche, Istituto di Chimica della Materia Condensata e di Tecnologie per l’Energia, Via R. Cozzi 53, 20125 Milano, Italy
- ISI Foundation, Via Alassio 11C, Torino, Italy
- Department of Applied Physics, Aalto University, P.O. Box 14100, FIN-00076, Aalto, Finland
| | - Caterina A. M. La Porta
- Center for Complexity and Biosystems, Department of Biosciences, University of Milano, via Celoria 26, 20133 Milano, Italy
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30
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Biwer LA, Isakson BE. Endoplasmic reticulum-mediated signalling in cellular microdomains. Acta Physiol (Oxf) 2017; 219:162-175. [PMID: 26973141 DOI: 10.1111/apha.12675] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Revised: 12/01/2015] [Accepted: 03/01/2016] [Indexed: 12/17/2022]
Abstract
The endoplasmic reticulum (ER) is a prime mediator of cellular signalling due to its functions as an internal cellular store for calcium, as well as a site for synthesis of proteins and lipids. Its peripheral network of sheets and tubules facilitates calcium and lipid signalling, especially in areas of the cell that are more distant to the main cytoplasmic network. Specific membrane proteins shape the peripheral ER architecture and influence the network stability to project into restricted spaces. The signalling microdomains are anatomically separate from the cytoplasm as a whole and exhibit localized protein, ion channel and cytoskeletal element expression. Signalling can also occur between the ER and other organelles, such as the Golgi or mitochondria. Lipids made in the ER membrane can be sent to the Golgi via specialized transfer proteins and specific phospholipid synthases are enriched at ER-mitochondria junctions to more efficiently expedite phospholipid transfer. As a hub for protein and lipid synthesis, a store for intracellular calcium [Ca2+ ]i and a mediator of cellular stress, the ER is an important cellular organelle. Its ability to organize into tubules and project into restricted spaces allows for discrete and temporal signalling, which is important for cellular physiology and organism homoeostasis.
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Affiliation(s)
- L. A. Biwer
- Department of Molecular Physiology and Biophysics; University of Virginia; Charlottesville VA USA
- Robert M. Berne Cardiovascular Research Center; University of Virginia School of Medicine; Charlottesville VA USA
| | - B. E. Isakson
- Department of Molecular Physiology and Biophysics; University of Virginia; Charlottesville VA USA
- Robert M. Berne Cardiovascular Research Center; University of Virginia School of Medicine; Charlottesville VA USA
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31
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Li J, Wang X, Yuan Y, Long X, Bao J, Li X. An in vitro test system for evaluation of SCAP–SREBP pathway inhibitory activities of Traditional Chinese Medicines. RSC Adv 2017. [DOI: 10.1039/c7ra09521j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
In vitro assay system demonstrates that Rhizoma Alismatis and Semen Cassiae show beneficial effects on inhibition of SCAP–SREBP pathway activities.
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Affiliation(s)
- Jianzong Li
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education
- College of Life Sciences
- Sichuan University
- Chengdu 610065
- P. R. China
| | - Xin Wang
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education
- College of Life Sciences
- Sichuan University
- Chengdu 610065
- P. R. China
| | - Yuan Yuan
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education
- College of Life Sciences
- Sichuan University
- Chengdu 610065
- P. R. China
| | - Xin Long
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education
- College of Life Sciences
- Sichuan University
- Chengdu 610065
- P. R. China
| | - Jinku Bao
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education
- College of Life Sciences
- Sichuan University
- Chengdu 610065
- P. R. China
| | - Xin Li
- State Key Laboratory of Oral Diseases
- National Clinical Research Center for Oral Diseases
- West China Hospital of Stomatology
- Sichuan University
- Chengdu
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32
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Cheng C, Guo JY, Geng F, Wu X, Cheng X, Li Q, Guo D. Analysis of SCAP N-glycosylation and Trafficking in Human Cells. J Vis Exp 2016. [PMID: 27911384 DOI: 10.3791/54709] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Elevated lipogenesis is a common characteristic of cancer and metabolic diseases. Sterol regulatory element-binding proteins (SREBPs), a family of membrane-bound transcription factors controlling the expression of genes important for the synthesis of cholesterol, fatty acids and phospholipids, are frequently upregulated in these diseases. In the process of SREBP nuclear translocation, SREBP-cleavage activating protein (SCAP) plays a central role in the trafficking of SREBP from the endoplasmic reticulum (ER) to the Golgi and in subsequent proteolysis activation. Recently, we uncovered that glucose-mediated N-glycosylation of SCAP is a prerequisite condition for the exit of SCAP/SREBP from the ER and movement to the Golgi. N-glycosylation stabilizes SCAP and directs SCAP/SREBP trafficking. Here, we describe a protocol for the isolation of membrane fractions in human cells and for the preparation of the samples for the detection of SCAP N-glycosylation and total protein by using western blot. We further provide a method to monitor SCAP trafficking by using confocal microscopy. This protocol is appropriate for the investigation of SCAP N-glycosylation and trafficking in mammalian cells.
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Affiliation(s)
- Chunming Cheng
- Department of Radiation Oncology, The Ohio State University Comprehensive Cancer Center and College of Medicine
| | - Jeffrey Yunhua Guo
- Department of Radiation Oncology, The Ohio State University Comprehensive Cancer Center and College of Medicine
| | - Feng Geng
- Department of Radiation Oncology, The Ohio State University Comprehensive Cancer Center and College of Medicine
| | - Xiaoning Wu
- Department of Radiation Oncology, The Ohio State University Comprehensive Cancer Center and College of Medicine
| | - Xiang Cheng
- Department of Radiation Oncology, The Ohio State University Comprehensive Cancer Center and College of Medicine
| | - Qiyue Li
- Department of Radiation Oncology, The Ohio State University Comprehensive Cancer Center and College of Medicine
| | - Deliang Guo
- Department of Radiation Oncology, The Ohio State University Comprehensive Cancer Center and College of Medicine;
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Zheng ZG, Zhou YP, Zhang X, Thu PM, Xie ZS, Lu C, Pang T, Xue B, Xu DQ, Chen Y, Chen XW, Li HJ, Xu X. Anhydroicaritin improves diet-induced obesity and hyperlipidemia and alleviates insulin resistance by suppressing SREBPs activation. Biochem Pharmacol 2016; 122:42-61. [PMID: 27816546 DOI: 10.1016/j.bcp.2016.10.016] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Accepted: 10/31/2016] [Indexed: 11/24/2022]
Abstract
SREBPs play important roles in the regulation of lipid metabolism, and are closely related to the occurrence and development of many metabolic diseases. Small molecular inhibitors of SERBPs are important tools in developing efficient treatment of metabolic diseases. However, there are no listing drug targeting SREBPs. Therefore, there is an urgent need to develop highly specific small molecules that inhibit SREBPs. In this study, using a hepatocyte-based high-throughput screening, we identified anhydroicaritin (AHI) as a novel inhibitor of SREBPs. HepG2, HL-7702, and human primary hepatocytes were used to verify the effects of AHI. We explored the mechanism by which AHI blocks the binding of SCAP/SREBPs complex with Sec23α/24D via regulating LKB1/AMPK/mTOR pathway. AHI reduced liver cell lipid level by preventing de novo lipogenesis. In diet induced obese mice, AHI ameliorated obesity, insulin resistance, fatty accumulation in liver and hyperlipemia. In conclusion, AHI improves diet-induced obesity and alleviates insulin resistance by suppressing SREBPs maturation which is dependent on LKB1/AMPK/mTOR pathway. Thus, AHI can serve as a leading compound for pharmacological control of metabolic diseases.
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Affiliation(s)
- Zu-Guo Zheng
- State Key Laboratory of Natural Medicines, China Pharmaceutical University, 210009 Nanjing, Jiangsu, China
| | - Ya-Ping Zhou
- State Key Laboratory of Natural Medicines, China Pharmaceutical University, 210009 Nanjing, Jiangsu, China
| | - Xin Zhang
- State Key Laboratory of Natural Medicines, China Pharmaceutical University, 210009 Nanjing, Jiangsu, China
| | - Pyone Myat Thu
- State Key Laboratory of Natural Medicines, China Pharmaceutical University, 210009 Nanjing, Jiangsu, China
| | - Zhi-Shen Xie
- State Key Laboratory of Natural Medicines, China Pharmaceutical University, 210009 Nanjing, Jiangsu, China
| | - Chong Lu
- State Key Laboratory of Natural Medicines, China Pharmaceutical University, 210009 Nanjing, Jiangsu, China
| | - Tao Pang
- State Key Laboratory of Natural Medicines, China Pharmaceutical University, 210009 Nanjing, Jiangsu, China; Jiangsu Key Laboratory of Drug Discovery for Metabolic Diseases, China Pharmaceutical University, 210009 Nanjing, Jiangsu, China
| | - Bin Xue
- State Key Laboratory of Pharmaceutical Biotechnology and Jiangsu Key Laboratory of Molecular Medicine and School of Medicine, Nanjing University, 210093 Nanjing, Jiangsu, China
| | - Da-Qian Xu
- Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences (SIBS), Chinese Academy of Sciences, 200031 Shanghai, China
| | - Yan Chen
- Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences (SIBS), Chinese Academy of Sciences, 200031 Shanghai, China
| | - Xiao-Wei Chen
- Institute of Molecular Medicine, Peking University, 100871 Beijing, China
| | - Hui-Jun Li
- State Key Laboratory of Natural Medicines, China Pharmaceutical University, 210009 Nanjing, Jiangsu, China.
| | - Xiaojun Xu
- State Key Laboratory of Natural Medicines, China Pharmaceutical University, 210009 Nanjing, Jiangsu, China; Jiangsu Key Laboratory of Drug Discovery for Metabolic Diseases, China Pharmaceutical University, 210009 Nanjing, Jiangsu, China.
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34
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Wen G, Pachner LI, Gessner DK, Eder K, Ringseis R. Sterol regulatory element-binding proteins are regulators of the sodium/iodide symporter in mammary epithelial cells. J Dairy Sci 2016; 99:9211-9226. [PMID: 27614840 DOI: 10.3168/jds.2016-11174] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Accepted: 07/17/2016] [Indexed: 12/29/2022]
Abstract
The sodium/iodide symporter (NIS), which is essential for iodide concentration in the thyroid, is reported to be transcriptionally regulated by sterol regulatory element-binding proteins (SREBP) in rat FRTL-5 thyrocytes. The SREBP are strongly activated after parturition and throughout lactation in the mammary gland of cattle and are important for mammary epithelial cell synthesis of milk lipids. In this study, we tested the hypothesis that the NIS gene is regulated also by SREBP in mammary epithelial cells, in which NIS is functionally expressed during lactation. Regulation of NIS expression and iodide uptake was investigated by means of inhibition, silencing, and overexpression of SREBP and by reporter gene and DNA-binding assays. As a mammary epithelial cell model, the human MCF-7 cell line, a breast adenocarcinoma cell line, which shows inducible expression of NIS by all-trans retinoic acid (ATRA), and unlike bovine mammary epithelial cells, is widely used to investigate the regulation of mammary gland NIS and NIS-specific iodide uptake, was used. Inhibition of SREBP maturation by treatment with 25-hydroxycholesterol (5 µM) for 48h reduced ATRA (1 µM)-induced mRNA concentration of NIS and iodide uptake in MCF-7 cells by approximately 20%. Knockdown of SREBP-1c and SREBP-2 by RNA interference decreased the mRNA and protein concentration of NIS by 30 to 50% 48h after initiating knockdown, whereas overexpression of nuclear SREBP (nSREBP)-1c and nSREBP-2 increased the expression of NIS in MCF-7 cells by 45 to 60%, respectively, 48h after initiating overexpression. Reporter gene experiments with varying length of NIS promoter reporter constructs revealed that the NIS 5'-flanking region is activated by nSREBP-1c and nSREBP-2 approximately 1.5- and 4.5-fold, respectively, and activation involves a SREBP-binding motif (SRE) at -38 relative to the transcription start site of the NIS gene. Gel shift assays using oligonucleotides spanning either the wild-type or the mutated SRE at -38 of the NIS 5'-flanking region showed that in vitro-translated nSREBP-1c and nSREBP-2 bind only the wild-type but not the mutated SRE at -38 of NIS. Collectively, the present results from cell culture experiments with human mammary epithelial MCF-7 cells and from genetic studies show for the first time that the NIS gene and iodide uptake are regulated by SREBP in cultured human mammary epithelial cells. Future studies are necessary to clarify if the regulation of NIS expression and iodide uptake by SREBP also applies to the lactating bovine mammary epithelium.
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Affiliation(s)
- G Wen
- Institute of Animal Nutrition and Nutrition Physiology, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 26-32, 35392 Gießen, Germany
| | - L I Pachner
- Institute of Animal Nutrition and Nutrition Physiology, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 26-32, 35392 Gießen, Germany
| | - D K Gessner
- Institute of Animal Nutrition and Nutrition Physiology, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 26-32, 35392 Gießen, Germany
| | - K Eder
- Institute of Animal Nutrition and Nutrition Physiology, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 26-32, 35392 Gießen, Germany
| | - R Ringseis
- Institute of Animal Nutrition and Nutrition Physiology, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 26-32, 35392 Gießen, Germany.
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35
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SCAP/SREBP pathway is required for the full steroidogenic response to cyclic AMP. Proc Natl Acad Sci U S A 2016; 113:E5685-93. [PMID: 27601673 DOI: 10.1073/pnas.1611424113] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Luteinizing hormone (LH) stimulates steroidogenesis largely through a surge in cyclic AMP (cAMP). Steroidogenic rates are also critically dependent on the availability of cholesterol at mitochondrial sites of synthesis. This cholesterol is provided by cellular uptake of lipoproteins, mobilization of intracellular lipid, and de novo synthesis. Whether and how these pathways are coordinated by cAMP are poorly understood. Recent phosphoproteomic analyses of cAMP-dependent phosphorylation sites in MA10 Leydig cells suggested that cAMP regulates multiple steps in these processes, including activation of the SCAP/SREBP pathway. SCAP [sterol-regulatory element-binding protein (SREBP) cleavage-activating protein] acts as a cholesterol sensor responsible for regulating intracellular cholesterol balance. Its role in cAMP-mediated control of steroidogenesis has not been explored. We used two CRISPR (clustered regularly interspaced short palindromic repeat)-Cas9 (CRISPR associated protein 9) knockout approaches to test the role of SCAP in steroidogenesis. Our results demonstrate that SCAP is required for progesterone production induced by concurrent inhibition of the cAMP phosphodiesterases PDE4 and PDE8. These inhibitors increased SCAP phosphorylation, SREBP2 activation, and subsequent expression of cholesterol biosynthetic genes, whereas SCAP deficiency largely prevented these effects. Reexpression of SCAP in SCAP-deficient cells restored SREBP2 protein expression and partially restored steroidogenic responses, confirming the requirement of SCAP-SREBP2 in steroidogenesis. Inhibitors of 3-hydroxy-3-methylglutaryl-Coenzyme A reductase and isoprenylation attenuated, whereas exogenously provided cholesterol augmented, PDE inhibitor-induced steroidogenesis, suggesting that the cholesterol substrate needed for steroidogenesis is provided by both de novo synthesis and isoprenylation-dependent mechanisms. Overall, these results demonstrate a novel role for LH/cAMP in SCAP/SREBP activation and subsequent regulation of steroidogenesis.
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36
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Shao W, Machamer CE, Espenshade PJ. Fatostatin blocks ER exit of SCAP but inhibits cell growth in a SCAP-independent manner. J Lipid Res 2016; 57:1564-73. [PMID: 27324795 DOI: 10.1194/jlr.m069583] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Indexed: 12/30/2022] Open
Abstract
Sterol regulatory element-binding protein (SREBP) transcription factors are central regulators of cellular lipid homeostasis and activate expression of genes required for fatty acid, triglyceride, and cholesterol synthesis and uptake. SREBP cleavage activating protein (SCAP) plays an essential role in SREBP activation by mediating endoplasmic reticulum (ER)-to-Golgi transport of SREBP. In the Golgi, membrane-bound SREBPs are cleaved sequentially by the site-1 and site-2 proteases. Recent studies have shown a requirement for the SREBP pathway in the development of fatty liver disease and tumor growth, making SCAP a target for drug development. Fatostatin is a chemical inhibitor of the SREBP pathway that directly binds SCAP and blocks its ER-to-Golgi transport. In this study, we determined that fatostatin blocks ER exit of SCAP and showed that inhibition is independent of insulin-induced gene proteins, which function to retain the SCAP-SREBP complex in the ER. Fatostatin potently inhibited cell growth, but unexpectedly exogenous lipids failed to rescue proliferation of fatostatin-treated cells. Furthermore, fatostatin inhibited growth of cells lacking SCAP Using a vesicular stomatitis virus glycoprotein (VSVG) trafficking assay, we demonstrated that fatostatin delays ER-to-Golgi transport of VSVG. In summary, fatostatin inhibited SREBP activation, but fatostatin additionally inhibited cell proliferation through both lipid-independent and SCAP-independent mechanisms, possibly by general inhibition of ER-to-Golgi transport.
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Affiliation(s)
- Wei Shao
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Carolyn E Machamer
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Peter J Espenshade
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
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37
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Wen G, Eder K, Ringseis R. Sterol regulatory element-binding proteins are transcriptional regulators of the thyroglobulin gene in thyroid cells. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2016; 1859:994-1003. [PMID: 27321819 DOI: 10.1016/j.bbagrm.2016.06.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Revised: 05/24/2016] [Accepted: 06/15/2016] [Indexed: 01/13/2023]
Abstract
The genes encoding sodium/iodide symporter (NIS) and thyroid peroxidase (TPO), both of which are essential for thyroid hormone (TH) synthesis, were shown to be regulated by sterol regulatory element-binding proteins (SREBP)-1c and -2. In the present study we tested the hypothesis that transcription of a further gene essential for TH synthesis, the thyroglobulin (TG) gene, is under the control of SREBP. To test this hypothesis, we studied the influence of inhibition of SREBP maturation and SREBP knockdown on TG expression in FRTL-5 thyrocytes and explored transcriptional regulation of the TG promoter by reporter gene experiments in FRTL-5 and HepG2 cells, gel shift assays and chromatin immunoprecipitation. Inhibition of SREBP maturation by 25-hydroxycholesterol and siRNA-mediated knockdown of either SREBP-1c or SREBP-2 decreased mRNA and protein levels of TG in FRTL-5 thyrocytes. Reporter gene assays with wild-type and mutated TG promoter reporter truncation constructs revealed that the rat TG promoter is transcriptionally activated by nSREBP-1c and nSREBP-2. DNA-binding assays and chromatin immunoprecipitation assays showed that both nSREBP-1c and nSREBP-2 bind to a SREBP binding motif with characteristics of an E-box SRE at position -63 in the rat TG promoter. In connection with recent findings that NIS and TPO are regulated by SREBP in thyrocytes the present findings support the view that SREBP are regulators of essential steps of TH synthesis in the thyroid gland such as iodide uptake, iodide oxidation and iodination of tyrosyl residues of TG. This moreover suggests that SREBP may be molecular targets for pharmacological modulation of TH synthesis.
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Affiliation(s)
- Gaiping Wen
- Institute of Animal Nutrition and Nutrition Physiology, Justus-Liebig-University Gießen, 35392 Gießen, Germany
| | - Klaus Eder
- Institute of Animal Nutrition and Nutrition Physiology, Justus-Liebig-University Gießen, 35392 Gießen, Germany
| | - Robert Ringseis
- Institute of Animal Nutrition and Nutrition Physiology, Justus-Liebig-University Gießen, 35392 Gießen, Germany.
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38
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Zhang Y, Ma KL, Ruan XZ, Liu BC. Dysregulation of the Low-Density Lipoprotein Receptor Pathway Is Involved in Lipid Disorder-Mediated Organ Injury. Int J Biol Sci 2016; 12:569-79. [PMID: 27019638 PMCID: PMC4807419 DOI: 10.7150/ijbs.14027] [Citation(s) in RCA: 86] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Accepted: 02/26/2016] [Indexed: 12/12/2022] Open
Abstract
The low-density lipoprotein receptor (LDLR) pathway is a negative feedback system that plays important roles in the regulation of plasma and intracellular cholesterol homeostasis. To maintain a cholesterol homeostasis, LDLR expression is tightly regulated by sterol regulatory element-binding protein-2 (SREBP-2) and SREBP cleavage-activating protein (SCAP) in transcriptional level and by proprotein convertase subtilisin/kexin type 9 (PCSK9) in posttranscriptional level. The dysregulation of LDLR expression results in abnormal lipid accumulation in cells and tissues, such as vascular smooth muscle cells, hepatic cells, renal mesangial cells, renal tubular cells and podocytes. It has been demonstrated that inflammation, renin-angiotensin system (RAS) activation, and hyperglycemia induce the disruption of LDLR pathway, which might contribute to lipid disorder-mediated organ injury (atherosclerosis, non-alcoholic fatty liver disease, kidney fibrosis, etc). The mammalian target of rapamycin (mTOR) pathway is a critical mediator in the disruption of LDLR pathway caused by pathogenic factors. The mTOR complex1 activation upregulates LDLR expression at the transcriptional and posttranscriptional levels, consequently resulting in lipid deposition. This paper mainly reviews the mechanisms for the dysregulation of LDLR pathway and its roles in lipid disorder-mediated organ injury under various pathogenic conditions. Understanding these mechanisms leading to the abnormality of LDLR expression contributes to find potential new drug targets in lipid disorder-mediated diseases.
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Miyata S, Inoue J, Shimizu M, Sato R. Allyl isothiocyanate suppresses the proteolytic activation of sterol regulatory element-binding proteins and de novo fatty acid and cholesterol synthesis. Biosci Biotechnol Biochem 2016; 80:1006-11. [PMID: 26822063 DOI: 10.1080/09168451.2015.1132154] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Sterol regulatory element-binding proteins (SREBPs) are a family of transcription factors that regulate lipid homeostasis by controlling the expression of genes involved in fatty acid and cholesterol synthesis. In this study, we used a stable cell line that expresses a luciferase reporter gene driven by an SRE-containing fatty acid synthase promoter to identify allyl isothiocyanate (AITC), one of the major isothiocyanates in cruciferous vegetables, as a novel SREBP inactivator. We found that AITC downregulated the proteolytic processing of SREBPs and the expression of their target genes in human hepatoma Huh-7 cells. Furthermore, AITC reduced the de novo synthesis of both fatty acids and cholesterol. Our results indicate a novel physiological function of AITC in lipid metabolism regulation.
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Affiliation(s)
- Shingo Miyata
- a Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences , The University of Tokyo , Japan
| | - Jun Inoue
- a Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences , The University of Tokyo , Japan
| | - Makoto Shimizu
- a Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences , The University of Tokyo , Japan
| | - Ryuichiro Sato
- a Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences , The University of Tokyo , Japan
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40
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Ren R, Zhou X, He Y, Ke M, Wu J, Liu X, Yan C, Wu Y, Gong X, Lei X, Yan SF, Radhakrishnan A, Yan N. PROTEIN STRUCTURE. Crystal structure of a mycobacterial Insig homolog provides insight into how these sensors monitor sterol levels. Science 2015; 349:187-91. [PMID: 26160948 DOI: 10.1126/science.aab1091] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Insulin-induced gene 1 (Insig-1) and Insig-2 are endoplasmic reticulum membrane-embedded sterol sensors that regulate the cellular accumulation of sterols. Despite their physiological importance, the structural information on Insigs remains limited. Here we report the high-resolution structures of MvINS, an Insig homolog from Mycobacterium vanbaalenii. MvINS exists as a homotrimer. Each protomer comprises six transmembrane segments (TMs), with TM3 and TM4 contributing to homotrimerization. The six TMs enclose a V-shaped cavity that can accommodate a diacylglycerol molecule. A homology-based structural model of human Insig-2, together with biochemical characterizations, suggest that the central cavity of Insig-2 accommodates 25-hydroxycholesterol, whereas TM3 and TM4 engage in Scap binding. These analyses provide an important framework for further functional and mechanistic understanding of Insig proteins and the sterol regulatory element-binding protein pathway.
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Affiliation(s)
- Ruobing Ren
- State Key Laboratory of Membrane Biology, Tsinghua University, Beijing 100084, China. Center for Structural Biology, School of Life Sciences, School of Medicine, Tsinghua University, Beijing 100084, China. Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing 100084, China
| | - Xinhui Zhou
- State Key Laboratory of Membrane Biology, Tsinghua University, Beijing 100084, China. Center for Structural Biology, School of Life Sciences, School of Medicine, Tsinghua University, Beijing 100084, China. Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing 100084, China
| | - Yuan He
- State Key Laboratory of Membrane Biology, Tsinghua University, Beijing 100084, China. Center for Structural Biology, School of Life Sciences, School of Medicine, Tsinghua University, Beijing 100084, China. Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing 100084, China
| | - Meng Ke
- State Key Laboratory of Membrane Biology, Tsinghua University, Beijing 100084, China. Center for Structural Biology, School of Life Sciences, School of Medicine, Tsinghua University, Beijing 100084, China. Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing 100084, China
| | - Jianping Wu
- State Key Laboratory of Membrane Biology, Tsinghua University, Beijing 100084, China. Center for Structural Biology, School of Life Sciences, School of Medicine, Tsinghua University, Beijing 100084, China. Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing 100084, China
| | - Xiaohui Liu
- National Institute of Biological Sciences, Beijing 102206, China
| | - Chuangye Yan
- State Key Laboratory of Membrane Biology, Tsinghua University, Beijing 100084, China. Center for Structural Biology, School of Life Sciences, School of Medicine, Tsinghua University, Beijing 100084, China. Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing 100084, China
| | - Yixuan Wu
- State Key Laboratory of Membrane Biology, Tsinghua University, Beijing 100084, China. Center for Structural Biology, School of Life Sciences, School of Medicine, Tsinghua University, Beijing 100084, China. Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing 100084, China
| | - Xin Gong
- State Key Laboratory of Membrane Biology, Tsinghua University, Beijing 100084, China. Center for Structural Biology, School of Life Sciences, School of Medicine, Tsinghua University, Beijing 100084, China. Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing 100084, China
| | - Xiaoguang Lei
- National Institute of Biological Sciences, Beijing 102206, China
| | - S Frank Yan
- Molecular Design and Chemical Biology, Therapeutic Modalities, Roche Pharma Research and Early Development, Roche Innovation Center Shanghai, Shanghai 201203, China
| | - Arun Radhakrishnan
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046, USA
| | - Nieng Yan
- State Key Laboratory of Membrane Biology, Tsinghua University, Beijing 100084, China. Center for Structural Biology, School of Life Sciences, School of Medicine, Tsinghua University, Beijing 100084, China. Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing 100084, China
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41
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Miyata S, Inoue J, Shimizu M, Sato R. Xanthohumol Improves Diet-induced Obesity and Fatty Liver by Suppressing Sterol Regulatory Element-binding Protein (SREBP) Activation. J Biol Chem 2015; 290:20565-79. [PMID: 26140926 DOI: 10.1074/jbc.m115.656975] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Indexed: 02/02/2023] Open
Abstract
Sterol regulatory element-binding proteins (SREBPs) are key transcription factors that stimulate the expression of genes involved in fatty acid and cholesterol biosynthesis. Here, we demonstrate that a prenylated flavonoid in hops, xanthohumol (XN), is a novel SREBP inactivator that reduces the de novo synthesis of fatty acid and cholesterol. XN independently suppressed the maturation of SREBPs of insulin-induced genes in a manner different from sterols. Our results suggest that XN impairs the endoplasmic reticulum-to-Golgi translocation of the SREBP cleavage-activating protein (SCAP)-SREBP complex by binding to Sec23/24 and blocking SCAP/SREBP incorporation into common coated protein II vesicles. Furthermore, in diet-induced obese mice, dietary XN suppressed SREBP-1 target gene expression in the liver accompanied by a reduction of the mature form of hepatic SREBP-1, and it inhibited the development of obesity and hepatic steatosis. Altogether, our data suggest that XN attenuates the function of SREBP-1 by repressing its maturation and that it has the potential of becoming a nutraceutical food or pharmacological agent for improving metabolic syndrome.
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Affiliation(s)
- Shingo Miyata
- From the Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan
| | - Jun Inoue
- From the Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan
| | - Makoto Shimizu
- From the Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan
| | - Ryuichiro Sato
- From the Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan
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42
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Takashima K, Saitoh A, Funabashi T, Hirose S, Yagi C, Nozaki S, Sato R, Shin HW, Nakayama K. COPI-mediated retrieval of SCAP is crucial for regulating lipogenesis under basal and sterol-deficient conditions. J Cell Sci 2015; 128:2805-15. [PMID: 26092941 DOI: 10.1242/jcs.164137] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Accepted: 06/12/2015] [Indexed: 02/03/2023] Open
Abstract
Retrograde trafficking from the Golgi complex to endoplasmic reticulum (ER) through COPI-coated vesicles has been implicated in lipid homeostasis. Here, we find that a block in COPI-dependent retrograde trafficking promotes processing and nuclear translocation of sterol regulatory element binding proteins (SREBPs), and upregulates the expression of downstream genes that are involved in lipid biosynthesis. This elevation in SREBP processing and activation is not caused by mislocalization of S1P or S2P (also known as MBTPS1 and MBTPS2, respectively), two Golgi-resident endoproteases that are involved in SREBP processing, but instead by increased Golgi residence of SREBPs, leading to their increased susceptibility to processing by the endoproteases. Analyses using a processing-defective SREBP mutant suggest that a fraction of SREBP molecules undergo basal cycling between the ER and Golgi in complex with SREBP cleavage-activating protein (SCAP). Furthermore, we show that SCAP alone is retrieved from the Golgi and moves to the ER after processing of SREBP under sterol-deficient conditions. Thus, our observations indicate that COPI-mediated retrograde trafficking is crucial for preventing unnecessary SREBP activation, by retrieving the small amounts of SCAP-SREBP complex that escape from the sterol-regulated ER retention machinery, as well as for the reuse of SCAP.
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Affiliation(s)
- Kouhei Takashima
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan
| | - Akina Saitoh
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan
| | - Teruki Funabashi
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan
| | - Shohei Hirose
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan
| | - Chikako Yagi
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan
| | - Shohei Nozaki
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan
| | - Ryuichiro Sato
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan
| | - Hye-Won Shin
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan Career-Path Promotion Unit for Young Life Scientists, Kyoto University, Kyoto 606-8501, Japan
| | - Kazuhisa Nakayama
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan
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Phosphoregulatory protein 14-3-3 facilitates SAC1 transport from the endoplasmic reticulum. Proc Natl Acad Sci U S A 2015; 112:E3199-206. [PMID: 26056309 DOI: 10.1073/pnas.1509119112] [Citation(s) in RCA: 196] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Most secretory cargo proteins in eukaryotes are synthesized in the endoplasmic reticulum and actively exported in membrane-bound vesicles that are formed by the cytosolic coat protein complex II (COPII). COPII proteins are assisted by a variety of cargo-specific adaptor proteins required for the concentration and export of secretory proteins from the endoplasmic reticulum (ER). Adaptor proteins are key regulators of cargo export, and defects in their function may result in disease phenotypes in mammals. Here we report the role of 14-3-3 proteins as a cytosolic adaptor in mediating SAC1 transport in COPII-coated vesicles. Sac1 is a phosphatidyl inositol-4 phosphate (PI4P) lipid phosphatase that undergoes serum dependent translocation between the endoplasmic reticulum and Golgi complex and controls cellular PI4P lipid levels. We developed a cell-free COPII vesicle budding reaction to examine SAC1 exit from the ER that requires COPII and at least one additional cytosolic factor, the 14-3-3 protein. Recombinant 14-3-3 protein stimulates the packaging of SAC1 into COPII vesicles and the sorting subunit of COPII, Sec24, interacts with 14-3-3. We identified a minimal sorting motif of SAC1 that is important for 14-3-3 binding and which controls SAC1 export from the ER. This LS motif is part of a 7-aa stretch, RLSNTSP, which is similar to the consensus 14-3-3 binding sequence. Homology models, based on the SAC1 structure from yeast, predict this region to be in the exposed exterior of the protein. Our data suggest a model in which the 14-3-3 protein mediates SAC1 traffic from the ER through direct interaction with a sorting signal and COPII.
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Rauer C, Ringseis R, Rothe S, Wen G, Eder K. Sterol regulatory element-binding proteins are regulators of the rat thyroid peroxidase gene in thyroid cells. PLoS One 2014; 9:e91265. [PMID: 24625548 PMCID: PMC3953333 DOI: 10.1371/journal.pone.0091265] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Accepted: 02/07/2014] [Indexed: 01/21/2023] Open
Abstract
Sterol regulatory element-binding proteins (SREBPs)-1c and -2, which were initially discovered as master transcriptional regulators of lipid biosynthesis and uptake, were recently identified as novel transcriptional regulators of the sodium-iodide symporter gene in the thyroid, which is essential for thyroid hormone synthesis. Based on this observation that SREBPs play a role for thyroid hormone synthesis, we hypothesized that another gene involved in thyroid hormone synthesis, the thyroid peroxidase (TPO) gene, is also a target of SREBP-1c and -2. Thyroid epithelial cells treated with 25-hydroxycholesterol, which is known to inhibit SREBP activation, had about 50% decreased mRNA levels of TPO. Similarly, the mRNA level of TPO was reduced by about 50% in response to siRNA mediated knockdown of both, SREBP-1 and SREBP-2. Reporter gene assays revealed that overexpression of active SREBP-1c and -2 causes a strong transcriptional activation of the rat TPO gene, which was localized to an approximately 80 bp region in the intron 1 of the rat TPO gene. In vitro- and in vivo-binding of both, SREBP-1c and SREBP-2, to this region in the rat TPO gene could be demonstrated using gel-shift assays and chromatin immunoprecipitation. Mutation analysis of the 80 bp region of rat TPO intron 1 revealed two isolated and two overlapping SREBP-binding elements from which one, the overlapping SRE+609/InvSRE+614, was shown to be functional in reporter gene assays. In connection with recent findings that the rat NIS gene is also a SREBP target gene in the thyroid, the present findings suggest that SREBPs may be possible novel targets for pharmacological modulation of thyroid hormone synthesis.
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Affiliation(s)
- Christine Rauer
- Institute of Animal Nutrition and Nutrition Physiology, Justus-Liebig-Universität Gießen, Gießen, Germany
| | - Robert Ringseis
- Institute of Animal Nutrition and Nutrition Physiology, Justus-Liebig-Universität Gießen, Gießen, Germany
- * E-mail:
| | - Susanne Rothe
- Institute of Animal Nutrition and Nutrition Physiology, Justus-Liebig-Universität Gießen, Gießen, Germany
| | - Gaiping Wen
- Institute of Animal Nutrition and Nutrition Physiology, Justus-Liebig-Universität Gießen, Gießen, Germany
| | - Klaus Eder
- Institute of Animal Nutrition and Nutrition Physiology, Justus-Liebig-Universität Gießen, Gießen, Germany
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Influence of SREBP-2 and SCAP Gene Polymorphisms on Lipid-Lowering Response to Atorvastatin in a Cohort of Chilean Subjects with Amerindian Background. Mol Diagn Ther 2014; 18:435-43. [DOI: 10.1007/s40291-014-0094-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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46
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Shao W, Espenshade PJ. Sterol regulatory element-binding protein (SREBP) cleavage regulates Golgi-to-endoplasmic reticulum recycling of SREBP cleavage-activating protein (SCAP). J Biol Chem 2014; 289:7547-57. [PMID: 24478315 DOI: 10.1074/jbc.m113.545699] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Sterol regulatory element-binding protein (SREBP) transcription factors are central regulators of cellular lipogenesis. Release of membrane-bound SREBP requires SREBP cleavage-activating protein (SCAP) to escort SREBP from the endoplasmic reticulum (ER) to the Golgi for cleavage by site-1 and site-2 proteases. SCAP then recycles to the ER for additional rounds of SREBP binding and transport. Mechanisms regulating ER-to-Golgi transport of SCAP-SREBP are understood in molecular detail, but little is known about SCAP recycling. Here, we have demonstrated that SCAP Golgi-to-ER transport requires cleavage of SREBP at site-1. Reductions in SREBP cleavage lead to SCAP degradation in lysosomes, providing additional negative feedback control to the SREBP pathway. Current models suggest that SREBP plays a passive role prior to cleavage. However, we show that SREBP actively prevents premature recycling of SCAP-SREBP until initiation of SREBP cleavage. SREBP regulates SCAP in human cells and yeast, indicating that this is an ancient regulatory mechanism.
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Affiliation(s)
- Wei Shao
- From the Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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Fryer LGD, Jones B, Duncan EJ, Hutchison CE, Ozkan T, Williams PA, Alder O, Nieuwdorp M, Townley AK, Mensenkamp AR, Stephens DJ, Dallinga-Thie GM, Shoulders CC. The endoplasmic reticulum coat protein II transport machinery coordinates cellular lipid secretion and cholesterol biosynthesis. J Biol Chem 2013; 289:4244-61. [PMID: 24338480 PMCID: PMC3924288 DOI: 10.1074/jbc.m113.479980] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Triglycerides and cholesterol are essential for life in most organisms. Triglycerides serve as the principal energy storage depot and, where vascular systems exist, as a means of energy transport. Cholesterol is essential for the functional integrity of all cellular membrane systems. The endoplasmic reticulum is the site of secretory lipoprotein production and de novo cholesterol synthesis, yet little is known about how these activities are coordinated with each other or with the activity of the COPII machinery, which transports endoplasmic reticulum cargo to the Golgi. The Sar1B component of this machinery is mutated in chylomicron retention disorder, indicating that this Sar1 isoform secures delivery of dietary lipids into the circulation. However, it is not known why some patients with chylomicron retention disorder develop hepatic steatosis, despite impaired intestinal fat malabsorption, and why very severe hypocholesterolemia develops in this condition. Here, we show that Sar1B also promotes hepatic apolipoprotein (apo) B lipoprotein secretion and that this promoting activity is coordinated with the processes regulating apoB expression and the transfer of triglycerides/cholesterol moieties onto this large lipid transport protein. We also show that although Sar1A antagonizes the lipoprotein secretion-promoting activity of Sar1B, both isoforms modulate the expression of genes encoding cholesterol biosynthetic enzymes and the synthesis of cholesterol de novo. These results not only establish that Sar1B promotes the secretion of hepatic lipids but also adds regulation of cholesterol synthesis to Sar1B's repertoire of transport functions.
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Affiliation(s)
- Lee G D Fryer
- From the Endocrinology Centre, William Harvey Research Institute, Queen Mary University of London and Barts and The London School of Medicine and Dentistry, Charterhouse Square, London EC1M 6BQ, United Kingdom
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48
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la Cour JM, Schindler AJ, Berchtold MW, Schekman R. ALG-2 attenuates COPII budding in vitro and stabilizes the Sec23/Sec31A complex. PLoS One 2013; 8:e75309. [PMID: 24069399 PMCID: PMC3777911 DOI: 10.1371/journal.pone.0075309] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2013] [Accepted: 08/14/2013] [Indexed: 11/18/2022] Open
Abstract
Coated vesicles mediate the traffic of secretory and membrane cargo proteins from the endoplasmic reticulum (ER) to the Golgi apparatus. The coat protein complex (COPII) involved in vesicle budding is constituted by a GTPase, Sar1, the inner coat components of Sec23/Sec24 and the components of the outer coat Sec13/Sec31A. The Ca(2+)-binding protein ALG-2 was recently identified as a Sec31A binding partner and a possible link to Ca(2+) regulation of COPII vesicle budding. Here we show that ALG-2/Ca(2+) is capable of attenuating vesicle budding in vitro through interaction with an ALG-2 binding domain in the proline rich region of Sec31A. Binding of ALG-2 to Sec31A and inhibition of COPII vesicle budding is furthermore dependent on an intact Ca(2+)-binding site at EF-hand 1 of ALG-2. ALG-2 increased recruitment of COPII proteins Sec23/24 and Sec13/31A to artificial liposomes and was capable of mediating binding of Sec13/31A to Sec23. These results introduce a regulatory role for ALG-2/Ca(2+) in COPII tethering and vesicle budding.
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Affiliation(s)
- Jonas M. la Cour
- From the Department of Biology, University of Copenhagen, Copenhagen, Denmark
- * E-mail:
| | - Adam J. Schindler
- From the Biology Department, Duke University, Durham, North Carolina, United States of America
| | - Martin W. Berchtold
- From the Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Randy Schekman
- From the Department of Cellular Biochemistry, University of California at Berkeley, Berkeley, California, United States of America
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49
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Ringseis R, Rauer C, Rothe S, Gessner DK, Schütz LM, Luci S, Wen G, Eder K. Sterol regulatory element-binding proteins are regulators of the NIS gene in thyroid cells. Mol Endocrinol 2013; 27:781-800. [PMID: 23542164 DOI: 10.1210/me.2012-1269] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The uptake of iodide into the thyroid, an essential step in thyroid hormone synthesis, is an active process mediated by the sodium-iodide symporter (NIS). Despite its strong dependence on TSH, the master regulator of the thyroid, the NIS gene was also reported to be regulated by non-TSH signaling pathways. In the present study we provide evidence that the rat NIS gene is subject to regulation by sterol regulatory element-binding proteins (SREBPs), which were initially identified as master transcriptional regulators of lipid biosynthesis and uptake. Studies in FRTL-5 thyrocytes revealed that TSH stimulates expression and maturation of SREBPs and expression of classical SREBP target genes involved in lipid biosynthesis and uptake. Almost identical effects were observed when the cAMP agonist forskolin was used instead of TSH. In TSH receptor-deficient mice, in which TSH/cAMP-dependent gene regulation is blocked, the expression of SREBP isoforms in the thyroid was markedly reduced when compared with wild-type mice. Sterol-mediated inhibition of SREBP maturation and/or RNA interference-mediated knockdown of SREBPs reduced expression of NIS and NIS-specific iodide uptake in FRTL-5 cells. Conversely, overexpression of active SREBPs caused a strong activation of the 5'-flanking region of the rat NIS gene mediated by binding to a functional SREBP binding site located in the 5'-untranslated region of the rat NIS gene. These findings show that TSH acts as a regulator of SREBP expression and maturation in thyroid epithelial cells and that SREBPs are novel transcriptional regulators of NIS.
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Affiliation(s)
- Robert Ringseis
- Institute of Animal Nutrition and Nutrition Physiology, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 26-32, 35392 Gießen, Germany.
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50
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Faulkner RA, Nguyen AD, Jo Y, DeBose-Boyd RA. Lipid-regulated degradation of HMG-CoA reductase and Insig-1 through distinct mechanisms in insect cells. J Lipid Res 2013; 54:1011-22. [PMID: 23403031 PMCID: PMC3653402 DOI: 10.1194/jlr.m033639] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In mammalian cells, levels of the integral membrane proteins 3-hydroxy-3-methylglutaryl-CoA reductase and Insig-1 are controlled by lipid-regulated endoplasmic reticulum-associated degradation (ERAD). The ERAD of reductase slows a rate-limiting step in cholesterol synthesis and results from sterol-induced binding of its membrane domain to Insig-1 and the highly related Insig-2 protein. Insig binding bridges reductase to ubiquitin ligases that facilitate its ubiquitination, thereby marking the protein for cytosolic dislocation and proteasomal degradation. In contrast to reductase, Insig-1 is subjected to ERAD in lipid-deprived cells. Sterols block this ERAD by inhibiting Insig-1 ubiquitination, whereas unsaturated fatty acids block the reaction by preventing the protein's cytosolic dislocation. In previous studies, we found that the membrane domain of mammalian reductase was subjected to ERAD in Drosophila S2 cells. This ERAD was appropriately accelerated by sterols and required the action of Insigs, which bridged reductase to a Drosophila ubiquitin ligase. We now report reconstitution of mammalian Insig-1 ERAD in S2 cells. The ERAD of Insig-1 in S2 cells mimics the reaction that occurs in mammalian cells with regard to its inhibition by either sterols or unsaturated fatty acids. Genetic and pharmacologic manipulations coupled with subcellular fractionation indicate that Insig-1 and reductase are degraded through distinct mechanisms that are mediated by different ubiquitin ligase complexes. Together, these results establish Drosophila S2 cells as a model system to elucidate mechanisms through which lipid constituents of cell membranes (i.e., sterols and fatty acids) modulate the ERAD of Insig-1 and reductase.
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Affiliation(s)
- Rebecca A Faulkner
- Howard Hughes Medical Institute, Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046, USA
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