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Fang XX, Wei P, Zhao K, Sheng ZC, Song BL, Yin L, Luo J. Fatty acid-binding proteins 3, 7, and 8 bind cholesterol and facilitate its egress from lysosomes. J Cell Biol 2024; 223:e202211062. [PMID: 38429999 PMCID: PMC10909654 DOI: 10.1083/jcb.202211062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Revised: 03/22/2023] [Accepted: 01/18/2024] [Indexed: 03/03/2024] Open
Abstract
Cholesterol from low-density lipoprotein (LDL) can be transported to many organelle membranes by non-vesicular mechanisms involving sterol transfer proteins (STPs). Fatty acid-binding protein (FABP) 7 was identified in our previous study searching for new regulators of intracellular cholesterol trafficking. Whether FABP7 is a bona fide STP remains unknown. Here, we found that FABP7 deficiency resulted in the accumulation of LDL-derived cholesterol in lysosomes and reduced cholesterol levels on the plasma membrane. A crystal structure of human FABP7 protein in complex with cholesterol was resolved at 2.7 Å resolution. In vitro, FABP7 efficiently transported the cholesterol analog dehydroergosterol between the liposomes. Further, the silencing of FABP3 and 8, which belong to the same family as FABP7, caused robust cholesterol accumulation in lysosomes. These two FABP proteins could transport dehydroergosterol in vitro as well. Collectively, our results suggest that FABP3, 7, and 8 are a new class of STPs mediating cholesterol egress from lysosomes.
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Affiliation(s)
- Xian-Xiu Fang
- The Institute for Advanced Studies, College of Life Sciences, Hubei Key Laboratory of Cell Homeostasis, Taikang Center for Life and Medical Sciences, Taikang Medical School, Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan, China
| | - Pengcheng Wei
- The Institute for Advanced Studies, College of Life Sciences, Hubei Key Laboratory of Cell Homeostasis, Taikang Center for Life and Medical Sciences, Taikang Medical School, Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan, China
| | - Kai Zhao
- The Institute for Advanced Studies, College of Life Sciences, Hubei Key Laboratory of Cell Homeostasis, Taikang Center for Life and Medical Sciences, Taikang Medical School, Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan, China
| | - Zhao-Chen Sheng
- The Institute for Advanced Studies, College of Life Sciences, Hubei Key Laboratory of Cell Homeostasis, Taikang Center for Life and Medical Sciences, Taikang Medical School, Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan, China
| | - Bao-Liang Song
- The Institute for Advanced Studies, College of Life Sciences, Hubei Key Laboratory of Cell Homeostasis, Taikang Center for Life and Medical Sciences, Taikang Medical School, Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan, China
| | - Lei Yin
- The Institute for Advanced Studies, College of Life Sciences, Hubei Key Laboratory of Cell Homeostasis, Taikang Center for Life and Medical Sciences, Taikang Medical School, Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan, China
| | - Jie Luo
- The Institute for Advanced Studies, College of Life Sciences, Hubei Key Laboratory of Cell Homeostasis, Taikang Center for Life and Medical Sciences, Taikang Medical School, Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan, China
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Nam KH. Crystal structure of human brain-type fatty acid-binding protein FABP7 complexed with palmitic acid. ACTA CRYSTALLOGRAPHICA SECTION D-STRUCTURAL BIOLOGY 2021; 77:954-965. [PMID: 34196621 DOI: 10.1107/s2059798321005763] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 06/03/2021] [Indexed: 11/11/2022]
Abstract
The brain-type fatty acid-binding protein FABP7, which is expressed in astrocytes and neural progenitors, is a member of the intracellular lipid-binding protein family. This protein is not only involved in various cellular functions such as metabolism, inflammation and energy homeostasis, but also in diseases such as cognitive disorders and tumors. Structures of unsaturated fatty acids, such as oleic acid (OA) and docosahexaenoic acid (DHA), bound to FABP7 have been elucidated; however, structures of saturated fatty acids bound to FABP7 remain unknown. To better understand fatty acid recognition, here the crystal structure of human brain-type fatty acid-binding protein FABP7 complexed with palmitic acid (PA), a saturated fatty acid, is reported at a resolution of 1.6 Å. The PA bound to the fatty acid-binding pocket of FABP7 assumed a U-shaped conformation. The carboxylate moiety of PA interacted with Tyr129, Arg127 and, via a water bridge, with Arg107 and Thr54, whereas its aliphatic chain was stabilized by hydrophobic interactions with Met21, Leu24, Thr30, Thr37, Pro39, Phe58 and Asp77. Structural comparison showed that PA, OA and DHA exhibited unique binding conformations in the fatty acid-binding pocket, stabilized by distinct amino-acid interactions. The binding of PA to FABP7 exhibits a unique binding conformation when compared with other human FABPs (FABP3-FABP5 and FABP8) expressed in other tissues. Based on the crystal and fatty acid structures, it was suggested that PA, which prefers a linear form in nature, required a greater conformational change in its aliphatic chain to bind to the fatty acid-binding pocket in a U-shaped conformation, compared with the cis configurations of OA or DHA. This, together with the length of the aliphatic chain, was considered to be one of the factors determining the binding affinity of PA to FABP7. These results provide a better understanding of fatty acid recognition by FABP7 and expand the knowledge of the binding of PA to FABPs.
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Affiliation(s)
- Ki Hyun Nam
- Department of Life Science, Pohang University of Science and Technology, Pohang, Republic of Korea
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Zhang Z, Yu J, Wang P, Lin L, Liu R, Zeng R, Ma H, Zhao Y. iTRAQ-based proteomic profiling reveals protein alterations after traumatic brain injury and supports thyroxine as a potential treatment. Mol Brain 2021; 14:25. [PMID: 33504361 PMCID: PMC7839205 DOI: 10.1186/s13041-021-00739-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Accepted: 01/16/2021] [Indexed: 12/25/2022] Open
Abstract
Traumatic brain injury (TBI) is a primary cause of disability and death across the world. Previously, RNA analysis was widely used to study the pathophysiological mechanisms underlying TBI; however, the relatively low correlation between the transcriptome and proteome revealed that RNA transcription abundance does not reliably predict protein abundance, which led to the emergence of proteomic research. In this study, an iTRAQ proteomics approach was applied to detect protein alterations after TBI on a large scale. A total of 3937 proteins were identified, and 146 proteins were significantly changed after TBI. Moreover, 23 upregulated proteins were verified by parallel reaction monitoring (PRM), and fold changes in 16 proteins were consistent with iTRAQ outcomes. Transthyretin (Ttr) upregulation has been demonstrated at the transcriptional level, and this study further confirmed this at the protein level. After treatment with thyroxine (T4), which is transported by Ttr, the effects of T4 on neuronal histopathology and behavioral performance were determined in vivo (TBI + T4 group). Brain edema was alleviated, and the integrity of the blood brain barrier (BBB) improved. Escape latency in the Morris water maze (MWM) declined significantly compared with the group without T4 treatment. Modified neurological severity scores (mNSS) of the TBI + T4 group decreased from day 1 to day 7 post-TBI compared with the TBI + saline group. These results indicate that T4 treatment has potential to alleviate pathologic and behavioral abnormalities post-TBI. Protein alterations after T4 treatment were also detected by iTRAQ proteomics. Upregulation of proteins like Lgals3, Gfap and Apoe after TBI were reversed by T4 treatment. GO enrichment showed T4 mainly affected intermediate filament organization, cholesterol transportation and axonal regeneration. In summary, iTRAQ proteomics provides information about the impact of TBI on protein alterations and yields insight into underlying mechanisms and pathways involved in TBI and T4 treatment. Finally, Ttr and other proteins identified by iTRAQ may become potential novel treatment targets post-TBI.
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Affiliation(s)
- Zhongxiang Zhang
- Emergency Center, Zhongnan Hospital of Wuhan University, Wuhan, 430071 China
- Hubei Clinical Research Center for Emergency and Resuscitation, Zhongnan Hospital of Wuhan University, Wuhan, 430071 China
| | - Jiangtao Yu
- Emergency Center, Zhongnan Hospital of Wuhan University, Wuhan, 430071 China
- Hubei Clinical Research Center for Emergency and Resuscitation, Zhongnan Hospital of Wuhan University, Wuhan, 430071 China
| | - Pengcheng Wang
- Emergency Center, Zhongnan Hospital of Wuhan University, Wuhan, 430071 China
- Hubei Clinical Research Center for Emergency and Resuscitation, Zhongnan Hospital of Wuhan University, Wuhan, 430071 China
| | - Lian Lin
- Emergency Center, Zhongnan Hospital of Wuhan University, Wuhan, 430071 China
- Hubei Clinical Research Center for Emergency and Resuscitation, Zhongnan Hospital of Wuhan University, Wuhan, 430071 China
| | - Ruining Liu
- Emergency Center, Zhongnan Hospital of Wuhan University, Wuhan, 430071 China
- Hubei Clinical Research Center for Emergency and Resuscitation, Zhongnan Hospital of Wuhan University, Wuhan, 430071 China
| | - Rong Zeng
- Emergency Center, Zhongnan Hospital of Wuhan University, Wuhan, 430071 China
- Hubei Clinical Research Center for Emergency and Resuscitation, Zhongnan Hospital of Wuhan University, Wuhan, 430071 China
| | - Haoli Ma
- Hubei Clinical Research Center for Emergency and Resuscitation, Zhongnan Hospital of Wuhan University, Wuhan, 430071 China
- Department of Biological Repositories, Zhongnan Hospital of Wuhan University, Wuhan, 430071 China
| | - Yan Zhao
- Emergency Center, Zhongnan Hospital of Wuhan University, Wuhan, 430071 China
- Hubei Clinical Research Center for Emergency and Resuscitation, Zhongnan Hospital of Wuhan University, Wuhan, 430071 China
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Foerster S, Guzman de la Fuente A, Kagawa Y, Bartels T, Owada Y, Franklin RJM. The fatty acid binding protein FABP7 is required for optimal oligodendrocyte differentiation during myelination but not during remyelination. Glia 2020; 68:1410-1420. [PMID: 32017258 PMCID: PMC7317849 DOI: 10.1002/glia.23789] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 01/10/2020] [Accepted: 01/23/2020] [Indexed: 12/12/2022]
Abstract
The major constituents of the myelin sheath are lipids, which are made up of fatty acids (FAs). The hydrophilic environment inside the cells requires FAs to be bound to proteins, preventing their aggregation. Fatty acid binding proteins (FABPs) are one class of proteins known to bind FAs in a cell. Given the crucial role of FAs for myelin sheath formation we investigated the role of FABP7, the major isoform expressed in oligodendrocyte progenitor cells (OPCs), in developmental myelination and remyelination. Here, we show that the knockdown of Fabp7 resulted in a reduction of OPC differentiation in vitro. Consistent with this result, a delay in developmental myelination was observed in Fabp7 knockout animals. This delay was transient with full myelination being established before adulthood. FABP7 was dispensable for remyelination, as the knockout of Fapb7 did not alter remyelination efficiency in a focal demyelination model. In summary, while FABP7 is important in OPC differentiation in vitro, its function is not crucial for myelination and remyelination in vivo.
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Affiliation(s)
- Sarah Foerster
- Wellcome-Medical Research Council Cambridge Stem Cell Institute, Jeffrey Cheah Biomedical Centre, University of Cambridge, Cambridge, UK
| | - Alerie Guzman de la Fuente
- Wellcome-Medical Research Council Cambridge Stem Cell Institute, Jeffrey Cheah Biomedical Centre, University of Cambridge, Cambridge, UK
| | - Yoshiteru Kagawa
- Department of Organ Anatomy, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Theresa Bartels
- Wellcome-Medical Research Council Cambridge Stem Cell Institute, Jeffrey Cheah Biomedical Centre, University of Cambridge, Cambridge, UK
| | - Yuji Owada
- Department of Organ Anatomy, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Robin J M Franklin
- Wellcome-Medical Research Council Cambridge Stem Cell Institute, Jeffrey Cheah Biomedical Centre, University of Cambridge, Cambridge, UK
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Xu H, Diolintzi A, Storch J. Fatty acid-binding proteins: functional understanding and diagnostic implications. Curr Opin Clin Nutr Metab Care 2019; 22:407-412. [PMID: 31503024 PMCID: PMC9940447 DOI: 10.1097/mco.0000000000000600] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
PURPOSE OF REVIEW Fatty acid-binding proteins (FABPs) are a family of small, abundant proteins with highly tissue-specific expression patterns whose different functions remain incompletely understood. The purpose of this review is to summarize recent findings regarding FABP functions and mechanisms of action, including their potential utilization as serum markers of tissue-specific metabolic diseases. RECENT FINDINGS FABPs are important not only in their tissues of origin but also appear to influence the metabolism and function of tissues distal to their sites of expression. This may be secondary to metabolic changes in their primary tissues, and/or a result of FABP secretion from these tissues leading to effects on distal sites. Their levels in the circulation are increasingly explored as potential biomarkers for tissue-specific disease prognosis and progression. SUMMARY The nine fatty acid-binding members of the FABP family have unique tissue-specific functions and important secondary effects on tissues in which they are not expressed. For many of the FABPs, circulating levels may be indicative of disease processes related to their primary tissues, and may influence physiological function in distal tissues.
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Affiliation(s)
- Heli Xu
- Department of Nutritional Sciences, Rutgers University, New Brunswick,
- Rutgers Center for Lipid Research, New Jersey, USA
| | - Anastasia Diolintzi
- Department of Kinesiology and Health, New Jersey, USA
- Rutgers Center for Lipid Research, New Jersey, USA
| | - Judith Storch
- Department of Nutritional Sciences, Rutgers University, New Brunswick,
- Rutgers Center for Lipid Research, New Jersey, USA
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