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Guo X, Schmiege P, Assafa TE, Wang R, Xu Y, Donnelly L, Fine M, Ni X, Jiang J, Millhauser G, Feng L, Li X. Structure and mechanism of human cystine exporter cystinosin. Cell 2022; 185:3739-3752.e18. [PMID: 36113465 PMCID: PMC9530027 DOI: 10.1016/j.cell.2022.08.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 07/18/2022] [Accepted: 08/17/2022] [Indexed: 01/26/2023]
Abstract
Lysosomal amino acid efflux by proton-driven transporters is essential for lysosomal homeostasis, amino acid recycling, mTOR signaling, and maintaining lysosomal pH. To unravel the mechanisms of these transporters, we focus on cystinosin, a prototypical lysosomal amino acid transporter that exports cystine to the cytosol, where its reduction to cysteine supplies this limiting amino acid for diverse fundamental processes and controlling nutrient adaptation. Cystinosin mutations cause cystinosis, a devastating lysosomal storage disease. Here, we present structures of human cystinosin in lumen-open, cytosol-open, and cystine-bound states, which uncover the cystine recognition mechanism and capture the key conformational states of the transport cycle. Our structures, along with functional studies and double electron-electron resonance spectroscopic investigations, reveal the molecular basis for the transporter's conformational transitions and protonation switch, show conformation-dependent Ragulator-Rag complex engagement, and demonstrate an unexpected activation mechanism. These findings provide molecular insights into lysosomal amino acid efflux and a potential therapeutic strategy.
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Affiliation(s)
- Xue Guo
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Philip Schmiege
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Tufa E Assafa
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95060, USA
| | - Rong Wang
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Yan Xu
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Linda Donnelly
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Michael Fine
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Xiaodan Ni
- Laboratory of Membrane Proteins and Structural Biology, Biochemistry and Biophysics Center, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jiansen Jiang
- Laboratory of Membrane Proteins and Structural Biology, Biochemistry and Biophysics Center, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Glenn Millhauser
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95060, USA.
| | - Liang Feng
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA.
| | - Xiaochun Li
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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Zhao M, Liu Q, Zhang Y, Yang N, Wu G, Li Q, Wang W. Alleviation of osmotic stress by H 2S is related to regulated PLDα1 and suppressed ROS in Arabidopsis thaliana. JOURNAL OF PLANT RESEARCH 2020; 133:393-407. [PMID: 32200466 DOI: 10.1007/s10265-020-01182-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Accepted: 03/08/2020] [Indexed: 06/10/2023]
Abstract
Hydrogen sulfide (H2S) is an important gaseous molecule responding to osmotic stress in plant. Phospholipase Dα1 (PLDα1) and reactive oxygen species (ROS) are involved in many biotic or abiotic stress responses. Using the seedlings of Arabidopsis thaliana ecotype (WT), PLDα1 deficient mutant (pldα1) and the L-cysteine desulfhydrase (L-DEs) deficient mutant (lcd) as materials, the effect of H2S responding to osmotic stress and the functions of PLDα1 and ROS in this response were investigated. The results showed that H2S, PLDα1 and ROS were involved in osmotic stress resistance. Exogenous sodium hydrosulfide (NaHS) promoted the endogenous H2S content and up-regulated the expression of LCD in WT, lcd and plda1. Exogenous phosphatidic acid (PA) enhanced the H2S content and up-regulated the expressions of LCD in WT and plda1 but had no significant effect on the H2S content and LCD expression in lcd under osmotic stress. This suggested that H2S was located downstream of PLDα1 to participate in the osmotic stress signal response. Exogenous NaHS treatment regulated the antioxidant enzymes (SOD, POD, and CAT). The activities and the gene relative expressions of antioxidant enzymes in pldα1 and lcd were higher than those in WT under osmotic stress. This indicated that H2S and PLD regulated the antioxidant enzyme system under osmotic stress. The ROS level, electrolyte leakage (EL), malondialdehyde (MDA) were decreased by NaHS under osmotic stress, demonstrating H2S maintained the membrane integrity. All of these results revealed that H2S alleviated the osmotic stress by elevating PLD and suppressing ROS in A. thaliana.
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Affiliation(s)
- Min Zhao
- College of Life Science, Northwest Normal University, Lanzhou, 730070, China
| | - Qin Liu
- College of Life Science, Northwest Normal University, Lanzhou, 730070, China
| | - Yue Zhang
- College of Life Science, Northwest Normal University, Lanzhou, 730070, China
| | - Ning Yang
- College of Life Science, Northwest Normal University, Lanzhou, 730070, China.
- Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, Lanzhou, 730000, China.
| | - Guofan Wu
- College of Life Science, Northwest Normal University, Lanzhou, 730070, China
| | - Qiaoxia Li
- College of Life Science, Northwest Normal University, Lanzhou, 730070, China
| | - Wei Wang
- College of Life Science, Northwest Normal University, Lanzhou, 730070, China
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Insights into multifaceted activities of CysK for therapeutic interventions. 3 Biotech 2019; 9:44. [PMID: 30675454 DOI: 10.1007/s13205-019-1572-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Accepted: 01/10/2019] [Indexed: 01/24/2023] Open
Abstract
CysK (O-acetylserine sulfhydrylase) is a pyridoxal-5' phosphate-dependent enzyme which catalyzes the second step of the de novo cysteine biosynthesis pathway by converting O-acetyl serine (OAS) into l-cysteine in the presence of sulfide. The first step of the cysteine biosynthesis involves formation of OAS from serine and acetyl CoA by CysE (serine acetyltransferase). Apart from role of CysK in cysteine biosynthesis, recent studies have revealed various additional roles of this enzyme in bacterial physiology. Other than the suggested regulatory role in cysteine production, other activities of CysK include involvement of CysK-in contact-dependent toxin activation in Gram-negative pathogens, as a transcriptional regulator of CymR by stabilizing the CymR-DNA interactions, in biofilm formation by providing cysteine and via another mechanism not yet understood, in ofloxacin and tellurite resistance as well as in cysteine desulfurization. Some of these activities involve binding of CysK to another cellular partner, where the complex is regulated by the availability of OAS and/or sulfide (H2S). The aim of this study is to present an overview of current knowledge of multiple functions performed by CysK and identifying structural features involved in alternate functions. Due to possible role in disease, promoting or inhibiting a "moonlighting" function of CysK could be a target for developing novel therapeutic interventions.
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Structural insights into the catalytic mechanism of cysteine (hydroxyl) lyase from the hydrogen sulfide-producing oral pathogen, Fusobacterium nucleatum. Biochem J 2018; 475:733-748. [DOI: 10.1042/bcj20170838] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Revised: 01/10/2018] [Accepted: 01/16/2018] [Indexed: 02/07/2023]
Abstract
Hydrogen sulfide (H2S) plays important roles in the pathogenesis of periodontitis. Oral pathogens typically produce H2S from l-cysteine in addition to pyruvate and . However, fn1055 from Fusobacterium nucleatum subsp. nucleatum ATCC 25586 encodes a pyridoxal 5′-phosphate (PLP)-dependent enzyme that catalyzes the production of H2S and l-serine from l-cysteine and H2O, an unusual cysteine (hydroxyl) lyase reaction (β-replacement reaction). To reveal the reaction mechanism, the crystal structure of substrate-free Fn1055 was determined. Based on this structure, a model of the l-cysteine-PLP Schiff base suggested that the thiol group forms hydrogen bonds with Asp232 and Ser74, and the substrate α-carboxylate interacts with Thr73 and Gln147. Asp232 is a unique residue to Fn1055 and its substitution to asparagine (D232N) resulted in almost complete loss of β-replacement activity. The D232N structure obtained in the presence of l-cysteine contained the α-aminoacrylate-PLP Schiff base in the active site, indicating that Asp232 is essential for the addition of water to the α-aminoacrylate to produce the l-serine-PLP Schiff base. Rapid-scan stopped-flow kinetic analyses showed an accumulation of the α-aminoacrylate intermediate during the reaction cycle, suggesting that water addition mediated by Asp232 is the rate-limiting step. In contrast, mutants containing substitutions of other active-site residues (Ser74, Thr73, and Gln147) exhibited reduced β-replacement activity by more than 100-fold. Finally, based on the structural and biochemical analyses, we propose a mechanism of the cysteine (hydroxyl) lyase reaction by Fn1055. The present study leads to elucidation of the H2S-producing mechanism in F. nucleatum.
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