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Yu Y, Wang S, Wang Z, Gao R, Lee J. Arabidopsis thaliana: a powerful model organism to explore histone modifications and their upstream regulations. Epigenetics 2023; 18:2211362. [PMID: 37196184 DOI: 10.1080/15592294.2023.2211362] [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: 11/24/2022] [Revised: 04/07/2023] [Accepted: 04/28/2023] [Indexed: 05/19/2023] Open
Abstract
Histones are subjected to extensive covalent modifications that affect inter-nucleosomal interactions as well as alter chromatin structure and DNA accessibility. Through switching the corresponding histone modifications, the level of transcription and diverse downstream biological processes can be regulated. Although animal systems are widely used in studying histone modifications, the signalling processes that occur outside the nucleus prior to histone modifications have not been well understood due to the limitations including non viable mutants, partial lethality, and infertility of survivors. Here, we review the benefits of using Arabidopsis thaliana as the model organism to study histone modifications and their upstream regulations. Similarities among histones and key histone modifiers such as the Polycomb group (PcG) and Trithorax group (TrxG) in Drosophila, Human, and Arabidopsis are examined. Furthermore, prolonged cold-induced vernalization system has been well-studied and revealed the relationship between the controllable environment input (duration of vernalization), its chromatin modifications of FLOWERING LOCUS C (FLC), following gene expression, and the corresponding phenotypes. Such evidence suggests that research on Arabidopsis can bring insights into incomplete signalling pathways outside of the histone box, which can be achieved through viable reverse genetic screenings based on the phenotypes instead of direct monitoring of histone modifications among individual mutants. The potential upstream regulators in Arabidopsis can provide cues or directions for animal research based on the similarities between them.
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Affiliation(s)
- Yang Yu
- Division of Natural and Applied Sciences, Duke Kunshan University, Kunshan, Jiangsu, China
| | - Sihan Wang
- Division of Natural and Applied Sciences, Duke Kunshan University, Kunshan, Jiangsu, China
| | - Ziqin Wang
- Division of Natural and Applied Sciences, Duke Kunshan University, Kunshan, Jiangsu, China
| | - Renwei Gao
- Division of Natural and Applied Sciences, Duke Kunshan University, Kunshan, Jiangsu, China
| | - Joohyun Lee
- Division of Natural and Applied Sciences, Duke Kunshan University, Kunshan, Jiangsu, China
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2
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Wang Y, Kinoshita T. The role of lipid scramblases in regulating lipid distributions at cellular membranes. Biochem Soc Trans 2023; 51:1857-1869. [PMID: 37767549 DOI: 10.1042/bst20221455] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 09/12/2023] [Accepted: 09/19/2023] [Indexed: 09/29/2023]
Abstract
Glycerophospholipids, sphingolipids and cholesterol assemble into lipid bilayers that form the scaffold of cellular membranes, in which proteins are embedded. Membrane composition and membrane protein profiles differ between plasma and intracellular membranes and between the two leaflets of a membrane. Lipid distributions between two leaflets are mediated by lipid translocases, including flippases and scramblases. Flippases use ATP to catalyze the inward movement of specific lipids between leaflets. In contrast, bidirectional flip-flop movements of lipids across the membrane are mediated by scramblases in an ATP-independent manner. Scramblases have been implicated in disrupting the lipid asymmetry of the plasma membrane, protein glycosylation, autophagosome biogenesis, lipoprotein secretion, lipid droplet formation and communications between organelles. Although scramblases in plasma membranes were identified over 10 years ago, most progress about scramblases localized in intracellular membranes has been made in the last few years. Herein, we review the role of scramblases in regulating lipid distributions in cellular membranes, focusing primarily on intracellular membrane-localized scramblases.
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Affiliation(s)
- Yicheng Wang
- State Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
- Key Laboratory of Biopharmaceutical Preparation and Delivery, Chinese Academy of Sciences, Beijing 100190, China
| | - Taroh Kinoshita
- Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871, Japan
- WPI Immunology Frontier Research Center, Osaka University, Suita, Osaka 565-0871, Japan
- Center for Infectious Disease Education and Research, Osaka University, Suita, Osaka 565-0871, Japan
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3
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Lim KK, Koh NZH, Zeng YB, Chuan JK, Raechell R, Chen ES. Resistance to Chemotherapeutic 5-Fluorouracil Conferred by Modulation of Heterochromatic Integrity through Ino80 Function in Fission Yeast. Int J Mol Sci 2023; 24:10687. [PMID: 37445861 DOI: 10.3390/ijms241310687] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Revised: 06/23/2023] [Accepted: 06/25/2023] [Indexed: 07/15/2023] Open
Abstract
5-Fluorouracil (5-FU) is a conventional chemotherapeutic drug widely used in clinics worldwide, but development of resistance that compromises responsiveness remains a major hurdle to its efficacy. The mechanism underlying 5-FU resistance is conventionally attributed to the disruption of nucleotide synthesis, even though research has implicated other pathways such as RNA processing and chromatin dysregulation. Aiming to clarify resistance mechanisms of 5-FU, we tested the response of a collection of fission yeast (Schizosaccharomyces pombe) null mutants, which confer multiple environmental factor responsiveness (MER). Our screen identified disruption of membrane transport, chromosome segregation and mitochondrial oxidative phosphorylation to increase cellular susceptibility towards 5-FU. Conversely, we revealed several null mutants of Ino80 complex factors exhibited resistance to 5-FU. Furthermore, attenuation of Ino80 function via deleting several subunit genes reversed loss of chromosome-segregation fidelity in 5-FU in the loss-of-function mutant of the Argonaute protein, which regulates RNA interference (RNAi)-dependent maintenance of pericentromeric heterochromatin. Our study thus uncovered a critical role played by chromatin remodeling Ino80 complex factors in 5-FU resistance, which may constitute a possible target to modulate in reversing 5-FU resistance.
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Affiliation(s)
- Kim Kiat Lim
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117596, Singapore
| | - Nathaniel Zhi Hao Koh
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117596, Singapore
| | - Yi Bing Zeng
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117596, Singapore
| | - Jun Kai Chuan
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117596, Singapore
| | - Raechell Raechell
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117596, Singapore
| | - Ee Sin Chen
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117596, Singapore
- National University Health System (NUHS), Singapore 119228, Singapore
- NUS Center for Cancer Research, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117599, Singapore
- NUS Graduate School-Integrative Sciences & Engineering Programme, National University of Singapore, Singapore 119077, Singapore
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4
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E96V Mutation in the Kdelr3 Gene Is Associated with Type 2 Diabetes Susceptibility in Obese NZO Mice. Int J Mol Sci 2023; 24:ijms24010845. [PMID: 36614300 PMCID: PMC9820861 DOI: 10.3390/ijms24010845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 12/16/2022] [Accepted: 12/28/2022] [Indexed: 01/05/2023] Open
Abstract
Type 2 diabetes (T2D) represents a multifactorial metabolic disease with a strong genetic predisposition. Despite elaborate efforts in identifying the genetic variants determining individual susceptibility towards T2D, the majority of genetic factors driving disease development remain poorly understood. With the aim to identify novel T2D risk genes we previously generated an N2 outcross population using the two inbred mouse strains New Zealand obese (NZO) and C3HeB/FeJ (C3H). A linkage study performed in this population led to the identification of the novel T2D-associated quantitative trait locus (QTL) Nbg15 (NZO blood glucose on chromosome 15, Logarithm of odds (LOD) 6.6). In this study we used a combined approach of positional cloning, gene expression analyses and in silico predictions of DNA polymorphism on gene/protein function to dissect the genetic variants linking Nbg15 to the development of T2D. Moreover, we have generated congenic strains that associated the distal sublocus of Nbg15 to mechanisms altering pancreatic beta cell function. In this sublocus, Cbx6, Fam135b and Kdelr3 were nominated as potential causative genes associated with the Nbg15 driven effects. Moreover, a putative mutation in the Kdelr3 gene from NZO was identified, negatively influencing adaptive responses associated with pancreatic beta cell death and induction of endoplasmic reticulum stress. Importantly, knockdown of Kdelr3 in cultured Min6 beta cells altered insulin granules maturation and pro-insulin levels, pointing towards a crucial role of this gene in islets function and T2D susceptibility.
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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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6
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Structural basis for proton coupled cystine transport by cystinosin. Nat Commun 2022; 13:4845. [PMID: 35977944 PMCID: PMC9385667 DOI: 10.1038/s41467-022-32589-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Accepted: 08/08/2022] [Indexed: 11/09/2022] Open
Abstract
Amino acid transporters play a key role controlling the flow of nutrients across the lysosomal membrane and regulating metabolism in the cell. Mutations in the gene encoding the transporter cystinosin result in cystinosis, an autosomal recessive metabolic disorder characterised by the accumulation of cystine crystals in the lysosome. Cystinosin is a member of the PQ-loop family of solute carrier (SLC) transporters and uses the proton gradient to drive cystine export into the cytoplasm. However, the molecular basis for cystinosin function remains elusive, hampering efforts to develop novel treatments for cystinosis and understand the mechanisms of ion driven transport in the PQ-loop family. To address these questions, we present the crystal structures of cystinosin from Arabidopsis thaliana in both apo and cystine bound states. Using a combination of in vitro and in vivo based assays, we establish a mechanism for cystine recognition and proton coupled transport. Mutational mapping and functional characterisation of human cystinosin further provide a framework for understanding the molecular impact of disease-causing mutations. Mutations in CTNS, the lysosomal cystine-proton symporter, cause cystinosis. Here authors report crystal structures of CTNS from Arabidopsis thaliana in complex with cystine, and establish the mode of ligand recognition and mechanism for proton-coupled cystine export from the lysosome.
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7
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KDEL Receptors: Pathophysiological Functions, Therapeutic Options, and Biotechnological Opportunities. Biomedicines 2022; 10:biomedicines10061234. [PMID: 35740256 PMCID: PMC9220330 DOI: 10.3390/biomedicines10061234] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 05/20/2022] [Accepted: 05/23/2022] [Indexed: 02/07/2023] Open
Abstract
KDEL receptors (KDELRs) are ubiquitous seven-transmembrane domain proteins encoded by three mammalian genes. They bind to and retro-transport endoplasmic reticulum (ER)-resident proteins with a C-terminal Lys-Asp-Glu-Leu (KDEL) sequence or variants thereof. In doing this, KDELR participates in the ER quality control of newly synthesized proteins and the unfolded protein response. The binding of KDEL proteins to KDELR initiates signaling cascades involving three alpha subunits of heterotrimeric G proteins, Src family kinases, protein kinases A (PKAs), and mitogen-activated protein kinases (MAPKs). These signaling pathways coordinate membrane trafficking flows between secretory compartments and control the degradation of the extracellular matrix (ECM), an important step in cancer progression. Considering the basic cellular functions performed by KDELRs, their association with various diseases is not surprising. KDELR mutants unable to bind the collagen-specific chaperon heat-shock protein 47 (HSP47) cause the osteogenesis imperfecta. Moreover, the overexpression of KDELRs appears to be linked to neurodegenerative diseases that share pathological ER-stress and activation of the unfolded protein response (UPR). Even immune function requires a functional KDELR1, as its mutants reduce the number of T lymphocytes and impair antiviral immunity. Several studies have also brought to light the exploitation of the shuttle activity of KDELR during the intoxication and maturation/exit of viral particles. Based on the above, KDELRs can be considered potential targets for the development of novel therapeutic strategies for a variety of diseases involving proteostasis disruption, cancer progression, and infectious disease. However, no drugs targeting KDELR functions are available to date; rather, KDELR has been leveraged to deliver drugs efficiently into cells or improve antigen presentation.
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Genome-wide CRISPR screen reveals CLPTM1L as a lipid scramblase required for efficient glycosylphosphatidylinositol biosynthesis. Proc Natl Acad Sci U S A 2022; 119:e2115083119. [PMID: 35344438 PMCID: PMC9169118 DOI: 10.1073/pnas.2115083119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Scramblases translocate lipids across the lipid bilayer without consumption of ATP, thereby regulating lipid distributions in cellular membranes. Cytosol-to-lumen translocation across the endoplasmic reticulum (ER) membrane is a common process among lipid glycoconjugates involved in posttranslational protein modifications in eukaryotes. These translocations are thought to be mediated by specific ER-resident scramblases, but the identity of these proteins and the underlying molecular mechanisms have been elusive. Here, we show that CLPTM1L, an integral membrane protein with eight putative transmembrane domains, is the major lipid scramblase involved in efficient glycosylphosphatidylinositol biosynthesis in the ER membrane. Our results validate the long-standing hypothesis that lipid scramblases ensure the efficient translocations of lipid glycoconjugates across the ER membrane for protein glycosylation pathways. Glycosylphosphatidylinositols (GPIs) are complex glycolipids that act as membrane anchors of many eukaryotic cell surface proteins. Biosynthesis of GPIs is initiated at the cytosolic face of the endoplasmic reticulum (ER) by generation of N-acetylglucosaminyl-phosphatidylinositol (GlcNAc-PI). The second intermediate, glucosaminyl-phosphatidylinositol (GlcN-PI), is translocated across the membrane to the luminal face for later biosynthetic steps and attachment to proteins. The mechanism of the luminal translocation of GlcN-PI is unclear. Here, we report a genome-wide CRISPR knockout screen of genes required for rescuing GPI-anchored protein expression after addition of chemically synthesized GlcNAc-PI to PIGA-knockout cells that cannot synthesize GlcNAc-PI. We identified CLPTM1L (cleft lip and palate transmembrane protein 1-like), an ER-resident multipass membrane protein, as a GlcN-PI scramblase required for efficient biosynthesis of GPIs. Knockout of CLPTM1L in PIGA-knockout cells impaired the efficient utilization of chemically synthesized GlcNAc-PI and GlcN-PI for GPI biosynthesis. Purified CLPTM1L scrambled GlcN-PI, GlcNAc-PI, PI, and several other phospholipids in vitro. CLPTM1L, a member of the PQ-loop family of proteins, represents a type of lipid scramblase having no structural similarity to known lipid scramblases. Knockout of CLPTM1L in various wild-type mammalian cultured cells partially decreased the level of GPI-anchored proteins. These results suggest that CLPTM1L is the major lipid scramblase involved in cytosol-to-lumen translocation of GlcN-PI across the ER membrane for efficient GPI biosynthesis.
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The Function of KDEL Receptors as UPR Genes in Disease. Int J Mol Sci 2021; 22:ijms22115436. [PMID: 34063979 PMCID: PMC8196686 DOI: 10.3390/ijms22115436] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Revised: 05/17/2021] [Accepted: 05/17/2021] [Indexed: 12/15/2022] Open
Abstract
The KDEL receptor retrieval pathway is essential for maintaining resident proteins in the endoplasmic reticulum (ER) lumen. ER resident proteins serve a variety of functions, including protein folding and maturation. Perturbations to the lumenal ER microenvironment, such as calcium depletion, can cause protein misfolding and activation of the unfolded protein response (UPR). Additionally, ER resident proteins are secreted from the cell by overwhelming the KDEL receptor retrieval pathway. Recent data show that KDEL receptors are also activated during the UPR through the IRE1/XBP1 signaling pathway as an adaptive response to cellular stress set forth to reduce the loss of ER resident proteins. This review will discuss the emerging connection between UPR activation and KDEL receptors as it pertains to ER proteostasis and disease states.
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10
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Arines FM, Hamlin AJ, Yang X, Liu YYJ, Li M. A selective transmembrane recognition mechanism by a membrane-anchored ubiquitin ligase adaptor. J Cell Biol 2021; 220:211632. [PMID: 33351099 PMCID: PMC7759299 DOI: 10.1083/jcb.202001116] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2020] [Revised: 09/10/2020] [Accepted: 10/30/2020] [Indexed: 12/30/2022] Open
Abstract
While it is well-known that E3 ubiquitin ligases can selectively ubiquitinate membrane proteins in response to specific environmental cues, the underlying mechanisms for the selectivity are poorly understood. In particular, the role of transmembrane regions, if any, in target recognition remains an open question. Here, we describe how Ssh4, a yeast E3 ligase adaptor, recognizes the PQ-loop lysine transporter Ypq1 only after lysine starvation. We show evidence of an interaction between two transmembrane helices of Ypq1 (TM5 and TM7) and the single transmembrane helix of Ssh4. This interaction is regulated by the conserved PQ motif. Strikingly, recent structural studies of the PQ-loop family have suggested that TM5 and TM7 undergo major conformational changes during substrate transport, implying that transport-associated conformational changes may determine the selectivity. These findings thus provide critical information concerning the regulatory mechanism through which transmembrane domains can be specifically recognized in response to changing environmental conditions.
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Affiliation(s)
- Felichi Mae Arines
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI
| | - Aaron Jeremy Hamlin
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI
| | - Xi Yang
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI
| | - Yun-Yu Jennifer Liu
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI
| | - Ming Li
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI
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Sun DY, Fu JT, Li GQ, Zhang WJ, Zeng FY, Tong J, Miao CY, Li DJ, Wang P. iTRAQ- and LC-MS/MS-based quantitative proteomics reveals Pqlc2 as a potential regulator of hepatic glucose metabolism and insulin signalling pathway during fasting. Clin Exp Pharmacol Physiol 2021; 48:238-249. [PMID: 33051888 DOI: 10.1111/1440-1681.13419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 09/24/2020] [Accepted: 10/06/2020] [Indexed: 11/30/2022]
Abstract
Glucose homeostasis is tightly controlled by balance between glucose production and uptake in liver tissue upon energy shortage condition. Altered glucose homeostasis contributes to the pathophysiology of metabolic disorders including diabetes and obesity. Here, we aimed to analyse the change of proteomic profile upon prolonged fasting in mice with isobaric tag for relative and absolute quantification (iTRAQ) labelling followed by liquid chromatography-mass spectrometry (LC/MS) technology. Adult male mice were fed or fasted for 16 hours and liver tissues were collected for iTRAQ labelling followed by LC/MS analysis. A total of 322 differentially expressed proteins were identified, including 189 upregulated and 133 downregulated proteins. Bioinformatics analyses, including Gene Ontology analysis (GO), Kyoto encyclopaedia of genes and genomes analysis (KEGG) and protein-protein interaction analysis (PPI) were conducted to understand biological process, cell component, and molecular function of the 322 differentially expressed proteins. Among 322 hepatic proteins differentially expressed between fasting and fed mice, we validated three upregulated proteins (Pqlc2, Ehhadh and Apoa4) and two downregulated proteins (Uba52 and Rpl37) by western-blotting analysis. In cultured HepG2 hepatocellular cells, we found that depletion of Pqlc2 by siRNA-mediated knockdown impaired the insulin-induced glucose uptake, inhibited GLUT2 mRNA level and suppressed the insulin-induced Akt phosphorylation. By contrast, knockdown of Pqlc2 did not affect the cAMP/dexamethasone-induced gluconeogenesis. In conclusion, our study provides important information on protein profile change during prolonged fasting with iTRAQ- and LC-MS/MS-based quantitative proteomics, and identifies Pqlc2 as a potential regulator of hepatic glucose metabolism and insulin signalling pathway in this process.
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Affiliation(s)
- Di-Yang Sun
- Department of Pharmacology, School of Pharmacy, Second Military Medical University/Naval Medical University, Shanghai, China
| | - Jiang-Tao Fu
- Department of Pharmacology, School of Pharmacy, Second Military Medical University/Naval Medical University, Shanghai, China
| | - Guo-Qiang Li
- Department of Pharmacology, School of Pharmacy, Second Military Medical University/Naval Medical University, Shanghai, China
| | - Wen-Jie Zhang
- Department of Pharmacology, School of Pharmacy, Second Military Medical University/Naval Medical University, Shanghai, China
| | - Fei-Yan Zeng
- Department of Pharmacy, Shanghai Tenth People's Hospital, Tongji University, Shanghai, China
| | - Jie Tong
- Department of Pharmacy, Shanghai Tenth People's Hospital, Tongji University, Shanghai, China
| | - Chao-Yu Miao
- Department of Pharmacology, School of Pharmacy, Second Military Medical University/Naval Medical University, Shanghai, China
| | - Dong-Jie Li
- Department of Pharmacy, Shanghai Tenth People's Hospital, Tongji University, Shanghai, China
| | - Pei Wang
- Department of Pharmacology, School of Pharmacy, Second Military Medical University/Naval Medical University, Shanghai, China
- Department of Pharmacy, Shanghai Tenth People's Hospital, Tongji University, Shanghai, China
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12
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Alqahtani M, Lightfoot DJ, Lemtiri‐Chlieh F, Bukhari E, Pardo JM, Julkowska MM, Tester M. The role of PQL genes in response to salinity tolerance in Arabidopsis and barley. PLANT DIRECT 2021; 5:e00301. [PMID: 33615113 PMCID: PMC7876507 DOI: 10.1002/pld3.301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 10/31/2020] [Accepted: 12/13/2020] [Indexed: 06/12/2023]
Abstract
While soil salinity is a global problem, how salt enters plant root cells from the soil solution remains underexplored. Non-selective cation channels (NSCCs) are suggested to be the major pathway for the entry of sodium ions (Na+), yet their genetic constituents remain unknown. Yeast PQ loop (PQL) proteins were previously proposed to encode NSCCs, but the role of PQLs in plants is unknown. The hypothesis tested in this research is that PQL proteins constitute NSCCs mediating some of the Na+ influx into the root, contributing to ion accumulation and the inhibition of growth in saline conditions. We identified plant PQL homologues, and studied the role of one clade of PQL genes in Arabidopsis and barley. Using heterologous expression of AtPQL1a and HvPQL1 in HEK293 cells allowed us to resolve sizable inwardly directed currents permeable to monovalent cations such as Na+, K+, or Li+ upon membrane hyperpolarization. We observed that GFP-tagged PQL proteins localized to intracellular membrane structures, both when transiently over-expressed in tobacco leaf epidermis and in stable Arabidopsis transformants. Expression of AtPQL1a, AtPQL1b, and AtPQL1c was increased by salt stress in the shoot tissue compared to non-stressed plants. Mutant lines with altered expression of AtPQL1a, AtPQL1b, and AtPQL1c developed larger rosettes in saline conditions, while altered levels of AtPQL1a severely reduced development of lateral roots in all conditions. This study provides the first step toward understanding the function of PQL proteins in plants and the role of NSCC in salinity tolerance.
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Affiliation(s)
- Mashael Alqahtani
- Division of Biological and Environmental Sciences and EngineeringKing Abdullah University of Science and TechnologyThuwalKingdom of Saudi Arabia
- Biology DepartmentPrincess Nourah Bint Abdul Rahman UniversityRiyadhKingdom of Saudi Arabia
| | - Damien J. Lightfoot
- Division of Biological and Environmental Sciences and EngineeringKing Abdullah University of Science and TechnologyThuwalKingdom of Saudi Arabia
| | - Fouad Lemtiri‐Chlieh
- Division of Biological and Environmental Sciences and EngineeringKing Abdullah University of Science and TechnologyThuwalKingdom of Saudi Arabia
- Department of NeuroscienceUniversity of Connecticut School of MedicineFarmingtonCTUSA
| | - Ebtihaj Bukhari
- Division of Biological and Environmental Sciences and EngineeringKing Abdullah University of Science and TechnologyThuwalKingdom of Saudi Arabia
| | - José M. Pardo
- Instituto de Bioquimica Vegetal y Fotosintesis (IBVF)Consejo Superior de Investigaciones Científicas (CSIC)University of SevilleSevilleSpain
| | - Magdalena M. Julkowska
- Division of Biological and Environmental Sciences and EngineeringKing Abdullah University of Science and TechnologyThuwalKingdom of Saudi Arabia
| | - Mark Tester
- Division of Biological and Environmental Sciences and EngineeringKing Abdullah University of Science and TechnologyThuwalKingdom of Saudi Arabia
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Thomas S. The Structure of the Membrane Protein of SARS-CoV-2 Resembles the Sugar Transporter SemiSWEET. Pathog Immun 2020; 5:342-363. [PMID: 33154981 PMCID: PMC7608487 DOI: 10.20411/pai.v5i1.377] [Citation(s) in RCA: 90] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Accepted: 06/16/2020] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the disease COVID-19 that has decimated the health and economy of our planet. The virus causes the disease not only in people but also in companion and wild animals. People with diabetes are at risk of the disease. As yet we do not know why the virus has been highly successful in causing the pandemic within 3 months of its first report. The structural proteins of SARS include membrane glycoprotein (M), envelope protein (E), nucleocapsid protein (N), and the spike protein (S). METHODS The structure and function of the most abundant structural protein of SARS-CoV-2, the membrane (M) glycoprotein, is not fully understood. Using in silico analyses we determined the structure and potential function of the M protein. RESULTS The M protein of SARS-CoV-2 is 98.6% similar to the M protein of bat SARS-CoV, maintains 98.2% homology with pangolin SARS-CoV, and has 90% homology with the M protein of SARS-CoV; whereas, the similarity is only 38% with the M protein of MERS-CoV. In silico analyses showed that the M protein of SARS-CoV-2 has a triple helix bundle, forms a single 3-trans-membrane domain, and is homologous to the prokaryotic sugar transport protein SemiSWEET. SemiSWEETs are related to the PQ-loop family whose members function as cargo receptors in vesicle transport, mediate movement of basic amino acids across lysosomal membranes, and are also involved in phospholipase flippase function. CONCLUSIONS The advantage and role of the M protein having a sugar transporter-like structure is not clearly understood. The M protein of SARS-CoV-2 interacts with S, E, and N protein. The S protein of the virus is glycosylated. It could be hypothesized that the sugar transporter-like structure of the M protein influences glycosylation of the S protein. Endocytosis is critical for the internalization and maturation of RNA viruses, including SARS-CoV-2. Sucrose is involved in endosome and lysosome maturation and may also induce autophagy, pathways that help in the entry of the virus. Overall, it could be hypothesized that the SemiSWEET sugar transporter-like structure of the M protein may be involved in multiple functions that may aid in the rapid proliferation, replication, and immune evasion of the SARS-CoV-2 virus. Biological experiments would validate the presence and function of the SemiSWEET sugar transporter.
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Affiliation(s)
- Sunil Thomas
- Lankenau Institute for Medical Research, Wynnewood, PA-19096, USA
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14
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Wu Z, Newstead S, Biggin PC. The KDEL trafficking receptor exploits pH to tune the strength of an unusual short hydrogen bond. Sci Rep 2020; 10:16903. [PMID: 33037300 PMCID: PMC7547670 DOI: 10.1038/s41598-020-73906-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Accepted: 09/23/2020] [Indexed: 12/27/2022] Open
Abstract
The endoplasmic reticulum (ER) is the main site of protein synthesis in eukaryotic cells and requires a high concentration of luminal chaperones to function. During protein synthesis, ER luminal chaperones are swept along the secretory pathway and must be retrieved to maintain cell viability. ER protein retrieval is achieved by the KDEL receptor, which recognises a C-terminal Lys-Asp-Glu-Leu (KDEL) sequence. Recognition of ER proteins by the KDEL receptor is pH dependent, with binding occurring under acidic conditions in the Golgi and release under conditions of higher pH in the ER. Recent crystal structures of the KDEL receptor in the apo and peptide bound state suggested that peptide binding drives the formation of a short-hydrogen bond that locks the KDEL sequence in the receptor and activates the receptor for COPI binding in the cytoplasm. Using quantum mechanical calculations we demonstrate that the strength of this short hydrogen bond is reinforced following protonation of a nearby histidine, providing a conceptual link between receptor protonation and KDEL peptide binding. Protonation also controls the water networks adjacent to the peptide binding site, leading to a conformational change that ultimately allows the receptor-complex to be recognized by the COPI system.
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Affiliation(s)
- Zhiyi Wu
- Department of Biochemistry, South Parks Road, Oxford, OX1 3QU, UK
| | - Simon Newstead
- Department of Biochemistry, South Parks Road, Oxford, OX1 3QU, UK.
| | - Philip C Biggin
- Department of Biochemistry, South Parks Road, Oxford, OX1 3QU, UK.
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15
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Newstead S, Barr F. Molecular basis for KDEL-mediated retrieval of escaped ER-resident proteins - SWEET talking the COPs. J Cell Sci 2020; 133:133/19/jcs250100. [PMID: 33037041 PMCID: PMC7561476 DOI: 10.1242/jcs.250100] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 07/30/2020] [Indexed: 12/11/2022] Open
Abstract
Protein localisation in the cell is controlled through the function of trafficking receptors, which recognise specific signal sequences and direct cargo proteins to different locations. The KDEL receptor (KDELR) was one of the first intracellular trafficking receptors identified and plays an essential role in maintaining the integrity of the early secretory pathway. The receptor recognises variants of a canonical C-terminal Lys-Asp-Glu-Leu (KDEL) signal sequence on ER-resident proteins when these escape to the Golgi, and targets these proteins to COPI- coated vesicles for retrograde transport back to the ER. The empty receptor is then recycled from the ER back to the Golgi by COPII-coated vesicles. Crystal structures of the KDELR show that it is structurally related to the PQ-loop family of transporters that are found in both pro- and eukaryotes, and shuttle sugars, amino acids and vitamins across cellular membranes. Furthermore, analogous to PQ-loop transporters, the KDELR undergoes a pH-dependent and ligand-regulated conformational cycle. Here, we propose that the striking structural similarity between the KDELR and PQ-loop transporters reveals a connection between transport and trafficking in the cell, with important implications for understanding trafficking receptor evolution and function. Summary: The structure of the KDEL receptor gives new insights into the close connection between trafficking and transport in the cell.
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Affiliation(s)
- Simon Newstead
- Department of Biochemistry, University of Oxford, South Parks Rd, Oxford OX1 3QU, UK
| | - Francis Barr
- Department of Biochemistry, University of Oxford, South Parks Rd, Oxford OX1 3QU, UK
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16
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Thoene JG, DelMonte MA, Mullet J. Microvesicle delivery of a lysosomal transport protein to ex vivo rabbit cornea. Mol Genet Metab Rep 2020; 23:100587. [PMID: 32280591 PMCID: PMC7138922 DOI: 10.1016/j.ymgmr.2020.100587] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 03/31/2020] [Accepted: 04/02/2020] [Indexed: 11/17/2022] Open
Abstract
Therapeutic use of transmembrane proteins is limited because of irreversible denaturation when away from their native lipid membrane. Mutations in lysosomal membrane transport proteins cause many lethal disorders including cystinosis which results from mutations in CTNS, which codes for the lysosomal cystine transport protein, cystinosin. Cystinosin-deficient fibroblasts, including keratocytes (corneal fibroblasts) accumulate lysosomal cystine. Cystinosis patients develop highly painful corneal cystine crystals, resulting in severe visually debilitating photophobia. The only available therapy is daily treatment with cysteamine eye drops. We have previously shown that microvesicles containing functional cystinosin are spontaneously produced by infecting Spodoptera frugiperda cells (Sf9) with baculovirus containing human wt CTNS. Infecting Sf9 cells for 3 days at a MOI of 1 yields 1011microvesicles /ml with a modal diameter of 90 nm. Addition of these vesicles to cultures of cystinotic fibroblasts produces cystine depletion over the course of 96 h, which persists for 2 weeks. In this paper we show that addition of such microvesicles containing cystinosinGFP to ex vivo rabbit ocular globes yields punctate perinuclear green fluorescence in the corneal keratocytes. These results support potential therapeutic use of these cystinosin containing microvesicles in treating cystinotic corneal keratopathy with the advantage of administering twice/month instead of daily topical administration.
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Affiliation(s)
- Jess G Thoene
- Department of Pediatrics, Division of Pediatric Genetics, Metabolism and Genomic Medicine, University of Michigan, Ann Arbor, MI 48109, USA
| | - Monte A DelMonte
- Department of Ophthalmology and Visual Sciences, Division of Pediatric Ophthalmology, Kellogg Eye Center, University of Michigan, Ann Arbor, MI 48105, USA
| | - Jodi Mullet
- Department of Pediatrics, Division of Pediatric Genetics, Metabolism and Genomic Medicine, University of Michigan, Ann Arbor, MI 48109, USA
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17
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Brasell EJ, Chu LL, Akpa MM, Eshkar-Oren I, Alroy I, Corsini R, Gilfix BM, Yamanaka Y, Huertas P, Goodyer P. The novel aminoglycoside, ELX-02, permits CTNSW138X translational read-through and restores lysosomal cystine efflux in cystinosis. PLoS One 2019; 14:e0223954. [PMID: 31800572 PMCID: PMC6892560 DOI: 10.1371/journal.pone.0223954] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Accepted: 10/02/2019] [Indexed: 12/19/2022] Open
Abstract
Background Cystinosis is a rare disorder caused by recessive mutations of the CTNS gene. Current therapy decreases cystine accumulation, thus slowing organ deterioration without reversing renal Fanconi syndrome or preventing eventual need for a kidney transplant.15-20% of cystinosis patients harbour at least one nonsense mutation in CTNS, leading to premature end of translation of the transcript. Aminoglycosides have been shown to permit translational read-through but have high toxicity level, especially in the kidney and inner ear. ELX-02, a modified aminoglycoside, retains it read-through ability without the toxicity. Methods and findings We ascertained the toxicity of ELX-02 in cells and in mice as well as the effect of ELX-02 on translational read-through of nonsense mutations in cystinotic mice and human cells. ELX-02 was not toxic in vitro or in vivo, and permitted read-through of nonsense mutations in cystinotic mice and human cells. Conclusions ELX-02 has translational read-through activity and produces a functional CTNS protein, as evidenced by reduced cystine accumulation. This reduction is comparable to cysteamine treatment. ELX-02 accumulates in the kidney but neither cytotoxicity nor nephrotoxicity was observed.
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Affiliation(s)
- Emma J. Brasell
- McGill University, Department of Human Genetics, Montreal, Canada
| | - Lee Lee Chu
- Research Institute of the McGill University Health Centre, Montreal, Canada
| | - Murielle M. Akpa
- Research Institute of the McGill University Health Centre, Montreal, Canada
| | - Idit Eshkar-Oren
- McGill University, Department of Experimental Medicine, Montreal, Canada
| | - Iris Alroy
- McGill University, Department of Experimental Medicine, Montreal, Canada
| | - Rachel Corsini
- Research Institute of the McGill University Health Centre, Montreal, Canada
| | - Brian M. Gilfix
- Research Institute of the McGill University Health Centre, Montreal, Canada
| | - Yojiro Yamanaka
- McGill University, Department of Human Genetics, Montreal, Canada
| | - Pedro Huertas
- McGill University, Department of Experimental Medicine, Montreal, Canada
| | - Paul Goodyer
- McGill University, Department of Human Genetics, Montreal, Canada
- Research Institute of the McGill University Health Centre, Montreal, Canada
- Montreal Children’s Hospital, Department of Nephrology, Montreal, Canada
- Eloxx Pharmaceuticals, Inc., Waltham, United States of America
- * E-mail:
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18
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Takar M, Huang Y, Graham TR. The PQ-loop protein Any1 segregates Drs2 and Neo1 functions required for viability and plasma membrane phospholipid asymmetry. J Lipid Res 2019; 60:1032-1042. [PMID: 30824614 PMCID: PMC6495175 DOI: 10.1194/jlr.m093526] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Indexed: 02/06/2023] Open
Abstract
Membrane asymmetry is a key organizational feature of the plasma membrane. Type IV P-type ATPases (P4-ATPases) are phospholipid flippases that establish membrane asymmetry by translocating phospholipids, such as phosphatidylserine (PS) and phospatidylethanolamine, from the exofacial leaflet to the cytosolic leaflet. Saccharomyces cerevisiae expresses five P4-ATPases: Drs2, Neo1, Dnf1, Dnf2, and Dnf3. The inactivation of Neo1 is lethal, suggesting Neo1 mediates an essential function not exerted by the other P4-ATPases. However, the disruption of ANY1, which encodes a PQ-loop membrane protein, allows the growth of neo1Δ and reveals functional redundancy between Golgi-localized Neo1 and Drs2. Here we show Drs2 PS flippase activity is required to support neo1Δ any1Δ viability. Additionally, a Dnf1 variant with enhanced PS flipping ability can replace Drs2 and Neo1 function in any1Δ cells. any1Δ also suppresses drs2Δ growth defects but not the loss of membrane asymmetry. Any1 overexpression perturbs the growth of cells but does not disrupt membrane asymmetry. Any1 coimmunoprecipitates with Neo1, an association prevented by the Any1-inactivating mutation D84G. These results indicate a critical role for PS flippase activity in Golgi membranes to sustain viability and suggests Any1 regulates Golgi membrane remodeling through protein-protein interactions rather than a previously proposed scramblase activity.
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Affiliation(s)
- Mehmet Takar
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235
| | - Yannan Huang
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235
| | - Todd R Graham
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235.
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19
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Kandasamy P, Gyimesi G, Kanai Y, Hediger MA. Amino acid transporters revisited: New views in health and disease. Trends Biochem Sci 2018; 43:752-789. [PMID: 30177408 DOI: 10.1016/j.tibs.2018.05.003] [Citation(s) in RCA: 252] [Impact Index Per Article: 42.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Revised: 05/23/2018] [Accepted: 05/25/2018] [Indexed: 02/09/2023]
Abstract
Amino acid transporters (AATs) are membrane-bound transport proteins that mediate transfer of amino acids into and out of cells or cellular organelles. AATs have diverse functional roles ranging from neurotransmission to acid-base balance, intracellular energy metabolism, and anabolic and catabolic reactions. In cancer cells and diabetes, dysregulation of AATs leads to metabolic reprogramming, which changes intracellular amino acid levels, contributing to the pathogenesis of cancer, obesity and diabetes. Indeed, the neutral amino acid transporters (NATs) SLC7A5/LAT1 and SLC1A5/ASCT2 are likely involved in several human malignancies. However, a clinical therapy that directly targets AATs has not yet been developed. The purpose of this review is to highlight the structural and functional diversity of AATs, their diverse physiological roles in different tissues and organs, their wide-ranging implications in human diseases and the emerging strategies and tools that will be necessary to target AATs therapeutically.
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Affiliation(s)
- Palanivel Kandasamy
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, CH-3012 Bern, Switzerland
| | - Gergely Gyimesi
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, CH-3012 Bern, Switzerland
| | - Yoshikatsu Kanai
- Division of Bio-system Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan.
| | - Matthias A Hediger
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, CH-3012 Bern, Switzerland.
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20
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Saudek V. Potential dual function of PQ-loop proteins such as cystinosin. J Biol Chem 2017; 292:15133. [PMID: 28887435 DOI: 10.1074/jbc.l117.795278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- Vladimir Saudek
- From the Wellcome Trust-MRC Institute of Metabolic Science, University of Cambridge Metabolic Research Laboratories, CB2 OQQ Cambridge, United Kingdom
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21
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Cfs1p, a Novel Membrane Protein in the PQ-Loop Family, Is Involved in Phospholipid Flippase Functions in Yeast. G3-GENES GENOMES GENETICS 2017; 7:179-192. [PMID: 28057802 PMCID: PMC5217107 DOI: 10.1534/g3.116.035238] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Type 4 P-type ATPases (P4-ATPases) function as phospholipid flippases, which translocate phospholipids from the exoplasmic leaflet to the cytoplasmic leaflet of the lipid bilayer, to generate and maintain asymmetric distribution of phospholipids at the plasma membrane and endosomal/Golgi membranes. The budding yeast Saccharomyces cerevisiae has four heteromeric flippases (Drs2p, Dnf1p, Dnf2p, and Dnf3p), associated with the Cdc50p family noncatalytic subunit, and one monomeric flippase, Neo1p. They have been suggested to function in vesicle formation in membrane trafficking pathways, but details of their mechanisms remain to be clarified. Here, to search for novel factors that functionally interact with flippases, we screened transposon insertional mutants for strains that suppressed the cold-sensitive growth defect in the cdc50Δ mutant. We identified a mutation of YMR010W encoding a novel conserved membrane protein that belongs to the PQ-loop family including the cystine transporter cystinosin and the SWEET sugar transporters. We named this gene CFS1 (cdc fifty suppressor 1). GFP-tagged Cfs1p was partially colocalized with Drs2p and Neo1p to endosomal/late Golgi membranes. Interestingly, the cfs1Δ mutation suppressed growth defects in all flippase mutants. Accordingly, defects in membrane trafficking in the flippase mutants were also suppressed. These results suggest that Cfs1p and flippases function antagonistically in membrane trafficking pathways. A growth assay to assess sensitivity to duramycin, a phosphatidylethanolamine (PE)-binding peptide, suggested that the cfs1Δ mutation changed PE asymmetry in the plasma membrane. Cfs1p may thus be a novel regulator of phospholipid asymmetry.
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22
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Cherqui S, Courtoy PJ. The renal Fanconi syndrome in cystinosis: pathogenic insights and therapeutic perspectives. Nat Rev Nephrol 2016; 13:115-131. [PMID: 27990015 DOI: 10.1038/nrneph.2016.182] [Citation(s) in RCA: 94] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Cystinosis is an autosomal recessive metabolic disease that belongs to the family of lysosomal storage disorders. It is caused by a defect in the lysosomal cystine transporter, cystinosin, which results in an accumulation of cystine in all organs. Despite the ubiquitous expression of cystinosin, a renal Fanconi syndrome is often the first manifestation of cystinosis, usually presenting within the first year of life and characterized by the early and severe dysfunction of proximal tubule cells, highlighting the unique vulnerability of this cell type. The current therapy for cystinosis, cysteamine, facilitates lysosomal cystine clearance and greatly delays progression to kidney failure but is unable to correct the Fanconi syndrome. This Review summarizes decades of studies that have fostered a better understanding of the pathogenesis of the renal Fanconi syndrome associated with cystinosis. These studies have unraveled some of the early molecular changes that occur before the onset of tubular atrophy and identified a role for cystinosin beyond cystine transport, in endolysosomal trafficking and proteolysis, lysosomal clearance, autophagy and the regulation of energy balance. These studies have also led to the identification of new potential therapeutic targets and here, we outline the potential role of stem cell therapy for cystinosis and provide insights into the mechanism of haematopoietic stem cell-mediated kidney protection.
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Affiliation(s)
- Stephanie Cherqui
- Department of Pediatrics, Division of Genetics, University of California San Diego, 9500 Gilman Drive, MC 0734, La Jolla, California 92093-0734, USA
| | - Pierre J Courtoy
- Cell biology, de Duve Institute and Université catholique de Louvain, UCL-Brussels, 75 Avenue Hippocrate, B-1200 Brussels, Belgium
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23
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Ruggiero C, Fragassi G, Grossi M, Picciani B, Di Martino R, Capitani M, Buccione R, Luini A, Sallese M. A Golgi-based KDELR-dependent signalling pathway controls extracellular matrix degradation. Oncotarget 2016; 6:3375-93. [PMID: 25682866 PMCID: PMC4413660 DOI: 10.18632/oncotarget.3270] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Accepted: 12/12/2014] [Indexed: 12/24/2022] Open
Abstract
We recently identified an endomembrane-based signalling cascade that is activated by the KDEL receptor (KDELR) on the Golgi complex. At the Golgi, the KDELR acts as a traffic sensor (presumably via binding to chaperones that leave the ER) and triggers signalling pathways that balance membrane fluxes between ER and Golgi. One such pathway relies on Gq and Src. Here, we examine if KDELR might control other cellular modules through this pathway. Given the central role of Src in extracellular matrix (ECM) degradation, we investigated the impact of the KDELR-Src pathway on the ability of cancer cells to degrade the ECM. We find that activation of the KDELR controls ECM degradation by increasing the number of the degradative structures known as invadopodia. The KDELR induces Src activation at the invadopodia and leads to phosphorylation of the Src substrates cortactin and ASAP1, which are required for basal and KDELR-stimulated ECM degradation. This study furthers our understanding of the regulatory circuitry underlying invadopodia-dependent ECM degradation, a key phase in metastases formation and invasive growth.
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Affiliation(s)
- Carmen Ruggiero
- Unit of Genomic Approaches to Membrane Traffic, Fondazione Mario Negri Sud, Santa Maria Imbaro, Chieti, Italy.,Current address: Institut de Pharmacologie Moléculaire et Cellulaire CNRS and Associated International Laboratory (LIA) NEOGENEX CNRS and University of Nice-Sophia-Antipolis, Valbonne, France
| | - Giorgia Fragassi
- Unit of Genomic Approaches to Membrane Traffic, Fondazione Mario Negri Sud, Santa Maria Imbaro, Chieti, Italy
| | - Mauro Grossi
- Unit of Genomic Approaches to Membrane Traffic, Fondazione Mario Negri Sud, Santa Maria Imbaro, Chieti, Italy
| | - Benedetta Picciani
- Unit of Genomic Approaches to Membrane Traffic, Fondazione Mario Negri Sud, Santa Maria Imbaro, Chieti, Italy
| | - Rosaria Di Martino
- Institute of Protein Biochemistry National Research Council, Naples, Italy
| | - Mirco Capitani
- Unit of Genomic Approaches to Membrane Traffic, Fondazione Mario Negri Sud, Santa Maria Imbaro, Chieti, Italy
| | - Roberto Buccione
- Laboratory of Tumour Cell Invasion, Fondazione Mario Negri Sud, Santa Maria Imbaro, Chieti, Italy
| | - Alberto Luini
- Institute of Protein Biochemistry National Research Council, Naples, Italy
| | - Michele Sallese
- Unit of Genomic Approaches to Membrane Traffic, Fondazione Mario Negri Sud, Santa Maria Imbaro, Chieti, Italy
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Luini A, Parashuraman S. Signaling at the Golgi: sensing and controlling the membrane fluxes. Curr Opin Cell Biol 2016; 39:37-42. [PMID: 26908115 DOI: 10.1016/j.ceb.2016.01.014] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Revised: 01/28/2016] [Accepted: 01/30/2016] [Indexed: 11/16/2022]
Abstract
Over the past few decades, it has emerged that the Golgi (and other secretory stations) is host to a variety of signaling molecules and can act as a signaling hub that receives, emits and elaborates signals. This endomembrane-based signaling apparatus appears to have more than one purpose. Its most fundamental function appears to be the auto-regulation of the biosynthetic apparatus to maintain and/or optimize its own activities and to coordinate such activities with those of other cellular modules.(1) This is achieved by dedicated control devices that provide stability, robustness, precision, sensitivity and complexity to cellular behaviors.
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Affiliation(s)
- Alberto Luini
- Institute of Protein Biochemistry, National Research Council, Via P. Castellino 111, 80131 Naples, Italy; Istituto di Ricovero e Cura a Carattere Scientifico SDN, Via Emanuele Gianturco, 113, 80143 Naples, Italy.
| | - Seetharaman Parashuraman
- Institute of Protein Biochemistry, National Research Council, Via P. Castellino 111, 80131 Naples, Italy
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25
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Gray LR, Rauckhorst AJ, Taylor EB. A Method for Multiplexed Measurement of Mitochondrial Pyruvate Carrier Activity. J Biol Chem 2016; 291:7409-17. [PMID: 26823462 DOI: 10.1074/jbc.m115.711663] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Indexed: 11/06/2022] Open
Abstract
The discovery that theMPC1andMPC2genes encode the protein components of the mitochondrial pyruvate carrier (MPC) has invigorated studies of mitochondrial pyruvate transport and its regulation in normal and disease states. Indeed, recent reports have demonstrated MPC involvement in the control of cell fate in cancer and gluconeogenesis in models of type 2 diabetes. Biochemical measurements of MPC activity are foundational for understanding the role of pyruvate transport in health and disease. We developed a 96-well scaled method of [(14)C]pyruvate uptake that markedly decreases sample requirements and increases throughput relative to previous techniques. This method was applied to determine the mouse liver MPCKm(28.0 ± 3.9 μm) andVmax(1.08 ± 0.05 nmol/min/mg), which have not previously been reported.KmandVmaxof the rat liver MPC were found to be 71.2 ± 17 μmand 1.42 ± 0.14 nmol/min/mg, respectively. Additionally, we performed parallel pyruvate uptake and oxidation experiments with the same biological samples and show differential results in response to fasting, demonstrating the continued importance of a direct MPC activity assay. We expect this method will be of value for understanding the contribution of the MPC activity to health and disease states where pyruvate metabolism is expected to play a prominent role.
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Affiliation(s)
- Lawrence R Gray
- From the Department of Biochemistry, the Fraternal Order of the Eagles Diabetes Research Center, the Abboud Cardiovascular Research Center, and the Pappajohn Biomedical Institute, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242
| | - Adam J Rauckhorst
- From the Department of Biochemistry, the Fraternal Order of the Eagles Diabetes Research Center, the Abboud Cardiovascular Research Center, and the Pappajohn Biomedical Institute, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242
| | - Eric B Taylor
- From the Department of Biochemistry, the Fraternal Order of the Eagles Diabetes Research Center, the Abboud Cardiovascular Research Center, and the Pappajohn Biomedical Institute, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242
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Prohibitin: A Novel Molecular Player in KDEL Receptor Signalling. BIOMED RESEARCH INTERNATIONAL 2015; 2015:319454. [PMID: 26064897 PMCID: PMC4442004 DOI: 10.1155/2015/319454] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Accepted: 04/14/2015] [Indexed: 01/25/2023]
Abstract
The KDEL receptor (KDELR) is a seven-transmembrane-domain protein involved in retrograde transport of protein chaperones from the Golgi complex to the endoplasmic reticulum. Our recent findings have shown that the Golgi-localised KDELR acts as a functional G-protein-coupled receptor by binding to and activating Gs and Gq. These G proteins induce activation of PKA and Src and regulate retrograde and anterograde Golgi trafficking. Here we used an integrated coimmunoprecipitation and mass spectrometry approach to identify prohibitin-1 (PHB) as a KDELR interactor. PHB is a multifunctional protein that is involved in signal transduction, cell-cycle control, and stabilisation of mitochondrial proteins. We provide evidence that depletion of PHB induces intense membrane-trafficking activity at the ER–Golgi interface, as revealed by formation of GM130-positive Golgi tubules, and recruitment of p115, β-COP, and GBF1 to the Golgi complex. There is also massive recruitment of SEC31 to endoplasmic-reticulum exit sites. Furthermore, absence of PHB decreases the levels of the Golgi-localised KDELR, thus preventing KDELR-dependent activation of Golgi-Src and inhibiting Golgi-to-plasma-membrane transport of VSVG. We propose a model whereby in analogy to previous findings (e.g., the RAS-RAF signalling pathway), PHB can act as a signalling scaffold protein to assist in KDELR-dependent Src activation.
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Lee Y, Nishizawa T, Yamashita K, Ishitani R, Nureki O. Structural basis for the facilitative diffusion mechanism by SemiSWEET transporter. Nat Commun 2015; 6:6112. [PMID: 25598322 PMCID: PMC4309421 DOI: 10.1038/ncomms7112] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 12/15/2014] [Indexed: 02/07/2023] Open
Abstract
SWEET family proteins mediate sugar transport across biological membranes and play crucial roles in plants and animals. The SWEETs and their bacterial homologues, the SemiSWEETs, are related to the PQ-loop family, which is characterized by highly conserved proline and glutamine residues (PQ-loop motif). Although the structures of the bacterial SemiSWEETs were recently reported, the conformational transition and the significance of the conserved motif in the transport cycle have remained elusive. Here we report crystal structures of SemiSWEET from Escherichia coli, in the both inward-open and outward-open states. A structural comparison revealed that SemiSWEET undergoes an intramolecular conformational change in each protomer. The conserved PQ-loop motif serves as a molecular hinge that enables the 'binder clip-like' motion of SemiSWEET. The present work provides the framework for understanding the overall transport cycles of SWEET and PQ-loop family proteins.
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Affiliation(s)
- Yongchan Lee
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Tomohiro Nishizawa
- 1] Department of Biological Sciences, Graduate School of Science, University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan [2] Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
| | | | - Ryuichiro Ishitani
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Osamu Nureki
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
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Cancino J, Capalbo A, Di Campli A, Giannotta M, Rizzo R, Jung JE, Di Martino R, Persico M, Heinklein P, Sallese M, Luini A. Control systems of membrane transport at the interface between the endoplasmic reticulum and the Golgi. Dev Cell 2014; 30:280-94. [PMID: 25117681 DOI: 10.1016/j.devcel.2014.06.018] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Revised: 04/08/2014] [Accepted: 06/23/2014] [Indexed: 10/24/2022]
Abstract
A fundamental property of cellular processes is to maintain homeostasis despite varying internal and external conditions. Within the membrane transport apparatus, variations in membrane fluxes from the endoplasmic reticulum (ER) to the Golgi complex are balanced by opposite fluxes from the Golgi to the ER to maintain homeostasis between the two organelles. Here we describe a molecular device that balances transport fluxes by integrating transduction cascades with the transport machinery. Specifically, ER-to-Golgi transport activates the KDEL receptor at the Golgi, which triggers a cascade that involves Gs and adenylyl cyclase and phosphodiesterase isoforms and then PKA activation and results in the phosphorylation of transport machinery proteins. This induces retrograde traffic to the ER and balances transport fluxes between the ER and Golgi. Moreover, the KDEL receptor activates CREB1 and other transcription factors that upregulate transport-related genes. Thus, a Golgi-based control system maintains transport homeostasis through both signaling and transcriptional networks.
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Affiliation(s)
- Jorge Cancino
- Istituto di Biochimica delle Proteine, Consiglio Nazionale delle Ricerche, Via Pietro Castellino 111, 80131 Napoli, Italy; Telethon Institute of Genetics and Medicine, Via Pietro Castellino 111, 80131 Napoli, Italy; Departamento de Ciencias Biológicas, Facultad de Ciencias Biológicas, Universidad Andrés Bello, Quillota 980, Viña del Mar 2520000, Chile.
| | - Anita Capalbo
- Istituto di Biochimica delle Proteine, Consiglio Nazionale delle Ricerche, Via Pietro Castellino 111, 80131 Napoli, Italy; Telethon Institute of Genetics and Medicine, Via Pietro Castellino 111, 80131 Napoli, Italy
| | - Antonella Di Campli
- Istituto di Biochimica delle Proteine, Consiglio Nazionale delle Ricerche, Via Pietro Castellino 111, 80131 Napoli, Italy
| | - Monica Giannotta
- Consorzio Mario Negri Sud, Via Nazionale 8/A, 66030 Santa Maria Imbaro (Chieti), Italy
| | - Riccardo Rizzo
- Istituto di Biochimica delle Proteine, Consiglio Nazionale delle Ricerche, Via Pietro Castellino 111, 80131 Napoli, Italy; Telethon Institute of Genetics and Medicine, Via Pietro Castellino 111, 80131 Napoli, Italy
| | - Juan E Jung
- Istituto di Biochimica delle Proteine, Consiglio Nazionale delle Ricerche, Via Pietro Castellino 111, 80131 Napoli, Italy; Istituto di Ricovero e Cura a Carattere Scientifico, Istituto di Ricerca Diagnostica e Nucleare (SDN), 80143 Napoli, Italy
| | - Rosaria Di Martino
- Istituto di Biochimica delle Proteine, Consiglio Nazionale delle Ricerche, Via Pietro Castellino 111, 80131 Napoli, Italy
| | - Maria Persico
- Istituto di Biochimica delle Proteine, Consiglio Nazionale delle Ricerche, Via Pietro Castellino 111, 80131 Napoli, Italy; Istituto di Ricovero e Cura a Carattere Scientifico, Istituto di Ricerca Diagnostica e Nucleare (SDN), 80143 Napoli, Italy
| | - Petra Heinklein
- Institut für Biochemie Charité, Universitätsmedizin Berlin, CrossOver Charitéplatz 1/Sitz, Virchowweg 6, 10117 Berlin, Germany
| | - Michele Sallese
- Consorzio Mario Negri Sud, Via Nazionale 8/A, 66030 Santa Maria Imbaro (Chieti), Italy
| | - Alberto Luini
- Istituto di Biochimica delle Proteine, Consiglio Nazionale delle Ricerche, Via Pietro Castellino 111, 80131 Napoli, Italy; Telethon Institute of Genetics and Medicine, Via Pietro Castellino 111, 80131 Napoli, Italy.
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29
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Luini A, Mavelli G, Jung J, Cancino J. Control systems and coordination protocols of the secretory pathway. F1000PRIME REPORTS 2014; 6:88. [PMID: 25374666 PMCID: PMC4191269 DOI: 10.12703/p6-88] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Like other cellular modules, the secretory pathway and the Golgi complex are likely to be supervised by control systems that support homeostasis and optimal functionality under all conditions, including external and internal perturbations. Moreover, the secretory apparatus must be functionally connected with other cellular modules, such as energy metabolism and protein degradation, via specific rules of interaction, or “coordination protocols”. These regulatory devices are of fundamental importance for optimal function; however, they are generally “hidden” at steady state. The molecular components and the architecture of the control systems and coordination protocols of the secretory pathway are beginning to emerge through studies based on the use of controlled transport-specific perturbations aimed specifically at the detection and analysis of these internal regulatory devices.
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Affiliation(s)
- Alberto Luini
- Consiglio Nazionale delle Ricerche (CNR), Istituto di Biochimica delle Proteine (IBP)Via Pietro Castellino 111, 80131 NapoliItaly
- Telethon Institute of Genetics and Medicine (TIGEM)Via Pietro Castellino 111, 80131 NapoliItaly
| | - Gabriella Mavelli
- Istituto di Analisi dei Sistemi ed Informatica Antonio Ruberti, Consiglio Nazionale delle RicercheViale Manzoni 30, 00185 RomaItaly
| | - Juan Jung
- Istituto di Ricovero e Cura a Carattere Scientifico-SDN80143 NapoliItaly
| | - Jorge Cancino
- Consiglio Nazionale delle Ricerche (CNR), Istituto di Biochimica delle Proteine (IBP)Via Pietro Castellino 111, 80131 NapoliItaly
- Departamento de Ciencias Biológicas, Facultad de Ciencias Biológicas, Universidad Andrés BelloQuillota 980, 2520000 Viña del MarChile
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30
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Proteomics and pathway analysis of N-glycosylated mammary gland proteins in response to Escherichia coli mastitis in cattle. Vet J 2014; 200:420-5. [DOI: 10.1016/j.tvjl.2014.03.026] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2013] [Revised: 03/06/2014] [Accepted: 03/25/2014] [Indexed: 12/28/2022]
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Koumandou VL, Wickstead B, Ginger ML, van der Giezen M, Dacks JB, Field MC. Molecular paleontology and complexity in the last eukaryotic common ancestor. Crit Rev Biochem Mol Biol 2014; 48:373-96. [PMID: 23895660 PMCID: PMC3791482 DOI: 10.3109/10409238.2013.821444] [Citation(s) in RCA: 133] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Eukaryogenesis, the origin of the eukaryotic cell, represents one of the fundamental evolutionary transitions in the history of life on earth. This event, which is estimated to have occurred over one billion years ago, remains rather poorly understood. While some well-validated examples of fossil microbial eukaryotes for this time frame have been described, these can provide only basic morphology and the molecular machinery present in these organisms has remained unknown. Complete and partial genomic information has begun to fill this gap, and is being used to trace proteins and cellular traits to their roots and to provide unprecedented levels of resolution of structures, metabolic pathways and capabilities of organisms at these earliest points within the eukaryotic lineage. This is essentially allowing a molecular paleontology. What has emerged from these studies is spectacular cellular complexity prior to expansion of the eukaryotic lineages. Multiple reconstructed cellular systems indicate a very sophisticated biology, which by implication arose following the initial eukaryogenesis event but prior to eukaryotic radiation and provides a challenge in terms of explaining how these early eukaryotes arose and in understanding how they lived. Here, we provide brief overviews of several cellular systems and the major emerging conclusions, together with predictions for subsequent directions in evolution leading to extant taxa. We also consider what these reconstructions suggest about the life styles and capabilities of these earliest eukaryotes and the period of evolution between the radiation of eukaryotes and the eukaryogenesis event itself.
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Affiliation(s)
- V Lila Koumandou
- Biomedical Research Foundation, Academy of Athens, Soranou Efesiou 4, Athens 115 27, Greece
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Gray LR, Tompkins SC, Taylor EB. Regulation of pyruvate metabolism and human disease. Cell Mol Life Sci 2013; 71:2577-604. [PMID: 24363178 PMCID: PMC4059968 DOI: 10.1007/s00018-013-1539-2] [Citation(s) in RCA: 514] [Impact Index Per Article: 46.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Revised: 11/24/2013] [Accepted: 12/02/2013] [Indexed: 12/31/2022]
Abstract
Pyruvate is a keystone molecule critical for numerous aspects of eukaryotic and human metabolism. Pyruvate is the end-product of glycolysis, is derived from additional sources in the cellular cytoplasm, and is ultimately destined for transport into mitochondria as a master fuel input undergirding citric acid cycle carbon flux. In mitochondria, pyruvate drives ATP production by oxidative phosphorylation and multiple biosynthetic pathways intersecting the citric acid cycle. Mitochondrial pyruvate metabolism is regulated by many enzymes, including the recently discovered mitochondria pyruvate carrier, pyruvate dehydrogenase, and pyruvate carboxylase, to modulate overall pyruvate carbon flux. Mutations in any of the genes encoding for proteins regulating pyruvate metabolism may lead to disease. Numerous cases have been described. Aberrant pyruvate metabolism plays an especially prominent role in cancer, heart failure, and neurodegeneration. Because most major diseases involve aberrant metabolism, understanding and exploiting pyruvate carbon flux may yield novel treatments that enhance human health.
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Affiliation(s)
- Lawrence R Gray
- Department of Biochemistry, Fraternal Order of the Eagles Diabetes Research Center, and François M. Abboud Cardiovascular Research Center, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, 51 Newton Rd, 4-403 BSB, Iowa City, IA, 52242, USA
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33
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Functional role of oligomerization for bacterial and plant SWEET sugar transporter family. Proc Natl Acad Sci U S A 2013; 110:E3685-94. [PMID: 24027245 DOI: 10.1073/pnas.1311244110] [Citation(s) in RCA: 198] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Eukaryotic sugar transporters of the MFS and SWEET superfamilies consist of 12 and 7 α-helical transmembrane domains (TMs), respectively. Structural analyses indicate that MFS transporters evolved from a series of tandem duplications of an ancestral 3-TM unit. SWEETs are heptahelical proteins carrying a tandem repeat of 3-TM separated by a single TM. Here, we show that prokaryotes have ancestral SWEET homologs with only 3-TM and that the Bradyrhizobium japonicum SemiSWEET1, like Arabidopsis SWEET11, mediates sucrose transport. Eukaryotic SWEETs most likely evolved by internal duplication of the 3-TM, suggesting that SemiSWEETs form oligomers to create a functional pore. However, it remains elusive whether the 7-TM SWEETs are the functional unit or require oligomerization to form a pore sufficiently large to allow for sucrose passage. Split ubiquitin yeast two-hybrid and split GFP assays indicate that Arabidopsis SWEETs homo- and heterooligomerize. We examined mutant SWEET variants for negative dominance to test if oligomerization is necessary for function. Mutation of the conserved Y57 or G58 in SWEET1 led to loss of activity. Coexpression of the defective mutants with functional A. thaliana SWEET1 inhibited glucose transport, indicating that homooligomerization is necessary for function. Collectively, these data imply that the basic unit of SWEETs, similar to MFS sugar transporters, is a 3-TM unit and that a functional transporter contains at least four such domains. We hypothesize that the functional unit of the SWEET family of transporters possesses a structure resembling the 12-TM MFS structure, however, with a parallel orientation of the 3-TM unit.
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Yuan M, Wang S. Rice MtN3/saliva/SWEET family genes and their homologs in cellular organisms. MOLECULAR PLANT 2013; 6:665-74. [PMID: 23430047 DOI: 10.1093/mp/sst035] [Citation(s) in RCA: 140] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The MtN3/saliva/SWEET-type genes, existing either alone or in a family group, are found in diverse organisms, from monocellular protozoa to higher eukaryotes, indicating their importance in cellular organisms. These genes encode polytopic membrane proteins that feature an MtN3/saliva domain, also known as a PQ loop repeat. The rice MtN3/saliva/SWEET gene family consists of 21 members and is among the largest families in sequenced organisms. Accumulating data suggest that these genes are involved in multiple physiological processes, including reproductive development, senescence, environmental adaptation, and host-pathogen interaction, in different species. In rice, some members of the family, including Xa13/Os8N3/OsSWEET11, which is essential for reproductive development, are used by the pathogenic bacterium Xanthomonas oryzae pv. oryzae to invade its host. Emerging data have also revealed that at least some MtN3/saliva/SWEET-type proteins may regulate different physiological processes by facilitating ion transport via interaction with ion transporters or as sugar transporters. The accumulating knowledge about MtN3/saliva/SWEET-type genes will help to elucidate the molecular bases of their function in different organisms.
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Affiliation(s)
- Meng Yuan
- National Key Laboratory of Crop Genetic Improvement, National Center of Plant Gene Research Wuhan, Huazhong Agricultural University, Wuhan 430070, China
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35
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Thoene J, Goss T, Witcher M, Mullet J, N'Kuli F, Van Der Smissen P, Courtoy P, Hahn SH. In vitro correction of disorders of lysosomal transport by microvesicles derived from baculovirus-infected Spodoptera cells. Mol Genet Metab 2013; 109:77-85. [PMID: 23465695 DOI: 10.1016/j.ymgme.2013.01.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Revised: 01/24/2013] [Accepted: 01/24/2013] [Indexed: 01/29/2023]
Abstract
Infection of Spodoptera frugiperda (Sf9) cells by baculovirus (BV) is well established for transgene expression of soluble proteins, but few correctly folded transmembrane proteins have been so produced. We here report the use of the BV/Sf9 (BVES) method for the expression and transfer, via microvesicles, of the exclusive lysosomal exporters for cystine and sialic acid, human cystinosin and sialin. These proteins and their mRNA are released into the culture medium as very low-density microvesicles (~1.05 g/ml), which do not label for lysobisphosphatidic acid. The presence of the human transgene proteins in the vesicles was confirmed by western blotting and confirmed and quantified by mass spectrometry. Addition of vesicles to cultures of human fibroblast lines deficient in either cystinosin or sialin produced a progressive depletion of stored lysosomal cystine or sialic acid, respectively. The depletion effect was slow (T1/2 ~48 h), saturable (down to ~40% of initial after 4 days) and stable (>one week). Surprisingly, BV infection of Spodoptera appeared to induce expression and release into microvesicles of the insect orthologue of cystinosin, but not of sialin. We conclude that BVES is an effective method to express and transfer functional transmembrane proteins so as to study their properties in mammalian cells, and has a generic potential for transport protein replacement therapy.
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Affiliation(s)
- Jess Thoene
- Department of Pediatric Genetics, University of Michigan, Ann Arbor, MI 48109-5629, USA.
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Henderson MJ, Richie CT, Airavaara M, Wang Y, Harvey BK. Mesencephalic astrocyte-derived neurotrophic factor (MANF) secretion and cell surface binding are modulated by KDEL receptors. J Biol Chem 2012; 288:4209-25. [PMID: 23255601 DOI: 10.1074/jbc.m112.400648] [Citation(s) in RCA: 112] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Mesencephalic astrocyte-derived neurotrophic factor (MANF) is an endoplasmic reticulum (ER) stress-responsive protein with neuroprotective effects in animal models of neurodegeneration, but the underlying mechanism is not understood. We constructed a set of lentiviral vectors that contain or lack the highly conserved final four amino acids of MANF ("RTDL"), which resemble the canonical ER retention signal ("KDEL"), to study MANF regulation in neuroblastoma cells and rat primary cortical neurons. The RTDL sequence was required for both ER retention and secretory response to ER stress. Overexpression of KDEL receptor paralogs (KDELRs) differentially reduced MANF secretion but had no effect on MANF lacking RTDL. MANF binding to the plasma membrane also required the RTDL sequence and was inhibited with a peptide known to interact with KDELRs, suggesting MANF binds KDELRs at the surface. We detected surface localization of FLAG-tagged KDELRs, with levels increasing following ER stress. Our study provides new insight into the regulation of MANF trafficking and has implications for other secreted proteins containing a KDEL-like retention signal.
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Affiliation(s)
- Mark J Henderson
- Intramural Research Program, National Institute on Drug Abuse, Baltimore, Maryland 21224, USA
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Heptahelical protein PQLC2 is a lysosomal cationic amino acid exporter underlying the action of cysteamine in cystinosis therapy. Proc Natl Acad Sci U S A 2012; 109:E3434-43. [PMID: 23169667 DOI: 10.1073/pnas.1211198109] [Citation(s) in RCA: 126] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Cystinosin, the lysosomal cystine exporter defective in cystinosis, is the founding member of a family of heptahelical membrane proteins related to bacteriorhodopsin and characterized by a duplicated motif termed the PQ loop. PQ-loop proteins are more frequent in eukaryotes than in prokaryotes; except for cystinosin, their molecular function remains elusive. In this study, we report that three yeast PQ-loop proteins of unknown function, Ypq1, Ypq2, and Ypq3, localize to the vacuolar membrane and are involved in homeostasis of cationic amino acids (CAAs). We also show that PQLC2, a mammalian PQ-loop protein closely related to yeast Ypq proteins, localizes to lysosomes and catalyzes a robust, electrogenic transport that is selective for CAAs and strongly activated at low extracytosolic pH. Heterologous expression of PQLC2 at the yeast vacuole rescues the resistance phenotype of an ypq2 mutant to canavanine, a toxic analog of arginine efficiently transported by PQLC2. Finally, PQLC2 transports a lysine-like mixed disulfide that serves as a chemical intermediate in cysteamine therapy of cystinosis, and PQLC2 gene silencing trapped this intermediate in cystinotic cells. We conclude that PQLC2 and Ypq1-3 proteins are lysosomal/vacuolar exporters of CAAs and suggest that small-molecule transport is a conserved feature of the PQ-loop protein family, in agreement with its distant similarity to SWEET sugar transporters and to the mitochondrial pyruvate carrier. The elucidation of PQLC2 function may help improve cysteamine therapy. It may also clarify the origin of CAA abnormalities in Batten disease.
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