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Sah SK, Shefali S, Yadav A, Som P, Komath SS. The caspase-like Gpi8 subunit of Candida albicans GPI transamidase is a metal-dependent endopeptidase. Biochem Biophys Res Commun 2020; 525:S0006-291X(20)30268-0. [PMID: 32081427 DOI: 10.1016/j.bbrc.2020.02.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 02/03/2020] [Indexed: 10/25/2022]
Abstract
GPI anchored proteins (GPI-APs) act at the frontiers of cells, decoding environmental cues and determining host-pathogen interactions in several lower eukaryotes. They are also essential for viability in lower eukaryotes. The GPI biosynthetic pathway begins at the ER and follows a roughly linear pathway to generate the complete precursor (CP) glycolipid. The GPI transamidase (GPIT) transfers this glycolipid to the C-terminal end of newly translated proteins after removing their GPI attachment signal sequence (SS). The GPIT subunit that cleaves SS is Gpi8, a protein with a conserved Cys/His catalytic dyad typical of cysteine proteases. A CaGPI8 heterozygous mutant accumulates CPs and has reduced cell surface GPI-APs. Using a simple cell-free assay, we demonstrate that the heterozygous CaGPI8 strain has low endopeptidase activity as well. The revertant strain is restored in all these phenotypes. CaGpi8 is also shown to be a metalloenzyme, whose protease activity is sensitive to agents that modify Cys/His residues.
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Affiliation(s)
- Sudisht Kumar Sah
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, 110067, India
| | - Shailja Shefali
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, 110067, India
| | - Anshuman Yadav
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, 110067, India
| | - Punnag Som
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, 110067, India
| | - Sneha Sudha Komath
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, 110067, India.
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Chen JJ, Boehning D. Protein Lipidation As a Regulator of Apoptotic Calcium Release: Relevance to Cancer. Front Oncol 2017; 7:138. [PMID: 28706877 PMCID: PMC5489567 DOI: 10.3389/fonc.2017.00138] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Accepted: 06/16/2017] [Indexed: 12/16/2022] Open
Abstract
Calcium is a critical regulator of cell death pathways. One of the most proximal events leading to cell death is activation of plasma membrane and endoplasmic reticulum-resident calcium channels. A large body of evidence indicates that defects in this pathway contribute to cancer development. Although we have a thorough understanding of how downstream elevations in cytosolic and mitochondrial calcium contribute to cell death, it is much less clear how calcium channels are activated upstream of the apoptotic stimulus. Recently, it has been shown that protein lipidation is a potent regulator of apoptotic signaling. Although classically thought of as a static modification, rapid and reversible protein acylation has emerged as a new signaling paradigm relevant to many pathways, including calcium release and cell death. In this review, we will discuss the role of protein lipidation in regulating apoptotic calcium signaling with direct therapeutic relevance to cancer.
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Affiliation(s)
- Jessica J Chen
- Department of Biochemistry and Molecular Biology, McGovern Medical School, UTHealth, Houston, TX, United States
| | - Darren Boehning
- Department of Biochemistry and Molecular Biology, McGovern Medical School, UTHealth, Houston, TX, United States
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Gamage DG, Hendrickson TL. GPI Transamidase and GPI anchored proteins: Oncogenes and biomarkers for cancer. Crit Rev Biochem Mol Biol 2013; 48:446-64. [DOI: 10.3109/10409238.2013.831024] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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Galian C, Björkholm P, Bulleid N, von Heijne G. Efficient glycosylphosphatidylinositol (GPI) modification of membrane proteins requires a C-terminal anchoring signal of marginal hydrophobicity. J Biol Chem 2012; 287:16399-409. [PMID: 22431723 PMCID: PMC3351287 DOI: 10.1074/jbc.m112.350009] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2012] [Revised: 03/16/2012] [Indexed: 11/06/2022] Open
Abstract
Many plasma membrane proteins are anchored to the membrane via a C-terminal glycosylphosphatidylinositol (GPI) moiety. The GPI anchor is attached to the protein in the endoplasmic reticulum by transamidation, a reaction in which a C-terminal GPI-attachment signal is cleaved off concomitantly with addition of the GPI moiety. GPI-attachment signals are poorly conserved on the sequence level but are all composed of a polar segment that includes the GPI-attachment site followed by a hydrophobic segment located at the very C terminus of the protein. Here, we show that efficient GPI modification requires that the hydrophobicity of the C-terminal segment is "marginal": less hydrophobic than type II transmembrane anchors and more hydrophobic than the most hydrophobic segments found in secreted proteins. We further show that the GPI-attachment signal can be modified by the transamidase irrespective of whether it is first released into the lumen of the endoplasmic reticulum or is retained in the endoplasmic reticulum membrane.
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Affiliation(s)
- Carmen Galian
- From the Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University SE-106 91 Stockholm, Sweden
| | - Patrik Björkholm
- From the Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University SE-106 91 Stockholm, Sweden
| | - Neil Bulleid
- the Institute of Molecular, Cell and Systems Biology, CMVLS, University of Glasgow, Glasgow, G12 8QQ Scotland, United Kingdom, and
| | - Gunnar von Heijne
- From the Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University SE-106 91 Stockholm, Sweden
- the Science for Life Laboratory, Stockholm University, SE-171 77 Solna, Sweden
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John F, Hendrickson TL. Synthesis of truncated analogues for studying the process of glycosyl phosphatidylinositol modification. Org Lett 2010; 12:2080-3. [PMID: 20380381 DOI: 10.1021/ol100575q] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Many eukaryotic proteins are modified with a glycosylphosphatidylinositol (GPI) anchor at their C-termini. This post-translational modification causes these proteins to be noncovalently tethered to the plasma membrane. The synthesis of truncated GPI anchor analogues is reported; these compounds were designed for use as soluble substrates for GPI transamidase (GPI-T), the enzyme that appends the GPI anchor onto proteins.
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Affiliation(s)
- Franklin John
- Department of Chemistry, 5101 Cass Avenue, Wayne State University, Detroit, Michigan 48202, USA
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Ashok A, Hegde RS. Retrotranslocation of prion proteins from the endoplasmic reticulum by preventing GPI signal transamidation. Mol Biol Cell 2008; 19:3463-76. [PMID: 18508914 DOI: 10.1091/mbc.e08-01-0087] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Neurodegeneration in diseases caused by altered metabolism of mammalian prion protein (PrP) can be averted by reducing PrP expression. To identify novel pathways for PrP down-regulation, we analyzed cells that had adapted to the negative selection pressure of stable overexpression of a disease-causing PrP mutant. A mutant cell line was isolated that selectively and quantitatively routes wild-type and various mutant PrPs for ER retrotranslocation and proteasomal degradation. Biochemical analyses of the mutant cells revealed that a defect in glycosylphosphatidylinositol (GPI) anchor synthesis leads to an unprocessed GPI-anchoring signal sequence that directs both ER retention and efficient retrotranslocation of PrP. An unprocessed GPI signal was sufficient to impart ER retention, but not retrotranslocation, to a heterologous protein, revealing an unexpected role for the mature domain in the metabolism of misprocessed GPI-anchored proteins. Our results provide new insights into the quality control pathways for unprocessed GPI-anchored proteins and identify transamidation of the GPI signal sequence as a step in PrP biosynthesis that is absolutely required for its surface expression. As each GPI signal sequence is unique, these results also identify signal recognition by the GPI-transamidase as a potential step for selective small molecule perturbation of PrP expression.
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Affiliation(s)
- Aarthi Ashok
- Cell Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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Meitzler JL, Gray JJ, Hendrickson TL. Truncation of the caspase-related subunit (Gpi8p) of Saccharomyces cerevisiae GPI transamidase: Dimerization revealed. Arch Biochem Biophys 2007; 462:83-93. [PMID: 17475206 DOI: 10.1016/j.abb.2007.03.035] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2007] [Revised: 03/15/2007] [Accepted: 03/16/2007] [Indexed: 11/24/2022]
Abstract
Eukaryotic proteins can be post-translationally modified with a glycosylphosphatidylinositol (GPI) membrane anchor. This modification reaction is catalyzed by GPI transamidase (GPI-T), a multimeric, membrane-bound enzyme. Gpi8p, an essential component of GPI-T, shares low sequence similarity with caspases and contains all or part of the enzyme's active site [U. Meyer, M. Benghezal, I. Imhof, A. Conzelmann, Biochemistry 39 (2000) 3461-3471]. Structural predictions suggest that the soluble portion of Gpi8p is divided into two domains: a caspase-like domain that contains the active site machinery and a second, smaller domain of unknown function. Based on these predictions, we evaluated a soluble truncation of Gpi8p (Gpi8(23-306)). Dimerization was investigated due to the known proclivity of caspases to homodimerize; a Gpi8(23-306) homodimer was detected by native gel and confirmed by mass spectrometry and N-terminal sequencing. Mutations at the putative caspase-like dimerization interface disrupted dimer formation. When combined, these results demonstrate an organizational similarity between Gpi8p and caspases.
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Affiliation(s)
- Jennifer L Meitzler
- Department of Chemistry, Remsen Hall, Johns Hopkins University, Baltimore, MD 21218, USA
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Nicholson TB, Stanners CP. Identification of a novel functional specificity signal within the GPI anchor signal sequence of carcinoembryonic antigen. ACTA ACUST UNITED AC 2007; 177:211-8. [PMID: 17438079 PMCID: PMC2064130 DOI: 10.1083/jcb.200701158] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Exchanging the glycophosphatidylinositol (GPI) anchor signal sequence of neural cell adhesion molecule (NCAM) for the signal sequence of carcinoembryonic antigen (CEA) generates a mature protein with NCAM external domains but CEA-like tumorigenic activity. We hypothesized that this resulted from the presence of a functional specificity signal within this sequence and generated CEA/NCAM chimeras to identify this signal. Replacing the residues (GLSAG) 6–10 amino acids downstream of the CEA anchor addition site with the corresponding NCAM residues resulted in GPI-anchored proteins lacking the CEA-like biological functions of integrin modulation and differentiation blockage. Transferring this region from CEA into NCAM in conjunction with the upstream proline (PGLSAG) was sufficient to specify the addition of the CEA anchor. Therefore, this study identifies a novel specificity signal consisting of six amino acids located within the GPI anchor attachment signal, which is necessary and sufficient to specify the addition of a particular functional GPI anchor and, thereby, the ultimate function of the mature protein.
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Affiliation(s)
- Thomas B Nicholson
- McGill Cancer Centre and 2Biochemistry Department, McGill University, Montréal, Québec H3G 1Y6, Canada
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Orlean P, Menon AK. Thematic review series: lipid posttranslational modifications. GPI anchoring of protein in yeast and mammalian cells, or: how we learned to stop worrying and love glycophospholipids. J Lipid Res 2007; 48:993-1011. [PMID: 17361015 DOI: 10.1194/jlr.r700002-jlr200] [Citation(s) in RCA: 268] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Glycosylphosphatidylinositol (GPI) anchoring of cell surface proteins is the most complex and metabolically expensive of the lipid posttranslational modifications described to date. The GPI anchor is synthesized via a membrane-bound multistep pathway in the endoplasmic reticulum (ER) requiring >20 gene products. The pathway is initiated on the cytoplasmic side of the ER and completed in the ER lumen, necessitating flipping of a glycolipid intermediate across the membrane. The completed GPI anchor is attached to proteins that have been translocated across the ER membrane and that display a GPI signal anchor sequence at the C terminus. GPI proteins transit the secretory pathway to the cell surface; in yeast, many become covalently attached to the cell wall. Genes encoding proteins involved in all but one of the predicted steps in the assembly of the GPI precursor glycolipid and its transfer to protein in mammals and yeast have now been identified. Most of these genes encode polytopic membrane proteins, some of which are organized in complexes. The steps in GPI assembly, and the enzymes that carry them out, are highly conserved. GPI biosynthesis is essential for viability in yeast and for embryonic development in mammals. In this review, we describe the biosynthesis of mammalian and yeast GPIs, their transfer to protein, and their subsequent processing.
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Affiliation(s)
- Peter Orlean
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
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Jung HR, Jensen ON. Proteomic analysis of GPI-anchored membrane proteins. DRUG DISCOVERY TODAY. TECHNOLOGIES 2006; 3:339-346. [PMID: 24980538 DOI: 10.1016/j.ddtec.2006.09.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Glycosyl-phosphatidyl-inositol-anchored proteins (GPI-APs) represent a subset of post-translationally modified proteins that are tethered to the outer leaflet of the plasma membrane via a C-terminal GPI anchor. GPI-APs are found in a variety of eukaryote species, from pathogenic microorganisms to humans. GPI-APs confer important cellular functions as receptors, enzymes and scaffolding molecules. Specific enzymes and detergent extraction methods combined with separation technologies and mass spectrometry permit proteomic analysis of GPI-APs from plasma membrane preparations to reveal cell-type specific surface molecules, candidate biomarkers and potential therapeutic targets.:
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Affiliation(s)
- Hye Ryung Jung
- Protein Research Group, Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230, Odense M, Denmark
| | - Ole Nørregaard Jensen
- Protein Research Group, Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230, Odense M, Denmark.
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Vainauskas S, Menon AK. A Conserved Proline in the Last Transmembrane Segment of Gaa1 Is Required for Glycosylphosphatidylinositol (GPI) Recognition by GPI Transamidase. J Biol Chem 2004; 279:6540-5. [PMID: 14660601 DOI: 10.1074/jbc.m312191200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Glycosylphosphatidylinositol (GPI)-anchored proteins are synthesized as precursor proteins that are processed in the endoplasmic reticulum by GPI transamidase (GPIT). Human GPIT is a multisubunit membrane-bound protein complex consisting of Gaa1, Gpi8, phosphatidylinositol glycan (PIG)-S, PIG-T, and PIG-U. The enzyme recognizes a C-terminal signal sequence in the proprotein and replaces it with a preformed GPI lipid. The nature of the functional interaction of the GPIT subunits with each other and with the proprotein and GPI substrates is largely unknown. We recently analyzed the GPIT subunit Gaa1, a polytopic protein with seven transmembrane (TM) spans, to identify sequence determinants in the protein that are required for its interaction with other subunits and for function (Vainauskas, S., Maeda, Y., Kurniawan, H., Kinoshita, T., and Menon, A. K. (2002) J. Biol. Chem. 277, 30535-30542). We showed that elimination of the C-terminal TM segment of Gaa1 allows the protein to interact with Gpi8, PIG-S, and PIG-T but renders the resulting GPIT complex nonfunctional. We now show that GPIT complexes containing C-terminally truncated Gaa1 possess a full complement of subunits and are able to interact with a proprotein substrate but cannot co-immunoprecipitate GPI. We go on to show that mutation of a conserved proline residue centrally located within the C-terminal TM span of Gaa1 is sufficient to abrogate the ability of the resulting GPIT complex to co-immunoprecipitate GPI. We suggest that the putative dynamic hinge created by the proline residue provides a structural basis for the interaction of GPI with GPIT.
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Affiliation(s)
- Saulius Vainauskas
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706-1544, USA.
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