1
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Gingras RM, Sulpizio AM, Park J, Bretscher A. High-resolution secretory timeline from vesicle formation at the Golgi to fusion at the plasma membrane in S. cerevisiae. eLife 2022; 11:e78750. [PMID: 36331188 PMCID: PMC9671497 DOI: 10.7554/elife.78750] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 11/03/2022] [Indexed: 11/06/2022] Open
Abstract
Most of the components in the yeast secretory pathway have been studied, yet a high-resolution temporal timeline of their participation is lacking. Here, we define the order of acquisition, lifetime, and release of critical components involved in late secretion from the Golgi to the plasma membrane. Of particular interest is the timing of the many reported effectors of the secretory vesicle Rab protein Sec4, including the myosin-V Myo2, the exocyst complex, the lgl homolog Sro7, and the small yeast-specific protein Mso1. At the trans-Golgi network (TGN) Sec4's GEF, Sec2, is recruited to Ypt31-positive compartments, quickly followed by Sec4 and Myo2 and vesicle formation. While transported to the bud tip, the entire exocyst complex, including Sec3, is assembled on to the vesicle. Before fusion, vesicles tether for 5 s, during which the vesicle retains the exocyst complex and stimulates lateral recruitment of Rho3 on the plasma membrane. Sec2 and Myo2 are rapidly lost, followed by recruitment of cytosolic Sro7, and finally the SM protein Sec1, which appears for just 2 s prior to fusion. Perturbation experiments reveal an ordered and robust series of events during tethering that provide insights into the function of Sec4 and effector exchange.
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Affiliation(s)
- Robert M Gingras
- Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell UniversityIthacaUnited States
| | - Abigail M Sulpizio
- Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell UniversityIthacaUnited States
| | - Joelle Park
- Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell UniversityIthacaUnited States
| | - Anthony Bretscher
- Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell UniversityIthacaUnited States
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2
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Pallares R, An DD, Hébert S, Loguinov A, Proctor M, Villalobos JA, Bjornstad KA, Rosen CJ, Vulpe CD, Abergel RJ. Identifying Toxicity Mechanisms Associated with Early Lanthanide Exposure through Multidimensional Genome-Wide Screening. ACS OMEGA 2022; 7:34412-34419. [PMID: 36188298 PMCID: PMC9521019 DOI: 10.1021/acsomega.2c04045] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Accepted: 09/01/2022] [Indexed: 06/16/2023]
Abstract
Lanthanides are a series of elements essential to a wide range of applications, from clean energy production to healthcare. Despite their presence in multiple products and technologies, their toxicological characteristics have been only partly studied. Recently, our group has employed a genomic approach to extensively characterize the toxicity mechanisms of lanthanides. Even though we identified substantially different behaviors for mid and late lanthanides, the toxicological profiles of early lanthanides remained elusive. Here, we overcome this gap by describing a multidimensional genome-wide toxicogenomic study for two early lanthanides, namely, lanthanum and praseodymium. We used Saccharomyces cerevisiae as a model system since its genome shares many biological pathways with humans. By performing functional analysis and protein-protein interaction network analysis, we identified the main genes and proteins that participate in the yeast response to counter metal harmful effects. Moreover, our analysis also highlighted key enzymes that are dysregulated by early lanthanides, inducing cytotoxicity. Several of these genes and proteins have human orthologues, indicating that they may also participate in the human response against the metals. By highlighting the key genes and proteins in lanthanide-induced toxicity, this work may contribute to the development of new prophylactic and therapeutic strategies against lanthanide harmful exposures.
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Affiliation(s)
- Roger
M. Pallares
- Chemical
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
| | - Dahlia D. An
- Chemical
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
| | - Solène Hébert
- Chemical
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
| | - Alex Loguinov
- Center
for Environmental and Human Toxicology, Department of Physiological
Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida 32611, United States
| | - Michael Proctor
- Center
for Environmental and Human Toxicology, Department of Physiological
Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida 32611, United States
| | - Jonathan A. Villalobos
- Chemical
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
| | - Kathleen A. Bjornstad
- Chemical
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
| | - Chris J. Rosen
- Chemical
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
| | - Chris D. Vulpe
- Center
for Environmental and Human Toxicology, Department of Physiological
Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida 32611, United States
| | - Rebecca J. Abergel
- Chemical
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
- Department
of Nuclear Engineering, University of California, Berkeley, California 94720, United States
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3
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Pallares RM, An DD, Hébert S, Faulkner D, Loguinov A, Proctor M, Villalobos JA, Bjornstad KA, Rosen CJ, Vulpe C, Abergel RJ. Delineating toxicity mechanisms associated with MRI contrast enhancement through a multidimensional toxicogenomic profiling of gadolinium. Mol Omics 2022; 18:237-248. [PMID: 35040455 DOI: 10.1039/d1mo00267h] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Gadolinium is a metal used in contrast agents for magnetic resonance imaging. Although gadolinium is widely used in clinical settings, many concerns regarding its toxicity and bioaccumulation after gadolinium-based contrast agent administration have been raised and published over the last decade. To date, most toxicological studies have focused on identifying acute effects following gadolinium exposure, rather than investigating associated toxicity mechanisms. In this study, we employ functional toxicogenomics to assess mechanistic interactions of gadolinium with Saccharomyces cerevisiae. Furthermore, we determine which mechanisms are conserved in humans, and their implications for diseases related to the use of gadolinium-based contrast agents in medicine. A homozygous deletion pool of 4291 strains were screened to identify biological functions and pathways disturbed by the metal. Gene ontology and pathway enrichment analyses showed endocytosis and vesicle-mediated transport as the main yeast response to gadolinium, while certain metabolic processes, such as glycosylation, were the primary disrupted functions after the metal treatments. Cluster and protein-protein interaction network analyses identified proteins mediating vesicle-mediated transport through the Golgi apparatus and the vacuole, and vesicle cargo exocytosis as key components to reduce the metal toxicity. Moreover, the metal seemed to induce cytotoxicity by disrupting the function of enzymes (e.g. transferases and proteases) and chaperones involved in metabolic processes. Several of the genes and proteins associated with gadolinium toxicity are conserved in humans, suggesting that they may participate in pathologies linked to gadolinium-based contrast agent exposures. We thereby discuss the potential role of these conserved genes and gene products in gadolinium-induced nephrogenic systemic fibrosis, and propose potential prophylactic strategies to prevent its adverse health effects.
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Affiliation(s)
- Roger M Pallares
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
| | - Dahlia D An
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
| | - Solène Hébert
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
| | - David Faulkner
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
| | - Alex Loguinov
- Center for Environmental and Human Toxicology, Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, 32611, USA
| | - Michael Proctor
- Center for Environmental and Human Toxicology, Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, 32611, USA
| | - Jonathan A Villalobos
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
| | - Kathleen A Bjornstad
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
| | - Chris J Rosen
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
| | - Christopher Vulpe
- Center for Environmental and Human Toxicology, Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, 32611, USA
| | - Rebecca J Abergel
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA. .,Department of Nuclear Engineering, University of California, Berkeley, CA, 94720, USA
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4
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Pallares RM, An DD, Hébert S, Faulkner D, Loguinov A, Proctor M, Villalobos JA, Bjornstad KA, Rosen CJ, Vulpe C, Abergel RJ. Multidimensional genome-wide screening in yeast provides mechanistic insights into europium toxicity. Metallomics 2021; 13:6409834. [PMID: 34694395 DOI: 10.1093/mtomcs/mfab061] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Accepted: 10/19/2021] [Indexed: 11/13/2022]
Abstract
Europium is a lanthanide metal that is highly valued in optoelectronics. Even though europium is used in many commercial products, its toxicological profile has only been partially characterized, with most studies focusing on identifying lethal doses in different systems or bioaccumulation in vivo. This paper describes a genome-wide toxicogenomic study of europium in Saccharomyces cerevisiae, which shares many biological functions with humans. By using a multidimensional approach and functional and network analyses, we have identified a group of genes and proteins associated with the yeast responses to ameliorate metal toxicity, which include metal discharge paths through vesicle-mediated transport, paths to regulate biologically relevant cations, and processes to reduce metal-induced stress. Furthermore, the analyses indicated that europium promotes yeast toxicity by disrupting the function of chaperones and cochaperones, which have metal-binding sites. Several of the genes and proteins highlighted in our study have human orthologues, suggesting they may participate in europium-induced toxicity in humans. By identifying the endogenous targets of europium as well as the already existing paths that can decrease its toxicity, we can determine specific genes and proteins that may help to develop future therapeutic strategies.
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Affiliation(s)
- Roger M Pallares
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Dahlia D An
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Solène Hébert
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - David Faulkner
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Alex Loguinov
- Center for Environmental and Human Toxicology, Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32611, USA
| | - Michael Proctor
- Center for Environmental and Human Toxicology, Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32611, USA
| | - Jonathan A Villalobos
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Kathleen A Bjornstad
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Chris J Rosen
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Christopher Vulpe
- Center for Environmental and Human Toxicology, Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32611, USA
| | - Rebecca J Abergel
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.,Department of Nuclear Engineering, University of California, Berkeley, CA 94720, USA
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5
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Gerien KS, Zhang S, Russell AC, Zhu YH, Purde V, Wu JQ. Roles of Mso1 and the SM protein Sec1 in efficient vesicle fusion during fission yeast cytokinesis. Mol Biol Cell 2020; 31:1570-1583. [PMID: 32432970 PMCID: PMC7521796 DOI: 10.1091/mbc.e20-01-0067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Membrane trafficking during cytokinesis is essential for the delivery of membrane lipids and cargoes to the division site. However, the molecular mechanisms are still incompletely understood. In this study, we demonstrate the importance of uncharacterized fission yeast proteins Mso1 and Sec1 in membrane trafficking during cytokinesis. Fission yeast Mso1 shares homology with budding yeast Mso1 and human Mint1, proteins that interact with Sec1/Munc18 family proteins during vesicle fusion. Sec1/Munc18 proteins and their interactors are important regulators of SNARE complex formation during vesicle fusion. The roles of these proteins in vesicle trafficking during cytokinesis have been barely studied. Here, we show that fission yeast Mso1 is also a Sec1-binding protein and Mso1 and Sec1 localize to the division site interdependently during cytokinesis. The loss of Sec1 localization in mso1Δ cells results in a decrease in vesicle fusion and cytokinesis defects such as slow ring constriction, defective ring disassembly, and delayed plasma membrane closure. We also find that Mso1 and Sec1 may have functions independent of the exocyst tethering complex on the plasma membrane at the division site. Together, Mso1 and Sec1 play essential roles in regulating vesicle fusion and cargo delivery at the division site during cytokinesis.
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Affiliation(s)
- Kenneth S Gerien
- Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210.,Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210
| | - Sha Zhang
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210
| | - Alexandra C Russell
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210
| | - Yi-Hua Zhu
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210
| | - Vedud Purde
- Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210.,Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210
| | - Jian-Qiu Wu
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210.,Department of Biological Chemistry and Pharmacology, The Ohio State University, Columbus, OH 43210
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6
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Applications of the Bacteriophage Mu In Vitro Transposition Reaction and Genome Manipulation via Electroporation of DNA Transposition Complexes. Methods Mol Biol 2018; 1681:279-286. [PMID: 29134602 DOI: 10.1007/978-1-4939-7343-9_20] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The capacity of transposable elements to insert into the genomes has been harnessed during the past decades to various in vitro and in vivo applications. This chapter describes in detail the general protocols and principles applicable for the Mu in vitro transposition reaction as well as the assembly of DNA transposition complexes that can be electroporated into bacterial cells to accomplish efficient gene delivery. These techniques with their modifications potentiate various gene and genome modification applications, which are discussed briefly here, and the reader is referred to the original publications for further details.
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7
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Weber-Boyvat M, Chernov KG, Aro N, Wohlfahrt G, Olkkonen VM, Jäntti J. The Sec1/Munc18 Protein Groove Plays a Conserved Role in Interaction with Sec9p/SNAP-25. Traffic 2015; 17:131-53. [PMID: 26572066 DOI: 10.1111/tra.12349] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Revised: 11/12/2015] [Accepted: 11/12/2015] [Indexed: 12/17/2022]
Abstract
The Sec1/Munc18 (SM) proteins constitute a conserved family with essential functions in SNARE-mediated membrane fusion. Recently, a new protein-protein interaction site in Sec1p, designated the groove, was proposed. Here, we show that a sec1 groove mutant yeast strain, sec1(w24), displays temperature-sensitive growth and secretion defects. The yeast Sec1p and mammalian Munc18-1 grooves were shown to play an important role in the interaction with the SNAREs Sec9p and SNAP-25b, respectively. Incubation of SNAP-25b with the Munc18-1 groove mutant resulted in a lag in the kinetics of SNARE complex assembly in vitro when compared with wild-type Munc18-1. The SNARE regulator SRO7 was identified as a multicopy suppressor of sec1(w24) groove mutant and an intact Sec1p groove was required for the plasma membrane targeting of Sro7p-SNARE complexes. Simultaneous inactivation of Sec1p groove and SRO7 resulted in reduced levels of exocytic SNARE complexes. Our results identify the groove as a conserved interaction surface in SM proteins. The results indicate that this structural element is important for interactions with Sec9p/SNAP-25 and participates, in concert with Sro7p, in the initial steps of SNARE complex assembly.
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Affiliation(s)
- Marion Weber-Boyvat
- Cell and Molecular Biology Program, Institute of Biotechnology, University of Helsinki, P.O. Box 56, FI-00014, Helsinki, Finland.,Minerva Foundation Institute for Medical Research, Tukholmankatu 8, FI-00290, Helsinki, Finland
| | - Konstantin G Chernov
- Cell and Molecular Biology Program, Institute of Biotechnology, University of Helsinki, P.O. Box 56, FI-00014, Helsinki, Finland
| | - Nina Aro
- Cell and Molecular Biology Program, Institute of Biotechnology, University of Helsinki, P.O. Box 56, FI-00014, Helsinki, Finland.,VTT Technical Research Centre of Finland, Tietotie 2, FIN 02044 VTT, Espoo, Finland
| | - Gerd Wohlfahrt
- Computer-Aided Drug Design, Orion Pharma, P.O. Box 65, 02101, Espoo, Finland
| | - Vesa M Olkkonen
- Minerva Foundation Institute for Medical Research, Tukholmankatu 8, FI-00290, Helsinki, Finland
| | - Jussi Jäntti
- Cell and Molecular Biology Program, Institute of Biotechnology, University of Helsinki, P.O. Box 56, FI-00014, Helsinki, Finland.,VTT Technical Research Centre of Finland, Tietotie 2, FIN 02044 VTT, Espoo, Finland
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8
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Weber-Boyvat M, Zhao H, Aro N, Yuan Q, Chernov K, Peränen J, Lappalainen P, Jäntti J. A conserved regulatory mode in exocytic membrane fusion revealed by Mso1p membrane interactions. Mol Biol Cell 2012. [PMID: 23197474 PMCID: PMC3564535 DOI: 10.1091/mbc.e12-05-0415] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Sec1/Munc18 family proteins are important components of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex-mediated membrane fusion processes. However, the molecular interactions and the mechanisms involved in Sec1p/Munc18 control and SNARE complex assembly are not well understood. We provide evidence that Mso1p, a Sec1p- and Sec4p-binding protein, interacts with membranes to regulate membrane fusion. We identify two membrane-binding sites on Mso1p. The N-terminal region inserts into the lipid bilayer and appears to interact with the plasma membrane, whereas the C-terminal region of the protein binds phospholipids mainly through electrostatic interactions and may associate with secretory vesicles. The Mso1p membrane interactions are essential for correct subcellular localization of Mso1p-Sec1p complexes and for membrane fusion in Saccharomyces cerevisiae. These characteristics are conserved in the phosphotyrosine-binding (PTB) domain of β-amyloid precursor protein-binding Mint1, the mammalian homologue of Mso1p. Both Mint1 PTB domain and Mso1p induce vesicle aggregation/clustering in vitro, supporting a role in a membrane-associated process. The results identify Mso1p as a novel lipid-interacting protein in the SNARE complex assembly machinery. Furthermore, our data suggest that a general mode of interaction, consisting of a lipid-binding protein, a Rab family GTPase, and a Sec1/Munc18 family protein, is important in all SNARE-mediated membrane fusion events.
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Affiliation(s)
- Marion Weber-Boyvat
- Cell and Molecular Biology Program, Institute of Biotechnology, FI-00014 University of Helsinki, Helsinki, Finland
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9
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Diversity in genetic in vivo methods for protein-protein interaction studies: from the yeast two-hybrid system to the mammalian split-luciferase system. Microbiol Mol Biol Rev 2012; 76:331-82. [PMID: 22688816 DOI: 10.1128/mmbr.05021-11] [Citation(s) in RCA: 133] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The yeast two-hybrid system pioneered the field of in vivo protein-protein interaction methods and undisputedly gave rise to a palette of ingenious techniques that are constantly pushing further the limits of the original method. Sensitivity and selectivity have improved because of various technical tricks and experimental designs. Here we present an exhaustive overview of the genetic approaches available to study in vivo binary protein interactions, based on two-hybrid and protein fragment complementation assays. These methods have been engineered and employed successfully in microorganisms such as Saccharomyces cerevisiae and Escherichia coli, but also in higher eukaryotes. From single binary pairwise interactions to whole-genome interactome mapping, the self-reassembly concept has been employed widely. Innovative studies report the use of proteins such as ubiquitin, dihydrofolate reductase, and adenylate cyclase as reconstituted reporters. Protein fragment complementation assays have extended the possibilities in protein-protein interaction studies, with technologies that enable spatial and temporal analyses of protein complexes. In addition, one-hybrid and three-hybrid systems have broadened the types of interactions that can be studied and the findings that can be obtained. Applications of these technologies are discussed, together with the advantages and limitations of the available assays.
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10
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Rasila TS, Vihinen M, Paulin L, Haapa-Paananen S, Savilahti H. Flexibility in MuA transposase family protein structures: functional mapping with scanning mutagenesis and sequence alignment of protein homologues. PLoS One 2012; 7:e37922. [PMID: 22666413 PMCID: PMC3362531 DOI: 10.1371/journal.pone.0037922] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Accepted: 04/26/2012] [Indexed: 12/13/2022] Open
Abstract
MuA transposase protein is a member of the retroviral integrase superfamily (RISF). It catalyzes DNA cleavage and joining reactions via an initial assembly and subsequent structural transitions of a protein-DNA complex, known as the Mu transpososome, ultimately attaching transposon DNA to non-specific target DNA. The transpososome functions as a molecular DNA-modifying machine and has been used in a wide variety of molecular biology and genetics/genomics applications. To analyze structure-function relationships in MuA action, a comprehensive pentapeptide insertion mutagenesis was carried out for the protein. A total of 233 unique insertion variants were generated, and their activity was analyzed using a quantitative in vivo DNA transposition assay. The results were then correlated with the known MuA structures, and the data were evaluated with regard to the protein domain function and transpososome development. To complement the analysis with an evolutionary component, a protein sequence alignment was produced for 44 members of MuA family transposases. Altogether, the results pinpointed those regions, in which insertions can be tolerated, and those where insertions are harmful. Most insertions within the subdomains Iγ, IIα, IIβ, and IIIα completely destroyed the transposase function, yet insertions into certain loop/linker regions of these subdomains increased the protein activity. Subdomains Iα and IIIβ were largely insertion-tolerant. The comprehensive structure-function data set will be useful for designing MuA transposase variants with improved properties for biotechnology/genomics applications, and is informative with regard to the function of RISF proteins in general.
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Affiliation(s)
- Tiina S. Rasila
- Institute of Biotechnology, Viikki Biocenter, University of Helsinki, Helsinki, Finland
| | - Mauno Vihinen
- Institute of Biomedical Technology, University of Tampere, Tampere, Finland
- BioMediTech, Tampere, Finland
- Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Lars Paulin
- Institute of Biotechnology, Viikki Biocenter, University of Helsinki, Helsinki, Finland
| | - Saija Haapa-Paananen
- Institute of Biotechnology, Viikki Biocenter, University of Helsinki, Helsinki, Finland
| | - Harri Savilahti
- Institute of Biotechnology, Viikki Biocenter, University of Helsinki, Helsinki, Finland
- Division of Genetics and Physiology, Department of Biology, University of Turku, Turku, Finland
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11
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Morgera F, Sallah MR, Dubuke ML, Gandhi P, Brewer DN, Carr CM, Munson M. Regulation of exocytosis by the exocyst subunit Sec6 and the SM protein Sec1. Mol Biol Cell 2011; 23:337-46. [PMID: 22114349 PMCID: PMC3258177 DOI: 10.1091/mbc.e11-08-0670] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The Sec6 subunit of the multisubunit exocyst tethering complex interacts with the Sec1/Munc18 protein Sec1 and with the t-SNARE Sec9. Assembly of the exocyst upon vesicle arrival at sites of secretion is proposed to release Sec9 for SNARE complex assembly and to recruit Sec1 for interaction with SNARE complexes to facilitate fusion. Trafficking of protein and lipid cargo through the secretory pathway in eukaryotic cells is mediated by membrane-bound vesicles. Secretory vesicle targeting and fusion require a conserved multisubunit protein complex termed the exocyst, which has been implicated in specific tethering of vesicles to sites of polarized exocytosis. The exocyst is directly involved in regulating soluble N-ethylmaleimide–sensitive factor (NSF) attachment protein receptor (SNARE) complexes and membrane fusion through interactions between the Sec6 subunit and the plasma membrane SNARE protein Sec9. Here we show another facet of Sec6 function—it directly binds Sec1, another SNARE regulator, but of the Sec1/Munc18 family. The Sec6–Sec1 interaction is exclusive of Sec6–Sec9 but compatible with Sec6–exocyst assembly. In contrast, the Sec6–exocyst interaction is incompatible with Sec6–Sec9. Therefore, upon vesicle arrival, Sec6 is proposed to release Sec9 in favor of Sec6–exocyst assembly and to simultaneously recruit Sec1 to sites of secretion for coordinated SNARE complex formation and membrane fusion.
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Affiliation(s)
- Francesca Morgera
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA
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12
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Graham ME, Prescott GR, Johnson JR, Jones M, Walmesley A, Haynes LP, Morgan A, Burgoyne RD, Barclay JW. Structure-function study of mammalian Munc18-1 and C. elegans UNC-18 implicates domain 3b in the regulation of exocytosis. PLoS One 2011; 6:e17999. [PMID: 21445306 PMCID: PMC3061876 DOI: 10.1371/journal.pone.0017999] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2010] [Accepted: 02/22/2011] [Indexed: 11/19/2022] Open
Abstract
Munc18-1 is an essential synaptic protein functioning during multiple stages of the exocytotic process including vesicle recruitment, docking and fusion. These functions require a number of distinct syntaxin-dependent interactions; however, Munc18-1 also regulates vesicle fusion via syntaxin-independent interactions with other exocytotic proteins. Although the structural regions of the Munc18-1 protein involved in closed-conformation syntaxin binding have been thoroughly examined, regions of the protein involved in other interactions are poorly characterised. To investigate this we performed a random transposon mutagenesis, identifying domain 3b of Munc18-1 as a functionally important region of the protein. Transposon insertion in an exposed loop within this domain specifically disrupted Mint1 binding despite leaving affinity for closed conformation syntaxin and binding to the SNARE complex unaffected. The insertion mutation significantly reduced total amounts of exocytosis as measured by carbon fiber amperometry in chromaffin cells. Introduction of the equivalent mutation in UNC-18 in Caenorhabditis elegans also reduced neurotransmitter release as assessed by aldicarb sensitivity. Correlation between the two experimental methods for recording changes in the number of exocytotic events was verified using a previously identified gain of function Munc18-1 mutation E466K (increased exocytosis in chromaffin cells and aldicarb hypersensitivity of C. elegans). These data implicate a novel role for an exposed loop in domain 3b of Munc18-1 in transducing regulation of vesicle fusion independent of closed-conformation syntaxin binding.
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Affiliation(s)
- Margaret E. Graham
- Department of Cellular and Molecular Physiology, The Physiological Laboratory, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Gerald R. Prescott
- Department of Cellular and Molecular Physiology, The Physiological Laboratory, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - James R. Johnson
- Department of Cellular and Molecular Physiology, The Physiological Laboratory, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Mathew Jones
- Department of Cellular and Molecular Physiology, The Physiological Laboratory, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Alice Walmesley
- Department of Cellular and Molecular Physiology, The Physiological Laboratory, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Lee P. Haynes
- Department of Cellular and Molecular Physiology, The Physiological Laboratory, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Alan Morgan
- Department of Cellular and Molecular Physiology, The Physiological Laboratory, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Robert D. Burgoyne
- Department of Cellular and Molecular Physiology, The Physiological Laboratory, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Jeff W. Barclay
- Department of Cellular and Molecular Physiology, The Physiological Laboratory, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
- * E-mail:
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Syntaxin N-terminal peptide motif is an initiation factor for the assembly of the SNARE-Sec1/Munc18 membrane fusion complex. Proc Natl Acad Sci U S A 2010; 107:22399-406. [PMID: 21139055 DOI: 10.1073/pnas.1012997108] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Intracellular membrane fusion is mediated by the concerted action of N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) and Sec1/Munc18 (SM) proteins. During fusion, SM proteins bind the N-terminal peptide (N-peptide) motif of the SNARE subunit syntaxin, but the function of this interaction is unknown. Here, using FRET-based biochemical reconstitution and Caenorhabditis elegans genetics, we show that the N-peptide of syntaxin-1 recruits the SM protein Munc18-1/nSec1 to the SNARE bundle, facilitating their assembly into a fusion-competent complex. The recruitment is achieved through physical tethering rather than allosteric activation of Munc18-1. Consistent with the recruitment role, the N-peptide is not spatially constrained along syntaxin-1, and it is functional when translocated to another SNARE subunit SNAP-25 or even when simply anchored in the target membrane. The N-peptide function is restricted to an early initiation stage of the fusion reaction. After association, Munc18-1 and the SNARE bundle together drive membrane merging without further involving the N-peptide. Thus, the syntaxin N-peptide is an initiation factor for the assembly of the SNARE-SM membrane fusion complex.
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Weber-Boyvat M, Aro N, Chernov KG, Nyman T, Jäntti J. Sec1p and Mso1p C-terminal tails cooperate with the SNAREs and Sec4p in polarized exocytosis. Mol Biol Cell 2010; 22:230-44. [PMID: 21119007 PMCID: PMC3020918 DOI: 10.1091/mbc.e10-07-0592] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
It is shown that Sec1p C-terminal tail is needed for proper Sec1p-SNARE complex interaction. Furthermore, evidence is provided that the Mso1p C terminus collaborates with the GTP-bound form of Sec4p in the bud. These results reveal a role for the Sec1p C-terminal tail in SNARE complex binding and suggest Mso1p as an effector for Sec4p. The Sec1/Munc18 protein family members perform an essential, albeit poorly understood, function in association with soluble n-ethylmaleimide sensitive factor adaptor protein receptor (SNARE) complexes in membrane fusion. The Saccharomyces cerevisiae Sec1p has a C-terminal tail that is missing in its mammalian homologues. Here we show that deletion of the Sec1p tail (amino acids 658–724) renders cells temperature sensitive for growth, reduces sporulation efficiency, causes a secretion defect, and abolishes Sec1p-SNARE component coimmunoprecipitation. The results show that the Sec1p tail binds preferentially ternary Sso1p-Sec9p-Snc2p complexes and it enhances ternary SNARE complex formation in vitro. The bimolecular fluorescence complementation (BiFC) assay results suggest that, in the SNARE-deficient sso2–1 Δsso1 cells, Mso1p, a Sec1p binding protein, helps to target Sec1p(1–657) lacking the C-terminal tail to the sites of secretion. The results suggest that the Mso1p C terminus is important for Sec1p(1–657) targeting. We show that, in addition to Sec1p, Mso1p can bind the Rab-GTPase Sec4p in vitro. The BiFC results suggest that Mso1p acts in close association with Sec4p on intracellular membranes in the bud. This association depends on the Sec4p guanine nucleotide exchange factor Sec2p. Our results reveal a novel binding mode between the Sec1p C-terminal tail and the SNARE complex, and suggest a role for Mso1p as an effector of Sec4p.
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Affiliation(s)
- Marion Weber-Boyvat
- Cell and Molecular Biology Program Research Program in Structural Biology and Biophysics, Institute of Biotechnology, FI-0001 University of Helsinki, Finland
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Functional analysis of phosphorylation on Saccharomyces cerevisiae syntaxin 1 homologues Sso1p and Sso2p. PLoS One 2010; 5:e13323. [PMID: 20948969 PMCID: PMC2952630 DOI: 10.1371/journal.pone.0013323] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2010] [Accepted: 09/09/2010] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The Saccharomyces cerevisiae syntaxin1 homologues Sso1p and Sso2p perform an essential function in membrane fusion in exocytosis. While deletion of either SSO1 or SSO2 causes no obvious phenotype in vegetatively grown cells, deletion of both genes is lethal. In sporulating diploid S. cerevisiae cells only Sso1p, but not Sso2p, is needed for membrane fusion during prospore membrane formation. Mass spectrometry and in vivo labeling data suggest that serines 23, 24, and 79 in Sso1p and serines 31 and 34 in Sso2p can be phosphorylated in vivo. Here we set out to assess the contribution of phosphorylation on Sso protein in vivo function. PRINCIPAL FINDINGS Different mutant versions of SSO1 and SSO2 were generated to target the phosphorylation sites in Sso1p and Sso2p. Basal or overexpression of phospho-mimicking or putative non-phosphorylated Sso1p or Sso2p mutants resulted in no obvious growth phenotype. However, S79A and S79E mutations caused a mild defect in the ability of Sso1p to complement the temperature-sensitive growth phenotype of sso2-1 sso1Δ cells. Combination of all mutations did not additionally compromise Sso1p in vivo function. When compared to the wild type SSO1 and SSO2, the phosphoamino acid mutants displayed similar genetic interactions with late acting sec mutants. Furthermore, diploid cells expressing only the mutant versions of Sso1p had no detectable sporulation defects. In addition to sporulation, also pseudohyphal and invasive growth modes are regulated by the availability of nutrients. In contrast to sporulating diploid cells, deletion of SSO1 or SSO2, or expression of the phospho-mutant versions of SSO1 or SSO2 as the sole copies of SSO genes caused no defects in haploid or diploid pseudohyphal and invasive growth. CONCLUSIONS The identified phosphorylation sites do not significantly contribute to the in vivo functionality of Sso1p and Sso2p in S. cerevisiae.
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