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Dewhurst-Maridor G, Abegg D, David FPA, Rougemont J, Scott CC, Adibekian A, Riezman H. The SAGA complex, together with transcription factors and the endocytic protein Rvs167p, coordinates the reprofiling of gene expression in response to changes in sterol composition in Saccharomyces cerevisiae. Mol Biol Cell 2017; 28:2637-2649. [PMID: 28768829 PMCID: PMC5620372 DOI: 10.1091/mbc.e17-03-0169] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Revised: 07/21/2017] [Accepted: 07/28/2017] [Indexed: 01/26/2023] Open
Abstract
The SAGA complex, together with transcription factors and Rvs167p, coordinates sterol-dependent transcription changes. In ergosterol mutants the SAGA complex increases its occupancy on ergosterol biosynthesis and anaerobic gene promoters, recruits the SWI/SNF complex, and binds to transcription factors and Rvs167p. Genes encoding stress proteins and basic amino acid synthesis are also affected even though promoter occupancy is not changed. Changes in cellular sterol species and concentrations can have profound effects on the transcriptional profile. In yeast, mutants defective in sterol biosynthesis show a wide range of changes in transcription, including a coinduction of anaerobic genes and ergosterol biosynthesis genes, biosynthesis of basic amino acids, and several stress genes. However the mechanisms underlying these changes are unknown. We identified mutations in the SAGA complex, a coactivator of transcription, which abrogate the ability to carry out most of these sterol-dependent transcriptional changes. In the erg3 mutant, the SAGA complex increases its occupancy time on many of the induced ergosterol and anaerobic gene promoters, increases its association with several relevant transcription factors and the SWI/SNF chromatin remodeling complex, and surprisingly, associates with an endocytic protein, Rvs167p, suggesting a moonlighting function for this protein in the sterol-regulated induction of the heat shock protein, HSP42 and HSP102, mRNAs.
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Affiliation(s)
| | - Daniel Abegg
- Department of Organic Chemistry, University of Geneva, 1205 Geneva, Switzerland.,NCCR Chemical Biology, University of Geneva, 1205 Geneva, Switzerland
| | - Fabrice P A David
- Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Jacques Rougemont
- Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Cameron C Scott
- Department of Biochemistry, University of Geneva, 1205 Geneva, Switzerland.,Department of Biochemistry, University of Geneva, 1205 Geneva, Switzerland
| | - Alexander Adibekian
- Department of Organic Chemistry, University of Geneva, 1205 Geneva, Switzerland.,NCCR Chemical Biology, University of Geneva, 1205 Geneva, Switzerland
| | - Howard Riezman
- Department of Biochemistry, University of Geneva, 1205 Geneva, Switzerland .,NCCR Chemical Biology, University of Geneva, 1205 Geneva, Switzerland
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2
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Tenay B, Kimberlin E, Williams M, Denise J, Fakilahyel J, Kim K. Inactivation of Tor proteins affects the dynamics of endocytic proteins in early stage of endocytosis. J Biosci 2013; 38:351-61. [PMID: 23660670 DOI: 10.1007/s12038-013-9326-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Tor2 is an activator of the Rom2/Rho1 pathway that regulates alpha-factor internalization. Since the recruitment of endocytic proteins such as actin-binding proteins and the amphiphysins precedes the internalization of alpha-factor, we hypothesized that loss of Tor function leads to an alteration in the dynamics of the endocytic proteins. We report here that endocytic proteins, Abp1 and Rvs167, are less recruited to endocytic sites not only in tor2 but also tor1 mutants. Furthermore, we found that the endocytic proteins Rvs167 and Sjl2 are completely mistargeted to the cytoplasm in tor1 delta tor2ts double mutant cells. We also demonstrate here that the efficiency of endocytic internalization or scission in all tor mutants was drastically decreased. In agreement with the Sjl2 mislocalization, we found that in tor1 delta tor2ts double mutant cells, as well as other tor mutant cells, the overall PIP2 level was dramatically increased. Finally, the cell wall chitin content in tor2ts and tor1 delta tor2ts mutant cells was also significantly increased. Taken together, both functional Tor proteins, Tor1 and Tor2, are essentially required for proper endocytic protein dynamics at the early stage of endocytosis.
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Affiliation(s)
- Brandon Tenay
- Department of Biology, Missouri State University, 901 South National Ave, Springfield, MO 65897, USA
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3
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Identification of a novel chitin-binding spore wall protein (NbSWP12) with a BAR-2 domain from Nosema bombycis (microsporidia). Parasitology 2013; 140:1394-402. [PMID: 23920053 DOI: 10.1017/s0031182013000875] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The spore wall of Nosema bombycis plays an important role in microsporidian pathogenesis. Protein fractions from germinated spore coats were analysed by two-dimensional polyacrylamide gel electrophoresis and MALDI-TOF/TOF mass spectrometry. Three protein spots were identified as the hypothetical spore wall protein NbHSWP12. A BAR-2 domain (e-value: 1.35e-03) was identified in the protein, and an N-terminal protein-heparin interaction motif, a potential N-glycosylation site, and 16 phosphorylation sites primarily activated by protein kinase C were also predicted. The sequence analysis suggested that Nbhswp12 and its homologous genes are widely distributed among microsporidia. Additionally, Nbhswp12 gene homologues share similar sequence features. An indirect immunofluorescence analysis showed that NbHSWP12 localized to the spore wall, and thus we renamed it spore wall protein 12 (NbSWP12). Moreover, NbSWP12 could adhere to deproteinized N. bombycis chitin coats that were obtained by hot alkaline treatment. This novel N. bombycis spore wall protein may function in a structural capacity to facilitate microsporidial spore maintenance.
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Upadhyay RD, Kumar AV, Sonawane S, Gaonkar R, Balasinor NH. Estrogen Effects on Actin Cytoskeletal and Endocytic Proteins Associated With Tubulobulbar Complex Disruption in Rat Testes. Reprod Sci 2013; 20:1162-74. [DOI: 10.1177/1933719113477491] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Rahul D. Upadhyay
- Department of Neuroendocrinology, National Institute for Research in Reproductive Health, Mumbai, India
| | - Anita V. Kumar
- Department of Neuroendocrinology, National Institute for Research in Reproductive Health, Mumbai, India
| | - Shobha Sonawane
- Department of Neuroendocrinology, National Institute for Research in Reproductive Health, Mumbai, India
| | - Reshma Gaonkar
- Department of Neuroendocrinology, National Institute for Research in Reproductive Health, Mumbai, India
| | - Nafisa H. Balasinor
- Department of Neuroendocrinology, National Institute for Research in Reproductive Health, Mumbai, India
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5
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Berepiki A, Lichius A, Read ND. Actin organization and dynamics in filamentous fungi. Nat Rev Microbiol 2011; 9:876-87. [PMID: 22048737 DOI: 10.1038/nrmicro2666] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Growth and morphogenesis of filamentous fungi is underpinned by dynamic reorganization and polarization of the actin cytoskeleton. Actin has crucial roles in exocytosis, endocytosis, organelle movement and cytokinesis in fungi, and these processes are coupled to the production of distinct higher-order structures (actin patches, cables and rings) that generate forces or serve as tracks for intracellular transport. New approaches for imaging actin in living cells are revealing important similarities and differences in actin architecture and organization within the fungal kingdom, and have yielded key insights into cell polarity, tip growth and long-distance intracellular transport. In this Review, we discuss the contribution that recent live-cell imaging and mutational studies have made to our understanding of the dynamics and regulation of actin in filamentous fungi.
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Affiliation(s)
- Adokiye Berepiki
- Fungal Cell Biology Group, Institute of Cell Biology, Rutherford Building, University of Edinburgh, Edinburgh, UK
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6
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Fricke R, Gohl C, Bogdan S. The F-BAR protein family Actin' on the membrane. Commun Integr Biol 2011; 3:89-94. [PMID: 20585497 DOI: 10.4161/cib.3.2.10521] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2009] [Accepted: 11/03/2009] [Indexed: 11/19/2022] Open
Abstract
A tight spatio-temporal coordination of the machineries controlling actin dynamics and membrane remodelling is crucial for a huge variety of cellular processes that shape cells into a multicellular organism. Dynamic membrane remodelling is achieved by a functional relationship between proteins that control plasma membrane curvature, membrane fission and nucleation of new actin filaments. The BAR/F-BAR-domain-containing proteins are prime candidates to couple plasma membrane curvature and actin dynamics in different morphogenetic processes. Here, we discuss recent findings on the membrane-shaping proteins of the F-BAR domain subfamily and how they regulate morphogenetic processes in vivo.
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Affiliation(s)
- Robert Fricke
- Institut für Neurobiologie; Wilhelms-University; Münster; Münster, Germany
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7
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Quiñones GA, Oro AE. BAR domain competition during directional cellular migration. Cell Cycle 2011; 9:2522-8. [PMID: 20581461 DOI: 10.4161/cc.9.13.12123] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
While directed cellular migration facilitates the coordinated movement of cells during development and tissue repair, the precise mechanisms regulating the interplay between the extracellular environment, the actin cytoskeleton, and the overlying plasma membrane remain inadequately understood. The BAR domain family of lipid binding, actin cytoskeletal regulators are gaining greater appreciation for their role in these critical processes. BAR domain proteins are involved as both positive and negative regulators of endocytosis, membrane plasticity, and directional cell migration. This review focuses on the functional relationship between different classes of BAR domain proteins and their role in guiding cell migration through regulation of the endocytic machinery. Competition for key signaling substrates by positive and negative BAR domain endocytic regulators appears to mediate control of directional cell migration, and may have wider applicability to other trafficking functions associated with development and carcinogenesis.
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Affiliation(s)
- Gabriel A Quiñones
- Program in Epithelial Biology and Cancer Biology Graduate Program, Stanford University School of Medicine, Stanford, CA, USA
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8
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Youn JY, Friesen H, Kishimoto T, Henne WM, Kurat CF, Ye W, Ceccarelli DF, Sicheri F, Kohlwein SD, McMahon HT, Andrews BJ. Dissecting BAR domain function in the yeast Amphiphysins Rvs161 and Rvs167 during endocytosis. Mol Biol Cell 2010; 21:3054-69. [PMID: 20610658 PMCID: PMC2929998 DOI: 10.1091/mbc.e10-03-0181] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2010] [Revised: 06/25/2010] [Accepted: 06/29/2010] [Indexed: 02/05/2023] Open
Abstract
BAR domains are protein modules that bind to membranes and promote membrane curvature. One type of BAR domain, the N-BAR domain, contains an additional N-terminal amphipathic helix, which contributes to membrane-binding and bending activities. The only known N-BAR-domain proteins in the budding yeast Saccharomyces cerevisiae, Rvs161 and Rvs167, are required for endocytosis. We have explored the mechanism of N-BAR-domain function in the endocytosis process using a combined biochemical and genetic approach. We show that the purified Rvs161-Rvs167 complex binds to liposomes in a curvature-independent manner and promotes tubule formation in vitro. Consistent with the known role of BAR domain polymerization in membrane bending, we found that Rvs167 BAR domains interact with each other at cortical actin patches in vivo. To characterize N-BAR-domain function in endocytosis, we constructed yeast strains harboring changes in conserved residues in the Rvs161 and Rvs167 N-BAR domains. In vivo analysis of the rvs endocytosis mutants suggests that Rvs proteins are initially recruited to sites of endocytosis through their membrane-binding ability. We show that inappropriate regulation of complex sphingolipid and phosphoinositide levels in the membrane can impinge on Rvs function, highlighting the relationship between membrane components and N-BAR-domain proteins in vivo.
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Affiliation(s)
- Ji-Young Youn
- Department of Molecular Genetics, Banting and Best Department of Medical Research, Terrence Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, ON M5S3E1, Canada
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9
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Kaake RM, Milenković T, Przulj N, Kaiser P, Huang L. Characterization of cell cycle specific protein interaction networks of the yeast 26S proteasome complex by the QTAX strategy. J Proteome Res 2010; 9:2016-29. [PMID: 20170199 DOI: 10.1021/pr1000175] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Ubiquitin-proteasome dependent protein degradation plays a fundamental role in the regulation of the eukaryotic cell cycle. Cell cycle transitions between different phases are tightly regulated to prevent uncontrolled cell proliferation, which is characteristic of cancer cells. To understand cell cycle phase specific regulation of the 26S proteasome and reveal the molecular mechanisms underlying the ubiquitin-proteasome degradation pathway during cell cycle progression, we have carried out comprehensive characterization of cell cycle phase specific proteasome interacting proteins (PIPs) by QTAX analysis of synchronized yeast cells. Our efforts have generated specific proteasome interaction networks for the G1, S, and M phases of the cell cycle and identified a total of 677 PIPs, 266 of which were not previously identified from unsynchronized cells. On the basis of the dynamic changes of their SILAC ratios across the three cell cycle phases, we have employed a profile vector-based clustering approach and identified 20 functionally significant groups of PIPs, 3 of which are enriched with cell cycle related functions. This work presents the first step toward understanding how dynamic proteasome interactions are involved in various cellular pathways during the cell cycle.
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Affiliation(s)
- Robyn M Kaake
- Departments of Physiology & Biophysics and Developmental & Cell Biology, University of California, Irvine, California 92697-4560, USA
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10
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Reijnst P, Walther A, Wendland J. Functional analysis of Candida albicans genes encoding SH3-domain-containing proteins. FEMS Yeast Res 2010; 10:452-61. [DOI: 10.1111/j.1567-1364.2010.00624.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
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12
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Hess DC, Myers CL, Huttenhower C, Hibbs MA, Hayes AP, Paw J, Clore JJ, Mendoza RM, Luis BS, Nislow C, Giaever G, Costanzo M, Troyanskaya OG, Caudy AA. Computationally driven, quantitative experiments discover genes required for mitochondrial biogenesis. PLoS Genet 2009; 5:e1000407. [PMID: 19300474 PMCID: PMC2648979 DOI: 10.1371/journal.pgen.1000407] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2008] [Accepted: 02/05/2009] [Indexed: 01/09/2023] Open
Abstract
Mitochondria are central to many cellular processes including respiration, ion homeostasis, and apoptosis. Using computational predictions combined with traditional quantitative experiments, we have identified 100 proteins whose deficiency alters mitochondrial biogenesis and inheritance in Saccharomyces cerevisiae. In addition, we used computational predictions to perform targeted double-mutant analysis detecting another nine genes with synthetic defects in mitochondrial biogenesis. This represents an increase of about 25% over previously known participants. Nearly half of these newly characterized proteins are conserved in mammals, including several orthologs known to be involved in human disease. Mutations in many of these genes demonstrate statistically significant mitochondrial transmission phenotypes more subtle than could be detected by traditional genetic screens or high-throughput techniques, and 47 have not been previously localized to mitochondria. We further characterized a subset of these genes using growth profiling and dual immunofluorescence, which identified genes specifically required for aerobic respiration and an uncharacterized cytoplasmic protein required for normal mitochondrial motility. Our results demonstrate that by leveraging computational analysis to direct quantitative experimental assays, we have characterized mutants with subtle mitochondrial defects whose phenotypes were undetected by high-throughput methods. Mitochondria are the proverbial powerhouses of the cell, running the fundamental biochemical processes that produce energy from nutrients using oxygen. These processes are conserved in all eukaryotes, from humans to model organisms such as baker's yeast. In humans, mitochondrial dysfunction plays a role in a variety of diseases, including diabetes, neuromuscular disorders, and aging. In order to better understand fundamental mitochondrial biology, we studied genes involved in mitochondrial biogenesis in the yeast S. cerevisiae, discovering over 100 proteins with novel roles in this process. These experiments assigned function to 5% of the genes whose function was not known. In order to achieve this rapid rate of discovery, we developed a system incorporating highly quantitative experimental assays and an integrated, iterative process of computational protein function prediction. Beginning from relatively little prior knowledge, we found that computational predictions achieved about 60% accuracy and rapidly guided our laboratory work towards hundreds of promising candidate genes. Thus, in addition to providing a more thorough understanding of mitochondrial biology, this study establishes a framework for successfully integrating computation and experimentation to drive biological discovery. A companion manuscript, published in PLoS Computational Biology (doi:10.1371/journal.pcbi.1000322), discusses observations and conclusions important for the computational community.
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Affiliation(s)
- David C. Hess
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
| | - Chad L. Myers
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
- Department of Computer Science, Princeton University, Princeton, New Jersey, United States of America
- Department of Computer Science and Engineering, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Curtis Huttenhower
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
- Department of Computer Science, Princeton University, Princeton, New Jersey, United States of America
| | - Matthew A. Hibbs
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
- Department of Computer Science, Princeton University, Princeton, New Jersey, United States of America
| | - Alicia P. Hayes
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
| | - Jadine Paw
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Ontario, Canada
| | - John J. Clore
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
| | - Rosa M. Mendoza
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
| | - Bryan San Luis
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Ontario, Canada
| | - Corey Nislow
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Ontario, Canada
| | - Guri Giaever
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Ontario, Canada
| | - Michael Costanzo
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Ontario, Canada
| | - Olga G. Troyanskaya
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
- Department of Computer Science, Princeton University, Princeton, New Jersey, United States of America
- * E-mail: (OGT); (AAC)
| | - Amy A. Caudy
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
- * E-mail: (OGT); (AAC)
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Prendergast GC, Muller AJ, Ramalingam A, Chang MY. BAR the door: cancer suppression by amphiphysin-like genes. Biochim Biophys Acta Rev Cancer 2008; 1795:25-36. [PMID: 18930786 DOI: 10.1016/j.bbcan.2008.09.001] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2008] [Revised: 08/26/2008] [Accepted: 09/03/2008] [Indexed: 11/17/2022]
Abstract
The evolutionarily conserved amphiphysin-like genes Bin1 and Bin3 function in membrane and actin dynamics, cell polarity, and stress signaling. Recent genetic studies in mice discriminate non-essential roles in endocytic processes commonly ascribed to amphiphysins from essential roles in cancer suppression. Bin1 acts in default pathways of apoptosis and senescence that are triggered by the Myc and Raf oncogenes in primary cells, and Bin1 gene products display a 'moonlighting function' in the nucleus where a variety of other 'endocytic' proteins are also found. Together, genetic investigations in yeast, flies, and mice suggest that amphiphysin-like adapter proteins may suppress cancer by helping integrate cell polarity signals generated by actin and vesicle dynamics with central regulators of cell cycle arrest, apoptosis, and immune surveillance.
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Upadhyay S, Shaw BD. The role of actin, fimbrin and endocytosis in growth of hyphae in Aspergillus nidulans. Mol Microbiol 2008; 68:690-705. [PMID: 18331474 DOI: 10.1111/j.1365-2958.2008.06178.x] [Citation(s) in RCA: 141] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Filamentous fungi are ideal systems to study the process of polarized growth, as their life cycle is dominated by hyphal growth exclusively at the cell apex. The actin cytoskeleton plays an important role in this growth. Until now, there have been no tools to visualize actin or the actin-binding protein fimbrin in live cells of a filamentous fungus. We investigated the roles of actin (ActA) and fimbrin (FimA) in hyphal growth in Aspergillus nidulans. We examined the localization of ActA::GFP and FimA::GFP in live cells, and each displayed a similar localization pattern. In actively growing hyphae, cortical ActA::GFP and FimA::GFP patches were highly mobile throughout the hypha and were concentrated near hyphal apices. A patch-depleted zone occupied the apical 0.5 microm of growing hypha. Both FimA::GFP and Act::GFP also localize transiently to septa. Movement and later localization of both was compromised after cytochalasin treatment. Disruption of fimA resulted in delayed polarity establishment during conidium germination, abnormal hyphal growth and endocytosis defects in apolar cells. Endocytosis was severely impaired in apolar fimA disruption cells. Our data support a novel apical recycling model which indicates a critical role for actin patch-mediated endocytosis to maintain polarized growth at the apex.
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Affiliation(s)
- Srijana Upadhyay
- Program for the Biology of Filamentous Fungi, Department of Plant Pathology and Microbiology, Texas A&M University, 2132 TAMU, College Station, TX 77843, USA
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Araujo-Bazán L, Peñalva MA, Espeso EA. Preferential localization of the endocytic internalization machinery to hyphal tips underlies polarization of the actin cytoskeleton in Aspergillus nidulans. Mol Microbiol 2008; 67:891-905. [DOI: 10.1111/j.1365-2958.2007.06102.x] [Citation(s) in RCA: 134] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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16
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Yaguchi SI, Shen H, Tsurugi K. Localization of Gts1p in cortical actin patches of yeast and its possible role in endocytosis. Eur J Cell Biol 2007; 86:275-85. [PMID: 17449140 DOI: 10.1016/j.ejcb.2007.02.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2006] [Revised: 02/09/2007] [Accepted: 02/09/2007] [Indexed: 01/24/2023] Open
Abstract
Herein we report that Gts1p fused with green-fluorescent protein (GFP) is localized in the cortical actin patch besides nuclei in yeast and the cortical Gts1p changed its position together with the patch depending on the cell-cycle phase, while nuclear Gts1p accumulated predominantly in the budding phase. Whereas Gts1p does not directly bind to actin, it associated mainly with the actin-associated protein Pan1p. In the GTS1-deleted transformant gts1Delta, the number of cells containing either a fragmented vacuole or an enlarged single central vacuole increased and the uptake of the hydrophilic dye Lucifer yellow (LY) in the vacuole decreased. Further, gts1Delta transformed with a mutant Gts1p having two cysteine-to-alanine substitutions in a zinc finger resembling that of GTPase-activating proteins of ADP-ribosylation factors (ARF-GAP) neither recovered the LY uptake unlike gts1Delta transformed with the wild-type GTS1, nor reduced the average size of central vacuoles as much as the latter did. These results suggested that Gts1p in the actin patch is involved in the fluid-phase endocytosis and membrane trafficking for vacuole formation and that the putative ARF-GAP domain in Gts1p plays an important role in these functions.
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Affiliation(s)
- So-ichi Yaguchi
- Department of Biochemistry 2, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi 409-3898, Japan
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17
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Oberholzer U, Nantel A, Berman J, Whiteway M. Transcript profiles of Candida albicans cortical actin patch mutants reflect their cellular defects: contribution of the Hog1p and Mkc1p signaling pathways. EUKARYOTIC CELL 2007; 5:1252-65. [PMID: 16896210 PMCID: PMC1539150 DOI: 10.1128/ec.00385-05] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In Candida albicans, Myo5p and Sla2p are required for the polarized localization and function of cortical actin patches, for hyphal formation, and for endocytosis. Deletion of either the MYO5 or the SLA2 gene generated a common transcriptional response that involved changes in the transcript levels of cell wall protein- and membrane protein-encoding genes. However, these profiles were distinct from those observed for a mutant with specific deletions of the actin-organizing domains of Myo5p or for wild-type cells treated with cytochalasin A, both of which also generate defects in the organization of cortical actin patches. The profiles observed for the myo5Delta and sla2Delta mutants had similarities to those of wild-type cells subjected to an osmotic shock, and the defects in cortical patch function found with myo5Delta and sla2Delta mutants, but not cortical actin patch distribution per se, affected sensitivity to various stresses, including heat and osmotic shocks and cell wall damage. Secondary effects coupled with defective endocytosis, such as lack of polarized lipid rafts and associated protein Rvs167-GFP (where GFP is green fluorescent protein) and lack of polarized wall remodeling protein GFP-Gsc1, were also observed for the myo5Delta and sla2Delta mutants. The mitogen-activated protein kinases Hog1p and Mkc1p, which mediate signaling in response to osmotic stress and cell wall damage, do not play a major role in regulating the transcript level changes in the myo5Delta and sla2Delta mutants. Hog1p was not hyperphosphorylated in the myo5Delta and sla2Delta mutants, and the transcript levels of only a subset of genes affected in the myo5Delta mutant were dependent upon the presence of Hog1p and Mkc1p. However, it appears that Hog1p and Mkc1p play important roles in the myo5Delta mutant cells because double deletion of myosin I and either Hog1p or Mkc1p resulted in very-slow-growing cells.
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Affiliation(s)
- Ursula Oberholzer
- Biotechnology Research Institute, National Research Council of Canada, 6100 Royalmount, Montreal H4P 2R2, Quebec, Canada
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Kusumi N, Watanabe M, Yamada H, Li SA, Kashiwakura Y, Matsukawa T, Nagai A, Nasu Y, Kumon H, Takei K. Implication of Amphiphysin 1 and Dynamin 2 in Tubulobulbar Complex Formation and Spermatid Release. Cell Struct Funct 2007; 32:101-13. [PMID: 17785912 DOI: 10.1247/csf.07024] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Tubulobulbar complexes (TBCs) are composed of several tubular invaginations formed at the plasma membrane of testicular Sertoli cells. TBCs are transiently formed at the contact region with spermatids at spermatogenic stage VII in rat and mouse, and such TBC formation is prerequisite for spermatid release. Since the characteristic structure of TBCs suggests that the molecules implicated in endocytosis could be involved in TBC formation, we here investigated the localization and physiological roles of endocytic proteins, amphiphysin 1 and dynamin 2, at TBCs. We demonstrated by immunofluorescence that the endocytic proteins were concentrated at TBCs, where they colocalized with cytoskeletal proteins, such as actin and vinculin. Immunoelectron microscopy disclosed that both amphiphysin 1 and dynamin 2 were localized on TBC membrane. Next, we histologically examined the testis from amphiphysin 1 deficient {Amph(-/-)} mice. Morphometric analysis revealed that the number of TBCs was significantly reduced in Amph(-/-). The ratio of stage VIII seminiferous tubules was increased, and the ratio of stage IX was conversely decreased in Amph(-/-). Moreover, unreleased spermatids in stage VIII seminiferous tubules were increased in Amph(-/-), indicating that spermatid release and the following transition from stage VIII to IX was prolonged in Amph(-/-) mice. These results suggest that amphiphysin 1 and dynamin 2 are involved in TBC formation and spermatid release at Sertoli cells.
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Affiliation(s)
- Norihiro Kusumi
- Department of Urology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan
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19
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Ren G, Vajjhala P, Lee JS, Winsor B, Munn AL. The BAR domain proteins: molding membranes in fission, fusion, and phagy. Microbiol Mol Biol Rev 2006; 70:37-120. [PMID: 16524918 PMCID: PMC1393252 DOI: 10.1128/mmbr.70.1.37-120.2006] [Citation(s) in RCA: 147] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The Bin1/amphiphysin/Rvs167 (BAR) domain proteins are a ubiquitous protein family. Genes encoding members of this family have not yet been found in the genomes of prokaryotes, but within eukaryotes, BAR domain proteins are found universally from unicellular eukaryotes such as yeast through to plants, insects, and vertebrates. BAR domain proteins share an N-terminal BAR domain with a high propensity to adopt alpha-helical structure and engage in coiled-coil interactions with other proteins. BAR domain proteins are implicated in processes as fundamental and diverse as fission of synaptic vesicles, cell polarity, endocytosis, regulation of the actin cytoskeleton, transcriptional repression, cell-cell fusion, signal transduction, apoptosis, secretory vesicle fusion, excitation-contraction coupling, learning and memory, tissue differentiation, ion flux across membranes, and tumor suppression. What has been lacking is a molecular understanding of the role of the BAR domain protein in each process. The three-dimensional structure of the BAR domain has now been determined and valuable insight has been gained in understanding the interactions of BAR domains with membranes. The cellular roles of BAR domain proteins, characterized over the past decade in cells as distinct as yeasts, neurons, and myocytes, can now be understood in terms of a fundamental molecular function of all BAR domain proteins: to sense membrane curvature, to bind GTPases, and to mold a diversity of cellular membranes.
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Affiliation(s)
- Gang Ren
- Institute for Molecular Bioscience, University of Queensland, St. Lucia, Queensland 4072, Australia
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20
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Friesen H, Humphries C, Ho Y, Schub O, Colwill K, Andrews B. Characterization of the yeast amphiphysins Rvs161p and Rvs167p reveals roles for the Rvs heterodimer in vivo. Mol Biol Cell 2006; 17:1306-21. [PMID: 16394103 PMCID: PMC1382319 DOI: 10.1091/mbc.e05-06-0476] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2005] [Revised: 12/13/2005] [Accepted: 12/27/2005] [Indexed: 11/11/2022] Open
Abstract
We have used comprehensive synthetic lethal screens and biochemical assays to examine the biological role of the yeast amphiphysin homologues Rvs161p and Rvs167p, two proteins that play a role in regulation of the actin cytoskeleton, endocytosis, and sporulation. We found that unlike some forms of amphiphysin, Rvs161p-Rvs167p acts as an obligate heterodimer during vegetative growth and neither Rvs161p nor Rvs167p forms a homodimer in vivo. RVS161 and RVS167 have an identical set of 49 synthetic lethal interactions, revealing functions for the Rvs proteins in cell polarity, cell wall synthesis, and vesicle trafficking as well as a shared role in mating. Consistent with these roles, we show that the Rvs167p-Rvs161p heterodimer, like its amphiphysin homologues, can bind to phospholipid membranes in vitro, suggesting a role in vesicle formation and/or fusion. Our genetic screens also reveal that the interaction between Abp1p and the Rvs167p Src homology 3 (SH3) domain may be important under certain conditions, providing the first genetic evidence for a role for the SH3 domain of Rvs167p. Our studies implicate heterodimerization of amphiphysin family proteins in various functions related to cell polarity, cell integrity, and vesicle trafficking during vegetative growth and the mating response.
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Affiliation(s)
- Helena Friesen
- Department of Medical Genetics and Microbiology, Banting and Best Department of Medical Research, University of Toronto, Toronto, Ontario, Canada M5S 1A8
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21
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Abstract
The actin-nucleating Arp2/3 complex is essential for life in yeast and animals, but not in plants, in which mutants of Arp2/3 complex components show relatively minor developmental abnormalities. Animal cells control the activity of the Arp2/3 complex through the suppressor of cyclic AMP receptor (SCAR) complex to achieve cell motility. Amazingly, plants have also retained the SCAR cell-motility pathway, and now provide a unique model for the study of new aspects of SCAR function in the absence of cell motility.
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Affiliation(s)
- Michael J Deeks
- The Integrative Cell Biology Laboratory, School of Biological and Biomedical Sciences, University of Durham, South Road, Durham, DH1 3LE, UK
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22
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Kaksonen M, Toret CP, Drubin DG. A modular design for the clathrin- and actin-mediated endocytosis machinery. Cell 2005; 123:305-20. [PMID: 16239147 DOI: 10.1016/j.cell.2005.09.024] [Citation(s) in RCA: 583] [Impact Index Per Article: 30.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2005] [Revised: 08/08/2005] [Accepted: 09/20/2005] [Indexed: 11/24/2022]
Abstract
Endocytosis depends on an extensive network of interacting proteins that execute a series of distinct subprocesses. Previously, we used live-cell imaging of six budding-yeast proteins to define a pathway for association of receptors, adaptors, and actin during endocytic internalization. Here, we analyzed the effects of 61 deletion mutants on the dynamics of this pathway, revealing functions for 15 proteins, and we analyzed the dynamics of 8 of these proteins. Our studies provide evidence for four protein modules that cooperate to drive coat formation, membrane invagination, actin-meshwork assembly, and vesicle scission during clathrin/actin-mediated endocytosis. We found that clathrin facilitates the initiation of endocytic-site assembly but is not needed for membrane invagination or vesicle formation. Finally, we present evidence that the actin-meshwork assembly that drives membrane invagination is nucleated proximally to the plasma membrane, opposite to the orientation observed for previously studied actin-assembly-driven motility processes.
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Affiliation(s)
- Marko Kaksonen
- Department of Molecular and Cell Biology, University of California, Berkeley, 94720, USA
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23
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Talarek N, Balguerie A, Aigle M, Durrens P. A novel link between a rab GTPase and Rvs proteins: the yeast amphiphysin homologues. Cell Biochem Funct 2005; 23:253-66. [PMID: 15473003 DOI: 10.1002/cbf.1146] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The BAR proteins are a well-conserved family of proteins including Rvsp in yeast, amphiphysins and Bin proteins in mammals. In yeast, as in mammals, BAR proteins are known to be implicated in vesicular traffic. The Gyp5p (Ypl249p) and Ymr192p proteins interact in two-hybrid tests with both Rvs161p and Rvs167p. Gyp5p is a Ypt/Rab-specific GAP and Ymr192p is highly similar to Gyp5p. To specify the interaction between Rvsp and Gyp5p, we used two-hybrid tests to determine the domains necessary for these interactions. The specific SH3 domain of Rvs167p interacted with the N-terminal domain of Gyp5p. Moreover, Gyp5p could form a homodimer. Fus2 protein is a specific partner of Rvs161p in two-hybrid tests. To characterize the functional relationships between these five proteins, we have studied cellular phenotypes in single, double and triple mutant strains for which rvs mutants present defects, such as polarity, cell fusion and meiosis. Phenotypic analysis showed that Gyp5p, Ymr192p and Fus2p were involved in bipolar budding pattern and in meiosis. Specific epistasis or suppressive phenomena were found between the five mutations. Finally, The Gyp5p-GFP fusion protein was localized at the bud tip during apical growth and at the mother-bud neck during cytokinesis. Moreover, Rvs167p and Rvs161p were shown to be essential for the correct localization of Gyp5p. Altogether, these data support the hypothesis that both Rvsp proteins act in vesicular traffic through physical and functional interactions with Ypt/Rab regulators.
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Huang TY, Renaud-Young M, Young D. Nak1 interacts with Hob1 and Wsp1 to regulate cell growth and polarity in Schizosaccharomyces pombe. J Cell Sci 2005; 118:199-210. [PMID: 15615784 DOI: 10.1242/jcs.01608] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have previously reported that Nak1, a group-II germinal center (GC) kinase, is essential for polarized growth in Schizosaccharomyces pombe. Here, we provide evidence that Nak1 regulates cell growth and polarity, in part, through its interactions with Hob1 (an Rvs167/amphiphysin homolog) and Wsp1 (Wiskott-Aldrich-syndrome-protein homolog). We found that Nak1, Hob1 and Wsp1 interact physically, and that both Hob1/green-fluorescent-protein (Hob1-GFP) and Wsp1-GFP fusion proteins localized to F-actin patches at growing cell ends and medial division sites. Hob1-GFP was dissociated from patches in cells lacking Wsp1. Also, Hob1 overexpression dissociated Wsp1-GFP from foci, inhibited Wsp1-directed F-actin formation in vitro and partially restored polarity defects associated with Wsp1 overexpression or nak1 repression. Furthermore, loss of both Wsp1 and Hob1 resulted in rounded cells, slow growth and multiple septae. Together, these observations suggest that Hob1 and Wsp1 cooperate to mediate cell polarity, growth and division. Repression of nak1 resulted in a random redistribution of Hob1-GFP and Wsp1-GFP foci, and inhibition of Wsp1-directed F-actin formation in vitro. Furthermore, hob1delta and wsp1delta mutants exhibited synthetic growth defects in combination with nak1 repression, suggesting that Nak1 has redundant functions with Hob1 and Wsp1. Collectively, our results suggest that Nak1 both regulates and cooperates with Hob1 and Wsp1 to promote F-actin formation and polarized cell growth.
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Affiliation(s)
- Timothy Y Huang
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, AB T2N 4N1, Canada
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25
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Friesen H, Colwill K, Robertson K, Schub O, Andrews B. Interaction of the Saccharomyces cerevisiae cortical actin patch protein Rvs167p with proteins involved in ER to Golgi vesicle trafficking. Genetics 2005; 170:555-68. [PMID: 15802519 PMCID: PMC1450407 DOI: 10.1534/genetics.104.040063] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We have used affinity chromatography to identify two proteins that bind to the SH3 domain of the actin cytoskeleton protein Rvs167p: Gyp5p and Gyl1p. Gyp5p has been shown to be a GTPase activating protein (GAP) for Ypt1p, a Rab GTPase involved in ER to Golgi trafficking; Gyl1p is a protein that resembles Gyp5p and has recently been shown to colocalize with and belong to the same protein complex as Gyp5p. We show that Gyl1p and Gyp5p interact directly with each other, likely through their carboxy-terminal coiled-coil regions. In assays of GAP activity, Gyp5p had GAP activity toward Ypt1p and we found that this activity was stimulated by the addition of Gyl1p. Gyl1p had no GAP activity toward Ypt1p. Genetic experiments suggest a role for Gyp5p and Gyl1p in ER to Golgi trafficking, consistent with their biochemical role. Since Rvs167p has a previously characterized role in endocytosis and we have shown here that it interacts with proteins involved in Golgi vesicle trafficking, we suggest that Rvs167p may have a general role in vesicle trafficking.
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Affiliation(s)
- Helena Friesen
- Department of Molecular and Medical Genetics, University of Toronto, Ontario, Canada
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26
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Germann M, Swain E, Bergman L, Nickels JT. Characterizing the sphingolipid signaling pathway that remediates defects associated with loss of the yeast amphiphysin-like orthologs, Rvs161p and Rvs167p. J Biol Chem 2004; 280:4270-8. [PMID: 15561700 DOI: 10.1074/jbc.m412454200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Loss of function of either the RVS161 or RVS167 Saccharomyces cerevisiae amphiphysin-like gene confers similar growth phenotypes that can be suppressed by mutations in sphingolipid biosynthesis. We performed a yeast two-hybrid screen using Rvs161p as bait to uncover proteins involved in this sphingolipid-dependent suppressor pathway. In the process, we have demonstrated a direct physical interaction between Rvs167p and the two-hybrid interacting proteins, Acf2p, Gdh3p, and Ybr108wp, while also elucidating the Rvs167p amino acid domains to which these proteins bind. By using subcellular fractionation, we demonstrate that Rvs167p, Ybr108wp, Gdh3p, and Acf2p all localize to Rvs161p-containing lipid rafts, thus placing them within a single compartment that should facilitate their interactions. Moreover, our results suggest that Acf2p and Gdh3p functions are needed for suppressor pathway activity. To determine pathway mechanisms further, we examined the localization of Rvs167p in suppressor mutants. These studies reveal roles for Rvs161p and the very long chain fatty acid elongase, Sur4p, in the localization and/or stability of Rvs167p. Previous yeast studies showed that rvs defects could be suppressed by changes in sphingolipid metabolism brought about by deleting SUR4 (Desfarges, L., Durrens, P., Juguelin, H., Cassagne, C., Bonneu, M., and Aigle, M. (1993) Yeast 9, 267-277). Using rvs167 sur4 and rvs161 sur4 double null cells as models to study suppressor pathway activity, we demonstrate that loss of SUR4 does not remediate the steady-state actin cytoskeletal defects of rvs167 or rvs161 cells. Moreover, suppressor activity does not require the function of the actin-binding protein, Abp1p, or Sla1p, a protein that is thought to regulate assembly of the cortical actin cytoskeleton. Based on our results, we suggest that sphingolipid-dependent suppression of rvs defects may not work entirely through regulating changes in actin organization.
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Affiliation(s)
- Melody Germann
- Department of Biochemistry, Drexel University College of Medicine, Philadelphia, Pennsylvania 19102, USA
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27
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Ceulemans H, Bollen M. Functional diversity of protein phosphatase-1, a cellular economizer and reset button. Physiol Rev 2004; 84:1-39. [PMID: 14715909 DOI: 10.1152/physrev.00013.2003] [Citation(s) in RCA: 490] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The protein serine/threonine phosphatase protein phosphatase-1 (PP1) is a ubiquitous eukaryotic enzyme that regulates a variety of cellular processes through the dephosphorylation of dozens of substrates. This multifunctionality of PP1 relies on its association with a host of function-specific targetting and substrate-specifying proteins. In this review we discuss how PP1 affects the biochemistry and physiology of eukaryotic cells. The picture of PP1 that emerges from this analysis is that of a "green" enzyme that promotes the rational use of energy, the recycling of protein factors, and a reversal of the cell to a basal and/or energy-conserving state. Thus PP1 promotes a shift to the more energy-efficient fuels when nutrients are abundant and stimulates the storage of energy in the form of glycogen. PP1 also enables the relaxation of actomyosin fibers, the return to basal patterns of protein synthesis, and the recycling of transcription and splicing factors. In addition, PP1 plays a key role in the recovery from stress but promotes apoptosis when cells are damaged beyond repair. Furthermore, PP1 downregulates ion pumps and transporters in various tissues and ion channels that are involved in the excitation of neurons. Finally, PP1 promotes the exit from mitosis and maintains cells in the G1 or G2 phases of the cell cycle.
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Affiliation(s)
- Hugo Ceulemans
- Afdeling Biochemie, Faculteit Geneeskunde, Katholieke Universiteit Leuven, Leuven, Belgium
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28
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Sarret P, Esdaile MJ, McPherson PS, Schonbrunn A, Kreienkamp HJ, Beaudet A. Role of Amphiphysin II in Somatostatin Receptor Trafficking in Neuroendocrine Cells. J Biol Chem 2004; 279:8029-37. [PMID: 14660576 DOI: 10.1074/jbc.m310792200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Amphiphysins are SH3 domain-containing proteins thought to function in clathrin-mediated endocytosis. To investigate the potential role of amphiphysin II in cellular trafficking of G protein-coupled somatostatin (SRIF) receptors, we generated an AtT-20 cell line stably overexpressing amphiphysin IIb, a splice variant that does not bind clathrin. Endocytosis of (125)I-[d-Trp(8)]SRIF was not affected by amphiphysin IIb overexpression. However, the maximal binding capacity (B(max)) of the ligand on intact cells was significantly lower in amphiphysin IIb overexpressing than in non-transfected cells. This difference was no longer apparent when the experiments were performed on crude cell homogenates, suggesting that amphiphysin IIb overexpression interferes with SRIF receptor targeting to the cell surface and not with receptor synthesis. Accordingly, immunofluorescence experiments demonstrated that, in amphiphysin overexpressing cells, sst(2A) and sst(5) receptors were segregated in a juxtanuclear compartment identified as the trans-Golgi network. Amphiphysin IIb overexpression had no effect on corticotrophin-releasing factor 41-stimulated adrenocorticotropic hormone secretion, suggesting that it is not involved in the regulated secretory pathway. Taken together, these results suggest that amphiphysin II is not necessary for SRIF receptor endocytosis but is critical for its constitutive targeting to the plasma membrane. Therefore, amphiphysin IIb may be an important component of the constitutive secretory pathway.
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Affiliation(s)
- Philippe Sarret
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec H3A 2B4, Canada
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29
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Schuske KR, Richmond JE, Matthies DS, Davis WS, Runz S, Rube DA, van der Bliek AM, Jorgensen EM. Endophilin is required for synaptic vesicle endocytosis by localizing synaptojanin. Neuron 2004; 40:749-62. [PMID: 14622579 DOI: 10.1016/s0896-6273(03)00667-6] [Citation(s) in RCA: 202] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Endophilin is a membrane-associated protein required for endocytosis of synaptic vesicles. Two models have been proposed for endophilin: that it alters lipid composition in order to shape membranes during endocytosis, or that it binds the polyphosphoinositide phosphatase synaptojanin and recruits this phosphatase to membranes. In this study, we demonstrate that the unc-57 gene encodes the Caenorhabditis elegans ortholog of endophilin A. We demonstrate that endophilin is required in C. elegans for synaptic vesicle recycling. Furthermore, the defects observed in endophilin mutants closely resemble those observed in synaptojanin mutants. The electrophysiological phenotype of endophilin and synaptojanin double mutants are virtually identical to the single mutants, demonstrating that endophilin and synaptojanin function in the same pathway. Finally, endophilin is required to stabilize expression of synaptojanin at the synapse. These data suggest that endophilin is an adaptor protein required to localize and stabilize synaptojanin at membranes during synaptic vesicle recycling.
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Affiliation(s)
- Kimberly R Schuske
- Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112, USA
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30
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Friesen H, Murphy K, Breitkreutz A, Tyers M, Andrews B. Regulation of the yeast amphiphysin homologue Rvs167p by phosphorylation. Mol Biol Cell 2003; 14:3027-40. [PMID: 12857883 PMCID: PMC165695 DOI: 10.1091/mbc.e02-09-0613] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The yeast amphiphysin homologue Rvs167p plays a role in regulation of the actin cytoskeleton, endocytosis, and sporulation. Rvs167p is a phosphoprotein in vegetatively growing cells and shows increased phosphorylation upon treatment with mating pheromone. Previous work has shown that Rvs167p can be phosphorylated in vitro by the cyclin-dependent kinase Pho85p complexed with its cyclin Pcl2p. Using chymotryptic phosphopeptide mapping, we have identified the sites on which Rvs167p is phosphorylated in vitro by Pcl2p-Pho85p. We have shown that these same sites are phosphorylated in vivo during vegetative growth and that phosphorylation at two of these sites is Pcl-Pho85p dependent. In cells treated with mating pheromone, the MAP kinase Fus3p is needed for full phosphorylation of Rvs167p. Functional genomics and genetics experiments revealed that mutation of other actin cytoskeleton genes compromises growth of a strain in which phosphorylation of Rvs167p is blocked by mutation. Phosphorylation of Rvs167p inhibits its interaction in vitro with Las17p, an activator of the Arp2/3 complex, as well as with a novel protein, Ymr192p. Our results suggest that phosphorylation of Rvs167p by a cyclin-dependent kinase and by a MAP kinase is an important mechanism for regulating protein complexes involved in actin cytoskeleton function.
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Affiliation(s)
- Helena Friesen
- Department of Molecular and Medical Genetics, University of Toronto, Toronto, Canada, M5S 1A8
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31
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DuHadaway JB, Du W, Donover S, Baker J, Liu AX, Sharp DM, Muller AJ, Prendergast GC. Transformation-selective apoptotic program triggered by farnesyltransferase inhibitors requires Bin1. Oncogene 2003; 22:3578-88. [PMID: 12789266 DOI: 10.1038/sj.onc.1206481] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Neoplastic transformation sensitizes many cells to apoptosis. This phenomenon may underlie the therapeutic benefit of many anticancer drugs, but its molecular basis is poorly understood. We have used a selective and potent farnesyltransferase inhibitor (FTI) to probe a mechanism of apoptosis that is peculiarly linked to neoplastic transformation. While nontoxic to untransformed mouse cells, FTI triggers a massive RhoB-dependent, p53-independent apoptosis in mouse cells that are neoplastically transformed. Here we offer evidence that the BAR adapter-encoding tumor suppressor gene Bin1 is required for this transformation-selective death program. Targeted deletion of Bin1 in primary mouse embyro fibroblasts (MEFs) transformed by E1A+Ras did not affect FTI-induced reversion, actin fiber formation, or growth inhibition, but it abolished FTI-induced apoptosis. The previously defined requirement for RhoB in these effects suggests that Bin1 adapter proteins act downstream or in parallel to RhoB in cell death signaling. The death defect in Bin1 null cells was significant insofar as it abolished FTI efficacy in tumor xenograft assays. p53 deletion did not phenocopy the effects of Bin1 deletion. However, MEFs transformed by SV40 large T antigen+Ras were also resistant to apoptosis by FTI, consistent with other evidence that large T inhibits Bin1-dependent cell death by a p53-independent mechanism. Taken together, the results define a function for Bin1 in apoptosis that is conditional on transformation stress. This study advances understanding of the functions of BAR adapter proteins, which are poorly understood, by revealing genetic interactions with an Rho small GTPase that functions in stress signaling. The frequent losses of Bin1 expression that occur in human breast and prostate cancers may promote tumor progression and limit susceptibility to FTI or other therapeutic agents that exploit the heightened sensitivity of neoplastic cells to apoptosis.
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32
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Muller AJ, Baker JF, DuHadaway JB, Ge K, Farmer G, Donover PS, Meade R, Reid C, Grzanna R, Roach AH, Shah N, Soler AP, Prendergast GC. Targeted disruption of the murine Bin1/Amphiphysin II gene does not disable endocytosis but results in embryonic cardiomyopathy with aberrant myofibril formation. Mol Cell Biol 2003; 23:4295-306. [PMID: 12773571 PMCID: PMC156129 DOI: 10.1128/mcb.23.12.4295-4306.2003] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2002] [Revised: 09/02/2002] [Accepted: 03/20/2003] [Indexed: 11/20/2022] Open
Abstract
The mammalian Bin1/Amphiphysin II gene encodes an assortment of alternatively spliced adapter proteins that exhibit markedly divergent expression and subcellular localization profiles. Bin1 proteins have been implicated in a variety of different cellular processes, including endocytosis, actin cytoskeletal organization, transcription, and stress responses. To gain insight into the physiological functions of the Bin1 gene, we have disrupted it by homologous recombination in the mouse. Bin1 loss had no discernible impact on either endocytosis or phagocytosis in mouse embryo-derived fibroblasts and macrophages, respectively. Similarly, actin cytoskeletal organization, proliferation, and apoptosis in embryo fibroblasts were all unaffected by Bin1 loss. In vivo, however, Bin1 loss resulted in perinatal lethality. Bin1 has been reported to affect muscle cell differentiation and T-tubule formation. No striking histological abnormalities were evident in skeletal muscle of Bin1 null embryos, but severe ventricular cardiomyopathy was observed in these embryos. Ultrastructurally, myofibrils in ventricular cardiomyocytes of Bin1 null embryos were severely disorganized. These results define a developmentally critical role for the Bin1 gene in cardiac muscle development.
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33
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Leprince C, Le Scolan E, Meunier B, Fraisier V, Brandon N, De Gunzburg J, Camonis J. Sorting nexin 4 and amphiphysin 2, a new partnership between endocytosis and intracellular trafficking. J Cell Sci 2003; 116:1937-48. [PMID: 12668730 DOI: 10.1242/jcs.00403] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Endocytosis is a regulated physiological process by which membrane receptors and their extracellular ligands are internalized. After internalization, they enter the endosomal trafficking pathway for sorting and processing. Amphiphysins consist of a family of proteins conserved throughout evolution that are crucial elements of the endocytosis machinery in mammalian cells. They act as adaptors for a series of proteins important for the endocytic process, such as dynamin. In order to improve our knowledge of amphiphysin function, we performed a two-hybrid screen with the N-terminal part of murine amphiphysin 2 (residues 1-304). One of the interacting clones corresponded to sorting nexin 4 (SNX4), a member of the SNX family of proteins which are suspected to regulate vesicular trafficking. This interaction was confirmed in vivo by co-immunoprecipitation. Immunofluorescence analysis revealed that amphiphysin 2 might bind reticulo-vesicular structures present throughout the cell body and be associated with SNX4 on these structures. In an endocytosis assay, overexpressed C-terminal or full-length SNX4 was able to inhibit transferrin receptor endocytosis as efficiently as the SH3 domain of amphiphysin 2. At lower levels of expression, SNX4 colocalized with transferrin-containing vesicles, some of which were also positive for amphiphysin 2. These results indicate that SNX4 may be part of the endocytic machinery or, alternatively, that SNX4 may associate with key elements of endocytosis such as amphiphysin 2 and sequester them when overexpressed. The presence of amphiphysin 2 on intracellular vesicles and its interplay with SNX4, which is likely to take part in intracellular trafficking, suggest that amphiphysin 2 is not only a regulator of the early steps of endocytosis. It could also play a role at the surface of the endocytic vesicle that has just been formed and of the future endosomes, in order to regulate intracellular trafficking.
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Affiliation(s)
- Corinne Leprince
- INSERM U528, Institut Curie Section de Recherche, 26 rue d'Ulm, 75248 Paris Cedex 05, France.
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34
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Vernoud V, Horton AC, Yang Z, Nielsen E. Analysis of the small GTPase gene superfamily of Arabidopsis. PLANT PHYSIOLOGY 2003; 131:1191-208. [PMID: 12644670 PMCID: PMC166880 DOI: 10.1104/pp.013052] [Citation(s) in RCA: 427] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Small GTP-binding proteins regulate diverse processes in eukaryotic cells such as signal transduction, cell proliferation, cytoskeletal organization, and intracellular membrane trafficking. These proteins function as molecular switches that cycle between "active" and "inactive" states, and this cycle is linked to the binding and hydrolysis of GTP. The Arabidopsis genome contains 93 genes that encode small GTP-binding protein homologs. Phylogenetic analysis of these genes shows that plants contain Rab, Rho, Arf, and Ran GTPases, but no Ras GTPases. We have assembled complete lists of these small GTPases families, as well as accessory proteins that control their activity, and review what is known of the functions of individual members of these families in Arabidopsis. We also discuss the possible roles of these GTPases in relation to their similarity to orthologs with known functions and localizations in yeast and/or animal systems.
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Affiliation(s)
- Vanessa Vernoud
- Center for Plant Cell Biology and Department of Botany and Plant Sciences, University of California, Riverside, California 92521, USA
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35
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Routhier EL, Donover PS, Prendergast GC. hob1+, the fission yeast homolog of Bin1, is dispensable for endocytosis or actin organization, but required for the response to starvation or genotoxic stress. Oncogene 2003; 22:637-48. [PMID: 12569356 DOI: 10.1038/sj.onc.1206162] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
BAR (Bin/Amphiphysin/Rvs) adapter proteins have been suggested to regulate endocytosis, actin organization, apoptosis, and transcription, but their precise roles are obscure. There are at least five mammalian genes that encode BAR adapter proteins, including the evolutionarily conserved and ubiquitously expressed Bin1/Amphiphysin-II and Bin3 genes. Bin1 holds special interest as certain splice isoforms localize to the nucleus, interact with the c-Abl and c-Myc oncoproteins, and display tumor suppressor properties. To obtain functional insights, we embarked upon a genetic analysis of the two BAR adapter proteins expressed in the fission yeast Schizosaccharomyces pombe. In a previous work, a role in actin organization and cytokinesis was identified for the Bin3 homolog hob3+. In this study, a role in stress signaling was defined for the Bin1 homolog, hob1+. Notably, hob1+ was dispensable for endocytosis, actin organization, or osmotic sensitivity. Instead, mutation of hob1+ led to slight cell elongation and faulty cell cycle arrest upon nutrient starvation. These defects were complemented by Bin1, but not by Amphiphysin-I, arguing that these genes have distinct functions despite their structural similarity. hob1 delta mutant cells were also hypersensitive to genotoxic stress. This was not related to a faulty checkpoint response, but mutation in the checkpoint gene rad3(+) further exacerbated the sensitivity of hob1 delta mutant cells. Interestingly, mutation of the cell cycle regulator wee1+ partially relieved the sensitivity defect, suggesting that hob1+ may influence the efficiency of DNA repair or checkpoint release after DNA damage. Genetic and biochemical evidence indicated that hob3+ is epistatic to hob1+ in the response to genotoxic stress. Our findings indicate that the Bin1 homolog hob1+ participates in DNA damage signaling and they suggest a novel role for BAR adapter proteins in stress response processes.
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Affiliation(s)
- Eric L Routhier
- Cancer Research Group, The DuPont Pharmaceuticals Company, Glenolden, PA 19036, USA
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36
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Chang JS, Henry K, Wolf BL, Geli M, Lemmon SK. Protein phosphatase-1 binding to scd5p is important for regulation of actin organization and endocytosis in yeast. J Biol Chem 2002; 277:48002-8. [PMID: 12356757 DOI: 10.1074/jbc.m208471200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
SCD5, an essential gene, encodes a protein important for endocytosis and actin organization in yeast. Previous two-hybrid screens showed that Scd5p interacts with Glc7p, a yeast Ser/Thr-specific protein phosphatase-1 (PP1) that participates in a variety of cellular processes. PP1 substrate specificity in vivo is regulated by association with different regulatory or targeting subunits, many of which have a consensus PP1-binding site ((V/I)XF, with a basic residue at the -1 or -2 position). Scd5p contains two of these potential PP1-binding motifs: KVDF (amino acids 240-243) and KKVRF (amino acids 272-276). Deletion analysis mapped the PP1-binding domain to a region of Scd5p containing these motifs. Therefore, the consequence of mutating these two potential PP1-binding sites was examined. Although mutation of KVDF had no effect, alteration of KKVRF dramatically reduced Scd5p interaction with Glc7p and resulted in temperature-sensitive growth. Furthermore, this mutation caused defects in fluid phase and receptor-mediated endocytosis and actin organization. Overexpression of GLC7 suppressed the temperature-sensitive growth of the KKVRF mutant and partially rescued the actin organization phenotype. These results provide evidence that Scd5p is a PP1 targeting subunit for regulation of actin organization and endocytosis or that Scd5p is a PP1 substrate, which regulates the function of Scd5p in these processes.
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Affiliation(s)
- Ji Suk Chang
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, Ohio 44106-4960, USA
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37
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Henry KR, D'Hondt K, Chang J, Newpher T, Huang K, Hudson RT, Riezman H, Lemmon SK. Scd5p and clathrin function are important for cortical actin organization, endocytosis, and localization of sla2p in yeast. Mol Biol Cell 2002; 13:2607-25. [PMID: 12181333 PMCID: PMC117929 DOI: 10.1091/mbc.e02-01-0012] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
SCD5 was identified as a multicopy suppressor of clathrin HC-deficient yeast. SCD5 is essential, but an scd5-Delta338 mutant, expressing Scd5p with a C-terminal truncation of 338 amino acids, is temperature sensitive for growth. Further studies here demonstrate that scd5-Delta338 affects receptor-mediated and fluid-phase endocytosis and normal actin organization. The scd5-Delta338 mutant contains larger and depolarized cortical actin patches and a prevalence of G-actin bars. scd5-Delta338 also displays synthetic negative genetic interactions with mutations in several other proteins important for cortical actin organization and endocytosis. Moreover, Scd5p colocalizes with cortical actin. Analysis has revealed that clathrin-deficient yeast also have a major defect in cortical actin organization and accumulate G-actin. Overexpression of SCD5 partially suppresses the actin defect of clathrin mutants, whereas combining scd5-Delta338 with a clathrin mutation exacerbates the actin and endocytic phenotypes. Both Scd5p and yeast clathrin physically associate with Sla2p, a homologue of the mammalian huntingtin interacting protein HIP1 and the related HIP1R. Furthermore, Sla2p localization at the cell cortex is dependent on Scd5p and clathrin function. Therefore, Scd5p and clathrin are important for actin organization and endocytosis, and Sla2p may provide a critical link between clathrin and the actin cytoskeleton in yeast, similar to HIP1(R) in animal cells.
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Affiliation(s)
- Kenneth R Henry
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland Ohio 44106, USA
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38
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Fazi B, Cope MJTV, Douangamath A, Ferracuti S, Schirwitz K, Zucconi A, Drubin DG, Wilmanns M, Cesareni G, Castagnoli L. Unusual binding properties of the SH3 domain of the yeast actin-binding protein Abp1: structural and functional analysis. J Biol Chem 2002; 277:5290-8. [PMID: 11668184 DOI: 10.1074/jbc.m109848200] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Abp1p is an actin-binding protein that plays a central role in the organization of Saccharomyces cerevisiae actin cytoskeleton. By a combination of two-hybrid and phage-display approaches, we have identified six new ligands of the Abp1-SH3 domain. None of these SH3-mediated novel interactions was detected in recent all genome high throughput protein interaction projects. Here we show that the SH3-mediated association of Abp1p with the Ser/Thr kinases Prk1p and Ark1p is essential for their localization to actin cortical patches. The Abp1-SH3 domain has a rather unusual binding specificity, because its target peptides contain the tetrapentapeptide +XXXPXXPX+PXXL with positive charges flanking the polyproline core on both sides. Here we present the structure of the Abp1-SH3 domain solved at 1.3-A resolution. The peptide-binding pockets in the SH3 domain are flanked by two acidic residues that are uncommon at those positions in the SH3 domain family. We have shown by site-directed mutagenesis that one of these negatively charged side chains may be the key determinant for the preference for non-classical ligands.
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Affiliation(s)
- Barbara Fazi
- Department of Biology, University of Rome Tor Vergata, Via della Ricerca Scientifica, 00133 Roma, Italy
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39
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Young ME, Karpova TS, Brügger B, Moschenross DM, Wang GK, Schneiter R, Wieland FT, Cooper JA. The Sur7p family defines novel cortical domains in Saccharomyces cerevisiae, affects sphingolipid metabolism, and is involved in sporulation. Mol Cell Biol 2002; 22:927-34. [PMID: 11784867 PMCID: PMC133540 DOI: 10.1128/mcb.22.3.927-934.2002] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have discovered a novel cortical patch structure in Saccharomyces cerevisiae defined by a family of integral plasma membrane proteins, including Sur7p, Ynl194p, and Ydl222p. Sur7p-family patches localized as cortical patches that were immobile and stable. These patches were polarized to regions of the cell with a mature cell wall; they were absent from small buds and the tips of many medium-sized buds. These patches were distinct from other known cortical structures. Digestion of the cell wall caused Sur7p patches to disassemble, indicating that Sur7p requires cell wall-dependent extracellular interactions for its localization as patches. sur7Delta, ydl222Delta, and ynl194Delta mutants had reduced sporulation efficiencies. SUR7 was originally described as a multicopy suppressor of rvs167, whose product is an actin patch component. This suppression is probably mediated by sphingolipids, since deletion of SUR7, YDL222, and YNL194 altered the sphingolipid content of the yeast plasma membrane, and other SUR genes suppress rvs167 via effects on sphingolipid synthesis. In particular, the sphingoid base length and number of hydroxyl groups in inositol phosphorylceramides were altered in sur7Delta, ydl222Delta, and yne194Delta strains.
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Affiliation(s)
- Michael E Young
- Department of Cell Biology and Physiology, Washington University, St. Louis, Missouri 63110, USA
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40
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Zelhof AC, Bao H, Hardy RW, Razzaq A, Zhang B, Doe CQ. DrosophilaAmphiphysin is implicated in protein localization and membrane morphogenesis but not in synaptic vesicle endocytosis. Development 2001; 128:5005-15. [PMID: 11748137 DOI: 10.1242/dev.128.24.5005] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Amphiphysin family members are implicated in synaptic vesicle endocytosis, actin localization and one isoform is an autoantigen in neurological autoimmune disorder; however, there has been no genetic analysis of Amphiphysin function in higher eukaryotes. We show that Drosophila Amphiphysin is localized to actin-rich membrane domains in many cell types, including apical epithelial membranes, the intricately folded apical rhabdomere membranes of photoreceptor neurons and the postsynaptic density of glutamatergic neuromuscular junctions. Flies that lack all Amphiphysin function are viable, lack any observable endocytic defects, but have abnormal localization of the postsynaptic proteins Discs large, Lethal giant larvae and Scribble, altered synaptic physiology, and behavioral defects. Misexpression of Amphiphysin outside its normal membrane domain in photoreceptor neurons results in striking morphological defects. The strong misexpression phenotype coupled with the mild mutant and lack of phenotypes suggests that Amphiphysin acts redundantly with other proteins to organize specialized membrane domains within a diverse array of cell types.
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Affiliation(s)
- A C Zelhof
- Institute of Neuroscience, HHMI, University of Oregon 1254, Eugene, OR 97403, USA
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41
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Escobar-Henriques M, Balguerie A, Monribot C, Boucherie H, Daignan-Fornier B. Proteome analysis and morphological studies reveal multiple effects of the immunosuppressive drug mycophenolic acid specifically resulting from guanylic nucleotide depletion. J Biol Chem 2001; 276:46237-42. [PMID: 11535588 DOI: 10.1074/jbc.m103416200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mycophenolic acid (MPA), one of the most promising immunosuppressive drugs recently developed, is a potent inhibitor of IMP dehydrogenase, the first committed step toward GMP synthesis. We found that all the drug effects on yeast cells were prevented by bypassing GMP synthesis, thus confirming the high specificity of MPA. Although the primary target of MPA is clearly identified, we aimed to further understand how GTP depletion leads to growth arrest and developed a new approach based on proteome analysis combined with overexpression studies. Essential proteins down-expressed in the presence of MPA were identified by protein two-dimensional gel analysis and subsequently overexpressed in yeast. Two such proteins, Cdc37p and Sup45p, when overexpressed allowed partial relief of MPA toxicity, strongly suggesting that their lower amount after MPA treatment significantly contributed to the MPA effect. These conserved proteins involved in cell cycle progression and translation are therefore important secondary targets for MPA. Our data establish that MPA effects occur through inhibition of a unique primary target resulting in guanine nucleotides depletion, thereby affecting multiple cellular processes.
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Affiliation(s)
- M Escobar-Henriques
- Institut de Biochimie et Génétique Cellulaires, CNRS Unité Mixte de Recherche 5095, 1 rue Camille Saint-Saëns, F-33077 Bordeaux Cedex, France
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42
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Leventis PA, Chow BM, Stewart BA, Iyengar B, Campos AR, Boulianne GL. Drosophila Amphiphysin is a post-synaptic protein required for normal locomotion but not endocytosis. Traffic 2001; 2:839-50. [PMID: 11733051 DOI: 10.1034/j.1600-0854.2001.21113.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Clathrin-mediated endocytosis is required to recycle synaptic vesicles for fast and efficient neurotransmission. Amphiphysins are thought to be multiprotein adaptors that may contribute to this process by bringing together many of the proteins required for endocytosis. Their in vivo function, however, has yet to be determined. Here, we show that the Drosophila genome encodes a single amphiphysin gene that is broadly expressed during development. We also show that, unlike its vertebrate counterparts, Drosophila Amphiphysin is enriched postsynaptically at the larval neuromuscular junction. To determine the role of Drosophila Amphiphysin, we also generated null mutants which are viable but give rise to larvae and adults with pronounced locomotory defects. Surprisingly, the locomotory defects cannot be accounted for by alterations in the morphology or physiology of the neuromuscular junction. Moreover, using stimulus protocols designed to test endocytosis under moderate and extreme vesicle cycling, we could not detect any defect in the neuromuscular junction of the amphiphysin mutant. Taken together, our findings suggest that Amphiphysin is not required for viability, nor is it absolutely required for clathrin-mediated endocytosis. However, Drosophila Amphiphysin function is required in both larvae and adults for normal locomotion.
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Affiliation(s)
- P A Leventis
- Department of Zoology, University of Toronto, Toronto, Canada
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43
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Drees BL, Sundin B, Brazeau E, Caviston JP, Chen GC, Guo W, Kozminski KG, Lau MW, Moskow JJ, Tong A, Schenkman LR, McKenzie A, Brennwald P, Longtine M, Bi E, Chan C, Novick P, Boone C, Pringle JR, Davis TN, Fields S, Drubin DG. A protein interaction map for cell polarity development. J Cell Biol 2001; 154:549-71. [PMID: 11489916 PMCID: PMC2196425 DOI: 10.1083/jcb.200104057] [Citation(s) in RCA: 240] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Many genes required for cell polarity development in budding yeast have been identified and arranged into a functional hierarchy. Core elements of the hierarchy are widely conserved, underlying cell polarity development in diverse eukaryotes. To enumerate more fully the protein-protein interactions that mediate cell polarity development, and to uncover novel mechanisms that coordinate the numerous events involved, we carried out a large-scale two-hybrid experiment. 68 Gal4 DNA binding domain fusions of yeast proteins associated with the actin cytoskeleton, septins, the secretory apparatus, and Rho-type GTPases were used to screen an array of yeast transformants that express approximately 90% of the predicted Saccharomyces cerevisiae open reading frames as Gal4 activation domain fusions. 191 protein-protein interactions were detected, of which 128 had not been described previously. 44 interactions implicated 20 previously uncharacterized proteins in cell polarity development. Further insights into possible roles of 13 of these proteins were revealed by their multiple two-hybrid interactions and by subcellular localization. Included in the interaction network were associations of Cdc42 and Rho1 pathways with proteins involved in exocytosis, septin organization, actin assembly, microtubule organization, autophagy, cytokinesis, and cell wall synthesis. Other interactions suggested direct connections between Rho1- and Cdc42-regulated pathways; the secretory apparatus and regulators of polarity establishment; actin assembly and the morphogenesis checkpoint; and the exocytic and endocytic machinery. In total, a network of interactions that provide an integrated response of signaling proteins, the cytoskeleton, and organelles to the spatial cues that direct polarity development was revealed.
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Affiliation(s)
- B L Drees
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
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44
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Breton AM, Schaeffer J, Aigle M. The yeast Rvs161 and Rvs167 proteins are involved in secretory vesicles targeting the plasma membrane and in cell integrity. Yeast 2001; 18:1053-68. [PMID: 11481676 DOI: 10.1002/yea.755] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
The Rvs161 and Rvs167 proteins are known to play a role in actin cytokeleton organization and endocytosis. Moreover, Rvs167p functionally interacts with the myosin Myo2p. Therefore, we explored the involvement of the Rvs proteins in vesicle traffic and in cell integrity. The rvs mutants accumulate late secretory vesicles at sites of membrane and cell wall construction. They are synthetic-lethal with the slt2/mpk1 mutation, which affects the MAP kinase cascade controlled by Pkc1p and is required for cell integrity. The phenotype of the double mutants is close to that described for the pkc1 mutant. Synthetic defects for growth are also observed with mutation in KRE6, a gene coding for a glucan synthase, required for cell wall construction. These data support the idea that the Rvs proteins are involved in the late targeting of vesicles whose cargoes are required for cell wall construction.
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Affiliation(s)
- A M Breton
- Laboratoire de Biologie Cellulaire de la Levure, LBCL/IBGC/CNRS UMR 5095, 1 Rue Camille Saint-Saëns, F-33077 Bordeaux Cedex, France.
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45
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Routhier EL, Burn TC, Abbaszade I, Summers M, Albright CF, Prendergast GC. Human BIN3 complements the F-actin localization defects caused by loss of Hob3p, the fission yeast homolog of Rvs161p. J Biol Chem 2001; 276:21670-7. [PMID: 11274158 DOI: 10.1074/jbc.m101096200] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The BAR adaptor proteins encoded by the RVS167 and RVS161 genes from Saccharomyces cerevisiae form a complex that regulates actin, endocytosis, and viability following starvation or osmotic stress. In this study, we identified a human homolog of RVS161, termed BIN3 (bridging integrator-3), and a Schizosaccharomyces pombe homolog of RVS161, termed hob3+ (homolog of Bin3). In human tissues, the BIN3 gene was expressed ubiquitously except for brain. S. pombe cells lacking Hob3p were often multinucleate and characterized by increased amounts of calcofluor-stained material and mislocalized F-actin. For example, while wild-type cells localized F-actin to cell ends during interphase, hob3Delta mutants had F-actin patches distributed randomly around the cell. In addition, medial F-actin rings were rarely found in hob3Delta mutants. Notably, in contrast to S. cerevisiae rvs161Delta mutants, hob3Delta mutants showed no measurable defects in endocytosis or response to osmotic stress, yet hob3+ complemented the osmosensitivity of a rvs161Delta mutant. BIN3 failed to rescue the osmosensitivity of rvs161Delta, but the actin localization defects of hob3Delta mutants were completely rescued by BIN3 and partially rescued by RVS161. These findings suggest that hob3+ and BIN3 regulate F-actin localization, like RVS161, but that other roles for this gene have diverged somewhat during evolution.
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Affiliation(s)
- E L Routhier
- Cancer Research Group, DuPont Pharmaceuticals Company, Glenolden Laboratory, Glenolden, Pennsylvania 19036, USA
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46
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Munn AL. Molecular requirements for the internalisation step of endocytosis: insights from yeast. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1535:236-57. [PMID: 11278164 DOI: 10.1016/s0925-4439(01)00028-x] [Citation(s) in RCA: 111] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Molecular genetic studies of endocytosis using the unicellular eukaryote Saccharomyces cerevisiae (budding yeast) have led to the identification of many cellular components, both proteins and lipids, required for this process. While initially, many of these requirements (e.g. for actin, various actin-associated proteins, the ubiquitin conjugation system, and for ergosterol and sphingolipids) appeared to differ from known requirements for endocytosis in higher eukaryotes (e.g. clathrin, AP-2, dynamin), it now seems that endocytosis in higher and lower eukaryotes share many requirements. Often, what were initially identified as actin cytoskeleton-associated proteins in S. cerevisiae, are now revealing themselves as clathrin-coated pit- and vesicle-associated proteins in higher eukaryotes. So rather than delineating two endocytic pathways, one actin-based and one clathrin-based, the combined studies on higher and lower eukaryotes are revealing interesting interplay in both systems between the actin cytoskeleton, clathrin coats, and lipids in the formation of endocytic vesicles at the plasma membrane. Recent results from the yeast system show that the Arp2/3p complex, Wiskott-Aldrich syndrome protein (WASP), and WASP-interacting protein (WIP), proteins involved in the nucleation step of actin filament assembly, play a major role in the formation of endocytic vesicles. This discovery suggests models whereby endocytic vesicles may be actively pushed from the plasma membrane and into the cell by newly forming and rapidly extending actin filaments.
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Affiliation(s)
- A L Munn
- Laboratory of Yeast Cell Biology, Institute of Molecular Agrobiology, 1 Research Link, National University of Singapore, 117604, Singapore.
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47
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Lombardi R, Riezman H. Rvs161p and Rvs167p, the two yeast amphiphysin homologs, function together in vivo. J Biol Chem 2001; 276:6016-22. [PMID: 11096097 DOI: 10.1074/jbc.m008735200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mutations in RVS161 and RVS167, the two yeast amphiphysin homologs, cause very similar growth phenotypes, a depolarized actin cytoskeleton, and a defect in the internalization step of endocytosis. Rvs161p and Rvs167p have been shown to interact in the two-hybrid system, but their localization in the cell may be different thus raising the question whether the interaction is physiologically relevant. Here we demonstrate that the two proteins function together in vivo. We find that the steady state level of Rvs167p is strongly reduced in an rvs161Delta strain. Similarly, the level of Rvs161p is strongly reduced in an rvs167Delta strain. We demonstrate that these reduced protein levels at steady state are due to a decreased stability of either Rvs protein in the absence of the other protein. Furthermore, we find that the amount and ratio of Rvs161p and Rvs167p are critical parameters for receptor-mediated endocytosis. In addition, by using the two-hybrid system we show that the interaction of Rvs167p with actin is not abolished in an abp1Delta strain suggesting that Abp1p is not essential for this interaction.
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Affiliation(s)
- R Lombardi
- Biozentrum of the University of Basel, CH-4056 Basel, Switzerland
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48
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Abstract
The yeast Saccharomyces cerevisiae is a very powerful system for cell biological research. Recent advances in electronic light microscopy together with the application of green fluorescent protein and other in vivo staining techniques have allowed novel and exciting insights into structural organization and dynamics of cells as small as yeast. Methods for staining yeast for microscopic inspection and for introducing tags for localization studies of proteins in living or fixed cells are summarized. Electronic light microscopy, video/deconvolution methods, and confocal laser scanning microscopy as novel tools for structural analyses, and their practical applications in yeast, are discussed.
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Affiliation(s)
- S D Kohlwein
- SFB Biomembrane Research Center, Department of Biochemistry, Technical University Graz, Petersgasse 12, A-8010 Graz, Austria.
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49
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Ives EB, Nichols J, Wente SR, York JD. Biochemical and functional characterization of inositol 1,3,4,5, 6-pentakisphosphate 2-kinases. J Biol Chem 2000; 275:36575-83. [PMID: 10960485 DOI: 10.1074/jbc.m007586200] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Synthesis of inositol 1,2,3,4,5,6-hexakisphosphate (IP(6)), also known as phytate, is integral to cellular function in all eukaryotes. Production of IP(6) predominately occurs through phosphorylation of inositol 1,3,4,5,6-pentakisphosphate (IP(5)) by a 2-kinase. Recent cloning of the gene encoding this kinase from Saccharomyces cerevisiae, designated scIpk1, has identified a cellular role for IP(6) production in the regulation of mRNA export from the nucleus. In this report, we characterize the biochemical and functional parameters of recombinant scIpk1. Purified recombinant scIpk1 kinase activity is highly selective for IP(5) substrate and exhibits apparent K(m) values of 644 nm and 62.8 microm for IP(5) and ATP, respectively. The observed apparent catalytic efficiency (k(cat)/K(m)) of scIpk1 is 31,610 s(-)(1) m(-)(1). A sequence similarity search was used to identify an IP(5) 2-kinase from the fission yeast Schizosaccharomyces pombe. Recombinant spIpk1 has similar substrate selectivity and catalytic efficiency to its budding yeast counterpart, despite sharing only 24% sequence identity. Cells lacking sc-IPK1 are deficient in IP(6) production and exhibit lethality in combination with a gle1 mutant allele. Both of these phenotypes are complemented by expression of the spIPK1 gene in the sc-ipk1 cells. Analysis of several inactive mutants and multiple sequence alignment of scIpk1, spIpk1, and a putative Candida albicans Ipk1 have identified residues involved in catalysis. This includes two conserved motifs: E(i/l/m)KPKWL(t/y) and LXMTLRDV(t/g)(l/c)(f/y)I. Our data suggest that the mechanism for IP(6) production is conserved across species.
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Affiliation(s)
- E B Ives
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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Ochoa GC, Slepnev VI, Neff L, Ringstad N, Takei K, Daniell L, Kim W, Cao H, McNiven M, Baron R, De Camilli P. A functional link between dynamin and the actin cytoskeleton at podosomes. J Cell Biol 2000; 150:377-89. [PMID: 10908579 PMCID: PMC2180219 DOI: 10.1083/jcb.150.2.377] [Citation(s) in RCA: 285] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/1999] [Accepted: 06/14/2000] [Indexed: 01/07/2023] Open
Abstract
Cell transformation by Rous sarcoma virus results in a dramatic change of adhesion structures with the substratum. Adhesion plaques are replaced by dot-like attachment sites called podosomes. Podosomes are also found constitutively in motile nontransformed cells such as leukocytes, macrophages, and osteoclasts. They are represented by columnar arrays of actin which are perpendicular to the substratum and contain tubular invaginations of the plasma membrane. Given the similarity of these tubules to those generated by dynamin around a variety of membrane templates, we investigated whether dynamin is present at podosomes. Immunoreactivities for dynamin 2 and for the dynamin 2-binding protein endophilin 2 (SH3P8) were detected at podosomes of transformed cells and osteoclasts. Furthermore, GFP wild-type dynamin 2aa was targeted to podosomes. As shown by fluorescence recovery after photobleaching, GFP-dynamin 2aa and GFP-actin had a very rapid and similar turnover at podosomes. Expression of the GFP-dynamin 2aa(G273D) abolished podosomes while GFP-dynamin(K44A) was targeted to podosomes but delayed actin turnover. These data demonstrate a functional link between a member of the dynamin family and actin at attachment sites between cells and the substratum.
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Affiliation(s)
- Gian-Carlo Ochoa
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06510
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06510
| | - Vladimir I. Slepnev
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06510
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06510
| | - Lynn Neff
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06510
- Department of Orthopaedic Surgery, Yale University School of Medicine, New Haven, Connecticut 06510
| | - Niels Ringstad
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06510
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06510
| | - Kohji Takei
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06510
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06510
| | - Laurie Daniell
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06510
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06510
| | - Warren Kim
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06510
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06510
| | - Hong Cao
- Mayo Clinic, Rochester, Minnesota 55905
| | | | - Roland Baron
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06510
- Department of Orthopaedic Surgery, Yale University School of Medicine, New Haven, Connecticut 06510
| | - Pietro De Camilli
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06510
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06510
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