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Ejzykowicz DE, Locken KM, Ruiz FJ, Manandhar SP, Olson DK, Gharakhanian E. Hygromycin B hypersensitive (hhy) mutants implicate an intact trans-Golgi and late endosome interface in efficient Tor1 vacuolar localization and TORC1 function. Curr Genet 2016; 63:531-551. [PMID: 27812735 DOI: 10.1007/s00294-016-0660-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Revised: 10/20/2016] [Accepted: 10/22/2016] [Indexed: 12/18/2022]
Abstract
Saccharomyces cerevisiae vacuoles are functionally analogous to mammalian lysosomes. Both also serve as physical platforms for Tor Complex 1 (TORC1) signal transduction, the master regulator of cellular growth and proliferation. Hygromycin B is a eukaryotic translation inhibitor. We recently reported on hygromycin B hypersensitive (hhy) mutants that fail to grow at subtranslation inhibitory concentrations of the drug and exhibit vacuolar defects (Banuelos et al. in Curr Genet 56:121-137, 2010). Here, we show that hhy phenotype is not due to increased sensitivity to translation inhibition and establish a super HHY (s-HHY) subgroup of genes comprised of ARF1, CHC1, DRS2, SAC1, VPS1, VPS34, VPS45, VPS52, and VPS54 that function exclusively or inclusively at trans-Golgi and late endosome interface. Live cell imaging of s-hhy mutants revealed that hygromycin B treatment disrupts vacuolar morphology and the localization of late endosome marker Pep12, but not that of late endosome-independent vacuolar SNARE Vam3. This, along with normal post-late endosome trafficking of the vital dye FM4-64, establishes that severe hypersensitivity to hygromycin B correlates specifically with compromised trans-Golgi and late endosome interface. We also show that Tor1p vacuolar localization and TORC1 anabolic functions, including growth promotion and phosphorylation of its direct substrate Sch9, are compromised in s-hhy mutants. Thus, an intact trans-Golgi and late endosome interface is a requisite for efficient Tor1 vacuolar localization and TORC1 function.
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Affiliation(s)
- Daniele E Ejzykowicz
- Department of Biological Sciences, California State University Long Beach, 1250 Bellflower Blvd, Long Beach, CA, 90840, USA
| | - Kristopher M Locken
- Department of Biological Sciences, California State University Long Beach, 1250 Bellflower Blvd, Long Beach, CA, 90840, USA
| | - Fiona J Ruiz
- Department of Biological Sciences, California State University Long Beach, 1250 Bellflower Blvd, Long Beach, CA, 90840, USA.,Department of Radiation Oncology, Cancer Biology Division, Washington University School of Medicine, Saint Louis, MO, 63108, USA
| | - Surya P Manandhar
- Department of Biological Sciences, California State University Long Beach, 1250 Bellflower Blvd, Long Beach, CA, 90840, USA
| | - Daniel K Olson
- Department of Biological Sciences, California State University Long Beach, 1250 Bellflower Blvd, Long Beach, CA, 90840, USA.,Inouye Center for Microbial Oceanography, Research and Education, University of Hawaii, Manoa, Honolulu, HI, 96822, USA
| | - Editte Gharakhanian
- Department of Biological Sciences, California State University Long Beach, 1250 Bellflower Blvd, Long Beach, CA, 90840, USA.
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A genome-wide immunodetection screen in S. cerevisiae uncovers novel genes involved in lysosomal vacuole function and morphology. PLoS One 2011; 6:e23696. [PMID: 21912603 PMCID: PMC3166051 DOI: 10.1371/journal.pone.0023696] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Accepted: 07/22/2011] [Indexed: 11/19/2022] Open
Abstract
Vacuoles of yeast Saccharomyces cerevisiae are functionally analogous to mammalian lysosomes. Both are cellular organelles responsible for macromolecular degradation, ion/pH homeostasis, and stress survival. We hypothesized that undefined gene functions remain at post-endosomal stage of vacuolar events and performed a genome-wide screen directed at such functions at the late endosome and vacuole interface – ENV genes. The immunodetection screen was designed to identify mutants that internally accumulate precursor form of the vacuolar hydrolase carboxypeptidase Y (CPY). Here, we report the uncovering and initial characterizations of twelve ENV genes. The small size of the collection and the lack of genes previously identified with vacuolar events are suggestive of the intended exclusive functional interface of the screen. Most notably, the collection includes four novel genes ENV7, ENV9, ENV10, and ENV11, and three genes previously linked to mitochondrial processes – MAM3, PCP1, PPE1. In all env mutants, vesicular trafficking stages were undisturbed in live cells as assessed by invertase and active α-factor secretion, as well as by localization of the endocytic fluorescent marker FM4-64 to the vacuole. Several mutants exhibit defects in stress survival functions associated with vacuoles. Confocal fluorescence microscopy revealed the collection to be significantly enriched in vacuolar morphologies suggestive of fusion and fission defects. These include the unique phenotype of lumenal vesicles within vacuoles in the novel env9Δ mutant and severely fragmented vacuoles upon deletion of GET4, a gene recently implicated in tail anchored membrane protein insertion. Thus, our results establish new gene functions in vacuolar function and morphology, and suggest a link between vacuolar and mitochondrial events.
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Gharakhanian E, Chima-Okereke O, Olson DK, Frost C, Kathleen Takahashi M. env1 Mutant of VPS35 gene exhibits unique protein localization and processing phenotype at Golgi and lysosomal vacuole in Saccharomyces cerevisiae. Mol Cell Biochem 2010; 346:187-95. [PMID: 20936498 DOI: 10.1007/s11010-010-0604-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2010] [Accepted: 09/23/2010] [Indexed: 11/26/2022]
Abstract
The yeast vacuole is functionally and structurally equivalent to the mammalian lysosome. Delivery of resident and cargo proteins to the lysosome is vital for proper cellular operations, and failure to correctly target proteins to the organelle is correlated with the development of neurodegenerative and lysosomal storage diseases. We previously reported a novel mutant screen for vacuolar trafficking defects in yeast Saccharomyces cerevisiae that resulted in the isolation of env1, an allelic mutant of VPS35. As a member of the retromer complex, Vps35p binds directly to cargos and facilitates their retrograde transport to trans Golgi from endosomes. Our previous studies established that env1 exhibits unique pleiotropic phenotype in comparison to other tested VPS35 alleles including severe growth sensitivity to hygromycin B and internal accumulation of the precursor form of the vacuolar enzyme carboxypeptidase Y. Here, through a combination of sub-cellular fractionation and indirect immunofluorescence microscopy, we confirm and extend the unique phenotype of env1 to processing and localization of additional proteins within the vacuolar trafficking pathway. In comparative studies with a null and an allelic mutant of VPS35, env1 exhibited unique processing defects of retromer-independent vacuolar membrane enzyme alkaline phosphatase at the vacuole and significant Golgi localization of retromer cargos Vps10p and Kex2p despite compromised trafficking at the Golgi and late endosome interface.
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Affiliation(s)
- Editte Gharakhanian
- Department of Biological Sciences, California State University at Long Beach, 1250 Bellflower Blvd, Long Beach, CA 90840, USA.
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Banuelos MG, Moreno DE, Olson DK, Nguyen Q, Ricarte F, Aguilera-Sandoval CR, Gharakhanian E. Genomic analysis of severe hypersensitivity to hygromycin B reveals linkage to vacuolar defects and new vacuolar gene functions in Saccharomyces cerevisiae. Curr Genet 2009; 56:121-37. [PMID: 20043226 DOI: 10.1007/s00294-009-0285-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2009] [Revised: 11/30/2009] [Accepted: 12/16/2009] [Indexed: 12/19/2022]
Abstract
The vacuole of Saccharomyces cerevisiae has been a seminal model for studies of lysosomal trafficking, biogenesis, and function. Several yeast mutants defective in such vacuolar events have been unable to grow at low levels of hygromycin B, an aminoglycoside antibiotic. We hypothesized that such severe hypersensitivity to hygromycin B (hhy) is linked to vacuolar defects and performed a genomic screen for the phenotype using a haploid deletion strain library of non-essential genes. Fourteen HHY genes were initially identified and were subjected to bioinformatics analyses. The uncovered hhy mutants were experimentally characterized with respect to vesicular trafficking, vacuole morphology, and growth under various stress and drug conditions. The combination of bioinformatics analyses and phenotypic characterizations implicate defects in vesicular trafficking, vacuole fusion/fission, or vacuole function in all hhy mutants. The collection was enriched for sensitivity to monensin, indicative of vacuolar trafficking defects. Additionally, all hhy mutants showed severe sensitivities to rapamycin and caffeine, suggestive of TOR kinase pathway defects. Our experimental results also establish a new role in vacuolar and vesicular functions for two genes: PAF1, encoding a RNAP II-associated protein required for expression of cell cycle-regulated genes, and TPD3, encoding the regulatory subunit of protein phosphatase 2A. Thus, our results support linkage between severe hypersensitivity to hygromycin B and vacuolar defects.
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Affiliation(s)
- M G Banuelos
- Department of Biological Sciences, California State University at Long Beach, 1250 Bellflower Blvd, Long Beach, CA 90840, USA
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Vergés M. Retromer: multipurpose sorting and specialization in polarized transport. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2008; 271:153-98. [PMID: 19081543 DOI: 10.1016/s1937-6448(08)01204-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Retromer is an evolutionary conserved protein complex required for endosome-to-Golgi retrieval of lysosomal hydrolases' receptors. A dimer of two sorting nexins-typically, SNX1 and/or SNX2-deforms the membrane and thus cooperates with retromer to ensure cargo sorting. Research in various model organisms indicates that retromer participates in sorting of additional molecules whose proper transport has important repercussions in development and disease. The role of retromer as well as SNXs in endosomal protein (re)cycling and protein targeting to specialized plasma membrane domains in polarized cells adds further complexity and has implications in growth control, the establishment of developmental patterns, cell adhesion, and migration. This chapter will discuss the functions of retromer described in various model systems and will focus on relevant aspects in polarized transport.
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Affiliation(s)
- Marcel Vergés
- Laboratory of Epithelial Cell Biology, Centro de Investigación Príncipe Felipe, C/E.P. Avda. Autopista del Saler, Valencia, Spain
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