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Duplicated ribosomal protein paralogs promote alternative translation and drug resistance. Nat Commun 2022; 13:4938. [PMID: 35999447 PMCID: PMC9399092 DOI: 10.1038/s41467-022-32717-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Accepted: 08/12/2022] [Indexed: 11/28/2022] Open
Abstract
Ribosomes are often seen as monolithic machines produced from uniformly regulated genes. However, in yeast most ribosomal proteins come from duplicated genes. Here, we demonstrate that gene duplication may serve as a stress-adaptation mechanism modulating the global proteome through the differential expression of ribosomal protein paralogs. Our data indicate that the yeast paralog pair of the ribosomal protein L7/uL30 produces two differentially acetylated proteins. Under normal conditions most ribosomes incorporate the hypo-acetylated major form favoring the translation of genes with short open reading frames. Exposure to drugs, on the other hand, increases the production of ribosomes carrying the hyper-acetylated minor paralog that increases translation of long open reading frames. Many of these paralog-dependent genes encode cell wall proteins that could promote tolerance to drugs as their translation increases after exposure to drugs. Together our data suggest a mechanism of translation control that functions through a differential use of near-identical ribosomal protein isoforms. Most yeast ribosomal protein genes are duplicated but the functional significance of this duplication remains unclear. This study identifies a natural program where changing the ratio of proteins produced from duplicated genes modifies translation in response to drugs regardless of ribosome number.
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Staurosporine Induces Filamentation in the Human Fungal Pathogen Candida albicans via Signaling through Cyr1 and Protein Kinase A. mSphere 2017; 2:mSphere00056-17. [PMID: 28261668 PMCID: PMC5332603 DOI: 10.1128/msphere.00056-17] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Accepted: 02/09/2017] [Indexed: 01/10/2023] Open
Abstract
The impact of fungal pathogens on human health is devastating. One of the most pervasive fungal pathogens is Candida albicans, which kills ~40% of people suffering from bloodstream infections. Treatment of these infections is extremely difficult, as fungi are closely related to humans, and there are limited drugs that kill the fungus without host toxicity. The capacity of C. albicans to transition between yeast and filamentous forms is a key virulence trait. Thus, understanding the genetic pathways that regulate morphogenesis could provide novel therapeutic targets to treat C. albicans infections. Here, we establish the small molecule staurosporine as an inducer of filamentous growth. We unveil distinct regulatory circuitry required for staurosporine-induced filamentation that appears to be unique to this filament-inducing cue. Thus, this work highlights the fact that small molecules, such as staurosporine, can improve our understanding of the pathways required for key virulence programs, which may lead to the development of novel therapeutics. Protein kinases are key regulators of signal transduction pathways that participate in diverse cellular processes. In fungal pathogens, kinases regulate signaling pathways that govern drug resistance, stress adaptation, and pathogenesis. The impact of kinases on the fungal regulatory circuitry has recently garnered considerable attention in the opportunistic fungal pathogen Candida albicans, which is a leading cause of human morbidity and mortality. Complex regulatory circuitry governs the C. albicans morphogenetic transition between yeast and filamentous growth, which is a key virulence trait. Here, we report that staurosporine, a promiscuous kinase inhibitor that abrogates fungal drug resistance, also influences C. albicans morphogenesis by inducing filamentation in the absence of any other inducing cue. We further establish that staurosporine exerts its effect via the adenylyl cyclase Cyr1 and the cyclic AMP (cAMP)-dependent protein kinase A (PKA). Strikingly, filamentation induced by staurosporine does not require the known upstream regulators of Cyr1, Ras1 or Pkc1, or effectors downstream of PKA, including Efg1. We further demonstrate that Cyr1 is capable of activating PKA to enable filamentation in response to staurosporine through a mechanism that does not require degradation of the transcriptional repressor Nrg1. We establish that staurosporine-induced filamentation is accompanied by a defect in septin ring formation, implicating cell cycle kinases as potential staurosporine targets underpinning this cellular response. Thus, we establish staurosporine as a chemical probe to elucidate the architecture of cellular signaling governing fungal morphogenesis and highlight the existence of novel circuitry through which the Cyr1 and PKA govern a key virulence trait. IMPORTANCE The impact of fungal pathogens on human health is devastating. One of the most pervasive fungal pathogens is Candida albicans, which kills ~40% of people suffering from bloodstream infections. Treatment of these infections is extremely difficult, as fungi are closely related to humans, and there are limited drugs that kill the fungus without host toxicity. The capacity of C. albicans to transition between yeast and filamentous forms is a key virulence trait. Thus, understanding the genetic pathways that regulate morphogenesis could provide novel therapeutic targets to treat C. albicans infections. Here, we establish the small molecule staurosporine as an inducer of filamentous growth. We unveil distinct regulatory circuitry required for staurosporine-induced filamentation that appears to be unique to this filament-inducing cue. Thus, this work highlights the fact that small molecules, such as staurosporine, can improve our understanding of the pathways required for key virulence programs, which may lead to the development of novel therapeutics.
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Parenteau J, Lavoie M, Catala M, Malik-Ghulam M, Gagnon J, Abou Elela S. Preservation of Gene Duplication Increases the Regulatory Spectrum of Ribosomal Protein Genes and Enhances Growth under Stress. Cell Rep 2015; 13:2516-2526. [DOI: 10.1016/j.celrep.2015.11.033] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Revised: 09/15/2015] [Accepted: 11/09/2015] [Indexed: 02/08/2023] Open
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Cokol M, Weinstein ZB, Yilancioglu K, Tasan M, Doak A, Cansever D, Mutlu B, Li S, Rodriguez-Esteban R, Akhmedov M, Guvenek A, Cokol M, Cetiner S, Giaever G, Iossifov I, Nislow C, Shoichet B, Roth FP. Large-scale identification and analysis of suppressive drug interactions. CHEMISTRY & BIOLOGY 2014; 21:541-551. [PMID: 24704506 PMCID: PMC4281482 DOI: 10.1016/j.chembiol.2014.02.012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2013] [Revised: 01/26/2014] [Accepted: 02/07/2014] [Indexed: 11/29/2022]
Abstract
One drug may suppress the effects of another. Although knowledge of drug suppression is vital to avoid efficacy-reducing drug interactions or discover countermeasures for chemical toxins, drug-drug suppression relationships have not been systematically mapped. Here, we analyze the growth response of Saccharomyces cerevisiae to anti-fungal compound ("drug") pairs. Among 440 ordered drug pairs, we identified 94 suppressive drug interactions. Using only pairs not selected on the basis of their suppression behavior, we provide an estimate of the prevalence of suppressive interactions between anti-fungal compounds as 17%. Analysis of the drug suppression network suggested that Bromopyruvate is a frequently suppressive drug and Staurosporine is a frequently suppressed drug. We investigated potential explanations for suppressive drug interactions, including chemogenomic analysis, coaggregation, and pH effects, allowing us to explain the interaction tendencies of Bromopyruvate.
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Affiliation(s)
- Murat Cokol
- Biological Sciences and Bioengineering Program, Faculty of Engineering and Natural Sciences, Sabanci University, Istanbul 34956, Turkey; Nanotechnology Research and Application Center, Sabanci University, Istanbul 34956, Turkey.
| | - Zohar B Weinstein
- Biological Sciences and Bioengineering Program, Faculty of Engineering and Natural Sciences, Sabanci University, Istanbul 34956, Turkey; Donnelly Centre, University of Toronto, Toronto, ON M5S 3E1, Canada
| | - Kaan Yilancioglu
- Biological Sciences and Bioengineering Program, Faculty of Engineering and Natural Sciences, Sabanci University, Istanbul 34956, Turkey; Donnelly Centre, University of Toronto, Toronto, ON M5S 3E1, Canada
| | - Murat Tasan
- Donnelly Centre, University of Toronto, Toronto, ON M5S 3E1, Canada
| | - Allison Doak
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Dilay Cansever
- Biological Sciences and Bioengineering Program, Faculty of Engineering and Natural Sciences, Sabanci University, Istanbul 34956, Turkey; Donnelly Centre, University of Toronto, Toronto, ON M5S 3E1, Canada
| | - Beste Mutlu
- Biological Sciences and Bioengineering Program, Faculty of Engineering and Natural Sciences, Sabanci University, Istanbul 34956, Turkey; Donnelly Centre, University of Toronto, Toronto, ON M5S 3E1, Canada
| | - Siyang Li
- Donnelly Centre, University of Toronto, Toronto, ON M5S 3E1, Canada
| | - Raul Rodriguez-Esteban
- Department of Computational Biology, Boehringer Ingelheim Pharmaceuticals, Ridgefield, CT 06877, USA
| | - Murodzhon Akhmedov
- Biological Sciences and Bioengineering Program, Faculty of Engineering and Natural Sciences, Sabanci University, Istanbul 34956, Turkey
| | - Aysegul Guvenek
- Biological Sciences and Bioengineering Program, Faculty of Engineering and Natural Sciences, Sabanci University, Istanbul 34956, Turkey
| | - Melike Cokol
- Biological Sciences and Bioengineering Program, Faculty of Engineering and Natural Sciences, Sabanci University, Istanbul 34956, Turkey
| | - Selim Cetiner
- Biological Sciences and Bioengineering Program, Faculty of Engineering and Natural Sciences, Sabanci University, Istanbul 34956, Turkey
| | - Guri Giaever
- Donnelly Centre, University of Toronto, Toronto, ON M5S 3E1, Canada; Department of Pharmaceutical Sciences, University of British Columbia, 2405 Wesbrook Mall, Vancouver, BC V6T 1Z3, Canada
| | - Ivan Iossifov
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA
| | - Corey Nislow
- Donnelly Centre, University of Toronto, Toronto, ON M5S 3E1, Canada; Department of Pharmaceutical Sciences, University of British Columbia, 2405 Wesbrook Mall, Vancouver, BC V6T 1Z3, Canada
| | - Brian Shoichet
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Frederick P Roth
- Donnelly Centre, University of Toronto, Toronto, ON M5S 3E1, Canada; Center for Cancer Systems Biology, Dana-Farber Cancer Institute, One Jimmy Fund Way, Boston, MA 02215, USA; Lunenfeld-Tanenbaum Research Institute, Mt. Sinai Hospital, Toronto, ON M5G 1X5, Canada; Departments of Molecular Genetics and Computer Science, University of Toronto, Toronto, ON M5S 3E1, Canada.
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Mathioni SM, Patel N, Riddick B, Sweigard JA, Czymmek KJ, Caplan JL, Kunjeti SG, Kunjeti S, Raman V, Hillman BI, Kobayashi DY, Donofrio NM. Transcriptomics of the rice blast fungus Magnaporthe oryzae in response to the bacterial antagonist Lysobacter enzymogenes reveals candidate fungal defense response genes. PLoS One 2013; 8:e76487. [PMID: 24098512 PMCID: PMC3789685 DOI: 10.1371/journal.pone.0076487] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Accepted: 08/28/2013] [Indexed: 12/15/2022] Open
Abstract
Plants and animals have evolved a first line of defense response to pathogens called innate or basal immunity. While basal defenses in these organisms are well studied, there is almost a complete lack of understanding of such systems in fungal species, and more specifically, how they are able to detect and mount a defense response upon pathogen attack. Hence, the goal of the present study was to understand how fungi respond to biotic stress by assessing the transcriptional profile of the rice blast pathogen, Magnaporthe oryzae, when challenged with the bacterial antagonist Lysobacter enzymogenes. Based on microscopic observations of interactions between M. oryzae and wild-type L. enzymogenes strain C3, we selected early and intermediate stages represented by time-points of 3 and 9 hours post-inoculation, respectively, to evaluate the fungal transcriptome using RNA-seq. For comparative purposes, we also challenged the fungus with L. enzymogenes mutant strain DCA, previously demonstrated to be devoid of antifungal activity. A comparison of transcriptional data from fungal interactions with the wild-type bacterial strain C3 and the mutant strain DCA revealed 463 fungal genes that were down-regulated during attack by C3; of these genes, 100 were also found to be up-regulated during the interaction with DCA. Functional categorization of genes in this suite included those with roles in carbohydrate metabolism, cellular transport and stress response. One gene in this suite belongs to the CFEM-domain class of fungal proteins. Another CFEM class protein called PTH11 has been previously characterized, and we found that a deletion in this gene caused advanced lesion development by C3 compared to its growth on the wild-type fungus. We discuss the characterization of this suite of 100 genes with respect to their role in the fungal defense response.
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Affiliation(s)
- Sandra M. Mathioni
- Department of Plant and Soil Sciences, University of Delaware, Newark, Delaware, United States of America
| | - Nrupali Patel
- Department of Plant Biology and Pathology, Rutgers University, New Brunswick, New Jersey, United States of America
| | - Bianca Riddick
- Department of Plant and Soil Sciences, University of Delaware, Newark, Delaware, United States of America
| | - James A. Sweigard
- DuPont Stine Haskell Research Center, Newark, Delaware, United States of America
| | - Kirk J. Czymmek
- Delaware Biotechnology Institute BioImaging Center, University of Delaware, Newark, Delaware, United States of America
- Department of Biological Sciences, University of Delaware, Newark, Delaware, United States of America
| | - Jeffrey L. Caplan
- Delaware Biotechnology Institute BioImaging Center, University of Delaware, Newark, Delaware, United States of America
| | - Sridhara G. Kunjeti
- Department of Plant and Soil Sciences, University of Delaware, Newark, Delaware, United States of America
| | - Saritha Kunjeti
- Department of Plant and Soil Sciences, University of Delaware, Newark, Delaware, United States of America
| | - Vidhyavathi Raman
- Department of Plant and Soil Sciences, University of Delaware, Newark, Delaware, United States of America
| | - Bradley I. Hillman
- Department of Plant Biology and Pathology, Rutgers University, New Brunswick, New Jersey, United States of America
| | - Donald Y. Kobayashi
- Department of Plant Biology and Pathology, Rutgers University, New Brunswick, New Jersey, United States of America
- * E-mail: (DYK); (NMD)
| | - Nicole M. Donofrio
- Department of Plant and Soil Sciences, University of Delaware, Newark, Delaware, United States of America
- * E-mail: (DYK); (NMD)
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Hernández A, Jiang X, Cubero B, Nieto PM, Bressan RA, Hasegawa PM, Pardo JM. Mutants of the Arabidopsis thaliana cation/H+ antiporter AtNHX1 conferring increased salt tolerance in yeast: the endosome/prevacuolar compartment is a target for salt toxicity. J Biol Chem 2009; 284:14276-85. [PMID: 19307188 PMCID: PMC2682876 DOI: 10.1074/jbc.m806203200] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2008] [Revised: 03/19/2009] [Indexed: 01/13/2023] Open
Abstract
Mutants of the plant cation/H(+) antiporter AtNHX1 that confer greater halotolerance were generated by random mutagenesis and selected in yeast by phenotypic complementation. The amino acid substitutions that were selected were conservative and occurred in the second half of the membrane-associated N terminus. AtNHX1 complemented the lack of endogenous ScNHX1 in endosomal protein trafficking assays. Growth enhancement on hygromycin B and vanadate media agreed with a generally improved endosomal/prevacuolar function of the mutated proteins. In vivo measurements by (31)P NMR revealed that wild-type and mutant AtNHX1 transporters did not affect cytosolic or vacuolar pH. Surprisingly, when yeast cells were challenged with lithium, a tracer for sodium, the main effect of the mutations in AtNHX1 was a reduction in the amount of compartmentalized lithium. When purified and reconstituted into proteoliposomes or assayed in intact vacuoles isolated from yeast cells, a representative mutant transporter (V318I) showed a greater cation discrimination favoring potassium transport over that of sodium or lithium. Together, our data suggest that the endosome/prevacuolar compartment is a target for salt toxicity. Poisoning by toxic cations in the endosome/prevacuolar compartment is detrimental for cell functions, but it can be alleviated by improving the discrimination of transported alkali cations by the resident cation/H(+) antiporter.
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Affiliation(s)
- Agustín Hernández
- Instituto de Recursos Naturales y Agrobiología, Consejo Superior de Investigaciones Científicas (IRNASE-CSIC), Avda. Reina Mercedes 10, Seville 41012, Spain
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Dawson K, Toone WM, Jones N, Wilkinson CRM. Loss of regulators of vacuolar ATPase function and ceramide synthesis results in multidrug sensitivity in Schizosaccharomyces pombe. EUKARYOTIC CELL 2008; 7:926-37. [PMID: 18441123 PMCID: PMC2446650 DOI: 10.1128/ec.00037-08] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2008] [Accepted: 04/11/2008] [Indexed: 11/20/2022]
Abstract
We undertook a screen to isolate determinants of drug resistance in fission yeast and identified two genes that, when mutated, result in sensitivity to a range of structurally unrelated compounds, some of them commonly used in the clinic. One gene, rav1, encodes the homologue of a budding yeast protein which regulates the assembly of the vacuolar ATPase. The second gene, lac1, encodes a homologue of genes that are required for ceramide synthesis. Both mutants are sensitive to the chemotherapeutic agent doxorubicin, and using the naturally fluorescent properties of this compound, we found that both rav1 and lac1 mutations result in an increased accumulation of the drug in cells. The multidrug-sensitive phenotype of rav1 mutants can be rescued by up-regulation of the lag1 gene which encodes a homologue of lac1, whereas overexpression of either lac1 or lag1 confers multidrug resistance on wild-type cells. These data suggest that changing the amount of ceramide synthase activity in cells can influence innate drug resistance. The function of Rav1 appears to be conserved, as we show that SpRav1 is part of a RAVE-like complex in fission yeast and that loss of rav1 results in defects in vacuolar (H(+))-ATPase activity. Thus, we conclude that loss of normal V-ATPase function results in an increased sensitivity of Schizosaccharomyces pombe cells to drugs. The rav1 and lac1 genes are conserved in both higher eukaryotes and various pathogenic fungi. Thus, our data could provide the basis for strategies to sensitize tumor cells or drug-resistant pathogenic fungi to drugs.
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Affiliation(s)
- Keren Dawson
- Paterson Institute for Cancer Research, University of Manchester, Wilmslow Road, Manchester M20 4BX, United Kingdom
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8
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A novel immunodetection screen for vacuolar defects identifies a unique allele of VPS35 in S. cerevisiae. Mol Cell Biochem 2008; 311:121-36. [PMID: 18224426 DOI: 10.1007/s11010-008-9703-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2007] [Accepted: 01/10/2008] [Indexed: 12/11/2022]
Abstract
The late endosome and vacuole of yeast Saccharomyces cerevisiae are functionally equivalent to the mammalian late endosome and lysosome. The late endosome is the convergence point of the biosynthetic and endocytic trafficking to the vacuole. Here, we describe a novel immunodetection screen to isolate mutants defective in trafficking the soluble hydrolase carboxypeptidase Y (CPY) at the late endosome to vacuole interface (env mutants). Mutants exhibit vacuolar morphology and endocytosis defects as assayed by electron, fluorescent, and nomarski microscopy. In biochemical assays, they internally accumulate p2CPY in a dense membrane compartment lacking vacuolar properties yet display normal secretion phenotypes. The results suggest vacuolar morphology and function defects that are exclusively at the late endosome/vacuole interface. env mutants define five complementation groups. The first gene of the collection to be cloned, ENV1 is allelic to VPS35 whose established function is in retrograde trafficking from late endosome to trans-Golgi network (TGN). Microscopic, biochemical, and growth analyses establish that env1 is distinct from other alleles of VPS35 in vacuolar morphology, growth characteristics, and internal accumulation of p2CPY. Our results indicate that ENV genes may define new gene functions at the late endosome to vacuole interface.
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Mukherjee S, Kallay L, Brett C, Rao R. Mutational analysis of the intramembranous H10 loop of yeast Nhx1 reveals a critical role in ion homoeostasis and vesicle trafficking. Biochem J 2006; 398:97-105. [PMID: 16671892 PMCID: PMC1525006 DOI: 10.1042/bj20060388] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Yeast Nhx1 [Na+(K+)/H+ exchanger 1] is an intracellular Na+(K+)/H+ exchanger, localizing to the late endosome where it is important for ion homoeostasis and vesicle trafficking. Phylogenetic analysis of NHE (Na+/H+ exchanger) sequences has identified orthologous proteins, including HsNHE6 (human NHE6), HsNHE7 and HsNHE9 of unknown physiological role. These appear distinct from well-studied mammalian plasma membrane isoforms (NHE1-NHE5). To explore the differences between plasma membrane and intracellular NHEs and understand the link between ion homoeostasis and vesicle trafficking, we examined the consequence of replacing residues in the intramembranous H10 loop of Nhx1 between transmembrane segments 9 and 10. The critical role for the carboxy group of Glu355 in ion transport is consistent with the invariance of this residue in all NHEs. Surprisingly, residues specifically conserved in the intracellular isoforms (such as Phe357 and Tyr361) could not be replaced with closely similar residues (leucine and phenylalanine) found in the plasma membrane isoforms without loss of function, revealing unexpected side chain specificity. The trafficking phenotypes of all Nhx1 mutants, including hygromycin-sensitivity and missorting of carboxypeptidase Y, were found to directly correlate with pH homoeostasis defects and could be proportionately corrected by titration with weak base. The present study demonstrates the importance of the H10 loop of the NHE family, highlights the differences between plasma membrane and intracellular isoforms and shows that trafficking defects are tightly coupled with pH homoeostasis.
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Affiliation(s)
- Sanchita Mukherjee
- Department of Physiology, The Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205, U.S.A
| | - Laura Kallay
- Department of Physiology, The Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205, U.S.A
| | - Christopher L. Brett
- Department of Physiology, The Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205, U.S.A
| | - Rajini Rao
- Department of Physiology, The Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205, U.S.A
- To whom correspondence should be addressed (email )
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Palmer GE, Kelly MN, Sturtevant JE. The Candida albicans vacuole is required for differentiation and efficient macrophage killing. EUKARYOTIC CELL 2005; 4:1677-86. [PMID: 16215175 PMCID: PMC1265890 DOI: 10.1128/ec.4.10.1677-1686.2005] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Yeast-hypha differentiation is believed to be necessary for the normal progression of Candida albicans infections. The emergence and extension of a germ tube from a parental yeast cell are accompanied by dynamic changes in vacuole size and morphology. Although vacuolar function is required during this process, it is unclear if it is vacuolar expansion or some other vacuolar function that is important. We previously described a C. albicans vps11Delta mutant which lacked a recognizable vacuole compartment and with defects in multiple vacuolar functions. These include sensitivities to stress, reduced proteolytic activities, and severe defects in filamentation. Herein we utilize a partially functional VPS11 allele (vps11hr) to help define which vacuolar functions are required for differentiation and which influence interaction with macrophages. Mutant strains harboring this allele are not osmotically or temperature sensitive and have normal levels of secreted aspartyl protease and carboxypeptidase Y activity but have a fragmented vacuole morphology. Moreover, this mutant is defective in filamentation, suggesting that the major role the vacuole plays in yeast-hypha differentiation may relate directly to its morphology. The results of this study support the hypothesis that vacuole expansion is required during germ tube emergence. Both vps11 mutants were severely attenuated in their ability to kill a macrophage cell line. The viability of the vps11delta mutant was significantly reduced during macrophage interaction compared to that in the control strains, while the vps11hr mutant was unaffected. This implies some vacuolar functions are required for Candida survival within the macrophage, while additional vacuolar functions are required to inflict injury on the macrophage.
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Affiliation(s)
- G E Palmer
- Department of MIP, Louisianna State University Health Sciences Center School of Dentistry, 1100 Florida Ave., Box F8-130, New Orleans, Louisianna 70119, USA.
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Cho SK, Hofmann SL. pdf1, a palmitoyl protein thioesterase 1 Ortholog in Schizosaccharomyces pombe: a yeast model of infantile Batten disease. EUKARYOTIC CELL 2004; 3:302-10. [PMID: 15075260 PMCID: PMC387660 DOI: 10.1128/ec.3.2.302-310.2004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Infantile Batten disease is a severe neurodegenerative storage disorder caused by mutations in the human PPT1 (palmitoyl protein thioesterase 1) gene, which encodes a lysosomal hydrolase that removes fatty acids from lipid-modified proteins. PPT1 has orthologs in many species, including lower organisms and plants, but not in Saccharomyces cerevisiae. The fission yeast Schizosaccharomyces pombe contains a previously uncharacterized open reading frame (SPBC530.12c) that encodes the S. pombe Ppt1p ortholog fused in frame to a second enzyme that is highly similar to a previously cloned mouse dolichol pyrophosphatase (Dolpp1p). In the present study, we characterized this interesting gene (designated here as pdf1, for palmitoyl protein thioesterase-dolichol pyrophosphate phosphatase fusion 1) through deletion of the open reading frame and complementation by plasmids bearing mutations in various regions of the pdf1 sequence. Strains bearing a deletion of the entire pdf1 open reading frame are nonviable and are rescued by a pdf1 expression plasmid. Inactivating mutations in the Dolpp1p domain do not rescue the lethality, whereas mutations in the Ppt1p domain result in cells that are viable but abnormally sensitive to sodium orthovanadate and elevated extracellular pH. The latter phenotypes have been previously associated with class C and class D vacuolar protein sorting (vps) mutants and vacuolar membrane H(+)-ATPase (vma) mutants in S. cerevisiae. Importantly, the Ppt1p-deficient phenotype is complemented by the human PPT1 gene. These results indicate that the function of PPT1 has been widely conserved throughout evolution and that S. pombe may serve as a genetically tractable model for the study of human infantile Batten disease.
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Affiliation(s)
- Steve K Cho
- Department of Internal Medicine and the Hamon Center for Therapeutic Oncology Research, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
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Markovich S, Yekutiel A, Shalit I, Shadkchan Y, Osherov N. Genomic approach to identification of mutations affecting caspofungin susceptibility in Saccharomyces cerevisiae. Antimicrob Agents Chemother 2004; 48:3871-6. [PMID: 15388447 PMCID: PMC521896 DOI: 10.1128/aac.48.10.3871-3876.2004] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The antifungal agent caspofungin (CAS) specifically interferes with glucan synthesis and cell wall formation. To further study the cellular processes affected by CAS, we analyzed a Saccharomyces cerevisiae mutant collection (4,787 individual knockout mutations) to identify new genes affecting susceptibility to the drug. This collection was screened for increased CAS sensitivity (CAS-IS) or increased CAS resistance (CAS-IR). MICs were determined by the broth microdilution method. Disruption of 20 genes led to CAS-IS (four- to eightfold reductions in the MIC). Eleven of the 20 genes are involved in cell wall and membrane function, notably in the protein kinase C (PKC) integrity pathway (MID2, FKS1, SMI1, and BCK1), chitin and mannan biosynthesis (CHS3, CHS4, CHS7, and MNN10), and ergosterol biosynthesis (ERG5 and ERG6). Four of the 20 genes (TPO1, VPS65, VPS25, and CHC1) are involved in vacuole and transport functions, 3 of the 20 genes (CCR4, POP2, and NPL3) are involved in the control of transcription, and 2 of the 20 genes are of unknown function. Disruption of nine additional genes led to CAS-IR (a fourfold increase of MIC). Five of these nine genes (SLG1, ERG3, VRP1, CSG2, and CKA2) are involved in cell wall function and signal transduction, and two of the nine genes (VPS67 and SAC2) are involved in vacuole function. To assess the specificity of susceptibility to CAS, the MICs of amphotericin B, fluconazole, flucytosine, and calcofluor for the strains were tested. Seven of 20 CAS-IS strains (with disruption of FKS1, SMI1, BCK1, CHS4, ERG5, TPO1, and ILM1) and 1 of 9 CAS-IR strains (with disruption of SLG1) demonstrated selective susceptibility to CAS. To further explore the importance of PKC in CAS susceptibility, the activity of the PKC inhibitor staurosporine in combination with CAS was tested against eight Aspergillus clinical isolates by the microdilution assay. Synergistic or synergistic-to-additive activities were found against all eight isolates by use of both MIC and minimum effective concentration endpoints.
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Affiliation(s)
- Sarit Markovich
- Department of Human Microbiology, Sackler School of Medicine, Tel-Aviv University, Ramat-Aviv 69978, Tel-Aviv, Israel
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13
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Abstract
The vacuolar H+-ATPase (V-ATPase) is one of the most fundamental enzymes in nature. It functions in almost every eukaryotic cell and energizes a wide variety of organelles and membranes. V-ATPase has a structure and mechanism of action similar to F-ATPase and several of their subunits probably evolved from common ancestors. In eukaryotic cells, F-ATPase is confined to the semiautonomous organelles, chloroplasts and mitochondria, which contain their own genes that encode some of the F-ATPase subunits. In contrast to F-ATPases, whose primary function in eukaryotic cells is to form ATP at the expense of the protonmotive force (pmf), V-ATPases function exclusively as ATP-dependent proton pumps. The pmf generated by V-ATPases in organelles and membranes of eukaryotic cells is utilized as a driving force for numerous secondary transport processes. It was the survival of the yeast mutant without the active enzyme and yeast genetics that allowed the identification of genuine subunits of the V-ATPase. It also revealed special properties of individual subunits, factors that are involved in the enzyme's biogenesis and assembly, as well as the involvement of V-ATPase in the secretory pathway, endocytosis, and respiration. It may be the insect V-ATPase that unconventionally resides in the plasma membrane of their midgut, that will give the first structure resolution of this complex.
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Affiliation(s)
- Nathan Nelson
- Department of Biochemistry, The George S. Wise Faculty of Life Sciences, Tel Aviv University, 69978 Tel Aviv Israel.
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Parsons AB, Brost RL, Ding H, Li Z, Zhang C, Sheikh B, Brown GW, Kane PM, Hughes TR, Boone C. Integration of chemical-genetic and genetic interaction data links bioactive compounds to cellular target pathways. Nat Biotechnol 2003; 22:62-9. [PMID: 14661025 DOI: 10.1038/nbt919] [Citation(s) in RCA: 481] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2003] [Accepted: 10/29/2003] [Indexed: 01/17/2023]
Abstract
Bioactive compounds can be valuable research tools and drug leads, but it is often difficult to identify their mechanism of action or cellular target. Here we investigate the potential for integration of chemical-genetic and genetic interaction data to reveal information about the pathways and targets of inhibitory compounds. Taking advantage of the existing complete set of yeast haploid deletion mutants, we generated drug-hypersensitivity (chemical-genetic) profiles for 12 compounds. In addition to a set of compound-specific interactions, the chemical-genetic profiles identified a large group of genes required for multidrug resistance. In particular, yeast mutants lacking a functional vacuolar H(+)-ATPase show multidrug sensitivity, a phenomenon that may be conserved in mammalian cells. By filtering chemical-genetic profiles for the multidrug-resistant genes and then clustering the compound-specific profiles with a compendium of large-scale genetic interaction profiles, we were able to identify target pathways or proteins. This method thus provides a powerful means for inferring mechanism of action.
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Affiliation(s)
- Ainslie B Parsons
- Department of Molecular and Medical Genetics, University of Toronto, Toronto, Ontario M5G 1L6, Canada
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15
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Chavan M, Rekowicz M, Lennarz W. Insight into Functional Aspects of Stt3p, a Subunit of the Oligosaccharyl Transferase. J Biol Chem 2003; 278:51441-7. [PMID: 14530272 DOI: 10.1074/jbc.m310456200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Over a decade ago, the gene STT3 was identified in a staurosporine and temperature sensitivity screen of yeast. Subsequently the product of this gene was shown to be a subunit of the endoplasmic reticulum-localized oligosaccharyl transferase (OT) complex. Although stt3 mutants are known to be staurosporine-sensitive, we found that mutants of other OT subunits (except ost4 Delta) are staurosporine-resistant, which indicates that this phenotype of stt3 mutants is not simply a consequence of their defect in glycosylation, as previously speculated. Staurosporine sensitivity was found to be an allele-specific phenotype restricted to cells harboring mutations in highly conserved residues in the N-terminal domain of the STT3 protein. Cells bearing mutations in one of the cytosolic-oriented loops (amino acids 158-168) in the N terminus of Stt3p were found to be specifically susceptible to staurosporine. Staurosporine is a specific inhibitor of Pkc1p, and a genetic link had previously been suggested between PKC1 and STT3. It is known that overexpression of PKC1 suppresses the staurosporine sensitivity of the stt3 mutants in an allele-specific manner, which is typical of mutants of Pkc1p cascade. It has been shown that the pkc1 null mutant exhibits lowered OT activity. Our results combined with these previous observations indicate that the N-terminal domain of Stt3p may interact with members of the Pkc1p cascade and consequently mutations in this domain result in staurosporine sensitivity. We further speculate that the Pkc1p regulates OT activity through the N-terminal domain of Stt3p, the C-terminal domain of which possesses the recognition and/or catalytic site of the OT complex.
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Affiliation(s)
- Manasi Chavan
- Department of Biochemistry and Cell Biology, State University of New York, Stony Brook, New York 11794, USA
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16
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Ali R, Brett CL, Mukherjee S, Rao R. Inhibition of sodium/proton exchange by a Rab-GTPase-activating protein regulates endosomal traffic in yeast. J Biol Chem 2003; 279:4498-506. [PMID: 14610088 DOI: 10.1074/jbc.m307446200] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Endosomal Na+/H+ exchangers are important for salt and osmotolerance, vacuolar pH regulation, and endosomal trafficking. We show that the C terminus of yeast Nhx1 interacts with Gyp6, a GTPase-activating protein for the Ypt/Rab family of GTPases, and that Gyp6 colocalizes with Nhx1 in the endosomal/prevacuolar compartment (PVC). The gyp6 null mutant exhibits novel phenotypes consistent with loss of negative regulation of Nhx1, including increased tolerance to hygromycin, increased vacuolar pH, and decreased plasma membrane potential. In contrast, overexpression of Gyp6 increases sensitivity to hygromycin, decreases vacuolar pH, and results in a slight missorting of vacuolar carboxypeptidase Y to the cell surface. We conclude that Gyp6 is a negative regulator of Nhx1-dependent trafficking out of the PVC. Taken together with its GTPase-activating protein-dependent role as a negative regulator of Ypt6-mediated retrograde traffic to the Golgi, we propose that Gyp6 coordinates upstream and downstream events in the PVC to Golgi pathway. Our findings provide a possible molecular link between intraendosomal pH and regulation of vesicular trafficking.
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Affiliation(s)
- Rashid Ali
- Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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Desmoucelles C, Pinson B, Saint-Marc C, Daignan-Fornier B. Screening the yeast "disruptome" for mutants affecting resistance to the immunosuppressive drug, mycophenolic acid. J Biol Chem 2002; 277:27036-44. [PMID: 12016207 DOI: 10.1074/jbc.m111433200] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The immunosuppressive drug mycophenolic acid (MPA) is a potent and specific inhibitor of IMP dehydrogenase, the first committed step of GMP synthesis. A screen for yeast genes affecting MPA sensitivity, when overexpressed, allowed us to identify two genes, IMD2 and TPO1, encoding a homologue of IMP dehydrogenase and a vacuolar pump, respectively. In parallel, 4787 yeast strains, each carrying an identified knock-out mutation, were tested for growth in the presence of MPA, allowing identification of 100 new genes affecting MPA resistance when disrupted. Disturbance of several cellular processes, such as ergosterol biosynthesis, vacuole biogenesis, or glycosylation impaired the natural capacity of yeast to resist MPA, although most of the highly sensitive mutants affected the transcription machinery (19 mutants). Expression of TPO1 and/or IMD2 was strongly affected in 16 such transcription mutants suggesting that low expression of these genes could contribute to MPA sensitivity. Interestingly, the spt3, spt8, and spt20 mutants behaved differently than other Spt-Ada-Gcn5-acetyltransferase (SAGA) mutants. Indeed, in these three mutants, as in previously characterized transcription elongation mutants, IMD2 expression was only affected in the presence of MPA, thus suggesting a possible role for some SAGA subunits in transcription elongation.
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Affiliation(s)
- Christine Desmoucelles
- Institut de Biochimie et Génétique Cellulaires, CNRS UMR 5095, 1 rue Camille Saint-Saens, 33077 Bordeaux Cedex, France
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Perzov N, Padler-Karavani V, Nelson H, Nelson N. Characterization of yeast V-ATPase mutants lacking Vph1p or Stv1p and the effect on endocytosis. J Exp Biol 2002; 205:1209-19. [PMID: 11948198 DOI: 10.1242/jeb.205.9.1209] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARYSubunit a of V-ATPase in the yeast Saccharomyces cerevisiae, in contrast to its other subunits, is encoded by two genes VPH1 and STV1. While disruption of any other gene encoding the V-ATPase subunits results in growth arrest at pH 7.5, null mutants of Vph1p or Stv1p can grow at this pH. We used a polyclonal antibody to yeast Stv1p and a commercially available monoclonal antibody to Vph1p for analysis of yeast membranes by sucrose gradient fractionation, and two different vital dyes to characterize the phenotype of vph1 ▵ and stv1 ▵mutants as compared to the double mutant and the wild-type cells. Immunological assays of sucrose gradient fractions revealed that the amount of Stv1p was elevated in the vph1 ▵ strain, and that vacuoles purified by this method with no detectable endosomal contamination contain an assembled V-ATPase complex, but with much lower activity than the wild type. These results suggest that Stv1p compensates for the loss of Vph1p in the vph1 ▵ strain. LysoSensor Green DND-189 was used as a pH sensor to demonstrate unexpected changes in vacuolar acidification in stv1▵ as the Vph1p-containing V-ATPase complex is commonly considered to acidify the vacuoles. In the vph1 ▵ strain, the dye revealed slight but definite acidification of the vacuole as well. The lipophilic dye FM4-64 was used as an endocytic marker. We show that the null V-ATPase mutants, as well as the vph1 ▵ one, markedly slow down endocytosis of the dye.
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Affiliation(s)
- Natalie Perzov
- Department of Biochemistry, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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Hallstrom TC, Lambert L, Schorling S, Balzi E, Goffeau A, Moye-Rowley WS. Coordinate control of sphingolipid biosynthesis and multidrug resistance in Saccharomyces cerevisiae. J Biol Chem 2001; 276:23674-80. [PMID: 11323424 DOI: 10.1074/jbc.m101568200] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Multiple or pleiotropic drug resistance often occurs in the yeast Saccharomyces cerevisiae through genetic activation of the Cys(6)-Zn(II) transcription factors Pdr1p and Pdr3p. Hyperactive alleles of these proteins cause overproduction of target genes that include drug efflux pumps, which in turn confer high level drug resistance. Here we provide evidence that both Pdr1p and Pdr3p act to regulate production of an enzyme involved in sphingolipid biosynthesis in S. cerevisiae. The last step in formation of the major sphingolipid in the yeast plasma membrane, mannosyldiinositol phosphorylceramide, is catalyzed by the product of the IPT1 gene, inositol phosphotransferase (Ipt1p). Transcription of the IPT1 gene is responsive to changes in activity of Pdr1p and Pdr3p. A single Pdr1p/Pdr3p response element is present in the IPT1 promoter and is required for regulation by these factors. Loss of IPT1 has complex effects on drug resistance of the resulting strain, consistent with an important role for mannosyldiinositol phosphorylceramide in normal plasma membrane function. Direct assay for lipid contents of cells demonstrates that changes in sphingolipid composition correlate with changes in the activity of Pdr3p. These data suggest that Pdr1p and Pdr3p may act to modulate the lipid composition of membranes in S. cerevisiae through activation of sphingolipid biosynthesis along with other target genes.
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Affiliation(s)
- T C Hallstrom
- Department of Physiology and Biophysics, University of Iowa, Iowa City, Iowa 52242, USA
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