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Takayama C, Koga A, Sakamoto R, Arita N, Tani M. Involvement of the mitochondrial retrograde pathway in dihydrosphingosine-induced cytotoxicity in budding yeast. Biochem Biophys Res Commun 2022; 605:63-69. [DOI: 10.1016/j.bbrc.2022.03.061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Revised: 03/09/2022] [Accepted: 03/12/2022] [Indexed: 11/28/2022]
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Proper regulation of inositolphosphorylceramide levels is required for acquirement of low pH resistance in budding yeast. Sci Rep 2020; 10:10792. [PMID: 32612142 PMCID: PMC7329899 DOI: 10.1038/s41598-020-67734-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Accepted: 06/12/2020] [Indexed: 02/04/2023] Open
Abstract
All organisms have stress response systems to protect themselves from various environmental stresses, and regulation of membrane lipids is thought to play an important role in acquirement of stress tolerance. Complex sphingolipids in the yeast Saccharomyces cerevisiae are classified into three types based on differences in the structure of the polar head group, and the compositions and quantities of complex sphingolipids in biomembranes are tightly regulated. In this study, we found that the accumulation of inositol phosphorylceramides (IPCs) due to a defect of mannosylinositol phosphorylceramide biosynthesis (sur1∆ csh1∆), i.e., disruption of the balance of the composition of complex sphingolipids, causes hypersensitivity to low pH conditions (pH 4.0–2.5). Furthermore, screening of suppressor mutations that confer low pH resistance to sur1∆ csh1∆ cells revealed that a change in ergosterol homeostasis at plasma membranes can rescue the hypersensitivity, suggesting the functional relationship between complex sphingolipids and ergosterol under low pH conditions. Under low pH conditions, wild-type yeast cells exhibited decreases in IPC levels, and forced enhancement of the biosynthesis of IPCs causes low pH hypersensitivity. Thus, it was suggested that the accumulation of IPCs is detrimental to yeast under low pH conditions, and downregulation of IPC levels is one of the adaptation mechanisms for low pH conditions.
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Arita N, Sakamoto R, Tani M. Mitochondrial reactive oxygen species-mediated cytotoxicity of intracellularly accumulated dihydrosphingosine in the yeast Saccharomyces cerevisiae. FEBS J 2020; 287:3427-3448. [PMID: 31944552 DOI: 10.1111/febs.15211] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2019] [Revised: 11/20/2019] [Accepted: 01/10/2020] [Indexed: 02/06/2023]
Abstract
In eukaryotic cells, the content of sphingoid long-chain bases (LCBs) is generally much lower than that of complex sphingolipids and ceramides, and the quantitative balance of these metabolites in cells is tightly regulated. In the budding yeast Saccharomyces cerevisiae, it has been demonstrated that exogenously added phytosphingosine (PHS) causes a strong growth defect in tryptophan auxotrophic cells, due to delayed uptake of tryptophan from the culture medium; however, the growth inhibitory effect of dihydrosphingosine (DHS) is less than that of PHS in tryptophan auxotrophic cells. Here, we found that, in tryptophan-prototrophic yeast cells, exogenously added DHS is much more toxic than PHS. Exogenously added DHS is converted to PHS, Cers, or LCB 1-phosphates through the action of sphingolipid C4-hydroxylase, Cer synthases, or LCB kinases, respectively; however, suppression of further metabolism of DHS in cells resulted in an increase in the growth inhibitory activity of exogenously added DHS, indicating that DHS itself is causative of the cytotoxicity. The cytotoxicity of DHS was not mediated by Pkh1/2, Sch9, and Ypk1/2 kinases, intracellular targets of LCBs. DHS treatment caused an increase in mitochondria-derived reactive oxygen species, and the cytotoxic effect of DHS was suppressed by depletion of mitochondrial DNA or antioxidant N-acetylcysteine, but enhanced by deletion of SOD1 and SOD2 encoding superoxide dismutases. Thus, collectively, these results indicated that intracellularly accumulated DHS has mitochondrial reactive oxygen species-mediated cytotoxic activity, which is much more potent than that of PHS.
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Affiliation(s)
- Nobuaki Arita
- Department of Chemistry, Faculty of Sciences, Kyushu University, Nishi-ku, Fukuoka, Japan
| | - Risa Sakamoto
- Department of Chemistry, Faculty of Sciences, Kyushu University, Nishi-ku, Fukuoka, Japan
| | - Motohiro Tani
- Department of Chemistry, Faculty of Sciences, Kyushu University, Nishi-ku, Fukuoka, Japan
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Zahumensky J, Malinsky J. Role of MCC/Eisosome in Fungal Lipid Homeostasis. Biomolecules 2019; 9:E305. [PMID: 31349700 PMCID: PMC6723945 DOI: 10.3390/biom9080305] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Revised: 07/19/2019] [Accepted: 07/22/2019] [Indexed: 12/11/2022] Open
Abstract
One of the best characterized fungal membrane microdomains is the MCC/eisosome. The MCC (membrane compartment of Can1) is an evolutionarily conserved ergosterol-rich plasma membrane domain. It is stabilized on its cytosolic face by the eisosome, a hemitubular protein complex composed of Bin/Amphiphysin/Rvs (BAR) domain-containing Pil1 and Lsp1. These two proteins bind directly to phosphatidylinositol 4,5-bisphosphate and promote the typical furrow-like shape of the microdomain, with highly curved edges and bottom. While some proteins display stable localization in the MCC/eisosome, others enter or leave it under particular conditions, such as misbalance in membrane lipid composition, changes in membrane tension, or availability of specific nutrients. These findings reveal that the MCC/eisosome, a plasma membrane microdomain with distinct morphology and lipid composition, acts as a multifaceted regulator of various cellular processes including metabolic pathways, cellular morphogenesis, signalling cascades, and mRNA decay. In this minireview, we focus on the MCC/eisosome's proposed role in the regulation of lipid metabolism. While the molecular mechanisms of the MCC/eisosome function are not completely understood, the idea of intracellular processes being regulated at the plasma membrane, the foremost barrier exposed to environmental challenges, is truly exciting.
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Affiliation(s)
- Jakub Zahumensky
- Department of Microscopy, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, 14220 Prague, Czech Republic
| | - Jan Malinsky
- Department of Microscopy, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, 14220 Prague, Czech Republic.
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Yamaguchi Y, Katsuki Y, Tanaka S, Kawaguchi R, Denda H, Ikeda T, Funato K, Tani M. Protective role of the HOG pathway against the growth defect caused by impaired biosynthesis of complex sphingolipids in yeast Saccharomyces cerevisiae. Mol Microbiol 2017; 107:363-386. [PMID: 29215176 DOI: 10.1111/mmi.13886] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/23/2017] [Indexed: 02/06/2023]
Abstract
Complex sphingolipids play critical roles in various cellular events in the yeast Saccharomyces cerevisiae. To identify genes that are related to the growth defect caused by disruption of complex sphingolipid biosynthesis, we screened for suppressor mutations and multicopy suppressor genes that confer resistance against repression of AUR1 encoding inositol phosphorylceramide synthase. From the results of this screening, we found that the activation of high-osmolarity glycerol (HOG) pathway is involved in suppression of growth defect caused by impaired biosynthesis of complex sphingolipids. Furthermore, it was found that transcriptional regulation via Msn2, Msn4 and Sko1 is involved in the suppressive effect of the HOG pathway. Lack of the HOG pathway did not enhance the reductions in complex sphingolipid levels or the increase in ceramide level caused by the AUR1 repression, implying that the suppressive effect of the HOG pathway on the growth defect is not attributed to restoration of impaired biosynthesis of complex sphingolipids. On the contrary, the HOG pathway and Msn2/4-mediated transcriptional activation was involved in suppression of aberrant reactive oxygen species accumulation caused by the AUR1 repression. These results indicated that the HOG pathway plays pivotal roles in maintaining cell growth under impaired biosynthesis of complex sphingolipids.
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Affiliation(s)
- Yutaro Yamaguchi
- Department of Chemistry, Faculty of Sciences, Kyushu University, 744, Motooka, Nishi-ku, Fukuoka 819-3905, Japan
| | - Yuka Katsuki
- Department of Chemistry, Faculty of Sciences, Kyushu University, 744, Motooka, Nishi-ku, Fukuoka 819-3905, Japan
| | - Seiya Tanaka
- Department of Chemistry, Faculty of Sciences, Kyushu University, 744, Motooka, Nishi-ku, Fukuoka 819-3905, Japan
| | - Ryotaro Kawaguchi
- Department of Chemistry, Faculty of Sciences, Kyushu University, 744, Motooka, Nishi-ku, Fukuoka 819-3905, Japan
| | - Hiroto Denda
- Department of Biofunctional Science and Technology, Graduate School of Biosphere Science, Hiroshima University, Kagamiyama 1-4-4, Higashi-Hiroshima 739-8528, Japan
| | - Takuma Ikeda
- Department of Biofunctional Science and Technology, Graduate School of Biosphere Science, Hiroshima University, Kagamiyama 1-4-4, Higashi-Hiroshima 739-8528, Japan
| | - Kouichi Funato
- Department of Biofunctional Science and Technology, Graduate School of Biosphere Science, Hiroshima University, Kagamiyama 1-4-4, Higashi-Hiroshima 739-8528, Japan
| | - Motohiro Tani
- Department of Chemistry, Faculty of Sciences, Kyushu University, 744, Motooka, Nishi-ku, Fukuoka 819-3905, Japan
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Makuta H, Obara K, Kihara A. Loop 5 region is important for the activity of the long-chain base transporter Rsb1. J Biochem 2017; 161:207-213. [PMID: 28175317 DOI: 10.1093/jb/mvw059] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Accepted: 09/05/2016] [Indexed: 11/12/2022] Open
Abstract
Intracellular lipid amounts are regulated not only by metabolism but also by efflux. Yeast Rsb1 is the only known transporter/floppase of the sphingolipid components long-chain bases (LCBs). However, even fundamental knowledge about Rsb1, such as important amino acid residues for activity and substrate recognition, still remains unclear. Rsb1 belongs to the Rta1-like family. To date, it has not been determined whether all family members share a common ability to export LCBs. Here, we revealed that within the Rta1-like family, only Rsb1 suppressed the hypersensitivity of the mutant cells lacking LCB 1-phoshate-degrading enzymes, suggesting that LCB-exporting activity is specific to Rsb1. Rsb1 contains a characteristic region (loop 5), which does not exist in other proteins of the Rta1-like family. We found that deletion of this region caused loss of Rsb1 function. Further mutational analysis of loop 5 revealed that the charged amino acid residues E223, D225 and R236 were important for Rsb1 activity. In addition to LCBs, Rsb1 facilitated the export of 1-hexadecanol, but not palmitic acid, which suggests that Rsb1 recognizes the C1 hydroxyl group. Thus, our findings provide an important clue for understanding the molecular mechanism of LCB export.
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Affiliation(s)
- Hiroshi Makuta
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita 12-jo Nishi 6-chome, Kita-ku, Sapporo 060-0812, Japan
| | - Keisuke Obara
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita 12-jo Nishi 6-chome, Kita-ku, Sapporo 060-0812, Japan
| | - Akio Kihara
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita 12-jo Nishi 6-chome, Kita-ku, Sapporo 060-0812, Japan
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Martínez-Montañés F, Schneiter R. Tools for the analysis of metabolic flux through the sphingolipid pathway. Biochimie 2016; 130:76-80. [PMID: 27208414 DOI: 10.1016/j.biochi.2016.05.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 05/13/2016] [Indexed: 01/26/2023]
Abstract
Discerning the complex regulation of the enzymatic steps necessary for sphingolipid biosynthesis is facilitated by the utilization of tracers that allow a time-resolved analysis of the pathway dynamics without affecting the metabolic flux. Different strategies have been used and new tools are continuously being developed to probe the various enzymatic conversions that occur within this complex pathway. Here, we provide a short overview of the divergent fungal and mammalian sphingolipid biosynthetic routes, and of the tracers and methods that are frequently employed to follow the flux of intermediates throughout these pathways.
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Affiliation(s)
| | - Roger Schneiter
- University of Fribourg, Department of Biology, 1700 Fribourg, Switzerland.
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Yamane-Sando Y, Shimobayashi E, Shimobayashi M, Kozutsumi Y, Oka S, Takematsu H. Fpk1/2 kinases regulate cellular sphingoid long-chain base abundance and alter cellular resistance to LCB elevation or depletion. Microbiologyopen 2014; 3:196-212. [PMID: 24510621 PMCID: PMC3996568 DOI: 10.1002/mbo3.160] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 12/10/2013] [Accepted: 01/03/2014] [Indexed: 01/30/2023] Open
Abstract
Sphingolipids are a family of eukaryotic lipids biosynthesized from sphingoid long-chain bases (LCBs). Sphingolipids are an essential class of lipids, as their depletion results in cell death. However, acute LCB supplementation is also toxic; thus, proper cellular LCB levels should be maintained. To characterize the "sphingolipid-signaling intercross," we performed a kinome screening assay in which budding yeast protein kinase-knockout strains were screened for resistance to ISP-1, a potent inhibitor of LCB biosynthesis. Here, one pair of such DIR (deletion-mediated ISP-1 resistance) genes, FPK1 and FPK2, was further characterized. Cellular LCB levels increased in the fpk1/2∆ strain, which was hypersensitive to phytosphingosine (PHS), a major LCB species of yeast cells. Concomitantly, this strain acquired resistance to ISP-1. Fpk1 and Fpk2 were involved in two downstream events; that is, ISP-1 uptake due to aminophospholipid flippase and LCB degradation due to LCB4 expression. RSK3, which belongs to the p90-S6K subfamily, was identified as a functional counterpart of Fpk1/2 in mammalian cells as the RSK3 gene functionally complemented the ISP-1-resistant phenotype of fpk1/2∆ cells.
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Affiliation(s)
- Yukari Yamane-Sando
- Laboratory of Membrane Biochemistry and Biophysics, Graduate School of Biostudies, Kyoto University, 46-29 Yoshida-shimoadachi, Sakyo, Kyoto, 606-8502, Japan
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Yucel EB, Eraslan S, Ulgen KO. The impact of medium acidity on the chronological life span ofSaccharomyces cerevisiae - lipids, signaling cascades, mitochondrial and vacuolar functions. FEBS J 2014; 281:1281-303. [DOI: 10.1111/febs.12705] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2013] [Revised: 12/20/2013] [Accepted: 12/23/2013] [Indexed: 12/18/2022]
Affiliation(s)
- Esra B. Yucel
- Department of Chemical Engineering; Boğaziçi University; Istanbul Turkey
| | - Serpil Eraslan
- Department of Chemical Engineering; Boğaziçi University; Istanbul Turkey
| | - Kutlu O. Ulgen
- Department of Chemical Engineering; Boğaziçi University; Istanbul Turkey
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Sphingosine 1-phosphate is a key metabolite linking sphingolipids to glycerophospholipids. Biochim Biophys Acta Mol Cell Biol Lipids 2013; 1841:766-72. [PMID: 23994042 DOI: 10.1016/j.bbalip.2013.08.014] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Revised: 08/09/2013] [Accepted: 08/13/2013] [Indexed: 12/18/2022]
Abstract
The sphingolipid metabolite sphingosine 1-phosphate (S1P) is a well-known lipid mediator. As a lipid mediator, S1P must be present in extracellular space and bind to its cell surface receptors (S1P1-5). However, most S1P, synthesized intracellularly, is metabolized without being released into extracellular space, in other words, without functioning as a lipid mediator in the vast majority of cells except those supplying plasma and lymph S1P such as blood cells and endothelial cells. Instead, intracellular S1P plays an important role as an intermediate of the sole sphingolipid-to-glycerophospholipid metabolic pathway. The degradation of S1P by S1P lyase is the first irreversible reaction (committed step) of this pathway. This metabolic pathway is conserved in eukaryotes from yeast to human, indicating its much older origin than the function of S1P as a lipid mediator, which is found to be present only in vertebrates and chordates. The sphingolipid-to-glycerophospholipid metabolism takes place ubiquitously in mammalian tissues, and its defect causes an aberration of several tissue functions as well as abnormal lipid metabolism. Although this metabolic pathway has been known for over four decades, only recently the precise reactions and enzymes involved in this pathway have been revealed. This review will focus on the recent advances in our understanding of the sphingolipid metabolic pathway via S1P and its physiological and pathological roles. This article is part of a Special Issue entitled New Frontiers in Sphingolipid Biology.
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Borklu Yucel E, Ulgen KO. Assessment of crosstalks between the Snf1 kinase complex and sphingolipid metabolism in S. cerevisiae via systems biology approaches. MOLECULAR BIOSYSTEMS 2013; 9:2914-31. [DOI: 10.1039/c3mb70248k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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Alvarez-Vasquez F, Riezman H, Hannun YA, Voit EO. Mathematical modeling and validation of the ergosterol pathway in Saccharomyces cerevisiae. PLoS One 2011; 6:e28344. [PMID: 22194828 PMCID: PMC3237449 DOI: 10.1371/journal.pone.0028344] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2011] [Accepted: 11/06/2011] [Indexed: 11/22/2022] Open
Abstract
The de novo biosynthetic machinery for both sphingolipid and ergosterol production in yeast is localized in the endoplasmic reticulum (ER) and Golgi. The interconnections between the two pathways are still poorly understood, but they may be connected in specialized membrane domains, and specific knockouts strongly suggest that both routes have different layers of mutual control and are co-affected by drugs. With the goal of shedding light on the functional integration of the yeast sphingolipid-ergosterol (SL-E) pathway, we constructed a dynamic model of the ergosterol pathway using the guidelines of Biochemical Systems Theory (BST) (Savageau., J. theor. Biol., 25, 365–9, 1969). The resulting model was merged with a previous mathematical model of sphingolipid metabolism in yeast (Alvarez-Vasquez et al., J. theor. Biol., 226, 265–91, 2004; Alvarez-Vasquez et al., Nature433, 425–30, 2005). The S-system format within BST was used for analyses of consistency, stability, and sensitivity of the SL-E model, while the GMA format was used for dynamic simulations and predictions. Model validation was accomplished by comparing predictions from the model with published results on sterol and sterol-ester dynamics in yeast. The validated model was used to predict the metabolomic dynamics of the SL-E pathway after drug treatment. Specifically, we simulated the action of drugs affecting sphingolipids in the endoplasmic reticulum and studied changes in ergosterol associated with microdomains of the plasma membrane (PM).
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Affiliation(s)
- Fernando Alvarez-Vasquez
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina, United States of America.
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Iwaki S, Sano T, Takagi T, Osumi M, Kihara A, Igarashi Y. Intracellular Trafficking Pathway of Yeast Long-chain Base Kinase Lcb4, from Its Synthesis to Its Degradation. J Biol Chem 2007; 282:28485-28492. [PMID: 17686782 DOI: 10.1074/jbc.m701607200] [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: 11/06/2022] Open
Abstract
Sphingoid long-chain base 1-phosphates act as bioactive lipid molecules in eukaryotic cells. In budding yeast, long-chain base 1-phosphates are synthesized mainly by the long-chain base kinase Lcb4. We recently reported that, soon after yeast cells enter into the stationary phase, Lcb4 is rapidly degraded by being delivered to the vacuole in a palmitoylation- and phosphorylation-dependent manner. In this study, we investigated the complete trafficking pathway of Lcb4, from its synthesis to its degradation. After membrane anchoring by palmitoylation at the Golgi apparatus, Lcb4 is delivered to the plasma membrane (PM) through the late Sec pathway and then to the endoplasmic reticulum (ER). The yeast ER consists of a cortical network juxtaposed to the PM (cortical ER) with tubular connections to the nuclear envelope (nuclear ER). Remarkably, the localization of Lcb4 is restricted to the cortical ER. As the cells reach the stationary phase, G(1) cell cycle arrest initiates Lcb4 degradation and its delivery to the vacuole via the Golgi apparatus. The protein transport pathway from the PM to the ER found in this study has not been previously reported. We speculate that this novel pathway is mediated by the PM-ER contact.
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Affiliation(s)
- Soichiro Iwaki
- Laboratory of Biomembrane and Biofunctional Chemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Kita 12-jo, Nishi 6-choume, Kita-ku, Sapporo 060-0812
| | - Takamitsu Sano
- Laboratory of Biomembrane and Biofunctional Chemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Kita 12-jo, Nishi 6-choume, Kita-ku, Sapporo 060-0812
| | - Tomoko Takagi
- Division of Biology, Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902
| | - Masako Osumi
- Laboratory of Electron Microscopy/Open Research Center, Japan Women's University, 2-8-1 Mejirodai, Bunkyo-ku, Tokyo 112-8681; Integrated Imaging Research Support, Villa Royal Hirakawa, 1-7-5, Hirakawacho, Chiyoda-ku Tokyo 102-0093
| | - Akio Kihara
- Laboratory of Biomembrane and Biofunctional Chemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Kita 12-jo, Nishi 6-choume, Kita-ku, Sapporo 060-0812.
| | - Yasuyuki Igarashi
- Laboratory of Biomembrane and Biofunctional Chemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Kita 12-jo, Nishi 6-choume, Kita-ku, Sapporo 060-0812; Laboratory of Biomembrane and Biofunctional Chemistry, Faculty of Advanced Life Sciences, Hokkaido University, Kita 21-jo, Nishi 11-choume, Kita-ku, Sapporo 001-0021, Japan
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Schulz TA, Prinz WA. Sterol transport in yeast and the oxysterol binding protein homologue (OSH) family. Biochim Biophys Acta Mol Cell Biol Lipids 2007; 1771:769-80. [PMID: 17434796 PMCID: PMC2034499 DOI: 10.1016/j.bbalip.2007.03.003] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2006] [Revised: 03/06/2007] [Accepted: 03/07/2007] [Indexed: 12/12/2022]
Abstract
Sterols such as cholesterol are a significant component of eukaryotic cellular membranes, and their unique physical properties influence a wide variety of membrane processes. It is known that the concentration of sterol within the membrane varies widely between organelles, and that the cell actively maintains this distribution through various transport processes. Vesicular pathways such as secretion or endocytosis may account for this traffic, but increasing evidence highlights the importance of nonvesicular routes as well. The structure of an oxysterol-binding protein homologue (OSH) in yeast (Osh4p/Kes1p) has recently been solved, identifying it as a sterol binding protein, and there is evidence consistent with the role of a cytoplasmic, nonvesicular sterol transporter. Yeast have seven such proteins, which appear to have distinct but overlapping functions with regard to maintaining intracellular sterol distribution and homeostasis. Control of sterol distribution can have far-reaching effects on membrane-related functions, and Osh proteins have been implicated in a variety of processes such as secretory vesicle budding from the Golgi and establishment of cell polarity. This review summarizes the current body of knowledge regarding this family and its potential functions, placing it in the context of known and hypothesized pathways of sterol transport in yeast.
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Affiliation(s)
- Timothy A Schulz
- Laboratory of Cell Biochemistry and Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, US Department of Health and Human Services, Bethesda, MD 20892, USA
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15
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Kihara A, Mitsutake S, Mizutani Y, Igarashi Y. Metabolism and biological functions of two phosphorylated sphingolipids, sphingosine 1-phosphate and ceramide 1-phosphate. Prog Lipid Res 2007; 46:126-44. [PMID: 17449104 DOI: 10.1016/j.plipres.2007.03.001] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Sphingolipids are major lipid constituents of the eukaryotic plasma membrane. Without certain sphingolipids, cells and/or embryos cannot survive, indicating that sphingolipids possess important physiological functions that are not substituted for by other lipids. One such role may be signaling. Recent studies have revealed that some sphingolipid metabolites, such as long-chain bases (LCBs; sphingosine (Sph) in mammals), long-chain base 1-phosphates (LCBPs; sphingosine 1-phosphate (S1P) in mammals), ceramide (Cer), and ceramide 1-phosphate (C1P), act as signaling molecules. The addition of phosphate groups to LCB/Sph and Cer generates LCBP/S1P and C1P, respectively. These phospholipids exhibit completely different functions than those of their precursors. In this review, we describe recent advances in understanding the functions of LCBP/S1P and C1P in mammals and in the yeast Saccharomyces cerevisiae. Since LCB/Sph, LCBP/S1P, Cer, and C1P are mutually convertible, regulation of not only the total amount of the each lipid but also of the overall balance in cellular levels is important. Therefore, we describe in detail their metabolic pathways, as well as the genes involved in each reaction.
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Affiliation(s)
- Akio Kihara
- Laboratory of Biomembrane and Biofunctional Chemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Nishi 6-Choume, Sapporo, Japan.
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16
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Souza CM, Pichler H. Lipid requirements for endocytosis in yeast. Biochim Biophys Acta Mol Cell Biol Lipids 2007; 1771:442-54. [PMID: 16997624 DOI: 10.1016/j.bbalip.2006.08.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2006] [Revised: 08/10/2006] [Accepted: 08/10/2006] [Indexed: 01/19/2023]
Abstract
Endocytosis is, besides secretion, the most prominent membrane transport pathway in eukaryotic cells. In membrane transport, defined areas of the donor membranes engulf solutes of the compartment they are bordering and bud off with the aid of coat proteins to form vesicles. These transport vehicles are guided along cytoskeletal paths, often matured and, finally, fuse to the acceptor membrane they are targeted to. Lipids and proteins are equally important components in membrane transport pathways. Not only are they the structural units of membranes and vesicles, but both classes of molecules also participate actively in membrane transport processes. Whereas proteins form the cytoskeleton and vesicle coats, confer signals and constitute attachment points for membrane-membrane interaction, lipids modulate the flexibility of bilayers, carry protein recognition sites and confer signals themselves. Over the last decade it has been realized that all classes of bilayer lipids, glycerophospholipids, sphingolipids and sterols, actively contribute to functional membrane transport, in particular to endocytosis. Thus, abnormal bilayer lipid metabolism leads to endocytic defects of different severity. Interestingly, there seems to be a great deal of interdependence and interaction among lipid classes. It will be a challenge to characterize this plenitude of interactions and find out about their impact on cellular processes.
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