1
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Duan HD, Li H. Consensus, controversies, and conundrums of P4-ATPases: The emerging face of eukaryotic lipid flippases. J Biol Chem 2024; 300:107387. [PMID: 38763336 PMCID: PMC11225554 DOI: 10.1016/j.jbc.2024.107387] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Revised: 05/04/2024] [Accepted: 05/07/2024] [Indexed: 05/21/2024] Open
Abstract
The cryo-EM resolution revolution has heralded a new era in our understanding of eukaryotic lipid flippases with a rapidly growing number of high-resolution structures. Flippases belong to the P4 family of ATPases (type IV P-type ATPases) that largely follow the reaction cycle proposed for the more extensively studied cation-transporting P-type ATPases. However, unlike the canonical P-type ATPases, no flippase cargos are transported in the phosphorylation half-reaction. Instead of being released into the intracellular or extracellular milieu, lipid cargos are transported to their destination at the inner leaflet of the membrane. Recent flippase structures have revealed multiple conformational states during the lipid transport cycle. Nonetheless, critical conformational states capturing the lipid cargo "in transit" are still missing. In this review, we highlight the amazing structural advances of these lipid transporters, discuss various perspectives on catalytic and regulatory mechanisms in the literature, and shed light on future directions in further deciphering the detailed molecular mechanisms of lipid flipping.
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Affiliation(s)
- H Diessel Duan
- Department of Structural Biology, Van Andel Institute, Grand Rapids, Michigan, USA.
| | - Huilin Li
- Department of Structural Biology, Van Andel Institute, Grand Rapids, Michigan, USA.
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2
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Bai L, Jain BK, You Q, Duan HD, Takar M, Graham TR, Li H. Structural basis of the P4B ATPase lipid flippase activity. Nat Commun 2021; 12:5963. [PMID: 34645814 PMCID: PMC8514546 DOI: 10.1038/s41467-021-26273-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 09/28/2021] [Indexed: 11/23/2022] Open
Abstract
P4 ATPases are lipid flippases that are phylogenetically grouped into P4A, P4B and P4C clades. The P4A ATPases are heterodimers composed of a catalytic α-subunit and accessory β-subunit, and the structures of several heterodimeric flippases have been reported. The S. cerevisiae Neo1 and its orthologs represent the P4B ATPases, which function as monomeric flippases without a β-subunit. It has been unclear whether monomeric flippases retain the architecture and transport mechanism of the dimeric flippases. Here we report the structure of a P4B ATPase, Neo1, in its E1-ATP, E2P-transition, and E2P states. The structure reveals a conserved architecture as well as highly similar functional intermediate states relative to dimeric flippases. Consistently, structure-guided mutagenesis of residues in the proposed substrate translocation path disrupted Neo1’s ability to establish membrane asymmetry. These observations indicate that evolutionarily distant P4 ATPases use a structurally conserved mechanism for substrate transport. The P4 ATPase lipid flippases play a crucial role in membrane biogenesis. Here the authors report the structure of the monomeric P4B ATPase Neo1 in several states, clarifying the mechanism of substrate transport.
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Affiliation(s)
- Lin Bai
- Department of Biochemistry and Biophysics, School of Basic Medical Sciences, Peking University, Beijing, China.
| | - Bhawik K Jain
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA
| | - Qinglong You
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI, USA
| | - H Diessel Duan
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI, USA
| | - Mehmet Takar
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA
| | - Todd R Graham
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA.
| | - Huilin Li
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI, USA.
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3
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Structural Basis of Substrate-Independent Phosphorylation in a P4-ATPase Lipid Flippase. J Mol Biol 2021; 433:167062. [PMID: 34023399 DOI: 10.1016/j.jmb.2021.167062] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Revised: 05/13/2021] [Accepted: 05/17/2021] [Indexed: 11/21/2022]
Abstract
P4-ATPases define a eukaryotic subfamily of the P-type ATPases, and are responsible for the transverse flip of specific lipids from the extracellular or luminal leaflet to the cytosolic leaflet of cell membranes. The enzymatic cycle of P-type ATPases is divided into autophosphorylation and dephosphorylation half-reactions. Unlike most other P-type ATPases, P4-ATPases transport their substrate during dephosphorylation only, i.e. the phosphorylation half-reaction is not associated with transport. To study the structural basis of the distinct mechanisms of P4-ATPases, we have determined cryo-EM structures of Drs2p-Cdc50p from Saccharomyces cerevisiae covering multiple intermediates of the cycle. We identify several structural motifs specific to Drs2p and P4-ATPases in general that decrease movements and flexibility of domains as compared to other P-type ATPases such as Na+/K+-ATPase or Ca2+-ATPase. These motifs include the linkers that connect the transmembrane region to the actuator (A) domain, which is responsible for dephosphorylation. Additionally, mutation of Tyr380, which interacts with conserved Asp340 of the distinct DGET dephosphorylation loop of P4-ATPases, highlights a functional role of these P4-ATPase specific motifs in the A-domain. Finally, the transmembrane (TM) domain, responsible for transport, also undergoes less extensive conformational changes, which is ensured both by a longer segment connecting TM helix 4 with the phosphorylation site, and possible stabilization by the auxiliary subunit Cdc50p. Collectively these adaptions in P4-ATPases are responsible for phosphorylation becoming transport-independent.
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4
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The transport mechanism of P4 ATPase lipid flippases. Biochem J 2021; 477:3769-3790. [PMID: 33045059 DOI: 10.1042/bcj20200249] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 09/02/2020] [Accepted: 09/16/2020] [Indexed: 12/18/2022]
Abstract
P4 ATPase lipid flippases are ATP-driven transporters that translocate specific lipids from the exoplasmic to the cytosolic leaflet of biological membranes, thus establishing a lipid gradient between the two leaflets that is essential for many cellular processes. While substrate specificity, subcellular and tissue-specific expression, and physiological functions have been assigned to a number of these transporters in several organisms, the mechanism of lipid transport has been a topic of intense debate in the field. The recent publication of a series of structural models based on X-ray crystallography and cryo-EM studies has provided the first glimpse into how P4 ATPases have adapted the transport mechanism used by the cation-pumping family members to accommodate a substrate that is at least an order of magnitude larger than cations.
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5
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Kmeck A, Tancer RJ, Ventura CR, Wiedman GR. Synergies with and Resistance to Membrane-Active Peptides. Antibiotics (Basel) 2020; 9:antibiotics9090620. [PMID: 32961656 PMCID: PMC7559582 DOI: 10.3390/antibiotics9090620] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 09/07/2020] [Accepted: 09/17/2020] [Indexed: 12/12/2022] Open
Abstract
Membrane-active peptides (MAPs) have long been thought of as the key to defeating antimicrobial-resistant microorganisms. Such peptides, however, may not be sufficient alone. In this review, we seek to highlight some of the common pathways for resistance, as well as some avenues for potential synergy. This discussion takes place considering resistance, and/or synergy in the extracellular space, at the membrane, and during interaction, and/or removal. Overall, this review shows that researchers require improved definitions of resistance and a more thorough understanding of MAP-resistance mechanisms. The solution to combating resistance may ultimately come from an understanding of how to harness the power of synergistic drug combinations.
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6
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Rizzo J, Stanchev LD, da Silva VK, Nimrichter L, Pomorski TG, Rodrigues ML. Role of lipid transporters in fungal physiology and pathogenicity. Comput Struct Biotechnol J 2019; 17:1278-1289. [PMID: 31921394 PMCID: PMC6944739 DOI: 10.1016/j.csbj.2019.09.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 08/20/2019] [Accepted: 09/02/2019] [Indexed: 02/08/2023] Open
Abstract
The fungal cell wall and membrane are the most common targets of antifungal agents, but the potential of membrane lipid organization in regulating drug-target interactions has yet to be investigated. Energy-dependent lipid transporters have been recently associated with virulence and drug resistance in many pathogenic fungi. To illustrate this view, we discuss (i) the structural and biological aspects of ATP-driven lipid transporters, comprising P-type ATPases and ATP-binding cassette transporters, (ii) the role of these transporters in fungal physiology and virulence, and (iii) the potential of lipid transporters as targets for the development of novel antifungals. These recent observations indicate that the lipid-trafficking machinery in fungi is a promising target for studies on physiology, pathogenesis and drug development.
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Affiliation(s)
- Juliana Rizzo
- Instituto de Microbiologia Paulo de Góes (IMPG), Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil
| | - Lyubomir Dimitrov Stanchev
- Department of Molecular Biochemistry, Ruhr University Bochum, Faculty of Chemistry and Biochemistry, 44780 Bochum, Germany
- Department of Plant Biology and Biotechnology, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C,Denmark
| | - Vanessa K.A. da Silva
- Programa de Pós-Graduação em Biologia Parasitária do Instituto Oswaldo Cruz (IOC), Fundação Oswaldo Cruz (Fiocruz), Rio de Janeiro, Brazil
| | - Leonardo Nimrichter
- Instituto de Microbiologia Paulo de Góes (IMPG), Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil
| | - Thomas Günther Pomorski
- Department of Molecular Biochemistry, Ruhr University Bochum, Faculty of Chemistry and Biochemistry, 44780 Bochum, Germany
- Department of Plant Biology and Biotechnology, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C,Denmark
| | - Marcio L. Rodrigues
- Instituto de Microbiologia Paulo de Góes (IMPG), Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil
- Instituto Carlos Chagas, Fundação Oswaldo Cruz (Fiocruz), Curitiba, Brazil
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7
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Timcenko M, Lyons JA, Januliene D, Ulstrup JJ, Dieudonné T, Montigny C, Ash MR, Karlsen JL, Boesen T, Kühlbrandt W, Lenoir G, Moeller A, Nissen P. Structure and autoregulation of a P4-ATPase lipid flippase. Nature 2019; 571:366-370. [DOI: 10.1038/s41586-019-1344-7] [Citation(s) in RCA: 95] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 05/28/2019] [Indexed: 02/07/2023]
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8
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Nintemann SJ, Palmgren M, López-Marqués RL. Catch You on the Flip Side: A Critical Review of Flippase Mutant Phenotypes. TRENDS IN PLANT SCIENCE 2019; 24:468-478. [PMID: 30885637 DOI: 10.1016/j.tplants.2019.02.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Revised: 01/24/2019] [Accepted: 02/04/2019] [Indexed: 05/05/2023]
Abstract
Lipid flippases are integral membrane proteins that use ATP hydrolysis to power the generation of phospholipid asymmetry between the two leaflets of biological membranes, a process essential for cell survival. Although the first report of a plant lipid flippase was published in 2000, progress in the field has been slow, partially due to the high level of redundancy in this gene family. However, recently an increasing number of reports have examined the physiological function of lipid flippases, mainly in Arabidopsis thaliana. In this review we aim to summarize recent findings on the physiological relevance of lipid flippases in plant adaptation to a changing environment and caution against misinterpretation of pleiotropic effects in genetic studies of flippases.
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Affiliation(s)
- Sebastian J Nintemann
- Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871, Frederiksberg C, Denmark
| | - Michael Palmgren
- Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871, Frederiksberg C, Denmark
| | - Rosa Laura López-Marqués
- Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871, Frederiksberg C, Denmark; https://plen.ku.dk/english/research/transport_biology/blf/.
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9
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Eising S, Thiele L, Fröhlich F. A systematic approach to identify recycling endocytic cargo depending on the GARP complex. eLife 2019; 8:42837. [PMID: 30694181 PMCID: PMC6374077 DOI: 10.7554/elife.42837] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Accepted: 01/29/2019] [Indexed: 12/14/2022] Open
Abstract
Proteins and lipids of the plasma membrane underlie constant remodeling via a combination of the secretory- and the endocytic pathway. In the yeast endocytic pathway, cargo is sorted for recycling to the plasma membrane or degradation in vacuoles. Previously we have shown a role for the GARP complex in sphingolipid sorting and homeostasis (Fröhlich et al. 2015). However, the majority of cargo sorted in a GARP dependent process remain largely unknown. Here we use auxin induced degradation of GARP combined with mass spectrometry based vacuolar proteomics and lipidomics to show that recycling of two specific groups of proteins, the amino-phospholipid flippases and cell wall synthesis proteins depends on a functional GARP complex. Our results suggest that mis-sorting of flippases and remodeling of the lipid composition are the first occurring defects in GARP mutants. Our assay can be adapted to systematically map cargo of the entire endocytic pathway.
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Affiliation(s)
- Sebastian Eising
- Department of Biology/Chemistry, Molecular Membrane Biology Group, University of Osnabrück, Osnabrück, Germany.,Center of Cellular Nanoanalytics, University of Osnabrück, Osnabrück, Germany
| | - Lisa Thiele
- Department of Biology/Chemistry, Molecular Membrane Biology Group, University of Osnabrück, Osnabrück, Germany.,Center of Cellular Nanoanalytics, University of Osnabrück, Osnabrück, Germany
| | - Florian Fröhlich
- Center of Cellular Nanoanalytics, University of Osnabrück, Osnabrück, Germany
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10
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Mioka T, Fujimura-Kamada K, Mizugaki N, Kishimoto T, Sano T, Nunome H, Williams DE, Andersen RJ, Tanaka K. Phospholipid flippases and Sfk1p, a novel regulator of phospholipid asymmetry, contribute to low permeability of the plasma membrane. Mol Biol Cell 2018. [PMID: 29540528 PMCID: PMC5935070 DOI: 10.1091/mbc.e17-04-0217] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Phospholipid flippase (type 4 P-type ATPase) plays a major role in the generation of phospholipid asymmetry in eukaryotic cell membranes. Loss of Lem3p-Dnf1/2p flippases leads to the exposure of phosphatidylserine (PS) and phosphatidylethanolamine (PE) on the cell surface in yeast, resulting in sensitivity to PS- or PE-binding peptides. We isolated Sfk1p, a conserved membrane protein in the TMEM150/FRAG1/DRAM family, as a multicopy suppressor of this sensitivity. Overexpression of SFK1 decreased PS/PE exposure in lem3Δ mutant cells. Consistent with this, lem3Δ sfk1Δ double mutant cells exposed more PS/PE than the lem3Δ mutant. Sfk1p was previously implicated in the regulation of the phosphatidylinositol-4 kinase Stt4p, but the effect of Sfk1p on PS/PE exposure in lem3Δ was independent of Stt4p. Surprisingly, Sfk1p did not facilitate phospholipid flipping but instead repressed it, even under ATP-depleted conditions. We propose that Sfk1p negatively regulates transbilayer movement of phospholipids irrespective of directions. In addition, we showed that the permeability of the plasma membrane was dramatically elevated in the lem3Δ sfk1Δ double mutant in comparison with the corresponding single mutants. Interestingly, total ergosterol was decreased in the lem3Δ sfk1Δ mutant. Our results suggest that phospholipid asymmetry is required for the maintenance of low plasma membrane permeability.
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Affiliation(s)
- Tetsuo Mioka
- Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University Graduate School of Life Science, Kita-ku, Sapporo 060-0815, Japan
| | - Konomi Fujimura-Kamada
- Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University Graduate School of Life Science, Kita-ku, Sapporo 060-0815, Japan
| | - Nahiro Mizugaki
- Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University Graduate School of Life Science, Kita-ku, Sapporo 060-0815, Japan
| | - Takuma Kishimoto
- Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University Graduate School of Life Science, Kita-ku, Sapporo 060-0815, Japan
| | - Takamitsu Sano
- Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University Graduate School of Life Science, Kita-ku, Sapporo 060-0815, Japan
| | - Hitoshi Nunome
- Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University Graduate School of Life Science, Kita-ku, Sapporo 060-0815, Japan
| | - David E Williams
- Departments of Chemistry and Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
| | - Raymond J Andersen
- Departments of Chemistry and Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
| | - Kazuma Tanaka
- Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University Graduate School of Life Science, Kita-ku, Sapporo 060-0815, Japan
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11
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Segawa K, Kurata S, Nagata S. The CDC50A extracellular domain is required for forming a functional complex with and chaperoning phospholipid flippases to the plasma membrane. J Biol Chem 2017; 293:2172-2182. [PMID: 29276178 DOI: 10.1074/jbc.ra117.000289] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Revised: 12/21/2017] [Indexed: 02/04/2023] Open
Abstract
Flippases are enzymes that translocate phosphatidylserine (PtdSer) and phosphatidylethanolamine (PtdEtn) from the outer to the inner leaflet in the lipid bilayer of the plasma membrane, leading to the asymmetric distribution of aminophospholipids in the membrane. One mammalian phospholipid flippase at the plasma membrane is ATP11C, a type IV P-type ATPase (P4-ATPase) that forms a heterocomplex with the transmembrane protein CDC50A. However, the structural features in CDC50A that support the function of ATP11C and other P4-ATPases have not been characterized. Here, using error-prone PCR-mediated mutagenesis of human CDC50A cDNA followed by functional screening and deep sequencing, we identified 14 amino acid residues that affect ATP11C's flippase activity. These residues were all located in CDC50A's extracellular domain and were evolutionarily well-conserved. Most of the mutations decreased CDC50A's ability to chaperone ATP11C and other P4-ATPases to their destinations. The CDC50A mutants failed to form a stable complex with ATP11C and could not induce ATP11C's PtdSer-dependent ATPase activity. Notably, one mutant variant could form a stable complex with ATP11C and transfer ATP11C to the plasma membrane, yet the ATP11C complexed with this CDC50A variant had very weak or little PtdSer- or PtdEtn-dependent ATPase activity. These results indicated that the extracellular domain of CDC50A has important roles both in CDC50A's ability to chaperone ATP11C to the plasma membrane and in inducing ATP11C's ATP hydrolysis-coupled flippase activity.
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Affiliation(s)
- Katsumori Segawa
- From the Laboratory of Biochemistry and Immunology, Immunology Frontier Research Center, Osaka University, Suita, Osaka 565-0871, Japan
| | - Sachiko Kurata
- From the Laboratory of Biochemistry and Immunology, Immunology Frontier Research Center, Osaka University, Suita, Osaka 565-0871, Japan
| | - Shigekazu Nagata
- From the Laboratory of Biochemistry and Immunology, Immunology Frontier Research Center, Osaka University, Suita, Osaka 565-0871, Japan
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12
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Cfs1p, a Novel Membrane Protein in the PQ-Loop Family, Is Involved in Phospholipid Flippase Functions in Yeast. G3-GENES GENOMES GENETICS 2017; 7:179-192. [PMID: 28057802 PMCID: PMC5217107 DOI: 10.1534/g3.116.035238] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Type 4 P-type ATPases (P4-ATPases) function as phospholipid flippases, which translocate phospholipids from the exoplasmic leaflet to the cytoplasmic leaflet of the lipid bilayer, to generate and maintain asymmetric distribution of phospholipids at the plasma membrane and endosomal/Golgi membranes. The budding yeast Saccharomyces cerevisiae has four heteromeric flippases (Drs2p, Dnf1p, Dnf2p, and Dnf3p), associated with the Cdc50p family noncatalytic subunit, and one monomeric flippase, Neo1p. They have been suggested to function in vesicle formation in membrane trafficking pathways, but details of their mechanisms remain to be clarified. Here, to search for novel factors that functionally interact with flippases, we screened transposon insertional mutants for strains that suppressed the cold-sensitive growth defect in the cdc50Δ mutant. We identified a mutation of YMR010W encoding a novel conserved membrane protein that belongs to the PQ-loop family including the cystine transporter cystinosin and the SWEET sugar transporters. We named this gene CFS1 (cdc fifty suppressor 1). GFP-tagged Cfs1p was partially colocalized with Drs2p and Neo1p to endosomal/late Golgi membranes. Interestingly, the cfs1Δ mutation suppressed growth defects in all flippase mutants. Accordingly, defects in membrane trafficking in the flippase mutants were also suppressed. These results suggest that Cfs1p and flippases function antagonistically in membrane trafficking pathways. A growth assay to assess sensitivity to duramycin, a phosphatidylethanolamine (PE)-binding peptide, suggested that the cfs1Δ mutation changed PE asymmetry in the plasma membrane. Cfs1p may thus be a novel regulator of phospholipid asymmetry.
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13
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Pomorski TG, Menon AK. Lipid somersaults: Uncovering the mechanisms of protein-mediated lipid flipping. Prog Lipid Res 2016; 64:69-84. [PMID: 27528189 DOI: 10.1016/j.plipres.2016.08.003] [Citation(s) in RCA: 116] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 08/10/2016] [Indexed: 12/22/2022]
Abstract
Membrane lipids diffuse rapidly in the plane of the membrane but their ability to flip spontaneously across a membrane bilayer is hampered by a significant energy barrier. Thus spontaneous flip-flop of polar lipids across membranes is very slow, even though it must occur rapidly to support diverse aspects of cellular life. Here we discuss the mechanisms by which rapid flip-flop occurs, and what role lipid flipping plays in membrane homeostasis and cell growth. We focus on conceptual aspects, highlighting mechanistic insights from biochemical and in silico experiments, and the recent, ground-breaking identification of a number of lipid scramblases.
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Affiliation(s)
- Thomas Günther Pomorski
- Faculty of Chemistry and Biochemistry, Molecular Biochemistry, Ruhr University Bochum, Universitätstrasse 150, D-44780 Bochum, Germany; Centre for Membrane Pumps in Cells and Disease-PUMPKIN, Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg C, Denmark.
| | - Anant K Menon
- Department of Biochemistry, Weill Cornell Medical College, 1300 York Avenue, New York, NY 10065, USA.
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14
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Costa SR, Marek M, Axelsen KB, Theorin L, Pomorski TG, López-Marqués RL. Role of post-translational modifications at the β-subunit ectodomain in complex association with a promiscuous plant P4-ATPase. Biochem J 2016; 473:1605-15. [PMID: 27048590 PMCID: PMC4888458 DOI: 10.1042/bcj20160207] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Revised: 04/01/2016] [Accepted: 04/04/2016] [Indexed: 12/14/2022]
Abstract
P-type ATPases of subfamily IV (P4-ATPases) constitute a major group of phospholipid flippases that form heteromeric complexes with members of the Cdc50 (cell division control 50) protein family. Some P4-ATPases interact specifically with only one β-subunit isoform, whereas others are promiscuous and can interact with several isoforms. In the present study, we used a site-directed mutagenesis approach to assess the role of post-translational modifications at the plant ALIS5 β-subunit ectodomain in the functionality of the promiscuous plant P4-ATPase ALA2. We identified two N-glycosylated residues, Asn(181) and Asn(231) Whereas mutation of Asn(231) seems to have a small effect on P4-ATPase complex formation, mutation of evolutionarily conserved Asn(181) disrupts interaction between the two subunits. Of the four cysteine residues located in the ALIS5 ectodomain, mutation of Cys(86) and Cys(107) compromises complex association, but the mutant β-subunits still promote complex trafficking and activity to some extent. In contrast, disruption of a conserved disulfide bond between Cys(158) and Cys(172) has no effect on the P4-ATPase complex. Our results demonstrate that post-translational modifications in the β-subunit have different functional roles in different organisms, which may be related to the promiscuity of the P4-ATPase.
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Affiliation(s)
- Sara R Costa
- Department of Plant and Environmental Sciences, Centre for Membrane Pumps in Cells and Disease-PUMPKin, University of Copenhagen, DK-1871, Frederiksberg C, Denmark
| | - Magdalena Marek
- Department of Plant and Environmental Sciences, Centre for Membrane Pumps in Cells and Disease-PUMPKin, University of Copenhagen, DK-1871, Frederiksberg C, Denmark
| | - Kristian B Axelsen
- Department of Plant and Environmental Sciences, Centre for Membrane Pumps in Cells and Disease-PUMPKin, University of Copenhagen, DK-1871, Frederiksberg C, Denmark SIB Swiss Institute of Bioinformatics, CMU, CH-1211, Geneva, Switzerland
| | - Lisa Theorin
- Department of Plant and Environmental Sciences, Centre for Membrane Pumps in Cells and Disease-PUMPKin, University of Copenhagen, DK-1871, Frederiksberg C, Denmark
| | - Thomas G Pomorski
- Department of Plant and Environmental Sciences, Centre for Membrane Pumps in Cells and Disease-PUMPKin, University of Copenhagen, DK-1871, Frederiksberg C, Denmark Faculty of Chemistry and Biochemistry, Department of Molecular Biochemistry, Ruhr University Bochum, Universitätstrasse 150, D-44780 Bochum, Germany
| | - Rosa L López-Marqués
- Department of Plant and Environmental Sciences, Centre for Membrane Pumps in Cells and Disease-PUMPKin, University of Copenhagen, DK-1871, Frederiksberg C, Denmark
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15
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Takar M, Wu Y, Graham TR. The Essential Neo1 Protein from Budding Yeast Plays a Role in Establishing Aminophospholipid Asymmetry of the Plasma Membrane. J Biol Chem 2016; 291:15727-39. [PMID: 27235400 DOI: 10.1074/jbc.m115.686253] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Indexed: 11/06/2022] Open
Abstract
Eukaryotic organisms typically express multiple type IV P-type ATPases (P4-ATPases), which establish plasma membrane asymmetry by flipping specific phospholipids from the exofacial to the cytosolic leaflet. Saccharomyces cerevisiae, for example, expresses five P4-ATPases, including Neo1, Drs2, Dnf1, Dnf2, and Dnf3. Neo1 is thought to be a phospholipid flippase, although there is currently no experimental evidence that Neo1 catalyzes this activity or helps establish membrane asymmetry. Here, we use temperature-conditional alleles (neo1(ts)) to test whether Neo1 deficiency leads to loss of plasma membrane asymmetry. Wild-type (WT) yeast normally restrict most of the phosphatidylserine (PS) and phosphatidylethanolamine (PE) to the inner cytosolic leaflet of the plasma membrane. However, the neo1-1(ts) and neo1-2(ts) mutants display a loss of PS and PE asymmetry at permissive growth temperatures as measured by hypersensitivity to pore-forming toxins that target PS (papuamide A) or PE (duramycin) exposed in the extracellular leaflet. When shifted to a semi-permissive growth temperature, the neo1-1(ts) mutant became extremely hypersensitive to duramycin, although the sensitivity to papuamide A was unchanged, indicating preferential exposure of PE. This loss of asymmetry occurs despite the presence of other flippases that flip PS and/or PE. Even when overexpressed, Drs2 and Dnf1 were unable to correct the loss of asymmetry caused by neo1(ts) However, modest overexpression of Neo1 weakly suppressed loss of membrane asymmetry caused by drs2Δ with a more significant correction of PE asymmetry than PS. These results indicate that Neo1 plays an important role in establishing PS and PE plasma membrane asymmetry in budding yeast.
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Affiliation(s)
- Mehmet Takar
- From the Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235
| | - Yuantai Wu
- From the Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235
| | - Todd R Graham
- From the Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235
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16
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Andersen JP, Vestergaard AL, Mikkelsen SA, Mogensen LS, Chalat M, Molday RS. P4-ATPases as Phospholipid Flippases-Structure, Function, and Enigmas. Front Physiol 2016; 7:275. [PMID: 27458383 PMCID: PMC4937031 DOI: 10.3389/fphys.2016.00275] [Citation(s) in RCA: 205] [Impact Index Per Article: 25.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2016] [Accepted: 06/20/2016] [Indexed: 01/26/2023] Open
Abstract
P4-ATPases comprise a family of P-type ATPases that actively transport or flip phospholipids across cell membranes. This generates and maintains membrane lipid asymmetry, a property essential for a wide variety of cellular processes such as vesicle budding and trafficking, cell signaling, blood coagulation, apoptosis, bile and cholesterol homeostasis, and neuronal cell survival. Some P4-ATPases transport phosphatidylserine and phosphatidylethanolamine across the plasma membrane or intracellular membranes whereas other P4-ATPases are specific for phosphatidylcholine. The importance of P4-ATPases is highlighted by the finding that genetic defects in two P4-ATPases ATP8A2 and ATP8B1 are associated with severe human disorders. Recent studies have provided insight into how P4-ATPases translocate phospholipids across membranes. P4-ATPases form a phosphorylated intermediate at the aspartate of the P-type ATPase signature sequence, and dephosphorylation is activated by the lipid substrate being flipped from the exoplasmic to the cytoplasmic leaflet similar to the activation of dephosphorylation of Na(+)/K(+)-ATPase by exoplasmic K(+). How the phospholipid is translocated can be understood in terms of a peripheral hydrophobic gate pathway between transmembrane helices M1, M3, M4, and M6. This pathway, which partially overlaps with the suggested pathway for migration of Ca(2+) in the opposite direction in the Ca(2+)-ATPase, is wider than the latter, thereby accommodating the phospholipid head group. The head group is propelled along against its concentration gradient with the hydrocarbon chains projecting out into the lipid phase by movement of an isoleucine located at the position corresponding to an ion binding glutamate in the Ca(2+)- and Na(+)/K(+)-ATPases. Hence, the P4-ATPase mechanism is quite similar to the mechanism of these ion pumps, where the glutamate translocates the ions by moving like a pump rod. The accessory subunit CDC50 may be located in close association with the exoplasmic entrance of the suggested pathway, and possibly promotes the binding of the lipid substrate. This review focuses on properties of mammalian and yeast P4-ATPases for which most mechanistic insight is available. However, the structure, function and enigmas associated with mammalian and yeast P4-ATPases most likely extend to P4-ATPases of plants and other organisms.
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Affiliation(s)
| | | | | | | | - Madhavan Chalat
- Department of Biochemistry and Molecular Biology, University of British ColumbiaVancouver, BC, Canada
| | - Robert S. Molday
- Department of Biochemistry and Molecular Biology, University of British ColumbiaVancouver, BC, Canada
- *Correspondence: Robert S. Molday
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17
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Montigny C, Lyons J, Champeil P, Nissen P, Lenoir G. On the molecular mechanism of flippase- and scramblase-mediated phospholipid transport. Biochim Biophys Acta Mol Cell Biol Lipids 2015; 1861:767-783. [PMID: 26747647 DOI: 10.1016/j.bbalip.2015.12.020] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Revised: 12/20/2015] [Accepted: 12/28/2015] [Indexed: 11/20/2022]
Abstract
Phospholipid flippases are key regulators of transbilayer lipid asymmetry in eukaryotic cell membranes, critical to many trafficking and signaling pathways. P4-ATPases, in particular, are responsible for the uphill transport of phospholipids from the exoplasmic to the cytosolic leaflet of the plasma membrane, as well as membranes of the late secretory/endocytic pathways, thereby establishing transbilayer asymmetry. Recent studies combining cell biology and biochemical approaches have improved our understanding of the path taken by lipids through P4-ATPases. Additionally, identification of several protein families catalyzing phospholipid 'scrambling', i.e. disruption of phospholipid asymmetry through energy-independent bi-directional phospholipid transport, as well as the recent report of the structure of such a scramblase, opens the way to a deeper characterization of their mechanism of action. Here, we discuss the molecular nature of the mechanism by which lipids may 'flip' across membranes, with an emphasis on active lipid transport catalyzed by P4-ATPases. This article is part of a Special Issue entitled: The cellular lipid landscape edited by Tim P. Levine and Anant K. Menon.
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Affiliation(s)
- Cédric Montigny
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette, France
| | - Joseph Lyons
- DANDRITE, Nordic-EMBL Partnership for Molecular Medicine, and PUMPkin, Danish National Research Foundation, Aarhus University, Department of Molecular Biology and Genetics, Gustav Wieds Vej 10C, 8000 Aarhus C, Denmark
| | - Philippe Champeil
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette, France
| | - Poul Nissen
- DANDRITE, Nordic-EMBL Partnership for Molecular Medicine, and PUMPkin, Danish National Research Foundation, Aarhus University, Department of Molecular Biology and Genetics, Gustav Wieds Vej 10C, 8000 Aarhus C, Denmark
| | - Guillaume Lenoir
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette, France.
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18
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Specific mutations in mammalian P4-ATPase ATP8A2 catalytic subunit entail differential glycosylation of the accessory CDC50A subunit. FEBS Lett 2015; 589:3908-14. [PMID: 26592152 DOI: 10.1016/j.febslet.2015.11.031] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Revised: 11/16/2015] [Accepted: 11/16/2015] [Indexed: 12/21/2022]
Abstract
P4-ATPases, or flippases, translocate phospholipids between the two leaflets of eukaryotic biological membranes. They are essential to the physiologically crucial phospholipid asymmetry and involved in severe diseases, but their molecular structure and mechanism are still unresolved. Here, we show that in an extensive mutational alanine screening of the mammalian flippase ATP8A2 catalytic subunit, five mutations stand out by leading to reduced glycosylation of the accessory subunit CDC50A. These mutations may disturb the interaction between the subunits.
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19
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Substrate trajectory through phospholipid-transporting P4-ATPases. Biochem Soc Trans 2015; 42:1367-71. [PMID: 25233416 DOI: 10.1042/bst20140137] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A difference in the lipid composition between the two leaflets of the same membrane is a relatively simple instance of lipid compositional heterogeneity. The large activation energy barrier for transbilayer movement for some (but not all) membrane lipids creates a regime governed by active transport processes. An early step in eukaryote evolution was the development of a capacity for generating transbilayer compositional heterogeneity far from equilibrium by directly tapping energy from the ATP pool. The mechanism of the P-type ATPases that create lipid asymmetry is well understood in terms of ATP hydrolysis, but the trajectory taken by the phospholipid substrate through the enzyme is a matter of current active research. There are currently three different models for this trajectory, all with support by mutation/activity measurements and analogies with known atomic structures.
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20
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Panatala R, Hennrich H, Holthuis JCM. Inner workings and biological impact of phospholipid flippases. J Cell Sci 2015; 128:2021-32. [PMID: 25918123 DOI: 10.1242/jcs.102715] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The plasma membrane, trans-Golgi network and endosomal system of eukaryotic cells are populated with flippases that hydrolyze ATP to help establish asymmetric phospholipid distributions across the bilayer. Upholding phospholipid asymmetry is vital to a host of cellular processes, including membrane homeostasis, vesicle biogenesis, cell signaling, morphogenesis and migration. Consequently, defining the identity of flippases and their biological impact has been the subject of intense investigations. Recent work has revealed a remarkable degree of kinship between flippases and cation pumps. In this Commentary, we review emerging insights into how flippases work, how their activity is controlled according to cellular demands, and how disrupting flippase activity causes system failure of membrane function, culminating in membrane trafficking defects, aberrant signaling and disease.
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Affiliation(s)
- Radhakrishnan Panatala
- Department of Membrane Enzymology, Bijvoet Center and Institute of Biomembranes, Utrecht University, 3584 Utrecht, The Netherlands Molecular Cell Biology Division, University of Osnabrück, 49076 Osnabrück, Germany
| | - Hanka Hennrich
- Department of Membrane Enzymology, Bijvoet Center and Institute of Biomembranes, Utrecht University, 3584 Utrecht, The Netherlands
| | - Joost C M Holthuis
- Department of Membrane Enzymology, Bijvoet Center and Institute of Biomembranes, Utrecht University, 3584 Utrecht, The Netherlands Molecular Cell Biology Division, University of Osnabrück, 49076 Osnabrück, Germany
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21
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Yamagami K, Yamamoto T, Sakai S, Mioka T, Sano T, Igarashi Y, Tanaka K. Inositol depletion restores vesicle transport in yeast phospholipid flippase mutants. PLoS One 2015; 10:e0120108. [PMID: 25781026 PMCID: PMC4363822 DOI: 10.1371/journal.pone.0120108] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Accepted: 01/19/2015] [Indexed: 12/19/2022] Open
Abstract
In eukaryotic cells, type 4 P-type ATPases function as phospholipid flippases, which translocate phospholipids from the exoplasmic leaflet to the cytoplasmic leaflet of the lipid bilayer. Flippases function in the formation of transport vesicles, but the mechanism remains unknown. Here, we isolate an arrestin-related trafficking adaptor, ART5, as a multicopy suppressor of the growth and endocytic recycling defects of flippase mutants in budding yeast. Consistent with a previous report that Art5p downregulates the inositol transporter Itr1p by endocytosis, we found that flippase mutations were also suppressed by the disruption of ITR1, as well as by depletion of inositol from the culture medium. Interestingly, inositol depletion suppressed the defects in all five flippase mutants. Inositol depletion also partially restored the formation of secretory vesicles in a flippase mutant. Inositol depletion caused changes in lipid composition, including a decrease in phosphatidylinositol and an increase in phosphatidylserine. A reduction in phosphatidylinositol levels caused by partially depleting the phosphatidylinositol synthase Pis1p also suppressed a flippase mutation. These results suggest that inositol depletion changes the lipid composition of the endosomal/TGN membranes, which results in vesicle formation from these membranes in the absence of flippases.
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Affiliation(s)
- Kanako Yamagami
- Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University Graduate School of Life Science, Sapporo, Japan
| | - Takaharu Yamamoto
- Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University Graduate School of Life Science, Sapporo, Japan
| | - Shota Sakai
- Laboratory of Biomembrane and Biofunctional Chemistry, Graduate School of Advanced Life Science, and Frontier Research Center for Post-Genome Science and Technology, Hokkaido University, Sapporo, Japan
| | - Tetsuo Mioka
- Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University Graduate School of Life Science, Sapporo, Japan
| | - Takamitsu Sano
- Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University Graduate School of Life Science, Sapporo, Japan
| | - Yasuyuki Igarashi
- Laboratory of Biomembrane and Biofunctional Chemistry, Graduate School of Advanced Life Science, and Frontier Research Center for Post-Genome Science and Technology, Hokkaido University, Sapporo, Japan
| | - Kazuma Tanaka
- Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University Graduate School of Life Science, Sapporo, Japan
- * E-mail:
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22
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P4-ATPases: lipid flippases in cell membranes. Pflugers Arch 2015; 466:1227-40. [PMID: 24077738 PMCID: PMC4062807 DOI: 10.1007/s00424-013-1363-4] [Citation(s) in RCA: 88] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2013] [Revised: 09/11/2013] [Accepted: 09/11/2013] [Indexed: 12/13/2022]
Abstract
Cellular membranes, notably eukaryotic plasma membranes, are equipped with special proteins that actively translocate lipids from one leaflet to the other and thereby help generate membrane lipid asymmetry. Among these ATP-driven transporters, the P4 subfamily of P-type ATPases (P4-ATPases) comprises lipid flippases that catalyze the translocation of phospholipids from the exoplasmic to the cytosolic leaflet of cell membranes. While initially characterized as aminophospholipid translocases, recent studies of individual P4-ATPase family members from fungi, plants, and animals show that P4-ATPases differ in their substrate specificities and mediate transport of a broader range of lipid substrates, including lysophospholipids and synthetic alkylphospholipids. At the same time, the cellular processes known to be directly or indirectly affected by this class of transporters have expanded to include the regulation of membrane traffic, cytoskeletal dynamics, cell division, lipid metabolism, and lipid signaling. In this review, we will summarize the basic features of P4-ATPases and the physiological implications of their lipid transport activity in the cell.
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23
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Mioka T, Fujimura-Kamada K, Tanaka K. Asymmetric distribution of phosphatidylserine is generated in the absence of phospholipid flippases in Saccharomyces cerevisiae. Microbiologyopen 2014; 3:803-21. [PMID: 25220349 PMCID: PMC4234269 DOI: 10.1002/mbo3.211] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Revised: 07/23/2014] [Accepted: 08/01/2014] [Indexed: 11/20/2022] Open
Abstract
In eukaryotic cells, phosphatidylserine (PS) is predominantly located in the cytosolic leaflet of the plasma membrane; this asymmetry is generated by an unknown mechanism. In this study, we used the PS-specific probe mRFP-Lact-C2 to investigate the possible involvement of type 4 P-type ATPases, also called phospholipid flippases, in the generation of this asymmetry in Saccharomyces cerevisiae. PS was not found in the trans-Golgi Network in wild-type cells, but it became exposed when vesicle formation was compromised in the sec7 mutant, and it was also exposed on secretory vesicles (SVs), as reported previously. However, flippase mutations did not reduce the exposure of PS in either case, even at low levels that would only be detectable by quantitative analysis of mRFP-Lact-C2 fluorescence in isolated SVs. Furthermore, no reduction in the PS level was observed in a mutant with multiple flippase mutations. Because PS was not exposed in a mutant that accumulates ER or cis/medial-Golgi membranes, Golgi maturation seems to be a prerequisite for PS translocation. Our results suggest that an unknown mechanism, possibly a protein with flippase-like activity, acts in conjunction with known flippases to regulate PS translocation.
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Affiliation(s)
- Tetsuo Mioka
- Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University Graduate School of Life Science, N15 W7, Kita-ku, Sapporo, 060-0815, Japan
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24
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Functional role of evolutionarily highly conserved residues, N-glycosylation level and domains of the Leishmania miltefosine transporter-Cdc50 subunit. Biochem J 2014; 459:83-94. [PMID: 24447089 DOI: 10.1042/bj20131318] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Cdc50 (cell-cycle control protein 50) is a family of conserved eukaryotic proteins that interact with P4-ATPases (phospholipid translocases). Cdc50 association is essential for the endoplasmic reticulum export of P4-ATPases and proper translocase activity. In the present study, we analysed the role of Leishmania infantum LiRos3, the Cdc50 subunit of the P4-ATPase MLF (miltefosine) transporter [LiMT (L. infantum MLF transporter)], on trafficking and complex functionality using site-directed mutagenesis and domain substitution. We identified 22 invariant residues in the Cdc50 proteins from L. infantum, human and yeast. Seven of these residues are found in the extracellular domain of LiRos3, the conservation of which is critical for ensuring that LiMT arrives at the plasma membrane. The substitution of other invariant residues affects complex trafficking to a lesser extent. Furthermore, invariant residues located in the N-terminal cytosolic domain play a role in the transport activity. Partial N-glycosylation of LiRos3 reduces MLF transport and total N-deglycosylation completely inhibits LiMT trafficking to the plasma membrane. One of the N-glycosylation residues is invariant along the Cdc50 family. The transmembrane and exoplasmic domains are not interchangeable with the other two L. infantum Cdc50 proteins to maintain LiMT interaction. Taken together, these findings indicate that both invariant and N-glycosylated residues of LiRos3 are implicated in LiMT trafficking and transport activity.
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25
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Coleman JA, Quazi F, Molday RS. Mammalian P4-ATPases and ABC transporters and their role in phospholipid transport. Biochim Biophys Acta Mol Cell Biol Lipids 2012; 1831:555-74. [PMID: 23103747 DOI: 10.1016/j.bbalip.2012.10.006] [Citation(s) in RCA: 102] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Revised: 10/16/2012] [Accepted: 10/18/2012] [Indexed: 02/08/2023]
Abstract
Transport of phospholipids across cell membranes plays a key role in a wide variety of biological processes. These include membrane biosynthesis, generation and maintenance of membrane asymmetry, cell and organelle shape determination, phagocytosis, vesicle trafficking, blood coagulation, lipid homeostasis, regulation of membrane protein function, apoptosis, etc. P(4)-ATPases and ATP binding cassette (ABC) transporters are the two principal classes of membrane proteins that actively transport phospholipids across cellular membranes. P(4)-ATPases utilize the energy from ATP hydrolysis to flip aminophospholipids from the exocytoplasmic (extracellular/lumen) to the cytoplasmic leaflet of cell membranes generating membrane lipid asymmetry and lipid imbalance which can induce membrane curvature. Many ABC transporters play crucial roles in lipid homeostasis by actively transporting phospholipids from the cytoplasmic to the exocytoplasmic leaflet of cell membranes or exporting phospholipids to protein acceptors or micelles. Recent studies indicate that some ABC proteins can also transport phospholipids in the opposite direction. The importance of P(4)-ATPases and ABC transporters is evident from the findings that mutations in many of these transporters are responsible for severe human genetic diseases linked to defective phospholipid transport. This article is part of a Special Issue entitled Phospholipids and Phospholipid Metabolism.
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Affiliation(s)
- Jonathan A Coleman
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, B.C., Canada
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26
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Stone A, Chau C, Eaton C, Foran E, Kapur M, Prevatt E, Belkin N, Kerr D, Kohlin T, Williamson P. Biochemical characterization of P4-ATPase mutations identified in patients with progressive familial intrahepatic cholestasis. J Biol Chem 2012; 287:41139-51. [PMID: 23060447 DOI: 10.1074/jbc.m112.413039] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Mutations in the P4-ATPase ATP8B1 cause the inherited liver disease progressive familial intrahepatic cholestasis. Several of these mutations are located in conserved regions of the transmembrane domain associated with substrate binding and transport. Assays for P4-ATPase-mediated transport in living yeast cells were developed and used to characterize the specificity and kinetic parameters of this transport. Progressive familial intrahepatic cholestasis mutations were introduced into the yeast plasma membrane P4-ATPase Dnf2p, and the effect of these mutations on its catalysis of phospholipid transport were determined. The results of these measurements have implications for the basis of the disease and for the mechanism of phospholipid transit through the enzyme during the reaction cycle.
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Affiliation(s)
- Alex Stone
- Department of Biology, Amherst College, Amherst, Massachusetts 01002, USA
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