1
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Overduin M, Bhat R. Recognition and remodeling of endosomal zones by sorting nexins. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2024; 1866:184305. [PMID: 38408696 DOI: 10.1016/j.bbamem.2024.184305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2023] [Revised: 02/05/2024] [Accepted: 02/18/2024] [Indexed: 02/28/2024]
Abstract
The proteolipid code determines how cytosolic proteins find and remodel membrane surfaces. Here, we investigate how this process works with sorting nexins Snx1 and Snx3. Both proteins form sorting machines by recognizing membrane zones enriched in phosphatidylinositol 3-phosphate (PI3P), phosphatidylserine (PS) and cholesterol. This co-localized combination forms a unique "lipid codon" or lipidon that we propose is responsible for endosomal targeting, as revealed by structures and interactions of their PX domain-based readers. We outline a membrane recognition and remodeling mechanism for Snx1 and Snx3 involving this code element alongside transmembrane pH gradients, dipole moment-guided docking and specific protein-protein interactions. This generates an initial membrane-protein assembly (memtein) that then recruits retromer and additional PX proteins to recruit cell surface receptors for sorting to the trans-Golgi network (TGN), lysosome and plasma membranes. Post-translational modification (PTM) networks appear to regulate how the sorting machines form and operate at each level. The commonalities and differences between these sorting nexins show how the proteolipid code orchestrates parallel flows of molecular information from ribosome emergence to organelle genesis, and illuminates a universally applicable model of the membrane.
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Affiliation(s)
- Michael Overduin
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada.
| | - Rakesh Bhat
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
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2
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Lysine acetylation regulates the interaction between proteins and membranes. Nat Commun 2021; 12:6466. [PMID: 34753925 PMCID: PMC8578602 DOI: 10.1038/s41467-021-26657-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Accepted: 09/30/2021] [Indexed: 11/23/2022] Open
Abstract
Lysine acetylation regulates the function of soluble proteins in vivo, yet it remains largely unexplored whether lysine acetylation regulates membrane protein function. Here, we use bioinformatics, biophysical analysis of recombinant proteins, live-cell fluorescent imaging and genetic manipulation of Drosophila to explore lysine acetylation in peripheral membrane proteins. Analysis of 50 peripheral membrane proteins harboring BAR, PX, C2, or EHD membrane-binding domains reveals that lysine acetylation predominates in membrane-interaction regions. Acetylation and acetylation-mimicking mutations in three test proteins, amphiphysin, EHD2, and synaptotagmin1, strongly reduce membrane binding affinity, attenuate membrane remodeling in vitro and alter subcellular localization. This effect is likely due to the loss of positive charge, which weakens interactions with negatively charged membranes. In Drosophila, acetylation-mimicking mutations of amphiphysin cause severe disruption of T-tubule organization and yield a flightless phenotype. Our data provide mechanistic insights into how lysine acetylation regulates membrane protein function, potentially impacting a plethora of membrane-related processes. Lysine acetylation regulates the function of soluble proteins in vivo, yet it remains largely unexplored whether lysine acetylation regulates the function of membrane proteins. Here, the authors map lysine acetylation predominantly in membrane-interaction regions in peripheral membrane proteins and show with three candidate proteins how lysine acetylation is a regulator of membrane protein function.
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3
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Kervin TA, Overduin M. Regulation of the Phosphoinositide Code by Phosphorylation of Membrane Readers. Cells 2021; 10:cells10051205. [PMID: 34069055 PMCID: PMC8156045 DOI: 10.3390/cells10051205] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 05/07/2021] [Accepted: 05/09/2021] [Indexed: 02/07/2023] Open
Abstract
The genetic code that dictates how nucleic acids are translated into proteins is well known, however, the code through which proteins recognize membranes remains mysterious. In eukaryotes, this code is mediated by hundreds of membrane readers that recognize unique phosphatidylinositol phosphates (PIPs), which demark organelles to initiate localized trafficking and signaling events. The only superfamily which specifically detects all seven PIPs are the Phox homology (PX) domains. Here, we reveal that throughout evolution, these readers are universally regulated by the phosphorylation of their PIP binding surfaces based on our analysis of existing and modelled protein structures and phosphoproteomic databases. These PIP-stops control the selective targeting of proteins to organelles and are shown to be key determinants of high-fidelity PIP recognition. The protein kinases responsible include prominent cancer targets, underscoring the critical role of regulated membrane readership.
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Tao K, Waletich JR, Arredondo F, Tyler BM. Manipulating Endoplasmic Reticulum-Plasma Membrane Tethering in Plants Through Fluorescent Protein Complementation. FRONTIERS IN PLANT SCIENCE 2019; 10:635. [PMID: 31191568 PMCID: PMC6547045 DOI: 10.3389/fpls.2019.00635] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 04/26/2019] [Indexed: 05/21/2023]
Abstract
The bimolecular fluorescence complementation (BiFC) assay has been widely used to examine interactions between integral and peripheral proteins within putative plasma membrane (PM) microdomains. In the course of using BiFC assays to examine the co-localization of plasma membrane (PM) targeted receptor-like kinases (RLKs), such as FLS2, with PM micro-domain proteins such as remorins, we unexpectedly observed heterogeneous distribution patterns of fluorescence on the PM of Nicotiana benthamiana leaf cortical cells. These patterns appeared to co-localize with the endoplasmic reticulum (ER) and with ER-PM contact sites, and closely resembled patterns caused by over-expression of the ER-PM tether protein Synaptotagmin1 (SYT1). Using domain swap experiments with SYT1, we inferred that non-specific dimerization between FLS2-VenusN and VenusC-StRem1.3 could create artificial ER-PM tether proteins analogous to SYT1. The same patterns of ER-PM tethering were produced when a representative set of integral membrane proteins were partnered in BiFC complexes with PM-targeted peripheral membrane proteins, including PtdIns(4)P-binding proteins. We inferred that spontaneous formation of mature fluorescent proteins caused the BiFC complexes to trap the integral membrane proteins in the ER during delivery to the PM, producing a PM-ER tether. This phenomenon could be a useful tool to deliberately manipulate ER-PM tethering or to test protein membrane localization. However, this study also highlights the risk of using the BiFC assay to study membrane protein interactions in plants, due to the possibility of alterations in cellular structures and membrane organization, or misinterpretation of protein-protein interactions. A number of published studies using this approach may therefore need to be revisited.
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Affiliation(s)
- Kai Tao
- Molecular and Cellular Biology Program, Oregon State University, Corvallis, OR, United States
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR, United States
| | - Justin R. Waletich
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR, United States
| | - Felipe Arredondo
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR, United States
| | - Brett M. Tyler
- Molecular and Cellular Biology Program, Oregon State University, Corvallis, OR, United States
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR, United States
- Center for Genome Research and Biocomputing, Oregon State University, Corvallis, OR, United States
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5
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Chandra M, Chin YKY, Mas C, Feathers JR, Paul B, Datta S, Chen KE, Jia X, Yang Z, Norwood SJ, Mohanty B, Bugarcic A, Teasdale RD, Henne WM, Mobli M, Collins BM. Classification of the human phox homology (PX) domains based on their phosphoinositide binding specificities. Nat Commun 2019; 10:1528. [PMID: 30948714 PMCID: PMC6449406 DOI: 10.1038/s41467-019-09355-y] [Citation(s) in RCA: 90] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Accepted: 02/21/2019] [Indexed: 01/05/2023] Open
Abstract
Phox homology (PX) domains are membrane interacting domains that bind to phosphatidylinositol phospholipids or phosphoinositides, markers of organelle identity in the endocytic system. Although many PX domains bind the canonical endosome-enriched lipid PtdIns3P, others interact with alternative phosphoinositides, and a precise understanding of how these specificities arise has remained elusive. Here we systematically screen all human PX domains for their phospholipid preferences using liposome binding assays, biolayer interferometry and isothermal titration calorimetry. These analyses define four distinct classes of human PX domains that either bind specifically to PtdIns3P, non-specifically to various di- and tri-phosphorylated phosphoinositides, bind both PtdIns3P and other phosphoinositides, or associate with none of the lipids tested. A comprehensive evaluation of PX domain structures reveals two distinct binding sites that explain these specificities, providing a basis for defining and predicting the functional membrane interactions of the entire PX domain protein family.
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Affiliation(s)
- Mintu Chandra
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD, 4072, Australia
| | - Yanni K-Y Chin
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD, 4072, Australia
| | - Caroline Mas
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD, 4072, Australia
- Integrated Structural Biology Grenoble, Grenoble, France
| | - J Ryan Feathers
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Blessy Paul
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD, 4072, Australia
| | - Sanchari Datta
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Kai-En Chen
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD, 4072, Australia
| | - Xinying Jia
- Centre for Advanced Imaging and School of Chemistry and Molecular Biology, The University of Queensland, St. Lucia, QLD, 4072, Australia
| | - Zhe Yang
- School of Biomedical Sciences, Faculty of Medicine, The University of Queensland, St. Lucia, QLD, 4072, Australia
| | - Suzanne J Norwood
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD, 4072, Australia
| | - Biswaranjan Mohanty
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, 3052, VIC, Australia
| | - Andrea Bugarcic
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD, 4072, Australia
| | - Rohan D Teasdale
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD, 4072, Australia
- School of Biomedical Sciences, Faculty of Medicine, The University of Queensland, St. Lucia, QLD, 4072, Australia
| | - W Mike Henne
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Mehdi Mobli
- Centre for Advanced Imaging and School of Chemistry and Molecular Biology, The University of Queensland, St. Lucia, QLD, 4072, Australia
| | - Brett M Collins
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD, 4072, Australia.
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6
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Tao K, Waletich JR, Wise H, Arredondo F, Tyler BM. Tethering of Multi-Vesicular Bodies and the Tonoplast to the Plasma Membrane in Plants. FRONTIERS IN PLANT SCIENCE 2019; 10:636. [PMID: 31396242 PMCID: PMC6662526 DOI: 10.3389/fpls.2019.00636] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Accepted: 04/26/2019] [Indexed: 05/05/2023]
Abstract
UNLABELLED Tethering of the plasma membrane (PM) and many organelles to the endoplasmic reticulum (ER) for communication and lipid exchange has been widely reported. However, despite growing interest in multi-vesicular bodies (MVBs) as possible sources of exosomes, tethering of MVBs to the PM has not been reported. Here we show that MVBs and the vacuolar membrane (tonoplast) could be tethered to the PM (PM-MVB/TP tethering) by artificial protein fusions or bimolecular fluorescence complementation (BiFC) complexes that contain a peripheral membrane protein that binds the PM and also a protein that binds MVBs or the tonoplast. PM-binding proteins capable of participating in PM-MVB/TP tethering included StRem1.3, BIK1, PBS1, CPK21, and the PtdIns(4)-binding proteins FAPP1 and Osh2. MVB/TP-binding proteins capable of participating in tethering included ARA6, ARA7, RHA1, RABG3f, and the PtdIns(3)P-binding proteins Vam7p and Hrs-2xFYVE. BiFC complexes or protein fusions capable of producing PM-MVB/TP tethering were visualized as large well-defined patches of fluorescence on the PM that could displace PM proteins such as AtFlotillin1 and also could displace cytoplasmic proteins such as soluble GFP. Furthermore, we identified paralogous ubiquitin E3 ligase proteins, SAUL1 (AtPUB44), and AtPUB43 that could produce PM-MVB/TP tethering. SAUL1 and AtPUB43 could produce tethering in uninfected tissue when paired with MVB-binding proteins or when their E3 ligase domain was deleted. When Nicotiana benthamiana leaf tissue was infected with Phytophthora capsici, full length SAUL1 and AtPUB43 localized in membrane patches consistent with PM-MVB/TP tethering. Our findings define new tools for studying PM-MVB/TP tethering and its possible role in plant defense. SIGNIFICANCE STATEMENT Although not previously observed, the tethering of multi-vesicular bodies to the plasma membrane is of interest due to the potential role of this process in producing exosomes in plants. Here we describe tools for observing and manipulating the tethering of multi-vesicular bodies and the tonoplast to the plant plasma membrane, and describe two plant proteins that may naturally regulate this process during infection.
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Affiliation(s)
- Kai Tao
- Molecular and Cellular Biology Program, Oregon State University, Corvallis, OR, United States
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR, United States
| | - Justin R. Waletich
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR, United States
| | - Hua Wise
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR, United States
| | - Felipe Arredondo
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR, United States
| | - Brett M. Tyler
- Molecular and Cellular Biology Program, Oregon State University, Corvallis, OR, United States
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR, United States
- Center for Genome Research and Biocomputing, Oregon State University, Corvallis, OR, United States
- *Correspondence: Brett M. Tyler
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7
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Song H, Orr A, Duan M, Merz AJ, Wickner W. Sec17/Sec18 act twice, enhancing membrane fusion and then disassembling cis-SNARE complexes. eLife 2017; 6:e26646. [PMID: 28718762 PMCID: PMC5540461 DOI: 10.7554/elife.26646] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 07/17/2017] [Indexed: 12/17/2022] Open
Abstract
At physiological protein levels, the slow HOPS- and SNARE-dependent fusion which occurs upon complete SNARE zippering is stimulated by Sec17 and Sec18:ATP without requiring ATP hydrolysis. To stimulate, Sec17 needs its central residues which bind the 0-layer of the SNARE complex and its N-terminal apolar loop. Adding a transmembrane anchor to the N-terminus of Sec17 bypasses this requirement for apolarity of the Sec17 loop, suggesting that the loop functions for membrane binding rather than to trigger bilayer rearrangement. In contrast, when complete C-terminal SNARE zippering is prevented, fusion strictly requires Sec18 and Sec17, and the Sec17 apolar loop has functions beyond membrane anchoring. Thus Sec17 and Sec18 act twice in the fusion cycle, binding to trans-SNARE complexes to accelerate fusion, then hydrolyzing ATP to disassemble cis-SNARE complexes.
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Affiliation(s)
- Hongki Song
- Department of Biochemistry and Cell Biology, Geisel School of Medicine, Hanover, United States
| | - Amy Orr
- Department of Biochemistry and Cell Biology, Geisel School of Medicine, Hanover, United States
| | - Mengtong Duan
- Departments of Biochemistry, University of Washington, Seattle, United States
| | - Alexey J Merz
- Departments of Biochemistry, University of Washington, Seattle, United States
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
| | - William Wickner
- Department of Biochemistry and Cell Biology, Geisel School of Medicine, Hanover, United States
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8
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Song H, Wickner W. A short region upstream of the yeast vacuolar Qa-SNARE heptad-repeats promotes membrane fusion through enhanced SNARE complex assembly. Mol Biol Cell 2017. [PMID: 28637767 PMCID: PMC5555656 DOI: 10.1091/mbc.e17-04-0218] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Membrane fusion requires that four SNARE domains form a complex. A short conserved region just upstream of the Qa-SNARE heptad-repeat domain promotes SNARE-complex assembly and hence fusion. Whereas SNARE (soluble N-ethylmaleimide–sensitive factor attachment protein receptor) heptad-repeats are well studied, SNAREs also have upstream N-domains of indeterminate function. The assembly of yeast vacuolar SNAREs into complexes for fusion can be studied in chemically defined reactions. Complementary proteoliposomes bearing a Rab:GTP and either the vacuolar R-SNARE or one of the three integrally anchored Q-SNAREs were incubated with the tethering/SM protein complex HOPS and the two other soluble SNAREs (lacking a transmembrane anchor) or their SNARE heptad-repeat domains. Fusion required a transmembrane-anchored R-SNARE on one membrane and an anchored Q-SNARE on the other. The N-domain of the Qb-SNARE was completely dispensable for fusion. Whereas fusion can be promoted by very high concentrations of the Qa-SNARE heptad-repeat domain alone, at physiological concentrations the Qa-SNARE heptad-repeat domain alone has almost no fusion activity. The 181–198 region of Qa, immediately upstream of the SNARE heptad-repeat domain, is required for normal fusion activity with HOPS. This region is needed for normal SNARE complex assembly.
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Affiliation(s)
- Hongki Song
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755-3844
| | - William Wickner
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755-3844
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9
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Zick M, Wickner W. Improved reconstitution of yeast vacuole fusion with physiological SNARE concentrations reveals an asymmetric Rab(GTP) requirement. Mol Biol Cell 2016; 27:2590-7. [PMID: 27385334 PMCID: PMC4985260 DOI: 10.1091/mbc.e16-04-0230] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Accepted: 06/21/2016] [Indexed: 11/11/2022] Open
Abstract
In vitro reconstitution is a powerful approach to deciphering membrane fusion. However, current reconstitutions do not adequately mimic the physiological process. This study takes a big step toward overcoming those shortcomings, achieving fusion with SNARE densities comparable to the native membrane. In vitro reconstitution of homotypic yeast vacuole fusion from purified components enables detailed study of membrane fusion mechanisms. Current reconstitutions have yet to faithfully replicate the fusion process in at least three respects: 1) The density of SNARE proteins required for fusion in vitro is substantially higher than on the organelle. 2) Substantial lysis accompanies reconstituted fusion. 3) The Rab GTPase Ypt7 is essential in vivo but often dispensable in vitro. Here we report that changes in fatty acyl chain composition dramatically lower the density of SNAREs that are required for fusion. By providing more physiological lipids with a lower phase transition temperature, we achieved efficient fusion with SNARE concentrations as low as on the native organelle. Although fused proteoliposomes became unstable at elevated SNARE concentrations, releasing their content after fusion had occurred, reconstituted proteoliposomes with substantially reduced SNARE concentrations fused without concomitant lysis. The Rab GTPase Ypt7 is essential on both membranes for proteoliposome fusion to occur at these SNARE concentrations. Strikingly, it was only critical for Ypt7 to be GTP loaded on membranes bearing the R-SNARE Nyv1, whereas the bound nucleotide of Ypt7 was irrelevant on membranes bearing the Q-SNAREs Vam3 and Vti1.
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Affiliation(s)
- Michael Zick
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, NH 03755-3844
| | - William Wickner
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, NH 03755-3844
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10
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Helliwell EE, Vega-Arreguín J, Shi Z, Bailey B, Xiao S, Maximova SN, Tyler BM, Guiltinan MJ. Enhanced resistance in Theobroma cacao against oomycete and fungal pathogens by secretion of phosphatidylinositol-3-phosphate-binding proteins. PLANT BIOTECHNOLOGY JOURNAL 2016. [PMID: 26214158 DOI: 10.1111/pbi.12436] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The internalization of some oomycete and fungal pathogen effectors into host plant cells has been reported to be blocked by proteins that bind to the effectors' cell entry receptor, phosphatidylinositol-3-phosphate (PI3P). This finding suggested a novel strategy for disease control by engineering plants to secrete PI3P-binding proteins. In this study, we tested this strategy using the chocolate tree Theobroma cacao. Transient expression and secretion of four different PI3P-binding proteins in detached leaves of T. cacao greatly reduced infection by two oomycete pathogens, Phytophthora tropicalis and Phytophthora palmivora, which cause black pod disease. Lesion size and pathogen growth were reduced by up to 85%. Resistance was not conferred by proteins lacking a secretory leader, by proteins with mutations in their PI3P-binding site, or by a secreted PI4P-binding protein. Stably transformed, transgenic T. cacao plants expressing two different PI3P-binding proteins showed substantially enhanced resistance to both P. tropicalis and P. palmivora, as well as to the fungal pathogen Colletotrichum theobromicola. These results demonstrate that secretion of PI3P-binding proteins is an effective way to increase disease resistance in T. cacao, and potentially in other plants, against a broad spectrum of pathogens.
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Affiliation(s)
- Emily E Helliwell
- Department of Plant Science and Huck Institute of Life Sciences, The Pennsylvania State University, University Park, PA, USA
- Center for Genome Research and Biocomputing, and Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR, USA
| | - Julio Vega-Arreguín
- Virginia Bioinformatics Institute and Department of Plant Pathology, Physiology and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA
| | - Zi Shi
- Department of Plant Science and Huck Institute of Life Sciences, The Pennsylvania State University, University Park, PA, USA
| | - Bryan Bailey
- United States Department of Agriculture, Agricultural Research Service, Beltsville, MD, USA
| | - Shunyuan Xiao
- Institute for Bioscience and Biotechnology Research & Department of Plant Science and Landscape Architecture, University of Maryland, College Park, MD, USA
| | - Siela N Maximova
- Department of Plant Science and Huck Institute of Life Sciences, The Pennsylvania State University, University Park, PA, USA
| | - Brett M Tyler
- Center for Genome Research and Biocomputing, and Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR, USA
- Virginia Bioinformatics Institute and Department of Plant Pathology, Physiology and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA
| | - Mark J Guiltinan
- Department of Plant Science and Huck Institute of Life Sciences, The Pennsylvania State University, University Park, PA, USA
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11
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Lenoir M, Grzybek M, Majkowski M, Rajesh S, Kaur J, Whittaker SBM, Coskun Ü, Overduin M. Structural Basis of Dynamic Membrane Recognition by trans-Golgi Network Specific FAPP Proteins. J Mol Biol 2015; 427:966-981. [DOI: 10.1016/j.jmb.2014.12.023] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Revised: 12/17/2014] [Accepted: 12/29/2014] [Indexed: 10/24/2022]
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12
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Orr A, Wickner W, Rusin SF, Kettenbach AN, Zick M. Yeast vacuolar HOPS, regulated by its kinase, exploits affinities for acidic lipids and Rab:GTP for membrane binding and to catalyze tethering and fusion. Mol Biol Cell 2014; 26:305-15. [PMID: 25411340 PMCID: PMC4294677 DOI: 10.1091/mbc.e14-08-1298] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Acidic lipids act as coreceptors with Ypt7p to bind the HOPS complex to support membrane tethering and fusion. After phosphorylation by the vacuolar kinase Yck3p, phospho-HOPS needs both Ypt7p:GTP and acidic lipids to support fusion. Fusion of yeast vacuoles requires the Rab GTPase Ypt7p, four SNAREs (soluble N-ethylmaleimide–sensitive factor attachment protein receptors), the SNARE disassembly chaperones Sec17p/Sec18p, vacuolar lipids, and the Rab-effector complex HOPS (homotypic fusion and vacuole protein sorting). Two HOPS subunits have direct affinity for Ypt7p. Although vacuolar fusion has been reconstituted with purified components, the functional relationships between individual lipids and Ypt7p:GTP have remained unclear. We now report that acidic lipids function with Ypt7p as coreceptors for HOPS, supporting membrane tethering and fusion. After phosphorylation by the vacuolar kinase Yck3p, phospho-HOPS needs both Ypt7p:GTP and acidic lipids to support fusion.
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Affiliation(s)
- Amy Orr
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
| | - William Wickner
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
| | - Scott F Rusin
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
| | - Arminja N Kettenbach
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, NH 03755 Norris Cotton Cancer Center, Lebanon, NH 03756
| | - Michael Zick
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
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13
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Hosomi A, Higuchi Y, Yagi S, Takegawa K. Vsl1p cooperates with Fsv1p for vacuolar protein transport and homotypic fusion in Schizosaccharomyces pombe. MICROBIOLOGY-SGM 2014; 161:89-98. [PMID: 25378562 DOI: 10.1099/mic.0.080481-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Members of the SNARE protein family participate in the docking-fusion step of several intracellular vesicular transport events. Saccharomyces cerevisiae Vam7p was identified as a SNARE protein that acts in vacuolar protein transport and membrane fusion. However, in Schizosaccharomyces pombe, there have been no reports regarding the counterpart of Vam7p. Here, we found that, although the SPCC594.06c gene has low similarity to Vam7p, the product of SPCC594.06c has a PX domain and SNARE motif like Vam7p, and thus we designated the gene Sch. pombe vsl1(+) (Vam7-like protein 1). The vsl1Δ cells showed no obvious defect in vacuolar protein transport. However, cells of the vsl1Δ mutant with a deletion of fsv1(+), which encodes another SNARE protein, displayed extreme defects in vacuolar protein transport and vacuolar morphology. Vsl1p was localized to the vacuolar membrane and prevacuolar compartment, and its PX domain was essential for proper localization. Expression of the fusion protein GFP-Vsl1p was able to suppress ZnCl2 sensitivity and the vacuolar protein sorting defect in the fsv1Δ cells. Moreover, GFP-Vsl1p was mislocalized in a pep12Δ mutant and in cells overexpressing fsv1(+). Importantly, overexpression of Sac. cerevisiae VAM7 could suppress the sensitivity to ZnCl2 of vsl1Δ cells and the vacuolar morphology defect of vsl1Δfsv1Δ cells in Sch. pombe. Taken together, these data suggest that Vsl1p and Fsv1p are required for vacuolar protein transport and membrane fusion, and they function cooperatively with Pep12p in the same membrane-trafficking step.
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Affiliation(s)
- Akira Hosomi
- Department of Bioscience and Biotechnology, Faculty of Agriculture, Kyushu University, 6-10-1 Hakozaki, Fukuoka 812-8581, Japan
| | - Yujiro Higuchi
- Department of Bioscience and Biotechnology, Faculty of Agriculture, Kyushu University, 6-10-1 Hakozaki, Fukuoka 812-8581, Japan
| | - Satoshi Yagi
- Department of Bioscience and Biotechnology, Faculty of Agriculture, Kyushu University, 6-10-1 Hakozaki, Fukuoka 812-8581, Japan
| | - Kaoru Takegawa
- Department of Bioscience and Biotechnology, Faculty of Agriculture, Kyushu University, 6-10-1 Hakozaki, Fukuoka 812-8581, Japan
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14
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Zick M, Wickner WT. A distinct tethering step is vital for vacuole membrane fusion. eLife 2014; 3:e03251. [PMID: 25255215 PMCID: PMC4200421 DOI: 10.7554/elife.03251] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2014] [Accepted: 09/24/2014] [Indexed: 12/12/2022] Open
Abstract
Past experiments with reconstituted proteoliposomes, employing assays that infer membrane fusion from fluorescent lipid dequenching, have suggested that vacuolar SNAREs alone suffice to catalyze membrane fusion in vitro. While we could replicate these results, we detected very little fusion with the more rigorous assay of lumenal compartment mixing. Exploring the discrepancies between lipid-dequenching and content-mixing assays, we surprisingly found that the disposition of the fluorescent lipids with respect to SNAREs had a striking effect. Without other proteins, the association of SNAREs in trans causes lipid dequenching that cannot be ascribed to fusion or hemifusion. Tethering of the SNARE-bearing proteoliposomes was required for efficient lumenal compartment mixing. While the physiological HOPS tethering complex caused a few-fold increase of trans-SNARE association, the rate of content mixing increased more than 100-fold. Thus tethering has a role in promoting membrane fusion that extends beyond simply increasing the amount of total trans-SNARE complex. DOI:http://dx.doi.org/10.7554/eLife.03251.001 Cells of higher organisms contain compartments called organelles and structures called vesicles that transfer molecules and proteins between these organelles. Each organelle and each vesicle is enclosed within a membrane, and these membranes must fuse together to allow these transfers to take place. A certain group of proteins, called SNAREs, have a central role in these fusion events. Since membrane fusion is difficult to observe directly, many researchers have used a method called ‘fluorescent lipid dequenching’ to study it indirectly. In this approach, one fraction of vesicles is labeled with two fluorescent molecules, with one of these molecules quenching the fluorescence of the other. However, when a labeled vesicle fuses with an unlabeled vesicle, the surface concentrations of the fluorescent molecules are diluted. This reduces the amount of quenching and the resulting increase in fluorescence can be measured. Experiments utilizing this technique had suggested that SNARE proteins are sufficient for fusion to take place, and that no other protein complexes need to be present. However, when a different assay method called ‘lumenal compartment mixing’ was used, little fusion was seen when the only proteins present were the SNAREs. The lumenal compartment mixing approach relies on measuring the degree of mixing between the contents of two vesicles. To address these conflicting results, Zick and Wickner used both methods to study fusion in a yeast-based system. The lumenal compartment mixing approach, which is the more reliable method, revealed that rapid and efficient membrane fusion in fact requires another protein complex, called HOPS, to hold the two membrane vesicles together. Zick and Wickner found that the HOPS complex does not enable fusion by just increasing the amount of interactions between the SNARE proteins. Rather, it seems to facilitate the formation of a particular quality of SNARE interactions. Future work is needed to work out how the SNARE complexes become ‘fusion-competent’, and to explore the mechanism that allows the HOPS complex to assist in the formation of fusion-competent SNARE complexes. DOI:http://dx.doi.org/10.7554/eLife.03251.002
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Affiliation(s)
- Michael Zick
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, United States
| | - William T Wickner
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, United States
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15
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Capelluto DGS, Zhao X, Lucas A, Lemkul JA, Xiao S, Fu X, Sun F, Bevan DR, Finkielstein CV. Biophysical and molecular-dynamics studies of phosphatidic acid binding by the Dvl-2 DEP domain. Biophys J 2014; 106:1101-11. [PMID: 24606934 PMCID: PMC4026774 DOI: 10.1016/j.bpj.2014.01.032] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 01/08/2014] [Accepted: 01/27/2014] [Indexed: 11/16/2022] Open
Abstract
The Wnt-dependent, β-catenin-independent pathway modulates cell movement and behavior. A downstream regulator of this signaling pathway is Dishevelled (Dvl), which, among other multiple interactions, binds to the Frizzled receptor and the plasma membrane via phosphatidic acid (PA) in a mechanism proposed to be pH-dependent. While the Dvl DEP domain is central to the β-catenin-independent Wnt signaling function, the mechanism underlying its physical interaction with the membrane remains elusive. In this report, we elucidate the structural and functional basis of PA association to the Dvl2 DEP domain. Nuclear magnetic resonance, molecular-dynamics simulations, and mutagenesis data indicated that the domain interacted with the phospholipid through the basic helix 3 and a contiguous loop with moderate affinity. The association suggested that PA binding promoted local conformational changes in helix 2 and β-strand 4, both of which are compromised to maintain a stable hydrophobic core in the DEP domain. We also show that the Dvl2 DEP domain bound PA in a pH-dependent manner in a mechanism that resembles deprotonation of PA. Collectively, our results structurally define the PA-binding properties of the Dvl2 DEP domain, which can be exploited for the investigation of binding mechanisms of other DEP domain-interacting proteins.
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Affiliation(s)
| | - Xiaolin Zhao
- Protein Signaling Domains Laboratory, Virginia Tech, Blacksburg, Virginia
| | - Andrew Lucas
- Protein Signaling Domains Laboratory, Virginia Tech, Blacksburg, Virginia; Integrated Cellular Responses Laboratory, Department of Biological Sciences, Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia
| | - Justin A Lemkul
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia
| | - Shuyan Xiao
- Protein Signaling Domains Laboratory, Virginia Tech, Blacksburg, Virginia
| | - Xiangping Fu
- Integrated Cellular Responses Laboratory, Department of Biological Sciences, Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia
| | - Furong Sun
- Protein Signaling Domains Laboratory, Virginia Tech, Blacksburg, Virginia
| | - David R Bevan
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia
| | - Carla V Finkielstein
- Integrated Cellular Responses Laboratory, Department of Biological Sciences, Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia
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16
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Multiple and distinct strategies of yeast SNAREs to confer the specificity of membrane fusion. Sci Rep 2014; 4:4277. [PMID: 24589832 PMCID: PMC3940976 DOI: 10.1038/srep04277] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2014] [Accepted: 02/17/2014] [Indexed: 01/04/2023] Open
Abstract
Trans-QabcR-SNARE pairing on opposing membranes is crucial for eukaryotic membrane fusion, but how selective pairs of Qabc- and R-SNARE proteins regulate membrane fusion specificity remains elusive. Here, we studied 14 purified full-length SNAREs that function in yeast endoplasmic reticulum (ER)-Golgi, intra-Golgi, endosomal, and vacuolar transport by comprehensively testing cis-QabcR-SNARE assembly and fusogenicity of reconstituted SNARE proteoliposomes. Strikingly, the cognate ER-Golgi and intra-Golgi SNARE-complex assemblies were highly stringent, whereas endosomal and vacuolar SNAREs assembled rather promiscuously into the non-cognate mixed complexes. However, these patterns of cis-SNARE assemblies cannot solely explain their potency to be fusogenic via trans-SNARE pairing: Only the vacuolar 3Q-SNARE combination is fusogenic in the absence of additional components; endosomal SNARE-dependent fusogenicity requires membrane-tethering factors; and ER-Golgi SNAREs can be fusogenic by synergistic actions of tethering factors and the cognate Sec1/Munc18-family protein Sly1p. Thus, our findings uncover multiple and distinct strategies of SNAREs to directly mediate fusion specificity.
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17
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Zick M, Stroupe C, Orr A, Douville D, Wickner WT. Membranes linked by trans-SNARE complexes require lipids prone to non-bilayer structure for progression to fusion. eLife 2014; 3:e01879. [PMID: 24596153 PMCID: PMC3937803 DOI: 10.7554/elife.01879] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Like other intracellular fusion events, the homotypic fusion of yeast vacuoles requires a Rab GTPase, a large Rab effector complex, SNARE proteins which can form a 4-helical bundle, and the SNARE disassembly chaperones Sec17p and Sec18p. In addition to these proteins, specific vacuole lipids are required for efficient fusion in vivo and with the purified organelle. Reconstitution of vacuole fusion with all purified components reveals that high SNARE levels can mask the requirement for a complex mixture of vacuole lipids. At lower, more physiological SNARE levels, neutral lipids with small headgroups that tend to form non-bilayer structures (phosphatidylethanolamine, diacylglycerol, and ergosterol) are essential. Membranes without these three lipids can dock and complete trans-SNARE pairing but cannot rearrange their lipids for fusion. DOI:http://dx.doi.org/10.7554/eLife.01879.001 All cells are enclosed with a membrane that is made of phospholipid molecules, and many of the structures found inside cells—such as the vacuoles in plant and fungal cells—are also enclosed with a phospholipid membrane. To form a membrane, the phospholipid molecules—which have a phosphate head and two fatty acid tails—arrange themselves in two layers, with the fatty acid tails pointing into the membrane, and the phosphate heads pointing outwards. This structure is known as a phospholipid bilayer. Vacuoles are filled with water that contains various proteins and molecules in solution, and adjust their volume to keep the concentrations of substances in the cell in balance. To do this, the vacuoles fuse with each other. This fusion process requires dramatic spatial rearrangements of the phospholipid molecules. The SNARE family of proteins plays a key role in membrane fusion. As the two membranes come together, SNARE proteins located on each membrane form a complex known as a trans-SNARE complex. This docks the vacuole in place beside another vacuole while the phospholipid molecules in the two membranes rearrange. However, much less is known about the phospholipid molecules that are involved in the fusion process. Now, Zick et al. have shown that three types of phospholipid molecules must be present for membrane fusion to be completed. These have in common that their phosphate ‘headgroups’ are small and they do not tend to form bilayers. The vacuoles can dock beside each other if these small headgroup phospholipid molecules are not present, but the bilayer lipids in the vacuole membranes cannot rearrange themselves in the absence of these particular lipids. The importance of these nonbilayer lipid molecules had not previously been established, as the majority of experiments investigating membrane fusion used concentrations of SNARE proteins that were much higher than those found physiologically. At such high concentrations, fusion can go ahead without the nonbilayer lipid molecules being present. DOI:http://dx.doi.org/10.7554/eLife.01879.002
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Affiliation(s)
- Michael Zick
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, United States
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18
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Sun F, Kale SD, Azurmendi HF, Li D, Tyler BM, Capelluto DGS. Structural basis for interactions of the Phytophthora sojae RxLR effector Avh5 with phosphatidylinositol 3-phosphate and for host cell entry. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2013; 26:330-44. [PMID: 23075041 DOI: 10.1094/mpmi-07-12-0184-r] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Oomycetes such as Phytophthora sojae employ effector proteins that enter plant cells to facilitate infection. Entry of some effector proteins is mediated by RxLR motifs in the effectors and phosphoinositides (PIP) resident in the host plasma membrane such as phosphatidylinositol 3-phosphate (PtdIns(3)P). Recent reports differ regarding the regions on RxLR effectors involved in PIP recognition. We have structurally and functionally characterized the P. sojae effector, avirulence homolog-5 (Avh5). Using nuclear magnetic resonance (NMR) spectroscopy, we demonstrate that Avh5 is helical in nature, with a long N-terminal disordered region. NMR titrations of Avh5 with the PtdIns(3)P head group, inositol 1,3-bisphosphate, directly identified the ligand-binding residues. A C-terminal lysine-rich helical region (helix 2) was the principal lipid-binding site, with the N-terminal RxLR (RFLR) motif playing a more minor role. Mutations in the RFLR motif affected PtdIns(3)P binding, while mutations in the basic helix almost abolished it. Mutations in the RFLR motif or in the basic region both significantly reduced protein entry into plant and human cells. Both regions independently mediated cell entry via a PtdIns(3)P-dependent mechanism. Based on these findings, we propose a model where Avh5 interacts with PtdIns(3)P through its C terminus, and by binding of the RFLR motif, which promotes host cell entry.
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Affiliation(s)
- Furong Sun
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, USA
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19
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Trio engagement via plasma membrane phospholipids and the myristoyl moiety governs HIV-1 matrix binding to bilayers. Proc Natl Acad Sci U S A 2013; 110:3525-30. [PMID: 23401539 DOI: 10.1073/pnas.1216655110] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Localization of the HIV type-1 (HIV-1) Gag protein on the plasma membrane (PM) for virus assembly is mediated by specific interactions between the N-terminal myristoylated matrix (MA) domain and phosphatidylinositol-(4,5)-bisphosphate [PI(4,5)P(2)]. The PM bilayer is highly asymmetric, and this asymmetry is considered crucial in cell function. In a typical mammalian cell, the inner leaflet of the PM is enriched in phosphatidylserine (PS) and phosphatidylethanolamine (PE) and contains minor populations of phosphatidylcholine (PC) and PI(4,5)P(2). There is strong evidence that efficient binding of HIV-1 Gag to membranes is sensitive not only to lipid composition and net negative charge, but also to the hydrophobic character of the acyl chains. Here, we show that PS, PE, and PC interact directly with MA via a region that is distinct from the PI(4,5)P(2) binding site. Our NMR data also show that the myristoyl group is readily exposed when MA is bound to micelles or bicelles. Strikingly, our structural data reveal a unique binding mode by which the 2'-acyl chain of PS, PE, and PC lipids is buried in a hydrophobic pocket whereas the 1'-acyl chain is exposed. Sphingomyelin, a major lipid localized exclusively on the outer layer of the PM, does not bind to MA. Our findings led us to propose a trio engagement model by which HIV-1 Gag is anchored to the PM via the 1'-acyl chains of PI(4,5)P(2) and PS/PE/PC and the myristoyl group, which collectively bracket a basic patch projecting toward the polar leaflet of the membrane.
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20
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Jiang RHY, Stahelin RV, Bhattacharjee S, Haldar K. Eukaryotic virulence determinants utilize phosphoinositides at the ER and host cell surface. Trends Microbiol 2013; 21:145-56. [PMID: 23375057 DOI: 10.1016/j.tim.2012.12.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2012] [Revised: 12/12/2012] [Accepted: 12/18/2012] [Indexed: 01/03/2023]
Abstract
Similar to bacteria, eukaryotic pathogens may utilize common strategies of pathogenic secretion, because effector proteins from the oomycete Phytophthora infestans and virulence determinants from the human malaria parasite Plasmodium falciparum share a functionally equivalent host-cell-targeting motif (RxLR-dEER in P. infestans and RxLxE/D/Q in P. falciparum). Here we summarize recent studies that reveal that the malarial motif may function differently than previously envisioned. Binding of the lipid phosphatidylinositol 3-phosphate [PI(3)P] is a critical step in accessing the host for both pathogens, but occurs in different locations. Nanomolar affinity for PI(3)P by these short amino acid motifs suggests that a newly identified mechanism of phosphoinositide binding that unexpectedly occurs in secretory locations has been exploited for virulence by diverse eukaryotic pathogens.
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Affiliation(s)
- Rays H Y Jiang
- Department of Infectious Diseases and Immunology, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115, USA
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21
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Yokogawa M, Kobashigawa Y, Yoshida N, Ogura K, Harada K, Inagaki F. NMR analyses of the interaction between the FYVE domain of early endosome antigen 1 (EEA1) and phosphoinositide embedded in a lipid bilayer. J Biol Chem 2012; 287:34936-34945. [PMID: 22915584 DOI: 10.1074/jbc.m112.398255] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phosphoinositides (PIs) are crucial lipid components of membranes and are involved in a number of cellular processes through interactions with their effector proteins. Recently, we have established a lipid-protein nanoscale bilayer (nanodisc) containing PIs, hereafter referred to as PI-nanodisc and demonstrated that it could be used for both qualitative and quantitative evaluations of protein-membrane interactions. Here, we report further NMR analyses for obtaining structural insights at the residue-specific level between PI-binding effector protein and PI-nanodisc, using the FYVE domain of early endosome antigen 1 (EEA1), denoted as EEA1 FYVE, and PI(3)P-nanodisc as a model system. We performed a combination of the NMR analyses including chemical shift perturbation, transferred cross-saturation, and paramagnetic relaxation enhancement experiments. These enabled an identification of the interaction surface, structural change, and relative orientation of EEA1 FYVE to the PI(3)P-incorporated lipid bilayer, substantiating that NMR analyses of protein-membrane interactions using nanodisc makes it possible to show the residue-specific interactions in the lipid bilayer environment.
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Affiliation(s)
- Mariko Yokogawa
- Faculty of Advanced Life Science, Hokkaido University, Sapporo 001-0021, Japan
| | | | - Naoki Yoshida
- Graduate School of Life Science, Hokkaido University, Sapporo 060-0810, Japan
| | - Kenji Ogura
- Faculty of Advanced Life Science, Hokkaido University, Sapporo 001-0021, Japan
| | - Kohsuke Harada
- Graduate School of Life Science, Hokkaido University, Sapporo 060-0810, Japan
| | - Fuyuhiko Inagaki
- Faculty of Advanced Life Science, Hokkaido University, Sapporo 001-0021, Japan.
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22
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Structural and functional characterization of the two phosphoinositide binding sites of PROPPINs, a β-propeller protein family. Proc Natl Acad Sci U S A 2012; 109:E2042-9. [PMID: 22753491 DOI: 10.1073/pnas.1205128109] [Citation(s) in RCA: 124] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
β-propellers that bind polyphosphoinositides (PROPPINs), a eukaryotic WD-40 motif-containing protein family, bind via their predicted β-propeller fold the polyphosphoinositides PtdIns3P and PtdIns(3,5)P(2) using a conserved FRRG motif. PROPPINs play a key role in macroautophagy in addition to other functions. We present the 3.0-Å crystal structure of Kluyveromyces lactis Hsv2, which shares significant sequence homologies with its three Saccharomyces cerevisiae homologs Atg18, Atg21, and Hsv2. It adopts a seven-bladed β-propeller fold with a rare nonvelcro propeller closure. Remarkably, in the crystal structure, the two arginines of the FRRG motif are part of two distinct basic pockets formed by a set of highly conserved residues. In comprehensive in vivo and in vitro studies of ScAtg18 and ScHsv2, we define within the two pockets a set of conserved residues essential for normal membrane association, phosphoinositide binding, and biological activities. Our experiments show that PROPPINs contain two individual phosphoinositide binding sites. Based on docking studies, we propose a model for phosphoinositide binding of PROPPINs.
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23
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Stampoulis P, Ueda T, Matsumoto M, Terasawa H, Miyano K, Sumimoto H, Shimada I. Atypical membrane-embedded phosphatidylinositol 3,4-bisphosphate (PI(3,4)P2)-binding site on p47(phox) Phox homology (PX) domain revealed by NMR. J Biol Chem 2012; 287:17848-17859. [PMID: 22493288 DOI: 10.1074/jbc.m111.332874] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Phox homology (PX) domain is a functional module that targets membranes through specific interactions with phosphoinositides. The p47(phox) PX domain preferably binds phosphatidylinositol 3,4-bisphosphate (PI(3,4)P(2)) and plays a pivotal role in the assembly of phagocyte NADPH oxidase. We describe the PI(3,4)P(2) binding mode of the p47(phox) PX domain as identified by a transferred cross-saturation experiment. The identified PI(3,4)P(2)-binding site, which includes the residues of helices α1 and α1' and the following loop up to the distorted left-handed PP(II) helix, is located at a unique position, as compared with the phosphoinositide-binding sites of all other PX domains characterized thus far. Mutational analyses corroborated the results of the transferred cross-saturation experiments. Moreover, experiments with intact cells demonstrated the importance of this unique binding site for the function of the NADPH oxidase. The low affinity and selectivity of the atypical phosphoinositide-binding site on the p47(phox) PX domain suggest that different types of phosphoinositides sequentially bind to the p47(phox) PX domain, allowing the regulation of the multiple events that characterize the assembly and activation of phagocyte NADPH oxidase.
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Affiliation(s)
- Pavlos Stampoulis
- Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo 113-0033; Japan Biological Informatics Consortium, Tokyo 104-0032
| | - Takumi Ueda
- Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo 113-0033
| | - Masahiko Matsumoto
- Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo 113-0033
| | - Hiroaki Terasawa
- Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo 113-0033
| | - Kei Miyano
- Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582
| | - Hideki Sumimoto
- Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582
| | - Ichio Shimada
- Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo 113-0033; Biomedicinal Information Research Center, National Institute of Advanced Industrial Science and Technology, Tokyo 135-0064, Japan.
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24
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He J, Gajewiak J, Scott JL, Gong D, Ali M, Best MD, Prestwich GD, Stahelin RV, Kutateladze TG. Metabolically stabilized derivatives of phosphatidylinositol 4-phosphate: synthesis and applications. ACTA ACUST UNITED AC 2012; 18:1312-9. [PMID: 22035800 DOI: 10.1016/j.chembiol.2011.07.022] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Revised: 07/07/2011] [Accepted: 07/08/2011] [Indexed: 01/19/2023]
Abstract
Phosphatidylinositol 4-phosphate (PtdIns(4)P) lipid is an essential component of eukaryotic membranes and a marker of the Golgi complex. Here, we developed metabolically stabilized (ms) analogs of PtdIns(4)P and the inositol 1,4-bisphosphate (IP(2)) head group derivative and demonstrated that these compounds can substitute the natural lipid fully retaining its physiological activities. The methylenephosphonate (MP) and phosphorothioate (PT) analogs of PtdIns(4)P and the aminohexyl (AH)-IP(2) probe are recognized by the PtdIns(4)P-specific PH domain of four phosphate adaptor protein 1 (FAPP1). Binding of FAPP1 to the PtdIns(4)P derivatives stimulates insertion of the PH domain into the lipid layers and induces tubulation of membranes. Both ms analogs and IP(2) probes could be invaluable for identifying protein effectors and characterizing PtdIns(4)P-dependent signaling cascades within the trans-Golgi network (TGN).
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Affiliation(s)
- Ju He
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
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25
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Abstract
In recent years, the functional roles of effectors from a wide variety of fungal and oomycete pathogens have begun to emerge. As a product of this work, the importance of effector-lipid interactions has been made apparent. Phospholipids are not only important signaling molecules, but they also play important roles in the trafficking of endosomes and the localization of proteins. Characterizing effector-lipid interactions can provide novel information regarding the functions of effectors relevant to their cellular and subcellular targeting and their potential effects on host signaling and vesicle trafficking. We present here two techniques that can be used to screen for and validate protein-lipid interactions without the need to access highly specialized machinery. We describe in detail how to perform lipid filter and liposome-binding assays and provide suggestions for troubleshooting potential problems with these assays.
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Affiliation(s)
- Shiv D Kale
- Virginia Bioinformatics Institute, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA.
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26
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Abstract
Diverse biological processes including cell growth and survival require transient association of proteins with cellular membranes. A large number of these proteins are drawn to a bilayer through binding of their modular domains to phosphoinositide (PI) lipids. Seven PI isoforms are found to concentrate in distinct pools of intracellular membranes, and this lipid compartmentalization provides an efficient way for recruiting PI-binding proteins to specific cellular organelles. The atomic-resolution structures and membrane docking mechanisms of a dozen PI effectors have been elucidated in the last decade, offering insight into the molecular basis for regulation of the PI-dependent signaling pathways. In this chapter, I summarize the mechanistic aspects of deciphering the 'PI code' by the most common PI-recognizing domains and discuss similarities and differences in the membrane anchoring mechanisms.
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Affiliation(s)
- Tatiana G Kutateladze
- Department of Pharmacology, University of Colorado Denver School of Medicine, Aurora, CO 80045, USA.
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27
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Wells RC, Hill RB. The cytosolic domain of Fis1 binds and reversibly clusters lipid vesicles. PLoS One 2011; 6:e21384. [PMID: 21738650 PMCID: PMC3125187 DOI: 10.1371/journal.pone.0021384] [Citation(s) in RCA: 15] [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: 01/21/2011] [Accepted: 05/27/2011] [Indexed: 11/18/2022] Open
Abstract
Every lipid membrane fission event involves the association of two apposing bilayers, mediated by proteins that can promote membrane curvature, fusion and fission. We tested the hypothesis that Fis1, a tail-anchored protein involved in mitochondrial and peroxisomal fission, promotes changes in membrane structure. We found that the cytosolic domain of Fis1 alone binds lipid vesicles, which is enhanced upon protonation and increasing concentrations of anionic phospholipids. Fluorescence and circular dichroism data indicate that the cytosolic domain undergoes a membrane-induced conformational change that buries two tryptophan side chains upon membrane binding. Light scattering and electron microscopy data show that membrane binding promotes lipid vesicle clustering. Remarkably, this vesicle clustering is reversible and vesicles largely retain their original shape and size. This raises the possibility that the Fis1 cytosolic domain might act in membrane fission by promoting a reversible membrane association, a necessary step in membrane fission.
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Affiliation(s)
- Robert C. Wells
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - R. Blake Hill
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, United States of America
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland, United States of America
- * E-mail:
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28
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He J, Scott JL, Heroux A, Roy S, Lenoir M, Overduin M, Stahelin RV, Kutateladze TG. Molecular basis of phosphatidylinositol 4-phosphate and ARF1 GTPase recognition by the FAPP1 pleckstrin homology (PH) domain. J Biol Chem 2011; 286:18650-7. [PMID: 21454700 PMCID: PMC3099681 DOI: 10.1074/jbc.m111.233015] [Citation(s) in RCA: 227] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2011] [Revised: 03/19/2011] [Indexed: 11/06/2022] Open
Abstract
Four-phosphate-adaptor protein 1 (FAPP1) regulates secretory transport from the trans-Golgi network (TGN) to the plasma membrane. FAPP1 is recruited to the Golgi through binding of its pleckstrin homology (PH) domain to phosphatidylinositol 4-phosphate (PtdIns(4)P) and a small GTPase ADP-ribosylation factor 1 (ARF1). Despite the critical role of FAPP1 in membrane trafficking, the molecular basis of its dual function remains unclear. Here, we report a 1.9 Å resolution crystal structure of the FAPP1 PH domain and detail the molecular mechanisms of the PtdIns(4)P and ARF1 recognition. The FAPP1 PH domain folds into a seven-stranded β-barrel capped by an α-helix at one edge, whereas the opposite edge is flanked by three loops and the β4 and β7 strands that form a lipid-binding pocket within the β-barrel. The ARF1-binding site is located on the outer side of the β-barrel as determined by NMR resonance perturbation analysis, mutagenesis, and measurements of binding affinities. The two binding sites have little overlap, allowing FAPP1 PH to associate with both ligands simultaneously and independently. Binding to PtdIns(4)P is enhanced in an acidic environment and is required for membrane penetration and tubulation activity of FAPP1, whereas the GTP-bound conformation of the GTPase is necessary for the interaction with ARF1. Together, these findings provide structural and biochemical insight into the multivalent membrane anchoring by the PH domain that may augment affinity and selectivity of FAPP1 toward the TGN membranes enriched in both PtdIns(4)P and GTP-bound ARF1.
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Affiliation(s)
- Ju He
- From the Department of Pharmacology, University of Colorado School of Medicine, Aurora, Colorado 80045
| | - Jordan L. Scott
- the Department of Chemistry and Biochemistry and the Walther Center for Cancer Research, University of Notre Dame, Notre Dame, Indiana 46556
| | - Annie Heroux
- the Department of Biology, Brookhaven National Laboratory, Upton, New York 11973, and
| | - Siddhartha Roy
- From the Department of Pharmacology, University of Colorado School of Medicine, Aurora, Colorado 80045
| | - Marc Lenoir
- the School of Cancer Sciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Michael Overduin
- the School of Cancer Sciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Robert V. Stahelin
- the Department of Chemistry and Biochemistry and the Walther Center for Cancer Research, University of Notre Dame, Notre Dame, Indiana 46556
- the Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, South Bend, Indiana 46617
| | - Tatiana G. Kutateladze
- From the Department of Pharmacology, University of Colorado School of Medicine, Aurora, Colorado 80045
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Kale SD, Gu B, Capelluto DGS, Dou D, Feldman E, Rumore A, Arredondo FD, Hanlon R, Fudal I, Rouxel T, Lawrence CB, Shan W, Tyler BM. External lipid PI3P mediates entry of eukaryotic pathogen effectors into plant and animal host cells. Cell 2010; 142:284-95. [PMID: 20655469 DOI: 10.1016/j.cell.2010.06.008] [Citation(s) in RCA: 291] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2009] [Revised: 03/30/2010] [Accepted: 05/10/2010] [Indexed: 10/19/2022]
Abstract
Pathogens of plants and animals produce effector proteins that are transferred into the cytoplasm of host cells to suppress host defenses. One type of plant pathogens, oomycetes, produces effector proteins with N-terminal RXLR and dEER motifs that enable entry into host cells. We show here that effectors of another pathogen type, fungi, contain functional variants of the RXLR motif, and that the oomycete and fungal RXLR motifs enable binding to the phospholipid, phosphatidylinositol-3-phosphate (PI3P). We find that PI3P is abundant on the outer surface of plant cell plasma membranes and, furthermore, on some animal cells. All effectors could also enter human cells, suggesting that PI3P-mediated effector entry may be very widespread in plant, animal and human pathogenesis. Entry into both plant and animal cells involves lipid raft-mediated endocytosis. Blocking PI3P binding inhibited effector entry, suggesting new therapeutic avenues.
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Affiliation(s)
- Shiv D Kale
- Virginia Bioinformatics Institute, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
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Abstract
Phosphoinositide (PI) lipids are essential components of eukaryotic cell membranes. They are produced by mono-, bis- and trisphosphorylation of the inositol headgroup of phosphatidylinositol (PtdIns) and are concentrated in separate pools of cytosolic membranes. PIs serve as markers of the cell compartments and form unique docking sites for protein effectors. Collectively, seven known PIs, the protein effectors that bind them and enzymes that generate or modify PIs compose a remarkably complex protein-lipid signaling network. A number of cytosolic proteins contain one or several effector modules capable of recognizing individual PIs and recruiting the host proteins to distinct intracellular compartment. The recently determined atomic-resolution structures and membrane-targeting mechanisms of a dozen PI effectors have provided insights into the molecular basis for regulation of endocytic membrane trafficking and signaling. In this review, I highlight the structural aspects of the deciphering of the 'PI code' by the most common PI-recognizing effectors and discuss the mechanistic details of their membrane anchoring.
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Abstract
Membrane fusion underlies many cellular events, including secretion, exocytosis, endocytosis, organelle reconstitution, transport from endoplasmic reticulum to Golgi and nuclear envelope formation. A large number of investigations into membrane fusion indicate various roles for individual members of the phosphoinositide class of membrane lipids. We first review the phosphoinositides as membrane recognition sites and their regulatory functions in membrane fusion. We then consider how modulation of phosphoinositides and their products may affect the structure and dynamics of natural membranes facilitating fusion. These diverse roles underscore the importance of these phospholipids in the fusion of biological membranes.
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32
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Saad JS, Ablan SD, Ghanam RH, Kim A, Andrews K, Nagashima K, Soheilian F, Freed EO, Summers MF. Structure of the myristylated human immunodeficiency virus type 2 matrix protein and the role of phosphatidylinositol-(4,5)-bisphosphate in membrane targeting. J Mol Biol 2008; 382:434-47. [PMID: 18657545 DOI: 10.1016/j.jmb.2008.07.027] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2008] [Revised: 07/10/2008] [Accepted: 07/10/2008] [Indexed: 11/25/2022]
Abstract
During the late phase of retroviral replication, newly synthesized Gag proteins are targeted to the plasma membrane (PM), where they assemble and bud to form immature virus particles. Membrane targeting by human immunodeficiency virus type 1 (HIV-1) Gag is mediated by the PM marker molecule phosphatidylinositol-(4,5)-bisphosphate [PI(4,5)P(2)], which is capable of binding to the matrix (MA) domain of Gag in an extended lipid conformation and of triggering myristate exposure. Here, we show that, as observed previously for HIV-1 MA, the myristyl group of HIV-2 MA is partially sequestered within a narrow hydrophobic tunnel formed by side chains of helices 1, 2, 3, and 5. However, the myristate of HIV-2 MA is more tightly sequestered than that of the HIV-1 protein and does not exhibit concentration-dependent exposure. Soluble PI(4,5)P(2) analogs containing truncated acyl chains bind HIV-2 MA and induce minor long-range structural changes but do not trigger myristate exposure. Despite these differences, the site of HIV-2 assembly in vivo can be manipulated by enzymes that regulate PI(4,5)P(2) localization. Our findings indicate that HIV-1 and HIV-2 are both targeted to the PM for assembly via a PI(4,5)P(2)-dependent mechanism, despite differences in the sensitivity of the MA myristyl switch, and suggest a potential mechanism that may contribute to the poor replication kinetics of HIV-2.
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Affiliation(s)
- Jamil S Saad
- Howard Hughes Medical Institute, Department of Chemistry and Biochemistry, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA
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33
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Bakrač B, Gutiérrez-Aguirre I, Podlesek Z, Sonnen AFP, Gilbert RJ, Maček P, Lakey JH, Anderluh G. Molecular Determinants of Sphingomyelin Specificity of a Eukaryotic Pore-forming Toxin. J Biol Chem 2008; 283:18665-77. [DOI: 10.1074/jbc.m708747200] [Citation(s) in RCA: 145] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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34
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He J, Haney RM, Vora M, Verkhusha VV, Stahelin RV, Kutateladze TG. Molecular mechanism of membrane targeting by the GRP1 PH domain. J Lipid Res 2008; 49:1807-15. [PMID: 18469301 DOI: 10.1194/jlr.m800150-jlr200] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The general receptor for phosphoinositides isoform 1 (GRP1) is recruited to the plasma membrane in response to activation of phosphoinositide 3-kinases and accumulation of phosphatidylinositol 3,4,5-trisphosphate [PtdIns(3,4,5)P(3)]. GRP1's pleckstrin homology (PH) domain recognizes PtdIns(3,4,5)P(3) with high specificity and affinity, however, the precise mechanism of its association with membranes remains unclear. Here, we detail the molecular basis of membrane anchoring by the GRP1 PH domain. Our data reveal a multivalent membrane docking involving PtdIns(3,4,5)P(3) binding, regulated by pH and facilitated by electrostatic interactions with other anionic lipids. The specific recognition of PtdIns(3,4,5)P(3) triggers insertion of the GRP1 PH domain into membranes. An acidic environment enhances PtdIns(3,4,5)P(3) binding and increases membrane penetration as demonstrated by NMR and monolayer surface tension and surface plasmon resonance experiments. The GRP1 PH domain displays a 28 nM affinity for POPC/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine/PtdIns(3,4,5)P(3) vesicles at pH 6.0, but binds 22-fold weaker at pH 8.0. The pH sensitivity is attributed in part to the His355 residue, protonation of which is required for the robust interaction with PtdIns(3,4,5)P(3) and significant membrane penetration, as illustrated by mutagenesis data. The binding affinity of the GRP1 PH domain for PtdIns(3,4,5)P(3)-containing vesicles is further amplified (by approximately 6-fold) by nonspecific electrostatic interactions with phosphatidylserine/phosphatidylinositol. Together, our results provide new insight into the multivalent mechanism of the membrane targeting and regulation of the GRP1 PH domain.
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Affiliation(s)
- Ju He
- Department of Pharmacology, University of Colorado Health Sciences Center, Aurora, CO, USA
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Dancea F, Kami K, Overduin M. Lipid interaction networks of peripheral membrane proteins revealed by data-driven micelle docking. Biophys J 2007; 94:515-24. [PMID: 17890395 PMCID: PMC2157223 DOI: 10.1529/biophysj.107.115923] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Many signaling and trafficking proteins contain modular domains that bind reversibly to cellular membranes. The structural basis of the intermolecular interactions which mediate these membrane-targeting events remains elusive since protein-membrane complexes are not directly accessible to standard structural biology techniques. Here we report a fast protein-micelle docking methodology that yields three-dimensional model structures of proteins inserted into micelles, revealing energetically favorable orientations, convergent insertion angles, and an array of protein-lipid interactions at atomic resolution. The method is applied to two peripheral membrane proteins, the early endosome antigen 1 (EEA1) FYVE (a zinc finger domain found in the proteins Fab1, YOTB/ZK632.12, Vac1, and EEA1) and Vam7p phagocyte oxidase homology domains, which are revealed to form extensive networks of interactions with multiple phospholipid headgroups and acyl chains. The resulting structural models explain extensive published mutagenesis data and reveal novel binding determinants. The docking restraints used here were based on NMR data, but can be derived from any technique that detects insertion of protein residues into a membrane, and can be applied to virtually any peripheral membrane protein or membrane-like structure.
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Affiliation(s)
- Felician Dancea
- Cancer Research UK Institute for Cancer Studies, University of Birmingham, Birmingham B15 2TT, United Kingdom
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36
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Blatner NR, Wilson MI, Lei C, Hong W, Murray D, Williams RL, Cho W. The structural basis of novel endosome anchoring activity of KIF16B kinesin. EMBO J 2007; 26:3709-19. [PMID: 17641687 PMCID: PMC1949010 DOI: 10.1038/sj.emboj.7601800] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2007] [Accepted: 06/26/2007] [Indexed: 12/26/2022] Open
Abstract
KIF16B is a newly identified kinesin that regulates the intracellular motility of early endosomes. KIF16B is unique among kinesins in that its cargo binding is mediated primarily by the strong interaction of its PX domain with endosomal lipids. To elucidate the structural basis of this unique endosomal anchoring activity of KIF16B-PX, we determined the crystal structure of the PX domain and performed in vitro and cellular membrane binding measurements for KIF16B-PX and mutants. The most salient structural feature of KIF16B-PX is that two neighboring residues, L1248 and F1249, on the membrane-binding surface form a protruding hydrophobic stalk with a large solvent-accessible surface area. This unique structure, arising from the complementary stacking of the two side chains and the local conformation, allows strong hydrophobic membrane interactions and endosome tethering. The presence of similar hydrophobic pairs in the amino-acid sequences of other membrane-binding domains and proteins suggests that the same structural motif may be shared by other membrane-binding proteins, whose physiological functions depend on strong hydrophobic membrane interactions.
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Affiliation(s)
- Nichole R Blatner
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL, USA
| | | | - Cai Lei
- Membrane Biology Laboratory, Institute of Molecular and Cell Biology, Singapore, Singapore
| | - Wanjin Hong
- Membrane Biology Laboratory, Institute of Molecular and Cell Biology, Singapore, Singapore
| | - Diana Murray
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, NY, USA
| | | | - Wonhwa Cho
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL, USA
- Department of Chemistry (M/C 111), University of Illinois at Chicago, 845 West Taylor Street, Chicago, IL 60607, USA. Tel.: +1 312 996 4883; Fax: +1 312 996 0431; E-mail:
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37
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Kutateladze TG. Mechanistic similarities in docking of the FYVE and PX domains to phosphatidylinositol 3-phosphate containing membranes. Prog Lipid Res 2007; 46:315-27. [PMID: 17707914 PMCID: PMC2211451 DOI: 10.1016/j.plipres.2007.06.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Phosphatidylinositol 3-phosphate [PtdIns(3)P], a phospholipid produced by PI 3-kinases in early endosomes and multivesicular bodies, often serves as a marker of endosomal membranes. PtdIns(3)P recruits and activates effector proteins containing the FYVE or PX domain and therefore regulates a variety of biological processes including endo- and exocytosis, membrane trafficking, protein sorting, signal transduction and cytoskeletal rearrangement. Structures and PtdIns(3)P binding modes of several FYVE and PX domains have recently been characterized, unveiling the molecular basis underlying multiple cellular functions of these proteins. Here, structural and functional aspects and current mechanisms of the multivalent membrane anchoring by the FYVE and PX domains are reviewed and compared.
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Affiliation(s)
- Tatiana G Kutateladze
- Department of Pharmacology, University of Colorado Health Sciences Center, Aurora, CO 80045, USA.
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38
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Stahelin RV, Karathanassis D, Murray D, Williams RL, Cho W. Structural and membrane binding analysis of the Phox homology domain of Bem1p: basis of phosphatidylinositol 4-phosphate specificity. J Biol Chem 2007; 282:25737-47. [PMID: 17581820 DOI: 10.1074/jbc.m702861200] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phox homology (PX) domains, which have been identified in a variety of proteins involved in cell signaling and membrane trafficking, have been shown to interact with phosphoinositides (PIs) with different affinities and specificities. To elucidate the structural origin of the diverse PI specificity of PX domains, we determined the crystal structure of the PX domain from Bem1p that has been reported to bind phosphatidylinositol 4-phosphate (PtdIns(4)P). We also measured the membrane binding properties of the PX domain and its mutants by surface plasmon resonance and monolayer techniques and calculated the electrostatic potentials for the PX domain in the absence and presence of bound PtdIns(4)P. The Bem1p PX domain contains a signature PI-binding site optimized for PtdIns(4)P binding and also harbors basic and hydrophobic residues on the membrane-binding surface. The membrane binding of the Bem1p PX domain is initiated by nonspecific electrostatic interactions between the cationic membrane-binding surface of the domain and anionic membrane surfaces, followed by the membrane penetration of hydrophobic residues. Unlike other PX domains, the Bem1p PX domain has high intrinsic membrane penetrating activity in the absence of PtdIns(4)P, suggesting that the partial membrane penetration may occur before specific PtdIns(4)P binding and last after the removal of PtdIns(4)P under certain conditions. This structural and functional study of the PtdIns(4)P-binding Bem1p PX domain provides new insight into the diverse PI specificities and membrane-binding mechanisms of PX domains.
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Affiliation(s)
- Robert V Stahelin
- Department of Chemistry, University of Illinois, Chicago, Illinois 60607-7061, USA
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