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Campbell O, Monje-Galvan V. Protein-driven membrane remodeling: Molecular perspectives from Flaviviridae infections. Biophys J 2023; 122:1890-1899. [PMID: 36369756 PMCID: PMC10257083 DOI: 10.1016/j.bpj.2022.11.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 10/23/2022] [Accepted: 11/07/2022] [Indexed: 11/13/2022] Open
Abstract
The mammalian cell membrane consists of thousands of different lipid species, and this variety is critical for biological function. Alterations to this balance can be dangerous as they can lead to permanent disruption of lipid metabolism, a hallmark in several viral diseases. The Flaviviridae family is made up of positive single-stranded RNA viruses that assemble at or near the location of lipid droplet formation in the endoplasmic reticulum. These viruses are known to interfere with lipid metabolism during the onset of liver disease, albeit to different extents. Pathogenesis of these infections involves specific protein-lipid interactions that alter lipid sorting and metabolism to sustain propagation of the viral infection. Recent experimental studies identify a correlation between viral proteins and lipid content or location in the cell, but these do not assess membrane-embedded interactions. Molecular modeling, specifically molecular dynamics simulations, can provide molecular-level spatial and temporal resolution for characterization of biomolecular interactions. This review focuses on recent advancements and current knowledge gaps in the molecular mechanisms of lipid-mediated liver disease preceded by viral infection. We discuss three viruses from the Flaviviridae family: dengue, zika, and hepatitis C, with a particular focus on lipid interactions with their respective ion channels, known as viroporins.
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Affiliation(s)
- Oluwatoyin Campbell
- Department of Chemical and Biological Engineering, University at Buffalo, Buffalo, New York
| | - Viviana Monje-Galvan
- Department of Chemical and Biological Engineering, University at Buffalo, Buffalo, New York.
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2
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Membrane protein assembly: two cytoplasmic phosphorylated serine sites of Vpu from HIV-1 affect oligomerization. Sci Rep 2016; 6:28866. [PMID: 27353136 PMCID: PMC4926278 DOI: 10.1038/srep28866] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Accepted: 06/06/2016] [Indexed: 11/08/2022] Open
Abstract
Viral protein U (Vpu) encoded by human immunodeficiency virus type 1 (HIV-1) is a short integral membrane protein which is known to self-assemble within the lipid membrane and associate with host factors during the HIV-1 infectivity cycle. In this study, full-length Vpu (M group) from clone NL4-3 was over-expressed in human cells and purified in an oligomeric state. Various single and double mutations were constructed on its phosphorylation sites to mimic different degrees of phosphorylation. Size exclusion chromatography of wild-type Vpu and mutants indicated that the smallest assembly unit of Vpu was a dimer and over time Vpu formed higher oligomers. The rate of oligomerization increased when (i) the degree of phosphorylation at serines 52 and 56 was decreased and (ii) when the ionic strength was increased indicating that the cytoplasmic domain of Vpu affects oligomerization. Coarse-grained molecular dynamic simulations with models of wild-type and mutant Vpu in a hydrated lipid bilayer supported the experimental data in demonstrating that, in addition to a previously known role in downregulation of host factors, the phosphorylation sites of Vpu also modulate oligomerization.
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Kalita MM, Fischer WB. Asymmetric dynamics of ion channel forming proteins - Hepatitis C virus (HCV) p7 bundles. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:1462-70. [PMID: 27079148 DOI: 10.1016/j.bbamem.2016.04.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 04/07/2016] [Accepted: 04/08/2016] [Indexed: 01/01/2023]
Abstract
Protein p7 of hepatitis C virus (HCV) is a short 63 amino acid membrane protein which homo-oligomerises in the lipid membrane to form ion and proton conducting bundles. Two different genotypes (GTs) of p7, 1a and 5a, are used to simulate hexameric bundles of the protein embedded in a fully hydrated lipid bilayer during 400 ns molecular dynamics (MD) simulations. Whilst the bundle of GT 1a is based on a fully computational derived structure, the bundle of GT 5a is based on NMR spectroscopic data. Results of a full correlation analysis (FCA) reveal that albeit structural differences both bundles screen local minima during the simulation. The collective motion of the protein domains is asymmetric. No 'breathing-mode'-like dynamics is observed. The presence of divalent ions, such as Ca-ions affects the dynamics of especially solvent exposed parts of the protein, but leaves the asymmetric domain motion unaffected.
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Affiliation(s)
- Monoj Mon Kalita
- Institute of Biophotonics and Biophotonics and Molecular Imaging Research Center (BMIRC), School of Biomedical Science and Engineering, National Yang-Ming University, Taipei, Taiwan, ROC
| | - Wolfgang B Fischer
- Institute of Biophotonics and Biophotonics and Molecular Imaging Research Center (BMIRC), School of Biomedical Science and Engineering, National Yang-Ming University, Taipei, Taiwan, ROC.
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Fischer WB, Kalita MM, Heermann D. Viral channel forming proteins--How to assemble and depolarize lipid membranes in silico. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:1710-21. [PMID: 26806161 PMCID: PMC7094687 DOI: 10.1016/j.bbamem.2016.01.018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Revised: 01/14/2016] [Accepted: 01/18/2016] [Indexed: 01/23/2023]
Abstract
Viral channel forming proteins (VCPs) have been discovered in the late 70s and are found in many viruses to date. Usually they are small and have to assemble to form channels which depolarize the lipid membrane of the host cells. Structural information is just about to emerge for just some of them. Thus, computational methods play a pivotal role in generating plausible structures which can be used in the drug development process. In this review the accumulation of structural data is introduced from a historical perspective. Computational performances and their predictive power are reported guided by biological questions such as the assembly, mechanism of function and drug–protein interaction of VCPs. An outlook of how coarse grained simulations can contribute to yet unexplored issues of these proteins is given. This article is part of a Special Issue entitled: Membrane Proteins edited by J.C. Gumbart and Sergei Noskov. Early references about the discovery of viral channel forming proteins. Latest structural information about the class of proteins. Identification of structural motifs, assembly mechanism of function and drug action using computational methods. Outlook for the use of coarse grained techniques to address assembly and integration into cellular processes.
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Affiliation(s)
- Wolfgang B Fischer
- Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, Taipei 112, Taiwan; Biophotonics & Molecular Imaging Center (BMIRC), National Yang-Ming University, Taipei 112, Taiwan.
| | - Monoj Mon Kalita
- Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, Taipei 112, Taiwan; Biophotonics & Molecular Imaging Center (BMIRC), National Yang-Ming University, Taipei 112, Taiwan
| | - Dieter Heermann
- Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, Taipei 112, Taiwan; Biophotonics & Molecular Imaging Center (BMIRC), National Yang-Ming University, Taipei 112, Taiwan
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Martinez-Gil L, Mingarro I. Viroporins, Examples of the Two-Stage Membrane Protein Folding Model. Viruses 2015; 7:3462-82. [PMID: 26131957 PMCID: PMC4517110 DOI: 10.3390/v7072781] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Revised: 06/15/2015] [Accepted: 06/17/2015] [Indexed: 12/21/2022] Open
Abstract
Viroporins are small, α-helical, hydrophobic virus encoded proteins, engineered to form homo-oligomeric hydrophilic pores in the host membrane. Viroporins participate in multiple steps of the viral life cycle, from entry to budding. As any other membrane protein, viroporins have to find the way to bury their hydrophobic regions into the lipid bilayer. Once within the membrane, the hydrophobic helices of viroporins interact with each other to form higher ordered structures required to correctly perform their porating activities. This two-step process resembles the two-stage model proposed for membrane protein folding by Engelman and Poppot. In this review we use the membrane protein folding model as a leading thread to analyze the mechanism and forces behind the membrane insertion and folding of viroporins. We start by describing the transmembrane segment architecture of viroporins, including the number and sequence characteristics of their membrane-spanning domains. Next, we connect the differences found among viroporin families to their viral genome organization, and finalize focusing on the pathways used by viroporins in their way to the membrane and on the transmembrane helix-helix interactions required to achieve proper folding and assembly.
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Affiliation(s)
- Luis Martinez-Gil
- Department of Biochemistry and Molecular Biology, ERI BioTecMed, University of Valencia, Dr. Moliner 50, 46100 Burjassot, Spain.
| | - Ismael Mingarro
- Department of Biochemistry and Molecular Biology, ERI BioTecMed, University of Valencia, Dr. Moliner 50, 46100 Burjassot, Spain.
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Padhi S, Ramakrishna S, Priyakumar UD. Prediction of the structures of helical membrane proteins based on a minimum unfavorable contacts approach. J Comput Chem 2015; 36:539-52. [PMID: 25565454 DOI: 10.1002/jcc.23828] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Revised: 11/20/2014] [Accepted: 11/21/2014] [Indexed: 11/12/2022]
Abstract
An understanding of structure-function relationships of membrane proteins continues to be a challenging problem, owing to the difficulty in obtaining their structures experimentally. This study suggests a method for modeling membrane protein structures that can be used to generate a reliable initial conformation prior to the use of other approaches for sampling conformations. It involves optimizing the orientation of hydrophilic residues so as to minimize unfavorable contacts with the hydrophobic tails of the lipid bilayer. Starting with the optimized initial conformation for three different proteins modeled based on this method, two independent approaches have been used for sampling the conformational space of the proteins. Both approaches are able to predict structures reasonably close to experimental structures, indicating that the initial structure enables the sampling of conformations that are close to the native structure. Possible improvements in the method for making it broadly applicable to helical membrane proteins are discussed.
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Affiliation(s)
- Siladitya Padhi
- Centre for Computational Natural Sciences and Bioinformatics, International Institute of Information Technology, Hyderabad, 500032, India
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Atomistic detailed mechanism and weak cation-conducting activity of HIV-1 Vpu revealed by free energy calculations. PLoS One 2014; 9:e112983. [PMID: 25392993 PMCID: PMC4231112 DOI: 10.1371/journal.pone.0112983] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2014] [Accepted: 10/20/2014] [Indexed: 12/02/2022] Open
Abstract
The viral protein U (Vpu) encoded by HIV-1 has been shown to assist in the detachment of virion particles from infected cells. Vpu forms cation-specific ion channels in host cells, and has been proposed as a potential drug target. An understanding of the mechanism of ion transport through Vpu is desirable, but remains limited because of the unavailability of an experimental structure of the channel. Using a structure of the pentameric form of Vpu – modeled and validated based on available experimental data – umbrella sampling molecular dynamics simulations (cumulative simulation time of more than 0.4 µs) were employed to elucidate the energetics and the molecular mechanism of ion transport in Vpu. Free energy profiles corresponding to the permeation of Na+ and K+ were found to be similar to each other indicating lack of ion selection, consistent with previous experimental studies. The Ser23 residue is shown to enhance ion transport via two mechanisms: creating a weak binding site, and increasing the effective hydrophilic length of the channel, both of which have previously been hypothesized in experiments. A two-dimensional free energy landscape has been computed to model multiple ion permeation, based on which a mechanism for ion conduction is proposed. It is shown that only one ion can pass through the channel at a time. This, along with a stretch of hydrophobic residues in the transmembrane domain of Vpu, explains the slow kinetics of ion conduction. The results are consistent with previous conductance studies that showed Vpu to be a weakly conducting ion channel.
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Ahn S, Lim G, Nam S, Lee J. Structural modeling of Vpu from HIV-1 based on solid-state NMR observables. Chem Phys Lett 2014. [DOI: 10.1016/j.cplett.2014.03.033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Li LH, Hsu HJ, Fischer WB. Qualitative computational bioanalytics: assembly of viral channel-forming peptides around mono and divalent ions. Biochem Biophys Res Commun 2013; 442:85-91. [PMID: 24239548 DOI: 10.1016/j.bbrc.2013.11.017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2013] [Accepted: 11/03/2013] [Indexed: 01/20/2023]
Abstract
A fine-grained docking protocol was used to generate a bundle-like structure of the bitopic membrane protein Vpu from HIV-1. Vpu is a type I membrane protein with 81 amino acids. It is proposed that Vpu forms ion- and substrate-conducting bundles, which are located at the plasma membrane in the infected cell. The Vpu1-32 peptide that includes the transmembrane domain (TMD) is assembled into homo-pentameric bundles around prepositioned Na, K, Ca or Cl ions. For bundles with the lowest energy, the TMDs generate a hydrophobic pore. Bundles in which Ser-24 faces the pore have higher energy. The tilt of the helices in the lowest energy bundles is larger than bundles with serines facing the pore. Left-handed bundles are lowest in energy where the ions are located at the serines.
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Affiliation(s)
- Li-Hua Li
- Institute of Biophotonics, School of Biomedical Science and Engineering, Biophotonics & Molecular Imaging Research Center (BMIRC), National Yang-Ming University, Taipei 112, Taiwan
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Viral channel proteins in intracellular protein-protein communication: Vpu of HIV-1, E5 of HPV16 and p7 of HCV. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:1113-21. [PMID: 24035804 DOI: 10.1016/j.bbamem.2013.08.017] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Revised: 08/06/2013] [Accepted: 08/09/2013] [Indexed: 01/20/2023]
Abstract
Viral channel forming proteins are known for their capability to make the lipid membrane of the host cell and its subcellular compartments permeable to ions and small compounds. There is increasing evidence that some of the representatives of this class of proteins are also strongly interacting with host proteins and the effectiveness of this interaction seems to be high. Interaction of viral channel proteins with host factors has been proposed by bioinformatics approaches and has also been identified experimentally. An overview of the interactions with host proteins is given for Vpu from HIV-1, E5 from HPV-16 and p7 from HCV. This article is part of a Special Issue entitled: Viral Membrane Proteins - Channels for Cellular Networking.
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Lin MH, Hsu HJ, Bartenschlager R, Fischer WB. Membrane undulation induced by NS4A of Dengue virus: a molecular dynamics simulation study. J Biomol Struct Dyn 2013; 32:1552-62. [PMID: 23964591 DOI: 10.1080/07391102.2013.826599] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Nonstructural protein 4A (NS4A) of Dengue virus (DENV) is a membrane protein involved in rearrangements of the endoplasmic reticulum membrane that are required for formation of replication vesicles. NS4A is composed most likely of three membrane domains. The N- and C-terminal domains are supposed to traverse the lipid membrane whereas the central one is thought to reside on the membrane surface, thus forming a u-shaped protein. All three membrane domains are proposed to be helical by secondary structure prediction programs. After performing multi nanosecond molecular dynamics (MD) simulations at various temperatures (300, 310, and 315.15 K) with each of the individual domains, they are used in a docking approach to define putative association motifs of the transmembrane domains (TMDs). Two structures of the u-shaped protein are generated by separating two assembled TMDs linking them with the membrane-attached domain. Lipid undulation is monitored with the structures embedded in a fully hydrated lipid bilayer applying multiple 200 ns MD simulations at 310 K. An intact structure of the protein supports membrane undulation. The strong unwinding of the helices in the domain-linking section of one of the structures lowers its capability to induce membrane curvature. Unwinding of the link region is due to interactions of two tryptophan residues, Trp-96 and 104. These results provide first insights into the membrane-altering properties of DENV NS4A.
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Affiliation(s)
- Meng-Han Lin
- a Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University and Biophotonics & Molecular Imaging Research Center (BMIRC), National Yang-Ming University , 155, Li-Non St., Sec. 2, Taipei , 112 , Taiwan
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