1
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Huster D, Maiti S, Herrmann A. Phospholipid Membranes as Chemically and Functionally Tunable Materials. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2312898. [PMID: 38456771 DOI: 10.1002/adma.202312898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Revised: 02/12/2024] [Indexed: 03/09/2024]
Abstract
The sheet-like lipid bilayer is the fundamental structural component of all cell membranes. Its building blocks are phospholipids and cholesterol. Their amphiphilic structure spontaneously leads to the formation of a bilayer in aqueous environment. Lipids are not just structural elements. Individual lipid species, the lipid membrane structure, and lipid dynamics influence and regulate membrane protein function. An exciting field is emerging where the membrane-associated material properties of different bilayer systems are used in designing innovative solutions for widespread applications across various fields, such as the food industry, cosmetics, nano- and biomedicine, drug storage and delivery, biotechnology, nano- and biosensors, and computing. Here, the authors summarize what is known about how lipids determine the properties and functions of biological membranes and how this has been or can be translated into innovative applications. Based on recent progress in the understanding of membrane structure, dynamics, and physical properties, a perspective is provided on how membrane-controlled regulation of protein functions can extend current applications and even offer new applications.
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Affiliation(s)
- Daniel Huster
- Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16/18, D-04107, Leipzig, Germany
| | - Sudipta Maiti
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai, 400 005, India
| | - Andreas Herrmann
- Freie Universität Berlin, Department Chemistry and Biochemistry, SupraFAB, Altensteinstr. 23a, D-14195, Berlin, Germany
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2
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Farcas A, Janosi L. GTP-Bound N-Ras Conformational States and Substates Are Modulated by Membrane and Point Mutation. Int J Mol Sci 2024; 25:1430. [PMID: 38338709 PMCID: PMC11154311 DOI: 10.3390/ijms25031430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Revised: 01/11/2024] [Accepted: 01/17/2024] [Indexed: 02/12/2024] Open
Abstract
Oncogenic Ras proteins are known to present multiple conformational states, as reported by the great variety of crystallographic structures. The GTP-bound states are grouped into two main states: the "inactive" state 1 and the "active" state 2. Recent reports on H-Ras have shown that state 2 exhibits two substates, directly related to the orientation of Tyr32: toward the GTP-bound pocket and outwards. In this paper, we show that N-Ras exhibits another substate of state 2, related to a third orientation of Tyr32, toward Ala18 and parallel to the GTP-bound pocket. We also show that this substate is highly sampled in the G12V mutation of N-Ras and barely present in its wild-type form, and that the G12V mutation prohibits the sampling of the GTPase-activating protein (GAP) binding substate, rendering this mutation oncogenic. Furthermore, using molecular dynamics simulations, we explore the importance of the membrane on N-Ras' conformational state dynamics and its strong influence on Ras protein stability. Moreover, the membrane has a significant influence on the conformational (sub)states sampling of Ras. This, in turn, is of crucial importance in the activation/deactivation cycle of Ras, due to the binding of guanine nucleotide exchange factor proteins (GEFs)/GTPase-activating proteins (GAPs).
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Affiliation(s)
| | - Lorant Janosi
- Department of Molecular and Biomolecular Physics, National Institute for Research and Development of Isotopic and Molecular Technologies, 67-103 Donat Street, 400293 Cluj-Napoca, Romania;
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3
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Zhang Y, Soubias O, Pant S, Heinrich F, Vogel A, Li J, Li Y, Clifton LA, Daum S, Bacia K, Huster D, Randazzo PA, Lösche M, Tajkhorshid E, Byrd RA. Myr-Arf1 conformational flexibility at the membrane surface sheds light on the interactions with ArfGAP ASAP1. Nat Commun 2023; 14:7570. [PMID: 37989735 PMCID: PMC10663523 DOI: 10.1038/s41467-023-43008-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Accepted: 10/30/2023] [Indexed: 11/23/2023] Open
Abstract
ADP-ribosylation factor 1 (Arf1) interacts with multiple cellular partners and membranes to regulate intracellular traffic, organelle structure and actin dynamics. Defining the dynamic conformational landscape of Arf1 in its active form, when bound to the membrane, is of high functional relevance and key to understanding how Arf1 can alter diverse cellular processes. Through concerted application of nuclear magnetic resonance (NMR), neutron reflectometry (NR) and molecular dynamics (MD) simulations, we show that, while Arf1 is anchored to the membrane through its N-terminal myristoylated amphipathic helix, the G domain explores a large conformational space, existing in a dynamic equilibrium between membrane-associated and membrane-distal conformations. These configurational dynamics expose different interfaces for interaction with effectors. Interaction with the Pleckstrin homology domain of ASAP1, an Arf-GTPase activating protein (ArfGAP), restricts motions of the G domain to lock it in what seems to be a conformation exposing functionally relevant regions.
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Affiliation(s)
- Yue Zhang
- Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702-1201, USA
- Ring Therapeutics, Inc., Cambridge, MA, USA
| | - Olivier Soubias
- Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702-1201, USA
| | - Shashank Pant
- Theoretical and Computational Biophysics Group, NIH Center for Macromolecular Modeling and Visualization, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
- Loxo Oncology at Lilly, Louisville, CO, USA
| | - Frank Heinrich
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA, USA
- NIST Center for Neutron Research, Gaithersburg, MD, USA
| | - Alexander Vogel
- Institute of Medical Physics and Biophysics, University of Leipzig, 04107, Leipzig, Germany
| | - Jess Li
- Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702-1201, USA
| | - Yifei Li
- Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702-1201, USA
- Vonsun Pharmatech Co., Ltd., Suzhou, China
| | - Luke A Clifton
- ISIS Neutron and Muon Source, Rutherford Appleton Laboratory, Didcot, Oxfordshire, OX11 0QX, UK
| | - Sebastian Daum
- Institute for Chemistry, Department of Biophysical Chemistry, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Str. 3A, 06120, Halle, Germany
| | - Kirsten Bacia
- Institute for Chemistry, Department of Biophysical Chemistry, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Str. 3A, 06120, Halle, Germany
| | - Daniel Huster
- Institute of Medical Physics and Biophysics, University of Leipzig, 04107, Leipzig, Germany
| | - Paul A Randazzo
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Mathias Lösche
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA, USA
- NIST Center for Neutron Research, Gaithersburg, MD, USA
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Emad Tajkhorshid
- Theoretical and Computational Biophysics Group, NIH Center for Macromolecular Modeling and Visualization, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - R Andrew Byrd
- Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702-1201, USA.
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4
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López CA, Agarwal A, Van QN, Stephen AG, Gnanakaran S. Unveiling the Dynamics of KRAS4b on Lipid Model Membranes. J Membr Biol 2021; 254:201-216. [PMID: 33825026 PMCID: PMC8052243 DOI: 10.1007/s00232-021-00176-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Accepted: 03/16/2021] [Indexed: 12/23/2022]
Abstract
Small GTPase proteins are ubiquitous and responsible for regulating several processes related to cell growth and differentiation. Mutations that stabilize their active state can lead to uncontrolled cell proliferation and cancer. Although these proteins are well characterized at the cellular scale, the molecular mechanisms governing their functions are still poorly understood. In addition, there is limited information about the regulatory function of the cell membrane which supports their activity. Thus, we have studied the dynamics and conformations of the farnesylated KRAS4b in various membrane model systems, ranging from binary fluid mixtures to heterogeneous raft mimics. Our approach combines long time-scale coarse-grained (CG) simulations and Markov state models to dissect the membrane-supported dynamics of KRAS4b. Our simulations reveal that protein dynamics is mainly modulated by the presence of anionic lipids and to some extent by the nucleotide state (activation) of the protein. In addition, our results suggest that both the farnesyl and the polybasic hypervariable region (HVR) are responsible for its preferential partitioning within the liquid-disordered (Ld) domains in membranes, potentially enhancing the formation of membrane-driven signaling platforms.
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Affiliation(s)
- Cesar A López
- Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
| | - Animesh Agarwal
- Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Que N Van
- National Cancer Institute RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Inc., Frederick, MD, 21702, USA
| | - Andrew G Stephen
- National Cancer Institute RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Inc., Frederick, MD, 21702, USA
| | - S Gnanakaran
- Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
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5
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Herzog M, Li L, Blesken CC, Welsing G, Tiso T, Blank LM, Winter R. Impact of the number of rhamnose moieties of rhamnolipids on the structure, lateral organization and morphology of model biomembranes. SOFT MATTER 2021; 17:3191-3206. [PMID: 33621291 DOI: 10.1039/d0sm01934h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Various studies have described remarkable biological activities and surface-active properties of rhamnolipids, leading to their proposed use in a wide range of industrial applications. Here, we report on a study of the effects of monorhamnolipid RhaC10C10 and dirhamnolipid RhaRhaC10C10 incorporation into model membranes of varying complexity, including bacterial and heterogeneous model biomembranes. For comparison, we studied the effect of HAA (C10C10, lacking a sugar headgroup) partitioning into these membrane systems. AFM, confocal fluorescence microscopy, DSC, and Laurdan fluorescence spectroscopy were employed to yield insights into the rhamnolipid-induced morphological changes of lipid vesicles as well as modifications of the lipid order and lateral membrane organization of the model biomembranes upon partitioning of the different rhamnolipids. The partitioning of the three rhamnolipids into phospholipid bilayers changes the phase behavior, fluidity, lateral lipid organization and morphology of the phospholipid membranes dramatically, to what extent, depends on the headgroup structure of the rhamnolipid, which affects its packing and hydrogen bonding capacity. The incorporation into giant unilamellar vesicles (GUVs) of a heterogeneous anionic raft membrane system revealed budding of domains and fission of daughter vesicles and small aggregates for all three rhamnolipids, with major destabilization of the lipid vesicles upon insertion of RhaC10C10, and also formation of huge GUVs upon the incorporation of RhaRhaC10C10. Finally, we discuss the results with regard to the role these biosurfactants play in biology and their possible impact on applications, ranging from agricultural to pharmaceutical industries.
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Affiliation(s)
- Marius Herzog
- Physical Chemistry I - Biophysical Chemistry, Faculty of Chemistry and Chemical Biology, TU Dortmund University, Otto-Hahn Street 4a, 44227 Dortmund, Germany.
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6
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Busquets-Hernández C, Triola G. Palmitoylation as a Key Regulator of Ras Localization and Function. Front Mol Biosci 2021; 8:659861. [PMID: 33816563 PMCID: PMC8010249 DOI: 10.3389/fmolb.2021.659861] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Accepted: 02/22/2021] [Indexed: 11/27/2022] Open
Abstract
Ras proteins require membrane association for proper function. This process is tightly regulated by reversible palmitoylation that controls not only the distribution over different subcellular compartments but also Ras compartmentalization within membrane subdomains. As a result, there is a growing interest in protein palmitoylation and the enzymes that control this process. In this minireview, we discuss how palmitoylation affects the localization and function of Ras proteins. A better understanding of the regulatory mechanism controlling protein lipidation is expected to provide new insights into the functional role of these modifications and may ultimately lead to the development of novel therapeutic approaches.
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Affiliation(s)
| | - Gemma Triola
- Department of Biological Chemistry, Laboratory of Chemical Biology, Institute of Advanced Chemistry of Catalonia (IQAC-CSIC), Barcelona, Spain
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7
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Engberg O, Bochicchio A, Brandner AF, Gupta A, Dey S, Böckmann RA, Maiti S, Huster D. Serotonin Alters the Phase Equilibrium of a Ternary Mixture of Phospholipids and Cholesterol. Front Physiol 2020; 11:578868. [PMID: 33192582 PMCID: PMC7645218 DOI: 10.3389/fphys.2020.578868] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 10/06/2020] [Indexed: 12/20/2022] Open
Abstract
Unsaturated and saturated phospholipids tend to laterally segregate, especially in the presence of cholesterol. Small molecules such as neurotransmitters, toxins, drugs etc. possibly modulate this lateral segregation. The small aromatic neurotransmitter serotonin (5-HT) has been found to bind to membranes. We studied the lipid structure and packing of a ternary membrane mixture consisting of palmitoyl-oleoyl-phosphatidylcholine, palmitoyl-sphingomyelin, and cholesterol at a molar ratio of 4/4/2 in the absence and in the presence of 5-HT, using a combination of solid-state 2H NMR, atomic force microscopy, and atomistic molecular dynamics (MD) simulations. Both NMR and MD report formation of a liquid ordered (L o ) and a liquid disordered (L d ) phase coexistence with small domains. Lipid exchange between the domains was fast such that single component 2H NMR spectra are detected over a wide temperature range. A drastic restructuring of the domains was induced when 5-HT is added to the membranes at a 9 mol% concentration relative to the lipids. 2H NMR spectra of all components of the mixture showed two prominent contributions indicative of molecules of the same kind residing both in the disordered and the ordered phase. Compared to the data in the absence of 5-HT, the lipid chain order in the disordered phase was further decreased in the presence of 5-HT. Likewise, addition of serotonin increased lipid chain order within the ordered phase. These characteristic lipid chain order changes were confirmed by MD simulations. The 5-HT-induced larger difference in lipid chain order results in more pronounced differences in the hydrophobic thickness of the individual membrane domains. The correspondingly enlarged hydrophobic mismatch between ordered and disordered phases is assumed to increase the line tension at the domain boundary, which drives the system into formation of larger size domains. These results not only demonstrate that small membrane binding molecules such as neurotransmitters have a profound impact on essential membrane properties. It also suggests a mechanism by which the interaction of small molecules with membranes can influence the function of membrane proteins and non-cognate receptors. Altered membrane properties may modify lateral sorting of membrane protein, membrane protein conformation, and thus influence their function as suspected for neurotransmitters, local anesthetics, and other small drug molecules.
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Affiliation(s)
- Oskar Engberg
- Institute for Medical Physics and Biophysics, University of Leipzig, Leipzig, Germany
| | - Anna Bochicchio
- Computational Biology, Department of Biology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Astrid F. Brandner
- Computational Biology, Department of Biology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Ankur Gupta
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai, India
| | - Simli Dey
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai, India
| | - Rainer A. Böckmann
- Computational Biology, Department of Biology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Sudipta Maiti
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai, India
| | - Daniel Huster
- Institute for Medical Physics and Biophysics, University of Leipzig, Leipzig, Germany
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai, India
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8
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Hutchison JM, Shih KC, Scheidt HA, Fantin SM, Parson KF, Pantelopulos GA, Harrington HR, Mittendorf KF, Qian S, Stein RA, Collier SE, Chambers MG, Katsaras J, Voehler MW, Ruotolo BT, Huster D, McFeeters RL, Straub JE, Nieh MP, Sanders CR. Bicelles Rich in both Sphingolipids and Cholesterol and Their Use in Studies of Membrane Proteins. J Am Chem Soc 2020; 142:12715-12729. [PMID: 32575981 DOI: 10.1021/jacs.0c04669] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
How the distinctive lipid composition of mammalian plasma membranes impacts membrane protein structure is largely unexplored, partly because of the dearth of isotropic model membrane systems that contain abundant sphingolipids and cholesterol. This gap is addressed by showing that sphingomyelin and cholesterol-rich (SCOR) lipid mixtures with phosphatidylcholine can be cosolubilized by n-dodecyl-β-melibioside to form bicelles. Small-angle X-ray and neutron scattering, as well as cryo-electron microscopy, demonstrate that these assemblies are stable over a wide range of conditions and exhibit the bilayered-disc morphology of ideal bicelles even at low lipid-to-detergent mole ratios. SCOR bicelles are shown to be compatible with a wide array of experimental techniques, as applied to the transmembrane human amyloid precursor C99 protein in this medium. These studies reveal an equilibrium between low-order oligomer structures that differ significantly from previous experimental structures of C99, providing an example of how ordered membranes alter membrane protein structure.
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Affiliation(s)
- James M Hutchison
- Chemical and Physical Biology Graduate Program and Center for Structural Biology, Vanderbilt University, Nashville 37240, Tennessee, United States
| | - Kuo-Chih Shih
- Polymer Program, Department of Chemical & Biomolecular Engineering, and Department of Biomedical Engineering, University of Connecticut, Storrs 06269, Connecticut, United States
| | - Holger A Scheidt
- Institute for Medical Physics and Biophysics, Leipzig University, Leipzig 16-18, 04107, Germany
| | - Sarah M Fantin
- Department of Chemistry, University of Michigan, Ann Arbor 48109, Michigan, United States
| | - Kristine F Parson
- Department of Chemistry, University of Michigan, Ann Arbor 48109, Michigan, United States
| | - George A Pantelopulos
- Department of Chemistry, Boston University, Boston 02215, Massachusetts, United States
| | - Haley R Harrington
- Center for Structural Biology and Department of Biochemistry, Vanderbilt University School of Medicine Basic Sciences, Nashville 37240, Tennessee, United States
| | - Kathleen F Mittendorf
- Center for Health Research, Kaiser Permanente, Portland 97227, Oregon, United States
| | - Shuo Qian
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge 37831, Tennessee, United States
| | - Richard A Stein
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville37240, Tennessee, United States
| | - Scott E Collier
- Department of Translational and Applied Genomics, Center for Health Research, Kaiser Permanente Northwest, Portland 97227, Oregon, United States
| | - Melissa G Chambers
- Center for Structural Biology, Vanderbilt University, Nashville 37240, Tennessee, United States
| | - John Katsaras
- Neutron Scattering Division and Shull Wollan Center, Oak Ridge National Laboratory, Oak Ridge 37831, Tennessee, United States
| | - Markus W Voehler
- Center for Structural Biology and Department of Chemistry, Vanderbilt University, Nashville 37240, Tennessee, United States
| | - Brandon T Ruotolo
- Department of Chemistry, University of Michigan, Ann Arbor 48109, Michigan, United States
| | - Daniel Huster
- Institute for Medical Physics and Biophysics, Leipzig University, Leipzig 16-18, 04107, Germany
| | - Robert L McFeeters
- Department of Chemistry, University of Alabama, Huntsville 35899, Alabama, United States
| | - John E Straub
- Department of Chemistry, Boston University, Boston 02215, Massachusetts, United States
| | - Mu-Ping Nieh
- Polymer Program, Department of Chemical & Biomolecular Engineering, and Department of Biomedical Engineering, University of Connecticut, Storrs 06269, Connecticut, United States
| | - Charles R Sanders
- Center for Structural Biology, Department of Biochemistry, and Department of Medicine, Vanderbilt University School of Medicine, Nashville 37240, Tennessee, United States
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Schulte-Zweckel J, Dwivedi M, Brockmeyer A, Janning P, Winter R, Triola G. A hydroxylamine probe for profiling S-acylated fatty acids on proteins. Chem Commun (Camb) 2019; 55:11183-11186. [PMID: 31465055 DOI: 10.1039/c9cc05989j] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Reversible S-palmitoylation is a key regulatory mechanism of protein function and localization. There is increasing evidence that S-acylation is not restricted to palmitate but it includes shorter, longer, and unsaturated fatty acids. However, the diversity of this protein modification has not been fully explored. Herein, we report a chemical probe that combined with MS-based analysis allows the rapid detection and quantification of fatty acids linked to proteins. We have used this approach to profile the S-acylome and to show that the oncogene N-Ras is heterogeneously acylated with palmitate and palmitoleate. Studies on protein distribution in membrane subdomains with semisynthetic proteins revealed that unsaturated N-Ras presents an increased tendency toward clustering and higher insertion kinetic rate constants.
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Affiliation(s)
- Janine Schulte-Zweckel
- Department of Chemical Biology, Max-Planck-Institute of molecular Physiology, Otto-Hahn-Strasse 11, D-44227 Dortmund, Germany
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10
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Bosse M, Sibold J, Scheidt HA, Patalag LJ, Kettelhoit K, Ries A, Werz DB, Steinem C, Huster D. Shiga toxin binding alters lipid packing and the domain structure of Gb 3-containing membranes: a solid-state NMR study. Phys Chem Chem Phys 2019; 21:15630-15638. [PMID: 31268447 DOI: 10.1039/c9cp02501d] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
We studied the influence of globotriaosylceramide (Gb3) lipid molecules on the properties of phospholipid membranes composed of a liquid ordered (lo)/liquid disordered (ld) phase separated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/N-palmitoyl-d-erythro-sphingosylphosphorylcholine (PSM)/cholesterol mixture (40/35/20, mol/mol/mol) supplemented with 5 mol% of either short acyl chain palmitoyl-Gb3 or long acyl chain lignoceryl-Gb3 using 2H solid-state NMR spectroscopy. To this end, both globotriaosylceramides were chemically synthesized featuring a perdeuterated lipid acyl chain. The solid-state 2H NMR spectra support the phase separation into a POPC-rich ld phase and a PSM/cholesterol-rich lo phase. The long chain lignoceryl-Gb3 showed a rather unusual order parameter profile of the acyl chain, which flattens out for the last ∼6 methylene segments. Such an odd chain conformation can be explained by partial chain interdigitation and/or a very fluid midplane region of the membrane. Possibly, the Gb3 molecules may thus preferentially be localized at the lo/ld phase boundary. In contrast, the short chain palmitoyl-Gb3 was well associated with the PSM/cholesterol-rich lo phase. Gb3 molecules act as membrane receptors for the Shiga toxin (STx) produced by Shigella dysenteriae and by enterohemorrhagic strains of Escherichia coli (EHEC). The B-subunits of STx (STxB) forming a pentameric structure were produced recombinantly and incubated with the membrane mixtures leading to alterations in the lipid packing properties and lateral organization of the membranes. Typically, STxB binding led to a decrease in lipid chain order in agreement with partial immersion of protein segments into the lipid-water interface of the membrane. In the presence of STxB, Gb3 preferentially partitioned into the lo membrane phase. In particular the short acyl chain palmitoyl-Gb3 showed very similar chain order parameters to PSM. In the presence of STxB, all lipid species showed isotropic contributions to the 2H NMR powder spectra; this was most pronounced for the Gb3 molecules. Such isotropic contributions are caused by highly curved membrane structures, which have previously been detected as membrane invaginations in fluorescence microscopy. Our analysis estimated that STxB induced highly curved membrane structures with a curvature radius of less than ∼10 nm likely related to the insertion of STxB segments into the lipid-water interface of the membrane.
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Affiliation(s)
- Mathias Bosse
- Institute for Medical Physics and Biophysics, Leipzig University, Härtelstr. 16-18, D-04107 Leipzig, Germany.
| | - Jeremias Sibold
- Institute for Organic and Biomolecular Chemistry, University of Göttingen, Tammannstr. 2, D-37077 Göttingen, Germany
| | - Holger A Scheidt
- Institute for Medical Physics and Biophysics, Leipzig University, Härtelstr. 16-18, D-04107 Leipzig, Germany.
| | - Lukas J Patalag
- Technische Universität Braunschweig, Institute of Organic Chemistry, Hagenring 30, D-38106 Braunschweig, Germany
| | - Katharina Kettelhoit
- Technische Universität Braunschweig, Institute of Organic Chemistry, Hagenring 30, D-38106 Braunschweig, Germany
| | - Annika Ries
- Technische Universität Braunschweig, Institute of Organic Chemistry, Hagenring 30, D-38106 Braunschweig, Germany
| | - Daniel B Werz
- Technische Universität Braunschweig, Institute of Organic Chemistry, Hagenring 30, D-38106 Braunschweig, Germany
| | - Claudia Steinem
- Institute for Organic and Biomolecular Chemistry, University of Göttingen, Tammannstr. 2, D-37077 Göttingen, Germany and Max-Planck-Institute for Dynamics and Self-Organization, Am Fassberg 11, 37077 Göttingen, Germany
| | - Daniel Huster
- Institute for Medical Physics and Biophysics, Leipzig University, Härtelstr. 16-18, D-04107 Leipzig, Germany.
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11
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Bandara A, Panahi A, Pantelopulos GA, Nagai T, Straub JE. Exploring the impact of proteins on the line tension of a phase-separating ternary lipid mixture. J Chem Phys 2019; 150:204702. [PMID: 31153187 DOI: 10.1063/1.5091450] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The separation of lipid mixtures into thermodynamically stable phase-separated domains is dependent on lipid composition, temperature, and system size. Using molecular dynamics simulations, the line tension between thermodynamically stable lipid domains formed from ternary mixtures of di-C16:0 PC:di-C18:2 PC:cholesterol at 40:40:20 mol. % ratio was investigated via two theoretical approaches. The line tension was found to be 3.1 ± 0.2 pN by capillary wave theory and 4.7 ± 3.7 pN by pressure tensor anisotropy approaches for coarse-grained models based on the Martini force field. Using an all-atom model of the lipid membrane based on the CHARMM36 force field, the line tension was found to be 3.6 ± 0.9 pN using capillary wave theory and 1.8 ± 2.2 pN using pressure anisotropy approaches. The discrepancy between estimates of the line tension based on capillary wave theory and pressure tensor anisotropy methods is discussed. Inclusion of protein in Martini membrane lipid mixtures was found to reduce the line tension by 25%-35% as calculated by the capillary wave theory approach. To further understand and predict the behavior of proteins in phase-separated membranes, we have formulated an analytical Flory-Huggins model and parameterized it against the simulation results. Taken together these results suggest a general role for proteins in reducing the thermodynamic cost associated with domain formation in lipid mixtures and quantifies the thermodynamic driving force promoting the association of proteins to domain interfaces.
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Affiliation(s)
- Asanga Bandara
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA
| | - Afra Panahi
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA
| | - George A Pantelopulos
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA
| | - Tetsuro Nagai
- Department of Physics, Graduate School of Science, Nagoya University, Nagoya, Aichi 464-8602, Japan
| | - John E Straub
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA
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12
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13
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Kováčik A, Vogel A, Adler J, Pullmannová P, Vávrová K, Huster D. Probing the role of ceramide hydroxylation in skin barrier lipid models by 2H solid-state NMR spectroscopy and X-ray powder diffraction. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:1162-1170. [PMID: 29408487 DOI: 10.1016/j.bbamem.2018.02.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 01/30/2018] [Accepted: 02/01/2018] [Indexed: 10/18/2022]
Abstract
In this work, we studied model stratum corneum lipid mixtures composed of the hydroxylated skin ceramides N-lignoceroyl 6-hydroxysphingosine (Cer[NH]) and α-hydroxylignoceroyl phytosphingosine (Cer[AP]). Two model skin lipid mixtures of the composition Cer[NH] or Cer[AP], N-lignoceroyl sphingosine (Cer[NS]), lignoceric acid (C24:0) and cholesterol in a 0.5:0.5:1:1 molar ratio were compared. Model membranes were investigated by differential scanning calorimetry and 2H solid-state NMR spectroscopy at temperatures from 25 °C to 80 °C. Each component of the model mixture was specifically deuterated for selective detection by 2H NMR. Thus, the exact phase composition of the mixture at varying temperatures could be quantified. Moreover, using X-ray powder diffraction we investigated the lamellar phase formation. From the solid-state NMR and DSC studies, we found that both hydroxylated Cer[NH] and Cer[AP] exhibit a similar phase behavior. At physiological skin temperature of 32 °C, the lipids form a crystalline (orthorhombic) phase. With increasing temperature, most of the lipids become fluid and form a liquid-crystalline phase, which converts to the isotropic phase at higher temperatures (65-80 °C). Interestingly, lignoceric acid in the Cer[NH]-containing mixture has a tendency to form two types of fluid phases at 65 °C. This tendency was also observed in Cer[AP]-containing membranes at 80 °C. While Cer[AP]-containing lipid models formed a short periodicity phase featuring a repeat spacing of d = 5.4 nm, in the Cer[NH]-based model skin lipid membranes, the formation of unusual long periodicity phase with a repeat spacing of d = 10.7 nm was observed.
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Affiliation(s)
- Andrej Kováčik
- Institute for Medical Physics and Biophysics, Leipzig University, Härtelstrasse 16-18, 04107 Leipzig, Germany; Skin Barrier Research Group, Faculty of Pharmacy in Hradec Králové, Charles University, Akademika Heyrovského 1203, 50005 Hradec Králové, Czech Republic
| | - Alexander Vogel
- Institute for Medical Physics and Biophysics, Leipzig University, Härtelstrasse 16-18, 04107 Leipzig, Germany
| | - Juliane Adler
- Institute for Medical Physics and Biophysics, Leipzig University, Härtelstrasse 16-18, 04107 Leipzig, Germany
| | - Petra Pullmannová
- Skin Barrier Research Group, Faculty of Pharmacy in Hradec Králové, Charles University, Akademika Heyrovského 1203, 50005 Hradec Králové, Czech Republic
| | - Kateřina Vávrová
- Skin Barrier Research Group, Faculty of Pharmacy in Hradec Králové, Charles University, Akademika Heyrovského 1203, 50005 Hradec Králové, Czech Republic.
| | - Daniel Huster
- Institute for Medical Physics and Biophysics, Leipzig University, Härtelstrasse 16-18, 04107 Leipzig, Germany.
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14
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Cholesterol overload in the liver aggravates oxidative stress-mediated DNA damage and accelerates hepatocarcinogenesis. Oncotarget 2017; 8:104136-104148. [PMID: 29262627 PMCID: PMC5732793 DOI: 10.18632/oncotarget.22024] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2017] [Accepted: 09/20/2017] [Indexed: 12/15/2022] Open
Abstract
Primary liver cancers represent the second leading cause of cancer-related deaths worldwide. Diverse etiological factors include chronic viral hepatitis, aflatoxin and alcohol exposure as well as aberrant liver lipid overload. Cholesterol has been identified as a key inducer of metabolic impairment, oxidative stress and promoter of cellular dysfunction. The aim of this work was to address the oxidative stress-mediated DNA damage induced by cholesterol overload, and its role in the development of hepatocellular carcinoma. C57BL/6 male mice were fed with a high cholesterol diet, followed by a single dose of N-diethylnitrosamine (DEN, 10 μg/g, ip). Reactive oxygen species generation, DNA oxidation, antioxidant and DNA repair proteins were analyzed at different time points. Diet-induced cholesterol overload caused enhanced oxidative DNA damage in the liver and was associated with a decrease in key DNA repair genes as early as 7 days. Interestingly, we found a cell survival response, induced by cholesterol, judged by a decrement in Bax to Bcl2 ratio. Importantly, N-acetyl-cysteine supplementation significantly prevented DNA oxidation damage. Furthermore, at 8 months after DEN administration, tumor growth was significantly enhanced in mice under cholesterol diet in comparison to control animals. Together, these results suggest that cholesterol overload exerts an oxidative stress-mediated effects and promotes the development of liver cancer.
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15
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Dwivedi M, Mejuch T, Waldmann H, Winter R. Lateral Organization of Host Heterogeneous Raft-like Membranes Altered by the Myristoyl Modification of Tyrosine Kinase c-Src. Angew Chem Int Ed Engl 2017; 56:10511-10515. [DOI: 10.1002/anie.201706233] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Indexed: 11/06/2022]
Affiliation(s)
- Mridula Dwivedi
- Department of Chemistry and Chemical Biology, Physical Chemistry; Technical University of Dortmund; Otto-Hahn-Str.4a 44221 Dortmund Germany
| | - Tom Mejuch
- Department of Chemistry and Chemical Biology; Max-Planck-Institute of Molecular Physiology; Otto-Hahn-Strasse 11 44227 Dortmund Germany
| | - Herbert Waldmann
- Department of Chemistry and Chemical Biology; Max-Planck-Institute of Molecular Physiology; Otto-Hahn-Strasse 11 44227 Dortmund Germany
| | - Roland Winter
- Department of Chemistry and Chemical Biology, Physical Chemistry; Technical University of Dortmund; Otto-Hahn-Str.4a 44221 Dortmund Germany
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16
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Dwivedi M, Mejuch T, Waldmann H, Winter R. Lateral Organization of Host Heterogeneous Raft-like Membranes Altered by the Myristoyl Modification of Tyrosine Kinase c-Src. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201706233] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Mridula Dwivedi
- Department of Chemistry and Chemical Biology, Physical Chemistry; Technical University of Dortmund; Otto-Hahn-Str.4a 44221 Dortmund Germany
| | - Tom Mejuch
- Department of Chemistry and Chemical Biology; Max-Planck-Institute of Molecular Physiology; Otto-Hahn-Strasse 11 44227 Dortmund Germany
| | - Herbert Waldmann
- Department of Chemistry and Chemical Biology; Max-Planck-Institute of Molecular Physiology; Otto-Hahn-Strasse 11 44227 Dortmund Germany
| | - Roland Winter
- Department of Chemistry and Chemical Biology, Physical Chemistry; Technical University of Dortmund; Otto-Hahn-Str.4a 44221 Dortmund Germany
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17
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Erwin N, Patra S, Dwivedi M, Weise K, Winter R. Influence of isoform-specific Ras lipidation motifs on protein partitioning and dynamics in model membrane systems of various complexity. Biol Chem 2017; 398:547-563. [PMID: 27977396 DOI: 10.1515/hsz-2016-0289] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2016] [Accepted: 12/07/2016] [Indexed: 12/17/2022]
Abstract
The partitioning of the lipidated signaling proteins N-Ras and K-Ras4B into various membrane systems, ranging from single-component fluid bilayers, binary fluid mixtures, heterogeneous raft model membranes up to complex native-like lipid mixtures (GPMVs) in the absence and presence of integral membrane proteins have been explored in the last decade in a combined chemical-biological and biophysical approach. These studies have revealed pronounced isoform-specific differences regarding the lateral distribution in membranes and formation of protein-rich membrane domains. In this context, we will also discuss the effects of lipid head group structure and charge density on the partitioning behavior of the lipoproteins. Moreover, the dynamic properties of N-Ras and K-Ras4B have been studied in different model membrane systems and native-like crowded milieus. Addition of crowding agents such as Ficoll and its monomeric unit, sucrose, gradually favors clustering of Ras proteins in forming small oligomers in the bulk; only at very high crowder concentrations association is disfavored.
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Affiliation(s)
- Nelli Erwin
- Physical Chemistry I - Biophysical Chemistry, Faculty of Chemistry and Chemical Biology, Dortmund Technical University, Otto-Hahn-Strasse 4a, D-44227 Dortmund
| | - Satyajit Patra
- Physical Chemistry I - Biophysical Chemistry, Faculty of Chemistry and Chemical Biology, Dortmund Technical University, Otto-Hahn-Strasse 4a, D-44227 Dortmund
| | - Mridula Dwivedi
- Physical Chemistry I - Biophysical Chemistry, Faculty of Chemistry and Chemical Biology, Dortmund Technical University, Otto-Hahn-Strasse 4a, D-44227 Dortmund
| | - Katrin Weise
- Physical Chemistry I - Biophysical Chemistry, Faculty of Chemistry and Chemical Biology, Dortmund Technical University, Otto-Hahn-Strasse 4a, D-44227 Dortmund
| | - Roland Winter
- Physical Chemistry I - Biophysical Chemistry, Faculty of Chemistry and Chemical Biology, Dortmund Technical University, Otto-Hahn-Strasse 4a, D-44227 Dortmund
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18
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Simanshu DK, Nissley DV, McCormick F. RAS Proteins and Their Regulators in Human Disease. Cell 2017; 170:17-33. [PMID: 28666118 PMCID: PMC5555610 DOI: 10.1016/j.cell.2017.06.009] [Citation(s) in RCA: 1133] [Impact Index Per Article: 161.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 05/22/2017] [Accepted: 06/07/2017] [Indexed: 02/07/2023]
Abstract
RAS proteins are binary switches, cycling between ON and OFF states during signal transduction. These switches are normally tightly controlled, but in RAS-related diseases, such as cancer, RASopathies, and many psychiatric disorders, mutations in the RAS genes or their regulators render RAS proteins persistently active. The structural basis of the switch and many of the pathways that RAS controls are well known, but the precise mechanisms by which RAS proteins function are less clear. All RAS biology occurs in membranes: a precise understanding of RAS' interaction with membranes is essential to understand RAS action and to intervene in RAS-driven diseases.
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Affiliation(s)
- Dhirendra K Simanshu
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Frederick, MD 21701, USA
| | - Dwight V Nissley
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Frederick, MD 21701, USA
| | - Frank McCormick
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Frederick, MD 21701, USA; Helen Diller Family Comprehensive Cancer Center, University of California San Francisco, 1450 3(rd) Street, San Francisco, CA 94158, USA.
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19
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Sperlich B, Kapoor S, Waldmann H, Winter R, Weise K. Regulation of K-Ras4B Membrane Binding by Calmodulin. Biophys J 2017; 111:113-22. [PMID: 27410739 DOI: 10.1016/j.bpj.2016.05.042] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Revised: 05/03/2016] [Accepted: 05/24/2016] [Indexed: 12/28/2022] Open
Abstract
K-Ras4B is a membrane-bound small GTPase with a prominent role in cancer development. It contains a polybasic farnesylated C-terminus that is required for the correct localization and clustering of K-Ras4B in distinct membrane domains. PDEδ and the Ca(2+)-binding protein calmodulin (CaM) are known to function as potential binding partners for farnesylated Ras proteins. However, they differ in the number of interaction sites with K-Ras4B, leading to different modes of interaction, and thus affect the subcellular distribution of K-Ras4B in different ways. Although it is clear that Ca(2+)-bound CaM can play a role in the dynamic spatial cycle of K-Ras4B in the cell, the exact molecular mechanism is only partially understood. In this biophysical study, we investigated the effect of Ca(2+)/CaM on the interaction of GDP- and GTP-loaded K-Ras4B with heterogeneous model biomembranes by using a combination of different spectroscopic and imaging techniques. The results show that Ca(2+)/CaM is able to extract K-Ras4B from negatively charged membranes in a nucleotide-independent manner. Moreover, the data demonstrate that the complex of Ca(2+)/CaM and K-Ras4B is stable in the presence of anionic membranes and shows no membrane binding. Finally, the influence of Ca(2+)/CaM on the interaction of K-Ras4B with membranes is compared with that of PDEδ, which was investigated in a previous study. Although both CaM and PDEδ exhibit a hydrophobic binding pocket for farnesyl, they have different effects on membrane binding of K-Ras4B and hence should be capable of regulating K-Ras4B plasma membrane localization in the cell.
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Affiliation(s)
- Benjamin Sperlich
- Physical Chemistry I - Biophysical Chemistry, TU Dortmund University, Dortmund, Germany
| | - Shobhna Kapoor
- Chemical Biology, TU Dortmund University, Dortmund, Germany; Department of Chemical Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Herbert Waldmann
- Chemical Biology, TU Dortmund University, Dortmund, Germany; Department of Chemical Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Roland Winter
- Physical Chemistry I - Biophysical Chemistry, TU Dortmund University, Dortmund, Germany.
| | - Katrin Weise
- Physical Chemistry I - Biophysical Chemistry, TU Dortmund University, Dortmund, Germany.
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20
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Edler E, Schulze E, Stein M. Membrane localization and dynamics of geranylgeranylated Rab5 hypervariable region. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:1335-1349. [PMID: 28455099 DOI: 10.1016/j.bbamem.2017.04.021] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Revised: 04/18/2017] [Accepted: 04/23/2017] [Indexed: 12/11/2022]
Abstract
The small GTPase Rab5 is a key regulator of endosomal trafficking processes and a marker for the early endosome. The C-terminal hypervariable region (HVR) of Rab5 is post-translationally modified at residues Cys212 and Cys213 to accommodate two geranylgeranyl anchors (C20 carbon chain length) in order to associate Rab5 with the membrane. The structural role of the HVR regarding protein-early endosome membrane recruitment is not resolved due to its high degree of flexibility and lack of crystallographic information. Here, full-atomistic and coarse-grained molecular dynamics simulations of the truncated Rab5 HVR206-215 in three model membranes of increasing complexity (pure phospholipid bilayer, ternary membrane with cholesterol, six-component early endosome) were performed. Specific electrostatic interactions between the HVR206-215 Arg209 residue and the phosphate group of the inositol ring of PI(3)P were detected. This shows that PI(3)P acts as a first contact site of protein recruitment to the early endosome. The free energy change of HVR206-215 extraction from the bilayer was largest for the physiological negatively charged membrane. 5μs coarse-grained simulations revealed an active recruitment of PI(3)P to the HVR206-215 supporting the formation of Rab5- and PI(3)P enriched signaling platforms.
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Affiliation(s)
- Eileen Edler
- Molecular Simulations and Design Group, Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstrasse 1, 39106 Magdeburg, Germany
| | - Eric Schulze
- Molecular Simulations and Design Group, Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstrasse 1, 39106 Magdeburg, Germany; International Max Planck Research School (IMPRS) for Advanced Methods in Process and Systems Engineering, Magdeburg, Germany
| | - Matthias Stein
- Molecular Simulations and Design Group, Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstrasse 1, 39106 Magdeburg, Germany.
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21
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Schroeter A, Stahlberg S, Školová B, Sonnenberger S, Eichner A, Huster D, Vávrová K, Hauß T, Dobner B, Neubert RHH, Vogel A. Phase separation in ceramide[NP] containing lipid model membranes: neutron diffraction and solid-state NMR. SOFT MATTER 2017; 13:2107-2119. [PMID: 28225091 DOI: 10.1039/c6sm02356h] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The stratum corneum is the outermost layer of the skin and protects the organism against external influences as well as water loss. It consists of corneocytes embedded in a mixture of ceramides, fatty acids, and cholesterol in a molar ratio of roughly 1 : 1 : 1. The unique structural and compositional arrangement of these stratum corneum lipids is responsible for the skin barrier properties. Many studies investigated the organization of these barrier lipids and, in particular, the exact conformation of ceramides. However, so far no consensus has been reached. In this study, we investigate a model system comprised of N-(non-hydroxy-tetracosanoyl)-phytosphingosine/cholesterol/tetracosanoic acid (CER[NP]-C24/CHOL/TA) at a 1 : 1 : 1 molar ratio using neutron diffraction and 2H solid-state NMR spectroscopy at temperatures from 25 °C to 80 °C. Deuterated variants of all three lipid components of the model system were used to enable their separate investigation in the NMR spectra and quantification of the amount of molecules in each phase. Neutron scattering experiments show the coexistence of two lipid phases at low temperatures with repeat spacings of 54.2 Å and 43.0 Å at a physiological skin temperature of 32 °C. They appear to be indistinguishable in the 2H NMR spectra as both phases are crystalline and ceramide molecules do not rotate around their long axis on a microsecond timescale. The evolution of these phases upon heating is followed and with increasing temperature fluid and even isotropically mobile molecules are observed. A model of the organization of the lamellar phases is proposed in which the thicker phase consists of CER[NP]-C24 in a hairpin conformation mixed with CHOL and TA, while the phase with a repeat spacing of 43.0 Å contains CER[NP]-C24 in a V-shape conformation.
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Affiliation(s)
- Annett Schroeter
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Sören Stahlberg
- Institute for Medical Physics and Biophysics, University of Leipzig, Härtelstraße 16-18, D-04107 Leipzig, Germany.
| | - Barbora Školová
- Institute for Medical Physics and Biophysics, University of Leipzig, Härtelstraße 16-18, D-04107 Leipzig, Germany. and Faculty of Pharmacy, Charles University, Akademika Heyrovského 1203, 50005 Hradec Králové, Czech Republic
| | - Stefan Sonnenberger
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Adina Eichner
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Daniel Huster
- Institute for Medical Physics and Biophysics, University of Leipzig, Härtelstraße 16-18, D-04107 Leipzig, Germany.
| | - Kateřina Vávrová
- Faculty of Pharmacy, Charles University, Akademika Heyrovského 1203, 50005 Hradec Králové, Czech Republic
| | - Thomas Hauß
- Institute of Soft Matter and Functional Materials, Helmholtz-Zentrum für Materialien und Energie, Berlin, Germany
| | - Bodo Dobner
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Reinhard H H Neubert
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany and Institute of Applied Dermatopharmacy at the Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Alexander Vogel
- Institute for Medical Physics and Biophysics, University of Leipzig, Härtelstraße 16-18, D-04107 Leipzig, Germany.
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22
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Erwin N, Sperlich B, Garivet G, Waldmann H, Weise K, Winter R. Lipoprotein insertion into membranes of various complexity: lipid sorting, interfacial adsorption and protein clustering. Phys Chem Chem Phys 2017; 18:8954-62. [PMID: 26960984 DOI: 10.1039/c6cp00563b] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
In a combined chemical-biological and biophysical approach we explored the membrane partitioning of the lipidated signaling proteins N-Ras and K-Ras4B into membrane systems of different complexity, ranging from one-component lipid bilayers and anionic binary and ternary heterogeneous membrane systems even up to partitioning studies on protein-free and protein-containing giant plasma membrane vesicles (GPMVs). To yield a pictorial view of the localization process, imaging using confocal laser scanning and atomic force microscopy was performed. The results reveal pronounced isoform-specific differences regarding the lateral distribution and formation of protein-rich membrane domains. Line tension is one of the key parameters controlling not only the size and dynamic properties of segregated lipid domains but also the partitioning process of N-Ras that acts as a lineactant. The formation of N-Ras protein clusters is even recorded for almost vanishing hydrophobic mismatch. Conversely, for K-Ras4B, selective localization and clustering are electrostatically mediated by its polybasic farnesylated C-terminus. The formation of K-Ras4B clusters is also observed for the multi-component GPMV membrane, i.e., it seems to be a general phenomenon, largely independent of the details of the membrane composition, including the anionic charge density of lipid headgroups. Our data indicate that unspecific and entropy-driven membrane-mediated interactions play a major role in the partitioning behavior, thus relaxing the need for a multitude of fine-tuned interactions. Such a scenario seems also to be reasonable recalling the high dynamic nature of cellular membranes. Finally, we note that even relatively simple models of heterogeneous membranes are able to reproduce many of the properties of much more complex biological membranes.
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Affiliation(s)
- Nelli Erwin
- Faculty of Chemistry and Chemical Biology, Physical Chemistry I - Biophysical Chemistry, TU Dortmund University, D-44221 Dortmund, Germany.
| | - Benjamin Sperlich
- Faculty of Chemistry and Chemical Biology, Physical Chemistry I - Biophysical Chemistry, TU Dortmund University, D-44221 Dortmund, Germany.
| | - Guillaume Garivet
- Department of Chemical Biology, Max Planck Institute of Molecular Physiology, Otto-Hahn-Str. 11, D-44227 Dortmund, Germany and Faculty of Chemistry and Chemical Biology, Department of Chemical Biology, TU Dortmund University, D-44221 Dortmund, Germany
| | - Herbert Waldmann
- Department of Chemical Biology, Max Planck Institute of Molecular Physiology, Otto-Hahn-Str. 11, D-44227 Dortmund, Germany and Faculty of Chemistry and Chemical Biology, Department of Chemical Biology, TU Dortmund University, D-44221 Dortmund, Germany
| | - Katrin Weise
- Faculty of Chemistry and Chemical Biology, Physical Chemistry I - Biophysical Chemistry, TU Dortmund University, D-44221 Dortmund, Germany.
| | - Roland Winter
- Faculty of Chemistry and Chemical Biology, Physical Chemistry I - Biophysical Chemistry, TU Dortmund University, D-44221 Dortmund, Germany.
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23
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Combining NMR Spectroscopy and Molecular Dynamics Simulation to Investigate the Structure and Dynamics of Membrane-Associated Proteins. SPRINGER SERIES IN BIOPHYSICS 2017. [DOI: 10.1007/978-3-319-66601-3_14] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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24
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Scheidt HA, Klingler J, Huster D, Keller S. Structural Thermodynamics of myr-Src(2-19) Binding to Phospholipid Membranes. Biophys J 2016; 109:586-94. [PMID: 26244740 DOI: 10.1016/j.bpj.2015.06.051] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Revised: 06/24/2015] [Accepted: 06/24/2015] [Indexed: 12/19/2022] Open
Abstract
Many proteins are anchored to lipid bilayer membranes through a combination of hydrophobic and electrostatic interactions. In the case of the membrane-bound nonreceptor tyrosine kinase Src from Rous sarcoma virus, these interactions are mediated by an N-terminal myristoyl chain and an adjacent cluster of six basic amino-acid residues, respectively. In contrast with the acyl modifications of other lipid-anchored proteins, the myristoyl chain of Src does not match the host lipid bilayer in terms of chain conformation and dynamics, which is attributed to a tradeoff between hydrophobic burial of the myristoyl chain and repulsion of the peptidic moiety from the phospholipid headgroup region. Here, we combine thermodynamic information obtained from isothermal titration calorimetry with structural data derived from (2)H, (13)C, and (31)P solid-state nuclear magnetic resonance spectroscopy to decipher the hydrophobic and electrostatic contributions governing the interactions of a myristoylated Src peptide with zwitterionic and anionic membranes made from lauroyl (C12:0) or myristoyl (C14:0) lipids. Although the latter are expected to enable better hydrophobic matching, the Src peptide partitions more avidly into the shorter-chain lipid analog because this does not require the myristoyl chain to stretch extensively to avoid unfavorable peptide/headgroup interactions. Moreover, we find that Coulombic and intrinsic contributions to membrane binding are not additive, because the presence of anionic lipids enhances membrane binding more strongly than would be expected on the basis of simple Coulombic attraction.
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Affiliation(s)
- Holger A Scheidt
- Institut für Medizinische Physik und Biophysik, Universität Leipzig, Leipzig, Germany
| | - Johannes Klingler
- Molecular Biophysics, University of Kaiserslautern, Kaiserslautern, Germany
| | - Daniel Huster
- Institut für Medizinische Physik und Biophysik, Universität Leipzig, Leipzig, Germany
| | - Sandro Keller
- Molecular Biophysics, University of Kaiserslautern, Kaiserslautern, Germany.
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Chen YX, Koch S, Uhlenbrock K, Weise K, Das D, Gremer L, Brunsveld L, Wittinghofer A, Winter R, Triola G, Waldmann H. Synthesis of the Rheb and K-Ras4B GTPases. Angew Chem Int Ed Engl 2015; 49:6090-5. [PMID: 20652921 DOI: 10.1002/anie.201001884] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Yong-Xiang Chen
- Abteilung Chemische Biologie, Max-Planck-Institut für molekulare Physiologie, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
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26
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Stahlberg S, Školová B, Madhu PK, Vogel A, Vávrová K, Huster D. Probing the role of the ceramide acyl chain length and sphingosine unsaturation in model skin barrier lipid mixtures by (2)H solid-state NMR spectroscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:4906-4915. [PMID: 25870928 DOI: 10.1021/acs.langmuir.5b00751] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We investigated equimolar mixtures of ceramides with lignoceric acid and cholesterol as models for the human stratum corneum by differential scanning calorimetry and (2)H solid-state NMR spectroscopy. Our reference system consisted of lignoceroyl sphingosine (Cer[NS24]), which represents one of the ceramides in the human stratum corneum. Furthermore, the effect of ceramide acyl chain truncation to 16 carbons as in Cer[NS16] and the loss of the C4 trans double bond as in dihydroceramide Cer[NDS24] were studied. Fully relaxed (2)H NMR spectra were acquired for each deuterated component of each mixture separately, allowing the quantitative determination of the individual lipid phases. At skin temperature, the reference system containing Cer[NS24] is characterized by large portions of each component of the mixture in a crystalline phase, which largely restricts the permeability of the skin lipid barrier. The loss of the C4 trans double bond in Cer[NDS24] leads to the replacement of more than 25% of the crystalline phase by an isotropic phase of the dihydroceramide that shows the importance of dihydroceramide desaturation in the formation of the skin lipid barrier. The truncated Cer[NS16] is mostly found in the gel phase at skin temperature, which may explain its negative effect on the transepidermal water loss in atopic dermatitis patients. These significant alterations in the phase behavior of all lipids are further reflected at elevated temperatures. The molecular insights of our study may help us to understand the importance of the structural parameters of ceramides in healthy and compromised skin barriers.
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Affiliation(s)
- Sören Stahlberg
- †Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, 04107 Leipzig, Germany
| | - Barbora Školová
- †Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, 04107 Leipzig, Germany
- ‡Faculty of Pharmacy, Charles University in Prague, Heyrovského 1203, 50005 Hradec Králové, Czech Republic
| | - Perunthiruthy K Madhu
- §Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India
- ∥TIFR Centre for Interdisciplinary Sciences, 21 Brundavan Colony, Narsingi, Hyderabad 500 075, India
| | - Alexander Vogel
- †Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, 04107 Leipzig, Germany
| | - Kateřina Vávrová
- ‡Faculty of Pharmacy, Charles University in Prague, Heyrovského 1203, 50005 Hradec Králové, Czech Republic
| | - Daniel Huster
- †Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, 04107 Leipzig, Germany
- §Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India
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Vogel A, Nikolaus J, Weise K, Triola G, Waldmann H, Winter R, Herrmann A, Huster D. Interaction of the human N-Ras protein with lipid raft model membranes of varying degrees of complexity. Biol Chem 2015; 395:779-89. [PMID: 24526608 DOI: 10.1515/hsz-2013-0294] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Accepted: 02/06/2014] [Indexed: 11/15/2022]
Abstract
Ternary lipid mixtures composed of cholesterol, saturated (frequently with sphingosine backbone), and unsaturated phospholipids show stable phase separation and are often used as model systems of lipid rafts. Yet, their ability to reproduce raft properties and function is still debated. We investigated the properties and functional aspects of three lipid raft model systems of varying degrees of biological relevance--PSM/POPC/Chol, DPPC/POPC/Chol, and DPPC/DOPC/Chol--using 2H solid-state nuclear magnetic resonance (NMR) spectroscopy, fluorescence microscopy, and atomic force microscopy. While some minor differences were observed, the general behavior and properties of all three model mixtures were similar to previously investigated influenza envelope lipid membranes, which closely mimic the lipid composition of biological membranes. For the investigation of the functional aspects, we employed the human N-Ras protein, which is posttranslationally modified by two lipid modifications that anchor the protein to the membrane. It was previously shown that N-Ras preferentially resides in liquid-disordered domains and exhibits a time-dependent accumulation in the domain boundaries of influenza envelope lipid membranes. For all three model mixtures, we observed the same membrane partitioning behavior for N-Ras. Therefore, we conclude that even relatively simple models of raft membranes are able to reproduce many of their specific properties and functions.
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Thomas L, Kahr J, Schmidt P, Krug U, Scheidt HA, Huster D. The dynamics of the G protein-coupled neuropeptide Y2 receptor in monounsaturated membranes investigated by solid-state NMR spectroscopy. JOURNAL OF BIOMOLECULAR NMR 2015; 61:347-59. [PMID: 25556885 DOI: 10.1007/s10858-014-9892-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Accepted: 12/20/2014] [Indexed: 05/14/2023]
Abstract
In contrast to the static snapshots provided by protein crystallography, G protein-coupled receptors constitute a group of proteins with highly dynamic properties, which are required in the receptors' function as signaling molecule. Here, the human neuropeptide Y2 receptor was reconstituted into a model membrane composed of monounsaturated phospholipids and solid-state NMR was used to characterize its dynamics. Qualitative static (15)N NMR spectra and quantitative determination of (1)H-(13)C order parameters through measurement of the (1)H-(13)C dipolar couplings of the CH, CH2 and CH3 groups revealed axially symmetric motions of the whole molecule in the membrane and molecular fluctuations of varying amplitude from all molecular segments. The molecular order parameters (S(backbone) = 0.59-0.67, S(CH2) = 0.41-0.51 and S(CH3) = 0.22) obtained in directly polarized (13)C NMR experiments demonstrate that the Y2 receptor is highly mobile in the native-like membrane. Interestingly, according to these results the receptor was found to be slightly more rigid in the membranes formed by the monounsaturated phospholipids than by saturated phospholipids as investigated previously. This could be caused by an increased chain length of the monounsaturated lipids, which may result in a higher helical content of the receptor. Furthermore, the incorporation of cholesterol, phosphatidylethanolamine, or negatively charged phosphatidylserine into the membrane did not have a significant influence on the molecular mobility of the Y2 receptor.
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Affiliation(s)
- Lars Thomas
- Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, 04107, Leipzig, Germany
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29
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Integrating solid-state NMR and computational modeling to investigate the structure and dynamics of membrane-associated ghrelin. PLoS One 2015; 10:e0122444. [PMID: 25803439 PMCID: PMC4372444 DOI: 10.1371/journal.pone.0122444] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Accepted: 02/11/2015] [Indexed: 12/18/2022] Open
Abstract
The peptide hormone ghrelin activates the growth hormone secretagogue receptor 1a, also known as the ghrelin receptor. This 28-residue peptide is acylated at Ser3 and is the only peptide hormone in the human body that is lipid-modified by an octanoyl group. Little is known about the structure and dynamics of membrane-associated ghrelin. We carried out solid-state NMR studies of ghrelin in lipid vesicles, followed by computational modeling of the peptide using Rosetta. Isotropic chemical shift data of isotopically labeled ghrelin provide information about the peptide’s secondary structure. Spin diffusion experiments indicate that ghrelin binds to membranes via its lipidated Ser3. Further, Phe4, as well as electrostatics involving the peptide’s positively charged residues and lipid polar headgroups, contribute to the binding energy. Other than the lipid anchor, ghrelin is highly flexible and mobile at the membrane surface. This observation is supported by our predicted model ensemble, which is in good agreement with experimentally determined chemical shifts. In the final ensemble of models, residues 8–17 form an α-helix, while residues 21–23 and 26–27 often adopt a polyproline II helical conformation. These helices appear to assist the peptide in forming an amphipathic conformation so that it can bind to the membrane.
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Guanylate Cyclase-Activating Protein-2 Undergoes Structural Changes upon Binding to Detergent Micelles and Bicelles. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:2767-77. [DOI: 10.1016/j.bbamem.2014.07.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Revised: 07/11/2014] [Accepted: 07/14/2014] [Indexed: 11/23/2022]
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31
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Nomura K, Harada E, Sugase K, Shimamoto K. Solid-state NMR spectra of lipid-anchored proteins under magic angle spinning. J Phys Chem B 2014; 118:2405-13. [PMID: 24517164 DOI: 10.1021/jp4124106] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Solid-state NMR is a promising tool for elucidating membrane-related biological phenomena. We achieved the measurement of high-resolution solid-state NMR spectra for a lipid-anchored protein embedded in lipid bilayers under magic angle spinning (MAS). To date, solid-state NMR measurements of lipid-anchored proteins have not been accomplished due to the difficulty in supplying sufficient amount of stable isotope labeled samples in the overexpression of lipid-anchored proteins requiring complex posttranslational modification. We designed a pseudo lipid-anchored protein in which the protein component was expressed in E. coli and attached to a chemically synthesized lipid-anchor mimic. Using two types of membranes, liposomes and bicelles, we demonstrated different types of insertion procedures for lipid-anchored protein into membranes. In the liposome sample, we were able to observe the cross-polarization and the (13)C-(13)C chemical shift correlation spectra under MAS, indicating that the liposome sample can be used to analyze molecular interactions using dipolar-based NMR experiments. In contrast, the bicelle sample showed sufficient quality of spectra through scalar-based experiments. The relaxation times and protein-membrane interaction were capable of being analyzed in the bicelle sample. These results demonstrated the applicability of two types of sample system to elucidate the roles of lipid-anchors in regulating diverse biological phenomena.
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Affiliation(s)
- Kaoru Nomura
- Bioorganic Research Institute, Suntory Foundation for Life Sciences , 1-1-1 Wakayamadai, Shimamoto-Cho, Mishima-Gun, Osaka 618-8503, Japan
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Li Z, Gorfe AA. Deformation of a Two-domain Lipid Bilayer due to Asymmetric Insertion of Lipid-modified Ras Peptides. SOFT MATTER 2013; 9:10.1039/C3SM51388B. [PMID: 24358048 PMCID: PMC3864742 DOI: 10.1039/c3sm51388b] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Ras proteins are attached to the inner leaflet of the plasma membrane via a lipid-modified anchor. Membrane-bound Ras proteins laterally segregate into nanoscale signaling platforms called nanoclusters. It has been shown that the membrane domain preference of Ras nanoclusters varies with the nature of lipidation but their effect on the membrane has not been well understood. To investigate the effect of Ras insertion on membrane structure, we carried out numerous coarse-grained molecular dynamics (CGMD) simulations on a two-domain DPPC/DLiPC/cholesterol lipid bilayer in which different number and type of H-ras peptides were attached on one side. We have shown previously that this lipid mixture forms co-existing liquid-ordered/liquid-disordered (L o /L d ) domains and that different H-ras peptides form clusters that variously accumulate at the L o /L d regions or the boundary between them. Here we show that asymmetric insertion of each of these peptides induces a vertical relative displacement of the domains and deforms the bilayer, with the domain boundary serving as the center of deformation. The extent of the deformation, however, varies with the type and number of lipid modification. This is because the number and type of the Ras lipid tails determines the degree to which the stress caused by asymmetric peptide insertion is relieved by inter-leaflet cholesterol transfer and lipid tilt. In addition, we have characterized the mechanism of bilayer deformation based on the collective effect of the Ras peptides on inter-leaflet surface area, pressure profile and line tension differences. This allowed us to elucidate how Ras lipid modification affects membrane geometry and how a two-domain bilayer adjusts its shape through boundary deformation. The result contributes to a better understanding of Ras signaling platforms and highlights some of the mechanisms by which a multi-domain membrane responds to external perturbation.
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Affiliation(s)
- Zhenlong Li
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, 6431 Fannin St., Houston, Texas 77030
| | - Alemayehu A. Gorfe
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, 6431 Fannin St., Houston, Texas 77030
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33
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Huster D. Solid-state NMR spectroscopy to study protein-lipid interactions. Biochim Biophys Acta Mol Cell Biol Lipids 2013; 1841:1146-60. [PMID: 24333800 DOI: 10.1016/j.bbalip.2013.12.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Accepted: 12/04/2013] [Indexed: 12/22/2022]
Abstract
The appropriate lipid environment is crucial for the proper function of membrane proteins. There is a tremendous variety of lipid molecules in the membrane and so far it is often unclear which component of the lipid matrix is essential for the function of a respective protein. Lipid molecules and proteins mutually influence each other; parameters such as acyl chain order, membrane thickness, membrane elasticity, permeability, lipid-domain and annulus formation are strongly modulated by proteins. More recent data also indicates that the influence of proteins goes beyond a single annulus of next-neighbor boundary lipids. Therefore, a mesoscopic approach to membrane lipid-protein interactions in terms of elastic membrane deformations has been developed. Solid-state NMR has greatly contributed to the understanding of lipid-protein interactions and the modern view of biological membranes. Methods that detect the influence of proteins on the membrane as well as direct lipid-protein interactions have been developed and are reviewed here. Examples for solid-state NMR studies on the interaction of Ras proteins, the antimicrobial peptide protegrin-1, the G protein-coupled receptor rhodopsin, and the K(+) channel KcsA are discussed. This article is part of a Special Issue entitled Tools to study lipid functions.
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Affiliation(s)
- Daniel Huster
- Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, D-04107 Leipzig, Germany.
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34
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Li H, Gorfe AA. Aggregation of lipid-anchored full-length H-Ras in lipid bilayers: simulations with the MARTINI force field. PLoS One 2013; 8:e71018. [PMID: 23923044 PMCID: PMC3724741 DOI: 10.1371/journal.pone.0071018] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Accepted: 06/28/2013] [Indexed: 11/25/2022] Open
Abstract
Lipid-anchored Ras oncoproteins assemble into transient, nano-sized substructures on the plasma membrane. These substructures, called nanoclusters, were proposed to be crucial for high-fidelity signal transmission in cells. However, the molecular basis of Ras nanoclustering is poorly understood. In this work, we used coarse-grained (CG) molecular dynamics simulations to investigate the molecular mechanism by which full-length H-ras proteins form nanoclusters in a model membrane. We chose two different conformations of H-ras that were proposed to represent the active and inactive state of the protein, and a domain-forming model bilayer made up of di16:0-PC (DPPC), di18:2-PC (DLiPC) and cholesterol. We found that, irrespective of the initial conformation, Ras molecules assembled into a single large aggregate. However, the two binding modes, which are characterized by the different orientation of the G-domain with respect to the membrane, differ in dynamics and organization during and after aggregation. Some of these differences involve regions of Ras that are important for effector/modulator binding, which may partly explain observed differences in the ability of active and inactive H-ras nanoclusters to recruit effectors. The simulations also revealed some limitations in the CG force field to study protein assembly in solution, which we discuss in the context of proposed potential avenues of improvement.
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Affiliation(s)
- Hualin Li
- Department of Integrative Biology and Pharmacology, University of Texas Medical School at Houston, Houston, Texas, United States of America
| | - Alemayehu A. Gorfe
- Department of Integrative Biology and Pharmacology, University of Texas Medical School at Houston, Houston, Texas, United States of America
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35
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Kapoor S, Werkmüller A, Goody RS, Waldmann H, Winter R. Pressure modulation of Ras-membrane interactions and intervesicle transfer. J Am Chem Soc 2013; 135:6149-56. [PMID: 23560466 DOI: 10.1021/ja312671j] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Proteins attached to the plasma membrane frequently encounter mechanical stresses, including high hydrostatic pressure (HHP) stress. Signaling pathways involving membrane-associated small GTPases (e.g., Ras) have been identified as critical loci for pressure perturbation. However, the impact of mechanical stimuli on biological outputs is still largely terra incognita. The present study explores the effect of HHP on the membrane association, dissociation, and intervesicle transfer process of N-Ras by using a FRET-based assay to obtain the kinetic parameters and volumetric properties along the reaction path of these processes. Notably, membrane association is fostered upon pressurization. Conversely, depending on the nature and lateral organization of the lipid membrane, acceleration or retardation is observed for the dissociation step. In addition, HHP can be inferred as a positive regulator of N-Ras clustering, in particular in heterogeneous membranes. The susceptibility of membrane interaction to pressure raises the idea of a role of lipidated signaling molecules as mechanosensors, transducing mechanical stimuli to chemical signals by regulating their membrane binding and dissociation. Finally, our results provide first insights into the influence of pressure on membrane-associated Ras-controlled signaling events in organisms living under extreme environmental conditions such as those that are encountered in the deep sea and sub-seafloor environments, where pressures reach the kilobar (100 MPa) range.
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Affiliation(s)
- Shobhna Kapoor
- Physical Chemistry I-Biophysical Chemistry, Faculty of Chemistry, TU Dortmund University, Otto-Hahn-Strasse 6, D-44227 Dortmund, Germany
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36
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Grimm C, Meyer T, Czapla S, Nikolaus J, Scheidt HA, Vogel A, Herrmann A, Wessig P, Huster D, Müller P. Structure and Dynamics of Molecular Rods in Membranes: Application of a Spin-Labeled Rod. Chemistry 2013; 19:2703-10. [DOI: 10.1002/chem.201202500] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Revised: 11/19/2012] [Indexed: 11/07/2022]
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37
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Weise K, Huster D, Kapoor S, Triola G, Waldmann H, Winter R. Gibbs energy determinants of lipoprotein insertion into lipid membranes: the case study of Ras proteins. Faraday Discuss 2013; 161:549-61; discussion 563-89. [DOI: 10.1039/c2fd20100c] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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38
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Schade M, Knoll A, Vogel A, Seitz O, Liebscher J, Huster D, Herrmann A, Arbuzova A. Remote control of lipophilic nucleic acids domain partitioning by DNA hybridization and enzymatic cleavage. J Am Chem Soc 2012; 134:20490-7. [PMID: 23163619 DOI: 10.1021/ja309256t] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Lateral partitioning of lipid-modified molecules between liquid-disordered (ld) and liquid-ordered (lo) domains depends on the type of lipid modification, presence of a spacer, membrane composition, and temperature. Here, we show that the lo domain partitioning of the palmitoylated peptide nucleic acid (PNA) can be influenced by formation of a four-component complex with the ld domain partitioning tocopherol-modified DNA: the PNA-DNA complex partitioned into the ld domains. Enzymatic cleavage of the DNA linker led to the disruption of the complex and restored the initial distribution of the lipophilic nucleic acids into the respective domains. This modular system offers strategies for dynamic functionalization of biomimetic surfaces, for example, in nanostructuring and regulation of enzyme catalysis, and it provides a tool to study the molecular basis of controlled reorganization of lipid-modified proteins in membranes, for example, during signal transduction.
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Affiliation(s)
- Matthias Schade
- Institute of Biology/Biophysics, Humboldt-University Berlin, Invalidenstrasse 42, 10115 Berlin, Germany
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39
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Veit M, Engel S, Thaa B, Scolari S, Herrmann A. Lipid domain association of influenza virus proteins detected by dynamic fluorescence microscopy techniques. Cell Microbiol 2012; 15:179-89. [PMID: 23057766 DOI: 10.1111/cmi.12045] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Revised: 09/16/2012] [Accepted: 09/17/2012] [Indexed: 01/31/2023]
Abstract
Influenza virus is thought to assemble in raft domains of the plasma membrane, but many of the conclusions were based on (controversial) Triton extraction experiments. Here we review how sophisticated methods of fluorescence microscopy, such as FPALM, FRET and FRAP, contributed to our understanding of lipid domain association of the viral proteins HA and M2. The results are summarized in light of the current model for virus assembly and lipid domain organization. Finally, it is described how the signals that govern domain association in transfected cells affect replication of influenza virus.
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Affiliation(s)
- Michael Veit
- Institute of Immunology, Free University Berlin, Philippstr. 13, 10115 Berlin, Germany.
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40
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Li Z, Janosi L, Gorfe AA. Formation and domain partitioning of H-ras peptide nanoclusters: effects of peptide concentration and lipid composition. J Am Chem Soc 2012; 134:17278-85. [PMID: 22994893 PMCID: PMC3479155 DOI: 10.1021/ja307716z] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Experiments have shown that homologous Ras proteins containing different lipid modification, which is required for membrane binding, form nonoverlapping nanoclusters on the plasma membrane. However, the physical basis for clustering and lateral organization remains poorly understood. We have begun to tackle this issue using coarse-grained molecular dynamics simulations of the H-ras lipid anchor (tH), a triply lipid-modified heptapeptide embedded in a domain-forming mixed lipid bilayer [Janosi L. et al. Proc. Natl. Acad. Sci. U.S.A. 2012, 109, 8097]. Here we use the same simulation approach to investigate the effect of peptide concentration and bilayer composition on the clustering and lateral distribution of tH. We found no major difference in the clustering behavior of tH above a certain concentration. However, the simulations predict the existence of a critical concentration below which tH does not form nanoclusters. Moreover, our data demonstrate that cholesterol enhances the stability of tH nanoclusters but is not required for their formation. Finally, analyses of peptide distributions and partition free energies allowed us to quantitatively describe how clustering facilitates the accumulation of tH at the interface between ordered and disordered domains of the simulated bilayer systems. These thermodynamic insights represent some of the key elements for a comprehensive understanding of the molecular basis for the formation and stability of Ras signaling platforms.
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Affiliation(s)
- Zhenlong Li
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, 6431 Fannin St., Houston, Texas 77030, USA
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41
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The role of G-domain orientation and nucleotide state on the Ras isoform-specific membrane interaction. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2012; 41:801-13. [PMID: 22851002 DOI: 10.1007/s00249-012-0841-5] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Revised: 06/26/2012] [Accepted: 07/10/2012] [Indexed: 12/21/2022]
Abstract
Ras proteins are proto-oncogenes that function as molecular switches linking extracellular stimuli with an overlapping but distinctive range of biological outcomes. Although modulatable interactions between the membrane and the Ras C-terminal hypervariable region (HVR) harbouring the membrane anchor motifs enable signalling specificity to be determined by their location, it is becoming clear that the spatial orientation of different Ras proteins is also crucial for their functions. To reveal the orientation of the G-domain at membranes, we conducted an extensive study on different Ras isoforms anchored to model raft membranes. The results show that the G-domain mediates the Ras-membrane interaction by inducing different sets of preferred orientations in the active and inactive states with largely parallel orientation relative to the membrane of most of the helices. The distinct locations of the different isoforms, exposing them to different effectors and regulators, coupled with different G-domain-membrane orientation, suggests synergy between this type of recognition motif and the specificity conferred by the HVR, thereby validating the concept of isoform specificity in Ras.
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42
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Weise K, Kapoor S, Werkmüller A, Möbitz S, Zimmermann G, Triola G, Waldmann H, Winter R. Dissociation of the K-Ras4B/PDEδ complex upon contact with lipid membranes: membrane delivery instead of extraction. J Am Chem Soc 2012; 134:11503-10. [PMID: 22721555 DOI: 10.1021/ja305518h] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
K-Ras4B is a small GTPase whose selective membrane localization and clustering into microdomains are mediated by its polybasic farnesylated C-terminus. The importance of the subcellular distribution for the signaling activity of K-Ras4B became apparent from recent in vivo studies, showing that the delta subunit of cGMP phosphodiesterase (PDEδ), which possesses a hydrophobic prenyl-binding pocket, is able to function as a potential binding partner for farnesylated proteins, thereby leading to a modulation of the spatiotemporal organization of K-Ras. Even though PDEδ has been suggested to serve as a cytosolic carrier for Ras, the functional transport mechanism still remains largely elusive. In this study, the effect of PDEδ on the interaction of GDP- and GTP-loaded K-Ras4B with neutral and anionic model biomembranes has been investigated by a combination of different spectroscopic and imaging techniques. The results show that PDEδ is not able to extract K-Ras4B from membranes. Rather, the K-Ras4B/PDEδ complex formed in bulk solution turned out to be unstable in the presence of heterogeneous membranes, resulting in a release of farnesylated K-Ras4B upon membrane contact. With the additional observation of enhanced membrane affinity for the K-Ras4B/PDEδ complex, a molecular mechanism for the PDEδ-K-Ras4B-membrane interaction could be proposed. This includes an effective delivery of PDEδ-solubilized K-Ras4B to the plasma membrane, probably through cytoplasmic diffusion, the dissociation of the K-Ras4B/PDEδ complex upon plasma membrane contact, and finally the membrane binding of released farnesylated K-Ras4B that leads to K-Ras4B-enriched microdomain formation.
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Affiliation(s)
- Katrin Weise
- Physical Chemistry I-Biophysical Chemistry, Faculty of Chemistry, TU Dortmund University, Otto-Hahn-Strasse 6, D-44227 Dortmund, Germany
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43
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Olausson BES, Grossfield A, Pitman MC, Brown MF, Feller SE, Vogel A. Molecular dynamics simulations reveal specific interactions of post-translational palmitoyl modifications with rhodopsin in membranes. J Am Chem Soc 2012; 134:4324-31. [PMID: 22280374 DOI: 10.1021/ja2108382] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
We present a detailed analysis of the behavior of the highly flexible post-translational lipid modifications of rhodopsin from multiple-microsecond all-atom molecular dynamics simulations. Rhodopsin was studied in a realistic membrane environment that includes cholesterol, as well as saturated and polyunsaturated lipids with phosphocholine and phosphoethanolamine headgroups. The simulation reveals striking differences between the palmitoylations at Cys322 and Cys323 as well as between the palmitoyl chains and the neighboring lipids. Notably the palmitoyl group at Cys322 shows considerably greater contact with helix H1 of rhodopsin, yielding frequent chain upturns with longer reorientational correlation times, and relatively low order parameters. While the palmitoylation at Cys323 makes fewer protein contacts and has increased order compared to Cys322, it nevertheless exhibits greater flexibility with smaller order parameters than the stearoyl chains of the surrounding lipids. The dynamical structure of the palmitoylations-as well as their extensive fluctuations-suggests a complex function for the post-translational modifications in rhodopsin and potentially other G protein-coupled receptors, going beyond their role as membrane anchoring elements. Rather, we propose that the palmitoylation at Cys323 has a potential role as a lipid anchor, whereas the palmitoyl-protein interaction observed for Cys322 suggests a more specific interaction that affects the stability of the dark state of rhodopsin.
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Affiliation(s)
- Bjoern E S Olausson
- Institute of Pharmacy, Martin-Luther-University Halle-Wittenberg, D-06120 Halle/Saale, Germany
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Probing the lipid-protein interface using model transmembrane peptides with a covalently linked acyl chain. Biophys J 2012; 101:1959-67. [PMID: 22004750 DOI: 10.1016/j.bpj.2011.09.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2011] [Revised: 09/12/2011] [Accepted: 09/15/2011] [Indexed: 12/11/2022] Open
Abstract
The aim of this study was to gain insight into how interactions between proteins and lipids in membranes are sensed at the protein-lipid interface. As a probe to analyze this interface, we used deuterium-labeled acyl chains that were covalently linked to a model transmembrane peptide. First, a perdeuterated palmitoyl chain was coupled to the Trp-flanked peptide WALP23 (Ac-CGWW(LA)(8)LWWA-NH(2)), and the deuterium NMR spectrum was analyzed in di-C18:1-phosphatidylcholine (PC) bilayers. We found that the chain order of this peptide-linked chain is rather similar to that of a noncovalently coupled perdeuterated palmitoyl chain, except that it exhibits a slightly lower order. Similar results were obtained when site-specific deuterium labels were used and when the palmitoyl chain was attached to the more-hydrophobic model peptide WLP23 (Ac-CGWWL(17)WWA-NH(2)) or to the Lys-flanked peptide KALP23 (Ac-CGKK(LA)(8)LKKA-NH(2)). The experiments showed that the order of both the peptide-linked chains and the noncovalently coupled palmitoyl chains in the phospholipid bilayer increases in the order KALP23 < WALP23 < WLP23. Furthermore, changes in the bulk lipid bilayer thickness caused by varying the lipid composition from di-C14:1-PC to di-C18:1-PC or by including cholesterol were sensed rather similarly by the covalently coupled chain and the noncovalently coupled palmitoyl chains. The results indicate that the properties of lipids adjacent to transmembrane peptides mostly reflect the properties of the surrounding lipid bilayer, and hence that (at least for the single-span model peptides used in this study) annular lipids do not play a highly specific role in protein-lipid interactions.
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Ras trafficking, localization and compartmentalized signalling. Semin Cell Dev Biol 2011; 23:145-53. [PMID: 21924373 DOI: 10.1016/j.semcdb.2011.09.002] [Citation(s) in RCA: 169] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Accepted: 09/02/2011] [Indexed: 12/30/2022]
Abstract
Ras proteins are proto-oncogenes that are frequently mutated in human cancers. Three closely related isoforms, HRAS, KRAS and NRAS, are expressed in all cells and have overlapping but distinctive functions. Recent work has revealed how differences between the Ras isoforms in their trafficking, localization and protein-membrane orientation enable signalling specificity to be determined. We review the various strategies used to characterize compartmentalized Ras localization and signalling. Localization is an important contextual modifier of signalling networks and insights from the Ras system are of widespread relevance for researchers interested in signalling initiated from membranes.
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Vogel A, Roark M, Feller SE. A reinterpretation of neutron scattering experiments on a lipidated Ras peptide using replica exchange molecular dynamics. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:219-24. [PMID: 21872568 DOI: 10.1016/j.bbamem.2011.08.016] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Revised: 08/10/2011] [Accepted: 08/11/2011] [Indexed: 11/27/2022]
Abstract
The Ras family of proteins plays crucial roles in a variety of cell signaling networks where they have the function of a molecular switch. Their particular medical relevance arises from mutations in these proteins that are implicated in ~30% of human cancers. The various Ras proteins exhibit a high degree of homology in their soluble domains but extremely high variability in the membrane anchoring regions that are crucial for protein function and are the focus of this study. We have employed replica exchange molecular dynamics computer simulations to study a doubly lipidated heptapeptide, corresponding to the C-terminus of the human N-Ras protein, incorporated into a dimyristoylphosphatidylcholine lipid bilayer. This same system has previously been investigated experimentally utilizing a number of techniques, including neutron scattering. Here we present results of well converged simulations that describe the subtle changes in scattering density in terms of the location of the peptide and its lipid modifications and in terms of changes in phospholipid density arising from the incorporation of the peptide into the membrane bilayer. The detailed picture that emerges from the combination of experimental and computational data exemplifies the power of combining isotopic substitution neutron scattering with atomistic molecular dynamics simulation. This article is part of a Special Issue entitled: Membrane protein structure and function.
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Affiliation(s)
- Alexander Vogel
- Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, D-04275 Leipzig, Germany
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Penk A, Müller M, Scheidt HA, Langosch D, Huster D. Structure and dynamics of the lipid modifications of a transmembrane α-helical peptide determined by 2H solid-state NMR spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:784-91. [DOI: 10.1016/j.bbamem.2010.12.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2010] [Revised: 12/15/2010] [Accepted: 12/15/2010] [Indexed: 01/11/2023]
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The presence of membranes or micelles induces structural changes of the myristoylated guanylate-cyclase activating protein-2. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2011; 40:565-76. [DOI: 10.1007/s00249-011-0680-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2010] [Revised: 01/20/2011] [Accepted: 01/25/2011] [Indexed: 10/18/2022]
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Scheidt HA, Sickert A, Meier T, Castellucci N, Tomasini C, Huster D. The interaction of lipid modified pseudopeptides with lipid membranes. Org Biomol Chem 2011; 9:6998-7006. [DOI: 10.1039/c1ob05652b] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Weise K, Kapoor S, Denter C, Nikolaus J, Opitz N, Koch S, Triola G, Herrmann A, Waldmann H, Winter R. Membrane-mediated induction and sorting of K-Ras microdomain signaling platforms. J Am Chem Soc 2010; 133:880-7. [PMID: 21141956 DOI: 10.1021/ja107532q] [Citation(s) in RCA: 128] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The K-Ras4B GTPase is a major oncoprotein whose signaling activity depends on its correct localization to negatively charged subcellular membranes and nanoclustering in membrane microdomains. Selective localization and clustering are mediated by the polybasic farnesylated C-terminus of K-Ras4B, but the mechanisms and molecular determinants involved are largely unknown. In a combined chemical biological and biophysical approach we investigated the partitioning of semisynthetic fully functional lipidated K-Ras4B proteins into heterogeneous anionic model membranes and membranes composed of viral lipid extracts. Independent of GDP/GTP-loading, K-Ras4B is preferentially localized in liquid-disordered (l(d)) lipid domains and forms new protein-containing fluid domains that are recruiting multivalent acidic lipids by an effective, electrostatic lipid sorting mechanism. In addition, GDP-GTP exchange and, thereby, Ras activation results in a higher concentration of activated K-Ras4B in the nanoscale signaling platforms. Conversely, palmitoylated and farnesylated N-Ras proteins partition into the l(d) phase and concentrate at the l(d)/l(o) phase boundary of heterogeneous membranes. Next to the lipid anchor system, the results reveal an involvement of the G-domain in the membrane interaction process by determining minor but yet significant structural reorientations of the GDP/GTP-K-Ras4B proteins at lipid interfaces. A molecular mechanism for isoform-specific Ras signaling from separate membrane microdomains is postulated from the results of this study.
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Affiliation(s)
- Katrin Weise
- Physical Chemistry I, Biophysical Chemistry, Faculty of Chemistry, TU Dortmund University , Otto-Hahn-Strasse 6, D-44227 Dortmund, Germany
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