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Ali O, Szabó A. Review of Eukaryote Cellular Membrane Lipid Composition, with Special Attention to the Fatty Acids. Int J Mol Sci 2023; 24:15693. [PMID: 37958678 PMCID: PMC10649022 DOI: 10.3390/ijms242115693] [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: 09/18/2023] [Revised: 10/24/2023] [Accepted: 10/25/2023] [Indexed: 11/15/2023] Open
Abstract
Biological membranes, primarily composed of lipids, envelop each living cell. The intricate composition and organization of membrane lipids, including the variety of fatty acids they encompass, serve a dynamic role in sustaining cellular structural integrity and functionality. Typically, modifications in lipid composition coincide with consequential alterations in universally significant signaling pathways. Exploring the various fatty acids, which serve as the foundational building blocks of membrane lipids, provides crucial insights into the underlying mechanisms governing a myriad of cellular processes, such as membrane fluidity, protein trafficking, signal transduction, intercellular communication, and the etiology of certain metabolic disorders. Furthermore, comprehending how alterations in the lipid composition, especially concerning the fatty acid profile, either contribute to or prevent the onset of pathological conditions stands as a compelling area of research. Hence, this review aims to meticulously introduce the intricacies of membrane lipids and their constituent fatty acids in a healthy organism, thereby illuminating their remarkable diversity and profound influence on cellular function. Furthermore, this review aspires to highlight some potential therapeutic targets for various pathological conditions that may be ameliorated through dietary fatty acid supplements. The initial section of this review expounds on the eukaryotic biomembranes and their complex lipids. Subsequent sections provide insights into the synthesis, membrane incorporation, and distribution of fatty acids across various fractions of membrane lipids. The last section highlights the functional significance of membrane-associated fatty acids and their innate capacity to shape the various cellular physiological responses.
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Affiliation(s)
- Omeralfaroug Ali
- Agrobiotechnology and Precision Breeding for Food Security National Laboratory, Institute of Physiology and Animal Nutrition, Department of Animal Physiology and Health, Hungarian University of Agriculture and Life Sciences, Guba Sándor Str. 40, 7400 Kaposvár, Hungary;
| | - András Szabó
- Agrobiotechnology and Precision Breeding for Food Security National Laboratory, Institute of Physiology and Animal Nutrition, Department of Animal Physiology and Health, Hungarian University of Agriculture and Life Sciences, Guba Sándor Str. 40, 7400 Kaposvár, Hungary;
- HUN-REN-MATE Mycotoxins in the Food Chain Research Group, Hungarian University of Agriculture and Life Sciences, Guba Sándor Str. 40, 7400 Kaposvár, Hungary
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2
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Human cone elongation responses can be explained by photoactivated cone opsin and membrane swelling and osmotic response to phosphate produced by RGS9-catalyzed GTPase. Proc Natl Acad Sci U S A 2022; 119:e2202485119. [PMID: 36122241 PMCID: PMC9522364 DOI: 10.1073/pnas.2202485119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Optical coherence tomography has established that human cone photoreceptor outer segments elongate in response to stimuli bleaching large fractions of their visual pigment. Elongation responses are completely described over their 200-fold bleaching range as the sum of two exponentially rising components differing 13-fold in time constants and 4-fold in light sensitivity. Bleaching measurements of individual cones with adaptive optics scanning laser ophthalmoscopy (SLO) suggest that component 2 arises from cone opsin and disk membrane swelling triggered by photoactivation. Application of a model of phototransduction suggests that component 1 corresponds to free phosphate generated by regulator of G-protein signaling 9 (RGS9)-catalyzed hydrolysis of guanosine triphosphate (GTP) in the α-subunit of G protein complexed with phosphodiesterase. Human cone outer segment (COS) length changes in response to stimuli bleaching up to 99% of L- and M-cone opsins were measured with high resolution, phase-resolved optical coherence tomography (OCT). Responses comprised a fast phase (∼5 ms), during which COSs shrink, and two slower phases (1.5 s), during which COSs elongate. The slower components saturated in amplitude (∼425 nm) and initial rate (∼3 nm ms−1) and are well described over the 200-fold bleaching range as the sum of two exponentially rising functions with time constants of 80 to 90 ms (component 1) and 1,000 to 1,250 ms (component 2). Measurements with adaptive optics reflection densitometry revealed component 2 to be linearly related to cone pigment bleaching, and the hypothesis is proposed that it arises from cone opsin and disk membrane swelling triggered by isomerization and rate-limited by chromophore hydrolysis and its reduction to membrane-localized all-trans retinol. The light sensitivity and kinetics of component 1 suggested that the underlying mechanism is an osmotic response to an amplified soluble by-product of phototransduction. The hypotheses that component 1 corresponds to G-protein subunits dissociating from the membrane, metabolites of cyclic guanosine monophosphate (cGMP) hydrolysis, or by-products of activated guanylate cyclase are rejected, while the hypothesis that it corresponds to phosphate produced by regulator of G-protein signaling 9 (RGS9)-catalyzed hydrolysis of guanosine triphosphate (GTP) in G protein–phosphodiesterase complexes was found to be consistent with the results. These results provide a basis for the assessment with optoretinography of phototransduction in individual cone photoreceptors in health and during disease progression and therapeutic interventions.
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Millette MA, Roy S, Salesse C. Farnesylation and lipid unsaturation are critical for the membrane binding of the C-terminal segment of G-Protein Receptor Kinase 1. Colloids Surf B Biointerfaces 2022; 211:112315. [PMID: 35026543 DOI: 10.1016/j.colsurfb.2021.112315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 12/15/2021] [Accepted: 12/30/2021] [Indexed: 10/19/2022]
Abstract
Many proteins are modified by the covalent addition of different types of lipids, such as myristoylation, palmitoylation and prenylation. Lipidation is expected to promote membrane association of proteins. Visual phototransduction involves many lipid-modified proteins. The G-Protein-coupled receptor of rod photoreceptors, rhodopsin, is inactivated by G-Protein-coupled Receptor Kinase 1 (GRK1). The C-terminus of GRK1 is farnesylated and its truncation has been shown to result in a very high decrease of its enzymatic activity, most likely because of the loss of its membrane localization. Little information is available on the membrane binding of GRK1 as well as of most prenylated proteins. Measurements of the membrane binding of the non-farnesylated and farnesylated C-terminal segment of GRK1 were thus performed using lipids typical of those found in rod outer segment disk membranes. Their random coil secondary structure was determined using circular dichroism and infrared spectroscopy. The non-farnesylated C-terminal segment of GRK1 has no surface activity. In contrast, the farnesylated C-terminal segment of GRK1 shows a particularly strong binding to lipid monolayers bearing at least one unsaturated fatty acyl chain. No binding is observed in the presence of monolayers of saturated phospholipids, in agreement with the low affinity of farnesylated Ras proteins for lipids in the liquid-ordered state. Altogether, these data demonstrate that the farnesyl group of the C-terminal segment of GRK1 is mandatory for its membrane binding, which is favored by particular lipids or lipid mixtures. This information will also be useful for the understanding of the membrane binding of other prenylated proteins.
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Affiliation(s)
- Marc-Antoine Millette
- CUO-Recherche, Centre de recherche du CHU de Québec and Département d'ophtalmologie, Faculté de médecine, and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Sarah Roy
- CUO-Recherche, Centre de recherche du CHU de Québec and Département d'ophtalmologie, Faculté de médecine, and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Christian Salesse
- CUO-Recherche, Centre de recherche du CHU de Québec and Département d'ophtalmologie, Faculté de médecine, and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada.
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Pilecky M, Závorka L, Arts MT, Kainz MJ. Omega-3 PUFA profoundly affect neural, physiological, and behavioural competences - implications for systemic changes in trophic interactions. Biol Rev Camb Philos Soc 2021; 96:2127-2145. [PMID: 34018324 DOI: 10.1111/brv.12747] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Revised: 05/09/2021] [Accepted: 05/11/2021] [Indexed: 01/01/2023]
Abstract
In recent decades, much conceptual thinking in trophic ecology has been guided by theories of nutrient limitation and the flow of elements, such as carbon and nitrogen, within and among ecosystems. More recently, ecologists have also turned their attention to examining the value of specific dietary nutrients, in particular polyunsaturated fatty acids (PUFA), among which the omega-3 PUFA, especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) play a central role as essential components of neuronal cell membranes in many organisms. This review focuses on a new neuro-ecological approach stemming from the biochemical (mechanistic) and physiological (functional) role of DHA in neuronal cell membranes, in particular in conjunction with G-protein coupled receptors (GPCRs). We link the co-evolution of these neurological functions to metabolic dependency on dietary omega-3 PUFA. We outline ways in which deficiencies in dietary DHA supply may affect, cognition, vision, and behaviour, and ultimately, the biological fitness of consumers. We then review emerging evidence that changes in access to dietary omega-3 PUFA may ultimately have profound impacts on trophic interactions leading to potential changes in community structure and ecosystem functioning that, in turn, may affect the supply of DHA within and across ecosystems, including the supply for human consumption.
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Affiliation(s)
- Matthias Pilecky
- WasserCluster Lunz - Biologische Station, Inter-University Center for Aquatic Ecosystem Research, Dr. Carl-Kupelwieser Promenade 5, Lunz am See, 3293, Austria.,Department of Biomedical Research, Donau-Universität Krems, Dr. Karl Dorrek-Straße 30, Krems, 3500, Austria
| | - Libor Závorka
- WasserCluster Lunz - Biologische Station, Inter-University Center for Aquatic Ecosystem Research, Dr. Carl-Kupelwieser Promenade 5, Lunz am See, 3293, Austria
| | - Michael T Arts
- Department of Chemistry and Biology, Ryerson University, 350 Victoria St, Toronto, ON, M5B 2K3, Canada
| | - Martin J Kainz
- WasserCluster Lunz - Biologische Station, Inter-University Center for Aquatic Ecosystem Research, Dr. Carl-Kupelwieser Promenade 5, Lunz am See, 3293, Austria.,Department of Biomedical Research, Donau-Universität Krems, Dr. Karl Dorrek-Straße 30, Krems, 3500, Austria
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5
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Membrane binding properties of the C-terminal segment of retinol dehydrogenase 8. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2021; 1863:183605. [PMID: 33766534 DOI: 10.1016/j.bbamem.2021.183605] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 03/01/2021] [Accepted: 03/12/2021] [Indexed: 12/18/2022]
Abstract
Light absorption by rhodopsin leads to the release of all-trans retinal (ATRal) in the lipid phase of photoreceptor disc membranes. Retinol dehydrogenase 8 (RDH8) then reduces ATRal into all-trans retinol, which is the first step of the visual cycle. The membrane binding of RDH8 has been postulated to be mediated by one or more palmitoylated cysteines located in its C-terminus. Different peptide variants of the C-terminus of RDH8 were thus used to obtain information on the mechanism of membrane binding of this enzyme. Steady-state and time-resolved fluorescence measurements were performed using short and long C-terminal segments of bovine RDH8, comprising one or two tryptophan residues. The data demonstrate that the amphipathic alpha helical structure of the first portion of the C-terminus of RDH8 strongly contributes to its membrane binding, which is also favored by palmitoylation of at least one of the cysteines located in the last portion of the C-terminus.
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Bernier SC, Millette MA, Roy S, Cantin L, Coutinho A, Salesse C. Structural information and membrane binding of truncated RGS9-1 Anchor Protein and its C-terminal hydrophobic segment. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2021; 1863:183566. [PMID: 33453187 DOI: 10.1016/j.bbamem.2021.183566] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Revised: 12/22/2020] [Accepted: 01/10/2021] [Indexed: 01/19/2023]
Abstract
Visual phototransduction takes place in photoreceptor cells. Light absorption by rhodopsin leads to the activation of transducin as a result of the exchange of its GDP for GTP. The GTP-bound ⍺-subunit of transducin then activates phosphodiesterase (PDE), which in turn hydrolyzes cGMP leading to photoreceptor hyperpolarization. Photoreceptors return to the dark state upon inactivation of these proteins. In particular, PDE is inactivated by the protein complex R9AP/RGS9-1/Gβ5. R9AP (RGS9-1 anchor protein) is responsible for the membrane anchoring of this protein complex to photoreceptor outer segment disk membranes most likely by the combined involvement of its C-terminal hydrophobic domain as well as other types of interactions. This study thus aimed to gather information on the structure and membrane binding of the C-terminal hydrophobic segment of R9AP as well as of truncated R9AP (without its C-terminal domain, R9AP∆TM). Circular dichroism and infrared spectroscopic measurements revealed that the secondary structure of R9AP∆TM mainly includes ⍺-helical structural elements. Moreover, intrinsic fluorescence measurements of native R9AP∆TM and individual mutants lacking one tryptophan demonstrated that W79 is more buried than W173 but that they are both located in a hydrophobic environment. This method also revealed that membrane binding of R9AP∆TM does not involve regions near its tryptophan residues, while infrared spectroscopy validated its binding to lipid vesicles. Additional fluorescence measurements showed that the C-terminal segment of R9AP is membrane embedded. Maximum insertion pressure and synergy data using Langmuir monolayers suggest that interactions with specific phospholipids could be involved in the membrane binding of R9AP∆TM.
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Affiliation(s)
- Sarah C Bernier
- CUO-Recherche, Centre de recherche du CHU de Québec and Département d'ophtalmologie, Faculté de Médecine, and Regroupement Stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Marc-Antoine Millette
- CUO-Recherche, Centre de recherche du CHU de Québec and Département d'ophtalmologie, Faculté de Médecine, and Regroupement Stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Sarah Roy
- CUO-Recherche, Centre de recherche du CHU de Québec and Département d'ophtalmologie, Faculté de Médecine, and Regroupement Stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Line Cantin
- CUO-Recherche, Centre de recherche du CHU de Québec and Département d'ophtalmologie, Faculté de Médecine, and Regroupement Stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Ana Coutinho
- iBB-Institute for Bioengineering and Biosciences, Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal; Department of Chemistry and Biochemistry, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal
| | - Christian Salesse
- CUO-Recherche, Centre de recherche du CHU de Québec and Département d'ophtalmologie, Faculté de Médecine, and Regroupement Stratégique PROTEO, Université Laval, Québec, Québec, Canada.
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de Santis A, Vitiello G, Appavou MS, Scoppola E, Fragneto G, Barnsley LC, Clifton LA, Ottaviani MF, Paduano L, Russo Krauss I, D'Errico G. Not just a fluidifying effect: omega-3 phospholipids induce formation of non-lamellar structures in biomembranes. SOFT MATTER 2020; 16:10425-10438. [PMID: 33165495 DOI: 10.1039/d0sm01549k] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Polyunsaturated omega-3 fatty acid docosahexaenoic acid (DHA) is found in very high concentrations in a few peculiar tissues, suggesting that it must have a specialized role. DHA was proposed to affect the function of the cell membrane and related proteins through an indirect mechanism of action, based on the DHA-phospholipid effects on the lipid bilayer structure. In this respect, most studies have focused on its influence on lipid-rafts, somehow neglecting the analysis of effects on liquid disordered phases that constitute most of the cell membranes, by reporting in these cases only a general fluidifying effect. In this study, by combining neutron reflectivity, cryo-transmission electron microscopy, small angle neutron scattering, dynamic light scattering and electron paramagnetic resonance spectroscopy, we characterize liquid disordered bilayers formed by the naturally abundant 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine and different contents of a di-DHA glycero-phosphocholine, 22:6-22:6PC, from both a molecular/microscopic and supramolecular/mesoscopic viewpoint. We show that, below a threshold concentration of about 40% molar percent, incorporation of 22:6-22:6PC in the membrane increases the lipid dynamics slightly but sufficiently to promote the membrane deformation and increase of multilamellarity. Notably, beyond this threshold, 22:6-22:6PC disfavours the formation of lamellar phases, leading to a phase separation consisting mostly of small spherical particles that coexist with a minority portion of a lipid blob with water-filled cavities. Concurrently, from a molecular viewpoint, the polyunsaturated acyl chains tend to fold and expose the termini to the aqueous medium. We propose that this peculiar tendency is a key feature of the DHA-phospholipids making them able to modulate the local morphology of biomembranes.
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Affiliation(s)
- Augusta de Santis
- Department of Chemical Sciences, University of Naples Federico II, Naples, Italy.
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Kaneshige Y, Hayashi F, Morigaki K, Tanimoto Y, Yamashita H, Fujii M, Awazu A. Affinity of rhodopsin to raft enables the aligned oligomer formation from dimers: Coarse-grained molecular dynamics simulation of disk membranes. PLoS One 2020; 15:e0226123. [PMID: 32032370 PMCID: PMC7006936 DOI: 10.1371/journal.pone.0226123] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Accepted: 01/13/2020] [Indexed: 12/16/2022] Open
Abstract
The visual photopigment protein rhodopsin (Rh) is a typical G protein-coupled receptor (GPCR) that initiates the phototransduction cascade in retinal disk membrane of rod-photoreceptor cells. Rh molecule has a tendency to form dimer, and the dimer tends to form rows, which is suggested to heighten phototransduction efficiency in single-photon regime. In addition, the dimerization confers Rh an affinity for lipid raft, i.e. raftophilicity. However, the mechanism by which Rh-dimer raftophilicity contributes to the organization of the higher order structure remains unknown. In this study, we performed coarse-grained molecular dynamics simulations of a disk membrane model containing unsaturated lipids, saturated lipids with cholesterol, and Rh-dimers. We described the Rh-dimers by two-dimensional particle populations where the palmitoyl moieties of each Rh exhibits raftophilicity. We simulated the structuring of Rh in a disk for two types of Rh-dimer, i.e., the most and second most stable Rh dimers, which exposes the raftophilic regions at the dimerization-interface (H1/H8 dimer) and two edges away from the interface (H4/H5 dimer), respectively. Our simulations revealed that only the H1/H8 dimer could form a row structure. A small number of raftophilic lipids recruited to and intercalated in a narrow space between H1/H8 dimers stabilize the side-by-side interaction between dimers in a row. Our results implicate that the nano-sized lipid raft domains act as a “glue” to organize the long row structures of Rh-dimers.
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Affiliation(s)
- Yukito Kaneshige
- Department of Mathematical and Life Sciences, Hiroshima University, Kagamiyama, Higashi-Hiroshima, Japan
| | - Fumio Hayashi
- Graduate School of Science, Kobe University, Rokkodaicho, Nada, Kobe, Japan
| | - Kenichi Morigaki
- Biosignal Research Center, Kobe University, Rokkodaicho, Nada, Kobe, Japan
| | - Yasushi Tanimoto
- Graduate School of Science, Kobe University, Rokkodaicho, Nada, Kobe, Japan
| | - Hayato Yamashita
- Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, Japan
| | - Masashi Fujii
- Department of Mathematical and Life Sciences, Hiroshima University, Kagamiyama, Higashi-Hiroshima, Japan
| | - Akinori Awazu
- Department of Mathematical and Life Sciences, Hiroshima University, Kagamiyama, Higashi-Hiroshima, Japan
- * E-mail:
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Zhang P, Villanueva V, Kalkowski J, Liu C, Pham T, Perez-Salas U, Bu W, Lin B, Liu Y. Polyunsaturated Phospholipid Modified Membrane Degradation Catalyzed by a Secreted Phospholipase A2. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:11643-11650. [PMID: 31401834 DOI: 10.1021/acs.langmuir.9b01476] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
To optimize the compositions of the lipid-based nanomedicine and to advance understanding of the roles of polyunsaturated phospholipids in biological membranes, this study examined the effects of polyunsaturated phospholipids on the degradation of giant unilamellar vesicles catalyzed by a secreted phospholipase A2 (sPLA2) using fluorescence microscopy. Molecular interfacial packing, interaction, and degradation of the films containing various mixing ratios of saturated and polyunsaturated phospholipids were quantified using a Langmuir trough integrated with synchrotron X-ray surface scattering techniques. It was found that a high molar fraction (0.63 and above) of polyunsaturated phospholipids not only enhanced the rate of sPLA2-catalyzed vesicle degradation but also changed the vesicle deformation process and degradation product morphology. Hydrolysis of the saturated phospholipids generated highly ordered liquid crystal domains, which was reduced or prohibited by the presence of the polyunsaturated phospholipids in the reactant film.
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Affiliation(s)
| | | | | | | | | | | | - Wei Bu
- NSF's ChemMatCARS , University of Chicago , Chicago , Illinois 60637 , United States
| | - Binhua Lin
- NSF's ChemMatCARS , University of Chicago , Chicago , Illinois 60637 , United States
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Hayashi F, Saito N, Tanimoto Y, Okada K, Morigaki K, Seno K, Maekawa S. Raftophilic rhodopsin-clusters offer stochastic platforms for G protein signalling in retinal discs. Commun Biol 2019; 2:209. [PMID: 31240247 PMCID: PMC6570657 DOI: 10.1038/s42003-019-0459-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Accepted: 05/10/2019] [Indexed: 12/18/2022] Open
Abstract
Rhodopsin is a G protein-coupled receptor (GPCR) that initiates the phototransduction cascade in retinal disc membrane. Recent studies have suggested that rhodopsin forms highly ordered rows of dimers responsible for single-photon detection by rod photoreceptors. Dimerization is also known to confer to rhodopsin a high affinity for ordered lipids (raftophilicity). However, the role of rhodopsin organization and its raftophilicity in phototransduction remains obscure, owing to the lack of direct observation of rhodopsin dynamics and distribution in native discs. Here, we explore the single-molecule and semi-multimolecule behaviour of rhodopsin in native discs. Rhodopsin forms transient meso-scale clusters, even in darkness, which are loosely confined to the disc centre. Cognate G protein transducin co-distributes with rhodopsin, and exhibits lateral translocation to the disc periphery upon activation. We demonstrate that rhodopsin offers inherently distributed and stochastic platforms for G protein signalling by self-organizing raftophilic clusters, which continually repeat generation/extinction in the disc membrane.
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Affiliation(s)
- Fumio Hayashi
- Graduate School of Science, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501 Japan
| | - Natsumi Saito
- Graduate School of Science, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501 Japan
| | - Yasushi Tanimoto
- Research Centre for Environmental Genomics, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501 Japan
| | - Keisuke Okada
- Graduate School of Agriculture, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501 Japan
| | - Kenichi Morigaki
- Research Centre for Environmental Genomics, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501 Japan
- Graduate School of Agriculture, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501 Japan
| | - Keiji Seno
- Faculty of Medicine, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka, 431-3192 Japan
- International Mass Imaging Centre, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka, 431-3192 Japan
| | - Shohei Maekawa
- Graduate School of Science, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501 Japan
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11
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Mondal D, Dutta R, Banerjee P, Mukherjee D, Maiti TK, Sarkar N. Modulation of Membrane Fluidity Performed on Model Phospholipid Membrane and Live Cell Membrane: Revealing through Spatiotemporal Approaches of FLIM, FAIM, and TRFS. Anal Chem 2019; 91:4337-4345. [PMID: 30821145 DOI: 10.1021/acs.analchem.8b04044] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have elucidated the role of unsaturated fatty acid in the in vitro model phospholipid membrane and in vivo live cell membrane. Fluorescence microscopy and time-resolved fluorescence spectroscopy have been employed to uncover how modulation of vesicle bilayer fluidity persuades structural transformation. This unsaturation induced structural transformation due to packing disorder in bilayer has been delineated through spatially resolved fluorescence lifetime imaging microscopy (FLIM) and fluorescence polarization or anisotropy imaging microscopy (FPIM/FAIM). Structure-function relationship of phospholipid vesicle is also investigated by monitoring intervesicular water dynamics behavior, which has been demonstrated by temporally resolved fluorescence spectroscopy (TRFS) techniques. Nevertheless, it has also been manifested from this study that loss of rigidity in bilayer breaks down the strong hydrogen bond (H-bond) network around the charged lipid head groups. The disruption of this H-bond network increases the bilayer elasticity, which helps to evolve various kinds of vesicular structure. Furthermore, the significant influence of unsaturated fatty acid on membrane bilayer has been ratified through in vivo live cell imaging.
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Affiliation(s)
- Dipankar Mondal
- Department of Chemistry , Indian Institute of Technology , Kharagpur 721302 , West Bengal , India
| | - Rupam Dutta
- Department of Chemistry , Indian Institute of Technology , Kharagpur 721302 , West Bengal , India
| | - Pavel Banerjee
- Department of Chemistry , Indian Institute of Technology , Kharagpur 721302 , West Bengal , India
| | - Devdeep Mukherjee
- Department of Biotechnology , Indian Institute of Technology , Kharagpur 721302 , West Bengal , India
| | - Tapas Kumar Maiti
- Department of Biotechnology , Indian Institute of Technology , Kharagpur 721302 , West Bengal , India
| | - Nilmoni Sarkar
- Department of Chemistry , Indian Institute of Technology , Kharagpur 721302 , West Bengal , India
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Seno K, Hayashi F. Palmitoylation is a prerequisite for dimerization-dependent raftophilicity of rhodopsin. J Biol Chem 2017; 292:15321-15328. [PMID: 28747438 DOI: 10.1074/jbc.m117.804880] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 07/23/2017] [Indexed: 01/07/2023] Open
Abstract
The visual photopigment rhodopsin (Rh) is a prototypical G protein-coupled receptor (GPCR) responsible for initiation of the phototransduction cascade in rod photoreceptors. Similar to other GPCRs, Rh can form dimers or even higher oligomers and tends to have a supramolecular organization that is likely important in the dim light response. Rh also exhibits high affinity for lipid rafts (i.e. raftophilicity) upon light-dependent binding with the cognate G protein transducin (Gt), suggesting the presence of lipid raft-like domains in the retinal disk membrane and their importance in phototransduction. However, the relationship between Rh oligomerization and lipid rafts in the disk membrane remains to be explored. Given previous findings that Gt binds to dimeric Rh and that Rh is posttranslationally modified with two highly raftophilic palmitoyl moieties, we hypothesized that Rh becomes raftophilic upon dimerization. Here, using biochemical assays, we found that Rh*-Gt complexes in the detergent-resistant membrane are partially resistant to cholesterol depletion by methyl-β-cyclodextrin and that the Rh-to-Gt stoichiometry in this methyl-β-cyclodextrin-resistant complex is 2:1. Next, we found that IgG-mediated Rh-Rh cross-linking renders Rh highly raftophilic, supporting the premise that Rh becomes raftophilic upon dimerization. Rh depalmitoylation via reduction of thioester linkages blocked the translocation of IgG-cross-linked Rh to the detergent-resistant membrane, highlighting that the two palmitoyl moieties are important for the dimerization-dependent raftophilicity of Rh. These results indicate that palmitoylated GPCRs such as Rh can acquire raftophilicity upon G protein-stabilized dimerization and thereby organize receptor-cluster rafts by recruiting raftophilic lipids.
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Affiliation(s)
- Keiji Seno
- From the Department of Biology, Faculty of Medicine, and.,International Mass Imaging Center, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan and
| | - Fumio Hayashi
- the Department of Biology, Graduate School of Science, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan
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13
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Boisselier É, Demers É, Cantin L, Salesse C. How to gather useful and valuable information from protein binding measurements using Langmuir lipid monolayers. Adv Colloid Interface Sci 2017; 243:60-76. [PMID: 28372794 DOI: 10.1016/j.cis.2017.03.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Revised: 03/14/2017] [Accepted: 03/15/2017] [Indexed: 12/22/2022]
Abstract
This review presents data on the influence of various experimental parameters on the binding of proteins onto Langmuir lipid monolayers. The users of the Langmuir methodology are often unaware of the importance of choosing appropriate experimental conditions to validate the data acquired with this method. The protein Retinitis pigmentosa 2 (RP2) has been used throughout this review to illustrate the influence of these experimental parameters on the data gathered with Langmuir monolayers. The methods detailed in this review include the determination of protein binding parameters from the measurement of adsorption isotherms, infrared spectra of the protein in solution and in monolayers, ellipsometric isotherms and fluorescence micrographs.
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Affiliation(s)
- Élodie Boisselier
- CUO-Recherche, Hôpital du Saint-Sacrement, Centre de recherche du CHU de Québec and Département d'ophtalmologie, Faculté de médecine, and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada.
| | - Éric Demers
- CUO-Recherche, Hôpital du Saint-Sacrement, Centre de recherche du CHU de Québec and Département d'ophtalmologie, Faculté de médecine, and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Line Cantin
- CUO-Recherche, Hôpital du Saint-Sacrement, Centre de recherche du CHU de Québec and Département d'ophtalmologie, Faculté de médecine, and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Christian Salesse
- CUO-Recherche, Hôpital du Saint-Sacrement, Centre de recherche du CHU de Québec and Département d'ophtalmologie, Faculté de médecine, and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada.
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14
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In vivo optophysiology reveals that G-protein activation triggers osmotic swelling and increased light scattering of rod photoreceptors. Proc Natl Acad Sci U S A 2017; 114:E2937-E2946. [PMID: 28320964 DOI: 10.1073/pnas.1620572114] [Citation(s) in RCA: 77] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The light responses of rod and cone photoreceptors have been studied electrophysiologically for decades, largely with ex vivo approaches that disrupt the photoreceptors' subretinal microenvironment. Here we report the use of optical coherence tomography (OCT) to measure light-driven signals of rod photoreceptors in vivo. Visible light stimulation over a 200-fold intensity range caused correlated rod outer segment (OS) elongation and increased light scattering in wild-type mice, but not in mice lacking the rod G-protein alpha subunit, transducin (Gαt), revealing these responses to be triggered by phototransduction. For stimuli that photoactivated one rhodopsin per Gαt the rod OS swelling response reached a saturated elongation of 10.0 ± 2.1%, at a maximum rate of 0.11% s-1 Analyzing swelling as osmotically driven water influx, we find the H2O membrane permeability of the rod OS to be (2.6 ± 0.4) × 10-5 cm⋅s-1, comparable to that of other cells lacking aquaporin expression. Application of Van't Hoff's law reveals that complete activation of phototransduction generates a potentially harmful 20% increase in OS osmotic pressure. The increased backscattering from the base of the OS is explained by a model combining cytoplasmic swelling, translocation of dissociated G-protein subunits from the disc membranes into the cytoplasm, and a relatively higher H2O permeability of nascent discs in the basal rod OS. Translocation of phototransduction components out of the OS may protect rods from osmotic stress, which could be especially harmful in disease conditions that affect rod OS structural integrity.
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15
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Stillwell W. The role of polyunsaturated lipids in membrane raft function. SCANDINAVIAN JOURNAL OF FOOD & NUTRITION 2016. [DOI: 10.1080/17482970601066165] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- William Stillwell
- Department of BiologyIndiana University–Purdue UniversityIndianapolisUSA
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16
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Periole X. Interplay of G Protein-Coupled Receptors with the Membrane: Insights from Supra-Atomic Coarse Grain Molecular Dynamics Simulations. Chem Rev 2016; 117:156-185. [PMID: 28073248 DOI: 10.1021/acs.chemrev.6b00344] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
G protein-coupled receptors (GPCRs) are central to many fundamental cellular signaling pathways. They transduce signals from the outside to the inside of cells in physiological processes ranging from vision to immune response. It is extremely challenging to look at them individually using conventional experimental techniques. Recently, a pseudo atomistic molecular model has emerged as a valuable tool to access information on GPCRs, more specifically on their interactions with their environment in their native cell membrane and the consequences on their supramolecular organization. This approach uses the Martini coarse grain (CG) model to describe the receptors, lipids, and solvent in molecular dynamics (MD) simulations and in enough detail to allow conserving the chemical specificity of the different molecules. The elimination of unnecessary degrees of freedom has opened up large-scale simulations of the lipid-mediated supramolecular organization of GPCRs. Here, after introducing the Martini CGMD method, we review these studies carried out on various members of the GPCR family, including rhodopsin (visual receptor), opioid receptors, adrenergic receptors, adenosine receptors, dopamine receptor, and sphingosine 1-phosphate receptor. These studies have brought to light an interesting set of novel biophysical principles. The insights range from revealing localized and heterogeneous deformations of the membrane bilayer at the surface of the protein, specific interactions of lipid molecules with individual GPCRs, to the effect of the membrane matrix on global GPCR self-assembly. The review ends with an overview of the lessons learned from the use of the CGMD method, the biophysical-chemical findings on lipid-protein interplay.
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Affiliation(s)
- Xavier Periole
- Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 7, 9747AG Groningen, The Netherlands
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17
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Lin X, Lorent JH, Skinkle AD, Levental KR, Waxham MN, Gorfe AA, Levental I. Domain Stability in Biomimetic Membranes Driven by Lipid Polyunsaturation. J Phys Chem B 2016; 120:11930-11941. [PMID: 27797198 DOI: 10.1021/acs.jpcb.6b06815] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Biological membranes contain a broad variety of lipid species whose individual physicochemical properties and collective interactions ultimately determine membrane organization. A key aspect of the organization of cellular membranes is their lateral subdivision into domains of distinct structure and composition. The most widely studied membrane domains are lipid rafts, which are the biological manifestations of liquid-ordered phases that form in sterol-containing membranes. Detailed studies of biomimetic membrane mixtures have yielded wide-ranging insights into the physical principles behind lipid rafts; however, these simplified models do not fully capture the diversity and complexity of the mammalian lipidome, most notably in their exclusion of polyunsaturated lipids. Here, we assess the role of lipid acyl chain unsaturation as a driving force for phase separation using coarse-grained molecular dynamics (CGMD) simulations validated by model membrane experiments. The clear trends in our observations and good qualitative agreements between simulations and experiments support the conclusions that highly unsaturated lipids promote liquid-liquid domain stability by enhancing the differences in cholesterol content and lipid chain order between the coexisting domains. These observations reveal the important role of noncanonical biological lipids in the physical properties of membranes, showing that lipid polyunsaturation is a driving force for liquid-liquid phase separation.
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Affiliation(s)
- Xubo Lin
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston , Houston, Texas 77030, United States
| | - Joseph H Lorent
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston , Houston, Texas 77030, United States
| | - Allison D Skinkle
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston , Houston, Texas 77030, United States
| | - Kandice R Levental
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston , Houston, Texas 77030, United States
| | - M Neal Waxham
- Department of Neurobiology and Anatomy, McGovern Medical School, The University of Texas Health Science Center at Houston , Houston, Texas 77030, United States
| | - Alemayehu A Gorfe
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston , Houston, Texas 77030, United States
| | - Ilya Levental
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston , Houston, Texas 77030, United States
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18
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Calvez P, Schmidt TF, Cantin L, Klinker K, Salesse C. Phosphatidylserine Allows Observation of the Calcium–Myristoyl Switch of Recoverin and Its Preferential Binding. J Am Chem Soc 2016; 138:13533-13540. [DOI: 10.1021/jacs.6b04218] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Philippe Calvez
- CUO-Recherche, Centre de
recherche du CHU de Québec, Hôpital du Saint-Sacrement,
Département d’ophtalmologie, Faculté de Médecine,
and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, G1S 4L8 Canada
| | - Thaís F. Schmidt
- CUO-Recherche, Centre de
recherche du CHU de Québec, Hôpital du Saint-Sacrement,
Département d’ophtalmologie, Faculté de Médecine,
and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, G1S 4L8 Canada
| | - Line Cantin
- CUO-Recherche, Centre de
recherche du CHU de Québec, Hôpital du Saint-Sacrement,
Département d’ophtalmologie, Faculté de Médecine,
and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, G1S 4L8 Canada
| | - Kristina Klinker
- CUO-Recherche, Centre de
recherche du CHU de Québec, Hôpital du Saint-Sacrement,
Département d’ophtalmologie, Faculté de Médecine,
and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, G1S 4L8 Canada
| | - Christian Salesse
- CUO-Recherche, Centre de
recherche du CHU de Québec, Hôpital du Saint-Sacrement,
Département d’ophtalmologie, Faculté de Médecine,
and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, G1S 4L8 Canada
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19
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Kullberg A, Ekholm OO, Slotte JP. Miscibility of Sphingomyelins and Phosphatidylcholines in Unsaturated Phosphatidylcholine Bilayers. Biophys J 2016; 109:1907-16. [PMID: 26536267 DOI: 10.1016/j.bpj.2015.09.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Revised: 08/26/2015] [Accepted: 09/11/2015] [Indexed: 10/22/2022] Open
Abstract
Polyunsaturated phospholipids are common in biological membranes and affect the lateral structure of bilayers. We have examined how saturated sphingomyelin (SM; palmitoyl and stearoyl SM (PSM and SSM, respectively)) and phosphatidylcholine (PC; dipalmitoyl PC and 1-palmitoyl-2-stearoyl PC (DPPC and PSPC, respectively)) segregate laterally to form ordered gel phases in increasingly unsaturated PC bilayers (sn-1: 16:0 and sn-2: 18:1...22:6; or sn-1 and sn-2: 18:1...22:6). The formation of gel phases was determined from the lifetime analysis of trans-parinaric acid. Using calorimetry, we also determined gel phase formation by PSM and DPPC in unsaturated PC mixed bilayers. Comparing PSM with DPPC, we observed that PSM formed a gel phase with less order than DPPC at comparable bilayer concentrations. The same was true when SSM was compared with PSPC. Furthermore, we observed that at equal saturated phospholipid concentration, the gel phases formed were less ordered in unsaturated PCs having 16:0 in sn-1, as compared to PCs having unsaturated acyl chains in both sn-1 and sn-2. The gel phases formed by the saturated phospholipids in unsaturated PC bilayers did not appear to achieve properties similar to pure saturated phospholipid bilayers, suggesting that complete lateral phase separation did not occur. Based on scanning calorimetry analysis, the melting of the gel phases formed by PSM and DPPC in unsaturated PC mixed bilayers (at 45 mol % saturated phospholipid) had low cooperativity and hence most likely were of mixed composition, in good agreement with trans-parinaric acid lifetime data. We conclude that both interfacial properties of the saturated phospholipids and their chain length, as well as the presence of 16:0 in sn-1 of the unsaturated PCs and the total number of cis unsaturations and acyl chain length (18 to 22) of the unsaturated PCs, all affected the formation of gel phases enriched in saturated phospholipids, under the conditions used.
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Affiliation(s)
- Anders Kullberg
- Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland
| | - Oscar Oz Ekholm
- Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland
| | - J Peter Slotte
- Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland.
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20
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Potvin-Fournier K, Lefèvre T, Picard-Lafond A, Marcotte C, Dufresne C, Cantin L, Salesse C, Auger M. Discriminating Lipid– from Protein–Calcium Binding To Understand the Interaction between Recoverin and Phosphatidylglycerol Model Membranes. Biochemistry 2016; 55:3481-91. [DOI: 10.1021/acs.biochem.6b00408] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Kim Potvin-Fournier
- Département
de chimie, Regroupement québécois de recherche sur la
fonction, l’ingénierie et les applications des protéines
(PROTEO), Centre de recherche sur les matériaux avancés
(CERMA), Centre québécois sur les matériaux fonctionnels
(CQMF), Université Laval, Pavillon Alexandre-Vachon, 1045
avenue de la médecine, Québec, Québec G1V 0A6, Canada
- CUO-recherche,
Centre de recherche du CHU de Québec, Hôpital du Saint-Sacrement,
Département d’ophtalmologie, Faculté de médecine,
PROTEO, Université Laval, Québec, Québec G1S 4L8, Canada
| | - Thierry Lefèvre
- Département
de chimie, Regroupement québécois de recherche sur la
fonction, l’ingénierie et les applications des protéines
(PROTEO), Centre de recherche sur les matériaux avancés
(CERMA), Centre québécois sur les matériaux fonctionnels
(CQMF), Université Laval, Pavillon Alexandre-Vachon, 1045
avenue de la médecine, Québec, Québec G1V 0A6, Canada
| | - Audrey Picard-Lafond
- Département
de chimie, Regroupement québécois de recherche sur la
fonction, l’ingénierie et les applications des protéines
(PROTEO), Centre de recherche sur les matériaux avancés
(CERMA), Centre québécois sur les matériaux fonctionnels
(CQMF), Université Laval, Pavillon Alexandre-Vachon, 1045
avenue de la médecine, Québec, Québec G1V 0A6, Canada
| | - Catherine Marcotte
- Département
de chimie, Regroupement québécois de recherche sur la
fonction, l’ingénierie et les applications des protéines
(PROTEO), Centre de recherche sur les matériaux avancés
(CERMA), Centre québécois sur les matériaux fonctionnels
(CQMF), Université Laval, Pavillon Alexandre-Vachon, 1045
avenue de la médecine, Québec, Québec G1V 0A6, Canada
| | - Caroline Dufresne
- Département
de chimie, Regroupement québécois de recherche sur la
fonction, l’ingénierie et les applications des protéines
(PROTEO), Centre de recherche sur les matériaux avancés
(CERMA), Centre québécois sur les matériaux fonctionnels
(CQMF), Université Laval, Pavillon Alexandre-Vachon, 1045
avenue de la médecine, Québec, Québec G1V 0A6, Canada
| | - Line Cantin
- CUO-recherche,
Centre de recherche du CHU de Québec, Hôpital du Saint-Sacrement,
Département d’ophtalmologie, Faculté de médecine,
PROTEO, Université Laval, Québec, Québec G1S 4L8, Canada
| | - Christian Salesse
- CUO-recherche,
Centre de recherche du CHU de Québec, Hôpital du Saint-Sacrement,
Département d’ophtalmologie, Faculté de médecine,
PROTEO, Université Laval, Québec, Québec G1S 4L8, Canada
| | - Michèle Auger
- Département
de chimie, Regroupement québécois de recherche sur la
fonction, l’ingénierie et les applications des protéines
(PROTEO), Centre de recherche sur les matériaux avancés
(CERMA), Centre québécois sur les matériaux fonctionnels
(CQMF), Université Laval, Pavillon Alexandre-Vachon, 1045
avenue de la médecine, Québec, Québec G1V 0A6, Canada
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21
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Lor C, Hirst LS. Effects of Low Concentrations of Docosahexaenoic Acid on the Structure and Phase Behavior of Model Lipid Membranes. MEMBRANES 2015; 5:857-74. [PMID: 26690231 PMCID: PMC4704016 DOI: 10.3390/membranes5040857] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Accepted: 11/25/2015] [Indexed: 11/21/2022]
Abstract
In this paper we report an X-ray diffraction study on the phase behavior of binary lipid mixtures of 1-palmitoyl-2-docosahexaenoyl-sn-glycero-3-phosphoethanolamine (DHA-PE) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) at low concentrations below 5.0 mol% DHA-PE. Our results show that DHA-PE induces phase separation into a DHA rich liquid crystalline (Lα) phase and a DHA poor gel (Lβ') phase at overall DHA-PE concentrations as low as 0.1 mol%. In addition, we find that the structure of the Lβ' phase, from which the DHA-PE molecules are largely excluded, is modified in the phase-separated state at low DHA-PE concentrations, with a decrease in bilayer thickness of 1.34 nm for 0.1 mol% at room temperature, compared to pure DPPC bilayers. This result is contrary to that seen in similar studies on mono-unsaturated lipids where an increase in bilayer thickness is observed. The surprising effect of such low DHA-PE concentrations on membrane structure may be important in understanding the role of highly polyunsaturated lipids in biological membrane-based structures and similar artificial surfactant systems.
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Affiliation(s)
- Chai Lor
- Bioengineering and Small Scale Technologies, School of Engineering, University of California, Merced, CA 95343, USA.
| | - Linda S Hirst
- Department of Physics, School of Natural Sciences, University of California, Merced, CA 95343, USA.
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22
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Demers É, Boisselier É, Horchani H, Blaudez D, Calvez P, Cantin L, Belley N, Champagne S, Desbat B, Salesse C. Lipid Selectivity, Orientation, and Extent of Membrane Binding of Nonacylated RP2. Biochemistry 2015; 54:2560-70. [DOI: 10.1021/bi501517r] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Éric Demers
- CUO-Recherche,
Hôpital du Saint-Sacrement, Centre de recherche du CHU de Québec
and Département d’ophtalmologie, Faculté de médecine,
and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Élodie Boisselier
- CUO-Recherche,
Hôpital du Saint-Sacrement, Centre de recherche du CHU de Québec
and Département d’ophtalmologie, Faculté de médecine,
and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Habib Horchani
- CUO-Recherche,
Hôpital du Saint-Sacrement, Centre de recherche du CHU de Québec
and Département d’ophtalmologie, Faculté de médecine,
and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Daniel Blaudez
- CBMN-UMR
5248 CNRS, Université de Bordeaux, IPB, Allée Geoffroy
Saint Hilaire, 33600 Pessac, France
| | - Philippe Calvez
- CUO-Recherche,
Hôpital du Saint-Sacrement, Centre de recherche du CHU de Québec
and Département d’ophtalmologie, Faculté de médecine,
and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Line Cantin
- CUO-Recherche,
Hôpital du Saint-Sacrement, Centre de recherche du CHU de Québec
and Département d’ophtalmologie, Faculté de médecine,
and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Nicolas Belley
- CUO-Recherche,
Hôpital du Saint-Sacrement, Centre de recherche du CHU de Québec
and Département d’ophtalmologie, Faculté de médecine,
and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Sophie Champagne
- CUO-Recherche,
Hôpital du Saint-Sacrement, Centre de recherche du CHU de Québec
and Département d’ophtalmologie, Faculté de médecine,
and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Bernard Desbat
- CBMN-UMR
5248 CNRS, Université de Bordeaux, IPB, Allée Geoffroy
Saint Hilaire, 33600 Pessac, France
| | - Christian Salesse
- CUO-Recherche,
Hôpital du Saint-Sacrement, Centre de recherche du CHU de Québec
and Département d’ophtalmologie, Faculté de médecine,
and Regroupement stratégique PROTEO, Université Laval, Québec, Québec, Canada
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23
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Bernier SC, Horchani H, Salesse C. Structure and binding of the C-terminal segment of R9AP to lipid monolayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:1967-1979. [PMID: 25614992 DOI: 10.1021/la503867h] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Phototransduction cascade takes place in disc membranes of photoreceptor cells. Following its activation by light, rhodopsin activates the G-protein transducin causing the dissociation of its GTP-bound α-subunit, which in turn activates phosphodiesterase 6 (PDE6) leading to the hyperpolarization of photoreceptor cells. PDE6 must then be inactivated to return to the dark state. This is achieved by a protein complex which is presumably anchored to photoreceptor disc membranes by means of the transmembrane C-terminal segment of RGS9-1-Anchor Protein (R9AP). Information on the secondary structure and membrane binding properties of the C-terminal segment of R9AP is not yet available to further support its role in the membrane anchoring of this protein. In the present study, circular dichroism and infrared spectroscopy measurements have allowed us to determine that the C-terminal segment of human and bovine R9AP adopts an α-helical structure in solution. Moreover, this C-terminal segment has shown affinity for most of the phospholipids typical of photoreceptor membranes. In fact, the physical state and the type of phospholipid as well as electrostatic interactions influence the binding of the human and bovine peptides to phospholipid monolayers. In addition, these measurements revealed that the human peptide has a high affinity for saturated phosphocholine, which may suggest a possible localization of R9AP in photoreceptor microdomains. Accordingly, infrared spectroscopy measurements have allowed determining that the C-terminal segment of R9AP adopts an ordered α-helical structure in the presence of saturated phospholipid monolayers. Altogether, these data are consistent with the typical α-helical secondary structure and behavior observed for transmembrane segments and with the proposed role of membrane anchoring of the C-terminal segment of human and bovine R9AP.
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Affiliation(s)
- Sarah C Bernier
- CUO-Recherche, Centre de recherche du CHU de Québec and Département d'ophtalmologie, Faculté de médecine, and Regroupement stratégique PROTEO, Université Laval , Québec (Québec) Canada
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24
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ATP-binding cassette transporter ABCA4 and chemical isomerization protect photoreceptor cells from the toxic accumulation of excess 11-cis-retinal. Proc Natl Acad Sci U S A 2014; 111:5024-9. [PMID: 24707049 DOI: 10.1073/pnas.1400780111] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The visual cycle is a series of enzyme-catalyzed reactions which converts all-trans-retinal to 11-cis-retinal for the regeneration of visual pigments in rod and cone photoreceptor cells. Although essential for vision, 11-cis-retinal like all-trans-retinal is highly toxic due to its highly reactive aldehyde group and has to be detoxified by either reduction to retinol or sequestration within retinal-binding proteins. Previous studies have focused on the role of the ATP-binding cassette transporter ABCA4 associated with Stargardt macular degeneration and retinol dehydrogenases (RDH) in the clearance of all-trans-retinal from photoreceptors following photoexcitation. How rod and cone cells prevent the accumulation of 11-cis-retinal in photoreceptor disk membranes in excess of what is required for visual pigment regeneration is not known. Here we show that ABCA4 can transport N-11-cis-retinylidene-phosphatidylethanolamine (PE), the Schiff-base conjugate of 11-cis-retinal and PE, from the lumen to the cytoplasmic leaflet of disk membranes. This transport function together with chemical isomerization to its all-trans isomer and reduction to all-trans-retinol by RDH can prevent the accumulation of excess 11-cis-retinal and its Schiff-base conjugate and the formation of toxic bisretinoid compounds as found in ABCA4-deficient mice and individuals with Stargardt macular degeneration. This segment of the visual cycle in which excess 11-cis-retinal is converted to all-trans-retinol provides a rationale for the unusually high content of PE and its long-chain unsaturated docosahexaenoyl group in photoreceptor membranes and adds insight into the molecular mechanisms responsible for Stargardt macular degeneration.
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Hishikawa D, Hashidate T, Shimizu T, Shindou H. Diversity and function of membrane glycerophospholipids generated by the remodeling pathway in mammalian cells. J Lipid Res 2014; 55:799-807. [PMID: 24646950 PMCID: PMC3995458 DOI: 10.1194/jlr.r046094] [Citation(s) in RCA: 230] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Cellular membranes are composed of numerous kinds of glycerophospholipids with different combinations of polar heads at the sn-3 position and acyl moieties at the sn-1 and sn-2 positions, respectively. The glycerophospholipid compositions of different cell types, organelles, and inner/outer plasma membrane leaflets are quite diverse. The acyl moieties of glycerophospholipids synthesized in the de novo pathway are subsequently remodeled by the action of phospholipases and lysophospholipid acyltransferases. This remodeling cycle contributes to the generation of membrane glycerophospholipid diversity and the production of lipid mediators such as fatty acid derivatives and lysophospholipids. Furthermore, specific glycerophospholipid transporters are also important to organize a unique glycerophospholipid composition in each organelle. Recent progress in this field contributes to understanding how and why membrane glycerophospholipid diversity is organized and maintained.
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Affiliation(s)
- Daisuke Hishikawa
- Department of Lipid Signaling, Research Institute, National Center for Global Health and Medicine, Tokyo 162-8655, Japan
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Effect of oxidation of polyunsaturated phospholipids on the binding of proteins in monolayers. Colloids Surf B Biointerfaces 2013; 109:109-14. [DOI: 10.1016/j.colsurfb.2013.03.021] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Revised: 03/08/2013] [Accepted: 03/12/2013] [Indexed: 11/18/2022]
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Khattree N, Ritter LM, Goldberg AFX. Membrane curvature generation by a C-terminal amphipathic helix in peripherin-2/rds, a tetraspanin required for photoreceptor sensory cilium morphogenesis. J Cell Sci 2013; 126:4659-70. [PMID: 23886945 DOI: 10.1242/jcs.126888] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Vertebrate vision requires photon absorption by photoreceptor outer segments (OSs), structurally elaborate membranous organelles derived from non-motile sensory cilia. The structure and function of OSs depends on a precise stacking of hundreds of membranous disks. Each disk is fully (as in rods) or partially (as in cones) bounded by a rim, at which the membrane is distorted into an energetically unfavorable high-curvature bend; however, the mechanism(s) underlying disk rim structure is (are) not established. Here, we demonstrate that the intrinsically disordered cytoplasmic C-terminus of the photoreceptor tetraspanin peripherin-2/rds (P/rds) can directly generate membrane curvature. A P/rds C-terminal domain and a peptide mimetic of an amphipathic helix contained within it each generated curvature in liposomes with a composition similar to that of OS disks and in liposomes generated from native OS lipids. Association of the C-terminal domain with liposomes required conical phospholipids, and was promoted by membrane curvature and anionic surface charge, results suggesting that the P/rds C-terminal amphipathic helix can partition into the cytosolic membrane leaflet to generate curvature by a hydrophobic insertion (wedging) mechanism. This activity was evidenced in full-length P/rds by its induction of small-diameter tubulovesicular membrane foci in cultured cells. In sum, the findings suggest that curvature generation by the P/rds C-terminus contributes to the distinctive structure of OS disk rims, and provide insight into how inherited defects in P/rds can disrupt organelle structure to cause retinal disease. They also raise the possibility that tethered amphipathic helices can function for shaping cellular membranes more generally.
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Affiliation(s)
- Nidhi Khattree
- Eye Research Institute, Oakland University, Rochester, MI 48309, USA
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Miwa K, Hashimoto M, Hossain S, Katakura M, Shido O. Evaluation of the inhibitory effect of docosahexaenoic acid and arachidonic acid on the initial stage of amyloid β1-42 polymerization by fluorescence correlation spectroscopy. ACTA ACUST UNITED AC 2013. [DOI: 10.4236/aad.2013.22009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Buzhynskyy N, Salesse C, Scheuring S. Rhodopsin is spatially heterogeneously distributed in rod outer segment disk membranes. J Mol Recognit 2011; 24:483-9. [DOI: 10.1002/jmr.1086] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Jastrzebska B, Debinski A, Filipek S, Palczewski K. Role of membrane integrity on G protein-coupled receptors: Rhodopsin stability and function. Prog Lipid Res 2011; 50:267-77. [PMID: 21435354 DOI: 10.1016/j.plipres.2011.03.002] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Rhodopsin is a prototypical G protein-coupled receptor (GPCR) - a member of the superfamily that shares a similar structural architecture consisting of seven-transmembrane helices and propagates various signals across biological membranes. Rhodopsin is embedded in the lipid bilayer of specialized disk membranes in the outer segments of retinal rod photoreceptor cells where it transmits a light-stimulated signal. Photoactivated rhodopsin then activates a visual signaling cascade through its cognate G protein, transducin or Gt, that results in a neuronal response in the brain. Interestingly, the lipid composition of ROS membranes not only differs from that of the photoreceptor plasma membrane but is critical for visual transduction. Specifically, lipids can modulate structural changes in rhodopsin that occur after photoactivation and influence binding of transducin. Thus, altering the lipid organization of ROS membranes can result in visual dysfunction and blindness.
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Affiliation(s)
- Beata Jastrzebska
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4965, USA.
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31
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Structure and dynamics of cholesterol-containing polyunsaturated lipid membranes studied by neutron diffraction and NMR. J Membr Biol 2010; 239:63-71. [PMID: 21161517 PMCID: PMC3030944 DOI: 10.1007/s00232-010-9326-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2010] [Accepted: 11/05/2010] [Indexed: 11/16/2022]
Abstract
A direct and quantitative analysis of the internal structure and dynamics of a polyunsaturated lipid bilayer composed of 1-stearoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine (18:0-22:6n3-PC) containing 29 mol% cholesterol was carried out by neutron diffraction, 2H-NMR and 13C-MAS NMR. Scattering length distribution functions of cholesterol segments as well as of the sn-1 and sn-2 hydrocarbon chains of 18:0-22:6n3-PC were obtained by conducting experiments with specifically deuterated cholesterol and lipids. Cholesterol orients parallel to the phospholipids, with the A-ring near the lipid glycerol and the terminal methyl groups 3 Å away from the bilayer center. Previously, we reported that the density of polyunsaturated docosahexaenoic acid (DHA, 22:6n3) chains was higher near the lipid–water interface. Addition of cholesterol partially redistributes DHA density from near the lipid–water interface to the center of the hydrocarbon region. Cholesterol raises chain-order parameters of both stearic acid and DHA chains. The fractional order increase for stearic acid methylene carbons C8–C18 is larger, reflecting the redistribution of DHA chain density toward the bilayer center. The correlation times of DHA chain isomerization are short and mostly unperturbed by the presence of cholesterol. The uneven distribution of saturated and polyunsaturated chain densities and the cholesterol-induced balancing of chain distributions may have important implications for the function and integrity of membrane receptors, such as rhodopsin.
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Polyunsaturated fatty acid–cholesterol interactions: Domain formation in membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:24-32. [DOI: 10.1016/j.bbamem.2008.10.011] [Citation(s) in RCA: 208] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2008] [Revised: 10/10/2008] [Accepted: 10/14/2008] [Indexed: 11/22/2022]
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Abstract
What distinguishes polyunsaturated fatty acids (PUFAs) from less unsaturated fatty acids is the presence of a repeating =CH-CH(2)-CH= unit that produces an extremely flexible structure rapidly isomerizing through conformational states. Docosahexaenoic acid (DHA) with 6 double bonds is the most extreme example. The focus of this review is the profound impact that the high disorder of DHA has on its interaction with cholesterol when the PUFA is incorporated into membrane phospholipids. Results from a battery of biophysical techniques are described. They demonstrate an aversion of DHA for the sterol that drives the lateral segregation of DHA-containing phospholipids into liquid disordered (l(d)) domains that are depleted in cholesterol. These domains are compositionally and organizationally the antithesis of lipid rafts, the much-studied liquid ordered (l(o)) domain that is enriched in predominantly saturated sphingolipids and cholesterol. We hypothesize that the introduction of DHA-rich domains into the plasma membrane where they coexist with lipid rafts is the origin, in part, of the astonishing diversity of health benefits that accrue from dietary consumption of DHA. According to our model, changes in the conformation of signaling proteins when they move between these disparate domains have the potential to modulate cell function.
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Boucher J, Trudel E, Méthot M, Desmeules P, Salesse C. Organization, structure and activity of proteins in monolayers. Colloids Surf B Biointerfaces 2007; 58:73-90. [PMID: 17509839 DOI: 10.1016/j.colsurfb.2007.03.019] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2007] [Revised: 03/24/2007] [Accepted: 03/26/2007] [Indexed: 12/17/2022]
Abstract
Many different processes take place at the cell membrane interface. Indeed, for instance, ligands bind membrane proteins which in turn activate peripheral membrane proteins, some of which are enzymes whose action is also located at the membrane interface. Native cell membranes are difficult to use to gain information on the activity of individual proteins at the membrane interface because of the large number of different proteins involved in membranous processes. Model membrane systems, such as monolayers at the air-water interface, have thus been extensively used during the last 50 years to reconstitute proteins and to gain information on their organization, structure and activity in membranes. In the present paper, we review the recent work we have performed with membrane and peripheral proteins as well as enzymes in monolayers at the air-water interface. We show that the structure and orientation of gramicidin has been determined by combining different methods. Furthermore, we demonstrate that the secondary structure of rhodopsin and bacteriorhodopsin is indistinguishable from that in native membranes when appropriate conditions are used. We also show that the kinetics and extent of monolayer binding of myristoylated recoverin is much faster than that of the nonmyristoylated form and that this binding is highly favored by the presence polyunsaturated phospholipids. Moreover, we show that the use of fragments of RPE65 allow determine which region of this protein is most likely involved in membrane binding. Monomolecular films were also used to further understand the hydrolysis of organized phospholipids by phospholipases A2 and C.
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Affiliation(s)
- Julie Boucher
- Unité de recherche en ophtalmologie, Centre de Recherche du Centre Hospitalier Universitaire de Québec and Département d'Ophtalmologie, Faculté de médecine, Université Laval, Québec, Que. G1V 4G2, Canada
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Wisniewska A, Subczynski WK. Distribution of macular xanthophylls between domains in a model of photoreceptor outer segment membranes. Free Radic Biol Med 2006; 41:1257-65. [PMID: 17015172 DOI: 10.1016/j.freeradbiomed.2006.07.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2006] [Revised: 07/03/2006] [Accepted: 07/06/2006] [Indexed: 11/24/2022]
Abstract
A model of photoreceptor outer segment (POS) membranes has been proposed, consisting of an equimolar ternary mixture of 1-palmitoyl-2-docosahexaenoylphosphatidylcholine/distearoylphosphatidylcholine/cholesterol. It was shown that, as in membranes made from the raft-forming mixture, in the model of POS membranes, two domains are formed: the raft domain (detergent resistant membranes, DRM), and the bulk domain (detergent soluble membranes, DSM). Saturation-recovery EPR discrimination by oxygen transport method also demonstrated the presence of two domains in this model system in situ at a wide range of temperatures (10-55 degrees C), showing additionally that neither lutein nor zeaxanthin at 1 mol% affect the formation of these domains. These membrane domains have been separated using cold Triton X-100 extraction from a model of POS membranes containing 1 mol% of either lutein or zeaxanthin. The results indicated that the macular xanthophylls lutein and zeaxanthin are substantially excluded from DRM and remain concentrated in DSM, a domain enriched in highly unsaturated docosahexaenoyl acid which is abundant in retina membranes. The concentration of xanthophylls in DRM and DSM calculated as the mol ratio of either xanthophyll to total lipid (phospholipid+cholesterol) was 0.0028 and 0.0391, respectively. Thus, xanthophylls are about 14 times more concentrated in DSM than in DRM. No significant difference in the distribution of lutein and zeaxanthin was found. The obtained results suggest that in POS membranes macular xanthophylls should also be concentrated in domains enriched in polyunsaturated chains.
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Affiliation(s)
- Anna Wisniewska
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
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Soubias O, Teague WE, Gawrisch K. Evidence for specificity in lipid-rhodopsin interactions. J Biol Chem 2006; 281:33233-41. [PMID: 16959786 DOI: 10.1074/jbc.m603059200] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The interaction of bovine rhodopsin with poly- and monounsaturated lipids was studied by (1)H MAS NMR with magnetization transfer from rhodopsin to lipid. Experiments were conducted on bovine rod outer segment (ROS) disks and on recombinant membranes containing lipids with polyunsaturated, docosahexaenoyl (DHA) chains. Poly- and monounsaturated lipids interact specifically with different sites on the rhodopsin surface. Rates of magnetization transfer from protein to DHA are lipid headgroup-dependent and increased in the sequence PC < PS < PE. Boundary lipids are in fast exchange with the lipid matrix on a time scale of milliseconds or shorter. All rhodopsin photointermediates transferred magnetization preferentially to DHA-containing lipids, but highest rates were observed for Meta-III rhodopsin. The experiments show clearly that the surface of rhodopsin has sites for specific interaction with lipids. Current theories of lipid-protein interaction do not account for such surface heterogeneity.
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Affiliation(s)
- Olivier Soubias
- Laboratory of Membrane Biochemistry and Biophysics, NIAAA, National Institutes of Health, Bethesda, Maryland 20892, USA
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Suh M, Clandinin MT. 20:5n-3 but not 22:6n-3 is a preferred substrate for synthesis of n-3 very-long- chain fatty acids (C24-C36) in retina. Curr Eye Res 2006; 30:959-68. [PMID: 16282130 DOI: 10.1080/02713680500246957] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The objective of this study was to determine if 20:5n-3 or 22:6n-3 is the primary precursor of very-long-chain fatty acids (VLCFAs; C24-C36) synthesized in retina. Rats were fed semisynthetic, nutritionally complete diet containing 20% (w/w) fat with 3% (w/w) of 22:6n-3. After 6 weeks feeding, the vitreal fluid of each eye was injected with [3H]20:5n-3 or [3H]22:6n-3. Rats were then maintained under constant light (330 lux) or dark conditions for 48 hr. After 48 hr in vivo metabolism, the amount of label present in individual fatty acids was determined in major phospholipids in retina. For [3H]22:6n-3, 90% of total incorporation remained in 22:6n-3, whereas for [3H]20:5n-3 the label was actively incorporated into pentaenoic and hexaenoic VLCFAs up to 34 carbon chain length. 22:5n-3 derived from [3H]20:5n-3 was among the most highly labeled fatty acids. These observations suggest that 22:6n-3 is incorporated directly into retinal phospholipids without further metabolism, whereas 20:5n-3 and 22:5n-3 are metabolically active precursors for synthesis of VLCFAs.
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Affiliation(s)
- Miyoung Suh
- Department of Human Nutritional Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
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Wassall SR, Brzustowicz MR, Shaikh SR, Cherezov V, Caffrey M, Stillwell W. Order from disorder, corralling cholesterol with chaotic lipids. The role of polyunsaturated lipids in membrane raft formation. Chem Phys Lipids 2005; 132:79-88. [PMID: 15530450 DOI: 10.1016/j.chemphyslip.2004.09.007] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A myriad of health benefits including the prevention of cancer and heart disease accompanies consumption of polyunsaturated fatty acids (PUFA). Of special importance is the omega-3-PUFA docosahexaenoic acid (DHA), with 22 carbons and six double bonds that constitute the most highly unsaturated fatty acid naturally occurring. Our experiments target the membrane as a likely site of action and focus upon the interaction of cholesterol with PUFA-containing phospholipids. They support the idea that steric incompatibility of the rigid steroid moiety for highly disordered PUFA chains promotes lateral segregation of lipids into PUFA-rich/sterol-poor and PUFA-poor/sterol-rich regions. Solid state 2H NMR and X-ray diffraction demonstrate that the solubility of cholesterol is low in polyunsaturated bilayers. In mixed membranes of phosphatidylethanolamine (PE) with the lipid raft-forming molecules sphingomyelin (SM) and cholesterol, diminished affinity of the sterol for 1-[2H31]palmitoyl-2-docosahexaenoylphosphatidylethanolamine ([2H31]16:0-22:6PE) relative to 1-[2H31]palmitoyl-2-oleoylphosphatidylethanolamine ([2H31]16:0-18:1PE) is identified by 2H NMR order parameters. Here, lies the origin of a potential biological advantage of the relatively modest increase in PUFA content of plasma membranes that would be conferred by dietary supplementation. We hypothesize that the enhanced propensity to form SM-/cholesterol-rich rafts as well as PUFA-rich/cholesterol-poor microdomains would modify the function of proteins for which these respective regions provide a platform.
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Affiliation(s)
- Stephen R Wassall
- Department of Physics, Indiana University Purdue University Indianapolis, 402 N. Blackford Street, Indianapolis, IN 46202-3273, USA.
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Valentine RC, Valentine DL. Omega-3 fatty acids in cellular membranes: a unified concept. Prog Lipid Res 2005; 43:383-402. [PMID: 15458813 DOI: 10.1016/j.plipres.2004.05.004] [Citation(s) in RCA: 150] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/27/2004] [Indexed: 11/23/2022]
Abstract
The Omega-3 fatty acid DHA (docosahexaenoic acid, 22:6) and its sister molecule EPA (eicosapentaenoic acid, 20:5) are highlighted here. These highly unsaturated fatty acids are widespread in nature, especially in the marine environment, and are essential in membranes ranging from deep sea bacteria to human neurons. Studies of DHA/EPA in bacteria have led to a working model on the structural roles of these molecules and are described in this review. The main points are: (a) genomic analysis shows that genes encoding the DHA/EPA pathways are similar, supporting the idea that structural roles in bacteria might be similar, (b) biochemical analysis shows that DHA and EPA are produced in bacteria by a polyketide process distinct from the pathway of plants and animals; this allows DHA and EPA to be produced in anaerobic or oxygen-limited environments, (c) regulatory systems triggered by temperature and pressure have been identified and studied, and add to the understanding of the roles of these molecules, (d) DHA/EPA bacteria are located almost exclusively in the marine environment, raising the prospect of an important linkage between membrane processes and marine conditions, (e) physiological studies of an EPA recombinant of E. coli show that EPA phospholipids contribute essential fluidity to the bilayer and that an EPA-enriched membrane supports a respiratory lifestyle dependent on proton bioenergetics; the EPA recombinant displays other physiological properties likely attributed to high levels of EPA in the bilayer, and (f) chemical studies such as chemical dynamic modeling support the idea that DHA and presumably EPA contribute hyperfluidizing properties to the membrane. We hypothesize that DHA/EPA phospholipids contribute fluidity and other properties to the bilayer which distinguish these highly unsaturated chains from monounsaturates and polyunsaturates such as 18:2 and 18:3. We further hypothesize that the structural properties of DHA/EPA functioning in bacteria are also harnessed by higher organisms for enhancing crucial membrane processes including photosynthesis and energy transduction.
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Brockman HL, Applegate KR, Momsen MM, King WC, Glomset JA. Packing and electrostatic behavior of sn-2-docosahexaenoyl and -arachidonoyl phosphoglycerides. Biophys J 2004; 85:2384-96. [PMID: 14507702 PMCID: PMC1303463 DOI: 10.1016/s0006-3495(03)74662-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Mammalian synaptic membranes appear to contain high proportions of specific, sn-1-stearoyl-2-docosahexaenoyl- and sn-1-stearoyl-2-arachidonoyl phosphoglycerides, but the structural significance of this is unclear. Here we used a standardized approach to compare the properties of homogeneous monolayers of the corresponding phosphatidylcholines, phosphatidylethanolamines, phosphatidylserines, and phosphatidic acids with those of control monolayers of sn-1-stearoyl-2-oleoyl- and sn-1-palmitoyl-2-oleoyl phosphoglycerides. Major findings were: 1), that the presence of an sn-2-docosahexaenoyl group or an sn-2-arachidonoyl group increases the molecular areas of phosphoglycerides by 3.8 A(2) (7%) relative to the presence of an sn-2-oleoyl group; 2), that the phosphorylcholine headgroup independently increases molecular areas by a larger amount, 7.1 A(2) (13%); and 3), that the dipole moments of species having an arachidonoyl moiety or an oleoyl moiety are 83 mD (19%) higher than those of comparable docosahexaenoic acid-containing phosphoglycerides. These and other results provide new information about the molecular packing properties of polyenoic phosphoglycerides and raise important questions about the role of these phosphoglycerides in synapses.
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Affiliation(s)
- Howard L Brockman
- The Hormel Institute, University of Minnesota, Austin, Minnesota 55912, USA
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Abstract
Docosahexaenoic acid (DHA) with 22-carbons and 6 double bonds is the extreme example of an omega-3 polyunsaturated fatty acid (PUFA). DHA has strong medical implications since its dietary presence has been positively linked to the prevention of numerous human afflictions including cancer and heart disease. The PUFA, moreover, is essential to neurological function. It is remarkable that one simple molecule has been reported to affect so many seemingly unrelated biological processes. Although details of a molecular mode of action remain elusive, DHA must be acting at a fundamental level common to many tissues that is related to the high degree of conformational flexibility that the multiple double bonds have been identified to confer. One likely target for DHA action is at the cell membrane where the fatty acid is known to readily incorporate into membrane phospholipids. Once esterified into phospholipids DHA has been demonstrated to significantly alter many basic properties of membranes including acyl chain order and "fluidity", phase behavior, elastic compressibility, permeability, fusion, flip-flop and protein activity. It is concluded that DHA's interaction with other membrane lipids, particularly cholesterol, may play a prominent role in modulating the local structure and function of cell membranes.
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Affiliation(s)
- William Stillwell
- Department of Biology, Indiana University Purdue University Indianapolis, 723 W Michigan Street, Indianapolis, IN 46202-5132, USA.
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Antollini SS, Aveldaño MI. Thermal behavior of liposomes containing PCs with long and very long chain PUFAs isolated from retinal rod outer segment membranes. J Lipid Res 2002; 43:1440-9. [PMID: 12235175 DOI: 10.1194/jlr.m200057-jlr200] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
About one-fourth the phosphatidylcholines (PC) from retina photoreceptor rod outer segment (ROS) membranes contain docosahexaenoic acid (22:6n-3) at sn-2 and a very long chain polyunsaturated fatty acid (VLCPUFA) (C24 to C36) at the sn-1 position of the glycerol backbone. In order to study the thermotropic behavior of these PCs, subfractions and molecular species of PC (16:0/22:6, 18:0/22:6, 22:6/22:6, 32:5/22:6, 32:6/22:6, 34:5/22:6), were isolated from bovine ROS, and liposomes containing different proportions of these PCs and dimyristoyl-PC (DMPC) or dipalmitoyl PC (DPPC) were compared using the fluorescence probes Laurdan and 1,6-diphenyl-1,3,5-hexatriene (DPH). With both probes, the 22:6n-3 containing PCs from ROS, in all proportions tested, decreased the transition temperature (Tt) of both DMPC and DPPC. Below the transition temperature, coexistence of phases was evidenced in all cases. Liposomes formed with 100% of any of these PCs did not show phase transitions in the temperature range studied (8 degrees C to 50 degrees C). At physiological temperatures, as it is likely to be the case in ROS membranes, all of these PC species were in the liquid-crystalline state. With Laurdan, all dipolyunsaturated PCs seemed to behave similarly: despite the large number of double bonds per molecule, all of them decreased the Tt of DPPC less than did the hexaenoic PCs. With DPH, an ample difference was detected between the dipolyunsaturates, 22:6/22:6-PC and VLCPUFA/22:6-PCs, and between the latter and hexaenoic PCs throughout the temperature range studied. This difference is consistent with the interpretation that the largest "disorder" produced by PCs containing a VLCPUFA like 32:6n-3 at the sn-1 position occurs toward the center of the membrane.
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Affiliation(s)
- Silvia S Antollini
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas, Bahía Blanca, Argentina.
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Polozova A, Litman BJ. Cholesterol dependent recruitment of di22:6-PC by a G protein-coupled receptor into lateral domains. Biophys J 2000; 79:2632-43. [PMID: 11053136 PMCID: PMC1301144 DOI: 10.1016/s0006-3495(00)76502-7] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Bovine rhodopsin was reconstituted into mixtures of didocosahexaenoylphosphatidylcholine (di22:6-PC), dipalmitoylphosphatidylcholine (di16:0-PC), sn-1-palmitoyl-sn-2-docosahexaenoylphosphatidylcholine (16:0, 22:6-PC) and cholesterol. Rhodopsin denaturation was examined by using high-sensitivity differential scanning calorimetry. The unfolding temperature was increased at lower levels of lipid unsaturation, but the highest temperature was detected for native disk membranes: di22:6-PC < 16:0,22:6-PC < di16:0,18:1-PC < native disks. The incorporation of 30 mol% of cholesterol resulted in 2-4 degrees C increase of denaturation temperature in all reconstituted systems examined. From the analysis of van't Hoff's and calorimetric enthalpies, it was concluded that the presence of cholesterol in di22:6-PC-containing bilayers induces a level of cooperativity in rhodopsin unfolding. Fluorescence resonance energy transfer (FRET), using lipids labeled at the headgroup with pyrene (Py) as donors and rhodopsin retinal group as acceptor of fluorescence, was used to study rhodopsin association with lipids. Higher FRET efficiencies detected for di22:6-PE-Py, compared to di16:0-PE-Py, in mixed di22:6-PC-di16:0-PC-cholesterol bilayers, indicate preferential segregation of rhodopsin with polyunsaturated lipids. The effective range of the rhodopsin-lipid interactions facilitating cluster formation exceeds two adjacent lipid layers. In similar mixed bilayers containing no cholesterol, cluster formation was absent at temperatures above lipid phase transition, indicating a crucial role of cholesterol in microdomain formation.
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Affiliation(s)
- A Polozova
- Laboratory of Membrane Biochemistry and Biophysics, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, Maryland 20852, USA
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Ahn J, Wong JT, Molday RS. The effect of lipid environment and retinoids on the ATPase activity of ABCR, the photoreceptor ABC transporter responsible for Stargardt macular dystrophy. J Biol Chem 2000; 275:20399-405. [PMID: 10767284 DOI: 10.1074/jbc.m000555200] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ABCR is a photoreceptor-specific ATP-binding cassette transporter that has been linked to various retinal diseases, including Stargardt macular dystrophy, and implicated in retinal transport across rod outer segment (ROS) membranes. We have examined the ATPase and GTPase activity of detergent-solubilized and reconstituted ABCR. 3-[(3-Cholamidopropyl)dimethylammonio]-1-propanesulfonic acid-solubilized ABCR had ATPase and GTPase activity (K(m) approximately 75 micrometer V(max) approximately 200 nmol/min/mg) that was stimulated 1.5-2-fold by all-trans-retinal and dependent on phospholipid and dithiothreitol. The K(m) for ATP decreased to approximately 25 micrometer after reconstitution, whereas the V(max) was strongly dependent on the lipid used for reconstitution. ABCR reconstituted in ROS phospholipid had a V(max) for basal and retinal activated ATPase activity that was 4-6 times higher than for ABCR in soybean or brain phospholipid. This enhanced activity was mainly due to the high phosphatidylethanolamine (PE) content of ROS membranes. PE was also required for retinoid-stimulated ATPase activity. ATPase activity of ABCR was stimulated by the addition of N-retinylidene-PE but not the reduced derivative, retinyl-PE. ABCR expressed in COS-1 cells also exhibited retinal-stimulated ATPase activity similar to that of the native protein. These results support the view that ABCR is an active retinoid transporter, the nucleotidase activity of which is strongly influenced by its lipid environment.
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Affiliation(s)
- J Ahn
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
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Giusto NM, Pasquaré SJ, Salvador GA, Castagnet PI, Roque ME, Ilincheta de Boschero MG. Lipid metabolism in vertebrate retinal rod outer segments. Prog Lipid Res 2000; 39:315-91. [PMID: 10856601 DOI: 10.1016/s0163-7827(00)00009-6] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Affiliation(s)
- N M Giusto
- Instituto de Investigaciones Bioquímicas, Universidad Nacional del Sur and Consejo Nacional de Investigaciones Científicas y Técnicas, CC 857, B 8000 FWB, Bahia Blanca, Argentina.
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Connor SL, Zhu N, Anderson GJ, Hamill D, Jaffe E, Carlson J, Connor WE. Cheek cell phospholipids in human infants: a marker of docosahexaenoic and arachidonic acids in the diet, plasma, and red blood cells. Am J Clin Nutr 2000; 71:21-7. [PMID: 10617942 DOI: 10.1093/ajcn/71.1.21] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
BACKGROUND Assessment of essential fatty acid status requires collection of blood or adipose tissue samples. However, these invasive techniques cannot always be used in studies involving infants, young children, or subjects from whom it is difficult to obtain blood. A body tissue that is easy to access is the buccal mucosa (cheek cells). OBJECTIVE The objective was to investigate the degree to which fatty acids of cheek cells reflect the fatty acid content of plasma, red blood cells, and the diet. DESIGN Thirty-one infants aged 12 mo were enrolled. Five infants were fed human milk and 26 infants received formulas that provided a wide range of arachidonic acid and docosahexaenoic acid (DHA) intakes. Cheek cells were collected on a small piece of gauze by gently swabbing the inside of the cheek 3 times. Lipids were extracted from the gauze and the phospholipid fatty acid content of the cheek cells was determined. RESULTS Cheek cell DHA and arachidonic acid in phospholipids were significantly correlated with DHA and arachidonic acid in plasma [r = 0.61 (P < 0.001) and r = 0.37 (P <0.05), respectively], red blood cells [r = 0.58 (P < 0.001) and r = 0.37 (P < 0.05), respectively], and the diet [r = 0.65 (P < 0.001) and r = 0. 51 (P < 0.01), respectively]. CONCLUSIONS Given these correlations and the ease and noninvasive nature of this technique, cheek cell fatty acids may serve as a marker of the essential fatty acid content, especially of DHA and arachidonic acid, in plasma, red blood cells, and the diet.
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Affiliation(s)
- S L Connor
- Departments of Medicine and Pediatrics, Oregon Health Sciences University, Portland, OR 97201-3098, USA.
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Mitchell DC, Litman BJ. Molecular order and dynamics in bilayers consisting of highly polyunsaturated phospholipids. Biophys J 1998; 74:879-91. [PMID: 9533699 PMCID: PMC1302567 DOI: 10.1016/s0006-3495(98)74011-1] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The time-resolved fluorescence emission and decay of fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene (DPH) was used to characterize equilibrium and dynamic bilayer structural properties of symmetrically substituted phosphatidylcholines (PCs) with acyl chains containing no, one, four, or six double bonds and mixed-chain phosphatidylcholines with a saturated sn-1 chain and one, four, or six double bonds in the sn-2 chain. Both the Brownian rotational diffusion (BRD) model and the wobble-in-cone model were fit to all differential polarization data, and the descriptions of the data provided by the BRD model were found to be statistically superior. Global analysis of differential polarization data revealed two statistically equivalent solutions. The solution corresponding to a bimodal orientational distribution function, f(theta), was selected based on the effects of temperature on f(theta) and previous measurements on fixed, oriented bilayers. The overall equilibrium acyl chain order in these bilayers was analyzed by comparing the orientational probability distribution for DPH, f(theta) sin theta, with a random orientational distribution. Orientational order decreased and probe dynamics increased in mixed-chain species as the unsaturation of the sn-2 chain was increased. The degree of orientational order dropped dramatically in the dipolyunsaturated species compared with the mixed-chain phosphatidylcholines, which contained a polyunsaturated sn-2 chain. In terms of both orientational order and probe dynamics, the differences between the highly polyunsaturated species and the monounsaturated species were much greater than the differences between the monounsaturated species and a disaturated PC.
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Affiliation(s)
- D C Mitchell
- Section of Fluorescence Studies, Laboratory of Membrane Biophysics and Biochemistry, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, Maryland 20852, USA.
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Albert AD, Young JE, Paw Z. Phospholipid fatty acyl spatial distribution in bovine rod outer segment disk membranes. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1368:52-60. [PMID: 9459584 DOI: 10.1016/s0005-2736(97)00200-9] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The distribution of fatty acids within the phospholipid headgroup classes was investigated as a function of the age/spatial distribution of bovine rod outer segment disk membranes. The disks were separated into subpopulations based upon the cholesterol content in their membranes. Because disk membrane cholesterol content decreases as the disks are apically displaced in the rod outer segment, this separation yields disk subpopulations of different ages and from age-dependent spatial locations within the outer segment. The phospholipids, phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS) and phosphatidylinositol (PI), of each of these subpopulations were separated and the fatty acid composition of each was determined. These data indicated that while most of the fatty acids show little or no change with age/spatial location, some pronounced changes can be observed in certain classes. Within the PC class, 16:0 dramatically decreases with disk age while the 22:6 increases with disk age. While the PE class exhibits some fatty acid changes, they are small. The PS class exhibits no significant changes in fatty acid composition. The PI class which constitutes less than 2% of the total phospholipid exhibits age-related changes in each of the fatty acids which could be measured. Most notable of these is an increase in 20:4 as the disks are apically displaced. These changes indicate a remodeling of the disk membranes which may be related to the phototransduction process or to preparation for eventual disk phagocytosis.
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Affiliation(s)
- A D Albert
- Department of Biochemistry, School of Medicine, University at Buffalo (SUNY), NY 14214, USA
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Connor WE, Lin DS, Thomas G, Ey F, DeLoughery T, Zhu N. Abnormal phospholipid molecular species of erythrocytes in sickle cell anemia. J Lipid Res 1997. [DOI: 10.1016/s0022-2275(20)30036-5] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
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50
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Koenig BW, Strey HH, Gawrisch K. Membrane lateral compressibility determined by NMR and x-ray diffraction: effect of acyl chain polyunsaturation. Biophys J 1997; 73:1954-66. [PMID: 9336191 PMCID: PMC1181096 DOI: 10.1016/s0006-3495(97)78226-2] [Citation(s) in RCA: 218] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The elastic area compressibility modulus, Ka, of lamellar liquid crystalline bilayers was determined by a new experimental approach using 2H-NMR order parameters of lipid hydrocarbon chains together with lamellar repeat spacings measured by x-ray diffraction. The combination of NMR and x-ray techniques yields accurate determination of lateral area per lipid molecule. Samples of saturated, monounsaturated, and polyunsaturated phospholipids were equilibrated with polyethylene glycol (PEG) 20,000 solutions in water at concentrations from 0 to 55 wt % PEG at 30 degrees C. This procedure is equivalent to applying 0 to 8 dyn/cm lateral pressure to the bilayers. The resulting reductions in area per lipid were measured with a resolution of +/-0.2 A2 and the fractional area decrease was proportional to applied lateral pressure. For 1,2-dimyristoyl(d54)-sn-glycero-3-phosphocholine, 1-stearoyl(d35)-2-oleoyl-sn-glycero-3-phosphocholine (SOPC-d35), and 1-stearoyl(d35)-2-docosahexaenoyl-sn-glycero-3-phosphocholine (SDPC-d35) cross-sectional areas per molecule in excess water of 59.5, 61.4, and 69.2 A2 and bilayer elastic area compressibility moduli of 141, 221, and 121 dyn/cm were determined, respectively. Combining NMR and x-ray results enables the determination of compressibility differences between saturated and unsaturated hydrocarbon chains. In mixed-chain SOPC-d35 both chains have similar compressibility moduli; however, in mixed-chain polyunsaturated SDPC-d35, the saturated stearic acid chain appears to be far less compressible than the polyunsaturated docosahexaenoic acid chain.
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Affiliation(s)
- B W Koenig
- Laboratory of Membrane Biochemistry and Biophysics, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, Maryland 20852, USA
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