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Skinkle AD, Levental KR, Levental I. Cell-Derived Plasma Membrane Vesicles Are Permeable to Hydrophilic Macromolecules. Biophys J 2020; 118:1292-1300. [PMID: 32053777 DOI: 10.1016/j.bpj.2019.12.040] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Revised: 12/09/2019] [Accepted: 12/23/2019] [Indexed: 12/22/2022] Open
Abstract
Giant plasma membrane vesicles (GPMVs) are a widely used experimental platform for biochemical and biophysical analysis of isolated mammalian plasma membranes (PMs). A core advantage of these vesicles is that they maintain the native lipid and protein diversity of the PM while affording the experimental flexibility of synthetic giant vesicles. In addition to fundamental investigations of PM structure and composition, GPMVs have been used to evaluate the binding of proteins and small molecules to cell-derived membranes and the permeation of drug-like molecules through them. An important assumption of such experiments is that GPMVs are sealed, i.e., that permeation occurs by diffusion through the hydrophobic core rather than through hydrophilic pores. Here, we demonstrate that this assumption is often incorrect. We find that most GPMVs isolated using standard preparations are passively permeable to various hydrophilic solutes as large as 40 kDa, in contrast to synthetic giant unilamellar vesicles. We attribute this leakiness to stable, relatively large, and heterogeneous pores formed by rupture of vesicles from cells. Finally, we identify preparation conditions that minimize poration and allow evaluation of sealed GPMVs. These unexpected observations of GPMV poration are important for interpreting experiments utilizing GPMVs as PM models, particularly for drug permeation and membrane asymmetry.
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Affiliation(s)
- Allison D Skinkle
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas; Biological and Biomedical Sciences Program, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Kandice R Levental
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas
| | - Ilya Levental
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas.
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Cornell CE, Skinkle AD, He S, Levental I, Levental KR, Keller SL. Tuning Length Scales of Small Domains in Cell-Derived Membranes and Synthetic Model Membranes. Biophys J 2018; 115:690-701. [PMID: 30049406 DOI: 10.1016/j.bpj.2018.06.027] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 06/15/2018] [Accepted: 06/19/2018] [Indexed: 01/10/2023] Open
Abstract
Micron-scale, coexisting liquid-ordered (Lo) and liquid-disordered (Ld) phases are straightforward to observe in giant unilamellar vesicles (GUVs) composed of ternary lipid mixtures. Experimentally, uniform membranes undergo demixing when temperature is decreased: domains subsequently nucleate, diffuse, collide, and coalesce until only one domain of each phase remains. The sizes of these two domains are limited only by the size of the system. Under different conditions, vesicles exhibit smaller-scale domains of fixed sizes, leading to the question of what sets the length scale. In membranes with excess area, small domains are expected when coarsening is hindered or when a microemulsion or modulated phase arises. Here, we test predictions of how the size, morphology, and fluorescence levels of small domains vary with the membrane's temperature, tension, and composition. Using GUVs and cell-derived giant plasma membrane vesicles, we find that 1) the characteristic size of domains decreases when temperature is increased or membrane tension is decreased, 2) stripes are favored over circular domains for lipid compositions with low energy per unit interface, 3) fluorescence levels are consistent with domain registration across both monolayer leaflets of the bilayer, and 4) small domains form in GUVs composed of lipids both with and without ester-linked lipids. Our experimental results are consistent with several elements of current theories for microemulsions and modulated phases and inconsistent with others, suggesting a motivation to modify or enhance current theories.
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Affiliation(s)
- Caitlin E Cornell
- Department of Chemistry, University of Washington, Seattle, Washington
| | | | - Shushan He
- Department of Chemistry, University of Washington, Seattle, Washington
| | - Ilya Levental
- Department of Integrative Biology and Pharmacology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas
| | - Kandice R Levental
- Department of Integrative Biology and Pharmacology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas
| | - Sarah L Keller
- Department of Chemistry, University of Washington, Seattle, Washington.
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Cornell CE, Skinkle AD, Levental I, Levental KR, Keller SL. Manipulation of Length Scales in a Modulated Phase in Cell-Derived GPMVs and Synthetic Model GUVs. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.2490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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Levental KR, Surma MA, Skinkle AD, Lorent JH, Zhou Y, Klose C, Chang JT, Hancock JF, Levental I. ω-3 polyunsaturated fatty acids direct differentiation of the membrane phenotype in mesenchymal stem cells to potentiate osteogenesis. Sci Adv 2017; 3:eaao1193. [PMID: 29134198 PMCID: PMC5677358 DOI: 10.1126/sciadv.aao1193] [Citation(s) in RCA: 82] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 10/16/2017] [Indexed: 05/19/2023]
Abstract
Mammalian cells produce hundreds of dynamically regulated lipid species that are actively turned over and trafficked to produce functional membranes. These lipid repertoires are susceptible to perturbations from dietary sources, with potentially profound physiological consequences. However, neither the lipid repertoires of various cellular membranes, their modulation by dietary fats, nor their effects on cellular phenotypes have been widely explored. We report that differentiation of human mesenchymal stem cells (MSCs) into osteoblasts or adipocytes results in extensive remodeling of the plasma membrane (PM), producing cell-specific membrane compositions and biophysical properties. The distinct features of osteoblast PMs enabled rational engineering of membrane phenotypes to modulate differentiation in MSCs. Specifically, supplementation with docosahexaenoic acid (DHA), a lipid component characteristic of osteoblast membranes, induced broad lipidomic remodeling in MSCs that reproduced compositional and structural aspects of the osteoblastic PM phenotype. The PM changes induced by DHA supplementation potentiated osteogenic differentiation of MSCs concurrent with enhanced Akt activation at the PM. These observations prompt a model wherein the DHA-induced lipidome leads to more stable membrane microdomains, which serve to increase Akt activity and thereby enhance osteogenic differentiation. More broadly, our investigations suggest a general mechanism by which dietary fats affect cellular physiology through remodeling of membrane lipidomes, biophysical properties, and signaling.
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Affiliation(s)
- Kandice R. Levental
- McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX 77030, USA
| | | | | | - Joseph H. Lorent
- McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX 77030, USA
| | - Yong Zhou
- McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX 77030, USA
| | | | - Jeffrey T. Chang
- McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX 77030, USA
- School of Biomedical Informatics, University of Texas Health Science Center at Houston, Houston, TX 77030, USA
- Brown Foundation Institute of Molecular Medicine, University of Texas Health Science Center at Houston, Houston, TX 77030, USA
- Department of Bioinformatics and Computational Biology, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - John F. Hancock
- McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX 77030, USA
- Brown Foundation Institute of Molecular Medicine, University of Texas Health Science Center at Houston, Houston, TX 77030, USA
| | - Ilya Levental
- McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX 77030, USA
- Corresponding author.
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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