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Müller GA, Müller TD. (Patho)Physiology of Glycosylphosphatidylinositol-Anchored Proteins II: Intercellular Transfer of Matter (Inheritance?) That Matters. Biomolecules 2023; 13:994. [PMID: 37371574 DOI: 10.3390/biom13060994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Revised: 06/12/2023] [Accepted: 06/13/2023] [Indexed: 06/29/2023] Open
Abstract
Glycosylphosphatidylinositol (GPI)-anchored proteins (APs) are anchored at the outer leaflet of the plasma membrane (PM) bilayer by covalent linkage to a typical glycolipid and expressed in all eukaryotic organisms so far studied. Lipolytic release from PMs into extracellular compartments and intercellular transfer are regarded as the main (patho)physiological roles exerted by GPI-APs. The intercellular transfer of GPI-APs relies on the complete GPI anchor and is mediated by extracellular vesicles such as microvesicles and exosomes and lipid-free homo- or heteromeric aggregates, and lipoprotein-like particles such as prostasomes and surfactant-like particles, or lipid-containing micelle-like complexes. In mammalian organisms, non-vesicular transfer is controlled by the distance between donor and acceptor cells/tissues; intrinsic conditions such as age, metabolic state, and stress; extrinsic factors such as GPI-binding proteins; hormones such as insulin; and drugs such as anti-diabetic sulfonylureas. It proceeds either "directly" upon close neighborhood or contact of donor and acceptor cells or "indirectly" as a consequence of the induced lipolytic release of GPI-APs from PMs. Those displace from the serum GPI-binding proteins GPI-APs, which have retained the complete anchor, and become assembled in aggregates or micelle-like complexes. Importantly, intercellular transfer of GPI-APs has been shown to induce specific phenotypes such as stimulation of lipid and glycogen synthesis, in cultured human adipocytes, blood cells, and induced pluripotent stem cells. As a consequence, intercellular transfer of GPI-APs should be regarded as non-genetic inheritance of (acquired) features between somatic cells which is based on the biogenesis and transmission of matter such as GPI-APs and "membrane landscapes", rather than the replication and transmission of information such as DNA. Its operation in mammalian organisms remains to be clarified.
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Affiliation(s)
- Günter A Müller
- Institute for Diabetes and Obesity (IDO), Helmholtz Diabetes Center (HDC) and German Center for Diabetes Research (DZD) at the Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Ingolstädter Landstraße 1, 85764 Neuherberg, Germany
| | - Timo D Müller
- Institute for Diabetes and Obesity (IDO), Helmholtz Diabetes Center (HDC) and German Center for Diabetes Research (DZD) at the Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Ingolstädter Landstraße 1, 85764 Neuherberg, Germany
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2
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Mahmood A, Otruba Z, Weisgerber AW, Palay MD, Nguyen MT, Bills BL, Knowles MK. Exosome secretion kinetics are controlled by temperature. Biophys J 2023; 122:1301-1314. [PMID: 36814381 PMCID: PMC10111348 DOI: 10.1016/j.bpj.2023.02.025] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 01/12/2023] [Accepted: 02/17/2023] [Indexed: 02/24/2023] Open
Abstract
When multivesicular endosomes (MVEs) fuse with the plasma membrane, exosomes are released into the extracellular space where they can affect other cells. The ability of exosomes to regulate cells nearby or further away depends on whether they remain attached to the secreting cell membrane. The regulation and kinetics of exosome secretion are not well characterized, but probes for directly imaging single MVE fusion events have allowed for visualization of the fusion and release process. In particular, the design of an exosome marker with a pH-sensitive dye in the middle of the tetraspanin protein CD63 has facilitated studies of individual MVE fusion events. Using TIRF microscopy, single fusion events were measured in A549 cells held at 23-37°C and events were identified using an automated detection algorithm. Stable docking precedes fusion almost always and a decrease in temperature was accompanied by decrease in the rate of content loss and in the frequency of fusion events. The loss of CD63-pHluorin fluorescence was measured at fusion sites and fit with a single or double exponential decay, with most events requiring two components and a plateau because the loss of fluorescence was typically incomplete. To interpret the kinetics, fusion events were simulated as a localized release of tethered/untethered exosomes coupled with the membrane diffusion of CD63. The experimentally observed decay required three components in the simulation: 1) free exosomes, 2) CD63 membrane diffusion from the endosomal membrane into the plasma membrane, and 3) tethered exosomes. Modeling with slow diffusion of the tethered exosomes (0.0015-0.004 μm2/s) accurately fits the experimental data for all temperatures. However, simulating with immobile tethers or the absence of tethers fails to replicate the data. Our model suggests that exosome release from the fusion site is incomplete due to postfusion, membrane attachment.
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Affiliation(s)
- Anarkali Mahmood
- Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado
| | - Zdeněk Otruba
- Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado
| | - Alan W Weisgerber
- Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado
| | - Max D Palay
- Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado
| | - Melodie T Nguyen
- Molecular and Cellular Biophysics Program, University of Denver, Denver, Colorado
| | - Broderick L Bills
- Molecular and Cellular Biophysics Program, University of Denver, Denver, Colorado
| | - Michelle K Knowles
- Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado; Molecular and Cellular Biophysics Program, University of Denver, Denver, Colorado.
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3
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Borges AR, Link F, Engstler M, Jones NG. The Glycosylphosphatidylinositol Anchor: A Linchpin for Cell Surface Versatility of Trypanosomatids. Front Cell Dev Biol 2021; 9:720536. [PMID: 34790656 PMCID: PMC8591177 DOI: 10.3389/fcell.2021.720536] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 09/06/2021] [Indexed: 11/20/2022] Open
Abstract
The use of glycosylphosphatidylinositol (GPI) to anchor proteins to the cell surface is widespread among eukaryotes. The GPI-anchor is covalently attached to the C-terminus of a protein and mediates the protein’s attachment to the outer leaflet of the lipid bilayer. GPI-anchored proteins have a wide range of functions, including acting as receptors, transporters, and adhesion molecules. In unicellular eukaryotic parasites, abundantly expressed GPI-anchored proteins are major virulence factors, which support infection and survival within distinct host environments. While, for example, the variant surface glycoprotein (VSG) is the major component of the cell surface of the bloodstream form of African trypanosomes, procyclin is the most abundant protein of the procyclic form which is found in the invertebrate host, the tsetse fly vector. Trypanosoma cruzi, on the other hand, expresses a variety of GPI-anchored molecules on their cell surface, such as mucins, that interact with their hosts. The latter is also true for Leishmania, which use GPI anchors to display, amongst others, lipophosphoglycans on their surface. Clearly, GPI-anchoring is a common feature in trypanosomatids and the fact that it has been maintained throughout eukaryote evolution indicates its adaptive value. Here, we explore and discuss GPI anchors as universal evolutionary building blocks that support the great variety of surface molecules of trypanosomatids.
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Affiliation(s)
- Alyssa R Borges
- Department of Cell and Developmental Biology, Biocenter, University of Würzburg, Würzburg, Germany
| | - Fabian Link
- Department of Cell and Developmental Biology, Biocenter, University of Würzburg, Würzburg, Germany
| | - Markus Engstler
- Department of Cell and Developmental Biology, Biocenter, University of Würzburg, Würzburg, Germany
| | - Nicola G Jones
- Department of Cell and Developmental Biology, Biocenter, University of Würzburg, Würzburg, Germany
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4
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Lateral diffusion of CD14 and TLR2 in macrophage plasma membrane assessed by raster image correlation spectroscopy and single particle tracking. Sci Rep 2020; 10:19375. [PMID: 33168941 PMCID: PMC7652837 DOI: 10.1038/s41598-020-76272-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Accepted: 10/23/2020] [Indexed: 01/02/2023] Open
Abstract
The diffusion of membrane receptors is central to many biological processes, such as signal transduction, molecule translocation, and ion transport, among others; consequently, several advanced fluorescence microscopy techniques have been developed to measure membrane receptor mobility within live cells. The membrane-anchored receptor cluster of differentiation 14 (CD14) and the transmembrane toll-like receptor 2 (TLR2) are important receptors in the plasma membrane of macrophages that activate the intracellular signaling cascade in response to pathogenic stimuli. The aim of the present work was to compare the diffusion coefficients of CD14 and TLR2 on the apical and basal membranes of macrophages using two fluorescence-based methods: raster image correlation spectroscopy (RICS) and single particle tracking (SPT). In the basal membrane, the diffusion coefficients obtained from SPT and RICS were found to be comparable and revealed significantly faster diffusion of CD14 compared with TLR2. In addition, RICS showed that the diffusion of both receptors was significantly faster in the apical membrane than in the basal membrane, suggesting diffusion hindrance by the adhesion of the cells to the substrate. This finding highlights the importance of selecting the appropriate membrane (i.e., basal or apical) and corresponding method when measuring receptor diffusion in live cells. Accurately knowing the diffusion coefficient of two macrophage receptors involved in the response to pathogen insults will facilitate the study of changes that occur in signaling in these cells as a result of aging and disease.
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Jin L, Zhao F, Lin W, Zhou X, Kuang C, Nedzved A, Ablameyko S, Liu X, Xu Y. Development of fan‐shaped tracker for single particle tracking. Microsc Res Tech 2020; 83:1056-1065. [DOI: 10.1002/jemt.23496] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 03/11/2020] [Accepted: 03/29/2020] [Indexed: 12/16/2022]
Affiliation(s)
- Luhong Jin
- Department of Biomedical Engineering, Key Laboratory for Biomedical Engineering of Ministry of Education, Zhejiang Provincial Key Laboratory of Cardio‐Cerebral Vascular Detection Technology and Medicinal Effectiveness AppraisalZhejiang University Hangzhou 310027 China
| | - Fengqiang Zhao
- Department of Biomedical Engineering, Key Laboratory for Biomedical Engineering of Ministry of Education, Zhejiang Provincial Key Laboratory of Cardio‐Cerebral Vascular Detection Technology and Medicinal Effectiveness AppraisalZhejiang University Hangzhou 310027 China
| | - Wanni Lin
- Department of Biomedical Engineering, Key Laboratory for Biomedical Engineering of Ministry of Education, Zhejiang Provincial Key Laboratory of Cardio‐Cerebral Vascular Detection Technology and Medicinal Effectiveness AppraisalZhejiang University Hangzhou 310027 China
| | - Xiaoxu Zhou
- Department of Biomedical Engineering, Key Laboratory for Biomedical Engineering of Ministry of Education, Zhejiang Provincial Key Laboratory of Cardio‐Cerebral Vascular Detection Technology and Medicinal Effectiveness AppraisalZhejiang University Hangzhou 310027 China
| | - Cuifang Kuang
- State Key Laboratory of Modern Optical Instrumentation, Department of Optical EngineeringZhejiang University Hangzhou 310027 China
| | - Alexander Nedzved
- National Academy of Sciences, United Institute of Informatics ProblemsBelarusian State University Minsk 220012 Republic of Belarus
| | - Sergey Ablameyko
- National Academy of Sciences, United Institute of Informatics ProblemsBelarusian State University Minsk 220012 Republic of Belarus
| | - Xu Liu
- State Key Laboratory of Modern Optical Instrumentation, Department of Optical EngineeringZhejiang University Hangzhou 310027 China
| | - Yingke Xu
- Department of Biomedical Engineering, Key Laboratory for Biomedical Engineering of Ministry of Education, Zhejiang Provincial Key Laboratory of Cardio‐Cerebral Vascular Detection Technology and Medicinal Effectiveness AppraisalZhejiang University Hangzhou 310027 China
- Department of Endocrinology, The Affiliated Sir Run Shaw HospitalZhejiang University School of Medicine Hangzhou 310016 China
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6
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Electromigration of cell surface macromolecules in DC electric fields during cell polarization and galvanotaxis. J Theor Biol 2019; 478:58-73. [DOI: 10.1016/j.jtbi.2019.06.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 06/11/2019] [Accepted: 06/14/2019] [Indexed: 12/14/2022]
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7
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Nanoscale analysis reveals no domain formation of glycosylphosphatidylinositol-anchored protein SAG1 in the plasma membrane of living Toxoplasma gondii. Histochem Cell Biol 2019; 152:365-375. [PMID: 31542792 DOI: 10.1007/s00418-019-01814-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/04/2019] [Indexed: 10/25/2022]
Abstract
Glycosylphosphatidylinositol (GPI)-anchored proteins typically localise to lipid rafts. GPI-anchored protein microdomains may be present in the plasma membrane; however, they have been studied using heterogeneously expressed GPI-anchored proteins, and the two-dimensional distributions of endogenous molecules in the plasma membrane are difficult to determine at the nanometre scale. Here, we used immunoelectron microscopy using a quick-freezing and freeze-fracture labelling (QF-FRL) method to examine the distribution of the endogenous GPI-anchored protein SAG1 in Toxoplasma gondii at the nanoscale. QF-FRL physically immobilised molecules in situ, minimising the possibility of artefactual perturbation. SAG1 labelling was observed in the exoplasmic, but not cytoplasmic, leaflets of T. gondii plasma membrane, whereas none was detected in any leaflet of the inner membrane complex. Point pattern analysis of SAG1 immunogold labelling revealed mostly random distribution in T. gondii plasma membrane. The present method obtains information on the molecular distribution of natively expressed GPI-anchored proteins and demonstrates that SAG1 in T. gondii does not form significant microdomains in the plasma membrane.
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8
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Lee S, Tan HY, Geneva II, Kruglov A, Calvert PD. Actin filaments partition primary cilia membranes into distinct fluid corrals. J Cell Biol 2018; 217:2831-2849. [PMID: 29945903 PMCID: PMC6080922 DOI: 10.1083/jcb.201711104] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Revised: 04/16/2018] [Accepted: 05/22/2018] [Indexed: 12/15/2022] Open
Abstract
Lee et al. examine the dynamics of membrane proteins within the ciliary membrane using quantum dots and 2P Super FRAP. They show that ciliary membrane proteins diffuse rapidly within highly fluid local membrane domains delimited by actin filaments. Physical properties of primary cilia membranes in living cells were examined using two independent, high-spatiotemporal-resolution approaches: fast tracking of single quantum dot–labeled G protein–coupled receptors and a novel two-photon super-resolution fluorescence recovery after photobleaching of protein ensemble. Both approaches demonstrated the cilium membrane to be partitioned into corralled domains spanning 274 ± 20 nm, within which the receptors are transiently confined for 0.71 ± 0.09 s. The mean membrane diffusion coefficient within the corrals, Dm1 = 2.9 ± 0.41 µm2/s, showed that the ciliary membranes were among the most fluid encountered. At longer times, the apparent membrane diffusion coefficient, Dm2 = 0.23 ± 0.05 µm2/s, showed that corral boundaries impeded receptor diffusion 13-fold. Mathematical simulations predict the probability of G protein–coupled receptors crossing corral boundaries to be 1 in 472. Remarkably, latrunculin A, cytochalasin D, and jasplakinolide treatments altered the corral permeability. Ciliary membranes are thus partitioned into highly fluid membrane nanodomains that are delimited by filamentous actin.
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Affiliation(s)
- Sungsu Lee
- Center for Vision Research and Department of Ophthalmology, State University of New York Upstate Medical University, Syracuse, NY.,Department of Neuroscience and Physiology, State University of New York Upstate Medical University, Syracuse, NY
| | - Han Yen Tan
- Center for Vision Research and Department of Ophthalmology, State University of New York Upstate Medical University, Syracuse, NY
| | - Ivayla I Geneva
- Center for Vision Research and Department of Ophthalmology, State University of New York Upstate Medical University, Syracuse, NY.,Department of Biochemistry and Molecular Biology, State University of New York Upstate Medical University, Syracuse, NY
| | - Aleksandr Kruglov
- Center for Vision Research and Department of Ophthalmology, State University of New York Upstate Medical University, Syracuse, NY
| | - Peter D Calvert
- Center for Vision Research and Department of Ophthalmology, State University of New York Upstate Medical University, Syracuse, NY .,Department of Biochemistry and Molecular Biology, State University of New York Upstate Medical University, Syracuse, NY.,Department of Neuroscience and Physiology, State University of New York Upstate Medical University, Syracuse, NY
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9
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Astrocyte-to-neuron communication through integrin-engaged Thy-1/CBP/Csk/Src complex triggers neurite retraction via the RhoA/ROCK pathway. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2017; 1864:243-254. [DOI: 10.1016/j.bbamcr.2016.11.006] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 10/27/2016] [Accepted: 11/07/2016] [Indexed: 12/22/2022]
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10
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Clinton RW, Mears JA. Using Scaffold Liposomes to Reconstitute Lipid-proximal Protein-protein Interactions In Vitro. J Vis Exp 2017. [PMID: 28117823 DOI: 10.3791/54971] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Studies of integral membrane proteins in vitro are frequently complicated by the presence of a hydrophobic transmembrane domain. Further complicating these studies, reincorporation of detergent-solubilized membrane proteins into liposomes is a stochastic process where protein topology is impossible to enforce. This paper offers an alternative method to these challenging techniques that utilizes a liposome-based scaffold. Protein solubility is enhanced by deletion of the transmembrane domain, and these amino acids are replaced with a tethering moiety, such as a His-tag. This tether interacts with an anchoring group (Ni2+ coordinated by nitrilotriacetic acid (NTA(Ni2+)) for His-tagged proteins), which enforces a uniform protein topology at the surface of the liposome. An example is presented wherein the interaction between Dynamin-related protein 1 (Drp1) with an integral membrane protein, Mitochondrial Fission Factor (Mff), was investigated using this scaffold liposome method. In this work, we have demonstrated the ability of Mff to efficiently recruit soluble Drp1 to the surface of liposomes, which stimulated its GTPase activity. Moreover, Drp1 was able to tubulate the Mff-decorated lipid template in the presence of specific lipids. This example demonstrates the effectiveness of scaffold liposomes using structural and functional assays and highlights the role of Mff in regulating Drp1 activity.
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Affiliation(s)
- Ryan W Clinton
- Department of Pharmacology, Center for Mitochondrial Diseases, The Cleveland Center for Membrane and Structural Biology, Case Western Reserve University School of Medicine
| | - Jason A Mears
- Department of Pharmacology, Center for Mitochondrial Diseases, The Cleveland Center for Membrane and Structural Biology, Case Western Reserve University School of Medicine;
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11
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Yamada T, Yoshimura H, Shimada R, Hattori M, Eguchi M, Fujiwara TK, Kusumi A, Ozawa T. Spatiotemporal analysis with a genetically encoded fluorescent RNA probe reveals TERRA function around telomeres. Sci Rep 2016; 6:38910. [PMID: 27958374 PMCID: PMC5153658 DOI: 10.1038/srep38910] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Accepted: 11/16/2016] [Indexed: 12/25/2022] Open
Abstract
Telomeric repeat-containing RNA (TERRA) controls the structure and length of telomeres through interactions with numerous telomere-binding proteins. However, little is known about the mechanism by which TERRA regulates the accessibility of the proteins to telomeres, mainly because of the lack of spatiotemporal information of TERRA and its-interacting proteins. We developed a fluorescent probe to visualize endogenous TERRA to investigate its dynamics in living cells. Single-particle fluorescence imaging revealed that TERRA accumulated in a telomere-neighboring region and trapped diffusive heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1), thereby inhibiting hnRNPA1 localization to the telomere. These results suggest that TERRA regulates binding of hnRNPA1 to the telomere in a region surrounding the telomere, leading to a deeper understanding of the mechanism of TERRA function.
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Affiliation(s)
- Toshimichi Yamada
- Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Hideaki Yoshimura
- Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Rintaro Shimada
- Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Mitsuru Hattori
- Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Masatoshi Eguchi
- Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Takahiro K Fujiwara
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto 606-8507, Japan
| | - Akihiro Kusumi
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto 606-8507, Japan
| | - Takeaki Ozawa
- Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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12
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Erasmus MF, Matlawska-Wasowska K, Kinjyo I, Mahajan A, Winter SS, Xu L, Horowitz M, Lidke DS, Wilson BS. Dynamic pre-BCR homodimers fine-tune autonomous survival signals in B cell precursor acute lymphoblastic leukemia. Sci Signal 2016; 9:ra116. [PMID: 27899526 DOI: 10.1126/scisignal.aaf3949] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The pre-B cell receptor (pre-BCR) is an immature form of the BCR critical for early B lymphocyte development. It is composed of the membrane-bound immunoglobulin (Ig) heavy chain, surrogate light chain components, and the signaling subunits Igα and Igβ. We developed monovalent quantum dot (QD)-labeled probes specific for Igβ to study the behavior of pre-BCRs engaged in autonomous, ligand-independent signaling in live B cells. Single-particle tracking revealed that QD-labeled pre-BCRs engaged in transient, but frequent, homotypic interactions. Receptor motion was correlated at short separation distances, consistent with the formation of dimers and higher-order oligomers. Repeated encounters between diffusing pre-BCRs appeared to reflect transient co-confinement in plasma membrane domains. In human B cell precursor acute lymphoblastic leukemia (BCP-ALL) cells, we showed that frequent, short-lived, homotypic pre-BCR interactions stimulated survival signals, including expression of BCL6, which encodes a transcriptional repressor. These survival signals were blocked by inhibitory monovalent antigen-binding antibody fragments (Fabs) specific for the surrogate light chain components of the pre-BCR or by inhibitors of the tyrosine kinases Lyn and Syk. For comparison, we evaluated pre-BCR aggregation mediated by dimeric galectin-1, which has binding sites for carbohydrate and for the surrogate light chain λ5 component. Galectin-1 binding resulted in the formation of large, highly immobile pre-BCR aggregates, which was partially relieved by the addition of lactose to prevent the cross-linking of galectin-BCR complexes to other glycosylated membrane components. Analysis of the pre-BCR and its signaling partners suggested that they could be potential targets for combination therapy in BCP-ALL.
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Affiliation(s)
- M Frank Erasmus
- Department of Pathology, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA.,UNM Comprehensive Cancer Center, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA
| | - Ksenia Matlawska-Wasowska
- UNM Comprehensive Cancer Center, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA.,Department of Pediatrics, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA
| | - Ichiko Kinjyo
- Department of Pathology, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA.,UNM Comprehensive Cancer Center, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA
| | - Avanika Mahajan
- Department of Pathology, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA.,UNM Comprehensive Cancer Center, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA
| | - Stuart S Winter
- UNM Comprehensive Cancer Center, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA.,Department of Pediatrics, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA
| | - Li Xu
- Sea Lane Biotechnologies, 2450 Bayshore Parkway, Mountain View, CA 94043, USA
| | - Michael Horowitz
- Sea Lane Biotechnologies, 2450 Bayshore Parkway, Mountain View, CA 94043, USA
| | - Diane S Lidke
- Department of Pathology, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA.,UNM Comprehensive Cancer Center, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA
| | - Bridget S Wilson
- Department of Pathology, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA. .,UNM Comprehensive Cancer Center, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA
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13
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Bernardino de la Serna J, Schütz GJ, Eggeling C, Cebecauer M. There Is No Simple Model of the Plasma Membrane Organization. Front Cell Dev Biol 2016; 4:106. [PMID: 27747212 PMCID: PMC5040727 DOI: 10.3389/fcell.2016.00106] [Citation(s) in RCA: 93] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 09/14/2016] [Indexed: 12/29/2022] Open
Abstract
Ever since technologies enabled the characterization of eukaryotic plasma membranes, heterogeneities in the distributions of its constituents were observed. Over the years this led to the proposal of various models describing the plasma membrane organization such as lipid shells, picket-and-fences, lipid rafts, or protein islands, as addressed in numerous publications and reviews. Instead of emphasizing on one model we in this review give a brief overview over current models and highlight how current experimental work in one or the other way do not support the existence of a single overarching model. Instead, we highlight the vast variety of membrane properties and components, their influences and impacts. We believe that highlighting such controversial discoveries will stimulate unbiased research on plasma membrane organization and functionality, leading to a better understanding of this essential cellular structure.
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Affiliation(s)
- Jorge Bernardino de la Serna
- Science and Technology Facilities Council, Rutherford Appleton Laboratory, Central Laser Facility, Research Complex at Harwell Harwell, UK
| | - Gerhard J Schütz
- Institute of Applied Physics, Technische Universität Wien Wien, Austria
| | - Christian Eggeling
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford Headley Way, UK
| | - Marek Cebecauer
- Department of Biophysical Chemistry, J.Heyrovsky Institute of Physical Chemistry, Czech Academy of Sciences Prague, Czech Republic
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14
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Hartel AJW, Glogger M, Jones NG, Abuillan W, Batram C, Hermann A, Fenz SF, Tanaka M, Engstler M. N-glycosylation enables high lateral mobility of GPI-anchored proteins at a molecular crowding threshold. Nat Commun 2016; 7:12870. [PMID: 27641538 PMCID: PMC5031801 DOI: 10.1038/ncomms12870] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 08/09/2016] [Indexed: 01/17/2023] Open
Abstract
The protein density in biological membranes can be extraordinarily high, but the impact of molecular crowding on the diffusion of membrane proteins has not been studied systematically in a natural system. The diversity of the membrane proteome of most cells may preclude systematic studies. African trypanosomes, however, feature a uniform surface coat that is dominated by a single type of variant surface glycoprotein (VSG). Here we study the density-dependence of the diffusion of different glycosylphosphatidylinositol-anchored VSG-types on living cells and in artificial membranes. Our results suggest that a specific molecular crowding threshold (MCT) limits diffusion and hence affects protein function. Obstacles in the form of heterologous proteins compromise the diffusion coefficient and the MCT. The trypanosome VSG-coat operates very close to its MCT. Importantly, our experiments show that N-linked glycans act as molecular insulators that reduce retarding intermolecular interactions allowing membrane proteins to function correctly even when densely packed.
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Affiliation(s)
- Andreas J. W. Hartel
- Department of Cell and Developmental Biology, Theodor-Boveri-Institute, Biocenter, University of Würzburg, Würzburg 97074, Germany
| | - Marius Glogger
- Department of Cell and Developmental Biology, Theodor-Boveri-Institute, Biocenter, University of Würzburg, Würzburg 97074, Germany
| | - Nicola G. Jones
- Department of Cell and Developmental Biology, Theodor-Boveri-Institute, Biocenter, University of Würzburg, Würzburg 97074, Germany
| | - Wasim Abuillan
- Physical Chemistry of Biosystems, Institute of Physical Chemistry, University of Heidelberg, Heidelberg 69120, Germany
| | - Christopher Batram
- Department of Cell and Developmental Biology, Theodor-Boveri-Institute, Biocenter, University of Würzburg, Würzburg 97074, Germany
| | - Anne Hermann
- Department of Cell and Developmental Biology, Theodor-Boveri-Institute, Biocenter, University of Würzburg, Würzburg 97074, Germany
| | - Susanne F. Fenz
- Department of Cell and Developmental Biology, Theodor-Boveri-Institute, Biocenter, University of Würzburg, Würzburg 97074, Germany
| | - Motomu Tanaka
- Physical Chemistry of Biosystems, Institute of Physical Chemistry, University of Heidelberg, Heidelberg 69120, Germany
- Institute for Integrated Cell-Material Science (WPI iCeMS), Kyoto University, Kyoto 606-8501, Japan
| | - Markus Engstler
- Department of Cell and Developmental Biology, Theodor-Boveri-Institute, Biocenter, University of Würzburg, Würzburg 97074, Germany
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15
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Bernstein J, Fricks J. Analysis of single particle diffusion with transient binding using particle filtering. J Theor Biol 2016; 401:109-21. [PMID: 27107737 DOI: 10.1016/j.jtbi.2016.04.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Revised: 10/27/2015] [Accepted: 04/11/2016] [Indexed: 12/27/2022]
Abstract
Diffusion with transient binding occurs in a variety of biophysical processes, including movement of transmembrane proteins, T cell adhesion, and caging in colloidal fluids. We model diffusion with transient binding as a Brownian particle undergoing Markovian switching between free diffusion when unbound and diffusion in a quadratic potential centered around a binding site when bound. Assuming the binding site is the last position of the particle in the unbound state and Gaussian observational error obscures the true position of the particle, we use particle filtering to predict when the particle is bound and to locate the binding sites. Maximum likelihood estimators of diffusion coefficients, state transition probabilities, and the spring constant in the bound state are computed with a stochastic Expectation-Maximization (EM) algorithm.
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Affiliation(s)
- Jason Bernstein
- Department of Statistics, Pennsylvania State University, University Park, PA 16802, United States
| | - John Fricks
- Department of Statistics, Pennsylvania State University, University Park, PA 16802, United States.
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16
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Richards MJ, Hsia CY, Singh RR, Haider H, Kumpf J, Kawate T, Daniel S. Membrane Protein Mobility and Orientation Preserved in Supported Bilayers Created Directly from Cell Plasma Membrane Blebs. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:2963-74. [PMID: 26812542 DOI: 10.1021/acs.langmuir.5b03415] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Membrane protein interactions with lipids are crucial for their native biological behavior, yet traditional characterization methods are often carried out on purified protein in the absence of lipids. We present a simple method to transfer membrane proteins expressed in mammalian cells to an assay-friendly, cushioned, supported lipid bilayer platform using cell blebs as an intermediate. Cell blebs, expressing either GPI-linked yellow fluorescent proteins or neon-green fused transmembrane P2X2 receptors, were induced to rupture on glass surfaces using PEGylated lipid vesicles, which resulted in planar supported membranes with over 50% mobility for multipass transmembrane proteins and over 90% for GPI-linked proteins. Fluorescent proteins were tracked, and their diffusion in supported bilayers characterized, using single molecule tracking and moment scaling spectrum (MSS) analysis. Diffusion was characterized for individual proteins as either free or confined, revealing details of the local lipid membrane heterogeneity surrounding the protein. A particularly useful result of our bilayer formation process is the protein orientation in the supported planar bilayer. For both the GPI-linked and transmembrane proteins used here, an enzymatic assay revealed that protein orientation in the planar bilayer results in the extracellular domains facing toward the bulk, and that the dominant mode of bleb rupture is via the "parachute" mechanism. Mobility, orientation, and preservation of the native lipid environment of the proteins using cell blebs offers advantages over proteoliposome reconstitution or disrupted cell membrane preparations, which necessarily result in significant scrambling of protein orientation and typically immobilized membrane proteins in SLBs. The bleb-based bilayer platform presented here is an important step toward integrating membrane proteomic studies on chip, especially for future studies aimed at understanding fundamental effects of lipid interactions on protein activity and the roles of membrane proteins in disease pathways.
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Affiliation(s)
- Mark J Richards
- School of Chemical and Biomolecular Engineering, and ‡Department of Molecular Medicine, Cornell University , Ithaca, New York 14853, United States
| | - Chih-Yun Hsia
- School of Chemical and Biomolecular Engineering, and ‡Department of Molecular Medicine, Cornell University , Ithaca, New York 14853, United States
| | - Rohit R Singh
- School of Chemical and Biomolecular Engineering, and ‡Department of Molecular Medicine, Cornell University , Ithaca, New York 14853, United States
| | - Huma Haider
- School of Chemical and Biomolecular Engineering, and ‡Department of Molecular Medicine, Cornell University , Ithaca, New York 14853, United States
| | - Julia Kumpf
- School of Chemical and Biomolecular Engineering, and ‡Department of Molecular Medicine, Cornell University , Ithaca, New York 14853, United States
| | - Toshimitsu Kawate
- School of Chemical and Biomolecular Engineering, and ‡Department of Molecular Medicine, Cornell University , Ithaca, New York 14853, United States
| | - Susan Daniel
- School of Chemical and Biomolecular Engineering, and ‡Department of Molecular Medicine, Cornell University , Ithaca, New York 14853, United States
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17
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Saha S, Anilkumar AA, Mayor S. GPI-anchored protein organization and dynamics at the cell surface. J Lipid Res 2015; 57:159-75. [PMID: 26394904 DOI: 10.1194/jlr.r062885] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Indexed: 01/05/2023] Open
Abstract
The surface of eukaryotic cells is a multi-component fluid bilayer in which glycosylphosphatidylinositol (GPI)-anchored proteins are an abundant constituent. In this review, we discuss the complex nature of the organization and dynamics of GPI-anchored proteins at multiple spatial and temporal scales. Different biophysical techniques have been utilized for understanding this organization, including fluorescence correlation spectroscopy, fluorescence recovery after photobleaching, single particle tracking, and a number of super resolution methods. Major insights into the organization and dynamics have also come from exploring the short-range interactions of GPI-anchored proteins by fluorescence (or Förster) resonance energy transfer microscopy. Based on the nanometer to micron scale organization, at the microsecond to the second time scale dynamics, a picture of the membrane bilayer emerges where the lipid bilayer appears inextricably intertwined with the underlying dynamic cytoskeleton. These observations have prompted a revision of the current models of plasma membrane organization, and suggest an active actin-membrane composite.
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Affiliation(s)
- Suvrajit Saha
- National Centre for Biological Sciences (Tata Institute of Fundamental Research), Bangalore 560065, India
| | - Anupama Ambika Anilkumar
- National Centre for Biological Sciences (Tata Institute of Fundamental Research), Bangalore 560065, India Shanmugha Arts, Science, Technology and Research Academy, Thanjavur 613401, India
| | - Satyajit Mayor
- National Centre for Biological Sciences (Tata Institute of Fundamental Research), Bangalore 560065, India Institute for Stem Cell Biology and Regenerative Medicine (inStem), Bangalore 560065, India
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18
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The molecular size of the extra-membrane domain influences the diffusion of the GPI-anchored VSG on the trypanosome plasma membrane. Sci Rep 2015; 5:10394. [PMID: 26065579 PMCID: PMC5387117 DOI: 10.1038/srep10394] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 04/13/2015] [Indexed: 12/14/2022] Open
Abstract
A plethora of proteins undergo random and passive diffusion in biological membranes. While the contribution of the membrane-embedded domain to diffusion is well established, the potential impact of the extra-membrane protein part has been largely neglected. Here, we show that the molecular length influences the diffusion coefficient of GPI-anchored proteins: smaller proteins diffuse faster than larger ones. The distinct diffusion properties of differently sized membrane proteins are biologically relevant. The variant surface glycoprotein (VSG) of African trypanosomes, for example, is sized for an effective diffusion-driven randomization on the cell surface, a process that is essential for parasite virulence. We propose that the molecular sizes of proteins dominating the cell surfaces of other eukaryotic pathogens may also be related to diffusion-limited functions.
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19
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Sevcsik E, Brameshuber M, Fölser M, Weghuber J, Honigmann A, Schütz GJ. GPI-anchored proteins do not reside in ordered domains in the live cell plasma membrane. Nat Commun 2015; 6:6969. [PMID: 25897971 PMCID: PMC4430820 DOI: 10.1038/ncomms7969] [Citation(s) in RCA: 105] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Accepted: 03/18/2015] [Indexed: 02/07/2023] Open
Abstract
The organization of proteins and lipids in the plasma membrane has been the subject of a long-lasting debate. Membrane rafts of higher lipid chain order were proposed to mediate protein interactions, but have thus far not been directly observed. Here we use protein micropatterning combined with single-molecule tracking to put current models to the test: we rearranged lipid-anchored raft proteins (glycosylphosphatidylinositol(GPI)-anchored-mGFP) directly in the live cell plasma membrane and measured the effect on the local membrane environment. Intriguingly, this treatment does neither nucleate the formation of an ordered membrane phase nor result in any enrichment of nanoscopic-ordered domains within the micropatterned regions. In contrast, we find that immobilized mGFP-GPIs behave as inert obstacles to the diffusion of other membrane constituents without influencing their membrane environment over distances beyond their physical size. Our results indicate that phase partitioning is not a fundamental element of protein organization in the plasma membrane.
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Affiliation(s)
- Eva Sevcsik
- Institute of Applied Physics, Vienna University of Technology, Wiedner Hauptstrasse 8-10, Vienna 1040, Austria
| | - Mario Brameshuber
- Institute of Applied Physics, Vienna University of Technology, Wiedner Hauptstrasse 8-10, Vienna 1040, Austria
| | - Martin Fölser
- Institute of Applied Physics, Vienna University of Technology, Wiedner Hauptstrasse 8-10, Vienna 1040, Austria
| | - Julian Weghuber
- School of Engineering and Environmental Sciences, University of Applied Sciences Upper Austria, Stelzhamerstrasse 23, Wels 4600, Austria
| | - Alf Honigmann
- Department of NanoBiophotonics, Max-Planck-Institute for Biophysical Chemistry, Am Fassberg 11, Göttingen 37077, Germany
| | - Gerhard J Schütz
- Institute of Applied Physics, Vienna University of Technology, Wiedner Hauptstrasse 8-10, Vienna 1040, Austria
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20
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Guigas G, Weiss M. Membrane protein mobility depends on the length of extra-membrane domains and on the protein concentration. SOFT MATTER 2015; 11:33-37. [PMID: 25407767 DOI: 10.1039/c4sm01846j] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Diffusion of membrane proteins is not only determined by the membrane anchor friction but also by the overall concentration of proteins and the length of their extra-membrane domains. We have studied the influence of the latter two cues by mesoscopic simulations. As a result, we have found that the total friction of membrane proteins, γ, increases approximately linearly with the length of the extra-membrane domain, L, whereas a slightly nonlinear dependence on the total protein concentration, ϕ was observed. We provide an educated guess for the functional form of γ(L, ϕ) and the associated diffusion coefficient. This expression not only matches our simulation data but it is also in favorable agreement with previously published experimental data. Our findings indicate that diffusion coefficients of membrane proteins are not solely determined by the friction of membrane anchors but also extra-membrane domains and the crowdedness of the membrane need to be considered to obtain a comprehensive view of protein diffusion on cellular membranes.
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Affiliation(s)
- Gernot Guigas
- Experimental Physics I, University of Bayreuth, 95440 Bayreuth, Germany.
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21
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Leyton L, Hagood JS. Thy-1 Modulates Neurological Cell–Cell and Cell–Matrix Interactions Through Multiple Molecular Interactions. ADVANCES IN NEUROBIOLOGY 2014; 8:3-20. [DOI: 10.1007/978-1-4614-8090-7_1] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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22
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Rajapaksha SP, Wang X, Lu HP. Suspended Lipid Bilayer for Optical and Electrical Measurements of Single Ion Channel Proteins. Anal Chem 2013; 85:8951-5. [DOI: 10.1021/ac401342u] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Suneth P. Rajapaksha
- Department of Chemistry and Center for Photochemical
Sciences, Bowling Green State University, Bowling Green, Ohio 43403, United States
| | - Xuefei Wang
- Department of Chemistry and Center for Photochemical
Sciences, Bowling Green State University, Bowling Green, Ohio 43403, United States
| | - H. Peter Lu
- Department of Chemistry and Center for Photochemical
Sciences, Bowling Green State University, Bowling Green, Ohio 43403, United States
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23
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Kiselev VY, Marenduzzo D, Goryachev AB. Lateral dynamics of proteins with polybasic domain on anionic membranes: a dynamic Monte-Carlo study. Biophys J 2011; 100:1261-70. [PMID: 21354399 DOI: 10.1016/j.bpj.2011.01.025] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Accepted: 01/13/2011] [Indexed: 10/18/2022] Open
Abstract
Positively charged polybasic domains are essential for recruiting multiple signaling proteins, such as Ras GTPases and Src kinase, to the negatively charged cellular membranes. Much less, however, is known about the influence of electrostatic interactions on the lateral dynamics of these proteins. We developed a dynamic Monte-Carlo automaton that faithfully simulates lateral diffusion of the adsorbed positively charged oligopeptides as well as the dynamics of mono- (phosphatidylserine) and polyvalent (PIP(2)) anionic lipids within the bilayer. In agreement with earlier results, our simulations reveal lipid demixing that leads to the formation of a lipid shell associated with the peptide. The computed association times and average numbers of bound lipids demonstrate that tetravalent PIP(2) interacts with the peptide much more strongly than monovalent lipid. On the spatially homogeneous membrane, the lipid shell affects the behavior of the peptide only by weakly reducing its lateral mobility. However, spatially heterogeneous distributions of monovalent lipids are found to produce peptide drift, the velocity of which is determined by the total charge of the peptide-lipid complex. We hypothesize that this predicted phenomenon may affect the spatial distribution of proteins with polybasic domains in the context of cell-signaling events that alter the local density of monovalent anionic lipids.
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Affiliation(s)
- Vladimir Yu Kiselev
- Centre for Systems Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
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24
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Covington ED, Wu MM, Lewis RS. Essential role for the CRAC activation domain in store-dependent oligomerization of STIM1. Mol Biol Cell 2010; 21:1897-907. [PMID: 20375143 PMCID: PMC2877647 DOI: 10.1091/mbc.e10-02-0145] [Citation(s) in RCA: 152] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Oligomerization of the ER Ca2+ sensor, STIM1, is the key triggering step in the activation of store-operated Ca channels. We show that the cytosolic CRAC activation domain, previously known only for its role in binding to and activating Orai1 channels, is also required for stable STIM1 oligomerization. Oligomerization of the ER Ca2+ sensor STIM1 is an essential step in store-operated Ca2+ entry. The lumenal EF-hand and SAM domains of STIM1 are believed to initiate oligomerization after Ca2+ store depletion, but the contributions of STIM1 cytosolic domains (coiled-coil 1, CC1; coiled-coil 2, CC2; CRAC activation domain, CAD) to this process are not well understood. By applying coimmunoprecipitation and fluorescence photobleaching and energy transfer techniques to truncated and mutant STIM1 proteins, we find that STIM1 cytosolic domains play distinct roles in forming both “resting” oligomers in cells with replete Ca2+ stores and higher-order oligomers in store-depleted cells. CC1 supports the formation of resting STIM1 oligomers and appears to interact with cytosolic components to slow STIM1 diffusion. On store depletion, STIM1 lacking all cytosolic domains (STIM1-ΔC) oligomerizes through EF-SAM interactions alone, but these oligomers are unstable. Addition of CC1 + CAD, but not CC1 alone, enables the formation of stable store-dependent oligomers. Within the CAD, both CC2 and C-terminal residues contribute to oligomer formation. Our results reveal a new function for the CAD: in addition to binding and activating Orai1, it is directly involved in STIM1 oligomerization, the initial event triggering store-operated Ca2+ entry.
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Affiliation(s)
- Elizabeth D Covington
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA
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25
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Kobayashi H, Azuma R, Yasunaga T. Expression of excess receptors and negative feedback control of signal pathways are required for rapid activation and prompt cessation of signal transduction. Cell Commun Signal 2009; 7:3. [PMID: 19254388 PMCID: PMC2666736 DOI: 10.1186/1478-811x-7-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2008] [Accepted: 03/03/2009] [Indexed: 01/22/2023] Open
Abstract
Background Cellular signal transduction is initiated by the binding of extracellular ligands to membrane receptors. Receptors are often expressed in excess, and cells are activated when a small number of receptors bind ligands. Intracellular signal proteins are activated at a high level soon after ligand binding, and the activation level decreases in a negative feedback manner without ligand clearance. Why are excess receptors required? What is the physiological significance of the negative feedback regulation? Results To answer these questions, we developed a Monte Carlo simulation program to kinetically analyze signal pathways using the model in which ligands are bound to receptors and then membrane complexes with other membrane proteins are formed. Our simulation results showed that excess receptors are not required for cell activation when the dissociation constant (Kd) of the ligand-receptor complex is 10-10 M or less. However, such low Kd values cause delayed signal shutdown after ligand clearance from the extracellular space. In contrast, when the Kd was 10-8 M and the ligand level was less than 1 μM, excess receptors were required for prompt signal propagation and rapid signal cessation after ligand clearance. An initial increase in active cytosolic signal proteins to a high level is required for rapid activation of cellular signal pathways, and a low level of active signal proteins is essential for the rapid shutdown of signal pathways after ligand clearance. Conclusion The present kinetic analysis revealed that excess receptors and negative feedback regulation promote activation and cessation of signal transduction with a low amount of extracellular ligand.
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Affiliation(s)
- Hiroshi Kobayashi
- Department of Biochemistry, Graduate School of Pharmaceutical Sciences, Chiba University, 1-8-1, Inohana, Chuo-ku, Chiba 260-8675, Japan.
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26
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Karnchanaphanurach P, Mirchev R, Ghiran I, Asara JM, Papahadjopoulos-Sternberg B, Nicholson-Weller A, Golan DE. C3b deposition on human erythrocytes induces the formation of a membrane skeleton-linked protein complex. J Clin Invest 2009; 119:788-801. [PMID: 19258706 DOI: 10.1172/jci36088] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2008] [Accepted: 01/07/2009] [Indexed: 11/17/2022] Open
Abstract
Decay-accelerating factor (DAF, also known as CD55), a glycosylphosphatidylinositol-linked (GPI-linked) plasma membrane protein, protects autologous cells from complement-mediated damage by inhibiting complement component 3 (C3) activation. An important physical property of GPI-anchored complement regulatory proteins such as DAF is their ability to translate laterally in the plasma membrane. Here, we used single-particle tracking and tether-pulling experiments to measure DAF lateral diffusion, lateral confinement, and membrane skeletal associations in human erythrocyte membranes. In native membranes, most DAF molecules exhibited Brownian lateral diffusion. Fluid-phase complement activation caused deposition of C3b, one of the products of C3 cleavage, onto erythrocyte glycophorin A (GPA). We then determined that DAF, C3b, GPA, and band 3 molecules were laterally immobilized in the membranes of complement-treated cells, and GPA was physically associated with the membrane skeleton. Mass spectrometry analysis further showed that band 3, alpha-spectrin, beta-spectrin, and ankyrin were present in a complex with C3b and GPA in complement-treated cells. C3b deposition was also associated with a substantial increase in erythrocyte membrane stiffness and/or viscosity. We therefore suggest that complement activation stimulates the formation of a membrane skeleton-linked DAF-C3b-GPA-band 3 complex on the erythrocyte surface. This complex may promote the removal of senescent erythrocytes from the circulation.
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Affiliation(s)
- Pallop Karnchanaphanurach
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02115, USA
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27
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Barker TH, Hagood JS. Getting a grip on Thy-1 signaling. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2008; 1793:921-3. [PMID: 19007822 DOI: 10.1016/j.bbamcr.2008.10.004] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 03/19/2008] [Revised: 10/07/2008] [Accepted: 10/08/2008] [Indexed: 11/30/2022]
Abstract
A recent study by Hermosilla et al. [T. Hermosilla, D. Munoz, R. Herrera-Molina, A. Valdivia, N. Munoz, S.U. Nham, P. Schneider, K. Burridge, A.F. Quest, L. Leyton, Direct Thy-1/alphaVbeta3 integrin interaction mediates neuron to astrocyte communication, Biochim Biophys Acta 1783 (2008) 1111-1120] demonstrates that Thy-1 on neurons binds to alphavbeta3 integrin on astrocytes via a conserved RLD motif, triggering the formation of focal adhesions and stress fibers via tyrosine phosphorylation and RhoA activation. This study adds to growing evidence regarding the signaling mechanisms and biological roles of Thy-1, an important regulator of context-dependent signaling. As knowledge of Thy-1 approaches its fiftieth year, it is critical to begin to synthesize insights from different fields to determine how this heretofore enigmatic molecule modulates cell behavior in both cis and trans.
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Affiliation(s)
- Thomas H Barker
- Biomedical Engineering, GA Tech/Emory, 313 Ferst Drive, Ste 3111 Atlanta, GA 30332-0535, USA.
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28
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Barr DJ, Ostermeyer-Fay AG, Matundan RA, Brown DA. Clathrin-independent endocytosis of ErbB2 in geldanamycin-treated human breast cancer cells. J Cell Sci 2008; 121:3155-66. [PMID: 18765569 DOI: 10.1242/jcs.020404] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The epidermal growth factor (EGF)-receptor family member ErbB2 is commonly overexpressed in human breast cancer cells and correlates with poor prognosis. Geldanamycin (GA) induces the ubiquitylation, intracellular accumulation and degradation of ErbB2. Whether GA stimulates ErbB2 internalization is controversial. We found that ErbB2 was internalized constitutively at a rate that was not affected by GA in SK-BR-3 breast cancer cells. Instead, GA treatment altered endosomal sorting, causing the transport of ErbB2 to lysosomes for degradation. In contrast to earlier work, we found that ErbB2 internalization occurred by a clathrin- and tyrosine-kinase-independent pathway that was not caveolar, because SK-BR-3 cells lack caveolae. Similar to cargo of the glycosylphosphatidylinositol (GPI)-anchored protein-enriched early endosomal compartment (GEEC) pathway, internalized ErbB2 colocalized with cholera toxin B subunit, GPI-anchored proteins and fluid, and was often seen in short tubules or large vesicles. However, in contrast to the GEEC pathway in other cells, internalization of ErbB2 and fluid in SK-BR-3 cells did not require Rho-family GTPase activity. Accumulation of ErbB2 in vesicles containing constitutively active Arf6-Q67L occurred only without GA treatment; Arf6-Q67L did not slow transport to lysosomes in GA-treated cells. Further characterization of this novel clathrin-, caveolae- and Rho-family-independent endocytic pathway might reveal new strategies for the downregulation of ErbB2 in breast cancer.
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Affiliation(s)
- Daniel J Barr
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794-5215, USA
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29
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Cairo CW, Golan DE. T cell adhesion mechanisms revealed by receptor lateral mobility. Biopolymers 2008; 89:409-19. [PMID: 18041065 DOI: 10.1002/bip.20898] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Cell surface receptors mediate the exchange of information between cells and their environment. In the case of adhesion receptors, the spatial distribution and molecular associations of the receptors are critical to their function. Therefore, understanding the mechanisms regulating the distribution and binding associations of these molecules is necessary to understand their functional regulation. Experiments characterizing the lateral mobility of adhesion receptors have revealed a set of common mechanisms that control receptor function and thus cellular behavior. The T cell provides one of the most dynamic examples of cellular adhesion. An individual T cell makes innumerable intercellular contacts with antigen presenting cells, the vascular endothelium, and many other cell types. We review here the mechanisms that regulate T cell adhesion receptor lateral mobility as a window into the molecular regulation of these systems, and we present a general framework for understanding the principles and mechanisms that are likely to be common among these and other cellular adhesion systems. We suggest that receptor lateral mobility is regulated via four major mechanisms-reorganization, recruitment, dispersion, and anchoring-and we review specific examples of T cell adhesion receptor systems that utilize one or more of these mechanisms.
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Affiliation(s)
- Christopher W Cairo
- Department of Chemistry, Alberta Ingenuity Centre for Carbohydrate Science, University of Alberta, Edmonton, Alberta, Canada T6G 2G2.
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30
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Szczesna-Skorupa E, Kemper B. Influence of protein-protein interactions on the cellular localization of cytochrome P450. Expert Opin Drug Metab Toxicol 2008; 4:123-36. [PMID: 18248308 DOI: 10.1517/17425255.4.2.123] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Microsomal CYPs are integral membrane proteins that are localized in the endoplasmic reticulum (ER), which is critical for their function. CYPs are co-translationally inserted into the rough ER membrane and are then either directly retained in the smooth ER or retained by a retrieval mechanism or targeted for ER-associated degradation. Protein-protein interactions are likely to be important for proper cellular targeting of CYPs. OBJECTIVE Progress in understanding the mechanisms of cellular targeting and ER retention of CYPs is reviewed with emphasis on the role of protein-protein interactions. Possible mechanisms of direct retention are the incorporation of CYPs into an immobile complex in the ER membrane, homooligomerization that prevents inclusion in transport vesicles, exclusion of CYP monomers from transport vesicles or targeting of CYPs to an ER subdomain away from sites of transport vesicle formation. Degradation of CYPs occurs either by lysosomal mechanisms or by the ubiquitin-proteasomal pathway. METHODS The scope of this review includes studies published in the research literature that have defined the targeting of CYPs to the ER, the retention of CYPs in the ER and the degradation of CYPs. RESULTS/CONCLUSION Targeting of CYPs to the ER is well understood and involves signal recognition particle-mediated delivery to the sec61 complex. The mechanism of ER retention of CYPs remains unclear, but self-oligomerization or binding to large immobile networks do not underlie ER retention of CYPs. An ER retention 'receptor' remains elusive, but BAP31 is important for the proper cellular localization of CYPs and Dap1p is a CYP-binding protein that is a candidate for such a receptor. Identification of protein binding partners of CYPs will be critical to understanding the mechanism of ER retention.
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Affiliation(s)
- Elzbieta Szczesna-Skorupa
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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Abi-Char J, El-Haou S, Balse E, Neyroud N, Vranckx R, Coulombe A, Hatem SN. The anchoring protein SAP97 retains Kv1.5 channels in the plasma membrane of cardiac myocytes. Am J Physiol Heart Circ Physiol 2008; 294:H1851-61. [DOI: 10.1152/ajpheart.01045.2007] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Membrane- associated guanylate kinase proteins (MAGUKs) are important determinants of localization and organization of ion channels into specific plasma membrane domains. However, their exact role in channel function and cardiac excitability is not known. We examined the effect of synapse-associated protein 97 (SAP97), a MAGUK abundantly expressed in the heart, on the function and localization of Kv1.5 subunits in cardiac myocytes. Recombinant SAP97 or Kv1.5 subunits tagged with green fluorescent protein (GFP) were overexpressed in rat neonatal cardiac myocytes and in Chinese hamster ovary (CHO) cells from adenoviral or plasmidic vectors. Immunocytochemistry, fluorescence recovery after photobleaching, and patch-clamp techniques were used to study the effects of SAP97 on the localization, mobility, and function of Kv1.5 subunits. Adenovirus-mediated SAP97 overexpression in cardiac myocytes resulted in the clustering of endogenous Kv1.5 subunits at myocyte-myocyte contacts and an increase in both the maintained component of the outward K+current, IKur(5.64 ± 0.57 pA/pF in SAP97 myocytes vs. 3.23 ± 0.43 pA/pF in controls) and the number of 4-aminopyridine-sensitive potassium channels in cell-attached membrane patches. In live myocytes, GFP-Kv1.5 subunits were mobile and organized in clusters at the basal plasma membrane, whereas SAP97 overexpression reduced their mobility. In CHO cells, Kv1.5 channels were diffusely distributed throughout the cell body and freely mobile. When coexpressed with SAP97, Kv subunits were organized in plaquelike clusters and poorly mobile. In conclusion, SAP97 regulates the K+current in cardiac myocytes by retaining and immobilizing Kv1.5 subunits in the plasma membrane. This new regulatory mechanism may contribute to the targeting of Kv channels in cardiac myocytes.
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Both MHC class II and its GPI-anchored form undergo hop diffusion as observed by single-molecule tracking. Biophys J 2008; 95:435-50. [PMID: 18339737 DOI: 10.1529/biophysj.107.123018] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Previously, investigations using single-fluorescent-molecule tracking at frame rates of up to 65 Hz, showed that the transmembrane MHC class II protein and its GPI-anchored modified form expressed in CHO cells undergo simple Brownian diffusion, without any influence of actin depolymerization with cytochalasin D. These results are at apparent variance with the view that GPI-anchored proteins stay with cholesterol-enriched raft domains, as well as with the observation that both lipids and transmembrane proteins undergo short-term confined diffusion within a compartment and long-term hop diffusion between compartments. Here, this apparent discrepancy has been resolved by reexamining the same paradigm, by using both high-speed single-particle tracking (50 kHz) and single fluorescent-molecule tracking (30 Hz). Both molecules exhibited rapid hop diffusion between 40-nm compartments, with an average dwell time of 1-3 ms in each compartment. Cytochalasin D hardly affected the hop diffusion, consistent with previous observations, whereas latrunculin A increased the compartment sizes with concomitant decreases of the hop rates, which led to an approximately 50% increase in the median macroscopic diffusion coefficient. These results indicate that the actin-based membrane skeleton influences the diffusion of both transmembrane and GPI-anchored proteins.
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Nikonov AV, Hauri HP, Lauring B, Kreibich G. Climp-63-mediated binding of microtubules to the ER affects the lateral mobility of translocon complexes. J Cell Sci 2007; 120:2248-58. [PMID: 17567679 DOI: 10.1242/jcs.008979] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Microtubules are frequently seen in close proximity to membranes of the endoplasmic reticulum (ER), and the membrane protein CLIMP-63 is thought to mediate specific interaction between these two structures. It was, therefore, of interest to investigate whether these microtubules are in fact responsible for the highly restricted lateral mobility of the translocon complexes in M3/18 cells as described before. As determined by fluorescence recovery after photobleaching, the breakdown of microtubules caused by drug treatment or by overexpression of the microtubule-severing protein spastin, resulted in an increased lateral mobility of the translocons that are assembled into polysomes. Also, the expression of a CLIMP-63 mutant lacking the microtubule-binding domain resulted in a significant increase of the lateral mobility of the translocon complexes. The most striking increase in the diffusion rate of the translocon complexes was observed in M3/18 cells transfected with a siRNA that effectively knocked down the expression of the endogenous CLIMP-63. It appears, therefore, that interaction of microtubules with the ER results in the immobilization of translocon complexes that are part of membrane-bound polysomes, and may play a role in the mechanism that segregates the rough and smooth domains of the ER.
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Affiliation(s)
- Andrei V Nikonov
- Department of Cell Biology, New York University School of Medicine, New York, NY 10016, USA
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Soong R, Macdonald PM. PEG molecular weight and lateral diffusion of PEG-ylated lipids in magnetically aligned bicelles. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:1805-14. [PMID: 17524353 DOI: 10.1016/j.bbamem.2007.03.028] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2006] [Revised: 03/07/2007] [Accepted: 03/27/2007] [Indexed: 11/30/2022]
Abstract
Lateral diffusion coefficients of PEG-ylated lipids with three different molecular weight PEG groups (1000, 2000 and 5000) were measured in magnetically-aligned bicelles using the stimulated echo (STE) pulsed field gradient (PEG) (1)H nuclear magnetic resonance (NMR) method. At concentrations below the PEG "mushroom-to-brush" transition, all three PEG-ylated lipids exhibited unrestricted lateral diffusion, with lateral diffusion coefficients comparable to those of corresponding non-PEG-ylated lipids and independent of PEG molecular weight. At concentrations above this transition, lateral diffusion slowed progressively with increasing concentration of PEG-ylated lipid as a result of surface crowding. As well, the lateral diffusion coefficients exhibited a pronounced decrease with increasing PEG group molecular weight and a diffusion-time dependence indicative of obstructed diffusion. We conclude that, while lateral diffusion of PEG-ylated lipids within lipid bilayers is determined primarily by the hydrophobic anchoring group, when crowding at the lipid bilayer surface becomes significant, the size of the extra-membranous domain, in this case the PEG group, can influence lateral diffusion, leading to decreased diffusivity with increasing size and producing obstructed diffusion at high crowding. These findings imply that similar considerations will pertain to lateral diffusion of membrane proteins with large extra-membranous domains.
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Affiliation(s)
- Ronald Soong
- Department of Chemistry, University of Toronto, 3359 Mississauga Road North, Mississauga, ON, Canada L5L 1C6
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35
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Abstract
Cell membranes are fluid but can exhibit local order that gives rise to lateral inhomogeneities, often referred to as membrane microdomains. Among the best studied yet least well understood of these microdomains are lipid rafts. Lipid rafts are hypothesized to participate in a variety of physiologic and pathologic pathways important to human health by causing the spatial segregation of proteins and lipids within the plane of the membrane. Despite the widespread implications of the raft model, major questions remain about raft size, composition, and life span. This article discusses how recent biophysical measurements of the dynamic properties of rafts and putative raft-associated proteins and lipids are being used to test the hypothesis that confinement of proteins in rafts slows and/or impairs their ability to sample their microenvironment by lateral diffusion.
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Affiliation(s)
- Anne K Kenworthy
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
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Atilgan E, Wirtz D, Sun SX. Morphology of the lamellipodium and organization of actin filaments at the leading edge of crawling cells. Biophys J 2005; 89:3589-602. [PMID: 16085776 PMCID: PMC1366852 DOI: 10.1529/biophysj.105.065383] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Lamellipodium extension, incorporating actin filament dynamics and the cell membrane, is simulated in three dimensions. The actin filament network topology and the role of actin-associated proteins such as Arp2/3 are examined. We find that the orientational pattern of the filaments is in accord with the experimental data only if the spatial orientation of the Arp2/3 complex is restricted during each branching event. We hypothesize that branching occurs when Arp2/3 is bound to Wiskott-Aldrich syndrome protein (WASP), which is in turn bound to Cdc42 signaling complex; Arp2/3 binding geometry is restricted by the membrane-bound complex. Using mechanical and energetic arguments, we show that any membrane protein that is conical or trapezoidal in shape preferentially resides at the curved regions of the plasma membrane. We hypothesize that the transmembrane receptors involved in the recruitment of Cdc42/WASP complex has this property and concentrate at the leading edge. These features, combined with the mechanical properties of the cell membrane, explain why lamellipodium is a flat organelle.
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Affiliation(s)
- Erdinç Atilgan
- Department of Mechanical Engineering and the Whitaker Institute of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, USA
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37
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Kusumi A, Nakada C, Ritchie K, Murase K, Suzuki K, Murakoshi H, Kasai RS, Kondo J, Fujiwara T. Paradigm shift of the plasma membrane concept from the two-dimensional continuum fluid to the partitioned fluid: high-speed single-molecule tracking of membrane molecules. ACTA ACUST UNITED AC 2005; 34:351-78. [PMID: 15869394 DOI: 10.1146/annurev.biophys.34.040204.144637] [Citation(s) in RCA: 807] [Impact Index Per Article: 42.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Recent advancements in single-molecule tracking methods with nanometer-level precision now allow researchers to observe the movement, recruitment, and activation of single molecules in the plasma membrane in living cells. In particular, on the basis of the observations by high-speed single-particle tracking at a frame rate of 40,000 frames s(1), the partitioning of the fluid plasma membrane into submicron compartments throughout the cell membrane and the hop diffusion of virtually all the molecules have been proposed. This could explain why the diffusion coefficients in the plasma membrane are considerably smaller than those in artificial membranes, and why the diffusion coefficient is reduced upon molecular complex formation (oligomerization-induced trapping). In this review, we first describe the high-speed single-molecule tracking methods, and then we critically review a new model of a partitioned fluid plasma membrane and the involvement of the actin-based membrane-skeleton "fences" and anchored-transmembrane protein "pickets" in the formation of compartment boundaries.
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Affiliation(s)
- Akihiro Kusumi
- Kusumi Membrane Organizer Project, Exploratory Research for Advanced Technology Organization, Department of Biological Science and Institute for Advanced Research, Nagoya University, Nagoya 464-8602, Japan.
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38
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Goodwin JS, Drake KR, Remmert CL, Kenworthy AK. Ras diffusion is sensitive to plasma membrane viscosity. Biophys J 2005; 89:1398-410. [PMID: 15923235 PMCID: PMC1366624 DOI: 10.1529/biophysj.104.055640] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The cell surface contains a variety of barriers and obstacles that slow the lateral diffusion of glycosylphosphatidylinositol (GPI)-anchored and transmembrane proteins below the theoretical limit imposed by membrane viscosity. How the diffusion of proteins residing exclusively on the inner leaflet of the plasma membrane is regulated has been largely unexplored. We show here that the diffusion of the small GTPase Ras is sensitive to the viscosity of the plasma membrane. Using confocal fluorescence recovery after photobleaching, we examined the diffusion of green fluorescent protein (GFP)-tagged HRas, NRas, and KRas in COS-7 cells loaded with or depleted of cholesterol, a well-known modulator of membrane bilayer viscosity. In cells loaded with excess cholesterol, the diffusional mobilities of GFP-HRas, GFP-NRas, and GFP-KRas were significantly reduced, paralleling the behavior of the viscosity-sensitive lipid probes DiIC(16) and DiIC(18). However, the effects of cholesterol depletion on protein and lipid diffusion in cell membranes were highly dependent on the depletion method used. Cholesterol depletion with methyl-beta-cyclodextrin slowed Ras diffusion by a viscosity-independent mechanism, whereas overnight cholesterol depletion slightly increased both protein and lipid diffusion. The ability of Ras to sense membrane viscosity may represent a general feature of proteins residing on the cytoplasmic face of the plasma membrane.
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Affiliation(s)
- J Shawn Goodwin
- Department of Molecular Physiology & Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
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39
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Abstract
Studies using a variety of microscopy-based approaches have led to a consensus that most cell-surface proteins are highly mobile and diffuse rapidly within fenced microdomains. Little attention, however, has so far been given to the analysis of the mobility of intracellular membrane proteins because of their comparative inaccessibility. Recent advances in microinjection, confocal microscopy and the construction of epitope-tagged proteins or of hybrids with an intrinsically fluorescent protein have allowed intracellular membrane proteins to be studied using approaches previously applied to characterize the mobility of cell-surface proteins. Confocal fluorescence recovery after photobleaching (c-FRAP) experiments show that intracellular membrane proteins may also be highly mobile.
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Affiliation(s)
- B Storrie
- Dept of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0308, USA
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40
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Bannas P, Adriouch S, Kahl S, Braasch F, Haag F, Koch-Nolte F. Activity and specificity of toxin-related mouse T cell ecto-ADP-ribosyltransferase ART2.2 depends on its association with lipid rafts. Blood 2005; 105:3663-70. [PMID: 15657180 DOI: 10.1182/blood-2004-08-3325] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Adenosine diphosphate (ADP)-ribosyl-transferases (ARTs) transfer ADP-ribose from nicotinamide adenine dinucleotide (NAD) onto target proteins. T cells express ART2.2, a toxin-related, glycosylphosphatidylinositol (GPI)-anchored ecto-enzyme. After the release of NAD from cells, ART2.2 ADP-ribosylates the P2X7 purinoceptor, lymphocyte function-associated antigen (LFA-1), and other membrane. Using lymphoma transfectants expressing either ART2.2 with its native GPI anchor (ART2.2-GPI) or ART2.2 with a grafted transmembrane anchor (ART2.2-Tm), we demonstrated that ART2.2-GPI but not ART2.2-Tm associated with glycosphingolipid-enriched microdomains (lipid rafts). At limiting substrate concentrations, ART2.2-GPI exhibited more than 10-fold higher activity than ART2.2-Tm. On intact cells, ART2.2-GPI ADP-ribosylated a small number of distinct target proteins. Strikingly, the disruption of lipid rafts by cyclodextrin or membrane solubilization by Triton X-100 increased the spectrum of modified target proteins. However, ART2.2 itself was a prominent target for ADP-ribosylation only when GPI anchored. Furthermore, cholesterol depletion or detergent solubilization abolished the auto-ADP-ribosylation of ART2.2. These findings imply that ART2.2-GPI, but not ART2.2-Tm, molecules are closely associated on the plasma membrane and lend support to the hypothesis that lipid rafts exist on living cells as platforms to which certain proteins are admitted and others are excluded. Our results further suggest that raft association focuses ART2.2 on specific targets that constitutively or inducibly associate with lipid rafts.
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Affiliation(s)
- Peter Bannas
- Institute of Immunology, University Hospital, Martinistr 52, D-20246 Hamburg, Germany
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41
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Deverall MA, Gindl E, Sinner EK, Besir H, Ruehe J, Saxton MJ, Naumann CA. Membrane lateral mobility obstructed by polymer-tethered lipids studied at the single molecule level. Biophys J 2004; 88:1875-86. [PMID: 15613633 PMCID: PMC1305241 DOI: 10.1529/biophysj.104.050559] [Citation(s) in RCA: 142] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Obstructed long-range lateral diffusion of phospholipids (TRITC-DHPE) and membrane proteins (bacteriorhodopsin) in a planar polymer-tethered 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine bilayer is studied using wide-field single molecule fluorescence microscopy. The obstacles are well-controlled concentrations of hydrophobic lipid-mimicking dioctadecylamine moieties in the polymer-exposed monolayer of the model membrane. Diffusion of both types of tracer molecules is well described by a percolating system with different percolation thresholds for lipids and proteins. Data analysis using a free area model of obstructed lipid diffusion indicates that phospholipids and tethered lipids interact via hard-core repulsion. A comparison to Monte Carlo lattice calculations reveals that tethered lipids act as immobile obstacles, are randomly distributed, and do not self-assemble into large-scale aggregates for low to moderate tethering concentrations. A procedure is presented to identify anomalous subdiffusion from tracking data at a single time lag. From the analysis of the cumulative distribution function of the square displacements, it was found that TRITC-DHPE and W80i show normal diffusion at lower concentrations of tethered lipids and anomalous diffusion at higher ones. This study may help improve our understanding of how lipids and proteins in biomembranes may be obstructed by very small obstacles comprising only one or very few molecules.
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Affiliation(s)
- M A Deverall
- Department of Chemistry, Indiana University-Purdue University Indianapolis, 402 N. Blackford St., Indianapolis, IN 46202, USA
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42
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Kenworthy AK, Nichols BJ, Remmert CL, Hendrix GM, Kumar M, Zimmerberg J, Lippincott-Schwartz J. Dynamics of putative raft-associated proteins at the cell surface. ACTA ACUST UNITED AC 2004; 165:735-46. [PMID: 15173190 PMCID: PMC2172371 DOI: 10.1083/jcb.200312170] [Citation(s) in RCA: 359] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Lipid rafts are conceptualized as membrane microdomains enriched in cholesterol and glycosphingolipid that serve as platforms for protein segregation and signaling. The properties of these domains in vivo are unclear. Here, we use fluorescence recovery after photobleaching to test if raft association affects a protein's ability to laterally diffuse large distances across the cell surface. The diffusion coefficients (D) of several types of putative raft and nonraft proteins were systematically measured under steady-state conditions and in response to raft perturbations. Raft proteins diffused freely over large distances (>4 μm), exhibiting Ds that varied 10-fold. This finding indicates that raft proteins do not undergo long-range diffusion as part of discrete, stable raft domains. Perturbations reported to affect lipid rafts in model membrane systems or by biochemical fractionation (cholesterol depletion, decreased temperature, and cholesterol loading) had similar effects on the diffusional mobility of raft and nonraft proteins. Thus, raft association is not the dominant factor in determining long-range protein mobility at the cell surface.
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Affiliation(s)
- Anne K Kenworthy
- Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bldg. 18T, Rm. 101, 18 Library Dr., Bethesda, MD 20895, USA
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Segretain D, Falk MM. Regulation of connexin biosynthesis, assembly, gap junction formation, and removal. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2004; 1662:3-21. [PMID: 15033576 DOI: 10.1016/j.bbamem.2004.01.007] [Citation(s) in RCA: 231] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2003] [Revised: 01/08/2004] [Accepted: 01/20/2004] [Indexed: 02/07/2023]
Abstract
Gap junctions (GJs) are the only known cellular structures that allow a direct transfer of signaling molecules from cell-to-cell by forming hydrophilic channels that bridge the opposing membranes of neighboring cells. The crucial role of GJ-mediated intercellular communication (GJIC) for coordination of development, tissue function, and cell homeostasis is now well documented. In addition, recent findings have fueled the novel concepts that connexins, although redundant, have unique and specific functions, that GJIC may play a significant role in unstable, transient cell-cell contacts, and that GJ hemi-channels by themselves may function in intra-/extracellular signaling. Assembly of these channels is a complicated, highly regulated process that includes biosynthesis of the connexin subunit proteins on endoplasmic reticulum membranes, oligomerization of compatible subunits into hexameric hemi-channels (connexons), delivery of the connexons to the plasma membrane, head-on docking of compatible connexons in the extracellular space at distinct locations, arrangement of channels into dynamic, spatially and temporally organized GJ channel aggregates (so-called plaques), and coordinated removal of channels into the cytoplasm followed by their degradation. Here we review the current knowledge of the processes that lead to GJ biosynthesis and degradation, draw comparisons to other membrane proteins, highlight novel findings, point out contradictory observations, and provide some provocative suggestive solutions.
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Affiliation(s)
- Dominique Segretain
- INSERM EMI 00-09, Université de Paris V, 45 rue des Saint Pères, 75006 Paris, France
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Sarkar A, Sreenivasan Y, Manna SK. α-Melanocyte-stimulating hormone inhibits lipopolysaccharide-induced biological responses by downregulating CD14 from macrophages. FEBS Lett 2003; 553:286-94. [PMID: 14572638 DOI: 10.1016/s0014-5793(03)01029-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Monocytes/macrophages are the first cells involved in inflammation. alpha-Melanocyte-stimulating hormone (alpha-MSH) is known to possess an anti-inflammatory role induced by a variety of stimuli; however, the molecular mechanisms underlying these effects are not clearly defined. In this report we provide evidence that alpha-MSH inhibited serum-activated lipopolysaccharide (SA-LPS)-induced proteolytic enzyme release, oxidative burst response, reactive oxygen intermediate generation, nitric oxide production, and adhesion molecule expression in monocyte-derived macrophages. alpha-MSH also inhibited SA-LPS-induced nuclear transcription factor kappaB activation not only in macrophages, but also in a T-cell line and human neutrophils isolated from fresh blood. alpha-MSH downregulated CD14, but not interleukin-1 receptor, tumor necrosis factor receptor 1 or 2 from the surface of macrophages. Anti-CD14 antibody was unable to protect alpha-MSH-mediated downregulation of CD14. Overall, our results suggest that alpha-MSH exerts its anti-inflammatory effect by a novel mechanism in macrophages through downregulating of the endotoxin receptor CD14.
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Affiliation(s)
- Abira Sarkar
- Laboratory of Immunology, Centre for DNA Fingerprinting and Diagnostics, Nacharam, 500 076 Hyderabad, India
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45
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Vega VL, De Maio A. Geldanamycin treatment ameliorates the response to LPS in murine macrophages by decreasing CD14 surface expression. Mol Biol Cell 2003; 14:764-73. [PMID: 12589068 PMCID: PMC150006 DOI: 10.1091/mbc.e02-08-0498] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Geldanamycin (GA) is an antibiotic produced by Actinomyces, which specifically inhibits the function of the heat shock protein 90 family. Treatment of a murine macrophage cell line (J774) with GA resulted in a reduced response to Escherichia coli lipopolysaccharide (LPS) as visualized by a decrease of NF-kappaB translocation into the nucleus and secretion of tumor necrosis factor alpha (TNF-alpha). To elucidate the mechanism of this effect, the expression of CD14, the formal LPS receptor, was analyzed. Cells treated with GA showed a reduced level of surface CD14 detected by immunostaining, whereas the expression of other surface receptors, such as FC-gamma receptor and tumor necrosis factor receptors (TNF-R1 and TNF-R2), was unaffected. The reduced surface level of CD14 was not due to a reduction in its expression because CD14 steady state mRNA levels or the total cellular pool of CD14 was not altered by GA treatment. Surface CD14 was more rapidly internalized after GA treatment (2-3 h) than after incubation with cycloheximide. Immunostaining of permeabilized cells after GA treatment revealed a higher intracellular content of CD14 colocalizing with calnexin, an endoplasmic reticulum (ER) protein. These results suggest that the decrease in CD14 surface expression after GA treatment is due to rapid internalization without new replacement. These effects may be due to the inhibition of Hsp90 and Grp94 by GA in macrophages.
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Affiliation(s)
- Virginia L Vega
- Division of Pediatric Surgery and Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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46
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Vrljic M, Nishimura SY, Brasselet S, Moerner WE, McConnell HM. Translational diffusion of individual class II MHC membrane proteins in cells. Biophys J 2002; 83:2681-92. [PMID: 12414700 PMCID: PMC1302352 DOI: 10.1016/s0006-3495(02)75277-6] [Citation(s) in RCA: 211] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Single-molecule epifluorescence microscopy was used to observe the translational motion of GPI-linked and native I-E(k) class II MHC membrane proteins in the plasma membrane of CHO cells. The purpose of the study was to look for deviations from Brownian diffusion that might arise from barriers to this motion. Detergent extraction had suggested that these proteins may be confined to lipid microdomains in the plasma membrane. The individual I-E(k) proteins were visualized with a Cy5-labeled peptide that binds to a specific extracytoplasmic site common to both proteins. Single-molecule trajectories were used to compute a radial distribution of displacements, yielding average diffusion coefficients equal to 0.22 (GPI-linked I-E(k)) and 0.18 microm(2)/s (native I-E(k)). The relative diffusion of pairs of proteins was also studied for intermolecular separations in the range 0.3-1.0 microm, to distinguish between free diffusion of a protein molecule and diffusion of proteins restricted to a rapidly diffusing small domain. Both analyses show that motion is predominantly Brownian. This study finds no strong evidence for significant confinement of either GPI-linked or native I-E(k) in the plasma membrane of CHO cells.
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Affiliation(s)
- Marija Vrljic
- Biophysics Program, Stanford University, Stanford, CA 94305-5080, USA
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47
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Lauf U, Giepmans BNG, Lopez P, Braconnot S, Chen SC, Falk MM. Dynamic trafficking and delivery of connexons to the plasma membrane and accretion to gap junctions in living cells. Proc Natl Acad Sci U S A 2002; 99:10446-51. [PMID: 12149451 PMCID: PMC124935 DOI: 10.1073/pnas.162055899] [Citation(s) in RCA: 251] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Certain membrane channels including acetylcholine receptors, gap junction (GJ) channels, and aquaporins arrange into large clusters in the plasma membrane (PM). However, how these channels are recruited to the clusters is unknown. To address this question, we have investigated delivery of GJ channel subunits (connexons) assembled from green fluorescent protein (GFP)-tagged connexin 43 (Cx43) to the PM and GJs in living cells. Fluorescence-photobleaching of distinct areas of Cx43-GFP GJs demonstrated that newly synthesized channels were accrued to the outer margins of channel clusters. Time-lapse microscopy further revealed that connexons were delivered in vesicular carriers traveling along microtubules from the Golgi to the PM. Routing and insertion of connexons occurred predominantly into the nonjunctional PM. These PM connexons can move laterally as shown by photo-bleaching and thus, can reach the margins of channel clusters. There, the apposing PMs are close enough to allow connexons to dock into complete GJ channels. When connexon delivery to the PM was inhibited by brefeldin A, or nocodazole pretreatment, the PM pool initially enabled connexon accrual to the clusters but further accrual was inhibited upon depletion. Taken together, our results indicate that GJ channel clusters grow by accretion at their outer margins from connexon subunits that were delivered to the nonjunctional PM, and explain how connexons in the PM can function in intra-/extracellular signaling before GJ channel formation and direct cell-cell communication.
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Affiliation(s)
- Undine Lauf
- Department of Cell Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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Fivaz M, Abrami L, Tsitrin Y, van der Goot FG. Aerolysin from Aeromonas hydrophila and related toxins. Curr Top Microbiol Immunol 2001; 257:35-52. [PMID: 11417121 DOI: 10.1007/978-3-642-56508-3_3] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- M Fivaz
- Department of Biochemistry, Faculty of Sciences, University of Geneva, 30 Quai Ernest-Ansermet, 1211 Geneva, Switzerland
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Fayen JD, Tykocinski ML, Medof ME. Glycerolphosphoinositide anchors for membrane-tethering proteins. Methods Enzymol 2001; 327:351-68. [PMID: 11044996 DOI: 10.1016/s0076-6879(00)27289-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Affiliation(s)
- J D Fayen
- Department of Pathology, Case Western Reserve University, Cleveland, Ohio 44106, USA
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Vines DJ, Lee SW, Dichek DA, Ellis V. Receptor-mediated regulation of plasminogen activator function: plasminogen activation by two directly membrane-anchored forms of urokinase. J Pept Sci 2000; 6:432-9. [PMID: 11016879 DOI: 10.1002/1099-1387(200009)6:9<432::aid-psc279>3.0.co;2-q] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The generation of the broad specificity serine protease plasmin in the pericellular environment is regulated by binding of the urokinase-type plasminogen activator (uPA) to its specific glycosylphosphatidylinositol (GPI)-anchored cell-surface receptor, uPAR. This interaction potentiates the reciprocal activation of the cell-associated zymogens pro-uPA and plasminogen. To further study the role of uPAR in this mechanism, we have expressed two directly membrane-anchored chimeric forms of uPA, one anchored by a C-terminal GPI-moiety (GPI-uPA), the other with a C-terminal transmembrane peptide (TM-uPA). These were expressed in the monocyte-like cell lines U937 and THP-1, which are excellent models for kinetic and mechanistic studies of cell-surface plasminogen activation. In both cell-lines, GPI-uPA activated cell-associated plasminogen with characteristics both qualitatively and quantitatively indistinguishable from those of uPAR-bound uPA. By contrast, TM-uPA activated cell-associated plasminogen less efficiently. This was due to effects on the K, for plasminogen activation (which was increased up to five-fold) and the efficiency of pro-uPA activation (which was decreased approximately four-fold). These observations suggest that uPAR serves two essential roles in mediating efficient cell-surface plasminogen activation. In addition to confining uPA to the cell-surface, the GPI-anchor plays an important role by increasing accessibility to substrate plasminogen and, thus, enhancing catalysis. However, the data also demonstrate that, in the presence of an alternative mechanism for uPA localization, uPAR is dispensable and, therefore, unlikely to participate in any additional interactions that may be necessary for the efficiency of this proteolytic system. In these experiments zymogen pro-uPA was unexpectedly found to be constitutively activated when expressed in THP-1 cells, suggesting the presence of an alternative plasmin-independent proteolytic activation mechanism in these cells.
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Affiliation(s)
- D J Vines
- Thrombosis Research Institute, London, UK
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