201
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Senju Y, Itoh Y, Takano K, Hamada S, Suetsugu S. Essential role of PACSIN2/syndapin-II in caveolae membrane sculpting. J Cell Sci 2011; 124:2032-40. [PMID: 21610094 DOI: 10.1242/jcs.086264] [Citation(s) in RCA: 110] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Caveolae are flask-shaped invaginations of the plasma membrane that are associated with tumor formation, pathogen entry and muscular dystrophy, through the regulation of lipids, signal transduction and endocytosis. Caveolae are generated by the fusion of caveolin-1-containing vesicles with the plasma membrane, which then participate in endocytosis via dynamin. Proteins containing membrane-sculpting F-BAR (or EFC) domains organize the membrane in clathrin-mediated endocytosis. Here, we show that the F-BAR protein PACSIN2 sculpts the plasma membrane of the caveola. The PACSIN2 F-BAR domain interacts directly with caveolin-1 by unmasking autoinhibition of PACSIN2. Furthermore, the membrane invaginations induced by the PACSIN2 F-BAR domain contained caveolin-1. Knockdown of PACSIN2 resulted in abnormal morphology of caveolin-1-associated plasma membranes, presumably as a result of decreased recruitment of dynamin-2 to caveolin-1. These results indicate that PACSIN2 mediates membrane sculpting by caveolin-1 in caveola morphology and recruits dynamin-2 for caveola fission.
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Affiliation(s)
- Yosuke Senju
- Laboratory of Membrane and Cytoskeleton Dynamics, Institute of Molecular and Cellular Biosciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
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202
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Hu J, Mukhopadhyay A, Truesdell P, Chander H, Mukhopadhyay UK, Mak AS, Craig AWB. Cdc42-interacting protein 4 is a Src substrate that regulates invadopodia and invasiveness of breast tumors by promoting MT1-MMP endocytosis. J Cell Sci 2011; 124:1739-51. [PMID: 21525036 DOI: 10.1242/jcs.078014] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Invadopodia are actin-rich membrane protrusions that promote extracellular matrix degradation and invasiveness of tumor cells. Src protein-tyrosine kinase is a potent inducer of invadopodia and tumor metastases. Cdc42-interacting protein 4 (CIP4) adaptor protein interacts with actin regulatory proteins and regulates endocytosis. Here, we show that CIP4 is a Src substrate that localizes to invadopodia in MDA-MB-231 breast tumor cells expressing activated Src (MDA-SrcYF). To probe the function of CIP4 in invadopodia, we established stable CIP4 knockdown in MDA-SrcYF cell lines by RNA interference. Compared with control cells, CIP4 knockdown cells degrade more extracellular matrix (ECM), have increased numbers of mature invadopodia and are more invasive through matrigel. Similar results are observed with knockdown of CIP4 in EGF-treated MDA-MB-231 cells. This inhibitory role of CIP4 is explained by our finding that CIP4 limits surface expression of transmembrane type I matrix metalloprotease (MT1-MMP), by promoting MT1-MMP internalization. Ectopic expression of CIP4 reduces ECM digestion by MDA-SrcYF cells, and this activity is enhanced by mutation of the major Src phosphorylation site in CIP4 (Y471). Overall, our results identify CIP4 as a suppressor of Src-induced invadopodia and invasion in breast tumor cells by promoting endocytosis of MT1-MMP.
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Affiliation(s)
- Jinghui Hu
- Department of Biochemistry, Queen's University, Kingston, ON K7L 3N6 Canada
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203
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Lyman E, Cui H, Voth GA. Reconstructing protein remodeled membranes in molecular detail from mesoscopic models. Phys Chem Chem Phys 2011; 13:10430-6. [PMID: 21503332 DOI: 10.1039/c0cp02978e] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We present a method for "inverse coarse graining," rebuilding a higher resolution model from a lower resolution one, in order to rebuild protein coats for remodeled membranes of complex topology. The specific case of membrane remodeling by N-BAR domain containing proteins is considered here, although the overall method is general and thus applicable to other membrane remodeling phenomena. Our approach begins with a previously developed, discretized mesoscopic continuum membrane model (EM2) which has been shown to capture the reticulated membrane topologies often observed for N-BAR/liposome systems by electron microscopy (EM). The information in the EM2 model-directions of the local curvatures and a low resolution sample of the membrane surface-is then used to construct a coarse-grained (CG) system with one site per lipid and 26 sites per protein. We demonstrate the approach on pieces of EM2 structures with three different topologies that have been observed by EM: A tubule, a "Y" junction, and a torus. We show that the approach leads to structures that are stable under subsequent constant temperature CG simulation, and end by considering the future application of the methodology as a hybrid approach that combines experimental information with computer modeling.
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Affiliation(s)
- Edward Lyman
- Department of Chemistry, Institute for Biophysical Dynamics, James Franck Institute, and Computation Institute, University of Chicago, 5735 S Ellis Ave., Chicago, IL 60637, USA
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204
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Kabaso D, Gongadze E, Elter P, van Rienen U, Gimsa J, Kralj-Iglič V, Iglič A. Attachment of rod-like (BAR) proteins and membrane shape. Mini Rev Med Chem 2011; 11:272-82. [PMID: 21428902 PMCID: PMC3343385 DOI: 10.2174/138955711795305353] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2010] [Revised: 03/03/2011] [Accepted: 12/24/2010] [Indexed: 11/22/2022]
Abstract
Previous studies have shown that cellular function depends on rod-like membrane proteins, among them Bin/Amphiphysin/Rvs (BAR) proteins may curve the membrane leading to physiologically important membrane invaginations and membrane protrusions. The membrane shaping induced by BAR proteins has a major role in various biological processes such as cell motility and cell growth. Different models of binding of BAR domains to the lipid bilayer are described. The binding includes hydrophobic insertion loops and electrostatic interactions between basic amino acids at the concave region of the BAR domain and negatively charged lipids. To shed light on the elusive binding dynamics, a novel experiment is proposed to expand the technique of single-molecule AFM for the traction of binding energy of a single BAR domain.
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Affiliation(s)
- D Kabaso
- Laboratory of Physics, Faculty of Electrical Engineering, University of Ljubljana, Tržaška 25, SI-1000 Ljubljana, Slovenia.
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205
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WRP/srGAP3 facilitates the initiation of spine development by an inverse F-BAR domain, and its loss impairs long-term memory. J Neurosci 2011; 31:2447-60. [PMID: 21325512 DOI: 10.1523/jneurosci.4433-10.2011] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The WAVE-associated Rac GAP, WRP, is thought to regulate key aspects of synapse development and function and may be linked to mental retardation in humans. WRP contains a newly described inverse F-BAR (IF-BAR) domain of unknown function. Our studies show that this domain senses/facilitates outward protrusions analogous to filopodia and that the molecular basis for this is likely explained by a convex lipid-binding surface on the WRP IF-BAR domain. In dendrites the IF-BAR domain of WRP forms a bud on the shaft from which precursors to spines emerge. Loss of WRP in vivo and in vitro results in reduced density of spines. In vivo this is primarily a loss of mushroom-shaped spines. Developmentally, WRP function is critical at the onset of spinogenesis, when dendritic filopodia are prevalent. Finally, because WRP is implicated in mental retardation, behaviors of WRP heterozygous and null mice have been evaluated. Results from these studies confirm that loss of WRP is linked to impaired learning and memory.
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206
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Taylor MJ, Perrais D, Merrifield CJ. A high precision survey of the molecular dynamics of mammalian clathrin-mediated endocytosis. PLoS Biol 2011; 9:e1000604. [PMID: 21445324 PMCID: PMC3062526 DOI: 10.1371/journal.pbio.1000604] [Citation(s) in RCA: 553] [Impact Index Per Article: 42.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2010] [Accepted: 02/10/2011] [Indexed: 12/15/2022] Open
Abstract
The molecular dynamics of clathrin-mediated endocytosis in living cells has been mapped with an approximately ten-fold improvement in temporal accuracy, yielding new insights into the molecular mechanism. Dual colour total internal reflection fluorescence microscopy is a powerful tool for decoding the molecular dynamics of clathrin-mediated endocytosis (CME). Typically, the recruitment of a fluorescent protein–tagged endocytic protein was referenced to the disappearance of spot-like clathrin-coated structure (CCS), but the precision of spot-like CCS disappearance as a marker for canonical CME remained unknown. Here we have used an imaging assay based on total internal reflection fluorescence microscopy to detect scission events with a resolution of ∼2 s. We found that scission events engulfed comparable amounts of transferrin receptor cargo at CCSs of different sizes and CCS did not always disappear following scission. We measured the recruitment dynamics of 34 types of endocytic protein to scission events: Abp1, ACK1, amphiphysin1, APPL1, Arp3, BIN1, CALM, CIP4, clathrin light chain (Clc), cofilin, coronin1B, cortactin, dynamin1/2, endophilin2, Eps15, Eps8, epsin2, FBP17, FCHo1/2, GAK, Hip1R, lifeAct, mu2 subunit of the AP2 complex, myosin1E, myosin6, NECAP, N-WASP, OCRL1, Rab5, SNX9, synaptojanin2β1, and syndapin2. For each protein we aligned ∼1,000 recruitment profiles to their respective scission events and constructed characteristic “recruitment signatures” that were grouped, as for yeast, to reveal the modular organization of mammalian CME. A detailed analysis revealed the unanticipated recruitment dynamics of SNX9, FBP17, and CIP4 and showed that the same set of proteins was recruited, in the same order, to scission events at CCSs of different sizes and lifetimes. Collectively these data reveal the fine-grained temporal structure of CME and suggest a simplified canonical model of mammalian CME in which the same core mechanism of CME, involving actin, operates at CCSs of diverse sizes and lifetimes. The molecular machinery of clathrin-mediated endocytosis concentrates receptors at the cell surface in a patch of membrane that curves into a vesicle, pinches off, and internalizes membrane cargo and a tiny volume of extracellular fluid. We know that dozens of proteins are involved in this process, but precisely when and where they act remains poorly understood. Here we used a fluorescence imaging assay to detect the moment of scission in living cells and used this as a reference point from which to measure the characteristic recruitment signatures of 34 fluorescently tagged endocytic proteins. Pair-wise comparison of these recruitment signatures allowed us to identify seven modules of proteins that were recruited with similar kinetics. For the most part the recruitment signatures were consistent with what was previously known about the proteins' structure and their binding affinities; however, the recruitment signatures for some components (such as some BAR and F-BAR domain proteins) could not have been predicted from existing structural or biochemical data. This study provides a paradigm for mapping molecular dynamics in living cells and provides new insights into the mechanism of clathrin-mediated endocytosis.
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Affiliation(s)
- Marcus J. Taylor
- Medical Research Council Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - David Perrais
- Université de Bordeaux, Interdisciplinary Institute for Neuroscience, UMR 5297, Bordeaux, France
- CNRS, Interdisciplinary Institute for Neuroscience, UMR 5297, Bordeaux, France
| | - Christien J. Merrifield
- Medical Research Council Laboratory of Molecular Biology, Cambridge, United Kingdom
- * E-mail:
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207
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Yamamoto H, Sutoh M, Hatakeyama S, Hashimoto Y, Yoneyama T, Koie T, Saitoh H, Yamaya K, Funyu T, Nakamura T, Ohyama C, Tsuboi S. Requirement for FBP17 in invadopodia formation by invasive bladder tumor cells. J Urol 2011; 185:1930-8. [PMID: 21421245 DOI: 10.1016/j.juro.2010.12.027] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Indexed: 01/27/2023]
Abstract
PURPOSE Invadopodia (protrusions of the plasma membrane formed by invasive tumor cells) have an essential role in bladder tumor invasion. To understand the process of bladder tumor invasion it is crucial to investigate the molecular mechanisms of invadopodia formation. We found that invasive bladder tumor cells express FBP17. In this study we examined the role of FBP17 in bladder tumor cell invadopodia formation and invasion. MATERIALS AND METHODS We used the 3 bladder tumor cell lines YTS-1, T24 and RT4 (ATCC®), and primary culture of bladder tumors from patients. Cells were stained with phalloidin for invadopodia formation. FBP17 knockdown cells were tested for invadopodia formation and subjected to invasion assay using a Transwell® cell culture chamber. We also examined the role of the extended FER-CIP4 homology and Src homology 3 domains of FBP17 in invadopodia formation in FBP17 mutant constructs. RESULTS Invadopodia formation was observed in invasive bladder tumor cells and FBP17 was localized to invadopodia in invasive cells. FBP17 knockdown decreased invadopodia formation in invasive cells to 13% to 14% (p <0.0005) and decreased their invasive capacity to 14% to 16% (p <0.001). The extended FER-CIP4 homology and Src homology 3 domains of FBP17 were necessary for invadopodia formation and invasion. CONCLUSIONS Invadopodia formation requires membrane deformation activity and recruitment of dynamin-2 mediated by FBP17. FBP17 has a critical role in the process of bladder tumor cell invasion by mediating invadopodia formation.
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Affiliation(s)
- Hayato Yamamoto
- Department of Urology, Graduate School of Medicine, Hirosaki University, Hirosaki, Japan
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208
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Boucrot E, McMahon HT. [Nucleation of clathrin-coated pits - « membrane sculptors » at work]. Med Sci (Paris) 2011; 27:122-5. [PMID: 21382316 DOI: 10.1051/medsci/2011272122] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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209
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Kawamoto S, Takasu M, Miyakawa T, Morikawa R, Oda T, Futaki S, Nagao H. Inverted micelle formation of cell-penetrating peptide studied by coarse-grained simulation: Importance of attractive force between cell-penetrating peptides and lipid head group. J Chem Phys 2011; 134:095103. [DOI: 10.1063/1.3555531] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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210
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New and unconventional approaches for advancing resolution in biological transmission electron microscopy by improving macromolecular specimen preparation and preservation. Micron 2011; 42:141-51. [DOI: 10.1016/j.micron.2010.05.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2010] [Revised: 05/16/2010] [Accepted: 05/17/2010] [Indexed: 11/21/2022]
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211
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Claret S, Roumanie O, Prouzet-Mauleon V, Lefebvre F, Thoraval D, Crouzet M, Doignon F. Evidence for functional links between the Rgd1-Rho3 RhoGAP-GTPase module and Tos2, a protein involved in polarized growth in Saccharomyces cerevisiae. FEMS Yeast Res 2010; 11:179-91. [PMID: 21143383 DOI: 10.1111/j.1567-1364.2010.00704.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The Rho GTPase-activating protein Rgd1p positively regulates the GTPase activity of Rho3p and Rho4p, which are involved in bud growth and cytokinesis, respectively, in the budding yeast Saccharomyces cerevisiae. Two-hybrid screening identified Tos2p as a candidate Rgd1p-binding protein. Further analyses confirmed that Tos2p binds to the RhoGAP Rgd1p through its C-terminal region. Both Tos2p and Rgd1p are localized to polarized growth sites during the cell cycle and associated with detergent-resistant membranes. We observed that TOS2 overexpression suppressed rgd1Δ sensitivity to a low pH. In the tos2Δ strain, the amount of GTP-bound Rho3p was increased, suggesting an influence of Tos2p on Rgd1p activity in vivo. We also showed a functional interaction between the TOS2 and the RHO3 genes: TOS2 overexpression partially suppressed the growth defect of rho3-V51 cells at a restrictive temperature. We propose that Tos2p, a protein involved in polarized growth and most probably associated with the plasma membrane, modulates the action of Rgd1p and Rho3p in S. cerevisiae.
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Affiliation(s)
- Sandra Claret
- RDPR, Institute of Cellular Biochemistry and Genetics, University of Bordeaux 2, Bordeaux, France
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212
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The Candida albicans Rgd1 is a RhoGAP protein involved in the control of filamentous growth. Fungal Genet Biol 2010; 47:1001-11. [DOI: 10.1016/j.fgb.2010.07.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2010] [Revised: 07/02/2010] [Accepted: 07/12/2010] [Indexed: 01/01/2023]
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213
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Zhao H, Pykäläinen A, Lappalainen P. I-BAR domain proteins: linking actin and plasma membrane dynamics. Curr Opin Cell Biol 2010; 23:14-21. [PMID: 21093245 DOI: 10.1016/j.ceb.2010.10.005] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2010] [Revised: 10/11/2010] [Accepted: 10/17/2010] [Indexed: 02/05/2023]
Abstract
Dynamic plasma membrane rearrangements occur during many cellular processes including endocytosis, morphogenesis, and migration. Actin polymerization together with proteins that directly deform membranes, such as the BAR superfamily proteins, is essential for generation of membrane invaginations during endocytosis. Importantly, recent studies revealed that direct membrane deformation contributes also to the formation of plasma membrane protrusions such as filopodia and lamellipodia. Inverse BAR (I-BAR) domain proteins bind phosphoinositide-rich membrane with high affinity and generate negative membrane curvature to induce plasma membrane protrusions. I-BAR domain proteins, such as IRSp53, MIM, ABBA, and IRTKS also harbor many protein-protein interaction modules that link them to actin dynamics. Thus, I-BAR domain proteins may connect direct membrane deformation to actin polymerization in cell morphogenesis and migration.
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Affiliation(s)
- Hongxia Zhao
- Institute of Biotechnology, University of Helsinki, P.O. Box 56 (Viikinkaari 9), 00014 Helsinki, Finland
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214
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Zaidel-Bar R, Joyce MJ, Lynch AM, Witte K, Audhya A, Hardin J. The F-BAR domain of SRGP-1 facilitates cell-cell adhesion during C. elegans morphogenesis. J Cell Biol 2010; 191:761-9. [PMID: 21059849 PMCID: PMC2983056 DOI: 10.1083/jcb.201005082] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2010] [Accepted: 10/11/2010] [Indexed: 12/02/2022] Open
Abstract
Robust cell-cell adhesion is critical for tissue integrity and morphogenesis, yet little is known about the molecular mechanisms controlling cell-cell junction architecture and strength. We discovered that SRGP-1 is a novel component of cell-cell junctions in Caenorhabditis elegans, localizing via its F-BAR (Bin1, Amphiphysin, and RVS167) domain and a flanking 200-amino acid sequence. SRGP-1 activity promotes an increase in membrane dynamics at nascent cell-cell contacts and the rapid formation of new junctions; in addition, srgp-1 loss of function is lethal in embryos with compromised cadherin-catenin complexes. Conversely, excess SRGP-1 activity leads to outward bending and projections of junctions. The C-terminal half of SRGP-1 interacts with the N-terminal F-BAR domain and negatively regulates its activity. Significantly, in vivo structure-function analysis establishes a role for the F-BAR domain in promoting rapid and robust cell adhesion during embryonic closure events, independent of the Rho guanosine triphosphatase-activating protein domain. These studies establish a new role for this conserved protein family in modulating cell-cell adhesion.
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Affiliation(s)
- Ronen Zaidel-Bar
- Department of Zoology, University of Wisconsin-Madison, Madison, WI 53706, USA.
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215
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Pichot CS, Arvanitis C, Hartig SM, Jensen SA, Bechill J, Marzouk S, Yu J, Frost JA, Corey SJ. Cdc42-interacting protein 4 promotes breast cancer cell invasion and formation of invadopodia through activation of N-WASp. Cancer Res 2010; 70:8347-56. [PMID: 20940394 DOI: 10.1158/0008-5472.can-09-4149] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In the earliest stages of metastasis, breast cancer cells must reorganize the cytoskeleton to affect cell shape change and promote cell invasion and motility. These events require the cytoskeletal regulators Cdc42 and Rho, their effectors such as N-WASp/WAVE, and direct inducers of actin polymerization such as Arp2/3. Little consideration has been given to molecules that shape the cell membrane. The F-BAR proteins CIP4, TOCA-1, and FBP17 generate membrane curvature and act as scaffolding proteins for activated Cdc42 and N-WASp. We found that expression of CIP4, but not TOCA-1 or FBP17, was increased in invasive breast cancer cell lines in comparison with weakly or noninvasive breast cancer cell lines. Endogenous CIP4 localized to the leading edge of migrating cells and to invadopodia in cells invading gelatin. Because CIP4 serves as a scaffolding protein for Cdc42, Src, and N-WASp, we tested whether loss of CIP4 could result in decreased N-WASp function. Interaction between CIP4 and N-WASp was epidermal growth factor responsive, and CIP4 silencing by small interfering RNA caused decreased tyrosine phosphorylation of N-WASp at a Src-dependent activation site (Y256). CIP4 silencing also impaired the migration and invasion of MDA-MB-231 cells and was associated with decreased formation of invadopodia and gelatin degradation. This study presents a new role for CIP4 in the promotion of migration and invasion of MDA-MB-231 breast cancer cells and establishes the contribution of F-BAR proteins to cancer cell motility and invasion.
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Affiliation(s)
- Christina S Pichot
- Integrative Biology and Pharmacology, University of Texas Health Science Center, Baylor College of Medicine, Houston, Texas, USA
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216
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Settles EI, Loftus AF, McKeown AN, Parthasarathy R. The vesicle trafficking protein Sar1 lowers lipid membrane rigidity. Biophys J 2010; 99:1539-45. [PMID: 20816066 PMCID: PMC2931751 DOI: 10.1016/j.bpj.2010.06.059] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Revised: 06/16/2010] [Accepted: 06/29/2010] [Indexed: 02/04/2023] Open
Abstract
The sculpting of membranes into dynamic, curved shapes is central to intracellular cargo trafficking. Though the generation of membrane curvature during trafficking necessarily involves both lipids and membrane-associated proteins, current mechanistic views focus primarily on the formation of rigid cages and curved scaffolds by protein assemblies. Here we report on a different mechanism for the control of membrane deformation, unrelated to the imposition of predefined curvature, involving modulation of membrane material properties: Sar1, a GTPase that regulates vesicle trafficking from the endoplasmic reticulum, lowers the rigidity of the lipid bilayer membrane to which it binds. In vitro assays in which optically trapped microspheres create controlled membrane deformations revealed a monotonic decline in bending modulus as a function of Sar1 concentration, down to nearly zero rigidity, indicating a dramatic lowering of the energetic cost of curvature generation. This is the first demonstration that a vesicle trafficking protein lowers the rigidity of its target membrane, leading to a new conceptual framework for vesicle biogenesis.
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Affiliation(s)
| | | | | | - Raghuveer Parthasarathy
- Department of Physics, University of Oregon, Eugene, Oregon
- Department of Materials Science Institute, University of Oregon, Eugene, Oregon
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217
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Youn JY, Friesen H, Kishimoto T, Henne WM, Kurat CF, Ye W, Ceccarelli DF, Sicheri F, Kohlwein SD, McMahon HT, Andrews BJ. Dissecting BAR domain function in the yeast Amphiphysins Rvs161 and Rvs167 during endocytosis. Mol Biol Cell 2010; 21:3054-69. [PMID: 20610658 PMCID: PMC2929998 DOI: 10.1091/mbc.e10-03-0181] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2010] [Revised: 06/25/2010] [Accepted: 06/29/2010] [Indexed: 02/05/2023] Open
Abstract
BAR domains are protein modules that bind to membranes and promote membrane curvature. One type of BAR domain, the N-BAR domain, contains an additional N-terminal amphipathic helix, which contributes to membrane-binding and bending activities. The only known N-BAR-domain proteins in the budding yeast Saccharomyces cerevisiae, Rvs161 and Rvs167, are required for endocytosis. We have explored the mechanism of N-BAR-domain function in the endocytosis process using a combined biochemical and genetic approach. We show that the purified Rvs161-Rvs167 complex binds to liposomes in a curvature-independent manner and promotes tubule formation in vitro. Consistent with the known role of BAR domain polymerization in membrane bending, we found that Rvs167 BAR domains interact with each other at cortical actin patches in vivo. To characterize N-BAR-domain function in endocytosis, we constructed yeast strains harboring changes in conserved residues in the Rvs161 and Rvs167 N-BAR domains. In vivo analysis of the rvs endocytosis mutants suggests that Rvs proteins are initially recruited to sites of endocytosis through their membrane-binding ability. We show that inappropriate regulation of complex sphingolipid and phosphoinositide levels in the membrane can impinge on Rvs function, highlighting the relationship between membrane components and N-BAR-domain proteins in vivo.
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Affiliation(s)
- Ji-Young Youn
- Department of Molecular Genetics, Banting and Best Department of Medical Research, Terrence Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, ON M5S3E1, Canada
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218
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Guo S, Bao S. srGAP2 arginine methylation regulates cell migration and cell spreading through promoting dimerization. J Biol Chem 2010; 285:35133-41. [PMID: 20810653 DOI: 10.1074/jbc.m110.153429] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Slit-Robo GTPase-activating proteins (srGAPs) are critical for neuronal migration through inactivation of Rho GTPases Cdc42, Rac1, and RhoA. Here we report that srGAP2 physically interacts with protein arginine methyltransferase 5 (PRMT5). srGAP2 localizes to the cytoplasm and plasma membrane protrusion. srGAP2 knockdown reduces cell adhesion spreading and increases cell migration, but has no effect on cell proliferation. PRMT5 binds to the N terminus of srGAP2 (225-538 aa) and methylates its C-terminal arginine residue Arg-927. The methylation mutant srGAP2-R927A fails to rescue the cell spreading rate, is unable to localize to the plasma membrane leading edge, and perturbs srGAP2 homodimer formation mediated by the F-BAR domain. These results suggest that srGAP2 arginine methylation plays important roles in cell spreading and cell migration through influencing membrane protrusion.
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Affiliation(s)
- Shaoshi Guo
- Key Laboratory of Molecular and Developmental Biology, Center for Molecular and Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
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219
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Wu M, Huang B, Graham M, Raimondi A, Heuser JE, Zhuang X, De Camilli P. Coupling between clathrin-dependent endocytic budding and F-BAR-dependent tubulation in a cell-free system. Nat Cell Biol 2010; 12:902-8. [PMID: 20729836 PMCID: PMC3338250 DOI: 10.1038/ncb2094] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2009] [Accepted: 07/29/2010] [Indexed: 12/30/2022]
Abstract
Cell-free reconstitution of membrane traffic reactions and the morphological characterization of membrane intermediates that accumulate under these conditions have helped to elucidate the physical and molecular mechanisms involved in membrane transport. To gain a better understanding of endocytosis, we have reconstituted vesicle budding and fission from isolated plasma membrane sheets and imaged these events. Electron and fluorescence microscopy, including subdiffraction-limit imaging by stochastic optical reconstruction microscopy (STORM), revealed F-BAR (FBP17) domain coated tubules nucleated by clathrin-coated buds when fission was blocked by GTPgammaS. Triggering fission by replacing GTPgammaS with GTP led not only to separation of clathrin-coated buds, but also to vesicle formation by fragmentation of the tubules. These results suggest a functional link between FBP17-dependent membrane tubulation and clathrin-dependent budding. They also show that clathrin spatially directs plasma membrane invaginations that lead to the generation of endocytic vesicles larger than those enclosed by the coat.
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MESH Headings
- Actins/antagonists & inhibitors
- Acyltransferases/metabolism
- Adenosine Triphosphate/pharmacology
- Animals
- Antibodies/immunology
- Antibodies/pharmacology
- Bridged Bicyclo Compounds, Heterocyclic/pharmacology
- Carrier Proteins/immunology
- Carrier Proteins/metabolism
- Cattle
- Cell Line
- Cell Membrane/drug effects
- Cell Membrane/physiology
- Cell Membrane/ultrastructure
- Cell Membrane Structures/drug effects
- Cell Membrane Structures/physiology
- Cell Membrane Structures/ultrastructure
- Cell-Free System/drug effects
- Cell-Free System/physiology
- Clathrin/immunology
- Clathrin/metabolism
- Coated Pits, Cell-Membrane/drug effects
- Coated Pits, Cell-Membrane/physiology
- Coated Pits, Cell-Membrane/ultrastructure
- Cytosol/metabolism
- Dynamins/metabolism
- Endocytosis/drug effects
- Endocytosis/physiology
- Fatty Acid-Binding Proteins
- Fibroblasts
- Guanosine 5'-O-(3-Thiotriphosphate)/pharmacology
- Guanosine Triphosphate/pharmacology
- Humans
- Imaging, Three-Dimensional/methods
- Mice
- Microscopy, Electron, Transmission
- Microscopy, Fluorescence
- Models, Biological
- Potoroidae
- Rats
- Receptors, Transferrin/metabolism
- Thiazolidines/pharmacology
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Affiliation(s)
- Min Wu
- Howard Hughes Medical Institute; Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06520, USA
- Department of Cell Biology, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06520, USA
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Bo Huang
- Howard Hughes Medical Institute; Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06520, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge MA 02138, USA
| | - Morven Graham
- Department of Cell Biology, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Andrea Raimondi
- Howard Hughes Medical Institute; Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06520, USA
- Department of Cell Biology, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06520, USA
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06520, USA
| | - John E. Heuser
- Department of Cell Biology and Physiology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA
| | - Xiaowei Zhuang
- Howard Hughes Medical Institute; Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06520, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge MA 02138, USA
- Department of Physics, Harvard University, Cambridge MA 02138, USA
| | - Pietro De Camilli
- Howard Hughes Medical Institute; Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06520, USA
- Department of Cell Biology, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06520, USA
- Department of Neurobiology, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06520, USA
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06520, USA
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220
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Bu W, Lim KB, Yu YH, Chou AM, Sudhaharan T, Ahmed S. Cdc42 interaction with N-WASP and Toca-1 regulates membrane tubulation, vesicle formation and vesicle motility: implications for endocytosis. PLoS One 2010; 5:e12153. [PMID: 20730103 PMCID: PMC2921345 DOI: 10.1371/journal.pone.0012153] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2010] [Accepted: 07/12/2010] [Indexed: 11/18/2022] Open
Abstract
Transducer of Cdc42-dependent actin assembly (Toca-1) consists of an F-BAR domain, a Cdc42 binding site and an SH3 domain. Toca-1 interacts with N-WASP, an activator of actin nucleation that binds Cdc42. Cdc42 may play an important role in regulating Toca-1 and N-WASP functions. We report here that the cellular expression of Toca-1 and N-WASP induces membrane tubulation and the formation of motile vesicles. Marker and uptake analysis suggests that the tubules and vesicles are associated with clathrin-mediated endocytosis. Forster resonance energy transfer (FRET) and Fluorescence Lifetime Imaging Microscopy (FLIM) analysis shows that Cdc42, N-WASP and Toca-1 form a trimer complex on the membrane tubules and vesicles and that Cdc42 interaction with N-WASP is critical for complex formation. Modulation of Cdc42 interaction with Toca-1 and/or N-WASP affects membrane tubulation, vesicle formation and vesicle motility. Thus Cdc42 may influence endocytic membrane trafficking by regulating the formation and activity of the Toca-1/N-WASP complex.
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Affiliation(s)
- Wenyu Bu
- Neural Stem Cell Laboratory, Institute of Medical Biology, Singapore, Singapore
| | - Kim Buay Lim
- Neural Stem Cell Laboratory, Institute of Medical Biology, Singapore, Singapore
| | - Yuan Hong Yu
- Neural Stem Cell Laboratory, Institute of Medical Biology, Singapore, Singapore
| | - Ai Mei Chou
- Neural Stem Cell Laboratory, Institute of Medical Biology, Singapore, Singapore
| | - Thankiah Sudhaharan
- Neural Stem Cell Laboratory, Institute of Medical Biology, Singapore, Singapore
| | - Sohail Ahmed
- Neural Stem Cell Laboratory, Institute of Medical Biology, Singapore, Singapore
- * E-mail:
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221
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Roberts-Galbraith RH, Ohi MD, Ballif BA, Chen JS, McLeod I, McDonald WH, Gygi SP, Yates JR, Gould KL. Dephosphorylation of F-BAR protein Cdc15 modulates its conformation and stimulates its scaffolding activity at the cell division site. Mol Cell 2010; 39:86-99. [PMID: 20603077 DOI: 10.1016/j.molcel.2010.06.012] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2009] [Revised: 03/22/2010] [Accepted: 04/16/2010] [Indexed: 01/11/2023]
Abstract
Cytokinesis in Schizosaccharomyces pombe requires the function of Cdc15, the founding member of the pombe cdc15 homology (PCH) family of proteins. As an early, abundant contractile ring component with multiple binding partners, Cdc15 plays a key role in organizing the ring. We demonstrate that Cdc15 phosphorylation at many sites generates a closed conformation, inhibits Cdc15 assembly at the division site in interphase, and precludes interaction of Cdc15 with its binding partners. Cdc15 dephosphorylation induces an open conformation, oligomerization, and scaffolding activity during mitosis. Cdc15 mutants with reduced phosphorylation precociously appear at the division site in filament-like structures and display increased association with protein partners and the membrane. Our results indicate that Cdc15 phosphoregulation impels both assembly and disassembly of the contractile apparatus and suggest a regulatory strategy that PCH family and BAR superfamily members might broadly employ to achieve temporal specificity in their roles as linkers between membrane and cytoskeleton.
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Affiliation(s)
- Rachel H Roberts-Galbraith
- Howard Hughes Medical Institute and Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
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222
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Glotzer M. Controlling cytokinesis through promiscuous phosphorylation outside BARs. Mol Cell 2010; 39:3-5. [PMID: 20603070 DOI: 10.1016/j.molcel.2010.06.028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
In this issue of Molecular Cell, Roberts-Galbraith and colleagues report that a key cytokinetic regulator in fission yeast, Cdc15, is phosphorylated on numerous sites that collectively, but not individually, control its oligomerization state and its associations with the plasma membrane and interacting proteins.
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Affiliation(s)
- Michael Glotzer
- Department of Molecular Genetics and Cell Biology, University of Chicago, 920 East 58th Street, Chicago, IL 60637, USA.
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223
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Dibble CF, Horst JA, Malone MH, Park K, Temple B, Cheeseman H, Barbaro JR, Johnson GL, Bencharit S. Defining the functional domain of programmed cell death 10 through its interactions with phosphatidylinositol-3,4,5-trisphosphate. PLoS One 2010; 5:e11740. [PMID: 20668527 PMCID: PMC2909203 DOI: 10.1371/journal.pone.0011740] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Accepted: 07/01/2010] [Indexed: 11/25/2022] Open
Abstract
Cerebral cavernous malformations (CCM) are vascular abnormalities of the central nervous system predisposing blood vessels to leakage, leading to hemorrhagic stroke. Three genes, Krit1 (CCM1), OSM (CCM2), and PDCD10 (CCM3) are involved in CCM development. PDCD10 binds specifically to PtdIns(3,4,5)P3 and OSM. Using threading analysis and multi-template modeling, we constructed a three-dimensional model of PDCD10. PDCD10 appears to be a six-helical-bundle protein formed by two heptad-repeat-hairpin structures (α1–3 and α4–6) sharing the closest 3D homology with the bacterial phosphate transporter, PhoU. We identified a stretch of five lysines forming an amphipathic helix, a potential PtdIns(3,4,5)P3 binding site, in the α5 helix. We generated a recombinant wild-type (WT) and three PDCD10 mutants that have two (Δ2KA), three (Δ3KA), and five (Δ5KA) K to A mutations. Δ2KA and Δ3KA mutants hypothetically lack binding residues to PtdIns(3,4,5)P3 at the beginning and the end of predicted helix, while Δ5KA completely lacks all predicted binding residues. The WT, Δ2KA, and Δ3KA mutants maintain their binding to PtdIns(3,4,5)P3. Only the Δ5KA abolishes binding to PtdIns(3,4,5)P3. Both Δ5KA and WT show similar secondary and tertiary structures; however, Δ5KA does not bind to OSM. When WT and Δ5KA are co-expressed with membrane-bound constitutively-active PI3 kinase (p110-CAAX), the majority of the WT is co-localized with p110-CAAX at the plasma membrane where PtdIns(3,4,5)P3 is presumably abundant. In contrast, the Δ5KA remains in the cytoplasm and is not present in the plasma membrane. Combining computational modeling and biological data, we propose that the CCM protein complex functions in the PI3K signaling pathway through the interaction between PDCD10 and PtdIns(3,4,5)P3.
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Affiliation(s)
- Christopher F. Dibble
- Department of Pharmacology, School of Medicine, and the Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Jeremy A. Horst
- Department of Microbiology, School of Medicine, and Department of Oral Biology, School of Dentistry, University of Washington, Seattle, Washington, United States of America
| | - Michael H. Malone
- Department of Pharmacology, School of Medicine, and the Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Kun Park
- Department of Prosthodontics and the Dental Research Center, School of Dentistry, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Brenda Temple
- Department of Pharmacology, School of Medicine, and the Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Holly Cheeseman
- Department of Prosthodontics and the Dental Research Center, School of Dentistry, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Justin R. Barbaro
- Department of Prosthodontics and the Dental Research Center, School of Dentistry, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Gary L. Johnson
- Department of Pharmacology, School of Medicine, and the Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Sompop Bencharit
- Department of Pharmacology, School of Medicine, and the Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina, United States of America
- Department of Prosthodontics and the Dental Research Center, School of Dentistry, University of North Carolina, Chapel Hill, North Carolina, United States of America
- * E-mail:
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224
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Bhatia VK, Hatzakis NS, Stamou D. A unifying mechanism accounts for sensing of membrane curvature by BAR domains, amphipathic helices and membrane-anchored proteins. Semin Cell Dev Biol 2010; 21:381-90. [DOI: 10.1016/j.semcdb.2009.12.004] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2009] [Accepted: 12/03/2009] [Indexed: 11/27/2022]
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225
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Masuda M, Mochizuki N. Structural characteristics of BAR domain superfamily to sculpt the membrane. Semin Cell Dev Biol 2010; 21:391-8. [DOI: 10.1016/j.semcdb.2010.01.010] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2009] [Revised: 01/07/2010] [Accepted: 01/08/2010] [Indexed: 11/28/2022]
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226
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Derivery E, Gautreau A. Generation of branched actin networks: assembly and regulation of the N-WASP and WAVE molecular machines. Bioessays 2010; 32:119-31. [PMID: 20091750 DOI: 10.1002/bies.200900123] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The Arp2/3 complex is a molecular machine that generates branched actin networks responsible for membrane remodeling during cell migration, endocytosis, and other morphogenetic events. This machine requires activators, which themselves are multiprotein complexes. This review focuses on recent advances concerning the assembly of stable complexes containing the most-studied activators, N-WASP and WAVE proteins, and the level of regulation that is provided by these complexes. N-WASP is the paradigmatic auto-inhibited protein, which is activated by a conformational opening. Even though this regulation has been successfully reconstituted in vitro with isolated N-WASP, the native dimeric complex with a WIP family protein has unique additional properties. WAVE proteins are part of a pentameric complex, whose basal state and activated state when bound to the Rac GTPase were recently clarified. Moreover, this review attempts to put together diverse observations concerning the WAVE complex in the conceptual frame of an in vivo assembly pathway that has gained support from the recent identification of a precursor.
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Affiliation(s)
- Emmanuel Derivery
- CNRS UPR3082, Laboratoire d'Enzymologie et de Biochimie Structurales, Bât. 34, Avenue de la Terrasse, 91198 Gif-sur-Yvette Cedex, France
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227
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Mizuno N, Jao CC, Langen R, Steven AC. Multiple modes of endophilin-mediated conversion of lipid vesicles into coated tubes: implications for synaptic endocytosis. J Biol Chem 2010; 285:23351-8. [PMID: 20484046 DOI: 10.1074/jbc.m110.143776] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Endophilin A1 is a BAR (Bin/amphiphysin/Rvs) protein abundant in neural synapses that senses and induces membrane curvature, contributing to neck formation in presynaptic endocytic vesicles. To investigate its role in membrane remodeling, we used cryoelectron microscopy to characterize structural changes induced in lipid vesicles by exposure to endophilin. The vesicles convert rapidly to coated tubules whose morphology reflects the local concentration of endophilin. Their diameters and curvature resemble those of synaptic vesicles in situ. Three-dimensional reconstructions of quasicylindrical tubes revealed arrays of BAR dimers, flanked by densities that we equate with amphipathic helices whose folding and membrane insertion were attested by EPR. We also observed the compression of bulbous coated tubes into 70-A-wide cylindrical micelles, which appear to mimic the penultimate (hemi-fission) stage of endocytosis. Our findings suggest that the adaptability of endophilin-lipid interactions underlies dynamic changes of endocytic membranes.
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Affiliation(s)
- Naoko Mizuno
- Laboratory of Structural Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
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228
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A hinge in the distal end of the PACSIN 2 F-BAR domain may contribute to membrane-curvature sensing. J Mol Biol 2010; 400:129-36. [PMID: 20471395 DOI: 10.1016/j.jmb.2010.05.008] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2010] [Revised: 05/03/2010] [Accepted: 05/05/2010] [Indexed: 11/23/2022]
Abstract
The protein kinase C and casein kinase 2 substrates in neurons (PACSINs) represent a subfamily of membrane-binding proteins characterized by an amino-terminal Bin-Amphiphysin-Rvs (F-BAR) domain. PACSINs link membrane trafficking with actin dynamics and regulate the localization of distinct cargo molecules. The F-BAR domain forms a dimer essential for lipid binding. We have obtained crystals of authentic murine PACSIN 2 that contain an ordered F-BAR domain, indicating that additional domains are flexibly connected to F-BAR. The structure shares similarity to other BAR domains and exhibits special features unique to PACSINs. These include the uneven distribution of charged residues on the concave molecular surface and a so-called wedge loop that is driven into the membrane upon binding of PACSIN. The murine PACSIN 2 F-BAR domain requires dimerization for sensing of curved membranes, and the present structure also provides a mechanism for higher-order oligomer formation. Importantly, comparison of murine with human and Drosophila PACSIN 2 F-BAR domains reveals stark differences in the orientation of distal helical segments leading to a wider crescent shape of murine PACSIN 2. We define hinge residues for these movements that may help PACSINs sense and concomitantly reinforce membrane curvature.
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229
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Henne WM, Boucrot E, Meinecke M, Evergren E, Vallis Y, Mittal R, McMahon HT. FCHo proteins are nucleators of clathrin-mediated endocytosis. Science 2010; 328:1281-4. [PMID: 20448150 DOI: 10.1126/science.1188462] [Citation(s) in RCA: 318] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Clathrin-mediated endocytosis, the major pathway for ligand internalization into eukaryotic cells, is thought to be initiated by the clustering of clathrin and adaptors around receptors destined for internalization. However, here we report that the membrane-sculpting F-BAR domain-containing Fer/Cip4 homology domain-only proteins 1 and 2 (FCHo1/2) were required for plasma membrane clathrin-coated vesicle (CCV) budding and marked sites of CCV formation. Changes in FCHo1/2 expression levels correlated directly with numbers of CCV budding events, ligand endocytosis, and synaptic vesicle marker recycling. FCHo1/2 proteins bound specifically to the plasma membrane and recruited the scaffold proteins eps15 and intersectin, which in turn engaged the adaptor complex AP2. The FCHo F-BAR membrane-bending activity was required, leading to the proposal that FCHo1/2 sculpt the initial bud site and recruit the clathrin machinery for CCV formation.
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Affiliation(s)
- William Mike Henne
- Medical Research Council, Laboratory of Molecular Biology (MRC-LMB), Hills Road, Cambridge CB2 0QH, UK
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230
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Suetsugu S. The proposed functions of membrane curvatures mediated by the BAR domain superfamily proteins. J Biochem 2010; 148:1-12. [PMID: 20435640 DOI: 10.1093/jb/mvq049] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The plasma membrane, the outermost surface of eukaryotic cells, contains various substructures, such as protrusions or invaginations, which are associated with diverse functions, including endocytosis and cell migration. These structures of the plasma membrane can be considered as tubules or inverted tubules (protrusions) of the membrane. There are six modes of membrane curvature at the plasma membrane, which are classified by the positive or negative curvature and the location of the curvature (tip, neck or shaft of the tubules). The BAR domain superfamily proteins have structurally determined positive and negative curvatures of membrane contact at their BAR, F-BAR and I-BAR domains, which generate and maintain such curved membranes by binding to the membrane. Importantly, the SH3 domains of the BAR domain superfamily proteins bind to the actin regulatory WASP/WAVE proteins, and the BAR/F-BAR/I-BAR domain-SH3 unit could orient the actin filaments towards the membrane for each subcellular structure. These membrane tubulations are also considered to function in membrane fusion and fission.
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Affiliation(s)
- Shiro Suetsugu
- Laboratory of Membrane and Cytoskeleton Dynamics, Institute of Molecular and Cellular Biosciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.
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231
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Hughson FM, Reinisch KM. Structure and mechanism in membrane trafficking. Curr Opin Cell Biol 2010; 22:454-60. [PMID: 20418086 DOI: 10.1016/j.ceb.2010.03.011] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2010] [Accepted: 03/25/2010] [Indexed: 11/19/2022]
Abstract
Cell biologists have long been interested in understanding the machinery that mediates movement of proteins and lipids between intracellular compartments. Much of this traffic is accomplished by vesicles (or other membranous carriers) that bud from one compartment and fuse with another. Given the pivotal roles that large protein complexes play in vesicular trafficking, many recent advances have relied on the combined use of X-ray crystallography and electron microscopy. Here, we discuss integrated structural studies of proteins whose assembly shapes membranes into vesicles and tubules, before turning to the so-called tethering factors that appear to orchestrate vesicle docking and fusion.
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Affiliation(s)
- Frederick M Hughson
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.
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232
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Abstract
The dynamic remolding of the actin cytoskeleton is a critical part of most cellular activities, and malfunction of cytoskeletal proteins results in various human diseases. The transition between two forms of actin, monomeric or G-actin and filamentous or F-actin, is tightly regulated in time and space by a large number of signaling, scaffolding and actin-binding proteins (ABPs). New ABPs are constantly being discovered in the post-genomic era. Most of these proteins are modular, integrating actin binding, protein-protein interaction, membrane-binding, and signaling domains. In response to extracellular signals, often mediated by Rho family GTPases, ABPs control different steps of actin cytoskeleton assembly, including filament nucleation, elongation, severing, capping, and depolymerization. This review summarizes structure-function relationships among ABPs in the regulation of actin cytoskeleton assembly.
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Affiliation(s)
- Sung Haeng Lee
- Chosun University School of Medicine, Department of Cellular and Molecular Medicine, Gwangju 501-759, Korea.
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233
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Tanaka M, Arakaki A, Matsunaga T. Identification and functional characterization of liposome tubulation protein from magnetotactic bacteria. Mol Microbiol 2010; 76:480-8. [PMID: 20345667 DOI: 10.1111/j.1365-2958.2010.07117.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Magnetotactic bacteria synthesize intracellular magnetosomes that are comprised of membrane-enveloped magnetic crystals. In this study, to identify the early stages of magnetosome formation, we isolated magnetosomes containing small magnetite crystals and those containing regular-sized magnetite crystals from Magnetospirillum magneticum AMB-1. This was achieved by using a novel size fractionation technique, resulting in the identification of a characteristic protein (Amb1018/MamY) from the small magnetite crystal fraction. The gene encoding MamY was located in the magnetosome island. Like the previously reported membrane deformation proteins, such as bin/amphiphysin/Rvs (BAR) and the dynamin family proteins, recombinant MamY protein bound directly to the liposomes, causing them to form long tubules. We established a mamY gene deletion mutant (DeltamamY) and analysed MamY protein localization in it for functional characterization of the protein in vivo. The DeltamamY mutant was found to have expanded magnetosome vesicles and a greater number of small magnetite crystals relative to the wild-type strain, suggesting that the function of the MamY protein is to constrict the magnetosome membrane during magnetosome vesicle formation, following which, the magnetite crystals grow to maturity within them.
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Affiliation(s)
- Masayoshi Tanaka
- Department of Biotechnology, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588, Japan
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234
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A mutational analysis of the endophilin-A N-BAR domain performed in living flies. PLoS One 2010; 5:e9492. [PMID: 20209138 PMCID: PMC2831065 DOI: 10.1371/journal.pone.0009492] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2009] [Accepted: 02/11/2010] [Indexed: 12/15/2022] Open
Abstract
Background Endophilin is a cytoplasmic protein with an important function in clathrin-dependent endocytosis at synapses and elsewhere. Endophilin has a BAR (Bin/Amphiphysin/Rvs-homology) domain, which is implicated in the sensing and induction of membrane curvature. Previous structure-function studies of the endophilin-A BAR domain have almost exclusively been made in reduced systems, either in vitro or ex vivo in cultured cells. To extend and complement this work, we have analyzed the role played by the structural features of the endophilin-A BAR domain in Drosophila in vivo. Methodology/Principal Findings The study is based on genetic rescue of endophilin-A (endoA) null mutants with wild type or mutated endoA transgenes. We evaluated the viability of the rescuants, the locomotor behavior in adult flies and the neurotransmission at the larval neuromuscular junction. Whereas mutating the endophilin BAR domain clearly affected adult flies, larval endophilin function was surprisingly resistant to mutagenesis. Previous reports have stressed the importance of a central appendage on the convex BAR surface, which forms a hydrophobic ridge able to directly insert into the lipid bilayer. We found that the charge-negative substitution A66D, which targets the hydrophobic ridge and was reported to completely disrupt the ability of endophilin-BAR to tubulate liposomes in vitro, rescued viability and neurotransmission with the same efficiency as wild type endoA transgenes, even in adults. A similar discrepancy was found for the hydrophilic substitutions A63S/A66S and A63S/A66S/M70Q. The A66W mutation, which introduces a bulky hydrophobic side chain and induces massive vesiculation of liposomes in vitro, strongly impeded eye development, even in presence of the endogenous endoA gene. Substantial residual function was observed in larvae rescued with the EndoA(Arf) transgene, which encodes a form of endophilin-A that completely lacks the central appendage. Whereas a mutation (D151P) designed to increase the BAR curvature was functional, another mutation (P143A, ΔLEN) designed to decrease the curvature was not. Conclusions/Significance Our results provide novel insight into the structure/function relationship of the endophilin-A BAR domain in vivo, especially with relation to synaptic function.
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Ayton GS, Lyman E, Voth GA. Hierarchical coarse-graining strategy for protein-membrane systems to access mesoscopic scales. Faraday Discuss 2010; 144:347-57; discussion 445-81. [PMID: 20158037 DOI: 10.1039/b901996k] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
An overall multiscale simulation strategy for large scale coarse-grain simulations of membrane protein systems is presented. The protein is modeled as a heterogeneous elastic network, while the lipids are modeled using the hybrid analytic-systematic (HAS) methodology, where in both cases atomistic level information obtained from molecular dynamics simulation is used to parameterize the model. A feature of this approach is that from the outset liposome length scales are employed in the simulation (i.e., on the order of 1/2 a million lipids plus protein). A route to develop highly coarse-grained models from molecular-scale information is proposed and results for N-BAR domain protein remodeling of a liposome are presented.
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Affiliation(s)
- Gary S Ayton
- Center for Biophysical Modeling and Simulation and Department of Chemistry, University of Utah, 315 S. 1400 E, Room 2020, Salt Lake City, Utah 84112-0850, USA
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236
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Shimada A, Takano K, Shirouzu M, Hanawa-Suetsugu K, Terada T, Toyooka K, Umehara T, Yamamoto M, Yokoyama S, Suetsugu S. Mapping of the basic amino-acid residues responsible for tubulation and cellular protrusion by the EFC/F-BAR domain of pacsin2/Syndapin II. FEBS Lett 2010; 584:1111-8. [PMID: 20188097 DOI: 10.1016/j.febslet.2010.02.058] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2010] [Revised: 02/10/2010] [Accepted: 02/18/2010] [Indexed: 12/22/2022]
Abstract
The extended Fes-CIP4 homology (EFC)/FCH-BAR (F-BAR) domain tubulates membranes. Overexpression of the pacsin2 EFC/F-BAR domain resulted in tubular localization inside cells and deformed liposomes into tubules in vitro. We found that overexpression of the pacsin2 EFC/F-BAR domain induced cellular microspikes, with the pacsin2 EFC/F-BAR domain concentrated at the neck. The hydrophobic loops and the basic amino-acid residues on the concave surface of the pacsin2 EFC/F-BAR domain are essential for both the microspike formation and tubulation. Since the curvature of the neck of the microspike and that of the tubulation share similar geometry, the pacsin2 EFC/F-BAR domain is considered to facilitate both microspike formation and tubulation.
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Affiliation(s)
- Atsushi Shimada
- RIKEN Systems and Structural Biology Center, Tsurumi, Yokohama, Japan
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237
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Feng Y, Hartig SM, Bechill JE, Blanchard EG, Caudell E, Corey SJ. The Cdc42-interacting protein-4 (CIP4) gene knock-out mouse reveals delayed and decreased endocytosis. J Biol Chem 2010; 285:4348-54. [PMID: 19920150 PMCID: PMC2836039 DOI: 10.1074/jbc.m109.041038] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2009] [Revised: 11/06/2009] [Indexed: 12/22/2022] Open
Abstract
The newly described F-BAR (Fer/CIP4 and Bin, amphiphysin, Rvs) family of proteins includes Cdc42-interacting protein-4 (CIP4), formin-binding protein-17 (FBP-17) and transactivator of cytoskeletal assembly-1 (Toca-1), and drives membrane deformation and invagination. Membrane remodeling affects endocytosis, vesicle budding, and cargo selection. The F-BAR family presents a novel family of proteins, which little is known about their in vivo function. We investigated the physiological role of CIP4, by creating Cip4-null mice through homologous recombination. Compared with their wild-type littermates, the Cip4-null mice displayed lower early post-prandial glucose levels. Adipocytes isolated from Cip4-null mice exhibited increased [(14)C]2-deoxyglucose uptake compared with cells from wild-type mice. The enhanced insulin sensitivity was not due to higher levels of insulin or phospho-Akt, a critical player in insulin signaling. However, higher glucose transporter 4 (GLUT4) levels were detected in muscle membrane fractions in Cip4-null mice under insulin stimulation. Mouse embryonic fibroblasts from Cip4-null mice demonstrated decreased transferrin uptake, fluorescein isothiocyanate-dextran, and horseradish peroxidase uptake, indicating that CIP4 affects multiple modes of endocytosis. These studies demonstrate a physiological role for CIP4 in endocytosis leading to a whole animal phenotype.
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Affiliation(s)
- Yanming Feng
- From the Division of Pediatrics, University of Texas, MD Anderson Cancer Center, Houston, Texas 77030
- the Departments of Pediatrics and Cellular and Molecular Biology and the Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Chicago, Illinois 60611, and
| | - Sean M. Hartig
- From the Division of Pediatrics, University of Texas, MD Anderson Cancer Center, Houston, Texas 77030
- the Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030
| | - John E. Bechill
- the Departments of Pediatrics and Cellular and Molecular Biology and the Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Chicago, Illinois 60611, and
| | - Elisabeth G. Blanchard
- From the Division of Pediatrics, University of Texas, MD Anderson Cancer Center, Houston, Texas 77030
| | - Eva Caudell
- From the Division of Pediatrics, University of Texas, MD Anderson Cancer Center, Houston, Texas 77030
| | - Seth J. Corey
- From the Division of Pediatrics, University of Texas, MD Anderson Cancer Center, Houston, Texas 77030
- the Departments of Pediatrics and Cellular and Molecular Biology and the Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Chicago, Illinois 60611, and
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238
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You JJ, Lin-Chao S. Gas7 functions with N-WASP to regulate the neurite outgrowth of hippocampal neurons. J Biol Chem 2010; 285:11652-66. [PMID: 20150425 PMCID: PMC3283256 DOI: 10.1074/jbc.m109.051094] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Neuritogenesis, or neurite outgrowth, is a critical process for neuronal differentiation and maturation in which growth cones are formed from highly dynamic actin structures. Gas7 (growth arrest-specific gene 7), a new member of the PCH (Pombe Cdc15 homology) protein family, is predominantly expressed in neurons and is required for the maturation of primary cultured Purkinje neurons as well as the neuron-like differentiation of PC12 cells upon nerve growth factor stimulation. We report that Gas7 co-localizes and physically interacts with N-WASP, a key regulator of Arp2/3 complex-mediated actin polymerization, in the cortical region of Gas7-transfected Neuro-2a cells and growth cones of hippocampal neurons. The interaction between Gas7 and N-WASP is mediated by WW-Pro domains, which is unique in the PCH protein family, where most interactions are of the SH3-Pro kind. The interaction contributes to the formation of membrane protrusions and processes by recruiting the Arp2/3 complex in a Cdc42-independent manner. Importantly, specific interaction between Gas7 and N-WASP is required for regular neurite outgrowth of hippocampal neurons. The data demonstrate an essential role of Gas7 through its interaction with N-WASP during neuronal maturation/differentiation.
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Affiliation(s)
- Jhong-Jhe You
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
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239
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Munn AL, Aspenström P. Second international conference on F-BAR proteins: October 1-3, 2009 at Rånäs Slott, Sweden. Cell Adh Migr 2010; 4:81-93. [PMID: 20139700 DOI: 10.4161/cam.4.1.10769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Affiliation(s)
- Alan L Munn
- School of Medical Science, Griffith University (Gold Coast), Southport, QLD, AU.
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240
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Saarikangas J, Zhao H, Lappalainen P. Regulation of the actin cytoskeleton-plasma membrane interplay by phosphoinositides. Physiol Rev 2010; 90:259-89. [PMID: 20086078 DOI: 10.1152/physrev.00036.2009] [Citation(s) in RCA: 362] [Impact Index Per Article: 25.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The plasma membrane and the underlying cortical actin cytoskeleton undergo continuous dynamic interplay that is responsible for many essential aspects of cell physiology. Polymerization of actin filaments against cellular membranes provides the force for a number of cellular processes such as migration, morphogenesis, and endocytosis. Plasma membrane phosphoinositides (especially phosphatidylinositol bis- and trisphosphates) play a central role in regulating the organization and dynamics of the actin cytoskeleton by acting as platforms for protein recruitment, by triggering signaling cascades, and by directly regulating the activities of actin-binding proteins. Furthermore, a number of actin-associated proteins, such as BAR domain proteins, are capable of directly deforming phosphoinositide-rich membranes to induce plasma membrane protrusions or invaginations. Recent studies have also provided evidence that the actin cytoskeleton-plasma membrane interactions are misregulated in a number of pathological conditions such as cancer and during pathogen invasion. Here, we summarize the wealth of knowledge on how the cortical actin cytoskeleton is regulated by phosphoinositides during various cell biological processes. We also discuss the mechanisms by which interplay between actin dynamics and certain membrane deforming proteins regulate the morphology of the plasma membrane.
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Affiliation(s)
- Juha Saarikangas
- Program in Cell and Molecular Biology, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
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241
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Madsen KL, Bhatia VK, Gether U, Stamou D. BAR domains, amphipathic helices and membrane-anchored proteins use the same mechanism to sense membrane curvature. FEBS Lett 2010; 584:1848-55. [PMID: 20122931 DOI: 10.1016/j.febslet.2010.01.053] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2010] [Accepted: 01/26/2010] [Indexed: 12/24/2022]
Abstract
The internal membranes of eukaryotic cells are all twists and bends characterized by high curvature. During recent years it has become clear that specific proteins sustain these curvatures while others simply recognize membrane shape and use it as "molecular information" to organize cellular processes in space and time. Here we discuss this new important recognition process termed membrane curvature sensing (MCS). First, we review a new fluorescence-based experimental method that allows characterization of MCS using measurements on single vesicles and compare it to sensing assays that use bulk/ensemble liposome samples of different mean diameter. Next, we describe two different MCS protein motifs (amphipathic helices and BAR domains) and suggest that in both cases curvature sensitive membrane binding results from asymmetric insertion of hydrophobic amino acids in the lipid membrane. This mechanism can be extended to include the insertion of alkyl chain in the lipid membrane and consequently palmitoylated and myristoylated proteins are predicted to display similar curvature sensitive binding. Surprisingly, in all the aforementioned cases, MCS is predominantly mediated by a higher density of binding sites on curved membranes instead of higher affinity as assumed so far. Finally, we integrate these new insights into the debate about which motifs are involved in sensing versus induction of membrane curvature and what role MCS proteins may play in biology.
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Affiliation(s)
- K L Madsen
- Molecular Neuropharmacology Group, Department of Neuroscience and Pharmacology, The Panum Institute, University of Copenhagen, Copenhagen, Denmark.
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242
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Members of the CIP4 family of proteins participate in the regulation of platelet-derived growth factor receptor-beta-dependent actin reorganization and migration. Biol Cell 2010; 102:215-30. [PMID: 19909236 DOI: 10.1042/bc20090033] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND INFORMATION The F-BAR {Fes/CIP4 [Cdc42 (cell division cycle 42)-interacting protein 4] homology and BAR (Bin/amphiphysin/Rvs)} proteins have emerged as important co-ordinators of signalling pathways that regulate actin assembly and membrane dynamics. The presence of the F-BAR domain is the hallmark of this family of proteins and the CIP4 (Cdc42-interacting protein 4) was one of the first identified vertebrate F-BAR proteins. There are three human CIP4 paralogues, namely CIP4, FBP17 (formin-binding protein 17) and Toca-1 (transducer of Cdc42-dependent actin assembly 1). The CIP4-like proteins have been implicated in Cdc42-dependent actin reorganization and in regulation of membrane deformation events visible as tubulation of lipid bilayers. RESULTS We performed side-by-side analyses of the three CIP4 paralogues. We found that the three CIP4-like proteins vary in their effectiveness to catalyse membrane tubulation and actin reorganization. Moreover, we show that the CIP4-dependent membrane tubulation is enhanced in the presence of activated Cdc42. Some F-BAR members have been shown to have a role in the endocytosis of the EGF (epidermal growth factor) receptor and this prompted us to study the involvement of the CIP4-like proteins in signalling of the PDGFRbeta [PDGF (platelet-derived growth factor) beta-receptor]. We found that knock-down of CIP4-like proteins resulted in a prolonged formation of PDGF-induced dorsal ruffles, as well as an increased PDGF-dependent cell migration. This was most likely a consequence of a sustained PDGFRbeta activation caused by delayed internalization of the receptor in the cells treated with siRNA (small interfering RNA) specific for the CIP4-like proteins. CONCLUSIONS Our findings show that CIP4-like proteins induced membrane tubulation downstream of Cdc42 and that they have important roles in PDGF-dependent actin reorganization and cell migration by regulating internalization and activity of the PDGFRbeta. Moreover, the results suggest an important role for the CIP4-like proteins in the regulation of the activity of the PDGFRbeta.
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243
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Abstract
Phase plates are a new technique in the field of cryo-electron microscopy. They provide improved contrast and signal-to-noise ratio in images of radiation sensitive specimens. Thin film phase plates are being tested in biological applications and have demonstrated benefits for single particle analysis and cryo-tomography. There are still unsolved problems, such as reliability of manufacturing and deterioration of performance with time. Several other types of phase plates are currently under development and may become available for cryo-microscopy in near future. Presented is a short overview of the current state of the field as well as ideas for the future directions. Also included is a detailed description of the instrumentation requirements and the experimental procedures for phase plate application.
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Affiliation(s)
- Radostin Danev
- Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Okazaki, Japan
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244
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Takenawa T. Phosphoinositide-binding interface proteins involved in shaping cell membranes. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2010; 86:509-23. [PMID: 20467216 PMCID: PMC3108299 DOI: 10.2183/pjab.86.509] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The mechanism by which cell and cell membrane shapes are created has long been a subject of great interest. Among the phosphoinositide-binding proteins, a group of proteins that can change the shape of membranes, in addition to the phosphoinositide-binding ability, has been found. These proteins, which contain membrane-deforming domains such as the BAR, EFC/F-BAR, and the IMD/I-BAR domains, led to inward-invaginated tubes or outward protrusions of the membrane, resulting in a variety of membrane shapes. Furthermore, these proteins not only bind to phosphoinositide, but also to the N-WASP/WAVE complex and the actin polymerization machinery, which generates a driving force to shape the membranes.
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Affiliation(s)
- Tadaomi Takenawa
- Laboratory of Lipid Biochemistry, Graduate School of Medicine, Kobe University, Hyogo, Japan.
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245
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Suetsugu S, Toyooka K, Senju Y. Subcellular membrane curvature mediated by the BAR domain superfamily proteins. Semin Cell Dev Biol 2009; 21:340-9. [PMID: 19963073 DOI: 10.1016/j.semcdb.2009.12.002] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Accepted: 12/02/2009] [Indexed: 12/14/2022]
Abstract
The Bin-Amphiphysin-Rvs167 (BAR) domain superfamily consists of proteins containing the BAR domain, the extended FCH (EFC)/FCH-BAR (F-BAR) domain, or the IRSp53-MIM homology domain (IMD)/inverse BAR (I-BAR) domain. These domains bind membranes through electrostatic interactions between the negative charges of the membranes and the positive charges on the structural surface of homo-dimeric BAR domain superfamily members. Some BAR superfamily members have membrane-penetrating insertion loops, which also contribute to the membrane binding by the proteins. The membrane-binding surface of each BAR domain superfamily member has its own unique curvature that governs or senses the curvature of the membrane for BAR-domain binding. The wide range of BAR-domain surface curvatures correlates with the various invaginations and protrusions of cells. Therefore, each BAR domain superfamily member may generate and recognize the curvature of the membrane of each subcellular structure, such as clathrin-coated pits or filopodia. The BAR domain superfamily proteins may regulate their own catalytic activity or that of their binding proteins, depending on the membrane curvature of their corresponding subcellular structures.
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Affiliation(s)
- Shiro Suetsugu
- Laboratory of Membrane and Cytoskeleton Dynamics, Institute of Molecular and Cellular Biosciences, The University of Tokyo, Tokyo, Japan.
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246
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Boettner DR, D'Agostino JL, Torres OT, Daugherty-Clarke K, Uygur A, Reider A, Wendland B, Lemmon SK, Goode BL. The F-BAR protein Syp1 negatively regulates WASp-Arp2/3 complex activity during endocytic patch formation. Curr Biol 2009; 19:1979-87. [PMID: 19962315 DOI: 10.1016/j.cub.2009.10.062] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2009] [Revised: 10/11/2009] [Accepted: 10/16/2009] [Indexed: 02/07/2023]
Abstract
BACKGROUND Actin polymerization by Arp2/3 complex must be tightly regulated to promote clathrin-mediated endocytosis. Although many Arp2/3 complex activators have been identified, mechanisms for its negative regulation have remained more elusive. To address this, we analyzed the yeast arp2-7 allele, which is biochemically unique in causing unregulated actin assembly in vitro in the absence of Arp2/3 activators. RESULTS We examined endocytosis in arp2-7 mutants by live-cell imaging of Sla1-GFP, a coat marker, and Abp1-RFP, which marks the later actin phase of endocytosis. Sla1-GFP and Abp1-RFP lifetimes were accelerated in arp2-7 mutants, which is opposite to actin nucleation-impaired arp2 alleles or deletions of Arp2/3 activators. We performed a screen for multicopy suppressors of arp2-7 and identified SYP1, an FCHO1 homolog, which contains F-BAR and AP-2micro homology domains. Overexpression of SYP1 in arp2-7 cells slowed Sla1-GFP lifetimes closer to wild-type cells. Further, purified Syp1 directly inhibited Las17/WASp stimulation of Arp2/3 complex-mediated actin assembly in vitro. This activity was mapped to a fragment of Syp1 located between its F-BAR and AP-2micro homology domains and depends on sequences in Las17/WASp outside of the VCA domain. CONCLUSIONS Together, these data identify Syp1 as a novel negative regulator of WASp-Arp2/3 complex that helps choreograph the precise timing of actin assembly during endocytosis.
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Affiliation(s)
- Douglas R Boettner
- Department of Molecular and Cellular Pharmacology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
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247
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Edeling MA, Sanker S, Shima T, Umasankar PK, Höning S, Kim HY, Davidson LA, Watkins SC, Tsang M, Owen DJ, Traub LM. Structural requirements for PACSIN/Syndapin operation during zebrafish embryonic notochord development. PLoS One 2009; 4:e8150. [PMID: 19997509 PMCID: PMC2780292 DOI: 10.1371/journal.pone.0008150] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2009] [Accepted: 11/05/2009] [Indexed: 11/18/2022] Open
Abstract
PACSIN/Syndapin proteins are membrane-active scaffolds that participate in endocytosis. The structure of the Drosophila Syndapin N-terminal EFC domain reveals a crescent shaped antiparallel dimer with a high affinity for phosphoinositides and a unique membrane-inserting prong upon the concave surface. Combined structural, biochemical and reverse genetic approaches in zebrafish define an important role for Syndapin orthologue, Pacsin3, in the early formation of the notochord during embryonic development. In pacsin3-morphant embryos, midline convergence of notochord precursors is defective as axial mesodermal cells fail to polarize, migrate and differentiate properly. The pacsin3 morphant phenotype of a stunted body axis and contorted trunk is rescued by ectopic expression of Drosophila Syndapin, and depends critically on both the prong that protrudes from the surface of the bowed Syndapin EFC domain and the ability of the antiparallel dimer to bind tightly to phosphoinositides. Our data confirm linkage between directional migration, endocytosis and cell specification during embryonic morphogenesis and highlight a key role for Pacsin3 in this coupling in the notochord.
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Affiliation(s)
- Melissa A. Edeling
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
| | - Subramaniam Sanker
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Takaki Shima
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - P. K. Umasankar
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Stefan Höning
- Institute of Biochemistry I and Center for Molecular Medicine, University of Cologne, Cologne, Germany
| | - Hye Y. Kim
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Lance A. Davidson
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Simon C. Watkins
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Michael Tsang
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - David J. Owen
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
| | - Linton M. Traub
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- * E-mail:
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248
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Lundmark R, Carlsson SR. Driving membrane curvature in clathrin-dependent and clathrin-independent endocytosis. Semin Cell Dev Biol 2009; 21:363-70. [PMID: 19931628 DOI: 10.1016/j.semcdb.2009.11.014] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2009] [Accepted: 11/16/2009] [Indexed: 10/20/2022]
Abstract
Cellular activity depends to a large extent on membrane bilayer dynamics. Many processes, such as organelle biogenesis and vesicular transport, rely on alterations in membrane structure and shape. It is now widely accepted that intracellular membrane curvature generation and remodelling is mediated and regulated by protein action, and the mechanisms behind the processes are currently being revealed. Here, we will briefly discuss the key principles of membrane deformation and focus on different endocytic events that use various kinds of proteins to shape the plasma membrane into transport carriers. The entry routes are adopted to make sure that a vast variety of molecules on the cell surface can be regulated by endocytosis. The principles for membrane sculpting of endocytic carriers can be viewed either from a perspective of rigid coat budding or of flexible opportunistic budding. We will discuss these principles and their implications, focusing on clathrin-dependent and -independent carrier formation and the proteins involved in the respective pathways.
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Affiliation(s)
- Richard Lundmark
- Department of Medical Biochemistry and Biophysics, Umeå University, 901 87 Umeå, Sweden.
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249
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Khelashvili G, Harries D, Weinstein H. Modeling membrane deformations and lipid demixing upon protein-membrane interaction: the BAR dimer adsorption. Biophys J 2009; 97:1626-35. [PMID: 19751667 DOI: 10.1016/j.bpj.2009.07.006] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2009] [Revised: 07/02/2009] [Accepted: 07/07/2009] [Indexed: 12/13/2022] Open
Abstract
We use a self-consistent mean-field theory, designed to investigate membrane reshaping and lipid demixing upon interaction with proteins, to explore BAR domains interacting with large patches of lipid membranes of heterogeneous compositions. The computational model includes contributions to the system free energy from electrostatic interactions and elastic energies of the membrane, as well as salt and lipid mixing entropies. The results from our simulation of a single adsorbing Amphiphysin BAR dimer indicate that it is capable of stabilizing a significantly curved membrane. However, we predict that such deformations will occur only for membrane patches that have the inherent propensity for high curvature, reflected in the tendency to create local distortions that closely match the curvature of the BAR dimer itself. Such favorable preconditioning for BAR-membrane interaction may be the result of perturbations such as local lipid demixing induced by the interaction, or of a prior insertion of the BAR domain's amphiphatic N-helix. From our simulations it appears that local segregation of charged lipids under the influence of the BAR dimer cannot produce high enough asymmetry between bilayer leaflets to induce significant bending. In the absence of additional energy contributions that favor membrane asymmetry, the membrane will remain nearly flat upon single BAR dimer adsorption, relative to the undulation expected from thermal fluctuations. Thus, we conclude that the N-helix insertions have a critical mechanistic role in the local perturbation and curving of the membrane, which is then stabilized by the electrostatic interaction with the BAR dimer. We discuss how these results can be used to estimate the tendency of BARs to bend membranes in terms of a spatially nonisotropic spontaneous curvature.
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Affiliation(s)
- George Khelashvili
- Department of Physiology and Biophysics, Weill Medical College of Cornell University, New York, New York, USA.
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250
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New insights into BAR domain-induced membrane remodeling. Biophys J 2009; 97:1616-25. [PMID: 19751666 DOI: 10.1016/j.bpj.2009.06.036] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2009] [Revised: 06/28/2009] [Accepted: 06/30/2009] [Indexed: 11/22/2022] Open
Abstract
Mesoscopic simulations and electron microscopy of N-BAR domain-induced liposome remodeling are used to characterize the process of liposome tubulation and vesiculation. The overall process of membrane remodeling is found to involve complex couplings among the N-BAR protein density, the degree of N-BAR oligomerization, and the membrane density. A comparison of complex remodeled liposome structures from mesoscopic simulations with those measured by electron microscopy experiments suggests that the process of membrane remodeling can be described via an appropriate mesoscopic free energy framework. Liposome remodeling more representative of F-BAR domains is also presented within the mesoscopic simulation framework.
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