1
|
Briata P, Mastracci L, Zapparoli E, Caputo L, Ferracci E, Silvestri A, Garuti A, Hamadou MH, Inga A, Marcaccini E, Grillo F, Bucci G, Puri P, Beznoussenko G, Mironov A, Chiacchiera F, Gherzi R. LncRNA EPR regulates intestinal mucus production and protects against inflammation and tumorigenesis. Nucleic Acids Res 2023; 51:5193-5209. [PMID: 37070602 PMCID: PMC10250242 DOI: 10.1093/nar/gkad257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Revised: 03/14/2023] [Accepted: 03/28/2023] [Indexed: 04/19/2023] Open
Abstract
The long non-coding RNA EPR is expressed in epithelial tissues, binds to chromatin and controls distinct biological activities in mouse mammary gland cells. Because of its high expression in the intestine, in this study we have generated a colon-specific conditional targeted deletion (EPR cKO) to evaluate EPR in vivo functions in mice. EPR cKO mice display epithelium hyperproliferation, impaired mucus production and secretion, as well as inflammatory infiltration in the proximal portion of the large intestine. RNA sequencing analysis reveals a rearrangement of the colon crypt transcriptome with strong reduction of goblet cell-specific factors including those involved in the synthesis, assembly, transport and control of mucus proteins. Further, colon mucosa integrity and permeability are impaired in EPR cKO mice, and this results in higher susceptibility to dextran sodium sulfate (DSS)-induced colitis and tumor formation. Human EPR is down-regulated in human cancer cell lines as well as in human cancers, and overexpression of EPR in a colon cancer cell line results in enhanced expression of pro-apoptotic genes. Mechanistically, we show that EPR directly interacts with select genes involved in mucus metabolism whose expression is reduced in EPR cKO mice and that EPR deletion causes tridimensional chromatin organization changes.
Collapse
Affiliation(s)
- Paola Briata
- Gene Expression Regulation Laboratory, IRCCS Ospedale Policlinico San Martino, 16132 Genova, Italy
| | - Luca Mastracci
- Pathology Unit, IRCCS Ospedale Policlinico San Martino, 16132 Genova, Italy
- Pathology Unit, Department of Surgical and Diagnostic Sciences (DISC), University of Genoa, Genova, Italy
| | - Ettore Zapparoli
- Center for Omics Sciences, IRCCS Ospedale San Raffaele, 20132 Milano, Italy
| | - Luca Caputo
- Development, Aging and Regeneration Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, USA
| | - Elisa Ferracci
- Laboratory of Stem Cells and Cancer Genomics, Department of Cellular, Computational and Integrative Biology (CIBIO), University of Trento, Trento, Italy
| | | | - Anna Garuti
- Translational Genomics, IRCCS Ospedale Policlinico San Martino, 16132 Genova, Italy
| | - Meriem Hadjer Hamadou
- Department of Cellular, Computational and Integrative Biology (CIBIO), University of Trento, Trento, Italy
| | - Alberto Inga
- Department of Cellular, Computational and Integrative Biology (CIBIO), University of Trento, Trento, Italy
| | - Elisa Marcaccini
- Gene Expression Regulation Laboratory, IRCCS Ospedale Policlinico San Martino, 16132 Genova, Italy
| | - Federica Grillo
- Pathology Unit, IRCCS Ospedale Policlinico San Martino, 16132 Genova, Italy
- Pathology Unit, Department of Surgical and Diagnostic Sciences (DISC), University of Genoa, Genova, Italy
| | - Gabriele Bucci
- Center for Omics Sciences, IRCCS Ospedale San Raffaele, 20132 Milano, Italy
| | - Pier Lorenzo Puri
- Development, Aging and Regeneration Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, USA
| | - Galina Beznoussenko
- The AIRC Institute of Molecular Oncology, Via Adamello 16, 20139 Milano, Italy
| | - Alexander Mironov
- The AIRC Institute of Molecular Oncology, Via Adamello 16, 20139 Milano, Italy
| | - Fulvio Chiacchiera
- Laboratory of Stem Cells and Cancer Genomics, Department of Cellular, Computational and Integrative Biology (CIBIO), University of Trento, Trento, Italy
| | - Roberto Gherzi
- Gene Expression Regulation Laboratory, IRCCS Ospedale Policlinico San Martino, 16132 Genova, Italy
| |
Collapse
|
2
|
The Diffusion Model of Intra-Golgi Transport Has Limited Power. Int J Mol Sci 2023; 24:ijms24021375. [PMID: 36674888 PMCID: PMC9861033 DOI: 10.3390/ijms24021375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 12/31/2022] [Accepted: 01/04/2023] [Indexed: 01/12/2023] Open
Abstract
The Golgi complex (GC) is the main station along the cell biosecretory pathway. Until now, mechanisms of intra-Golgi transport (IGT) have remained unclear. Herein, we confirm that the goodness-of-fit of the regression lines describing the exit of a cargo from the Golgi zone (GZ) corresponds to an exponential decay. When the GC was empty before the re-initiation of the intra-Golgi transport, this parameter of the curves describing the kinetics of different cargoes (which are deleted in Golgi vesicles) with different diffusional mobilities within the GZ as well as their exit from the GZ was maximal for the piecewise nonlinear regression, wherein the first segment was horizontal, while the second segment was similar to the exponential decay. The kinetic curve describing cargo exit from the GC per se resembled a linear decay. The Monte-Carlo simulation revealed that such curves reflect the role of microtubule growth in cells with a central GC or the random hovering of ministacks in cells lacking a microtubule. The synchronization of cargo exit from the GC already filled with a cargo using the wave synchronization protocol did not reveal the equilibration of cargo within a Golgi stack, which would be expected from the diffusion model (DM) of IGT. Moreover, not all cisternae are connected to each other in mini-stacks that are transporting membrane proteins. Finally, the kinetics of post-Golgi carriers and the important role of SNAREs for IGT at different level of IGT also argue against the DM of IGT.
Collapse
|
3
|
Effect of the First Feeding on Enterocytes of Newborn Rats. Int J Mol Sci 2022; 23:ijms232214179. [PMID: 36430658 PMCID: PMC9699143 DOI: 10.3390/ijms232214179] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Revised: 11/06/2022] [Accepted: 11/11/2022] [Indexed: 11/18/2022] Open
Abstract
The transcytosis of lipids through enterocytes occurs through the delivery of lipid micelles to the microvilli of enterocytes, consumption of lipid derivates by the apical plasma membrane (PM) and then their delivery to the membrane of the smooth ER attached to the basolateral PM. The SER forms immature chylomicrons (iChMs) in the ER lumen. iChMs are delivered at the Golgi complex (GC) where they are subjected to additional glycosylation resulting in maturation of iChMs. ChMs are secreted into the intercellular space and delivered into the lumen of lymphatic capillaries (LCs). The overloading of enterocytes with lipids induces the formation of lipid droplets inside the lipid bilayer of the ER membranes and transcytosis becomes slower. Here, we examined components of the enterocyte-to-lymphatic barriers in newly born rats before the first feeding and after it. In contrast to adult animals, enterocytes of newborns rats exhibited apical endocytosis and a well-developed subapical endosomal tubular network. These enterocytes uptake membranes from amniotic fluid. Then these membranes are transported across the polarized GC and secreted into the intercellular space. The enterocytes did not contain COPII-coated buds on the granular ER. The endothelium of blood capillaries situated near the enterocytes contained only a few fenestrae. The LCs were similar to those in adult animals. The first feeding induced specific alterations of enterocytes, which were similar to those observed after the lipid overloading of enterocytes in adult rats. Enlarged chylomicrons were stopped at the level of the LAMP2 and Neu1 positive post-Golgi structures, secreted, fused, delivered to the interstitial space, captured by the LCs and transported to the lymph node, inducing the movement of macrophages from lymphatic follicles into its sinuses. The macrophages captured the ChMs, preventing their delivery into the blood.
Collapse
|
4
|
Abstract
The Golgi apparatus has intrigued researchers since its discovery and despite the advances, there are still many open questions in regards to its shape and function. We propose a mechanical model of Golgi apparatus stack and explain its most elementary geometrical properties: the equilibrium number of cisternae, the stack size, and its general equilibrium shape. Combining both analytical and numerical methods we successfully reconstruct the stack morphology within the theory of bending elasticity. We demonstrate that energy-wise the stack prefers an overall bent shape and show strong evidence that the adhesion strength determines the equilibrium number of cisternae per stack. We explore the morphological role of fenestrations and discuss their impact on the overall stack structure. We also comment on the effects of the asymmetry in the composition of membrane leaflets on the shape of the cisternae and thus offer a broad steady-state study of the stack morphology and present a method that can be used also for other membrane-bound organelles.
Collapse
Affiliation(s)
- U Jelerčič
- Department of Theoretical Physics, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia. Current affiliation: Department of Chemical Engineering and Ilse Kats Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| |
Collapse
|
5
|
Tachikawa M, Mochizuki A. Golgi apparatus self-organizes into the characteristic shape via postmitotic reassembly dynamics. Proc Natl Acad Sci U S A 2017; 114:5177-5182. [PMID: 28461510 PMCID: PMC5441826 DOI: 10.1073/pnas.1619264114] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The Golgi apparatus is a membrane-bounded organelle with the characteristic shape of a series of stacked flat cisternae. During mitosis in mammalian cells, the Golgi apparatus is once fragmented into small vesicles and then reassembled to form the characteristic shape again in each daughter cell. The mechanism and details of the reassembly process remain elusive. Here, by the physical simulation of a coarse-grained membrane model, we reconstructed the three-dimensional morphological dynamics of the Golgi reassembly process. Considering the stability of the interphase Golgi shape, we introduce two hypothetical mechanisms-the Golgi rim stabilizer protein and curvature-dependent restriction on membrane fusion-into the general biomembrane model. We show that the characteristic Golgi shape is spontaneously organized from the assembly of vesicles by proper tuning of the two additional mechanisms, i.e., the Golgi reassembly process is modeled as self-organization. We also demonstrate that the fine Golgi shape forms via a balance of three reaction speeds: vesicle aggregation, membrane fusion, and shape relaxation. Moreover, the membrane fusion activity decreases thickness and the number of stacked cisternae of the emerging shapes.
Collapse
Affiliation(s)
- Masashi Tachikawa
- Theoretical Biology Laboratory, RIKEN, Wako 351-0198, Japan;
- Interdisciplinary Theoretical Science Research Group, RIKEN, Wako 351-0198, Japan
| | - Atsushi Mochizuki
- Theoretical Biology Laboratory, RIKEN, Wako 351-0198, Japan
- Interdisciplinary Theoretical Science Research Group, RIKEN, Wako 351-0198, Japan
- Core Research for Evolutionary Science and Technology, Japan Science and Technology Agency, Kawaguchi 332-0012, Japan
- Interdisciplinary Theoretical and Mathematical Science Program, RIKEN, Wako 351-0198, Japan
| |
Collapse
|
6
|
Campelo F, van Galen J, Turacchio G, Parashuraman S, Kozlov MM, García-Parajo MF, Malhotra V. Sphingomyelin metabolism controls the shape and function of the Golgi cisternae. eLife 2017; 6. [PMID: 28500756 PMCID: PMC5462544 DOI: 10.7554/elife.24603] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Accepted: 05/04/2017] [Indexed: 12/11/2022] Open
Abstract
The flat Golgi cisterna is a highly conserved feature of eukaryotic cells, but how is this morphology achieved and is it related to its function in cargo sorting and export? A physical model of cisterna morphology led us to propose that sphingomyelin (SM) metabolism at the trans-Golgi membranes in mammalian cells essentially controls the structural features of a Golgi cisterna by regulating its association to curvature-generating proteins. An experimental test of this hypothesis revealed that affecting SM homeostasis converted flat cisternae into highly curled membranes with a concomitant dissociation of membrane curvature-generating proteins. These data lend support to our hypothesis that SM metabolism controls the structural organization of a Golgi cisterna. Together with our previously presented role of SM in controlling the location of proteins involved in glycosylation and vesicle formation, our data reveal the significance of SM metabolism in the structural organization and function of Golgi cisternae. DOI:http://dx.doi.org/10.7554/eLife.24603.001 The Golgi complex is a hub inside cells that transports many proteins to various parts of the cell. It also receives freshly made proteins and modifies them to help them mature into their final active forms. The complex is made up of a stack of disc-like membrane structures called cisternae. Are the shapes of the cisternae important for the Golgi complex to work properly? Membranes are made of mixtures of molecules known as lipids and proteins. Previous experiments show that when the mixture of lipids in the Golgi membranes changes in a specific manner, the cisternae curl into an onion-like shape and the Golgi cannot process or send out proteins anymore. Campelo et al. used mathematics and experimental approaches to investigate what causes the Golgi to change shape when the lipid mixture of the cisternae changes. A mathematical description of the shape of the Golgi predicted that some proteins keep the cisternae flat by holding the membrane rim that connects the two faces of a cisterna. To test this prediction, Campelo et al. performed experiments in human cells, which showed that when the mixture of lipids in the Golgi membranes changes, certain proteins jump from the rim, causing the cisternae to curl. These same proteins are also needed to transport cargo proteins out of the Golgi, meaning that there is a connection between the shape of the Golgi and the tasks it carries out. The shape of the Golgi complex is altered in Alzheimer’s disease and many other neurodegenerative diseases. The next challenges are to understand how these shape changes happen, how this affects cells, and if it could be possible to develop drugs that prevent these changes from occurring in patients. DOI:http://dx.doi.org/10.7554/eLife.24603.002
Collapse
Affiliation(s)
- Felix Campelo
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Josse van Galen
- Centre for Genomic Regulation, The Barcelona Institute of Science and Technology, Barcelona, Spain.,Universitat Pompeu Fabra, Barcelona, Spain
| | - Gabriele Turacchio
- Institute of Protein Biochemistry, National Research Council of Italy, Naples, Italy
| | | | - Michael M Kozlov
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - María F García-Parajo
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Barcelona, Spain.,Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain
| | - Vivek Malhotra
- Centre for Genomic Regulation, The Barcelona Institute of Science and Technology, Barcelona, Spain.,Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain.,Universitat Pompeu Fabra, Barcelona, Spain
| |
Collapse
|
7
|
Different Golgi ultrastructure across species and tissues: Implications under functional and pathological conditions, and an attempt at classification. Tissue Cell 2017; 49:186-201. [DOI: 10.1016/j.tice.2016.12.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2016] [Revised: 12/05/2016] [Accepted: 12/05/2016] [Indexed: 02/08/2023]
|
8
|
Beznoussenko GV, Pilyugin SS, Geerts WJC, Kozlov MM, Burger KNJ, Luini A, Derganc J, Mironov AA. Trans-membrane area asymmetry controls the shape of cellular organelles. Int J Mol Sci 2015; 16:5299-333. [PMID: 25761238 PMCID: PMC4394477 DOI: 10.3390/ijms16035299] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Revised: 02/04/2015] [Accepted: 02/13/2015] [Indexed: 01/08/2023] Open
Abstract
Membrane organelles often have complicated shapes and differ in their volume, surface area and membrane curvature. The ratio between the surface area of the cytosolic and luminal leaflets (trans-membrane area asymmetry (TAA)) determines the membrane curvature within different sites of the organelle. Thus, the shape of the organelle could be critically dependent on TAA. Here, using mathematical modeling and stereological measurements of TAA during fast transformation of organelle shapes, we present evidence that suggests that when organelle volume and surface area are constant, TAA can regulate transformation of the shape of the Golgi apparatus, endosomal multivesicular bodies, and microvilli of brush borders of kidney epithelial cells. Extraction of membrane curvature by small spheres, such as COPI-dependent vesicles within the Golgi (extraction of positive curvature), or by intraluminal vesicles within endosomes (extraction of negative curvature) controls the shape of these organelles. For instance, Golgi tubulation is critically dependent on the fusion of COPI vesicles with Golgi cisternae, and vice versa, for the extraction of membrane curvature into 50–60 nm vesicles, to induce transformation of Golgi tubules into cisternae. Also, formation of intraluminal ultra-small vesicles after fusion of endosomes allows equilibration of their TAA, volume and surface area. Finally, when microvilli of the brush border are broken into vesicles and microvilli fragments, TAA of these membranes remains the same as TAA of the microvilli. Thus, TAA has a significant role in transformation of organelle shape when other factors remain constant.
Collapse
Affiliation(s)
- Galina V Beznoussenko
- The FIRC Institute of Molecular Oncology, Milan 20139, Italy.
- Consorzio Mario Negri Sud, S. Maria Imbaro, Chieti 66030, Italy.
| | - Sergei S Pilyugin
- Department of Mathematics, University of Florida, Gainesville, FL 32611-8105, USA.
| | - Willie J C Geerts
- Department of Biochemical Physiology, Institute of Biomembranes, 3584 CH Utrecht, The Netherlands.
| | - Michael M Kozlov
- Department of Physiology and Pharmacology, Tel Aviv University, Tel Aviv 69978, Israel.
| | - Koert N J Burger
- Department of Biochemical Physiology, Institute of Biomembranes, 3584 CH Utrecht, The Netherlands.
| | - Alberto Luini
- Consiglio Nazionale delle Ricerche (CNR), Istituto di Biochimica delle Proteine, Naples 80131, Italy.
| | - Jure Derganc
- Institute of Biophysics, University of Ljubljana, 1000 Ljubljana, Slovenia.
| | - Alexander A Mironov
- The FIRC Institute of Molecular Oncology, Milan 20139, Italy.
- Consorzio Mario Negri Sud, S. Maria Imbaro, Chieti 66030, Italy.
| |
Collapse
|
9
|
Abstract
In mammalian cells, the Golgi complex has an elaborate structure consisting of stacked, flattened cisternal membranes collected into a ribbon in the center of the cell. Amazingly, the flattened cisternae can rapidly dilate to accommodate large cargo as it traffics through the organelle. The mechanism by which this occurs is unknown. Exocytosis of large cargo is essential for many physiological processes, including collagen and lipoprotein secretion, and defects in the process lead to disease. In addition, enveloped viruses that bud into the endoplasmic reticulum or Golgi complex must also be transported through Golgi cisternae for secretion from the infected cell. This review summarizes our understanding of intra-Golgi transport of large cargo, and outlines current questions open for experimentation.
Collapse
Affiliation(s)
- Carolyn E Machamer
- Department of Cell Biology, Johns Hopkins University School of Medicine, 725 N. Wolfe St., Baltimore, MD 20205, USA.
| |
Collapse
|
10
|
Esteban-Pretel G, Marín MP, Romero AM, Timoneda J, Ponsoda X, Ballestín R, Renau-Piqueras J. Polyphosphoinositide metabolism and Golgi complex morphology in hippocampal neurons in primary culture is altered by chronic ethanol exposure. Alcohol Alcohol 2012; 48:15-27. [PMID: 23118092 DOI: 10.1093/alcalc/ags117] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
AIMS Ethanol affects not only the cytoskeletal organization and activity, but also intracellular trafficking in neurons in the primary culture. Polyphosphoinositide (PPIn) are essential regulators of many important cell functions, including those mentioned, cytoskeleton integrity and intracellular vesicle trafficking. Since information about the effect of chronic ethanol exposure on PPIn metabolism in neurons is scarce, this study analysed the effect of this treatment on three of these phospholipids. METHODS Phosphatidylinositol (PtdIns) levels as well as the activity and/or levels of enzymes involved in their metabolism were analysed in neurons chronically exposed to ethanol. The levels of phospholipases C and D, and phosphatidylethanol formation were also assessed. The consequence of the possible alterations in the levels of PtdIns on the Golgi complex (GC) was also analysed. RESULTS We show that phosphatidylinositol (4,5)-bisphosphate and phosphatidylinositol (3,4,5)-trisphosphate levels, both involved in the control of intracellular trafficking and cytoskeleton organization, decrease in ethanol-exposed hippocampal neurons. In contrast, several kinases that participate in the metabolism of these phospholipids, and the level and/or activity of phospholipases C and D, increase in cells after ethanol exposure. Ethanol also promotes phosphatidylethanol formation in neurons, which can result in the suppression of phosphatidic acid synthesis and, therefore, in PPIn biosynthesis. This treatment also lowers the phosphatidylinositol 4-phosphate levels, the main PPIn in the GC, with alterations in their morphology and in the levels of some of the proteins involved in structure maintenance. CONCLUSIONS The deregulation of the metabolism of PtdIns may underlie the ethanol-induced alterations on different neuronal processes, including intracellular trafficking and cytoskeletal integrity.
Collapse
Affiliation(s)
- Guillermo Esteban-Pretel
- Corresponding author: Sección de Biología y Patología Celular, Centro de Investigación, Hospital Universitario La Fe, Avda. Campanar 21, Valencia, Spain.
| | | | | | | | | | | | | |
Collapse
|
11
|
Shapes of discoid intracellular compartments with small relative volumes. PLoS One 2011; 6:e26824. [PMID: 22132079 PMCID: PMC3221666 DOI: 10.1371/journal.pone.0026824] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Accepted: 10/03/2011] [Indexed: 02/03/2023] Open
Abstract
A prominent feature of many intracellular compartments is a large membrane surface area relative to their luminal volume, i.e., the small relative volume. In this study we present a theoretical analysis of discoid membrane compartments with a small relative volume and then compare the theoretical results to quantitative morphological assessment of fusiform vesicles in urinary bladder umbrella cells. Specifically, we employ three established extensions of the standard approach to lipid membrane shape calculation and determine the shapes that could be expected according to three scenarios of membrane shaping: membrane adhesion in the central discoid part, curvature driven lateral segregation of membrane constituents, and existence of stiffer membrane regions, e.g., support by protein scaffolds. The main characteristics of each scenario are analyzed. The results indicate that even though all three scenarios can lead to similar shapes, there are values of model parameters that yield qualitatively distinctive shapes. Consequently, a distinctive shape of an intracellular compartment may reveal its membrane shaping mechanism and the membrane structure. The observed shapes of fusiform vesicles fall into two qualitatively different classes, yet they are all consistent with the theoretical results and the current understanding of their structure and function.
Collapse
|
12
|
Affiliation(s)
| | - Adam D. Linstedt
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15232;
| |
Collapse
|
13
|
Derganc J. Curvature-driven lateral segregation of membrane constituents in Golgi cisternae. Phys Biol 2007; 4:317-24. [DOI: 10.1088/1478-3975/4/4/008] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
14
|
Jiang H, Huber G, Pelcovits RA, Powers TR. Vesicle shape, molecular tilt, and the suppression of necks. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 76:031908. [PMID: 17930272 DOI: 10.1103/physreve.76.031908] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2007] [Indexed: 05/25/2023]
Abstract
Can the presence of molecular-tilt order significantly affect the shapes of lipid bilayer membranes, particularly membrane shapes with narrow necks? Motivated by the propensity for tilt order and the common occurrence of narrow necks in the intermediate stages of biological processes such as endocytosis and vesicle trafficking, we examine how tilt order inhibits the formation of necks in the equilibrium shapes of vesicles. For vesicles with a spherical topology, point defects in the molecular order with a total strength of +2 are required. We study axisymmetric shapes and suppose that there is a unit-strength defect at each pole of the vesicle. The model is further simplified by the assumption of tilt isotropy: invariance of the energy with respect to rotations of the molecules about the local membrane normal. This isotropy condition leads to a minimal coupling of tilt order and curvature, giving a high energetic cost to regions with Gaussian curvature and tilt order. Minimizing the elastic free energy with constraints of fixed area and fixed enclosed volume determines the allowed shapes. Using numerical calculations, we find several branches of solutions and identify them with the branches previously known for fluid membranes. We find that tilt order changes the relative energy of the branches, suppressing thin necks by making them costly, leading to elongated prolate vesicles as a generic family of tilt-ordered membrane shapes.
Collapse
Affiliation(s)
- Hongyuan Jiang
- Division of Engineering, Box D, Brown University, Providence, Rhode Island 02912, USA
| | | | | | | |
Collapse
|