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Caetano FA, Dirk BS, Tam JHK, Cavanagh PC, Goiko M, Ferguson SSG, Pasternak SH, Dikeakos JD, de Bruyn JR, Heit B. MIiSR: Molecular Interactions in Super-Resolution Imaging Enables the Analysis of Protein Interactions, Dynamics and Formation of Multi-protein Structures. PLoS Comput Biol 2015; 11:e1004634. [PMID: 26657340 PMCID: PMC4676698 DOI: 10.1371/journal.pcbi.1004634] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Accepted: 10/27/2015] [Indexed: 11/18/2022] Open
Abstract
Our current understanding of the molecular mechanisms which regulate cellular processes such as vesicular trafficking has been enabled by conventional biochemical and microscopy techniques. However, these methods often obscure the heterogeneity of the cellular environment, thus precluding a quantitative assessment of the molecular interactions regulating these processes. Herein, we present Molecular Interactions in Super Resolution (MIiSR) software which provides quantitative analysis tools for use with super-resolution images. MIiSR combines multiple tools for analyzing intermolecular interactions, molecular clustering and image segmentation. These tools enable quantification, in the native environment of the cell, of molecular interactions and the formation of higher-order molecular complexes. The capabilities and limitations of these analytical tools are demonstrated using both modeled data and examples derived from the vesicular trafficking system, thereby providing an established and validated experimental workflow capable of quantitatively assessing molecular interactions and molecular complex formation within the heterogeneous environment of the cell. In this paper we present the software package Molecular Interactions in Super Resolution (MIiSR), which provides a series of quantitative analytical tools for measuring molecular interactions and the formation of higher-order molecular complexes in super-resolution microscopy images.
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Affiliation(s)
- Fabiana A. Caetano
- The J. Allyn Taylor Centre for Cell Biology, Robarts Research Institute and the Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada
| | - Brennan S. Dirk
- Department of Microbiology and Immunology, The University of Western Ontario, London, Ontario, Canada
| | - Joshua H. K. Tam
- The J. Allyn Taylor Centre for Cell Biology, Robarts Research Institute and the Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada
| | - P. Craig Cavanagh
- Department of Microbiology and Immunology, The University of Western Ontario, London, Ontario, Canada
| | - Maria Goiko
- Department of Microbiology and Immunology, The University of Western Ontario, London, Ontario, Canada
- Department of Physics and Astronomy, The University of Western Ontario, London, Ontario, Canada
| | | | - Stephen H. Pasternak
- The J. Allyn Taylor Centre for Cell Biology, Robarts Research Institute and the Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada
- Department of Clinical Neurological Sciences, Schulich School of Medicine, The University of Western Ontario, London, Ontario, Canada
| | - Jimmy D. Dikeakos
- Department of Microbiology and Immunology, The University of Western Ontario, London, Ontario, Canada
| | - John R. de Bruyn
- Department of Physics and Astronomy, The University of Western Ontario, London, Ontario, Canada
| | - Bryan Heit
- Department of Microbiology and Immunology, The University of Western Ontario, London, Ontario, Canada
- * E-mail:
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Wu M, De Camilli P. Supported native plasma membranes as platforms for the reconstitution and visualization of endocytic membrane budding. Methods Cell Biol 2012; 108:3-18. [PMID: 22325595 DOI: 10.1016/b978-0-12-386487-1.00001-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Cell-free assays represent an important complement to studies in living cells for the elucidation of mechanisms underlying the dynamics of biological membranes, such as budding, fission, and fusion reactions. Here we describe a method for the reconstitution of endocytosis, the process through which cells internalize portions of the plasma membrane along with extracellular material, under conditions that allow the visualization of individual budding events with high spatial and temporal resolution. The method, which is based on the generation of planar plasma membrane sheets attached to a glass substrate and their subsequent incubation with a cytosolic extract, results in a very robust formation of endocytic buds, which upon appropriate conditions undergo fission. The synchronization of the endocytic events and the accessibility of the material to a variety of manipulations make this experimental system a powerful tool for the molecular dissection of endocytosis.
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Affiliation(s)
- Min Wu
- Howard Hughes Medical Institute, Department of Cell Biology, Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06520, USA
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Ay N, Irmler K, Fischer A, Uhlemann R, Reuter G, Humbeck K. Epigenetic programming via histone methylation at WRKY53 controls leaf senescence in Arabidopsis thaliana. Traffic 2009; 58:333-46. [PMID: 19143996 DOI: 10.1111/j.1365-313x.2008.03782.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/25/2023]
Abstract
Leaf senescence, the final step of leaf development, involves extensive reprogramming of gene expression. Here, we show that these processes include discrete changes of epigenetic indexing, as well as global alterations in chromatin organization. During leaf senescence, the interphase nuclei show a decondensation of chromocenter heterochromatin, and changes in the nuclear distribution of the H3K4me2, H3K4me3, and the H3K27me2 and H3K27me3 histone modification marks that index active and inactive chromatin, respectively. Locus-specific epigenetic indexing was studied at the WRKY53 key regulator of leaf senescence. During senescence, when the locus becomes activated, H3K4me2 and H3K4me3 are significantly increased at the 5' end and at coding regions. Impairment of these processes is observed in plants overexpressing the SUVH2 histone methyltransferase, which causes ectopic heterochromatization. In these plants the transcriptional initiation of WRKY53 and of the senescence-associated genes SIRK, SAG101, ANAC083, SAG12 and SAG24 is inhibited, resulting in a delay of leaf senescence. In SUVH2 overexpression plants, significant levels of H3K27me2 and H3K27me3 are detected at the 5'-end region of WRKY53, resulting in its transcriptional repression. Furthermore, SUVH2 overexpression inhibits senescence-associated global changes in chromatin organization. Our data suggest that complex epigenetic processes control the senescence-specific gene expression pattern.
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Affiliation(s)
- Nicole Ay
- Department of Plant Physiology, Institute of Biology, Martin-Luther University Halle-Wittenberg, Weinbergweg 10, D-06120 Halle, Germany
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Sekimoto K, Triller A. Compatibility between itinerant synaptic receptors and stable postsynaptic structure. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 79:031905. [PMID: 19391969 DOI: 10.1103/physreve.79.031905] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2008] [Revised: 01/13/2009] [Indexed: 05/27/2023]
Abstract
The density of synaptic receptors in front of presynaptic release sites is stabilized in the presence of scaffold proteins, but the receptors and scaffold molecules have local exchanges with characteristic times shorter than that of the receptor-scaffold assembly. We propose a mesoscopic model to account for the regulation of the local density of receptors as quasiequilibrium. It is based on two zones (synaptic and extrasynaptic) and multilayer (membrane, submembrane, and cytoplasmic) topological organization. The model includes the balance of chemical potentials associated with the receptor and scaffold protein concentrations in the various compartments. The model shows highly cooperative behavior including a "phase change" resulting in the formation of well-defined postsynaptic domains. This study provides theoretical tools to approach the complex issue of synaptic stability at the synapse, where receptors are transiently trapped yet rapidly diffuse laterally on the plasma membrane.
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Affiliation(s)
- Ken Sekimoto
- Laboratoire Matières et Systèmes Complexes, Université Paris Diderot and CNRS-UMR 7057, 10 rue Alice Domont et Léonie Duquet, 75013 Paris, France
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Abstract
The plasma membrane is the interface between cells and their harsh environment. Uptake of nutrients and all communication among cells and between cells and their environment occurs through this interface. 'Endocytosis' encompasses several diverse mechanisms by which cells internalize macromolecules and particles into transport vesicles derived from the plasma membrane. It controls entry into the cell and has a crucial role in development, the immune response, neurotransmission, intercellular communication, signal transduction, and cellular and organismal homeostasis. As the complexity of molecular interactions governing endocytosis are revealed, it has become increasingly clear that it is tightly coordinated and coupled with overall cell physiology and thus, must be viewed in a broader context than simple vesicular trafficking.
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Affiliation(s)
- Sean D Conner
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California 92037, USA
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Abstract
Members of the dynamin family of GTPases have unique structural properties that might reveal a general mechanochemical basis for membrane constriction. Receptor-mediated endocytosis, caveolae internalization and certain trafficking events in the Golgi all require dynamin for vesiculation. The dynamin-related protein Drp1 (Dlp1) has been implicated in mitochondria fission and a plant dynamin-like protein phragmoplastin is involved in the vesicular events leading to cell wall formation. A common theme among these proteins is their ability to self-assemble into spirals and their localization to areas of membrane fission. Here we present the first three-dimensional structure of dynamin at a resolution of approximately 20 A, determined from cryo-electron micrographs of tubular crystals in the constricted state. The map reveals a T-shaped dimer consisting of three prominent densities: leg, stalk and head. The structure suggests that the dense stalk and head regions rearrange when GTP is added, a rearrangement that generates a force on the underlying lipid bilayer and thereby leads to membrane constriction. These results indicate that dynamin is a force-generating 'contrictase'.
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Affiliation(s)
- P Zhang
- Laboratory of Cell Biochemistry and Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Building 8, Room 419, MSC 0851, 8 Center Drive, National Institutes of Health, Bethesda, Maryland 20892, USA
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Simpson F, Hussain NK, Qualmann B, Kelly RB, Kay BK, McPherson PS, Schmid SL. SH3-domain-containing proteins function at distinct steps in clathrin-coated vesicle formation. Nat Cell Biol 1999; 1:119-24. [PMID: 10559884 DOI: 10.1038/10091] [Citation(s) in RCA: 224] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Several SH3-domain-containing proteins have been implicated in endocytosis by virtue of their interactions with dynamin; however, their functions remain undefined. Here we report the efficient reconstitution of ATP-, GTP-, cytosol- and dynamin-dependent formation of clathrin-coated vesicles in permeabilized 3T3-L1 cells. The SH3 domains of intersectin, endophilin I, syndapin I and amphiphysin II inhibit coated-vesicle formation in vitro through interactions with membrane-associated proteins. Most of the SH3 domains tested selectively inhibit late events involving membrane fission, but the SH3A domain of intersectin uniquely inhibits intermediate events leading to the formation of constricted coated pits. These results suggest that interactions between SH3 domains and their partners function sequentially in endocytic coated-vesicle formation.
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Affiliation(s)
- F Simpson
- Department of Cell Biology, Scripps Research Institute, La Jolla, California 92037, USA
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Sever S, Muhlberg AB, Schmid SL. Impairment of dynamin's GAP domain stimulates receptor-mediated endocytosis. Nature 1999; 398:481-6. [PMID: 10206643 DOI: 10.1038/19024] [Citation(s) in RCA: 292] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Dynamin is a GTP-hydrolysing protein that is an essential participant in clathrin-mediated endocytosis by cells. It self-assembles into 'collars' in vitro which also formin vivo at the necks of invaginated coated pits. This self-assembly stimulates dynamin's GTPase activity and it has been proposed that dynamin hydrolyses GTP in order to generate the force needed to sever vesicles from the plasma membrane. A mechanism is now described in which self-assembly of dynamin is coordinated by a domain of dynamin with a GTPase-activating function. Unexpectedly, when dynamin mutants defective in self-assembly-stimulated GTPase activity are overexpressed, receptor-mediated endocytosis is accelerated. The results indicate that dynamin, like other members of the GTPase superfamily, functions as a molecular regulator in receptor-mediated endocytosis, rather than as a force-generating GTPase.
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Affiliation(s)
- S Sever
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California 92037, USA
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Gilbert A, Paccaud JP, Foti M, Porcheron G, Balz J, Carpentier JL. Direct demonstration of the endocytic function of caveolae by a cell-free assay. J Cell Sci 1999; 112 ( Pt 7):1101-10. [PMID: 10198292 DOI: 10.1242/jcs.112.7.1101] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The endocytic function of caveolae was challenged by taking advantage of a cell-free assay directly measuring the detachment of receptor-containing vesicles from isolated plasma membranes. Plasma membranes from cultured cells surface-labeled with 125I-cholera toxin (segregating in caveolae) were isolated as described previously. Following incubation of these labeled membranes in the presence of nucleotide(s) and cytosol, a significant proportion of the initially membrane-associated radioactivity was released into the incubation medium in sedimentable form (14*10(6)g). Results of biochemical, morphological, and fractionation analysis of the material containing the released radioactivity directly demonstrated that caveolae are plasma membrane domains involved in an endocytic process and resulting in the formation of caveolae-derived vesicles. In addition, these studies allowed a direct comparison of caveolae- and clathrin-coated pit-mediated endocytosis and reveal that these two processes diverge in terms of kinetics, cytosol and nucleotide requirements as well as in terms of the density and size of the endocytic vesicles formed.
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Affiliation(s)
- A Gilbert
- Department of Morphology, CMU, CH-1211 Geneva 4, Switzerland
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Flötenmeyer M, Momayezi M, Plattner H. Immunolabeling analysis of biosynthetic and degradative pathways of cell surface components (glycocalyx) in Paramecium cells. Eur J Cell Biol 1999; 78:67-77. [PMID: 10082425 DOI: 10.1016/s0171-9335(99)80008-9] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Biosynthetic and degradative pathways of glycocalyx components are largely unknown in Paramecium and in some related parasitic protozoa. We isolated cell surface (glyco-)proteins, i.e., surface antigens (SAg) and used them in the native (nSAg) or denatured (dSAg) state to produce antibodies (AB) for immunolocalization by confocal imaging and by quantitative immunogold EM-labeling of ultrathin sections or of freeze-fracture replicas. Antibodies against nSAg or dSAg, respectively, yield different labeling densities over individual structures, thus indicating biosynthetic or degradative pathways, respectively. We derive the following biosynthetic way: ER --> Golgi apparatus --> non-regulated/non-dense core vesicle transport --> diffusional spread over non-ciliary (somatic) and ciliary cell membrane. For degradation we show the following pathways: Concentration of nSAg in the cytostome --> nascent digestive vacuole --> mature vacuoles --> release of dSAg at cytoproct, with partial retrieval by "discoidal vesicles". A second internalization pathway proceeds via coated pits ("parasomal sacs") --> early endosomes ("terminal cisternae") --> digestive vacuoles. Dense packing of SAg in the glycocalyx may drive them into the endo-/phagocytic pathway. Still more intriguing is the site of nSAg integration into the cell membrane by unstimulated exocytosis. We consider unconspicuous clear vesicles relevant for nSAg export, probably via sites which most of the time are occupied by coated pits. This could compensate for membrane retrieval by coated pits, while scarcity of smooth profiles at these sites may be explained by the much longer time period required for coated pit formation as compared to exocytosis.
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