Ignicoccus hospitalis and Nanoarchaeum equitans: ultrastructure, cell–cell interaction, and 3D reconstruction from serial sections of freeze-substituted cells and by electron cryotomography

Ultrastructure and intercellular interaction of Ignicoccus hospitalis and Nanoarchaeum equitans were investigated using two different electron microscopy approaches, by three-dimensional reconstructions from serial sections, and by electron cryotomography. Serial sections were assembled into 3D reconstructions, for visualizing the unusual complexity of I. hospitalis, its huge periplasmic space, the vesiculating cytoplasmic membrane, and the outer membrane. The cytoplasm contains fibres which are reminiscent to a cytoskeleton. Cell division in I. hospitalis is complex, and different to that in Euryarchaeota or Bacteria. An irregular invagination of the cytoplasmic membrane is followed by separation of the two cytoplasms. Simultaneous constriction of cytoplasmic plus outer membrane is not observed. Cells of N. equitans show a classical mode of cell division, by constriction in the mid-plane. Their cytoplasm exhibits two types of fibres, elongated and ring-shaped. Electron micrographs of contact sites between I. hospitalis and N. equitans exhibit two modes of interaction. One is indirect and mediated by thin fibres; in other cells the two cell surfaces are in direct contact. The two membranes of I. hospitalis cells are frequently seen in direct contact, possibly a prerequisite for transporting metabolites or substrates from the cytoplasm of one cell to the other. Rarely, a transport based on cargo vesicles is observed between I. hospitalis and N. equitans

A Method for Efficient Calculation of Diffusion and Reactions of Lipophilic Compounds in Complex Cell Geometry

A general description of effects of toxic compounds in mammalian cells is facing several problems. Firstly, most toxic compounds are hydrophobic and partition phenomena strongly influence their behaviour. Secondly, cells display considerable heterogeneity regarding the presence, activity and distribution of enzymes participating in the metabolism of foreign compounds i.e. bioactivation/biotransformation. Thirdly, cellular architecture varies greatly. Taken together, complexity at several levels has to be addressed to arrive at efficient in silico modelling based on physicochemical properties, metabolic preferences and cell characteristics. In order to understand the cellular behaviour of toxic foreign compounds we have developed a mathematical model that addresses these issues. In order to make the system numerically treatable, methods motivated by homogenization techniques have been applied. These tools reduce the complexity of mathematical models of cell dynamics considerably thus allowing to solve efficiently the partial differential equations in the model numerically on a personal computer. Compared to a compartment model with well-stirred compartments, our model affords a more realistic representation. Numerical results concerning metabolism and chemical solvolysis of a polycyclic aromatic hydrocarbon carcinogen show good agreement with results from measurements in V79 cell culture. The model can easily be extended and refined to include more reactants, and/or more complex reaction chains, enzyme distribution etc, and is therefore suitable for modelling cellular metabolism involving membrane partitioning also at higher levels of complexity

Report on ISCTM consensus meeting on clinical assessment of response to treatment of cognitive impairment in schizophrenia

Funding for this manuscript was provided by the International Society for CNS Clinical Trials and Methodology.Dr Keefe currently or in the past 3 years has received investigator-initiated research funding support from the Department of Veteran's Affair, Feinstein Institute for Medical Research, GlaxoSmithKline, National Institute of Mental Health, Novartis, Psychogenics, Research Foundation for Mental Hygiene, Inc., and the Singapore National Medical Research Council. He currently or in the past 3 years has received honoraria, served as a consultant, or advisory board member for Abbvie, Akebia, Amgen, Asubio, AviNeuro/ChemRar, BiolineRx, Biogen Idec, Biomarin, Boehringer-Ingelheim, Eli Lilly, EnVivo/FORUM, GW Pharmaceuticals, Janssen, Lundbeck, Merck, Minerva Neurosciences, Inc., Mitsubishi, Novartis, NY State Office of Mental Health, Otsuka, Pfizer, Reviva, Roche, Sanofi/Aventis, Shire, Sunovion, Takeda, Targacept, and the University of Texas South West Medical Center. Dr Keefe receives royalties from the BACS testing battery, the MATRICS battery (BACS Symbol Coding), and the Virtual Reality Functional Capacity Assessment Tool. He is also a shareholder in NeuroCog Trials, Inc. and Sengenix. Dr Haig is a full-time employee of Abbvie. Dr Marder has received consulting fees from Abbvie, Genentech, Roche, Lundbeck, Pfizer, Otsuka, Takeda, and Boeringer Ingelheim. He has received research support from Amgen, Sunovion, and Synchroneuron. Dr Harvey has received consulting fees from Abbvie, Boehringer Ingelheim, Forest Labs, Forum Pharma, Genentech, Otsuka America, Roche Pharma, Sunovion Pharma, and Takeda Pharma during the past year. He also received contract research support from Genentech. Dr Dunayevich for the past 3 years has been a full-time employee and stockholder of Amgen. Dr Medalia in the past 3 years has received research funding support from Sunovion. Dr Medalia has also currently or in the past 3 years received honoraria or served as consultant for Dainippon Sumitomo Pharma Co., Ltd., Otsuka, and Takeda Pharmaceuticals U.S.A., Inc. Dr Davidson has received research grant support and/or travel support and/or speaker fees and/or consultancy fees from Lundbeck, Eli Lilly, Servier, Abbott, Minerva and holds stocks in CTR and BiolineRx. Dr Lombardo is a full-time employee of FORUM Pharmaceuticals. Dr Bowie reports receiving grant support from Pfizer. He has also been a consultant for Lundbeck, Otsuka, Abbvie, and Takeda. Dr Buchanan reports: Advisory Board: Abbvie, Amgen, EnVivo, Roche; Consultant: Abbvie, Amgen, Bristol Myers Squibb, EnVivo, Omeros; DSMB member: Pfizer. Dr Bugarski -Kirola is a full-time employee of Hoffmann-La Roche Ltd. Dr Carpenter in the past 2 years has been a consultant to Roche/Genetech. Dr Dago in the last 3 years has received honoraria from Lundbeck, Forest Pharmaceuticals, Otsuka, Pam Labs, and Astra Zeneca for lectures given in promotion of their psychotropic medications. Dr Durand in the past year has been a consultant and received honoraria from Teva Pharmaceuticals. Dr Gold receives royalty payments from the BACS. He also has served as a consultant for Amgen, Hoffman LaRoche, and Lundbeck. Dr Hooker has served as a consultant and is currently a Co-Investigator on an NIH SBIR grant with PositScience Corporation. Dr Loebel is an employee of Sunovion Pharmaceuticals. Dr McGurk reports receiving consulting fees from Abbvie and EnVivo Pharmaceuticals. Dr Pinkham in the past year has received consulting fees from Otsuka America Pharmaceutical, Inc.The following authors have declared that there are no conflicts of interest in relation to the subject of this study: Drs Csernansky, Frese, Goff, Kopelowic, Opler, and Stern. (International Society for CNS Clinical Trials and Methodology; Department of Veteran's Affair; Feinstein Institute for Medical Research; GlaxoSmithKline; National Institute of Mental Health; Novartis; Psychogenics; Research Foundation for Mental Hygiene, Inc.; Singapore National Medical Research Council; Abbvie; Genentech; Roche; Lundbeck; Pfizer; Otsuka; Takeda; Boeringer Ingelheim; Amgen; Sunovion; Synchroneuron; Boehringer Ingelheim; Forest Labs; Forum Pharma; Otsuka America; Roche Pharma; Sunovion Pharma; Takeda Pharma; Eli Lilly; Servier; Abbott; Minerva; BACS; EnVivo Pharmaceuticals; Otsuka America Pharmaceutical, Inc.)Published versio

Characterization of the Endothelial Cell Cytoskeleton following HLA Class I Ligation

Vascular endothelial cells (ECs) are a target of antibody-mediated allograft rejection. In vitro, when the HLA class I molecules on the surface of ECs are ligated by anti-HLA class I antibodies, cell proliferation and survival pathways are activated and this is thought to contribute to the development of antibody-mediated rejection. Crosslinking of HLA class I molecules by anti-HLA antibodies also triggers reorganization of the cytoskeleton, which induces the formation of F-actin stress fibers. HLA class I induced stress fiber formation is not well understood.The present study examines the protein composition of the cytoskeleton fraction of ECs treated with HLA class I antibodies and compares it to other agonists known to induce alterations of the cytoskeleton in endothelial cells. Analysis by tandem mass spectrometry revealed unique cytoskeleton proteomes for each treatment group. Using annotation tools a candidate list was created that revealed 12 proteins, which were unique to the HLA class I stimulated group. Eleven of the candidate proteins were phosphoproteins and exploration of their predicted kinases provided clues as to how these proteins may contribute to the understanding of HLA class I induced antibody-mediated rejection. Three of the candidates, eukaryotic initiation factor 4A1 (eIF4A1), Tropomyosin alpha 4-chain (TPM4) and DDX3X, were further characterized by Western blot and found to be associated with the cytoskeleton. Confocal microscopy analysis showed that class I ligation stimulated increased eIF4A1 co-localization with F-actin and paxillin.Colocalization of eIF4A1 with F-actin and paxillin following HLA class I ligation suggests that this candidate protein could be a target for understanding the mechanism(s) of class I mediated antibody-mediated rejection. This proteomic approach for analyzing the cytoskeleton of ECs can be applied to other agonists and various cells types as a method for uncovering novel regulators of cytoskeleton changes

Whole Cell Cryo-Electron Tomography Reveals Distinct Disassembly Intermediates of Vaccinia Virus

At each round of infection, viruses fall apart to release their genome for replication, and then reassemble into stable particles within the same host cell. For most viruses, the structural details that underlie these disassembly and assembly reactions are poorly understood. Cryo-electron tomography (cryo-ET), a unique method to investigate large and asymmetric structures at the near molecular resolution, was previously used to study the complex structure of vaccinia virus (VV). Here we study the disassembly of VV by cryo-ET on intact, rapidly frozen, mammalian cells, infected for up to 60 minutes. Binding to the cell surface induced distinct structural rearrangements of the core, such as a shape change, the rearrangement of its surface spikes and de-condensation of the viral DNA. We propose that the cell surface induced changes, in particular the decondensation of the viral genome, are a prerequisite for the subsequent release of the vaccinia DNA into the cytoplasm, which is followed by its cytoplasmic replication. Generally, this is the first study that employs whole cell cryo-ET to address structural details of pathogen-host cell interaction

Arabidopsis Plasmodesmal Proteome

The multicellular nature of plants requires that cells should communicate in order to coordinate essential functions. This is achieved in part by molecular flux through pores in the cell wall, called plasmodesmata. We describe the proteomic analysis of plasmodesmata purified from the walls of Arabidopsis suspension cells. Isolated plasmodesmata were seen as membrane-rich structures largely devoid of immunoreactive markers for the plasma membrane, endoplasmic reticulum and cytoplasmic components. Using nano-liquid chromatography and an Orbitrap ion-trap tandem mass spectrometer, 1341 proteins were identified. We refer to this list as the plasmodesmata- or PD-proteome. Relative to other cell wall proteomes, the PD-proteome is depleted in wall proteins and enriched for membrane proteins, but still has a significant number (35%) of putative cytoplasmic contaminants, probably reflecting the sensitivity of the proteomic detection system. To validate the PD-proteome we searched for known plasmodesmal proteins and used molecular and cell biological techniques to identify novel putative plasmodesmal proteins from a small subset of candidates. The PD-proteome contained known plasmodesmal proteins and some inferred plasmodesmal proteins, based upon sequence or functional homology with examples identified in different plant systems. Many of these had a membrane association reflecting the membranous nature of isolated structures. Exploiting this connection we analysed a sample of the abundant receptor-like class of membrane proteins and a small random selection of other membrane proteins for their ability to target plasmodesmata as fluorescently-tagged fusion proteins. From 15 candidates we identified three receptor-like kinases, a tetraspanin and a protein of unknown function as novel potential plasmodesmal proteins. Together with published work, these data suggest that the membranous elements in plasmodesmata may be rich in receptor-like functions, and they validate the content of the PD-proteome as a valuable resource for the further uncovering of the structure and function of plasmodesmata as key components in cell-to-cell communication in plants

From lamins to lamina: a structural perspective

Lamin proteins are the major constituents of the nuclear lamina, a proteinaceous network that lines the inner nuclear membrane. Primarily, the nuclear lamina provides structural support for the nucleus and the nuclear envelope; however, lamins and their associated proteins are also involved in most of the nuclear processes, including DNA replication and repair, regulation of gene expression, and signaling. Mutations in human lamin A and associated proteins were found to cause a large number of diseases, termed 'laminopathies.' These diseases include muscular dystrophies, lipodystrophies, neuropathies, and premature aging syndromes. Despite the growing number of studies on lamins and their associated proteins, the molecular organization of lamins in health and disease is still elusive. Likewise, there is no comprehensive view how mutations in lamins result in a plethora of diseases, selectively affecting different tissues. Here, we discuss some of the structural aspects of lamins and the nuclear lamina organization, in light of recent results