Subcellular organization of snRNPS in mammalian cells

1995 ◽  
Vol 53 ◽  
pp. 772-773
Author(s):  
A. Gregory Matera
Keyword(s):  
Rna Processing ◽  
Cell Biology ◽  
Mammalian Cells ◽  
Spatial Organization ◽  
Protein Complexes ◽  
Nuclear Architecture ◽  
Valuable Insight ◽  
Subcellular Organization ◽  
Protein Components ◽  
The Individual

Our laboratory is interested in aspects of eukaryotic gene expression that may be regulated at the level of nuclear architecture and/or localization. Understanding the spatial organization of genes and gene products within mammalian nuclei will provide valuable insight into how the various metabolic processes such as replication, transcription, processing and transport are orchestrated. In order to begin to address these questions, we have chosen to study the cell biology of RNA processing. Small RNA-protein complexes known as ribonucleoproteins (RNPs) are central factors in numerous RNA processing reactions. Much of what is currently known about the subcellular organization of RNPs is based upon the locations of the protein components of RNPs, not the RNA components. Furthermore, since many RNAs share common protein subunits it is essential to develop probes which are specific to the individual RNAs. We utilize highly specific antisense oligonucleotide probes and fluorescence in situ hybridization (FISH) to ascertain the organization of RNPs and their associations with particular subdomains within mammalian cells.

scholarly journals Nanoscale subcellular architecture revealed by multicolor 3D salvaged fluorescence imaging

2019 ◽  
Author(s):  
Yongdeng Zhang ◽  
Lena K. Schroeder ◽  
Mark D. Lessard ◽  
Phylicia Kidd ◽  
Jeeyun Chung ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Cell Biology ◽  
Mammalian Cells ◽  
Spatial Organization ◽  
Protein Complexes ◽  
Three Dimensional ◽  
Super Resolution ◽  
Membrane Structures ◽  
Molecular Specificity ◽  
20 Nm

AbstractCombining the molecular specificity of fluorescent probes with three-dimensional (3D) imaging at nanoscale resolution is critical for investigating the spatial organization and interactions of cellular organelles and protein complexes. We present a super-resolution light microscope that enables simultaneous multicolor imaging of whole mammalian cells at ~20 nm 3D resolution. We show its power for cell biology research with fluorescence images that resolved the highly convoluted Golgi apparatus and the close contacts between the endoplasmic reticulum and the plasma membrane, structures that have traditionally been the imaging realm of electron microscopy.One Sentence SummaryComplex cellular structures previously only resolved by electron microscopy can now be imaged in multiple colors by 4Pi-SMS.

Role of cryo-ET in membrane bioenergetics research

2013 ◽  
Vol 41 (5) ◽  
pp. 1227-1234 ◽  
Author(s):  
Karen M. Davies ◽  
Bertram Daum
Keyword(s):  
Spatial Organization ◽  
Electron Tomography ◽  
Protein Complexes ◽  
Mitochondrial Diseases ◽  
Atp Synthesis ◽  
Cellular Level ◽  
Molecular Organization ◽  
Cellular Context ◽  
Membrane Bound ◽  
The Individual

To truly understand bioenergetic processes such as ATP synthesis, membrane-bound substrate transport or flagellar rotation, systems need to be analysed in a cellular context. Cryo-ET (cryo-electron tomography) is an essential part of this process, as it is currently the only technique which can directly determine the spatial organization of proteins at the level of both the cell and the individual protein complexes. The need to assess bioenergetic processes at a cellular level is becoming more and more apparent with the increasing interest in mitochondrial diseases. In recent years, cryo-ET has contributed significantly to our understanding of the molecular organization of mitochondria and chloroplasts. The present mini-review first describes the technique of cryo-ET and then discusses its role in membrane bioenergetics specifically in chloroplasts and mitochondrial research.

scholarly journals Cell3: a new vision for study of the endomembrane system in mammalian cells

2021 ◽  
Vol 41 (12) ◽  
Author(s):  
Margaritha M. Mysior ◽  
Jeremy C. Simpson
Keyword(s):  
Membrane Trafficking ◽  
Cell Biology ◽  
Mammalian Cells ◽  
Cell Function ◽  
Cultured Cells ◽  
Membrane Traffic ◽  
Endomembrane System ◽  
Cellular Environment ◽  
New Vision ◽  
The Individual

Abstract The endomembrane system of mammalian cells provides massive capacity for the segregation of biochemical reactions into discrete locations. The individual organelles of the endomembrane system also require the ability to precisely transport material between these compartments in order to maintain cell homeostasis; this process is termed membrane traffic. For several decades, researchers have been systematically identifying and dissecting the molecular machinery that governs membrane trafficking pathways, with the overwhelming majority of these studies being carried out in cultured cells growing as monolayers. In recent years, a number of methodological innovations have provided the opportunity for cultured cells to be grown as 3-dimensional (3D) assemblies, for example as spheroids and organoids. These structures have the potential to better replicate the cellular environment found in tissues and present an exciting new opportunity for the study of cell function. In this mini-review, we summarize the main methods used to generate 3D cell models and highlight emerging studies that have started to use these models to study basic cellular processes. We also describe a number of pieces of work that potentially provide the basis for adaptation for deeper study of how membrane traffic is coordinated in multicellular assemblies. Finally, we comment on some of the technological challenges that still need to be overcome if 3D cell biology is to become a mainstream tool toward deepening our understanding of the endomembrane system in mammalian cells.

scholarly journals Cell3: A new vision for study of the endomembrane system in mammalian cells

2021 ◽  
Author(s):  
Margaritha M. Mysior ◽  
Jeremy C. Simpson
Keyword(s):  
Membrane Trafficking ◽  
Cell Biology ◽  
Mammalian Cells ◽  
Cell Function ◽  
Cultured Cells ◽  
Membrane Traffic ◽  
Endomembrane System ◽  
Cellular Environment ◽  
New Vision ◽  
The Individual

The endomembrane system of mammalian cells provides massive capacity for the segregation of biochemical reactions into discrete locations. The individual organelles of the endomembrane system also require the ability to precisely transport material between these compartments in order to maintain cell homeostasis; this process is termed membrane traffic. For several decades, researchers have been systematically identifying and dissecting the molecular machinery that governs membrane trafficking pathways, with the overwhelming majority of these studies being carried out in cultured cells growing as monolayers. In recent years, a number of methodological innovations have provided the opportunity for cultured cells to be grown as 3-dimensional (3D) assemblies, for example as spheroids and organoids. These structures have the potential to better replicate the cellular environment found in tissues, and present an exciting new opportunity for the study of cell function. In this mini-review we summarise the main methods used to generate 3D cell models, and highlight emerging studies that have started to use these models to study basic cellular processes. We also describe a number of pieces of work that potentially provide the basis for adaptation for deeper study of how membrane traffic is coordinated in multicellular assemblies. Finally, we comment on some of the technological challenges that still need to be overcome if 3D cell biology is to become a mainstream tool towards deepening our understanding of the endomembrane system in mammalian cells.

scholarly journals Intoxication of mammalian cells with binary clostridial enterotoxins is inhibited by the combination of pharmacological chaperone inhibitors

2020 ◽  
Author(s):  
Katharina Ernst ◽  
Judith Sailer ◽  
Maria Braune ◽  
Holger Barth
Keyword(s):  
Mammalian Cells ◽  
Clinical Symptoms ◽  
Target Cells ◽  
Pharmacological Chaperone ◽  
Fk506 Binding Protein ◽  
Clostridioides Difficile ◽  
Endosomal Membranes ◽  
Separate Protein ◽  
Protein Components ◽  
The Individual

AbstractBinary enterotoxins Clostridioides difficile CDT toxin, Clostridium botulinum C2 toxin, and Clostridium perfringens iota toxin consist of two separate protein components. The B-components facilitate receptor-mediated uptake into mammalian cells and form pores into endosomal membranes through which the enzymatic active A-components translocate into the cytosol. Here, the A-components ADP-ribosylate G-actin which leads to F-actin depolymerization followed by rounding of cells which causes clinical symptoms. The protein folding helper enzymes Hsp90, Hsp70, and peptidyl-prolyl cis/trans isomerases of the cyclophilin (Cyp) and FK506 binding protein (FKBP) families are required for translocation of A-components of CDT, C2, and iota toxins from endosomes to the cytosol. Here, we demonstrated that simultaneous inhibition of these folding helpers by specific pharmacological inhibitors protects mammalian, including human, cells from intoxication with CDT, C2, and iota toxins, and that the inhibitor combination displayed an enhanced effect compared to application of the individual inhibitors. Moreover, combination of inhibitors allowed a concentration reduction of the individual compounds as well as decreasing of the incubation time with inhibitors to achieve a protective effect. These results potentially have implications for possible future therapeutic applications to relieve clinical symptoms caused by bacterial toxins that depend on Hsp90, Hsp70, Cyps, and FKBPs for their membrane translocation into the cytosol of target cells.

Functional compartmentalization of the nucleus

1996 ◽  
Vol 109 (8) ◽  
pp. 1991-2000 ◽  
Author(s):  
J. Strouboulis ◽  
A.P. Wolffe
Keyword(s):  
Rna Processing ◽  
Cell Biology ◽  
Structural Organization ◽  
Nuclear Organization ◽  
Nuclear Architecture ◽  
Molecular Machines ◽  
Metabolic Activities ◽  
High Level ◽  
Regulatory Functions ◽  
Very High

Recent applications of cell biology and molecular genetics have built an image of nuclear organization in which the molecular machines involved in transcription, RNA processing and replication assemble morphologically distinct nuclear organelles with defined functional properties. These observations indicate a very high level of structural organization for the various metabolic activities occurring within the nucleus. We discuss the possible existence of novel regulatory functions inherent to nuclear architecture itself.

scholarly journals Linking cortical microtubule attachment and exocytosis

F1000Research ◽  
2017 ◽  
Vol 6 ◽  
pp. 469 ◽  
Author(s):  
Ivar Noordstra ◽  
Anna Akhmanova
Keyword(s):  
Targeted Delivery ◽  
Mammalian Cells ◽  
Spatial Organization ◽  
Protein Complexes ◽  
Cortical Microtubule ◽  
Actin Binding ◽  
Cell Cortex ◽  
Microtubule Organization ◽  
Vesicle Docking ◽  
Microtubule Attachment

Exocytosis is a fundamental cellular process whereby secreted molecules are packaged into vesicles that move along cytoskeletal filaments and fuse with the plasma membrane. To function optimally, cells are strongly dependent on precisely controlled delivery of exocytotic cargo. In mammalian cells, microtubules serve as major tracks for vesicle transport by motor proteins, and thus microtubule organization is important for targeted delivery of secretory carriers. Over the years, multiple microtubule-associated and cortical proteins have been discovered that facilitate the interaction between the microtubule plus ends and the cell cortex. In this review, we focus on mammalian protein complexes that have been shown to participate in both cortical microtubule capture and exocytosis, thereby regulating the spatial organization of secretion. These complexes include microtubule plus-end tracking proteins, scaffolding factors, actin-binding proteins, and components of vesicle docking machinery, which together allow efficient coordination of cargo transport and release.

scholarly journals Solubilization of isolated central-nervous-system myelin preparations by the amniotic detergent sodium dodecyl sulphate

1978 ◽  
Vol 173 (3) ◽  
pp. 909-917 ◽  
Author(s):  
A J Crang ◽  
M G Rumsby
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Sodium Dodecyl Sulphate ◽  
Protein Complexes ◽  
Sodium Dodecyl ◽  
Gel Filtration ◽  
Supernatant Fraction ◽  
Protein Components ◽  
The Individual ◽  
Membrane Components

The mechanism for the solubilization of isolated central-nervous-system myelin by sodium dodecyl sulphate was studied in detail. The release of protein and phospholipid to the 100000 g x 1 h supernatant fraction is dependent on the total amount of detergent relative to the amount of membrane present and on the ionic strength of the solubilization system. Gel-filtration analysis of supernatant fractions indicate that at suboptimal concentrations of detergent these contain lipid-protein complexes. The complete dissociation of the individual protein components from lipid is dependent on the total amount of sodium dodecyl sulphate present in the system. The results indicate that for the analysis of membrane components in sodium dodecyl sulphate it is essential that sufficient detergent is present.

scholarly journals Signal-transducing protein phosphorylation cascades mediated by Ras/Rho proteins in the mammalian cell: the potential for multiplex signalling

1996 ◽  
Vol 318 (3) ◽  
pp. 729-747 ◽  
Author(s):  
David T DENHARDT
Keyword(s):  
Map Kinase ◽  
Protein Phosphorylation ◽  
Mammalian Cells ◽  
Protein Complexes ◽  
Dynamic Balance ◽  
Signal Transmission ◽  
Target Cells ◽  
Rho Proteins ◽  
Signalling Molecules ◽  
The Individual

The features of three distinct protein phosphorylation cascades in mammalian cells are becoming clear. These signalling pathways link receptor-mediated events at the cell surface or intracellular perturbations such as DNA damage to changes in cytoskeletal structure, vesicle transport and altered transcription factor activity. The best known pathway, the Ras → Raf → MEK → ERK cascade [where ERK is extracellular-signal-regulated kinase and MEK is mitogen-activated protein (MAP) kinase/ERK kinase], is typically stimulated strongly by mitogens and growth factors. The other two pathways, stimulated primarily by assorted cytokines, hormones and various forms of stress, predominantly utilize p21 proteins of the Rho family (Rho, Rac and CDC42), although Ras can also participate. Diagnostic of each pathway is the MAP kinase component, which is phosphorylated by a unique dual-specificity kinase on both tyrosine and threonine in one of three motifs (Thr-Glu-Tyr, Thr-Phe-Tyr or Thr-Gly-Tyr), depending upon the pathway. In addition to activating one or more protein phosphorylation cascades, the initiating stimulus may also mobilize a variety of other signalling molecules (e.g. protein kinase C isoforms, phospholipid kinases, G-protein α and βγ subunits, phospholipases, intracellular Ca2+). These various signals impact to a greater or lesser extent on multiple downstream effectors. Important concepts are that signal transmission often entails the targeted relocation of specific proteins in the cell, and the reversible formation of protein complexes by means of regulated protein phosphorylation. The signalling circuits may be completed by the phosphorylation of upstream effectors by downstream kinases, resulting in a modulation of the signal. Signalling is terminated and the components returned to the ground state largely by dephosphorylation. There is an indeterminant amount of cross-talk among the pathways, and many of the proteins in the pathways belong to families of closely related proteins. The potential for more than one signal to be conveyed down a pathway simultaneously (multiplex signalling) is discussed. The net effect of a given stimulus on the cell is the result of a complex intracellular integration of the intensity and duration of activation of the individual pathways. The specific outcome depends on the particular signalling molecules expressed by the target cells and on the dynamic balance among the pathways.

scholarly journals Probing the biogenesis pathway and dynamics of thylakoid membranes

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Tuomas Huokko ◽  
Tao Ni ◽  
Gregory F. Dykes ◽  
Deborah M. Simpson ◽  
Philip Brownridge ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Photosystem I ◽  
Spatial Organization ◽  
Electron Flux ◽  
Protein Complexes ◽  
Thylakoid Membranes ◽  
Thylakoid Biogenesis ◽  
Photosynthetic Complexes ◽  
Photosynthetic Machinery ◽  
Pcc 7942

AbstractHow thylakoid membranes are generated to form a metabolically active membrane network and how thylakoid membranes orchestrate the insertion and localization of protein complexes for efficient electron flux remain elusive. Here, we develop a method to modulate thylakoid biogenesis in the rod-shaped cyanobacterium Synechococcus elongatus PCC 7942 by modulating light intensity during cell growth, and probe the spatial-temporal stepwise biogenesis process of thylakoid membranes in cells. Our results reveal that the plasma membrane and regularly arranged concentric thylakoid layers have no physical connections. The newly synthesized thylakoid membrane fragments emerge between the plasma membrane and pre-existing thylakoids. Photosystem I monomers appear in the thylakoid membranes earlier than other mature photosystem assemblies, followed by generation of Photosystem I trimers and Photosystem II complexes. Redistribution of photosynthetic complexes during thylakoid biogenesis ensures establishment of the spatial organization of the functional thylakoid network. This study provides insights into the dynamic biogenesis process and maturation of the functional photosynthetic machinery.

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