scholarly journals Mechanism of shaping membrane nanostructures of endoplasmic reticulum

2021 ◽  
Vol 119 (1) ◽  
pp. e2116142119
Author(s):  
Ben Zucker ◽  
Michael M. Kozlov
Keyword(s):  
Endoplasmic Reticulum ◽  
Discrete Series ◽  
Super Resolution ◽  
Structural Motif ◽  
Physical Factors ◽  
Equilibrium Configurations ◽  
Er Exit Sites ◽  
Common Concept ◽  
The One ◽  
Low Tension

Recent advances in super-resolution microscopy revealed the previously unknown nanoscopic level of organization of endoplasmic reticulum (ER), one of the most vital intracellular organelles. Membrane nanostructures of 10- to 100-nm intrinsic length scales, which include ER tubular matrices, ER sheet nanoholes, internal membranes of ER exit sites (ERES), and ER transport intermediates, were discovered and imaged in considerable detail, but the physical factors determining their unique geometrical features remained unknown. Here, we proposed and computationally substantiated a common concept for mechanisms of all ER nanostructures based on the membrane intrinsic curvature as a primary factor shaping the membrane and ultra-low membrane tensions as modulators of the membrane configurations. We computationally revealed a common structural motif underlying most of the nanostructures. We predicted the existence of a discrete series of equilibrium configurations of ER tubular matrices and recovered the one corresponding to the observations and favored by ultra-low tensions. We modeled the nanohole formation as resulting from a spontaneous collapse of elements of the ER tubular network adjacent to the ER sheet edge and calculated the nanohole dimensions. We proposed the ERES membrane to have a shape of a super flexible membrane bead chain, which acquires random walk configurations unless an ultra-low tension converts it into a straight conformation of a transport intermediate. The adequacy of the proposed concept is supported by a close qualitative and quantitative similarity between the predicted and observed configurations of all four ER nanostructures.

scholarly journals New insights into protein secretion: TANGO1 runs rings around the COPII coat

2017 ◽  
Vol 216 (4) ◽  
pp. 859-861 ◽  
Author(s):  
Benjamin S. Glick
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Secretion ◽  
Super Resolution ◽  
Cell Biol ◽  
Er Exit Sites ◽  
Er Export ◽  
Super Resolution Microscopy

In this issue, Liu et al. (2017. J. Cell Biol. https://doi.org/10.1083/jcb.201611088) and Raote et al. (2017. J. Cell Biol. https://doi.org/10.1083/jcb.201608080) use super-resolution microscopy to visualize large COPII-coated endoplasmic reticulum (ER) export carriers. Rings of TANGO1 surround COPII, implicating TANGO1 in organizing ER exit sites and in regulating COPII coat dynamics and geometry.

Structural Evidence of Photoisomerization Pathways in Fluorescent Proteins

2019 ◽  
Author(s):  
Jeffrey Chang ◽  
Matthew Romei ◽  
Steven Boxer
Keyword(s):  
Rational Design ◽  
Fluorescent Protein ◽  
Fluorescent Proteins ◽  
Super Resolution ◽  
Unit Cell Size ◽  
Chlorine Substituent ◽  
Gfp Chromophore ◽  
The One ◽  
Green Fluorescent ◽  
Super Resolution Microscopy

<p>Double-bond photoisomerization in molecules such as the green fluorescent protein (GFP) chromophore can occur either via a volume-demanding one-bond-flip pathway or via a volume-conserving hula-twist pathway. Understanding the factors that determine the pathway of photoisomerization would inform the rational design of photoswitchable GFPs as improved tools for super-resolution microscopy. In this communication, we reveal the photoisomerization pathway of a photoswitchable GFP, rsEGFP2, by solving crystal structures of <i>cis</i> and <i>trans</i> rsEGFP2 containing a monochlorinated chromophore. The position of the chlorine substituent in the <i>trans</i> state breaks the symmetry of the phenolate ring of the chromophore and allows us to distinguish the two pathways. Surprisingly, we find that the pathway depends on the arrangement of protein monomers within the crystal lattice: in a looser packing, the one-bond-flip occurs, whereas in a tighter packing (7% smaller unit cell size), the hula-twist occurs.</p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p> <p> </p>

scholarly journals Alternative redox forms of ASNA-1 separate insulin signaling from tail-anchored protein targeting and cisplatin resistance in C. elegans

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Dorota Raj ◽  
Ola Billing ◽  
Agnieszka Podraza-Farhanieh ◽  
Bashar Kraish ◽  
Oskar Hemmingsson ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Insulin Secretion ◽  
Protein Targeting ◽  
Cisplatin Resistance ◽  
Acquired Resistance ◽  
Endoplasmic Reticulum Membrane ◽  
C Elegans ◽  
Cisplatin Sensitivity ◽  
Tumor Environment ◽  
The One

AbstractCisplatin is a frontline cancer therapeutic, but intrinsic or acquired resistance is common. We previously showed that cisplatin sensitivity can be achieved by inactivation of ASNA-1/TRC40 in mammalian cancer cells and in Caenorhabditis elegans. ASNA-1 has two more conserved functions: in promoting tail-anchored protein (TAP) targeting to the endoplasmic reticulum membrane and in promoting insulin secretion. However, the relation between its different functions has remained unknown. Here, we show that ASNA-1 exists in two redox states that promote TAP-targeting and insulin secretion separately. The reduced state is the one required for cisplatin resistance: an ASNA-1 point mutant, in which the protein preferentially was found in the oxidized state, was sensitive to cisplatin and defective for TAP targeting but had no insulin secretion defect. The same was true for mutants in wrb-1, which we identify as the C. elegans homolog of WRB, the ASNA1/TRC40 receptor. Finally, we uncover a previously unknown action of cisplatin induced reactive oxygen species: cisplatin induced ROS drives ASNA-1 into the oxidized form, and selectively prevents an ASNA-1-dependent TAP substrate from reaching the endoplasmic reticulum. Our work suggests that ASNA-1 acts as a redox-sensitive target for cisplatin cytotoxicity and that cisplatin resistance is likely mediated by ASNA-1-dependent TAP substrates. Treatments that promote an oxidizing tumor environment should be explored as possible means to combat cisplatin resistance.

scholarly journals Aβ receptors specifically recognize molecular features displayed by fibril ends and neurotoxic oligomers

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ladan Amin ◽  
David A. Harris
Keyword(s):  
Amyloid Β ◽  
Super Resolution ◽  
Structural Motif ◽  
Aβ Oligomers ◽  
Surface Receptors ◽  
Molecular Features ◽  
Molecular Determinant ◽  
Receptor Interactions ◽  
Aβ Fibrils ◽  
Super Resolution Microscopy

AbstractSeveral cell-surface receptors for neurotoxic forms of amyloid-β (Aβ) have been described, but their molecular interactions with Aβ assemblies and their relative contributions to mediating Alzheimer’s disease pathology have remained uncertain. Here, we used super-resolution microscopy to directly visualize Aβ-receptor interactions at the nanometer scale. We report that one documented Aβ receptor, PrPC, specifically inhibits the polymerization of Aβ fibrils by binding to the rapidly growing end of each fibril, thereby blocking polarized elongation at that end. PrPC binds neurotoxic oligomers and protofibrils in a similar fashion, suggesting that it may recognize a common, end-specific, structural motif on all of these assemblies. Finally, two other Aβ receptors, FcγRIIb and LilrB2, affect Aβ fibril growth in a manner similar to PrPC. Our results suggest that receptors may trap Aβ oligomers and protofibrils on the neuronal surface by binding to a common molecular determinant on these assemblies, thereby initiating a neurotoxic signal.

Cubic spline-based depth-dependent localization of mitochondria–endoplasmic reticulum contacts by three-dimensional light-sheet super-resolution microscopy

The Analyst ◽  
2021 ◽  
Author(s):  
Yucheng Sun ◽  
Seungah Lee ◽  
Seong Ho Kang
Keyword(s):  
Endoplasmic Reticulum ◽  
Calcium Homeostasis ◽  
Three Dimensional ◽  
Super Resolution ◽  
Light Sheet ◽  
Cubic Spline ◽  
Contact Distance ◽  
Super Resolution Microscopy

The contact distance between mitochondria (Mito) and endoplasmic reticulum (ER) has received considerable attention owing to their crucial function in maintaining lipid and calcium homeostasis. Herein, cubic spline algorithm-based depth-dependent...

scholarly journals Mechanism for antigenic peptide selection by endoplasmic reticulum aminopeptidase 1

2019 ◽  
Vol 116 (52) ◽  
pp. 26709-26716 ◽  
Author(s):  
Petros Giastas ◽  
Anastasia Mpakali ◽  
Athanasios Papakyriakou ◽  
Aggelos Lelis ◽  
Paraskevi Kokkala ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Structural Motif ◽  
Internal Cavity ◽  
Sequence Specificity ◽  
Substrate Selection ◽  
Class I Mhc ◽  
Mhc I ◽  
Intracellular Enzyme ◽  
C Terminus ◽  
Endoplasmic Reticulum Aminopeptidase 1

Endoplasmic reticulum aminopeptidase 1 (ERAP1) is an intracellular enzyme that optimizes the peptide cargo of major histocompatibility class I (MHC-I) molecules and regulates adaptive immunity. It has unusual substrate selectivity for length and sequence, resulting in poorly understood effects on the cellular immunopeptidome. To understand substrate selection by ERAP1, we solved 2 crystal structures of the enzyme with bound transition-state pseudopeptide analogs at 1.68 Å and 1.72 Å. Both peptides have their N terminus bound at the active site and extend away along a large internal cavity, interacting with shallow pockets that can influence selectivity. The longer peptide is disordered through the central region of the cavity and has its C terminus bound in an allosteric pocket of domain IV that features a carboxypeptidase-like structural motif. These structures, along with enzymatic and computational analyses, explain how ERAP1 can select peptides based on length while retaining the broad sequence-specificity necessary for its biological function.

scholarly journals Super Resolution Microscopy and Deep Learning Identify Zika Virus Reorganization of the Endoplasmic Reticulum

2020 ◽  
Author(s):  
Rory K. M. Long ◽  
Kathleen P. Moriarty ◽  
Ben Cardoen ◽  
Guang Gao ◽  
A. Wayne Vogl ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Deep Learning ◽  
Viral Replication ◽  
Zika Virus ◽  
Deep Neural Networks ◽  
Super Resolution ◽  
Zikv Infection ◽  
Subcellular Organelle ◽  
Infected Cells ◽  
Super Resolution Microscopy

AbstractThe endoplasmic reticulum (ER) is a complex subcellular organelle composed of diverse structures such as tubules, sheets and tubular matrices. Flaviviruses such as Zika virus (ZIKV) induce reorganization of endoplasmic reticulum (ER) membranes to facilitate viral replication. Here, using 3D super resolution microscopy, ZIKV infection is shown to induce the formation of dense tubular matrices associated with viral replication in the central ER. Viral non-structural proteins NS4B and NS2B associate with replication complexes within the ZIKV-induced tubular matrix and exhibit distinct ER distributions outside this central ER region. Deep neural networks trained to identify ZIKV-infected versus mock-infected cells successfully identified ZIKV-induced central ER tubular matrices as a determinant of viral infection. Super resolution microscopy and deep learning are therefore able to identify and localize morphological features of the ER and may be of use to screen for inhibitors of infection by ER-reorganizing viruses.

scholarly journals THE ELABORATION OF PROTEIN AND CARBOHYDRATE BY RAT PARATHYROID CELLS AS REVEALED BY ELECTRON MICROSCOPE RADIOAUTOGRAPHY

1971 ◽  
Vol 51 (3) ◽  
pp. 596-610 ◽  
Author(s):  
K. Nakagami ◽  
H. Warshawsky ◽  
C. P. Leblond
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Intravenous Injection ◽  
Rough Endoplasmic Reticulum ◽  
Secretory Granules ◽  
Glycoprotein Precursor ◽  
Secretion Granules ◽  
And Migration ◽  
The One ◽  
Membrane Cell

The parathyroid glands of young rats were radioautographed after a single injection of the protein precursor tyrosine-3H in the hope of identifying the sites of synthesis and migration of newly formed protein in the gland cells. The same procedure was used after injection of the glycoprotein precursor galactose-3H. As early as 2 min after intravenous injection of tyrosine-3H, the label was mainly found in the rough endoplasmic reticulum suggesting that cisternal ribosomes are sites of protein synthesis. By 5 and 10 min, much of the label had migrated from the rough endoplasmic reticulum into the Golgi apparatus. By 20 and 30 min, some label had migrated from there into secretory granules. By 45 min and 1 hr, the label content of the cell had decreased, indicating release of labeled material outside the cell. At 2 min after intravenous injection of galactose-3H, the label was mainly present in the Golgi apparatus, where presumably galactose is taken up into glycoprotein. By 10 min, some label appeared in secretion granules and by 30 min release of the material to the outside of the cell was under way. In conclusion, it is likely that the tyrosine-labeled protein material consists mainly of the parathyroid hormone. The galactose-labeled carbohydrate material would be either associated with the hormone in the cell or be part of a distinct glycoprotein which may be the one present on the outer surface of the plasma membrane (cell coat).

scholarly journals Vesicular and uncoated Rab1-dependent cargo carriers facilitate ER to Golgi transport

2020 ◽  
Vol 133 (14) ◽  
pp. jcs239814 ◽  
Author(s):  
Laura M. Westrate ◽  
Melissa J. Hoyer ◽  
Michael J. Nash ◽  
Gia K. Voeltz
Keyword(s):  
Endoplasmic Reticulum ◽  
De Novo ◽  
Coated Vesicle ◽  
First Person ◽  
Coat Proteins ◽  
Animal Cells ◽  
Golgi Transport ◽  
Er Exit Sites ◽  
Copii Vesicles ◽  
Export System

ABSTRACTSecretory cargo is recognized, concentrated and trafficked from endoplasmic reticulum (ER) exit sites (ERES) to the Golgi. Cargo export from the ER begins when a series of highly conserved COPII coat proteins accumulate at the ER and regulate the formation of cargo-loaded COPII vesicles. In animal cells, capturing live de novo cargo trafficking past this point is challenging; it has been difficult to discriminate whether cargo is trafficked to the Golgi in a COPII-coated vesicle. Here, we describe a recently developed live-cell cargo export system that can be synchronously released from ERES to illustrate de novo trafficking in animal cells. We found that components of the COPII coat remain associated with the ERES while cargo is extruded into COPII-uncoated, non-ER associated, Rab1 (herein referring to Rab1a or Rab1b)-dependent carriers. Our data suggest that, in animal cells, COPII coat components remain stably associated with the ER at exit sites to generate a specialized compartment, but once cargo is sorted and organized, Rab1 labels these export carriers and facilitates efficient forward trafficking.This article has an associated First Person interview with the first author of the paper.

scholarly journals A Simple Probe for Super-Resolution Imaging of the Endoplasmic Reticulum in Living Cells

2018 ◽  
Vol 101 (11) ◽  
pp. e1800165 ◽  
Author(s):  
Elias A. Halabi ◽  
Salome Püntener ◽  
Pablo Rivera-Fuentes
Keyword(s):  
Endoplasmic Reticulum ◽  
Super Resolution ◽  
Living Cells ◽  
Resolution Imaging
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