scholarly journals Nanomachinery Organizing Release at Neuronal and Ribbon Synapses

2019 ◽  
Vol 20 (9) ◽  
pp. 2147 ◽  
Author(s):  
Chakrabarti ◽  
Wichmann
Keyword(s):  
Electron Tomography ◽  
Molecular Architecture ◽  
Inner Hair Cell ◽  
Presynaptic Nerve Terminal ◽  
Ultrastructural Studies ◽  
Ribbon Synapses ◽  
Neuronal Synapses ◽  
Electrophysiological Recordings

A critical aim in neuroscience is to obtain a comprehensive view of how regulated neurotransmission is achieved. Our current understanding of synapses relies mainly on data from electrophysiological recordings, imaging, and molecular biology. Based on these methodologies, proteins involved in a synaptic vesicle (SV) formation, mobility, and fusion at the active zone (AZ) membrane have been identified. In the last decade, electron tomography (ET) combined with a rapid freezing immobilization of neuronal samples opened a window for understanding the structural machinery with the highest spatial resolution in situ. ET provides significant insights into the molecular architecture of the AZ and the organelles within the presynaptic nerve terminal. The specialized sensory ribbon synapses exhibit a distinct architecture from neuronal synapses due to the presence of the electron-dense synaptic ribbon. However, both synapse types share the filamentous structures, also commonly termed as tethers that are proposed to contribute to different steps of SV recruitment and exocytosis. In this review, we discuss the emerging views on the role of filamentous structures in SV exocytosis gained from ultrastructural studies of excitatory, mainly central neuronal compared to ribbon-type synapses with a focus on inner hair cell (IHC) ribbon synapses. Moreover, we will speculate on the molecular entities that may be involved in filament formation and hence play a crucial role in the SV cycle.

scholarly journals Molecular architecture of inner dynein arms in situ in Chlamydomonas reinhardtii flagella

2008 ◽  
Vol 183 (5) ◽  
pp. 923-932 ◽  
Author(s):  
Khanh Huy Bui ◽  
Hitoshi Sakakibara ◽  
Tandis Movassagh ◽  
Kazuhiro Oiwa ◽  
Takashi Ishikawa
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Electron Tomography ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Molecular Architecture ◽  
Heavy Chains ◽  
Distal Side ◽  
Cryo Electron Tomography ◽  
Dynein Arms

The inner dynein arm regulates axonemal bending motion in eukaryotes. We used cryo-electron tomography to reconstruct the three-dimensional structure of inner dynein arms from Chlamydomonas reinhardtii. All the eight different heavy chains were identified in one 96-nm periodic repeat, as expected from previous biochemical studies. Based on mutants, we identified the positions of the AAA rings and the N-terminal tails of all the eight heavy chains. The dynein f dimer is located close to the surface of the A-microtubule, whereas the other six heavy chain rings are roughly colinear at a larger distance to form three dyads. Each dyad consists of two heavy chains and has a corresponding radial spoke or a similar feature. In each of the six heavy chains (dynein a, b, c, d, e, and g), the N-terminal tail extends from the distal side of the ring. To interact with the B-microtubule through stalks, the inner-arm dyneins must have either different handedness or, more probably, the opposite orientation of the AAA rings compared with the outer-arm dyneins.

scholarly journals Visualizing insulin vesicle neighborhoods in β cells by cryo–electron tomography

2020 ◽  
Vol 6 (50) ◽  
pp. eabc8258
Author(s):  
Xianjun Zhang ◽  
Stephen D. Carter ◽  
Jitin Singla ◽  
Kate L. White ◽  
Peter C. Butler ◽  
...  
Keyword(s):  
Secretory Pathway ◽  
Electron Tomography ◽  
Secretory Cells ◽  
Nanometer Scale ◽  
Β Cells ◽  
Cellular Volume ◽  
Cryo Electron Tomography ◽  
Average Size

Subcellular neighborhoods, comprising specific ratios of organelles and proteins, serve a multitude of biological functions and are of particular importance in secretory cells. However, the role of subcellular neighborhoods in insulin vesicle maturation is poorly understood. Here, we present single-cell multiple distinct tomogram acquisitions of β cells for in situ visualization of distinct subcellular neighborhoods that are involved in the insulin vesicle secretory pathway. We propose that these neighborhoods play an essential role in the specific function of cellular material. In the regions where we observed insulin vesicles, a measurable increase in both the fraction of cellular volume occupied by vesicles and the average size (diameter) of the vesicles was apparent as sampling moved from the area near the nucleus toward the plasma membrane. These findings describe the important role of the nanometer-scale organization of subcellular neighborhoods on insulin vesicle maturation.

scholarly journals High Throughput Cryo-Electron Tomography: Towards Molecular Architecture of Spirochetal Flagellar Motor in situ

2010 ◽  
Vol 16 (S2) ◽  
pp. 1070-1071
Author(s):  
J Liu ◽  
S Norris
Keyword(s):  
High Throughput ◽  
Electron Tomography ◽  
Flagellar Motor ◽  
Molecular Architecture ◽  
Cryo Electron Tomography

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.

scholarly journals In situ architecture of neuronal α-Synuclein inclusions

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Victoria A. Trinkaus ◽  
Irene Riera-Tur ◽  
Antonio Martínez-Sánchez ◽  
Felix J. B. Bäuerlein ◽  
Qiang Guo ◽  
...  
Keyword(s):  
Detailed Analysis ◽  
Neurodegenerative Disorders ◽  
Electron Tomography ◽  
Cellular Interaction ◽  
Molecular Architecture ◽  
Membrane Interactions ◽  
Intracellular Membranes ◽  
Cryo Electron Tomography ◽  
Cellular Organelles

AbstractThe molecular architecture of α-Synuclein (α-Syn) inclusions, pathognomonic of various neurodegenerative disorders, remains unclear. α-Syn inclusions were long thought to consist mainly of α-Syn fibrils, but recent reports pointed to intracellular membranes as the major inclusion component. Here, we use cryo-electron tomography (cryo-ET) to image neuronal α-Syn inclusions in situ at molecular resolution. We show that inclusions seeded by α-Syn aggregates produced recombinantly or purified from patient brain consist of α-Syn fibrils crisscrossing a variety of cellular organelles. Using gold-labeled seeds, we find that aggregate seeding is predominantly mediated by small α-Syn fibrils, from which cytoplasmic fibrils grow unidirectionally. Detailed analysis of membrane interactions revealed that α-Syn fibrils do not contact membranes directly, and that α-Syn does not drive membrane clustering. Altogether, we conclusively demonstrate that neuronal α-Syn inclusions consist of α-Syn fibrils intermixed with membranous organelles, and illuminate the mechanism of aggregate seeding and cellular interaction.

scholarly journals In situ Alphavirus Assembly and Budding Mechanism Revealed by Cellular CryoET

2021 ◽  
Author(s):  
David Chmielewski ◽  
Michael Schmid ◽  
Graham Simmons ◽  
Jing Jin ◽  
Wah Chiu
Keyword(s):  
Plasma Membrane ◽  
Electron Tomography ◽  
Virus Budding ◽  
Enveloped Virus ◽  
Infected Cells ◽  
Membrane Bending ◽  
Average Structures

Abstract Chikungunya virus (CHIKV) is a representative alphavirus causing debilitating arthritogenic disease in humans. Alphavirus particles assemble into two icosahedral protein layers: the glycoprotein spike shell embedded in a lipid envelope and the inner nucleocapsid (NC) core. In contrast to matrix-driven assembly of some enveloped viruses, the assembly/budding process of two-layered icosahedral particles remains poorly understood. Here we used cryogenic electron tomography (cryoET) to capture snapshots of the CHIKV assembly process in infected human cells. Subvolume classification of the snapshots revealed 12 intermediate structures, representing different stages of assembly/budding at the plasma membrane. Further subtomogram average structures ranging from subnanometer to nanometer resolutions show that immature, non-icosahedral NCs function as rough scaffolds to trigger icosahedral assembly of the glycoprotein spike lattice, which in turn progressively transforms the underlying NCs into icosahedral cores during budding. Here we resolve a long-standing mechanistic question about the role of spikes and NCs in assembly of two-layered icosahedral shells. Further, data of CHIKV-infected cells treated with budding-inhibiting antibodies shows that spacing spikes apart to prevent their lateral interactions prevents the plasma membrane bending around NC cores, thus blocking virus budding. These findings provide the molecular details of icosahedral enveloped virus formation and antibodies against assembly/budding.

{10-12} Twinning Mechanism During In Situ Micro-Tensile Loading of Pure Mg: Role of Basal Slip and Twin-Twin Boundary Interaction

2020 ◽  
Author(s):  
Nicolò Maria della Ventura ◽  
Szilvia Kalácska ◽  
Daniele Casari ◽  
Thomas Edward James Edwards ◽  
Johann Michler ◽  
...  
Keyword(s):  
Twin Boundary ◽  
Basal Slip ◽  
Tensile Loading ◽  
Boundary Interaction

The role of (bio)surfactant sorption in promoting the bioavailability of nutrients localized at the solid-water interface

1999 ◽  
Vol 39 (7) ◽  
pp. 91-98 ◽  
Author(s):  
Ryan N. Jordan ◽  
Eric P. Nichols ◽  
Alfred B. Cunningham
Keyword(s):  
Mass Transfer ◽  
Cell Membrane ◽  
Substrate Concentration ◽  
Water Interface ◽  
Industrial Systems ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Surfactant Sorption

Bioavailability is herein defined as the accessibility of a substrate by a microorganism. Further, bioavailability is governed by (1) the substrate concentration that the cell membrane “sees,” (i.e., the “directly bioavailable” pool) as well as (2) the rate of mass transfer from potentially bioavailable (e.g., nonaqueous) phases to the directly bioavailable (e.g., aqueous) phase. Mechanisms by which sorbed (bio)surfactants influence these two processes are discussed. We propose the hypothesis that the sorption of (bio)surfactants at the solid-liquid interface is partially responsible for the increased bioavailability of surface-bound nutrients, and offer this as a basis for suggesting the development of engineered in-situ bioremediation technologies that take advantage of low (bio)surfactant concentrations. In addition, other industrial systems where bioavailability phenomena should be considered are addressed.

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