scholarly journals Elucidation of AMPA receptor–stargazin complexes by cryo–electron microscopy

Science ◽  
2016 ◽  
Vol 353 (6294) ◽  
pp. 83-86 ◽  
Author(s):  
Edward C. Twomey ◽  
Maria V. Yelshanskaya ◽  
Robert A. Grassucci ◽  
Joachim Frank ◽  
Alexander I. Sobolevsky
Keyword(s):  
Electron Microscopy ◽  
Cognitive Processes ◽  
Electrostatic Interactions ◽  
Structural Basis ◽  
Cryo Electron Microscopy ◽  
Activated State ◽  
Ampar Trafficking ◽  
Excitatory Neurotransmission ◽  
Binding Interfaces ◽  
The Brain

AMPA-subtype ionotropic glutamate receptors (AMPARs) mediate fast excitatory neurotransmission and contribute to high cognitive processes such as learning and memory. In the brain, AMPAR trafficking, gating, and pharmacology is tightly controlled by transmembrane AMPAR regulatory proteins (TARPs). Here, we used cryo–electron microscopy to elucidate the structural basis of AMPAR regulation by one of these auxiliary proteins, TARP γ2, or stargazin (STZ). Our structures illuminate the variable interaction stoichiometry of the AMPAR-TARP complex, with one or two TARP molecules binding one tetrameric AMPAR. Analysis of the AMPAR-STZ binding interfaces suggests that electrostatic interactions between the extracellular domains of AMPAR and STZ play an important role in modulating AMPAR function through contact surfaces that are conserved across AMPARs and TARPs. We propose a model explaining how TARPs stabilize the activated state of AMPARs and how the interactions between AMPARs and their auxiliary proteins control fast excitatory synaptic transmission.

scholarly journals Cryo-EM structure and polymorphism of Aβ amyloid fibrils purified from Alzheimer’s brain tissue

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Marius Kollmer ◽  
William Close ◽  
Leonie Funk ◽  
Jay Rasmussen ◽  
Aref Bsoul ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Brain Tissue ◽  
Amyloid Fibrils ◽  
Structural Basis ◽  
Amyloid Angiopathy ◽  
Cryo Electron Microscopy ◽  
Aβ Amyloid ◽  
Cerebral Amyloid ◽  
Aβ Fibrils

Abstract The formation of Aβ amyloid fibrils is a neuropathological hallmark of Alzheimer’s disease and cerebral amyloid angiopathy. However, the structure of Aβ amyloid fibrils from brain tissue is poorly understood. Here we report the purification of Aβ amyloid fibrils from meningeal Alzheimer’s brain tissue and their structural analysis with cryo-electron microscopy. We show that these fibrils are polymorphic but consist of similarly structured protofilaments. Brain derived Aβ amyloid fibrils are right-hand twisted and their peptide fold differs sharply from previously analyzed Aβ fibrils that were formed in vitro. These data underscore the importance to use patient-derived amyloid fibrils when investigating the structural basis of the disease.

How Good Can Single-Particle Cryo-EM Become? What Remains Before It Approaches Its Physical Limits?

2019 ◽  
Vol 48 (1) ◽  
pp. 45-61 ◽  
Author(s):  
Robert M. Glaeser
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Single Particle ◽  
Energy Use ◽  
Optimal Choice ◽  
Structural Basis ◽  
Detective Quantum Efficiency ◽  
Quantum Metrology ◽  
Cryo Electron Microscopy ◽  
Induced Motion

Impressive though the achievements of single-particle cryo–electron microscopy are today, a substantial gap still remains between what is currently accomplished and what is theoretically possible. As is reviewed here, twofold or more improvements are possible as regards ( a) the detective quantum efficiency of cameras at high resolution, ( b) converting phase modulations to intensity modulations in the image, and ( c) recovering the full amount of high-resolution signal in the presence of beam-induced motion of the specimen. In addition, potential for improvement is reviewed for other topics such as optimal choice of electron energy, use of aberration correctors, and quantum metrology. With the help of such improvements, it does not seem to be too much to imagine that determining the structural basis for every aspect of catalytic control, signaling, and regulation, in any type of cell of interest, could easily be accelerated fivefold or more.

scholarly journals Structural basis of actin filament capping at the barbed-end: a cryo-electron microscopy study

2006 ◽  
Vol 25 (23) ◽  
pp. 5626-5633 ◽  
Author(s):  
Akihiro Narita ◽  
Shuichi Takeda ◽  
Atsuko Yamashita ◽  
Yuichiro Maéda
Keyword(s):  
Electron Microscopy ◽  
Actin Filament ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Structural Basis ◽  
Cryo Electron Microscopy

scholarly journals Cryo-EM Reveals the Structural Basis of Microtubule Depolymerization by Kinesin-13s

2017 ◽  
Author(s):  
Matthieu P. M. H. Benoit ◽  
Ana B. Asenjo ◽  
Hernando Sosa
Keyword(s):  
Electron Microscopy ◽  
Conformational Changes ◽  
Distinct Group ◽  
Atomic Resolution ◽  
Structural Basis ◽  
Structural Elements ◽  
Microtubule Depolymerization ◽  
Cryo Electron Microscopy ◽  
Kinesin Superfamily ◽  
Motile Activity

SummaryKinesin-13s constitute a distinct group within the kinesin superfamily of motor proteins that promotes microtubule depolymerization and lacks motile activity. The molecular mechanism by which the kinesins depolymerize microtubules and are adapted to perform a seemingly very different activity from other kinesins is still unclear. To address this issue we obtained near atomic resolution cryo-electron microscopy (cryo-EM) structures of Drosophila melanogaster kinesin-13 KLP10A constructs bound to curved or straight tubulin in different nucleotide states. The structures show how nucleotide induced conformational changes near the catalytic site are coupled with kinesin-13-specific structural elements to induce tubulin curvature leading to microtubule depolymerization. The data highlight a modular structure that allows similar kinesin core motor-domains to be used for different functions, such as motility or microtubule depolymerization.

scholarly journals Molecular basis for the ATPase-powered substrate translocation by the Lon AAA+ protease

2020 ◽  
Author(s):  
Kaiming Zhang ◽  
Shanshan Li ◽  
Kan-Yen Hsieh ◽  
Shih-Chieh Su ◽  
Grigore D. Pintilie ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Conformational Changes ◽  
Molecular Basis ◽  
Structural Basis ◽  
Cryo Electron Microscopy ◽  
Adenosine Triphosphatases ◽  
Translocation Mechanism ◽  
Atp Binding And Hydrolysis ◽  
Proteolytic Chamber ◽  
Specific Nucleotide

AbstractThe Lon AAA+ (adenosine triphosphatases associated with diverse cellular activities) protease (LonA) converts ATP-fuelled conformational changes into sufficient mechanical force to drive translocation of the substrate into a hexameric proteolytic chamber. To understand the structural basis for the substrate translocation process, we have determined the cryo-electron microscopy (cryo-EM) structure of Meiothermus taiwanensis LonA (MtaLonA) at 3.6 Å resolution in a substrate-engaged state. Substrate interactions are mediated by the dual pore-loops of the ATPase domains, organized in spiral staircase arrangement from four consecutive protomers in different ATP-binding and hydrolysis states; a closed AAA+ ring is nevertheless maintained by two disengaged ADP-bound protomers transiting between the lowest and highest position. The structure reveals a processive rotary translocation mechanism mediated by LonA-specific nucleotide-dependent allosteric coordination among the ATPase domains, which is induced by substrate binding.

scholarly journals Structural basis of ER-associated protein degradation mediated by the Hrd1 ubiquitin ligase complex

Science ◽  
2020 ◽  
Vol 368 (6489) ◽  
pp. eaaz2449 ◽  
Author(s):  
Xudong Wu ◽  
Marc Siggel ◽  
Sergey Ovchinnikov ◽  
Wei Mi ◽  
Vladimir Svetlov ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Ubiquitin Ligase ◽  
Dynamics Simulation ◽  
Structural Basis ◽  
Cryo Electron Microscopy ◽  
Ubiquitin Ligase Complex ◽  
Electron Microscopy Analysis ◽  
Microscopy Analysis ◽  
Simulation Results ◽  
Membrane Region

Misfolded luminal endoplasmic reticulum (ER) proteins undergo ER-associated degradation (ERAD-L): They are retrotranslocated into the cytosol, polyubiquitinated, and degraded by the proteasome. ERAD-L is mediated by the Hrd1 complex (composed of Hrd1, Hrd3, Der1, Usa1, and Yos9), but the mechanism of retrotranslocation remains mysterious. Here, we report a structure of the active Hrd1 complex, as determined by cryo–electron microscopy analysis of two subcomplexes. Hrd3 and Yos9 jointly create a luminal binding site that recognizes glycosylated substrates. Hrd1 and the rhomboid-like Der1 protein form two “half-channels” with cytosolic and luminal cavities, respectively, and lateral gates facing one another in a thinned membrane region. These structures, along with crosslinking and molecular dynamics simulation results, suggest how a polypeptide loop of an ERAD-L substrate moves through the ER membrane.

scholarly journals α/β-Hydrolase domain-containing 6 (ABHD6) negatively regulates the surface delivery and synaptic function of AMPA receptors

2016 ◽  
Vol 113 (19) ◽  
pp. E2695-E2704 ◽  
Author(s):  
Mengping Wei ◽  
Jian Zhang ◽  
Moye Jia ◽  
Chaojuan Yang ◽  
Yunlong Pan ◽  
...  
Keyword(s):  
Ampa Receptors ◽  
Surface Expression ◽  
Inhibitory Effect ◽  
Synaptic Function ◽  
Excitatory Synapses ◽  
C Terminus ◽  
Ampar Trafficking ◽  
Excitatory Neurotransmission ◽  
Induced Currents ◽  
The Brain

In the brain, AMPA-type glutamate receptors are major postsynaptic receptors at excitatory synapses that mediate fast neurotransmission and synaptic plasticity. α/β-Hydrolase domain-containing 6 (ABHD6), a monoacylglycerol lipase, was previously found to be a component of AMPA receptor macromolecular complexes, but its physiological significance in the function of AMPA receptors (AMPARs) has remained unclear. The present study shows that overexpression of ABHD6 in neurons drastically reduced excitatory neurotransmission mediated by AMPA but not by NMDA receptors at excitatory synapses. Inactivation of ABHD6 expression in neurons by either CRISPR/Cas9 or shRNA knockdown methods significantly increased excitatory neurotransmission at excitatory synapses. Interestingly, overexpression of ABHD6 reduced glutamate-induced currents and the surface expression of GluA1 in HEK293T cells expressing GluA1 and stargazin, suggesting a direct functional interaction between these two proteins. The C-terminal tail of GluA1 was required for the binding between of ABHD6 and GluA1. Mutagenesis analysis revealed a GFCLIPQ sequence in the GluA1 C terminus that was essential for the inhibitory effect of ABHD6. The hydrolase activity of ABHD6 was not required for the effects of ABHD6 on AMPAR function in either neurons or transfected HEK293T cells. Thus, these findings reveal a novel and unexpected mechanism governing AMPAR trafficking at synapses through ABHD6.

scholarly journals Structural basis of trehalose recycling by the ABC transporter LpqY-SugABC

2020 ◽  
Vol 6 (44) ◽  
pp. eabb9833
Author(s):  
Fengjiang Liu ◽  
Jingxi Liang ◽  
Bing Zhang ◽  
Yan Gao ◽  
Xiuna Yang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Abc Transporter ◽  
Abc Transporters ◽  
Unique Feature ◽  
Structural Basis ◽  
Human Pathogens ◽  
Gram Positive Bacteria ◽  
Cryo Electron Microscopy ◽  
Uptake Of Nutrients ◽  
Initial Mode

In bacteria, adenosine 5′-triphosphate (ATP)–binding cassette (ABC) importers are essential for the uptake of nutrients including the nonreducing disaccharide trehalose, a metabolite that is crucial for the survival and virulence of several human pathogens including Mycobacterium tuberculosis. SugABC is an ABC transporter that translocates trehalose from the periplasmic lipoprotein LpqY into the cytoplasm of mycobacteria. Here, we report four high-resolution cryo–electron microscopy structures of the mycobacterial LpqY-SugABC complex to reveal how it binds and passes trehalose through the membrane to the cytoplasm. A unique feature observed in this system is the initial mode of capture of the trehalose at the LpqY interface. Uptake is achieved by a pivotal rotation of LpqY relative to SugABC, moving from an open and accessible conformation to a clamped conformation upon trehalose binding. These findings enrich our understanding as to how ABC transporters facilitate substrate transport across the membrane in Gram-positive bacteria.

scholarly journals Structural basis of SARS-CoV-2 Omicron immune evasion and receptor engagement

2021 ◽  
Author(s):  
Matthew McCallum ◽  
Nadine Czudnochowski ◽  
Laura E Rosen ◽  
Samantha K Zepeda ◽  
John E Bowen ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Monoclonal Antibody ◽  
Crystal Structures ◽  
Immune Evasion ◽  
Marked Reduction ◽  
Structural Basis ◽  
X Ray ◽  
Structural Framework ◽  
Cryo Electron Microscopy ◽  
Antigenic Shift

The SARS-CoV-2 Omicron variant of concern evades antibody mediated immunity with an unprecedented magnitude due to accumulation of numerous spike mutations. To understand the Omicron antigenic shift, we determined cryo-electron microscopy and X-ray crystal structures of the spike and RBD bound to the broadly neutralizing sarbecovirus monoclonal antibody (mAb) S309 (the parent mAb of sotrovimab) and to the human ACE2 receptor. We provide a structural framework for understanding the marked reduction of binding of all other therapeutic mAbs leading to dampened neutralizing activity. We reveal electrostatic remodeling of the interactions within the spike and those formed between the Omicron RBD and human ACE2, likely explaining enhanced affinity for the host receptor relative to the prototypic virus.

scholarly journals Cryo-Electron Microscopy and Biochemical Analysis Offer Insights Into the Effects of Acidic pH, Such as Occur During Acidosis, on the Complement Binding Properties of C-Reactive Protein

2021 ◽  
Vol 12 ◽  
Author(s):  
Dylan P. Noone ◽  
Tijn T. van der Velden ◽  
Thomas H. Sharp
Keyword(s):  
Electron Microscopy ◽  
Biochemical Analysis ◽  
Biochemical Properties ◽  
Structural Basis ◽  
Structural Rearrangements ◽  
C Reactive Protein ◽  
Reactive Protein ◽  
Cryo Electron Microscopy ◽  
Ionic Nature ◽  
The Complement System

The pentraxin family of proteins includes C-reactive protein (CRP), a canonical marker for the acute phase inflammatory response. As compared to normal physiological conditions in human serum, under conditions associated with damage and inflammation, such as acidosis and the oxidative burst, CRP exhibits modulated biochemical properties that may have a structural basis. Here, we explore how pH and ligand binding affect the structure and biochemical properties of CRP. Cryo-electron microscopy was used to solve structures of CRP at pH 7.5 or pH 5 and in the presence or absence of the ligand phosphocholine (PCh), which yielded 7 new high-resolution structures of CRP, including pentameric and decameric complexes. Structures previously derived from crystallography were imperfect pentagons, as shown by the variable angles between each subunit, whereas pentameric CRP derived from cryoEM was found to have C5 symmetry, with subunits forming a regular pentagon with equal angles. This discrepancy indicates flexibility at the interfaces of monomers that may relate to activation of the complement system by the C1 complex. CRP also appears to readily decamerise in solution into dimers of pentamers, which obscures the postulated binding sites for C1. Subtle structural rearrangements were observed between the conditions tested, including a putative change in histidine protonation that may prime the disulphide bridges for reduction and enhanced ability to activate the immune system. Enzyme-linked immunosorbent assays showed that CRP had markedly increased association to the C1 complex and immunoglobulins under conditions associated with acidosis, whilst a reduction in the Ca2+ concentration lowered this pH-sensitivity for C1q, but not immunoglobulins, suggesting different modes of binding. These data suggest a model whereby a change in the ionic nature of CRP and immunological proteins can make it more adhesive to potential ligands without large structural rearrangements.

Sign in / Sign up

Export Citation Format

Share Document