scholarly journals Cryo-EM structure of the calcium homeostasis modulator 1 channel

2020 ◽  
Vol 6 (29) ◽  
pp. eaba8161
Author(s):  
Yue Ren ◽  
Tianlei Wen ◽  
Zhiqin Xi ◽  
Shunjin Li ◽  
Jing Lu ◽  
...  
Keyword(s):  
Calcium Homeostasis ◽  
Transmembrane Helix ◽  
Atp Release ◽  
Ion Permeation ◽  
Extracellular Loop ◽  
Release Channel ◽  
Dimer Interface ◽  
Cryo Electron Microscopy ◽  
Gating Mechanism ◽  
Oligomeric Assembly

Calcium homeostasis modulator 1 (CALHM1) is a voltage-gated ATP release channel that plays an important role in neural gustatory signaling and the pathogenesis of Alzheimer’s disease. Here, we present a cryo–electron microscopy structure of full-length Ca2+-free CALHM1 from Danio rerio at an overall resolution of 3.1 Å. Our structure reveals an octameric architecture with a wide pore diameter of ~20 Å, presumably representing the active conformation. The overall structure is substantially different from that of the isoform CALHM2, which forms both undecameric hemichannels and gap junctions. The N-terminal small helix folds back to the pore and forms an antiparallel interaction with transmembrane helix 1. Structural analysis revealed that the extracellular loop 1 region within the dimer interface may contribute to oligomeric assembly. A positive potential belt inside the pore was identified that may modulate ion permeation. Our structure offers insights into the assembly and gating mechanism of the CALHM1 channel.

scholarly journals Structure and assembly of calcium homeostasis modulator proteins

2019 ◽  
Author(s):  
Johanna L Syrjanen ◽  
Kevin Michalski ◽  
Tsung-Han Chou ◽  
Timothy Grant ◽  
Shanlin Rao ◽  
...  
Keyword(s):  
Calcium Homeostasis ◽  
Neuronal Excitability ◽  
Dependent Manner ◽  
Transmembrane Helices ◽  
Cryo Electron Microscopy ◽  
Large Pore ◽  
Oligomeric Assembly ◽  
Voltage Dependent ◽  
Bona Fide ◽  
Dynamics Simulations

AbstractBiological membranes of many tissues and organs contain large-pore channels designed to permeate a wide variety of ions and metabolites. Examples include connexin, innexin, and pannexin, which form gap junctions and/or bona fide cell surface channels. The most recently identified large-pore channels are the calcium homeostasis modulators (CALHMs), which permeate ions and ATP in a voltage-dependent manner to control neuronal excitability, taste signaling, and pathologies of depression and Alzheimer’s disease. Despite such critical biological roles, the structures and patterns of oligomeric assembly remain unclear. Here, we reveal the first structures of two CALHMs, CALHM1 and CALHM2, by single particle cryo-electron microscopy, which show novel assembly of the four transmembrane helices into channels of 8-mers and 11-mers, respectively. Furthermore, molecular dynamics simulations suggest that lipids can favorably assemble into a bilayer within the larger CALHM2 pore, but not within CALHM1, demonstrating the potential correlation between pore-size, lipid accommodation, and channel activity.

scholarly journals Gating mechanism of cardiac ryanodine receptor 2 upon calcium ion binding

2020 ◽  
Author(s):  
Takuya Kobayashi ◽  
Akihisa Tsutsumi ◽  
Nagomi Kurebayashi ◽  
Kei Saito ◽  
Masami Kodama ◽  
...  
Keyword(s):  
Ryanodine Receptor ◽  
Heart Diseases ◽  
Atomic Level ◽  
Structural Basis ◽  
Ion Binding ◽  
Release Channel ◽  
Cryo Electron Microscopy ◽  
Gating Mechanism ◽  
Channel Opening ◽  
Cardiac Ryanodine Receptor

AbstractCardiac ryanodine receptor (RyR2) is a large Ca2+ release channel in the sarcoplasmic reticulum and indispensable for excitation-contraction coupling in the heart. RyR2 is activated by Ca2+ and RyR2 mutations have been implicated in severe arrhythmogenic heart diseases. Yet, the structural basis underlying channel opening and how mutations affect the channel remain unknown. Here, we combined high-resolution structures determined by cryo-electron microscopy with quantitative functional analysis of channels carrying various mutations in specific residues. We demonstrated that interactions close to the channel pore are important for stabilizing the channel in the closed state and those in the surrounding regions are essential for channel opening. Our results reveal mechanisms underlying channel opening upon Ca2+ binding and alterations by pathogenic mutations of RyR2 at the atomic level.One Sentence SummaryKey movements and interactions in RyR2 during cardiac Ca2+ channel opening are clarified at the atomic level.

scholarly journals Cryo-EM structures of calcium homeostasis modulator channels in diverse oligomeric assemblies

2020 ◽  
Vol 6 (29) ◽  
pp. eaba8105 ◽  
Author(s):  
Kanae Demura ◽  
Tsukasa Kusakizako ◽  
Wataru Shihoya ◽  
Masahiro Hiraizumi ◽  
Kengo Nomura ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Caenorhabditis Elegans ◽  
Adenosine Triphosphate ◽  
Calcium Homeostasis ◽  
Transmembrane Domain ◽  
Atp Release ◽  
Channel Pore ◽  
Cryo Electron Microscopy ◽  
Chimeric Construct ◽  
Intersubunit Interactions

Calcium homeostasis modulator (CALHM) family proteins are Ca2+-regulated adenosine triphosphate (ATP)–release channels involved in neural functions including neurotransmission in gustation. Here, we present the cryo–electron microscopy (EM) structures of killifish CALHM1, human CALHM2, and Caenorhabditis elegans CLHM-1 at resolutions of 2.66, 3.4, and 3.6 Å, respectively. The CALHM1 octamer structure reveals that the N-terminal helix forms the constriction site at the channel pore in the open state and modulates the ATP conductance. The CALHM2 undecamer and CLHM-1 nonamer structures show the different oligomeric stoichiometries among CALHM homologs. We further report the cryo-EM structures of the chimeric construct, revealing that the intersubunit interactions at the transmembrane domain (TMD) and the TMD–intracellular domain linker define the oligomeric stoichiometry. These findings advance our understanding of the ATP conduction and oligomerization mechanisms of CALHM channels.

scholarly journals Cryo-EM structures of calcium homeostasis modulator channels in diverse oligomeric assemblies

2020 ◽  
Author(s):  
Kanae Demura ◽  
Tsukasa Kusakizako ◽  
Wataru Shihoya ◽  
Masahiro Hiraizumi ◽  
Kengo Nomura ◽  
...  
Keyword(s):  
Calcium Homeostasis ◽  
Transmembrane Domain ◽  
Atp Release ◽  
Subunit Interactions ◽  
Channel Pore ◽  
C Elegans ◽  
Oligomeric Assembly ◽  
Chimeric Construct

AbstractCalcium homeostasis modulator (CALHM) family proteins are Ca2+-regulated ATP-release channels involved in neural functions including neurotransmission in gustation. Here we present the cryo-EM structures of killifish CALHM1, human CALHM2, and C. elegans CLHM-1 at resolutions of 2.66, 3.51, and 3.60 Å, respectively. The CALHM1 octamer structure reveals that the N-terminal helix forms the constriction site at the channel pore in the open state, and modulates the ATP conductance. The CALHM2 undecamer and CLHM-1 nonomer structures show the different oligomeric stoichiometries among CALHM homologs. We further report the cryo-EM structures of the chimeric construct, revealing that the inter-subunit interactions at the transmembrane domain define the oligomeric stoichiometry. These findings advance our understanding of the ATP conduction and oligomerization mechanisms of CALHM channels.One Sentence SummaryCryo-EM structures reveal the ATP conduction and oligomeric assembly mechanisms of CALHM channels.

scholarly journals Structure of the full-length human Pannexin1 channel and insights into its role in pyroptosis

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Sensen Zhang ◽  
Baolei Yuan ◽  
Jordy Homing Lam ◽  
Jun Zhou ◽  
Xuan Zhou ◽  
...  
Keyword(s):  
Md Simulation ◽  
Potential Role ◽  
Md Simulations ◽  
Full Length ◽  
Inflammasome Activation ◽  
Simulation Studies ◽  
Cryo Electron Microscopy ◽  
Gating Mechanism ◽  
Atp Efflux

AbstractPannexin1 (PANX1) is a large-pore ATP efflux channel with a broad distribution, which allows the exchange of molecules and ions smaller than 1 kDa between the cytoplasm and extracellular space. In this study, we show that in human macrophages PANX1 expression is upregulated by diverse stimuli that promote pyroptosis, which is reminiscent of the previously reported lipopolysaccharide-induced upregulation of PANX1 during inflammasome activation. To further elucidate the function of PANX1, we propose the full-length human Pannexin1 (hPANX1) model through cryo-electron microscopy (cryo-EM) and molecular dynamics (MD) simulation studies, establishing hPANX1 as a homo-heptamer and revealing that both the N-termini and C-termini protrude deeply into the channel pore funnel. MD simulations also elucidate key energetic features governing the channel that lay a foundation to understand the channel gating mechanism. Structural analyses, functional characterizations, and computational studies support the current hPANX1-MD model, suggesting the potential role of hPANX1 in pyroptosis during immune responses.

scholarly journals Pannexin-1 Deficient Mice Have an Increased Susceptibility for Atrial Fibrillation and Show a QT-Prolongation Phenotype

2016 ◽  
Vol 38 (2) ◽  
pp. 487-501 ◽  
Author(s):  
Stella Petric ◽  
Sofia Klein ◽  
Lisa Dannenberg ◽  
Tillman Lahres ◽  
Lukas Clasen ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Cardiac Electrophysiology ◽  
Electrophysiological Study ◽  
Atp Release ◽  
Release Channel ◽  
Knock Out ◽  
Pannexin 1 ◽  
Significant Prolongation ◽  
Knock Out Mice

Background/Aims: Pannexin-1 (Panx1) is an ATP release channel that is ubiquitously expressed and coupled to several ligand-gated receptors. In isolated cardiac myocytes, Panx1 forms large conductance channels that can be activated by Ca2+ release from the sarcoplasmic reticulum. Here we characterized the electrophysiological function of these channels in the heart in vivo, taking recourse to mice with Panx1 ablation. Methods: Cardiac phenotyping of Panx1 knock-out mice (Panx1-/-) was performed by employing a molecular, cellular and functional approach, including echocardiography, surface and telemetric ECG recordings with QT analysis, physical stress testing and quantification of heart rate variability. In addition, an in vivo electrophysiological study entailed programmed electrical stimulation using an intracardiac octapolar catheter. Results: Panx1 deficiency results in a higher incidence of AV-block, delayed ventricular depolarisation, significant prolongation of QT- and rate corrected QT-interval and a higher incidence of atrial fibrillation after intraatrial burst stimulation. Conclusion: Panx1 seems to play an important role in murine cardiac electrophysiology and warrants further consideration in the context of hereditary forms of atrial fibrillation.

scholarly journals Unravelling calcium-release channel gating: clues from a hot disease

2004 ◽  
Vol 380 (1) ◽  
pp. e1-e3 ◽  
Author(s):  
Tommie V. McCARTHY ◽  
John J. MACKRILL
Keyword(s):  
Calcium Release ◽  
Distinct Point ◽  
Ryanodine Receptors ◽  
Point Mutations ◽  
Calcium Release Channel ◽  
Release Channel ◽  
Present Evidence ◽  
Gating Mechanism ◽  
Biochemical Journal ◽  
Interdomain Interactions

Ryanodine receptors (RyRs) are a family of intracellular channels that mediate Ca2+ release from the endoplasmic and sarcoplasmic reticulum. More than 50 distinct point mutations in one member of this family, RyR1, cause malignant hyperthermia, a potentially lethal pharmacogenetic disorder of skeletal muscle. These mutations are not randomly distributed throughout the primary structure of RyR1, but are grouped in three discrete clusters. In this issue of the Biochemical Journal, Kobayashi et al. present evidence that interdomain interactions between two of these mutation-enriched regions play a key role in the gating mechanism of RyR1.

scholarly journals Brief structural insight into the allosteric gating mechanism of BK (Slo1) channel

2019 ◽  
Vol 97 (6) ◽  
pp. 498-502
Author(s):  
János Almássy ◽  
Péter P. Nánási
Keyword(s):  
Quaternary Structure ◽  
Short Review ◽  
Bk Channel ◽  
The Past ◽  
Gating Model ◽  
Cryo Electron Microscopy ◽  
Gating Mechanism ◽  
Electrophysiological Measurements ◽  
Structural Insight ◽  
Insight Into

The big conductance Ca2+-dependent K+ channel, also known as BK, MaxiK, Slo1, or KCa1.1, is a ligand- and voltage-gated K+ channel. Although structure-function studies of the past decades, involving mutagenesis and electrophysiological measurements, revealed fine details of the mechanism of BK channel gating, the exact molecular details remained unknown until the quaternary structure of the protein has been solved at a resolution of 3.5 Å using cryo-electron microscopy. In this short review, we are going to summarize these results and interpret the gating model of the BK channel in the light of the recent structural results.

scholarly journals ATP triggers macropinocytosis that internalizes and is regulated by PANX1

2020 ◽  
Author(s):  
Andrew K.J. Boyce ◽  
Emma van der Slagt ◽  
Juan C. Sanchez-Arias ◽  
Leigh Anne Swayne
Keyword(s):  
Neuroblastoma Cells ◽  
Atp Release ◽  
Surface Proteins ◽  
Cell Area ◽  
Release Channel ◽  
Cross Sectional ◽  
Pannexin 1 ◽  
Disease States ◽  
Cellular Area ◽  
Area Expansion

ABSTRACTMacropinocytosis is an endocytic process that allows cells to respond to changes in their environment by internalizing nutrients and cell surface proteins, as well as modulating cell size. Here, we identify that adenosine triphosphate (ATP) triggers macropinocytosis in murine neuroblastoma cells, thereby internalizing the ATP release channel pannexin 1 (PANX1) while concurrently increasing cross-sectional cellular area. Amiloride, a potent inhibitor of macropinocytosis-associated GTPases, abolished ATP-induced PANX1 internalization and cell area expansion. Transient expression of the GTP-hydrolysis resistant GTPase ARF6 Q67L led to increased PANX1 internalization and increased cell area equivalent to levels seen with ATP stimulation. Mutation of an extracellular tryptophan (W74) in PANX1 abolished ATP-evoked cell area enlargement suggesting that PANX1 regulates this form of macropinocytosis. This novel role of PANX1 in macropinocytosis could be particularly important for disease states implicating PANX1, such as cancer, where ATP can act as a purinergic regulator of cell growth/metastasis and as a supplementary energy source following internalization.

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