scholarly journals Kinetic analysis of ASIC1a delineates conformational signaling from proton-sensing domains to the channel gate

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Sabrina Vullo ◽  
Nicolas Ambrosio ◽  
Jan P Kucera ◽  
Olivier Bignucolo ◽  
Stephan Kellenberger
Keyword(s):  
Ion Channels ◽  
Kinetic Analysis ◽  
Conformational Changes ◽  
Transmembrane Helix ◽  
Activation Mechanism ◽  
Pain Sensation ◽  
Channel Activation ◽  
Channel Pore ◽  
Acid Sensing Ion Channels ◽  
Channel Gate

Acid-sensing ion channels (ASICs) are neuronal Na+ channels that are activated by a drop in pH. Their established physiological and pathological roles, involving fear behaviors, learning, pain sensation and neurodegeneration after stroke, make them promising targets for future drugs. Currently, the ASIC activation mechanism is not understood. Here we used voltage-clamp fluorometry (VCF) combined with fluorophore-quencher pairing to determine the kinetics and direction of movements. We show that conformational changes with the speed of channel activation occur close to the gate and in more distant extracellular sites, where they may be driven by local protonation events. Further, we provide evidence for fast conformational changes in a pathway linking protonation sites to the channel pore, in which an extracellular interdomain loop interacts via aromatic residue interactions with the upper end of a transmembrane helix and would thereby open the gate.

scholarly journals Kinetic analysis of ASIC1a delineates conformational signaling from proton-sensing domains to the channel gate

2021 ◽  
Author(s):  
Sabrina Vullo ◽  
Nicolas Ambrosio ◽  
Jan P. Kucera ◽  
Olivier Bignucolo ◽  
Stephan Kellenberger
Keyword(s):  
Molecular Dynamics ◽  
Conformational Changes ◽  
Transmembrane Helix ◽  
Activation Mechanism ◽  
Pain Sensation ◽  
Channel Activation ◽  
Channel Pore ◽  
Acid Sensing Ion Channels ◽  
Channel Gate ◽  
Dynamics Simulations

AbstractAcid-sensing ion channels (ASICs) are neuronal Na+ channels that are activated by a drop in pH. Their established physiological and pathological roles, involving fear behaviors, learning, pain sensation and neurodegeneration after stroke, make them promising targets for future drugs. Currently, the ASIC activation mechanism is not understood. Here we used voltage-clamp fluorometry (VCF) combined with fluorophore-quencher pairing to determine the kinetics and direction of movements. Molecular dynamics simulations were used to further evaluate VCF-predicted movements. We show that conformational changes with the speed of channel activation occur close to the gate and in more distant extracellular sites, where they may be driven by local protonation events. Further, we provide evidence for fast conformational changes in a pathway linking protonation sites to the channel pore, in which an extracellular interdomain loop interacts via aromatic residue interactions with the upper end of a transmembrane helix and would thereby open the gate.

scholarly journals Two residues in the extracellular domain convert a nonfunctional ASIC1 into a proton-activated channel

2010 ◽  
Vol 299 (1) ◽  
pp. C66-C73 ◽  
Author(s):  
Tianbo Li ◽  
Youshan Yang ◽  
Cecilia M. Canessa
Keyword(s):  
Amino Acid ◽  
Conformational Changes ◽  
Transmembrane Helix ◽  
Amino Acid Substitutions ◽  
Fast Kinetics ◽  
Acid Sensing Ion Channels ◽  
Inward Currents ◽  
Mammalian Counterpart ◽  
Opening And Closing ◽  
Kinetics Of

Acid-sensing ion channels (ASICs) are proton-activated sodium channels of the nervous system. Mammals express four ASICs, and orthologs of these genes have been found in all chordates examined to date. Despite a high degree of sequence conservation of all ASICs across species, the response to a given increase in external proton concentration varies markedly: from large and slowly inactivating inward currents to no detectable currents. The underlying bases of this functional variability and whether it stems from differences in proton-binding sites or in structures that translate conformational changes have not been determined yet. We show here that the ASIC1 ortholog of an early vertebrate, lamprey ASIC1, does not respond to protons; however, only two amino acid substitutions for the corresponding ones in rat ASIC1, Q77L and T85L, convert lamprey ASIC1 into a highly sensitive proton-activated channel with apparent H+ affinity of pH50 7.2. Addition of C73H increases the magnitude of the currents by fivefold, and W64R confers desensitization similar to that of the mammalian counterpart. Most amino acid substitutions in these four positions increase the rates of opening and closing the pore, whereas only few, namely, the ones in rat ASIC1, slow the rates. The four residues are located in a contiguous segment made by the β1-β2-linker, β1-strand, and the external segment of the first transmembrane helix. We conclude that the segment thus defined modulates the kinetics of opening and closing the pore and that fast kinetics of desensitization rather than lack of acid sensor accounts for the absence of proton-induced currents in the parent lamprey ASIC1.

scholarly journals Structural model of the open–closed–inactivated cycle of prokaryotic voltage-gated sodium channels

2014 ◽  
Vol 145 (1) ◽  
pp. 5-16 ◽  
Author(s):  
Claire Bagnéris ◽  
Claire E. Naylor ◽  
Emily C. McCusker ◽  
B.A. Wallace
Keyword(s):  
Sodium Channels ◽  
Conformational Changes ◽  
Structural Model ◽  
Transmembrane Helix ◽  
Activation Mechanism ◽  
Excitable Cells ◽  
Voltage Gated ◽  
Recovery Processes ◽  
Voltage Gated Sodium Channels ◽  
Activation Gate

In excitable cells, the initiation of the action potential results from the opening of voltage-gated sodium channels. These channels undergo a series of conformational changes between open, closed, and inactivated states. Many models have been proposed for the structural transitions that result in these different functional states. Here, we compare the crystal structures of prokaryotic sodium channels captured in the different conformational forms and use them as the basis for examining molecular models for the activation, slow inactivation, and recovery processes. We compare structural similarities and differences in the pore domains, specifically in the transmembrane helices, the constrictions within the pore cavity, the activation gate at the cytoplasmic end of the last transmembrane helix, the C-terminal domain, and the selectivity filter. We discuss the observed differences in the context of previous models for opening, closing, and inactivation, and present a new structure-based model for the functional transitions. Our proposed prokaryotic channel activation mechanism is then compared with the activation transition in eukaryotic sodium channels.

scholarly journals Allosteric effect of nanobody binding on ligand-specific active states of the β2-Adrenergic Receptor

2021 ◽  
Author(s):  
Yue Chen ◽  
Oliver Fleetwood ◽  
Sergio Perez-Conesa ◽  
Lucie Delemotte
Keyword(s):  
G Protein ◽  
Conformational Changes ◽  
Adrenergic Receptor ◽  
Partial Agonist ◽  
Transmembrane Helix ◽  
Active State ◽  
Supervised Machine Learning ◽  
Activation Mechanism ◽  
Gpcr Activation ◽  
Loop 2

Nanobody binding stabilizes the active state of G-protein-coupled receptor (GPCR) and modulates its affinity for bound ligands. However, the atomic level basis for this allosteric regulation remains elusive. Here, we investigate the conformational changes induced by the binding of a nanobody (Nb80) on the active-like beta2 adrenergic receptor (beta2AR) via enhanced sampling molecular dynamics simulations. Dimensionality reduction analysis shows that Nb80 stabilizes a highly active state of the beta2AR with a ~14 A outward movement of transmembrane helix 6 and close proximity of transmembrane (TM) helices 5 and 7. This is further supported by the residues located at hotspots located on TMs 5, 6 and 7, as shown by supervised machine learning methods. Besides, ligand-specific subtle differences in the conformations assumed by intercellular loop 2 and extracellular loop 2 are captured from the trajectories of various ligand-bound receptors in the presence of Nb80. Dynamic network analysis further reveals that Nb80 binding can enhance the communication between the binding sites of Nb80 and of the ligand. We identify unique allosteric signal transmission mechanisms between the Nb80-binding site and the extracellular domains in presence of full agonist and G-protein biased partial agonist, respectively. Altogether, our results provide insights into the effect of intracellular binding partners on the GPCR activation mechanism, which could be useful for structure-based drug discovery.

scholarly journals Conformational dynamics and role of the acidic pocket in ASIC pH-dependent gating

2017 ◽  
Vol 114 (14) ◽  
pp. 3768-3773 ◽  
Author(s):  
Sabrina Vullo ◽  
Gaetano Bonifacio ◽  
Sophie Roy ◽  
Niklaus Johner ◽  
Simon Bernèche ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Conformational Dynamics ◽  
Ph Sensing ◽  
Central Channel ◽  
Ph Sensors ◽  
Pain Sensation ◽  
Acid Sensing Ion Channels ◽  
Acidic Residues ◽  
Ph Dependent

Acid-sensing ion channels (ASICs) are proton-activated Na+ channels expressed in the nervous system, where they are involved in learning, fear behaviors, neurodegeneration, and pain sensation. In this work, we study the role in pH sensing of two regions of the ectodomain enriched in acidic residues: the acidic pocket, which faces the outside of the protein and is the binding site of several animal toxins, and the palm, a central channel domain. Using voltage clamp fluorometry, we find that the acidic pocket undergoes conformational changes during both activation and desensitization. Concurrently, we find that, although proton sensing in the acidic pocket is not required for channel function, it does contribute to both activation and desensitization. Furthermore, protonation-mimicking mutations of acidic residues in the palm induce a dramatic acceleration of desensitization followed by the appearance of a sustained current. In summary, this work describes the roles of potential pH sensors in two extracellular domains, and it proposes a model of acidification-induced conformational changes occurring in the acidic pocket of ASIC1a.

Acid-sensing ion channels

2006 ◽  
pp. S100-S101
Author(s):  
S P H Alexander ◽  
A Mathie ◽  
J A Peters
Keyword(s):  
Ion Channels ◽  
Acid Sensing Ion Channels

Acid Sensing Ion Channels (ASICs) und 5-HT-Rezeptoren bei GERD. Untersuchungen zur Genexpression im pharmakologischen Modell

2015 ◽  
Vol 53 (08) ◽  
Author(s):  
A Shcherbokova ◽  
H Abdel-Aziz ◽  
O Kelber ◽  
K Nieber ◽  
G Ulrich-Merzenich
Keyword(s):  
Ion Channels ◽  
Acid Sensing Ion Channels

Acid-Sensing Ion Channels

2020 ◽  
Author(s):  
Stefan Gründer
Keyword(s):  
Nervous System ◽  
Ion Channels ◽  
Excitatory Synapses ◽  
Detailed Characterization ◽  
High Affinity ◽  
Acid Sensing Ion Channels ◽  
Long Time ◽  
Pathological Pain

Acid-sensing ion channels (ASICs) are proton-gated Na+ channels. Being almost ubiquitously present in neurons of the vertebrate nervous system, their precise function remained obscure for a long time. Various animal toxins that bind to ASICs with high affinity and specificity have been tremendously helpful in uncovering the role of ASICs. We now know that they contribute to synaptic transmission at excitatory synapses as well as to sensing metabolic acidosis and nociception. Moreover, detailed characterization of mouse models uncovered an unanticipated role of ASICs in disorders of the nervous system like stroke, multiple sclerosis, and pathological pain. This review provides an overview on the expression, structure, and pharmacology of ASICs plus a summary of what is known and what is still unknown about their physiological functions and their roles in diseases.

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