| 1. |
- Pantazis, A., et al.
(author)
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Tracking the motion of the KV1.2 voltage sensor reveals the molecular perturbations caused by a de novo mutation in a case of epilepsy
- 2020
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In: Journal of Physiology. - : Blackwell Publishing Ltd. - 0022-3751 .- 1469-7793.
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Journal article (peer-reviewed)abstract
- Key points: KV1.2 channels, encoded by the KCNA2 gene, regulate neuronal excitability by conducting K+ upon depolarization. A new KCNA2 missense variant was discovered in a patient with epilepsy, causing amino acid substitution F302L at helix S4, in the KV1.2 voltage-sensing domain. Immunocytochemistry and flow cytometry showed that F302L does not impair KCNA2 subunit surface trafficking. Molecular dynamics simulations indicated that F302L alters the exposure of S4 residues to membrane lipids. Voltage clamp fluorometry revealed that the voltage-sensing domain of KV1.2-F302L channels is more sensitive to depolarization. Accordingly, KV1.2-F302L channels opened faster and at more negative potentials; however, they also exhibited enhanced inactivation: that is, F302L causes both gain- and loss-of-function effects. Coexpression of KCNA2-WT and -F302L did not fully rescue these effects. The proband's symptoms are more characteristic of patients with loss of KCNA2 function. Enhanced KV1.2 inactivation could lead to increased synaptic release in excitatory neurons, steering neuronal circuits towards epilepsy. Abstract: An exome-based diagnostic panel in an infant with epilepsy revealed a previously unreported de novo missense variant in KCNA2, which encodes voltage-gated K+ channel KV1.2. This variant causes substitution F302L, in helix S4 of the KV1.2 voltage-sensing domain (VSD). F302L does not affect KCNA2 subunit membrane trafficking. However, it does alter channel functional properties, accelerating channel opening at more hyperpolarized membrane potentials, indicating gain of function. F302L also caused loss of KV1.2 function via accelerated inactivation onset, decelerated recovery and shifted inactivation voltage dependence to more negative potentials. These effects, which are not fully rescued by coexpression of wild-type and mutant KCNA2 subunits, probably result from the enhancement of VSD function, as demonstrated by optically tracking VSD depolarization-evoked conformational rearrangements. In turn, molecular dynamics simulations suggest altered VSD exposure to membrane lipids. Compared to other encephalopathy patients with KCNA2 mutations, the proband exhibits mild neurological impairment, more characteristic of patients with KCNA2 loss of function. Based on this information, we propose a mechanism of epileptogenesis based on enhanced KV1.2 inactivation leading to increased synaptic release preferentially in excitatory neurons, and hence the perturbation of the excitatory/inhibitory balance of neuronal circuits.
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| 2. |
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| 3. |
- Fleetwood, Oliver, et al.
(author)
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Molecular Insights from Conformational Ensembles via Machine Learning
- 2020
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In: Biophysical Journal. - : Biophysical Society. - 0006-3495 .- 1542-0086. ; 118:3, s. 765-780
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Journal article (peer-reviewed)abstract
- Biomolecular simulations are intrinsically high dimensional and generate noisy data sets of ever-increasing size. Extracting important features from the data is crucial for understanding the biophysical properties of molecular processes, but remains a big challenge. Machine learning (ML) provides powerful dimensionality reduction tools. However, such methods are often criticized as resembling black boxes with limited human-interpretable insight. We use methods from supervised and unsupervised ML to efficiently create interpretable maps of important features from molecular simulations. We benchmark the performance of several methods, including neural networks, random forests, and principal component analysis, using a toy model with properties reminiscent of macromolecular behavior. We then analyze three diverse biological processes: conformational changes within the soluble protein calmodulin, ligand binding to a G protein-coupled receptor, and activation of an ion channel voltage-sensor domain, unraveling features critical for signal transduction, ligand binding, and voltage sensing. This work demonstrates the usefulness of ML in understanding biomolecular states and demystifying complex simulations.
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| 4. |
- Fransson, Eleonor I, et al.
(author)
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Job strain and the risk of stroke : an individual-participant data meta-analysis
- 2015
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In: Stroke. - 0039-2499 .- 1524-4628. ; 46:2, s. 557-559
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Journal article (peer-reviewed)abstract
- BACKGROUND AND PURPOSE: Psychosocial stress at work has been proposed to be a risk factor for cardiovascular disease. However, its role as a risk factor for stroke is uncertain.METHODS: We conducted an individual-participant-data meta-analysis of 196 380 males and females from 14 European cohort studies to investigate the association between job strain, a measure of work-related stress, and incident stroke.RESULTS: In 1.8 million person-years at risk (mean follow-up 9.2 years), 2023 first-time stroke events were recorded. The age- and sex-adjusted hazard ratio for job strain relative to no job strain was 1.24 (95% confidence interval, 1.05;1.47) for ischemic stroke, 1.01 (95% confidence interval, 0.75;1.36) for hemorrhagic stroke, and 1.09 (95% confidence interval, 0.94;1.26) for overall stroke. The association with ischemic stroke was robust to further adjustment for socioeconomic status.CONCLUSION: Job strain may be associated with an increased risk of ischemic stroke, but further research is needed to determine whether interventions targeting job strain would reduce stroke risk beyond existing preventive strategies.
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| 5. |
- Kang, Po Wei, et al.
(author)
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Calmodulin acts as a state-dependent switch to control a cardiac potassium channel opening
- 2024
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Other publication (other academic/artistic)abstract
- Calmodulin (CaM) and PIP2 are potent regulators of the voltage-gated potassium channel KCNQ1 (KV7.1), which conducts the IKs current important for repolarization of cardiac action potentials. Although cryo-EM structures revealed intricate interactions between the KCNQ1 voltage-sensing domain (VSD), CaM, and PIP2, the functional consequences of these interactions remain unknown. Here, we show that CaM-VSD interactions act as a state-dependent switch to control KCNQ1 pore opening. Combined electrophysiology and molecular dynamics network analysis suggest that VSD transition into the fully-activated state allows PIP2 to compete with CaM for binding to VSD, leading to the conformational change that alters the VSD-pore coupling. We identify a motif in the KCNQ1 cytosolic domain which works downstream of CaM-VSD interactions to facilitate the conformational change. Our findings suggest a gating mechanism that integrates PIP2 and CaM in KCNQ1 voltage-dependent activation, yielding insights into how KCNQ1 gains the phenotypes critical for its function in the heart.
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| 6. |
- Kang, Po Wei, et al.
(author)
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Calmodulin acts as a state-dependent switch to control a cardiac potassium channel opening
- 2020
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In: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 6:50
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Journal article (peer-reviewed)abstract
- Calmodulin (CaM) and phosphatidylinositol 4,5-bisphosphate (PIP2) are potent regulators of the voltage-gated potassium channel KCNQ1 (K(v)7.1), which conducts the cardiac I-Ks current. Although cryo-electron microscopy structures revealed intricate interactions between the KCNQ1 voltage-sensing domain (VSD), CaM, and PIP2, the functional consequences of these interactions remain unknown. Here, we show that CaM-VSD interactions act as a state-dependent switch to control KCNQ1 pore opening. Combined electrophysiology and molecular dynamics network analysis suggest that VSD transition into the fully activated state allows PIP 2 to compete with CaM for binding to VSD. This leads to conformational changes that alter VSD-pore coupling to stabilize open states. We identify a motif in the KCNQ1 cytosolic domain, which works downstream of CaM-VSD interactions to facilitate the conformational change. Our findings suggest a gating mechanism that integrates PIP2 and CaM in KCNQ1 voltage-dependent activation, yielding insights into how KCNQ1 gains the phenotypes critical for its physiological function.
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| 10. |
- Pantazis, Antonios, et al.
(author)
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Tracking the motion of the K(V)1.2 voltage sensor reveals the molecular perturbations caused by ade novomutation in a case of epilepsy
- 2020
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In: Journal of Physiology. - : WILEY. - 0022-3751 .- 1469-7793. ; 598:22, s. 5245-5269
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Journal article (peer-reviewed)abstract
- Key points K(V)1.2 channels, encoded by theKCNA2gene, regulate neuronal excitability by conducting K(+)upon depolarization. A newKCNA2missense variant was discovered in a patient with epilepsy, causing amino acid substitution F302L at helix S4, in the K(V)1.2 voltage-sensing domain. Immunocytochemistry and flow cytometry showed that F302L does not impair KCNA2 subunit surface trafficking. Molecular dynamics simulations indicated that F302L alters the exposure of S4 residues to membrane lipids. Voltage clamp fluorometry revealed that the voltage-sensing domain of K(V)1.2-F302L channels is more sensitive to depolarization. Accordingly, K(V)1.2-F302L channels opened faster and at more negative potentials; however, they also exhibited enhanced inactivation: that is, F302L causes both gain- and loss-of-function effects. Coexpression of KCNA2-WT and -F302L did not fully rescue these effects. The probands symptoms are more characteristic of patients with loss ofKCNA2function. Enhanced K(V)1.2 inactivation could lead to increased synaptic release in excitatory neurons, steering neuronal circuits towards epilepsy. An exome-based diagnostic panel in an infant with epilepsy revealed a previously unreportedde novomissense variant inKCNA2, which encodes voltage-gated K(+)channel K(V)1.2. This variant causes substitution F302L, in helix S4 of the K(V)1.2 voltage-sensing domain (VSD). F302L does not affect KCNA2 subunit membrane trafficking. However, it does alter channel functional properties, accelerating channel opening at more hyperpolarized membrane potentials, indicating gain of function. F302L also caused loss of K(V)1.2 function via accelerated inactivation onset, decelerated recovery and shifted inactivation voltage dependence to more negative potentials. These effects, which are not fully rescued by coexpression of wild-type and mutant KCNA2 subunits, probably result from the enhancement of VSD function, as demonstrated by optically tracking VSD depolarization-evoked conformational rearrangements. In turn, molecular dynamics simulations suggest altered VSD exposure to membrane lipids. Compared to other encephalopathy patients withKCNA2mutations, the proband exhibits mild neurological impairment, more characteristic of patients withKCNA2loss of function. Based on this information, we propose a mechanism of epileptogenesis based on enhanced K(V)1.2 inactivation leading to increased synaptic release preferentially in excitatory neurons, and hence the perturbation of the excitatory/inhibitory balance of neuronal circuits.
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