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- Mínguez‐Viñas, Teresa, et al.
(author)
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Two epilepsy‐associated variants in KCNA2 (KV1.2) at position H310 oppositely affect channel functional expression
- 2023
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In: Journal of Physiology. - : WILEY. - 0022-3751 .- 1469-7793. ; 601:23, s. 5367-5389
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Journal article (peer-reviewed)abstract
- Two KCNA2 variants (p.H310Y and p.H310R) were discovered in paediatric patients with epilepsy and developmental delay. KCNA2 encodes KV1.2-channel subunits, which regulate neuronal excitability. Both gain and loss of KV1.2 function cause epilepsy, precluding the prediction of variant effects; and while H310 is conserved throughout the KV-channel superfamily, it is largely understudied. We investigated both variants in heterologously expressed, human KV1.2 channels by immunocytochemistry, electrophysiology and voltage-clamp fluorometry. Despite affecting the same channel, at the same position, and being associated with severe neurological disease, the two variants had diametrically opposite effects on KV1.2 functional expression. The p.H310Y variant produced ‘dual gain of function’, increasing both cell-surface trafficking and activity, delaying channel closure. We found that the latter is due to the formation of a hydrogen bond that stabilizes the active state of the voltage-sensor domain. Additionally, H310Y abolished ‘ball and chain’ inactivation of KV1.2 by KVβ1 subunits, enhancing gain of function. In contrast, p.H310R caused ‘dual loss of function’, diminishing surface levels by multiple impediments to trafficking and inhibiting voltage-dependent channel opening. We discuss the implications for KV-channel biogenesis and function, an emergent hotspot for disease-associated variants, and mechanisms of epileptogenesis.
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| 2. |
- Bittmann, Simon F., et al.
(author)
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Ultrafast ring-opening and solvent-dependent product relaxation of photochromic spironaphthopyran
- 2019
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In: Physical Chemistry, Chemical Physics - PCCP. - : ROYAL SOC CHEMISTRY. - 1463-9076 .- 1463-9084. ; 21:33, s. 18119-18127
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Journal article (peer-reviewed)abstract
- The ultrafast dynamics of unsubstituted spironaphthopyran (SNP) were investigated using femtosecond transient UV and visible absorption spectroscopy in three different solvents and by semi-classical nuclear dynamics simulations. The primary ring-opening of the pyran unit was found to occur in 300 fs yielding a non-planar intermediate in the first singlet excited state (S-1). Subsequent planarisation and relaxation to the product ground state proceed through barrier crossing on the S-1 potential energy surface (PES) and take place within 1.1 ps after excitation. Simulations show that more than 90% of the trajectories involving C-O bond elongation lead to the planar, open-ring product, while relaxation back to the S-0 of the closed-ring form is accompanied by C-N elongation. All ensuing spectral dynamics are ascribed to vibrational relaxation and thermalisation of the product with a time constant of 13 ps. The latter shows dependency on characteristics of the solvent with solvent relaxation kinetics playing a role.
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| 3. |
- Felker, G. Michael, et al.
(author)
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Assessment of Omecamtiv Mecarbil for the Treatment of Patients With Severe Heart Failure A Post Hoc Analysis of Data From the GALACTIC-HF Randomized Clinical Trial
- 2022
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In: JAMA cardiology. - : AMER MEDICAL ASSOC. - 2380-6583 .- 2380-6591. ; 7:1, s. 26-34
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Journal article (peer-reviewed)abstract
- IMPORTANCE Heart failure with reduced ejection fraction is a progressive clinical syndrome, and many patients condition worsen over time despite treatment. Patients with more severe disease are often intolerant of available medical therapies. OBJECTIVE To evaluate the efficacy and safety of omecamtiv mecarbil for the treatment of patients with severe heart failure (HF) enrolled in the Global Approach to Lowering Adverse Cardiac Outcomes Through Improving Contractility in Heart Failure (GALACTIC-HF) randomized clinical trial. DESIGN, SETTING, AND PARTICIPANTS The GALACTIC-HF study was a global double-blind, placebo-controlled phase 3 randomized clinical trial that was conducted at multiple centers between January 2017 and August 2020. A total of 8232 patients with symptomatic HF (defined as New York Heart Association symptom class II-IV) and left ventricular ejection fraction of 35% or less were randomized to receive omecamtiv mecarbil or placebo and followed up for a median of 21.8 months (range, 15.4-28.6 months). The current post hoc analysis evaluated the efficacy and safety of omecamtiv mecarbil therapy among patients classified as having severe HF compared with patients without severe HF. Severe HF was defined as the presence of all of the following criteria: New York Heart Association symptom class III to IV, left ventricular ejection fraction of 30% or less, and hospitalization for HF within the previous 6 months. INTERVENTIONS Participants were randomized at a 1:1 ratio to receive either omecamtiv mecarbil or placebo. MAIN OUTCOMES AND MEASURES The primary end point was time to first HF event or cardiovascular (CV) death. Secondary end points included time to CV death and safety and tolerability. RESULTS Among 8232 patients enrolled in the GALACTIC-HF clinical trial, 2258 patients (27.4%; mean [SD] age, 64.5 [11.6] years; 1781 men [78.9%]) met the specified criteria for severe HF. Of those, 1106 patients were randomized to the omecamtiv mecarbil group and 1152 to the placebo group. Patients with severe HF who received omecamtiv mecarbil experienced a significant treatment benefit for the primary end point (hazard ratio [HR], 0.80; 95% CI, 0.71-0.90), whereas patients without severe HF had no significant treatment benefit (HR, 0.99; 95% CI, 0.91-1.08; P = .005 for interaction). For CV death, the results were similar (HR for patients with vs without severe HF: 0.88 [95% CI, 0.75-1.03] vs 1.10 [95% CI, 0.97-1.25]; P = .03 for interaction). Omecamtiv mecarbil therapy was well tolerated in patients with severe HF, with no significant changes in blood pressure, kidney function, or potassium level compared with placebo. CONCLUSIONS AND RELEVANCE In this post hoc analysis of data from the GALACTIC-HF clinical trial, omecamtiv mecarbil therapy may have provided a clinically meaningful reduction in the composite end point of time to first HF event or CV death among patients with severe HF. These data support a potential role of omecamtiv mecarbil therapy among patients for whom current treatment options are limited. (C) 2021 American Medical Association. All rights reserved.
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