| 1. |
- Pantazis, A., et al.
(författare)
-
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
-
Ingår i: Journal of Physiology. - : Blackwell Publishing Ltd. - 0022-3751 .- 1469-7793.
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 2. |
- Bahira, M., et al.
(författare)
-
A ruthenium dimer complex with a flexible linker slowly threads between DNA bases in two distinct steps
- 2015
-
Ingår i: Nucleic Acids Research. - : Oxford University Press (OUP). - 0305-1048 .- 1362-4962. ; 43:18, s. 8856-8867
-
Tidskriftsartikel (refereegranskat)abstract
- Several multi-component DNA intercalating small molecules have been designed around ruthenium-based intercalating monomers to optimize DNA binding properties for therapeutic use. Here we probe the DNA binding ligand [mu-C-4(cpdppz)(2)(phen)(4)Ru-2](4+), which consists of two Ru(phen)(2)dppz(2+) moieties joined by a flexible linker. To quantify ligand binding, double-stranded DNA is stretched with optical tweezers and exposed to ligand under constant applied force. In contrast to other bis-intercalators, we find that ligand association is described by a two-step process, which consists of fast bimolecular intercalation of the first dppz moiety followed by similar to 10-fold slower intercalation of the second dppz moiety. The second step is rate-limited by the requirement for a DNA-ligand conformational change that allows the flexible linker to pass through the DNA duplex. Based on our measured force-dependent binding rates and ligand-induced DNA elongation measurements, we are able to map out the energy landscape and structural dynamics for both ligand binding steps. In addition, we find that at zero force the overall binding process involves fast association (similar to 10 s), slow dissociation (similar to 300 s), and very high affinity (K-d similar to 10 nM). The methodology developed in this work will be useful for studying the mechanism of DNA binding by other multi-step intercalating ligands and proteins.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Axelsson, Anton, 1991, et al.
(författare)
-
Asymmetric Synthesis of Dihydropyranones with Three Contiguous Stereocenters by an NHC-Catalyzed Kinetic Resolution
- 2021
-
Ingår i: European Journal of Organic Chemistry. - : Wiley. - 1434-193X .- 1099-0690. ; 2021:25, s. 3657-3661
-
Tidskriftsartikel (refereegranskat)abstract
- An oxidative NHC-catalyzed kinetic resolution (KR) of racemic mixtures is presented. The developed reaction furnishes tricyclic dihydropyranones with three contiguous stereocenters in excellent dia- and enantioselectivity, with good-to-moderate yields. Mechanistic studies indicate that the rate-determining step of the reaction is the formation of the Breslow intermediate, while the selectivity determining step occurs later in the mechanism. The presented methodology enables rapid synthesis of complex structures in a single step.
|
|
| 7. |
- Höglund Carlsson, Lotta, et al.
(författare)
-
Prenatal ultrasound and childhood autism : long-term follow-up after a randomized controlled trial of first- vs second-trimester ultrasound
- 2016
-
Ingår i: Ultrasound in Obstetrics and Gynecology. - : John Wiley & Sons. - 0960-7692 .- 1469-0705. ; 48:3, s. 285-288
-
Tidskriftsartikel (refereegranskat)abstract
- Objective: To analyze whether the frequency of autism spectrum disorder (ASD) in a cohort of Swedish children differs between those exposed to ultrasound in the 12th week and those exposed to ultrasound in the 18th week of gestation.Methods: The study cohort consisted of approximately 30 000 children born between 1999 and 2003 to mothers who had been randomized to a prenatal ultrasound examination at either 12 or 18weeks' gestation as part of the framework for a study on nuchal translucency screening. The outcome measure in the present study was the rate of ASD diagnoses among the children. Information on ASD diagnoses was based on data from the Swedish social insurance agency concerning childcare allowance granted for ASD.Results: Between 1999 and 2003, a total of 14 726 children were born to women who underwent a 12-week ultrasound examination and 14 596 to women who underwent an 18-week ultrasound examination. Of these, 181 (1.2%) and 176 (1.2%) children, respectively, had been diagnosed with ASD. There was no difference in ASD frequency between the early and late ultrasound groups.Conclusions: Women subjected to at least one prenatal ultrasound examination at either 12 or 18weeks' gestation had children with similar rates of ASD. However, this result reflects routine care 10-15 years ago in Sweden. Today, higher intensity ultrasound scans are performed more frequently, at earlier stages during pregnancy and for non-medical purposes, implying longer exposure time for the fetus. This change in the use of ultrasound necessitates further follow-up study of the possible effects that high exposure to ultrasound during the gestational period has on the developing brain.
|
|
| 8. |
- Paramanathan, T., et al.
(författare)
-
Mechanically manipulating the DNA threading intercalation rate
- 2008
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 130:12, s. 3752-
-
Tidskriftsartikel (refereegranskat)abstract
- The dumbbell shaped binuclear ruthenium complex ΔΔ-P requires transiently melted DNA in order to thread through the DNA bases and intercalate DNA. Because such fluctuations are rare at room temperature, the binding rates are extremely low in bulk experiments. Here, single DNA molecule stretching is used to lower the barrier to DNA melting, resulting in direct mechanical manipulation of the barrier to DNA binding by the ligand. The rate of DNA threading depends exponentially on force, consistent with theoretical predictions. From the observed force dependence of the binding rate, we demonstrate that only one base pair must be transiently melted for DNA threading to occur. Copyright © 2008 American Chemical Society.
|
|
| 9. |
|
|
| 10. |
|
|
