Biology subjects

Ladefoged, L. K.

Publications and source records attributed to Ladefoged, L. K..

4 recordsLinked to original sources

bioRxiv2024

Structural Determinants for Activity of the Antidepressant Vortioxetine at Human and Rodent 5-HT3 receptors

Vortioxetine (VTX) is a recent antidepressant that targets a variety of serotonin receptors. We investigate the drugs molecular mechanism of operation at serotonin 5-HT3 receptors (5-HT3R), which features two mysterious properties: VTX acts differently on rodent and human 5-HT3R; VTX appears to suppress any subsequent response to agonists. Using a combination of cryo-EM, electrophysiology, and molecular dynamics, we show that VTX stabilizes a resting inhibited state of the mouse 5-HT3R and an agonist bound-like state of the human 5-HT3R, in line with the functional profile of the drug. We report four human 5-HT3R structures and show that the human receptor transmembrane domain is intrinsically fragile. We also explain the lack of recovery after VTX administration via a membrane partition mechanism.

biochemistry↗

bioRxiv2022

Potentiation of drug toxicity through virus latency reversal promotes preferential elimination of HIV infected cells

Eliminating latently infected cells is a highly challenging, indispensable step towards the overall cure for HIV/AIDS. We recognized that the unique HIV protease cut site (Phe-Pro) can be reconstructed using a potent toxin, monomethyl auristatin F (MMAF), which features Phe at its C-terminus. We hypothesized that this presents opportunities to design prodrugs that are specifically activated by the HIV protease. To investigate this, a series of MMAF derivatives was synthesized and evaluated in cell culture using latently HIV-infected cells. Cytotoxicity of compounds was enhanced upon latency reversal by up to 11-fold. In a mixed cell population, nanomolar concentrations of the lead compound depleted predominantly the HIV-infected cells and in doing so markedly enriched the pool with the uninfected cells. Despite expectation, mechanism of action of the synthesized toxins was not as HIV protease-specific prodrugs, but likely through the synergy of toxicities between the toxin and the reactivated virus.

pharmacology and toxicology↗

bioRxiv2021

Binding and activation of serotonergic G-protein coupled receptors by the multimodal antidepressant vortioxetine.

G-protein coupled receptors are important pharmacological targets. Despite substantial progress, important questions still remain concerning the details of activation: how can a ligand act as an agonist in one receptor, but as an antagonist in a homologous receptor, and how can agonists activate a receptor despite lacking polar functional groups able to interact with helix 5? Studying vortioxetine, an important multimodal antidepressant drug, may elucidate both questions. Herein, we present a thorough in silico analysis of vortioxetine binding to 5-HT1A, 5-HT1B, and 5-HT7 receptors and compare to available experimental data. We are able to rationalize the differential mode of action of vortioxetine at different receptors, but also, in the case of the 5-HT1A receptor, we observe the initial steps of activation suggesting that interaction with helix 5 does not necessarily require a hydrogen bond as previously suggested. The results extend our current understanding of agonist and antagonist action at GPCRs.

biophysics↗

bioRxiv2020

Beneficent and maleficent effects of cations on bufadienolide binding to Na+,K+-ATPase

Kinetic properties and crystal structures of the Na+,K+-ATPase in complex with cardiotonic steroids (CTS) revealed significant differences between CTS subfamilies (Laursen et al., 2015): beneficial effects of K+ on bufadienolide binding strongly contrasted with K+/cardenolide antagonism. To solve this riddle we applied docking and molecular dynamics simulations of the complexes involving Na+,K+-ATPase, bufadienolides (bufalin, cinobufagin), and ions (K+, Na+, Mg2+). The results revealed that bufadienolide binding is affected by i) electrostatic attraction of the lactone ring by a cation, and ii) the ability of a cation to stabilize and "shape" the site constituted by transmembrane helices of the -subunit (M1-6). The latter effect was due to varying coordination patterns involving amino acid residues from helix bundles M1-4 and M5-10. Substituents on the steroid core of a bufadienolide add to and modify the cation effects. The above rationale is fully consistent with the ion effects on the kinetics of Na+,K+-ATPase/bufadienolide interactions.

biophysics↗