Biology subjects

MacKerell, A. D.

Publications and source records attributed to MacKerell, A. D..

4 recordsLinked to original sources

bioRxiv2025

Drude SILCS-Nucleic: Harnessing Explicit Electronic Polarization in Targeting RNA and DNA for Drug Design

The growing interest in nucleic acids as therapeutic targets has prompted the devel-opment of novel computational methods to facilitate drug discovery. In this study, we extend the Site Identification by Ligand Competitive Saturation (SILCS) methodology to characterize ligand-nucleic acid interactions using the Drude polarizable force field. We demonstrate the ability of the Drude force field to better model solute-nucleic acid interactions, resulting in improved identification of known binding sites and ligand binding favorability predictions across a diverse set of nucleic acid structures. This new workflow addresses limitations in previous SILCS studies by exploiting the en-hanced sampling of solutes in the original SILCS-RNA workflow, accurately modeling the interactions of charged species, and improving solute sampling in minor groove binding sites. These results establish this Drude-based SILCS workflow as a valuable tool for structure-based drug design targeting nucleic acids and offer insights into solute preferences that can guide rational ligand design.

biophysics↗

bioRxiv2025

Prediction of TdP Arrhythmia Risk Through Molecular Simulations of Conformation-specific Drug Interactions with the hERG K+, NaV1.5, and CaV1.2 Channels

Unintended block of cardiac ion channels, particularly hERG (KV11.1), remains a key concern in drug development as disruption of ion channel function can lead to deadly arrhythmia. To assess proarrhythmic risk, we investigated how drugs interact with hERG in its open and inactivated states and whether drug interactions with other cardiac channels like NaV1.5 and CaV1.2 mitigate that risk. Using cryo-EM structures, we modeled open and inactivated conformations of these channels with Rosetta and AlphaFold. We then applied Site Identification by Ligand Competitive Saturation (SILCS), a physics-based pre-computed ensemble docking method, to predict drug binding affinities. SILCS leverages molecular simulation-generated free energy maps for high-throughput docking against hydrated lipid bilayer-embedded ion channel models. Bayesian machine learning was used to refine SILCS scoring using experimental IC50 values from 69 known hERG blockers outperforming Schrodinger Glide, AutoDock Vina, and OpenEye FRED drug docking predictions. Computed drug binding affinities for hERG and CaV1.2 channels were used to train machine learning models that successfully classified around 300 drugs from the CredibleMeds database. Cationic nitrogen SILCS fragment free energy scores were found to be top physical properties that are predictive of drug-induced Torsades de Pointes (TdP) arrhythmia risk. This approach, which relies on the predicted binding free energies and predicted physical properties of drugs rather than the chemical structure of the drugs themselves as features could be extended to facilitate the design of new drugs where rapid assessment of arrhythmia risk can be performed prior to experimental testing.

biophysics↗

bioRxiv2024

The mammalian SKI complex is a broad-spectrum antiviral drug target that upregulates cellular cholesterol to inhibit viral replication

There is a need for the development of broad-spectrum antiviral compounds that can act as first line therapeutic countermeasures to emerging viral infections. Host-directed approaches present a promising avenue of development and carry the benefit of mitigating risks of viral escape mutants. We have previously found the SKI (super killer) complex to be a broad-spectrum, host-target with our lead compound ("UMB18") showing activity against influenza A virus, coronaviruses, and filoviruses. The SKI complex is a cytosolic RNA helicase and we previously found that UMB18 inhibited viral RNA production but did not further define the mechanism. Here, we demonstrate that UMB18 directly binds to SKIC8 of the SKI complex and through transcriptomic analysis of UMB18 treated A549 cells revealed an upregulation of genes in the mevalonate pathway which drives cholesterol synthesis. Further investigation validated the genetic upregulation and confirmed an increase in total cellular cholesterol. This upregulation was dependent on the sterol regulatory element binding proteins (SREBPs) and their regulator SCAP, the major regulators for cholesterol and fatty acid synthesis. Depletion of the SREBPs or SCAP with siRNA, or extraction of cholesterol with methyl {beta}-cyclodextrin attenuated UMB18 antiviral activity, emphasizing the role of increased cholesterol synthesis in this mechanism of action. Our findings further define the antiviral mechanism of a developmental host-directed therapeutic approach with broad applicability against emerging viral pathogens. Author SummaryThe COVID-19 pandemic has underscored the urgent need for effective countermeasures to novel and emerging viral pathogens. Our research presented here builds upon our previously published data on an experimental novel antiviral compound termed UMB18. We have found this compound capable of inhibiting replication of influenza A virus, coronaviruses and the filoviruses Marburg and Ebola virus, but did not fully define a mechanism of action. In this work, we demonstrate that UMB18 exerts antiviral activity by modulating cellular cholesterol levels. By targeting the SKI complex, UMB18 triggers an increase in endogenous cellular cholesterol which disrupts the fine balance viruses rely on for efficient infection. We demonstrate that this mechanism inhibits replication of SARS-CoV-2, revealing a previously undescribed host-directed strategy for antiviral intervention. These findings highlight UMB18s potential as a broad-spectrum antiviral agent and pave the way for further research into its mechanism and therapeutic applications, offering a promising avenue for development of antiviral countermeasures to current, novel and emerging pathogens.

microbiology↗

bioRxiv2019

Structure of the cell-binding component of the Clostridium difficile binary toxin reveals a novel macromolecular assembly

Targeting Clostridium difficile infection (CDI) is challenging because treatment options are limited, and high recurrence rates are common. One reason for this is that hypervirulent CDI often has a binary toxin termed the C. difficile toxin (CDT), in addition to the enterotoxins TsdA and TsdB. CDT has an enzymatic component, termed CDTa, and a pore-forming or delivery subunit termed CDTb. CDTb was characterized here using a combination of single particle cryoEM, X-ray crystallography, NMR, and other biophysical methods. In the absence of CDTa, two novel di-heptamer structures for activated CDTb (aCDTb; 1.0 MDa) were solved at atomic resolution including a symmetric (SymCDTb; 3.14 [A]) and an asymmetric form (AsymCDTb; 2.84 [A]). Roles played by two receptor-binding domains of aCDTb were of particular interest since RBD1 lacks sequence homology to any other known toxin, and the RBD2 domain is completely absent in other well-studied heptameric toxins (i.e. anthrax). For AsymCDTb, a novel Ca2+ binding site was discovered in RBD1 that is important for its stability, and RBD2 was found to be critical for host cell toxicity and the novel di-heptamer fold for both forms of aCDTb. Together, these studies represent a starting point for structure-based drug-discovery strategies to targeting CDT in the most severe strains of CDI. SIGNIFICANCE STATEMENTThere is a high burden from C. difficile infection (CDI) throughout the world, and the Center for Disease Control (CDC) reports more than 500,000 cases annually in the United States, resulting in an estimated 15,000 deaths. In addition to the large clostridial toxins, TcdA/TcdB, a third C. difficile binary toxin (CDT) is associated with the most serious outbreaks of drug resistant CDI in the 21st century. Here, structural biology and biophysical approaches were used to characterize the cell binding component of CDT, termed CDTb, at atomic resolution. Surprisingly, two novel structures were solved from a single sample that help to explain the molecular underpinnings of C. difficile toxicity. These structures will also be important for targeting this human pathogen via structure-based therapeutic design methods.

biophysics↗