Biology subjects

Roscioni, A.

Publications and source records attributed to Roscioni, A..

4 recordsLinked to original sources

bioRxiv2026

Molecular mechanism of partially open Kv7.2 gate stabilization by gain-of-function variants

Gain-of-function (GoF) variants in the Kv7.2 channel are associated with a clinically relevant subset of neurodevelopmental disorders. While most GoF substitutions identified so far affect the voltage-sensing domain, we recently described three mutations in the intracellular-facing activation gate (AG), G313S, A317T, and L318V. Electrophysiological recordings showed that these variants increase macroscopic current density and enhance channel open probability. Consistently, molecular dynamics (MD) simulations revealed that they hinder complete channel closure by destabilizing the closed AG and increasing hydration of the central cavity (CC). Whether this partially open conformation can support K+ permeation, however, remained an open question. Here, we combined long-timescale atomistic simulations and simulations with applied electric fields to evaluate the stability of these mutant-associated AG states over longer timescales and their functional relevance. In new trajectories, all three substitutions consistently shifted the closed intracellular gate toward a widened, water-accessible conformation, accompanied by increased CC hydration. We then assessed the functional significance of this partially open state by simulating the A317T channel under applied electric fields. The conformation supported K+ translocation, whereas the closed WT pore remained impermeable under all tested voltages. When simulations were started from open channel conformations, both WT and A317T conducted K+ ions, indicating that the main effect of the substitution is to destabilize closure of the intracellular gate rather than to alter the fully conductive open state. Together, these data show that AG GoF variants can generate an intermediate gate conformation that permits ion permeation, providing a mechanistic link between mutant-induced pore remodeling and Kv7.2 dysfunction in KCNQ2-related disease.

biophysics↗

bioRxiv2026

A CYFIP1-Inspired Peptidomimetic Modulates eIF4E-Dependent Translational Control in Cancer and Neurodevelopmental Disorders

The eukaryotic translation initiation factor 4E (eIF4E) is a central regulator of cap-dependent translation and a compelling pharmacological target in disorders marked by protein synthesis dysregulation, including cancer and Fragile X Syndrome (FXS). Among endogenous eIF4E regulators, the CYFIP1-eIF4E interaction is uniquely selective, offering a framework for designing targeted translation modulators. Here, we report Cy-9B, a rationally engineered, stapled peptidomimetic derived from CYFIP1 that binds eIF4E, disrupts eIF4E-eIF4G complex, and suppresses cap-dependent translation. Enhanced-sampling free-energy simulations reveal that Cy-9B engages eIF4E through a non-canonical binding mode. Cy-9B exhibits drug-like properties, including high proteolytic stability and nanomolar affinity. Functionally, Cy-9B inhibits lung cancer cell proliferation, migration, and invasion. In neurodevelopmental disease models, Cy-9B partially normalizes excessive translation in FXS hippocampal neurons and rescues social behavior deficits in a Cyfip1 haploinsufficient Drosophila melanogaster model, restoring wild-type-like performance. Cy-9B emerges as a first-in-class therapeutic candidate for disorders sharing translational dysregulation, highlighting targeted modulation of eIF4E as a broadly applicable and physiologically compatible therapeutic strategy.

biochemistry↗

bioRxiv2025

Ligand-Induced Structural Dynamics Drive Allosteric Regulation of Translation Initiation Factor eIF4E

The eukaryotic initiation factor 4E (eIF4E) governs cap-dependent translation, and its dysregulation contributes both to cancer and neurological disorders, making it an attractive target for therapeutic intervention. Among the few small-molecule inhibitors developed, 4EGI-1 and its analogue i4EG-BiP have shown promise in cellular and preclinical models. These compounds disrupt eIF4Es interaction with its partner eIF4G while enhancing binding to its negative regulators, the 4E-binding proteins (4E-BPs). Despite their chemical similarity and overlapping functional effects, structural data suggest the two ligands engage different regions of eIF4E, lateral for 4EGI-1 and frontal for i4EG-BiP, raising questions about the basis of their shared activity. Here, we integrate molecular simulations, site-directed mutagenesis, and fluorescence binding assays to elucidate the mechanism of action of both ligands. Funnel metadynamics free-energy calculations reveal that the frontal binding mode is thermodynamically preferred for both compounds. Furthermore, we demonstrate that the conformational rearrangement induced by frontal binding selectively promotes 4E-BP1 over eIF4G association, explaining their common allosteric regulatory effect. These findings reconcile divergent structural observations and highlight how ligand-induced dynamics can be exploited to reprogram eIF4E interactions, offering a framework for next-generation therapeutics targeting dysregulated translation.

molecular biology↗

bioRxiv2024

CONSTITUTIVE OPENING OF THE Kv7.2 PORE ACTIVATION GATE CAUSES KCNQ2-DEVELOPMENTAL ENCEPHALOPATHY

Pathogenic variants in KCNQ2 encoding for Kv7.2 voltage-gated potassium channel subunits cause developmental encephalopathies (KCNQ2-encephalopathies), both with and without epilepsy. We herein describe the clinical, in vitro and in silico features of two encephalopathy-causing variants (A317T, L318V) in Kv7.2 affecting two consecutive residues in the S6 activation gate undergoing large structural rearrangements during pore opening. Currents through these mutant channels displayed increased density, hyperpolarizing shifts in activation gating, and insensitivity to phosphatidylinositol 4,5-bisphosphate (PIP2), a critical regulator of Kv7 channel function; all these features are consistent with a strong gain-of-function effect. An increase in single-channel open probability, with no change in membrane abundance or single-channel conductance, was responsible for the observed gain-of-function effects. All-atoms Molecular Dynamics simulations revealed that the mutations widened the inner pore gate and stabilized a constitutively open channel configuration in the closed state, with minimal effects on the open conformation. Thus, a PIP2-independent stabilization of the inner pore gate open configuration is a novel molecular pathogenetic mechanism for KCNQ2-developmental encephalopathies.

biophysics↗