Biology subjects

Miceli, F.

Publications and source records attributed to Miceli, F..

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↗

bioRxiv2025

KCNQ2 Loss-of-Function variants disrupt neuronal maturation via early hyperexcitability followed by maladaptive network remodeling

Loss-of-function (LOF) variants in the potassium channel subunit KCNQ2 cause a spectrum of neonatal epilepsies from self-limiting familial neonatal epilepsy (SeLFNE) to severe developmental and epileptic encephalopathy (DEE). To dissect the developmental consequences of KCNQ2 LOF, we conducted a longitudinal and multimodal comparative analysis in a human neuronal model generated from patients with KCNQ2-DEE and KCNQ2-SeLFNE. KCNQ2-LOF induced a biphasic network dysfunction, with early Kv7-driven hyperexcitability rescued by acute Retigabine (RTG) treatment, followed by maladaptive remodeling in the opposite direction. Transcriptomic analysis mirrored this biphasic dynamic trajectory, revealing an initial upregulation followed by a subsequent downregulation of synaptic genes. Structural analysis showed a steeper decline in presynaptic density alongside a distal shift in the axon initial segment (AIS) throughout maturation, and impaired AIS plasticity at later stages. Overall, KCNQ2-LOF disrupts human neuronal maturation through dynamic, biphasic changes in function, gene expression and structure, offering insights into disease mechanisms and therapeutic options.

neuroscience↗

bioRxiv2025

Two-step voltage-sensor activation of the human KV7.4 channel and effect of a deafness-associated mutation

Voltage-gated, potassium-selective KV7.4 channels are expressed in the inner ear and are crucial for hair-cell function and survival. Loss-of-function variants of KCNQ4, the gene encoding KV7.4-channel subunits, cause non-syndromic progressive hearing loss (DFNA2). KV7.4 opening requires a voltage-dependent conformational change (activation) of the charged voltage-sensor domains (VSDs), and its transduction to the pore. Previously, fast charge displacement was reported during VSD activation at negative potentials, but it is unclear how this is coupled to slow channel opening occurring at more depolarized potentials. Here, we optically tracked KV7.4 VSD activation with voltage-clamp fluorometry, leveraging two different fluorophores and pulsed excitation, to thoroughly characterize VSD movements. We found that VSD activation comprises several voltage-dependent transitions, some of which had kinetics and voltage-dependence matching those of channel opening and closing. The deafness-associated mutation R216H, which substitutes a charged amino-acid in the VSD, impaired both VSD movements and channel opening, shifting them towards more depolarized potentials. This suggested that R216H impaired KV7.4 function by destabilizing VSD activation. Using molecular dynamics, we found that H216 reduced intramolecular interactions, thus decreasing the stability of an active VSD conformation. We propose that the KV7.4 VSD activates in two steps: a fast movement at negative voltages that represents a first transition to an intermediate state of activation; and this is followed by slower, depolarized component that represents subsequent full VSD activation, which drives channel opening.

biophysics↗

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↗