Kloecker, N. | bioRxiv Science

bioRxiv2026

PI(4,5)P2-dependence of GABAA receptor channel function revealed by optogenetic manipulation of a binding site

ABSTRACT/SUMMARYIonotropic GABAA receptors (GABAARs) mediate fast inhibitory neurotransmission in mammalian brains. While recent structural studies have identified that phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2], a well-established regulator of numerous ion channels, binds to the 1 subunits of GABAARs, the functional relevance of this binding has remained elusive. Here, we combine electrophysiology, molecular dynamics simulations, and a recently developed caged lysine technology to define the role of PI(4,5)P2 in GABAARs. We show that GABAARs are insensitive to acute PI(4,5)P2 depletions by voltage-sensing phosphatase, but sensitivity is conferred by neutralizing the K311 binding site, indicating high-affinity binding. Caging of K311 by use of genetic code expansion recapitulated phenotypes of K311 mutant, conferring sensitivity to PI(4,5)P2 depletion, whereas uncaging restored insensitivity. Furthermore, caging K311 revealed decelerated activation, which then can be accelerated by uncaging. Additionally, PI(4,5)P2-dependence extends to glycine receptors, suggesting PI(4,5)P2 is an important endogenous phospholipid modulator of inhibitory receptor channels.

biophysics↗

bioRxiv2024

Optical Control of Cardiac Electrophysiology by thePhotochromic Ligand AB2

Ventricular arrhythmias (VAs) may occur in both the structurally normal and diseased heart. Particularly, patients suffering from ischemic heart disease and heart failure are at high risk of recurrent VA eventually leading to sudden cardiac death (SCD). While high-voltage shocks delivered by an implantable defibrillator may prevent SCD, these interventions themselves impair quality of life and raise both morbidity and mortality, which accentuates the need for developing novel defibrillation techniques. Here, we report the photochromic ligand azobupivacaine 2 (AB2) to enable gradual control of cardiac electrophysiology by light. By reversibly blocking voltage-gated both Na+ and K+ channels, photoswitching of AB2 modulates both the ventricular effective refractory period and conduction velocity thereby converting VA into sinus rhythm in an ex-vivo intact heart model. Thus, AB2 opens the door to the development of an optical defibrillator based on photopharmacology.

pharmacology and toxicology↗