Biology subjects

Williams-Noonan, B. J.

Publications and source records attributed to Williams-Noonan, B. J..

3 recordsLinked to original sources

bioRxiv2026

Structural basis for inefficient G protein coupling by Frizzled receptors

Frizzleds (FZDs) are class F G protein-coupled receptors (GPCRs) that primarily signal through Dishevelled (DVL) to initiate Wnt signalling, with evidence for context-specific coupling to heterotrimeric G proteins. Every FZD-G protein structure to date has been determined without an agonist, implying that agonist binding is not required for stable complex formation in vitro and directly contradicting the difficulty of demonstrating G protein coupling in cells. All these structures contain unassigned density between the receptor and the heterotrimeric G protein. From structures generated by single-particle cryo-electron microscopy (cryo-EM) of FZD7-Gs and FZD5-Gq, we identify this density as the detergent lauryl maltose neopentyl glycol (LMNG), which bridges the receptor and G protein to stabilise a weak, shallow interface. Absence of LMNG - in biochemical preparations and molecular dynamics simulations - destabilises the complex, showing that constitutive FZD-G protein engagement is intrinsically weak. The weak G protein coupling is governed by a conserved intracellular interface that when mutated differentially influences DVL and G protein signalling. Our findings show that LMNG has masked the instability of purified FZD-G protein complexes and provide the structural basis of FZDs as inherently weak G protein activators that are predisposed to DVL signalling.

biochemistry↗

bioRxiv2025

Structural insights into allosteric mechanism of glycine transporter-mediated analgesia

Chronic neuropathic pain, caused by nerve damage or disease, is increasing in prevalence, but current treatments are ineffective and over-reliant on opioids. The neuronal glycine transporter, GlyT2, regulates inhibitory glycinergic neurotransmission and represents a promising target for new analgesics. However, most GlyT2 inhibitors cause significant side effects, in part due to irreversible inhibition at analgesic doses. Here we develop a reversible inhibitor of GlyT2, RPI-GLYT2-82, and identify its binding site by determining cryo-EM structures of human GlyT2. We capture three fundamental conformational states of GlyT2 in the substrate-free state, and bound to either glycine, RPI-GLYT2-82 or the pseudo-irreversible inhibitor ORG25543. We demonstrate that RPI-GLYT2-82 dissociates from GlyT2 faster than ORG25543, providing analgesia in mouse neuropathic pain models without on-target side-effects or addiction liability. Our data provide a mechanistic understanding of allosteric inhibition of glycine transport, enabling structure-based design of non-opioid analgesics.

neuroscience↗

bioRxiv2023

Potassium dependent structural changes in the selectivity filter of HERG potassium channels

The fine tuning of biological electrical signaling is mediated by variations in the rates of opening and closing of gates that control ion flux through different ion channels. Human ether-a-go-go related gene (HERG) potassium channels have uniquely rapid inactivation kinetics which are critical to the role they play in regulating cardiac electrical activity. Here, we have exploited the K+ sensitivity of HERG inactivation to determine structures of both a conductive and non-conductive selectivity filter structure of HERG. We propose that inactivation is the result of a high propensity for flipping of the selectivity filter valine carbonyl oxygens. Molecular dynamics simulations point to a low energy barrier, and hence rapid kinetics, for flipping of the valine 625 carbonyl oxygens facilitated by a previously unrecognized interaction between S620 and Y616 that stabilizes the transition state between conducting and non-conducting structures. Our model represents a new mechanism by which ion channels fine tune their activity that explains the uniquely rapid inactivation kinetics of HERG. HighlightsStructures of a conductive and non-conductive HERG selectivity filter have been determined. Reduced potassium causes flipping of selectivity filter valine carbonyl oxygens. The sidechain of S620 on the pore helix coordinates distinct sets of interactions between conductive, non-conductive, and transition states.

biophysics↗