Biology subjects

Smith, C. E.

Publications and source records attributed to Smith, C. E..

3 recordsLinked to original sources

bioRxiv2025

Nucleosome context regulates chromatin reader preference

Chromatin is more than a simple genome packaging system, and instead locally distinguished by histone post-translational modifications (PTMs) that can directly change nucleosome structure and / or be "read" by chromatin-associated proteins to mediate downstream events. An accurate understanding of histone PTM binding preference is vital to explain normal function and pathogenesis, and has revealed multiple therapeutic opportunities. Such studies most often use histone peptides, even though these cannot represent the full regulatory potential of nucleosome context. Here we apply a range of complementary and easily adoptable biochemical and genomic approaches to interrogate fully defined peptide and nucleosome targets with a diversity of mono or multivalent chromatin readers. In the resulting data, nucleosome context consistently refined reader binding, and multivalent engagement was more often regulatory than simply additive. This included abrogating the binding of the Polycomb group L3MBTL1 MBT to histone tails with lower methyl states (me1 or me2 at H3K4, H3K9, H3K27, H3K36 or H4K20); and confirmation that the CBX7 chromodomain and AT-hook-like motif (CD-ATL) tandem act as a functional unit to confer specificity for H3K27me3. Further, in vitro nucleosome preferences were confirmed by in vivo reader-CUT&RUN genomic mapping. Such data confirms that more representative chromatin substrates provide greater insight to biological mechanism and its disorder in human disease.

biochemistry↗

bioRxiv2024

Acute sildenafil administration reduces susceptibility to induced atrial fibrillation in sheep

BackgroundSildenafil is a PDE5 inhibitor with a very good safety profile and animal models suggest it may be beneficial in the treatment of heart failure and ventricular fibrillation. Sildenafil has also been associated with a reduced incidence of atrial fibrillation (AF) in a retrospective observational study. We have therefore sought to determine whether sildenafil has a direct effect on atrial electrophysiology and resultant AF burden. MethodsInvasive electrophysiological studies were performed in 12 anaesthetised healthy adult female Welsh mountain sheep. Pacing protocols were performed in the right atrium before and after administration of an acute 10 mg intravenous bolus of sildenafil and the burden of AF assessed. ResultsSildenafil profoundly reduced the vulnerability to AF, decreasing AF duration (112.2 {+/-} 73.5 s vs. 3.3 {+/-} 1.4 s), the number of burst pacing inductions causing AF (90 % vs 70 %) and the complexity of AF. The antiarrhythmic effects of sildenafil were determined to be resultant of prolongation of both the atrial effective refractory period (146.9 {+/-} 7.2 ms vs 166.2 {+/-} 32.5 ms) and the atrial excitation wavelength (12.9 {+/-} 0.07 cm vs 15.0 {+/-} 0.07 cm) and resulted in a shallower restitution curve, reflected in a decreased magnitude of monophasic action potential alternans (0.09 {+/-} 0.001 mV vs 0.05 {+/-} 0.10 mV). ConclusionsIn the subjectively healthy atria of a highly translational model a strong antiarrhythmic effect upon acute sildenafil application was observed suggestive of a potential clinical benefit in AF.

physiology↗

bioRxiv2024

LYMTACs: Chimeric Small Molecules Repurpose Lysosomal Membrane Proteins for Target Protein Relocalization and Degradation

Proximity-inducing modalities that co-opt cellular pathways offer new opportunities to regulate oncogenic drivers. Inspired by the success of proximity-based chimeras in both intracellular and extracellular target space, here we describe the development of LYsosome Membrane TArgeting Chimeras (LYMTACs) as a novel small molecule-based platform that functions intracellularly to modulate the membrane proteome. Conceptually, LYMTACs are heterobifunctional small molecules that co-opt short-lived lysosomal membrane proteins (LMPs) as effectors to deliver targets for lysosomal degradation. We demonstrate that a promiscuous kinase inhibitor-based LYMTAC selectively targets membrane proteins for lysosomal degradation via RNF152, a short-lived LMP. To extend these findings, we show that oncogenic, membrane-associated KRASG12D protein can be tethered to RNF152, inducing KRAS relocalization to the lysosomal membrane, inhibiting downstream phospho-ERK signaling, and leading to lysosomal degradation of KRASG12D in a LYMTAC-dependent manner. Notably, potent cell killing could be attributed to the multi-pharmacology displayed by LYMTACs, which differentiates the LYMTAC technology from existing modalities. Thus, LYMTACs represent a proximity-based therapeutic approach that promises to expand the target space for challenging membrane proteins through targeted protein relocalization and degradation.

cancer biology↗