Biology subjects

McArthur, J. R.

Publications and source records attributed to McArthur, J. R..

6 recordsLinked to original sources

bioRxiv2024

Distinct molecular and functional properties of human induced-proprioceptor and low-threshold mechanoreceptor neurons

Sensing mechanical stimuli is crucial for the function of internal and external tissues, such as the skin and muscles. Much of our understanding of mechanosensory physiology relies on rodent studies, which may not directly translate to humans. To address the knowledge gap in human mechanosensation, we developed distinct populations of human mechanosensory neuronal subtypes from human pluripotent stem cells (hPSC). By inducing co-expression of NGN2/RUNX3 or NGN2/SHOX2 in hPSC-derived migrating neural crest cells we directed their specification to proprioceptor and low-threshold mechanoreceptor neuronal subtypes, respectively. The induced neurons exhibited transcriptional profiles consistent with mechanosensory neurons and displayed functional responses to mechanical stimuli, such as stretch and submicrometer probe indentation to the soma. Notably, each subtype displayed unique mechanical thresholds and desensitization properties akin to proprioceptors and low-threshold mechanoreceptors and both induced neuronal subtypes fired action potentials in response to minute mechanical stimuli, predominantly relying on PIEZO2 for mechanosensory function. Collectively, this study provides a foundational model for exploring human neuronal mechanosensory biology.

neuroscience↗

bioRxiv2022

Cellular Heterogeneity of Pluripotent Stem Cell Derived Cardiomyocyte Grafts is Mechanistically Linked to Treatable Arrhythmias

BackgroundExciting pre-clinical data have confirmed that human pluripotent stem cell derived cardiomyocytes (PSC-CMs) can remuscularise the injured or diseased heart, with several clinical trials now in planning or recruitment stages worldwide. However, ventricular arrhythmias are a predictable complication following engraftment of intramyocardially injected PSC-CMs. Therefore, there is an urgent unmet need to gain mechanistic insights and treatment strategies to control or prevent these engraftment arrhythmias (EAs). MethodsWe used a porcine model of myocardial infarction and PSC-CM transplantation to investigate efficacy of pharmacologic and catheter based anti-arrhythmic strategies in mitigating EAs. Furthermore, cell doses were robustly phenotyped using single cell ribonucleic acid sequencing and high parameter flow cytometry to identify cellular characteristics predictive of arrhythmogenesis. ResultsCombination therapy with amiodarone and ivabradine significantly reduced EA rate and burden following PSC-CM transplantation. Catheter ablation was also a feasible and effective treatment strategy which could be considered in the case of pharmacologically refractory arrhythmias. In addition, we show that EAs are mechanistically linked to cellular heterogeneity in the input PSC-CM and resultant graft. Specifically, we identify atrial and pacemaker-like cardiomyocytes as culprit arrhythmogenic subpopulations. We further describe two unique surface marker signatures, SIRPA+/CD90-/CD200+ and SIRPA+/CD90-/CD200-, which identify arrhythmogenic and non-arrhythmogenic cardiomyocytes respectively. ConclusionOur data deepens mechanistic understanding of EAs and suggests that modifications to current PSC-CM production and/or selection protocols could ameliorate this problem. We further show that current clinical pharmacologic and interventional anti-arrhythmic strategies can control and potentially abolish these arrhythmias, an important safety consideration given several impending clinical trials.

cell biology↗

bioRxiv2022

Identification of a sensory neuron Cav2.3 inhibitor within a new superfamily of macro-conotoxins

Animal venom peptides represent valuable compounds for biomedical exploration. The venoms of marine cone snails constitute a particularly rich source of peptide toxins, known as conotoxins. Here, we identify the sequence of an unusually large conotoxin, Mu8.1, that defines a new class of conotoxins evolutionarily related to the well-known con-ikot-ikots and two additional conotoxin classes not previously described. The crystal structure of recombinant Mu8.1 displays a saposin-like fold and shows structural similarity with con-ikot-ikot. Functional studies demonstrate that Mu8.1 curtails calcium influx in defined classes of murine somatosensory dorsal root ganglion (DRG) neurons. When tested on a variety of voltage-gated ion channels, Mu8.1 preferentially inhibited the R-type (Cav2.3) calcium channel. Ca2+ signals from Mu8.1-sensitive DRG neurons were also inhibited by SNX-482, a known spider peptide modulator of Cav2.3 and voltage-gated K+ (Kv4) channels. Our findings highlight the potential of Mu8.1 as a molecular tool to identify and study neuronal subclasses expressing Cav2.3. Importantly, this multidisciplinary study demonstrates the feasibility of large, disulfide-rich venom-component investigation, an endeavor that will lead to the discovery of novel structures and functions in the previously underexplored group of macro-conotoxins.

biochemistry↗

bioRxiv2022

Automated patch clamp screening of amiloride and 5-N,N-hexamethyleneamiloride (HMA) analogs identifies 6-iodoamiloride as a potent acid-sensing ion channel inhibitor.

Acid-sensing ion channels (ASICs) are transmembrane sensors of extracellular acidosis and potential drug targets in several disease indications, including neuropathic pain and cancer metastasis. The K+-sparing diuretic amiloride is a moderate non-specific inhibitor of ASICs and has been widely used as a probe for elucidating ASIC function. In this work, we screened a library of 6-substituted and 5,6-disubstituted amiloride analogs using a custom-developed automated patch-clamp protocol and identified 6-iodoamiloride as a more potent ASIC1 inhibitor. Follow-up IC50 determinations in tsA-201 cells confirmed higher ASIC1 inhibitory potency for 6-iodoamiloride 97 (hASIC1 97 IC50 88 nM cf. amiloride 11 IC50 1.7 M). A similar improvement in activity was observed in ASIC3-mediated currents from rat small diameter dorsal root ganglion neurons (rDRG single-concentration 97 IC50 230 nM cf. 11 IC50 2.7 M). 6-iodoamiloride represents the amiloride analogue of choice for studying the effects of ASIC inhibition on cell physiology.

pharmacology and toxicology↗

bioRxiv2021

{micro}-Theraphotoxin-Pn3a inhibition of Cav3.3 channels reveals a novel isoform-selective drug binding site

Low voltage-activated calcium currents are mediated by T-type calcium channels CaV3.1, CaV3.2, and CaV3.3, which modulate a variety of physiological processes including sleep, cardiac pace-making, pain, and epilepsy. CaV3 isoforms biophysical properties, overlapping expression and lack of subtype-selective pharmacology hinder the determination of their specific physiological roles in health and disease. Notably, CaV3.3s contribution to normal and pathophysiological function has remained largely unexplored. We have identified Pn3a as the first subtype-selective spider venom peptide inhibitor of CaV3.3, with >100-fold lower potency against the other T-type isoforms. Pn3a modifies CaV3.3 gating through a depolarizing shift in the voltage dependence of activation thus decreasing CaV3.3-mediated currents in the normal range of activation potentials. Paddle chimeras of KV1.7 channels bearing voltage sensor sequences from all four CaV3.3 domains revealed preferential binding of Pn3a to the S3-S4 region of domain II (CaV3.3DII). This novel T-type channel pharmacological site was explored through computational docking simulations of Pn3a into all T-type channel isoforms highlighting it as subtype-specific pharmacophore with therapeutic potential. This research expands our understanding of T-type calcium channel pharmacology and supports the suitability of Pn3a as a molecular tool in the study of the physiological roles of CaV3.3 channels.

pharmacology and toxicology↗

bioRxiv2020

Analgesic α-conotoxins modulate GIRK1/2 channels via GABAB receptor activation and reduce neuroexcitability

Activation of G protein-coupled inwardly rectifying potassium (GIRK or Kir3) channels leads to membrane hyperpolarization and dampening of neuronal excitability. Here we show that the analgesic -conotoxin Vc1.1 potentiates inwardly rectifying K+ currents (IKir) mediated through native and recombinant GIRK1/2 channels by activation of the G protein-coupled GABAB receptor (GABABR) via a Pertussis toxin (PTX)-sensitive G protein. Recombinant co-expression of human GIRK1/2 subunits and GABABR in HEK293T cells resulted in a Ba2+-sensitive IKir potentiated by baclofen and Vc1.1 which was inhibited by PTX, intracellular GDP-{beta}-S, or the GABABR-selective antagonist CGP 55845. In adult mouse DRG neurons, GABABR-dependent GIRK channel potentiation by Vc1.1 and baclofen hyperpolarizes the cell resting membrane potential with concomitant reduction of excitability consistent with Vc1.1 and baclofen analgesic effects in vivo. This study provides new insight into Vc1.1 as an allosteric agonist for GABABR-mediated potentiation of GIRK channels and may aid in the development of novel non-opioid treatments for chronic pain.

neuroscience↗