Biology subjects

Cote, J. M.

Publications and source records attributed to Cote, J. M..

3 recordsLinked to original sources

bioRxiv2026

Muscarinic Suppression of BK Channels in Type II Vestibular Hair Cells of Mouse Cristae

Cholinergic efferent neurons modulate sensory signaling in the peripheral vestibular system, but the cellular mechanisms underlying this modulation remain incompletely understood. In mammalian vestibular organs, type II hair cells (HC-II) receive efferent input and express 910-containing nicotinic acetylcholine receptors (nAChRs) that activate SK potassium channels and produce rapid hyperpolarization. Here, we examined the functional role of mAChRs in mouse vestibular HC-II using whole cell patch clamp recordings in whole tissue preparations of crista ampularis (P13-P17, male and female mice). Activation of mAChRs with oxotremorine-M inhibited voltage dependent outward currents, with the largest effects at depolarized membrane potentials. Further experiments revealed that this effect was mediated by inhibition of large conductance potassium (BK) channels: the BK antagonist iberiotoxin mimicked and occluded the muscarinic effect and muscarinic suppression was absent in mice with BK channel mutations. In contrast, blockade of SK channels with apamin did not prevent the muscarinic effect, indicating that mAChR signaling specifically targets BK mediated currents. In current clamp recordings, mAChR activation enhanced depolarization during strong current injections, consistent with increased hair cell excitability when BK channels were suppressed. These findings identify a previously unrecognized muscarinic efferent pathway in vestibular hair cells and reveal complementary cholinergic mechanisms that suppress responses to weak stimuli while enhancing responses to strong stimulation, providing a cellular basis for dynamic gain control in the vestibular periphery. Significance statementVestibular efferent signaling shapes how head movements are encoded, but its cellular mechanisms are incompletely understood. While nicotinic acetylcholine receptors are known to reduce excitability of type II vestibular hair cells (HC-II) via small conductance (SK) channels, the role of muscarinic receptors has remained unclear. Here we show that muscarinic receptor activation selectively inhibits large conductance (BK) potassium channels in HC-II, enhancing excitability during strong depolarization. This muscarinic pathway is mechanistically distinct from nicotinic signaling and operates at a different voltage range. Together, these findings reveal a dual efferent control strategy that differentially regulates hair cell responses to slow versus fast head movements, providing new insight into how the vestibular system filters sensory input across dynamic ranges.

physiology↗

bioRxiv2021

Discovery of Aminoglycosides as first in class, nanomolar inhibitors of Heptosyltransferase I

A clinically relevant inhibitor for Heptosyltransferase I (HepI) has been sought after for many years and while many have designed novel small-molecule inhibitors, these compounds lack the bioavailability and potency necessary for therapeutic use. Extensive characterization of the HepI protein has provided valuable insight into the dynamic motions necessary for catalysis that could be targeted for inhibition. With the help of molecular dynamic simulations, aminoglycoside antibiotics were shown to be putative inhibitors for HepI and in this study, they were experimentally determined to be the first in-class nanomolar inhibitors of HepI with the best inhibitor demonstrating a Ki of 600 +/- 90 nM. Detailed kinetic analyses were performed to determine the mechanism of inhibition while circular dichroism spectroscopy, intrinsic tryptophan fluorescence, docking, and MD simulations were used to corroborate kinetic experimental findings. Kinetic analysis methods include Lineweaver-Burk, Dixon, Cornish-Bowden and Mixed-Model of Inhibition which allowed for unambiguous assignment of inhibition mechanism for each inhibitor. In this study, we show that neomycin and kanamycin b are competitive inhibitors against the sugar acceptor substrate while tobramycin exhibits a mixed inhibitory effect and streptomycin is non-competitive. MD simulations also allowed us to suggest that the inhibitors bind tightly and inhibit catalytic dynamics due to a major desolvation penalty of the enzyme active site. While aminoglycosides have long been known as a class of potent antibiotics, they also have been scientifically shown to impact cell membrane stability, and we propose that inhibition of HepI contributes to this effect by disrupting lipopolysaccharide biosynthesis.

biochemistry↗

bioRxiv2018

Two factor authorization: Asf1 mediates crosstalk between H3 K14 and K56 acetylation

Acetylation of histones plays a critical role in maintaining the epigenetic state of the eukaryotic cell. One such acetylation site critical for DNA damage repair is H3K56ac. In Saccharomyces cerevisiae, H3K56ac is thought to be driven mainly by Rtt109, a lysine acetyltransferase (KAT) that associates with the histone chaperones Vps75 and Asf1. Both of these chaperones can increase the specificity of histone acetylation by Rtt109, but neither alter the selectivity. It has been shown that histones extracted from cells (Drosophila), presumably containing pre-acetylated histones, can incorporate higher amounts of H3K56ac relative to recombinant non-acetylated histones. We hypothesized that histone pre-acetylation and histone chaperones could function together to drive acetylation of H3K56. In the present study, we test this hypothesis using a series of singly acetylated histones to determine the impact of crosstalk on enzyme selectivity. Our data suggest that crosstalk between acetylation sites plays a major role in altering the selectivity of Rtt109-Vps75 and that the histone chaperone Asf1 mediates this crosstalk. Specifically, we show that H3K14ac/H4 functions with Asf1 to drive H3K56ac by Rtt109-Vps75. We identified an acidic patch in Asf1 that mediates this cross-talk and show that mutations to this region can alter the Asf1 mediated crosstalk that changes Rtt109-Vps75 selectivity. These data explain the genetic link between Gcn5, which acetylates H3K14 and Rtt109. More broadly these data demonstrate that acetylation sites can dictate site selectivity even in the absence of a bromodomain and helps to explain the limited complexity that has been observed of the histone post-translational modifications patterns by global proteomic studies.

biochemistry↗