Distinct specificity and functions of PRC2 subcomplexes in human stem cells and cardiac differentiation.

The dynamic regulation of epigenetic states relies on complex macromolecular interactions. PRC2, the methyltransferase complex depositing H3K27me3, interacts with distinct accessory proteins to form the mutually exclusive subcomplexes PHF1-PRC2.1, MTF2-PRC2.

The NaV1.5 auxiliary subunit FGF13 modulates channels by regulating membrane cholesterol independent of channel binding.

Fibroblast growth factor homologous factors (FHFs) bind to the cytoplasmic carboxy terminus of voltage-gated sodium channels (VGSCs) and modulate channel function. Variants in FHFs or VGSCs perturbing that bimolecular interaction are associated with arrhythmias. Like some channel auxiliary subunits, FHFs exert additional cellular regulatory roles, but whether these alternative roles affect VGSC regulation is unknown.

FGF13 regulates cardiomyocyte impulse propagation via Cx43 trafficking independent of voltage-gated sodium channels.

Background: Fibroblast growth factor homologous factor (FHF) variants associate with arrhythmias. Although FHFs are best characterized as regulators of voltage gated sodium channel (VGSC) gating, recent studies suggest broader, non-VGSC-related functions, including regulation of Cx43 gap junctions and/or hemichannels, mechanisms that have generally been understudied or disregarded.

Methods: We assessed cardiac conduction and cardiomyocyte action potentials in mice with constitutive cardiac-specific ablation (c ) while targeting Cx43 gap junctions and hemichannels pharmacologically.

Macromolecular interactions dictate Polycomb-mediated epigenetic repression.

The dynamic regulation of epigenetic states relies on complex macromolecular interactions. PRC2, the methyltransferase complex responsible for depositing H3K27me3, interacts with distinct accessory proteins to form the mutually exclusive subcomplexes PHF1-PRC2.1, MTF2-PRC2.

The Na 1.5 auxiliary subunit FGF13 modulates channels by regulating membrane cholesterol independent of channel binding.

Fibroblast growth factor homologous factors (FHFs) bind to the cytoplasmic carboxy terminus of voltage-gated sodium channels (VGSCs) and modulate channel function. Variants in FHFs or VGSCs perturbing that bimolecular interaction are associated with arrhythmias. Like some channel auxiliary subunits, FHFs exert additional cellular regulatory roles, but whether these alternative roles affect VGSC regulation is unknown.

Interneuron FGF13 regulates seizure susceptibility via a sodium channel-independent mechanism.

Developmental and epileptic encephalopathies (DEEs), a class of devastating neurological disorders characterized by recurrent seizures and exacerbated by disruptions to excitatory/inhibitory balance in the brain, are commonly caused by mutations in ion channels. Disruption of, or variants in, were implicated as causal for a set of DEEs, but the underlying mechanisms were clouded because is expressed in both excitatory and inhibitory neurons, undergoes extensive alternative splicing producing multiple isoforms with distinct functions, and the overall roles of FGF13 in neurons are incompletely cataloged. To overcome these challenges, we generated a set of novel cell-type-specific conditional knockout mice.

Interneuron FGF13 regulates seizure susceptibility via a sodium channel-independent mechanism.

Developmental and Epileptic Encephalopathies (DEEs), a class of devastating neurological disorders characterized by recurrent seizures and exacerbated by disruptions to excitatory/inhibitory balance in the brain, are commonly caused by mutations in ion channels. Disruption of, or variants in, were implicated as causal for a set of DEEs, but the underlying mechanisms were clouded because is expressed in both excitatory and inhibitory neurons, undergoes extensive alternative splicing producing multiple isoforms with distinct functions, and the overall roles of FGF13 in neurons are incompletely cataloged. To overcome these challenges, we generated a set of novel cell type-specific conditional knockout mice.

SARS-CoV-2 Infection Induces Ferroptosis of Sinoatrial Node Pacemaker Cells.

Background: Increasing evidence suggests that cardiac arrhythmias are frequent clinical features of coronavirus disease 2019 (COVID-19). Sinus node damage may lead to bradycardia. However, it is challenging to explore human sinoatrial node (SAN) pathophysiology due to difficulty in isolating and culturing human SAN cells.

Chronic Morphine Induces IL-18 in Ileum Myenteric Plexus Neurons Through Mu-opioid Receptor Activation in Cholinergic and VIPergic Neurons.

The gastrointestinal epithelium is critical for maintaining a symbiotic relationship with commensal microbiota. Chronic morphine exposure can compromise the gut epithelial barrier in mice and lead to dysbiosis. Recently, studies have implicated morphine-induced dysbiosis in the mechanism of antinociceptive tolerance and reward, suggesting the presence of a gut-brain axis in the pharmacological effects of morphine.

An interaction between the III-IV linker and CTD in NaV1.5 confers regulation of inactivation by CaM and FHF.

Voltage gated sodium channel (VGSC) activation drives the action potential upstroke in cardiac myocytes, skeletal muscles, and neurons. After opening, VGSCs rapidly enter a non-conducting, inactivated state. Impaired inactivation causes persistent inward current and underlies cardiac arrhythmias.

Knockout of the X-linked in the hypothalamic paraventricular nucleus impairs sympathetic output to brown fat and causes obesity.

Fibroblast growth factor (FGF)13, a nonsecreted, X-linked, FGF homologous factor, is differentially expressed in adipocytes in response to diet, yet 's role in metabolism has not been explored. Heterozygous knockouts fed normal chow and housed at 22°C showed hyperactivity accompanying reduced core temperature and obesity when housed at 30°C. Those heterozygous knockouts showed defects in thermogenesis even at 30°C and an inability to protect core temperature.

Connexin-purinergic signaling in enteric glia mediates the prolonged effect of morphine on constipation.

Morphine is one of the most widely used drugs for the treatment of pain. However, side effects, including persistent constipation and antinociceptive tolerance, limit its clinical efficacy. Prolonged morphine treatment results in a "leaky" gut, predisposing to colonic inflammation that is facilitated by microbial dysbiosis and associated bacterial translocation.

Enhanced Sensitivity of α3β4 Nicotinic Receptors in Enteric Neurons after Long-Term Morphine: Implication for Opioid-Induced Constipation.

Opioid-induced constipation is a major side effect that persists with long-term opioid use. Previous studies demonstrated that nicotine-induced contractions are enhanced after long-term morphine exposure in guinea pig ileum. In the present study, we examined whether the increased sensitivity to nicotine could be observed in single enteric neurons after long-term morphine exposure, determined the subunits in mouse enteric neurons, and examined the effect of nicotine in reversing opioid-induced constipation.

Interaction between hydrogen sulfide-induced sulfhydration and tyrosine nitration in the KATP channel complex.

Hydrogen sulfide (H₂S) is an endogenous gaseous mediator affecting many physiological and pathophysiological conditions. Enhanced expression of H2S and reactive nitrogen/oxygen species (RNS/ROS) during inflammation alters cellular excitability via modulation of ion channel function. Sulfhydration of cysteine residues and tyrosine nitration are the posttranslational modifications induced by H₂S and RNS, respectively.

Hydrogen sulfide as an allosteric modulator of ATP-sensitive potassium channels in colonic inflammation.

The ATP-sensitive potassium channel (K(ATP)) in mouse colonic smooth muscle cell is a complex containing a pore-forming subunit (Kir6.1) and a sulfonylurea receptor subunit (SUR2B). These channels contribute to the cellular excitability of smooth muscle cells and hence regulate the motility patterns in the colon.

Opioid-induced hypernociception is associated with hyperexcitability and altered tetrodotoxin-resistant Na+ channel function of dorsal root ganglia.

Opiates are potent analgesics for moderate to severe pain. Paradoxically, patients under chronic opiates have reported hypernociception, the mechanisms of which are unknown. Using standard patch-clamp technique, we examined the excitability, biophysical properties of tetrodotoxin-resistant (TTX-R) Na(+) and transient receptor potential vanilloid 1 (TRPV1) channels of dorsal root ganglia neurons (DRG) (L(5)-S(1)) from mice pelleted with morphine (75 mg) or placebo (7 days).