Distinctive biochemical properties of the μ-opioid receptor-corticotropin- releasing factor CRF receptor heterotetramer.

Heteromerization of Gs with Gi protein-coupled receptors has been suggested to be necessary to sustain the canonical Gi-Gs antagonistic interaction at adenylyl cyclase (AC). These heteromers have a tetrameric quaternary structure, composed by two homodimers each one coupled to its corresponding G protein. We describe the heterotetramer formed by the Gi-coupled μ-opioid receptor (MOR) and the Gs-coupled corticotropin releasing factor CRF receptor (CRFR), which also sustains a canonical interaction at AC and reciprocal allosteric interactions between MOR and CRFR ligands.

Orthosteric interactions with PIP activate TMEM16A channels.

TMEM16A channels pass Ca -activated Cl currents that drive a plethora of fundamental physiological processes. TMEM16A channels are activated by a rise in intracellular Ca levels but also require interactions with the signaling phospholipid phosphatidylinositol 4,5-bisphosphate (PIP ) to gate open. Although PIP is essential for the activity of many types of ion channels, its precise binding site and role in channel gating remain poorly understood in most cases, limiting efforts to study channel dynamics and design targeted modulators.

SUMO Regulation of Ion Channels in Health and Disease.

The small ubiquitin-like modifier (SUMO) protein pathway governs a panoply of vital biological processes including cell death, proliferation, differentiation, metabolism, and signal transduction by diversifying the functions, half-lives, and partnerships of target proteins in situ. More recently, SUMOylation has emerged as a key regulator of ion homeostasis and excitability across multiple tissues due to the regulation of a plethora of ion channels expressed in a range of tissue subtypes. Altogether, the balance of SUMOylation states among relevant ion channels can result in graded biophysical effects that tune excitability and contribute to a range of disease states including cardiac arrhythmia, epilepsy, pain transmission, and inflammation.

Crosstalk between PKA and PIAS3 regulates cardiac Kv4 channel SUMOylation.

Post-translational SUMOylation of nuclear and cytosolic proteins maintains homeostasis in eukaryotic cells and orchestrates programmed responses to changes in metabolic demand or extracellular stimuli. In excitable cells, SUMOylation tunes the biophysical properties and trafficking of ion channels. Ion channel SUMOylation status is determined by the opposing enzyme activities of SUMO ligases and deconjugases.

Evaluating protein cross-linking as a therapeutic strategy to stabilize SOD1 variants in a mouse model of familial ALS.

Mutations in the gene encoding Cu-Zn superoxide dismutase 1 (SOD1) cause a subset of familial amyotrophic lateral sclerosis (fALS) cases. A shared effect of these mutations is that SOD1, which is normally a stable dimer, dissociates into toxic monomers that seed toxic aggregates. Considerable research effort has been devoted to developing compounds that stabilize the dimer of fALS SOD1 variants, but unfortunately, this has not yet resulted in a treatment.

The Concise Guide to PHARMACOLOGY 2023/24: Ion channels.

The Concise Guide to PHARMACOLOGY 2023/24 is the sixth in this series of biennial publications. The Concise Guide provides concise overviews, mostly in tabular format, of the key properties of approximately 1800 drug targets, and over 6000 interactions with about 3900 ligands. There is an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (https://www.

PI(4,5)P2 regulates the gating of NaV1.4 channels.

Voltage-gated sodium (NaV) channels are densely expressed in most excitable cells and activate in response to depolarization, causing a rapid influx of Na+ ions that initiates the action potential. The voltage-dependent activation of NaV channels is followed almost instantaneously by fast inactivation, setting the refractory period of excitable tissues. The gating cycle of NaV channels is subject to tight regulation, with perturbations leading to a range of pathophysiological states.

Imaging Membrane Proteins Using Total Internal Reflection Fluorescence Microscopy (TIRFM) in Mammalian Cells.

The cell surfaceome is of vital importance across physiology, developmental biology, and disease states alike. The precise identification of proteins and their regulatory mechanisms at the cell membrane has been challenging and is typically determined using confocal microscopy, two-photon microscopy, or total internal reflection fluorescence microscopy (TIRFM). Of these, TIRFM is the most precise, as it harnesses the generation of a spatially delimited evanescent wave at the interface of two surfaces with distinct refractive indices.

SUMOylation of Na1.2 channels regulates the velocity of backpropagating action potentials in cortical pyramidal neurons.

Voltage-gated sodium channels located in axon initial segments (AIS) trigger action potentials (AP) and play pivotal roles in the excitability of cortical pyramidal neurons. The differential electrophysiological properties and distributions of Na1.2 and Na1.

Optogenetic dephosphorylation of phosphatidylinositol 4,5 bisphosphate in Xenopus laevis oocytes.

Here, we present a protocol for optogenetic dephosphorylation of the phosphoinositide PI(4,5)P at the plasma membrane of Xenopus laevis oocytes. We first describe the co-injection of oocytes with cRNAs encoding (1) a light-activated PI(4,5)P 5-phosphatase fusion protein, (2) its dimerization partner fused to the plasma membrane, and (3) the potassium channel reporter for PI(4,5)P dephosphorylation. We then detail blue light illumination to induce PI(4,5)P dephosphorylation, combined with simultaneous two-electrode voltage clamp electrophysiological recording to assess potassium channel current responses.

Mechanism of PKCε regulation of cardiac GIRK channel gating.

G-protein-gated inwardly rectifying potassium (GIRK) channel activity is regulated by the membrane phospholipid, phosphatidylinositol-4,5-bisphosphate (PI 4,5P). Constitutive activity of cardiac GIRK channels in atrial myocytes, that is implicated in atrial fibrillation (AF), is mediated via a protein kinase C-ε (PKCε)-dependent mechanism. The novel PKC isoform, PKCε, is reported to enhance the activity of cardiac GIRK channels.

Hypoxia inhibits the cardiac current through SUMO targeting Kir2.1 activation by PIP.

Cardiovascular diseases remain the leading cause of death worldwide. Most deaths are sudden and occur secondary to the occlusion of coronary arteries resulting in a rapid decrease in cellular oxygen levels. Acute hypoxia is proarrhythmic, leading to disordered electrical signals, conduction block, and uncoordinated beating of the myocardium.

A novel small-molecule selective activator of homomeric GIRK4 channels.

G protein-sensitive inwardly rectifying potassium (GIRK) channels are important pharmaceutical targets for neuronal, cardiac, and endocrine diseases. Although a number of GIRK channel modulators have been discovered in recent years, most lack selectivity. GIRK channels function as either homomeric (i.

An optogenetic tool to recruit individual PKC isozymes to the cell surface and promote specific phosphorylation of membrane proteins.

The PKC family consists of several closely related kinases. These enzymes regulate the function of proteins through the phosphorylation of hydroxyl groups on serines and/or threonines. The selective activation of individual PKC isozymes has proven challenging because of a lack of specific activator molecules.

A molecular switch controls the impact of cholesterol on a Kir channel.

SignificanceCholesterol is one of the main components found in plasma membranes and is involved in lipid-dependent signaling enabled by integral membrane proteins such as inwardly rectifying potassium (Kir) channels. Similar to other ion channels, most of the Kir channels are down-regulated by cholesterol. One of the very few notable exceptions is Kir3.

THE CONCISE GUIDE TO PHARMACOLOGY 2021/22: Ion channels.

The Concise Guide to PHARMACOLOGY 2021/22 is the fifth in this series of biennial publications. The Concise Guide provides concise overviews, mostly in tabular format, of the key properties of nearly 1900 human drug targets with an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (www.guidetopharmacology.

Multifaceted Regulation of Potassium-Ion Channels by Graphene Quantum Dots.

Graphene quantum dots (GQDs) are emerging as a versatile nanomaterial with numerous proposed biomedical applications. Despite the explosion in potential applications, the molecular interactions between GQDs and complex biomolecular systems, including potassium-ion (K) channels, remain largely unknown. Here, we use molecular dynamics (MD) simulations and electrophysiology to study the interactions between GQDs and three representative K channels, which participate in a variety of physiological processes and are closely related to many disease states.

The Pharmacology of Two-Pore Domain Potassium Channels.

Two-pore domain potassium channels are formed by subunits that each contain two pore-loops moieties. Whether the channels are expressed in yeast or the human central nervous system, two subunits come together to form a single potassium selective pore. TOK1, the first two-domain channel was cloned from Saccharomyces cerevisiae in 1995 and soon thereafter, 15 distinct K subunits were identified in the human genome.

A benzopyran with antiarrhythmic activity is an inhibitor of Kir3.1-containing potassium channels.

Atrial fibrillation (AF) is the most commonly diagnosed cardiac arrhythmia and is associated with increased morbidity and mortality. Currently approved AF antiarrhythmic drugs have limited efficacy and/or carry the risk of ventricular proarrhythmia. The cardiac acetylcholine activated inwardly rectifying K current (I), composed of Kir3.

Hypoxia Produces Pro-arrhythmic Late Sodium Current in Cardiac Myocytes by SUMOylation of Na1.5 Channels.

Acute cardiac hypoxia produces life-threatening elevations in late sodium current (I) in the human heart. Here, we show the underlying mechanism: hypoxia induces rapid SUMOylation of Na1.5 channels so they reopen when normally inactive, late in the action potential.

The small molecule GAT1508 activates brain-specific GIRK1/2 channel heteromers and facilitates conditioned fear extinction in rodents.

G-protein-gated inwardly-rectifying K (GIRK) channels are targets of G-protein-signaling systems that inhibit cell excitability. GIRK channels exist as homotetramers (GIRK2 and GIRK4) or heterotetramers with nonfunctional homomeric subunits (GIRK1 and GIRK3). Although they have been implicated in multiple conditions, the lack of selective GIRK drugs that discriminate among the different GIRK channel subtypes has hampered investigations into their precise physiological relevance and therapeutic potential.

Potential blockade of the human voltage-dependent anion channel by MoS nanoflakes.

Despite significant interest in molybdenum disulfide (MoS2) nanomaterials, particularly in biomedicine, their biological effects have been understudied. Here, we explored the effect of MoS2 nanoflakes on the ubiquitous mitochondrial porin voltage-dependent anion channel (VDAC1), using a combined computational and functional approach. All-atomic molecular dynamics simulations suggest that MoS2 nanoflakes make specific contact interactions with human VDAC1.