Key phosphorylation sites for robust β-arrestin2 binding at the MOR revisited.

Desensitisation of the mu-opioid receptor (MOR) is proposed to underlie the initiation of opioid analgesic tolerance and previous work has shown that agonist-induced phosphorylation of the MOR C-tail contributes to this desensitisation. Moreover, phosphorylation is important for β-arrestin recruitment to the receptor, and ligands of different efficacies induce distinct phosphorylation barcodes. The C-tail TREHPSTANT motif harbours Ser/Thr residues important for these regulatory functions.

Cardiac human bitter taste receptors contain naturally occurring variants that alter function.

Bitter taste receptors (T2R) are a subfamily of G protein-coupled receptors that enable humans to detect aversive and toxic substances. The ability to discern bitter compounds varies between individuals and is attributed mainly to naturally occurring T2R polymorphisms. T2Rs are also expressed in numerous non-gustatory tissues, including the heart, indicating potential contributions to cardiovascular physiology.

TSH Pulses Finely Tune Thyroid Hormone Release and TSH Receptor Transduction.

Detection of circulating TSH is a first-line test of thyroid dysfunction, a major health problem (affecting about 5% of the population) that, if untreated, can lead to a significant deterioration of quality of life and adverse effects on multiple organ systems. Human TSH levels display both pulsatile and (nonpulsatile) basal TSH secretion patterns; however, the importance of these in regulating thyroid function and their decoding by the thyroid is unknown. Here, we developed a novel ultra-sensitive ELISA that allows precise detection of TSH secretion patterns with minute resolution in mouse models of health and disease.

Assessment of the potential of novel and classical opioids to induce respiratory depression in mice.

Background And Purpose: Opioid-induced respiratory depression limits the use of μ-opioid receptor agonists in clinical settings and is the main cause of opioid overdose fatalities. The relative potential of different opioid agonists to induce respiratory depression at doses exceeding those producing analgesia is understudied despite its relevance to assessments of opioid safety. Here we evaluated the respiratory depressant and anti-nociceptive effects of three novel opioids and relate these measurements to their in vitro efficacy.

Plasma membrane preassociation drives β-arrestin coupling to receptors and activation.

β-arrestin plays a key role in G protein-coupled receptor (GPCR) signaling and desensitization. Despite recent structural advances, the mechanisms that govern receptor-β-arrestin interactions at the plasma membrane of living cells remain elusive. Here, we combine single-molecule microscopy with molecular dynamics simulations to dissect the complex sequence of events involved in β-arrestin interactions with both receptors and the lipid bilayer.

Temperature and friction fluctuations inside a harmonic potential.

In this article we study the trapped motion of a molecule undergoing diffusivity fluctuations inside a harmonic potential. For the same diffusing-diffusivity process, we investigate two possible interpretations. Depending on whether diffusivity fluctuations are interpreted as temperature or friction fluctuations, we show that they display drastically different statistical properties inside the harmonic potential.

Post-operative electrical muscle stimulation attenuates loss of muscle mass and function following major abdominal surgery in older adults: a split body randomised control trial.

Introduction: Significant losses of muscle mass and function occur after major abdominal surgery. Neuromuscular electrical stimulation (NMES) has been shown to reduce muscle atrophy in some patient groups, but evidence in post-operative patients is limited. This study assesses the efficacy of NMES for attenuating muscle atrophy and functional declines following major abdominal surgery in older adults.

The respiratory depressant effects of mitragynine are limited by its conversion to 7-OH mitragynine.

Background And Purpose: Mitragynine, the major alkaloid in Mitragyna speciosa (kratom), is a partial agonist at the μ opioid receptor. CYP3A-dependent oxidation of mitragynine yields the metabolite 7-OH mitragynine, a more efficacious μ receptor agonist. While both mitragynine and 7-OH mitragynine can induce anti-nociception in mice, recent evidence suggests that 7-OH mitragynine formed as a metabolite is sufficient to explain the anti-nociceptive effects of mitragynine.

Detecting Transient Trapping from a Single Trajectory: A Structural Approach.

In this article, we introduce a new method to detect transient trapping events within a single particle trajectory, thus allowing the explicit accounting of changes in the particle's dynamics over time. Our method is based on new measures of a smoothed recurrence matrix. The newly introduced set of measures takes into account both the spatial and temporal structure of the trajectory.

PKA Cα subunit mutation triggers caspase-dependent RIIβ subunit degradation via Ser phosphorylation.

Mutations in the gene are the most frequent cause of cortisol-producing adrenocortical adenomas leading to Cushing's syndrome. encodes for the catalytic subunit α of protein kinase A (PKA). We already showed that mutations lead to impairment of regulatory (R) subunit binding.

Spatiotemporal GLP-1 and GIP receptor signaling and trafficking/recycling dynamics induced by selected receptor mono- and dual-agonists.

Objective: We assessed the spatiotemporal GLP-1 and GIP receptor signaling, trafficking, and recycling dynamics of GIPR mono-agonists, GLP-1R mono-agonists including semaglutide, and GLP-1/GIP dual-agonists MAR709 and tirzepatide.

Methods: Receptor G protein recruitment and internalization/trafficking dynamics were assessed using bioluminescence resonance energy transfer (BRET)-based technology and live-cell HILO microscopy.

Results: Relative to native and acylated GLP-1 agonists, MAR709 and tirzepatide showed preserved maximal cAMP production despite partial Gα recruitment paralleled by diminished ligand-induced receptor internalization at both target receptors.

G protein-coupled receptor-G protein interactions: a single-molecule perspective.

G protein-coupled receptors (GPCRs) regulate many cellular and physiological processes, responding to a diverse range of extracellular stimuli including hormones, neurotransmitters, odorants, and light. Decades of biochemical and pharmacological studies have provided fundamental insights into the mechanisms of GPCR signaling. Thanks to recent advances in structural biology, we now possess an atomistic understanding of receptor activation and G protein coupling.

PRKACB variants in skeletal disease or adrenocortical hyperplasia: effects on protein kinase A.

Genetic variants in components of the protein kinase A (PKA) enzyme have been associated with various defects and neoplasms in the context of Carney complex (CNC) and in isolated cases, such as in primary pigmented nodular adrenocortical disease (PPNAD), cortisol-producing adrenal adenomas (CPAs), and various cancers. PRKAR1A mutations have been found in subjects with impaired cAMP-dependent signaling and skeletal defects; bone tumors also develop in both humans and mice with PKA abnormalities. We studied the PRKACB gene in 148 subjects with PPNAD and related disorders, who did not have other PKA-related defects and identified two subjects with possibly pathogenic PRKACB gene variants and unusual bone and endocrine phenotypes.

Genomic and sequence variants of protein kinase A regulatory subunit type 1β (PRKAR1B) in patients with adrenocortical disease and Cushing syndrome.

Purpose: Protein kinase A (PKA) subunit defects (in PRKAR1A and PRKACA) are known to contribute to adrenal tumor pathogenesis. We studied the PRKAR1B gene for any genetic changes in bilateral adrenocortical hyperplasia (BAH) and cortisol-producing adrenal adenomas (CPA).

Methods: Exome sequencing and PRKAR1B copy-number variant (CNV) analysis were performed in 74 patients with BAH and 21 with CPA.

Super-resolution imaging reveals the nanoscale organization of metabotropic glutamate receptors at presynaptic active zones.

G protein-coupled receptors (GPCRs) play a fundamental role in the modulation of synaptic transmission. A pivotal example is provided by the metabotropic glutamate receptor type 4 (mGluR4), which inhibits glutamate release at presynaptic active zones (AZs). However, how GPCRs are organized within AZs to regulate neurotransmission remains largely unknown.