Intracellular Signaling Processes Research Articles

Genomic analysis of intracranial and subcortical brain volumes yields polygenic scores accounting for variation across ancestries.

Subcortical brain structures are involved in developmental, psychiatric and neurological disorders. Here we performed genome-wide association studies meta-analyses of intracranial and nine subcortical brain volumes (brainstem, caudate nucleus, putamen, hippocampus, globus pallidus, thalamus, nucleus accumbens, amygdala and the ventral diencephalon) in 74,898 participants of European ancestry. We identified 254 independent loci associated with these brain volumes, explaining up to 35% of phenotypic variance. We observed gene expression in specific neural cell types across differentiation time points, including genes involved in intracellular signaling and brain aging-related processes. Polygenic scores for brain volumes showed predictive ability when applied to individuals of diverse ancestries. We observed causal genetic effects of brain volumes with Parkinson's disease and attention-deficit/hyperactivity disorder. Findings implicate specific gene expression patterns in brain development and genetic variants in comorbid neuropsychiatric disorders, which could point to a brain substrate and region of action for risk genes implicated in brain diseases.

Cytokine-armed vaccinia virus promotes cytotoxicity toward pancreatic carcinoma cells via activation of human intermediary CD56dimCD16dim natural killer cells.

Pancreatic ductal adenocarcinoma (PDAC) remains a particularly aggressive disease with few effective treatments. The PDAC tumor immune microenvironment (TIME) is known to be immune suppressive. Oncolytic viruses can increase tumor immunogenicity via immunogenic cell death (ICD). We focused on tumor-selective (vvDD) and cytokine-armed Western-reserve vaccinia viruses (vvDD-IL2 and vvDD-IL15) and infected carcinoma cell lines as well as patient-derived primary PDAC cells. In co-culture experiments, we investigated the cytotoxic response and the activation of human natural killer (NK). Infection and virus replication were assessed by measuring virus encoded YFP. We then analyzed intracellular signaling processes and oncolysis via in-depth proteomic analysis, immunoblotting and TUNEL assay. Following the co-culture of mock or virus infected carcinoma cell lines with allogenic PBMCs or NK cell lines, CD56+ NK cells were analyzed with respect to their activation, cytotoxicity and effector function. Both, dose- and time-dependent release of danger signals following infection weremeasured. Viruses effectively entered PDAC cells, emitted YFP signals and resulted in concomitant oncolysis. The proteome showed reprogramming of normally active core signaling pathways in PDAC (e.g., MAPK-ERK signaling). Danger-associated molecular patterns were released upon infection and stimulated co-cultured NK cells for enhanced effector cytotoxicity. NK cell subtyping revealed enhanced numbers and activation of a rare CD56dimCD16dim population. Tumor cell killing was primarily triggered via Fas ligands rather than granule release, resulting in marked apoptosis. Overall, the cytokine-armed vaccinia viruses induced NK cell activation and enhanced cytotoxicity toward human PDAC cells in vitro. We could show that cytokine-armed virus targets the carcinoma cells and thus hasgreat potential to modulate the TIME in PDAC.

Genomic analysis of intracranial and subcortical brain volumes yields polygenic scores accounting for variation across ancestries.

Subcortical brain structures are involved in developmental, psychiatric and neurological disorders. We performed GWAS meta-analyses of intracranial and nine subcortical brain volumes (brainstem, caudate nucleus, putamen, hippocampus, globus pallidus, thalamus, nucleus accumbens, amygdala and, for the first time, the ventral diencephalon) in 74,898 participants of European ancestry. We identified 254 independent loci associated with these brain volumes, explaining up to 35% of phenotypic variance. We observed gene expression in specific neural cell types across differentiation time points, including genes involved in intracellular signalling and brain ageing-related processes. Polygenic scores for brain volumes showed predictive ability when applied to individuals of diverse ancestries. We observed causal genetic effects of brain volumes with Parkinson's disease and ADHD. Findings implicate specific gene expression patterns in brain development and genetic variants in comorbid neuropsychiatric disorders, which could point to a brain substrate and region of action for risk genes implicated in brain diseases.

Mapping the interaction site for β-arrestin-2 in the prokineticin 2 receptor

G protein-coupled receptors (GPCRs) are a family of cell membrane receptors that couple and activate heterotrimeric G proteins and their associated intracellular signalling processes after ligand binding. Although the carboxyl terminal of the receptors is essential for this action, it can also serve as a docking site for regulatory proteins such as the β-arrestins. Prokineticin receptors (PKR1 and PKR2) are a new class of GPCRs that are able to activate different classes of G proteins and form complexes with β-arrestins after activation by the endogenous agonists PK2. The aim of this work was to define the molecular determinants within PKR2 that are required for β-arrestin-2 binding and to investigate the role of β-arrestin-2 in the signalling pathways induced by PKR2 activation. Our data show that PKR2 binds constitutively to β-arrestin-2 and that this process occurs through the core region of the receptor without being affected by the carboxy-terminal region. Indeed, a PKR2 mutant lacking the carboxy-terminal amino acids retains the ability to bind constitutively to β-arrestin-2, whereas a mutant lacking the third intracellular loop does not. Overall, our data suggest that the C-terminus of PKR2 is critical for the stability of the β-arrestin-2-receptor complex in the presence of PK2 ligand. This leads to the β-arrestin-2 conformational change required to initiate intracellular signalling that ultimately leads to ERK phosphorylation and activation.

Transcriptional, growth factors, components of the AKT/mTOR signaling pathway, receptors and ligands of programmed cell death expression in melanoma

Introduction. Melanoma is the most dangerous neoplasm of the skin, characterized by a malignant and aggressive course. Transcriptional and growth factors, components of the AKT/mTOR signaling pathway, receptors and ligands of programmed cell death are involved in significant processes of oncogenesis.Aim. To study the expression of components of the AKT/mTOR (mTOR – mammalian target of rapamycin) signaling pathway, transcription and growth factors, expression of AMPK, LC3B, programmed cell death 1 (PD-1), programmed death-ligand 1 PD-L1 and programmed death-ligand 2 (PD-L2) in skin and mucosal tumor tissues.Materials and methods. The study included 21 patients with a verified diagnosis of melanoma of the skin of various localizations and mucous membranes of the nasal cavity T1a–4bN0M0 (I–IV stages) and 18 patients with basal cell carcinoma of the skin of various localizations T1–4N0M0 (I–VIA stages), aged 45 to 72 years old, who were treated in the department of head and neck tumors of the Cancer Research Institute, Tomsk National Research Medical Center. The presence of tumor ulceration was determined by microscopy and registration of the true absence of the epidermis over the tumor or due to traumatization of the epidermis. Expression of components of the AKT/mTOR signaling pathway, transcription and growth factors, expression of AMPK, LC3B, PD-1, PD-L1 and PD-L2 in the tumor tissue was determined by real-time polymerase chain reaction.Results. An increase in the expression of 70 S6 kinase and VHL was found in melanoma tissues compared to basal cell carcinoma. At the same time, the presence of signs of ulceration was associated with a low level of c-RAF, nuclear factor kappa B (NF-kB) p50 and hypoxia-inducible factor 1 (HIF-1) matrix RNA (mRNA) against the background of an increase in the expression of the hypoxia-inducible factor 2 (HIF-2) transcription factor. The study of the molecular features of neoplasms in relation to the tumor thickness according to Breslow revealed the contribution of transcription and growth factors, the intensity of intracellular signaling processes, modification of the microenvironment, autophagy and neoangiogenesis.Conclusion. The molecular and biological features of melanomas associated with invasive tumor growth have been identified. An increase in the expression of 70 S6 kinase and VHL are characteristic of a malignant skin tumor. The presence of signs of ulceration and tumor invasion were associated with a change in the transcriptional characteristics of factors with the induction of key markers, oncogenesis, which contributes to the formation of the invasive potential of the tumor.

Association between phthalate metabolite mixture in neonatal cord serum and birth outcomes

Prenatal exposure to phthalates (PAEs) is ubiquitous among Chinese neonates. PAEs entering the body will be transformed to various hydrolyzed and oxidated PAE metabolites (mPAEs). PAEs and mPAEs exposure may lead to adverse birth outcomes through disruption of multiple hormone signaling pathways, induction of oxidative stress, and alterations in intracellular signaling processes. In this study, the concentrations of 11 mPAEs in 318 umbilical cord serum samples from neonates in Jinan were quantified with HPLC-ESI-MS. Multiple linear regression, Bayesian kernel machine regression, and quantile g-computation models were utilized to investigate the effects of both individual mPAE and mPAE mixture on birth outcomes. Stratified analysis was performed to explore whether these effects were gender-specific. mPAE mixture was negatively associated with birth length (BL) z-score, birth weight (BW) z-score, head circumference (HC) z-score, and ponderal index (PI). Mono(2-ethylhexyl) phthalate (MEHP) manifested negative associations with BL(z-score), BW(z-score), HC(z-score), and PI, whereas mono(2-carboxymethylhexyl) phthalate (MCMHP) was negatively associated with BW(z-score) and PI within the mPAE mixture. Stratified analysis revealed that the negative associations between mPAE mixture and four birth outcomes were attenuated in female infants, while the positive impact of mono(2-ethyl-5carboxypentyl) phthalate (MECPP) on BL(z-score) and BW(z-score) could be detected only in females. In summary, our findings suggest that prenatal exposure to phthalates may be associated with intrauterine growth restriction, and these effects vary according to the gender of the infant.

Epigenetic Alterations in Alzheimer's Disease: Impact on Insulin Signaling and Advanced Drug Delivery Systems.

Alzheimer's disease (AD) is a neurodegenerative condition that predominantly affects the hippocampus and the entorhinal complex, leading to memory lapse and cognitive impairment. This can have a negative impact on an individual's behavior, speech, and ability to navigate their surroundings. AD is one of the principal causes of dementia. One of the most accepted theories in AD, the amyloid β (Aβ) hypothesis, assumes that the buildup of the peptide Aβ is the root cause of AD. Impaired insulin signaling in the periphery and central nervous system has been considered to have an effect on the pathophysiology of AD. Further, researchers have shifted their focus to epigenetic mechanisms that are responsible for dysregulating major biochemical pathways and intracellular signaling processes responsible for directly or indirectly causing AD. The prime epigenetic mechanisms encompass DNA methylation, histone modifications, and non-coding RNA, and are majorly responsible for impairing insulin signaling both centrally and peripherally, thus leading to AD. In this review, we provide insights into the major epigenetic mechanisms involved in causing AD, such as DNA methylation and histone deacetylation. We decipher how the mechanisms alter peripheral insulin signaling and brain insulin signaling, leading to AD pathophysiology. In addition, this review also discusses the need for newer drug delivery systems for the targeted delivery of epigenetic drugs and explores targeted drug delivery systems such as nanoparticles, vesicular systems, networks, and other nano formulations in AD. Further, this review also sheds light on the future approaches used for epigenetic drug delivery.

Deep quantitative proteomics of North American Pacific coast star tunicate (Botryllus schlosseri).

Botryllus schlosseri, is a model marine invertebrate for studying immunity, regeneration, and stress-induced evolution. Conditions for validating its predicted proteome were optimized using nanoElute® 2 deep-coverage LCMS, revealing up to 4930 protein groups and 20,984 unique peptides per sample. Spectral libraries were generated and filtered to remove interferences, low-quality transitions, and only retain proteins with>3 unique peptides. The resulting DIA assay library enabled label-free quantitation of 3426 protein groups represented by 22,593 unique peptides. Quantitative comparisons of single systems from a laboratory-raised with two field-collected populations revealed (1) a more unique proteome in the laboratory-raised population, and (2) proteins with high/low individual variabilities in each population. DNA repair/replication, ion transport, and intracellular signaling processes were distinct in laboratory-cultured colonies. Spliceosome and Wnt signaling proteins were the least variable (highly functionally constrained) in all populations. In conclusion, we present the first colonial tunicate's deep quantitative proteome analysis, identifying functional protein clusters associated with laboratory conditions, different habitats, and strong versus relaxed abundance constraints. These results empower research on B. schlosseri with proteomics resources and enable quantitative molecular phenotyping of changes associated with transfer from in situ to ex situ and from in vivo to in vitro culture conditions.

A Comparative Study for Localization of Odontoclast in Crown and Root of Physiological Resorbed Primary Teeth

Root and crown resorption is a physiologic event for the primary teeth. It is still unclear whether odontoclasts, the cells which resorb the dental har d tissue, are different from the osteoclasts, the cells that resorb bone. Dental tissue resorption seems to be initiated and regulated by the stellate reticulum and the dental follicle of the underlying permanent tooth via the secretion of stimulatory molecules, i.e. cytokines and transcription factors. The primary teeth resorption process is regulated in a manner similar to bone remodeling, involving the same receptor ligand system known as RANK/RANKL (receptor activator of nuclear factor-kappa B/ RANK Ligand), which represent two cytokine-like proteins of the tumor necrosis factor superfamily, are localized on bone cells and dental cells .They are crucial for the regulation of osteoclastic/odontoclast cell differentiation and also for the upregulation of mature osteoclasts/odontoclasts mediated by cell-to-cell contact and a subsequent cascade of diverse intracellular signaling processes .The aim of the present study was to localize and compare the IHC rea ctions for RANKL along root surface and the crown of human phs iological resorbed primary teeth. Fifteen human upper deciduous (second molar) teeth ,undergoing root and crown resorption wer e used for immunohistochemical study to identify RANKL expre ssion. The results demonstrated a high mean of expression of R ANKL in root as compared with crown in human primary shedding teeth. The present study concludes that RANKL play a role in res orption process of the primary teeth.

DARTS: an open-source Python pipeline for Ca2+ microdomain analysis in live cell imaging data.

Ca2+ microdomains play a key role in intracellular signaling processes. For instance, they mediate the activation of T cells and, thus, the initial adaptive immune system. They are, however, also of utmost importance for activation of other cells, and a detailed understanding of the dynamics of these spatially localized Ca2+ signals is crucial for a better understanding of the underlying signaling processes. A typical approach to analyze Ca2+ microdomain dynamics is live cell fluorescence microscopy imaging. Experiments usually involve imaging a larger number of cells of different groups (for instance, wild type and knockout cells), followed by a time consuming image and data analysis. With DARTS, we present a modular Python pipeline for efficient Ca2+ microdomain analysis in live cell imaging data. DARTS (Deconvolution, Analysis, Registration, Tracking, and Shape normalization) provides state-of-the-art image postprocessing options like deep learning-based cell detection and tracking, spatio-temporal image deconvolution, and bleaching correction. An integrated automated Ca2+ microdomain detection offers direct access to global statistics like the number of microdomains for cell groups, corresponding signal intensity levels, and the temporal evolution of the measures. With a focus on bead stimulation experiments, DARTS provides a so-called dartboard projection analysis and visualization approach. A dartboard projection covers spatio-temporal normalization of the bead contact areas and cell shape normalization onto a circular template that enables aggregation of the spatiotemporal information of the microdomain detection results for the individual cells of the cell groups of interest. The dartboard visualization allows intuitive interpretation of the spatio-temporal microdomain dynamics at the group level. The application of DARTS is illustrated by three use cases in the context of the formation of initial Ca2+ microdomains after cell stimulation. DARTS is provided as an open-source solution and will be continuously extended upon the feedback of the community. Code available at: 10.5281/zenodo.10459243.

Based on virtual screening methods and biological activity assessment, AK-968/13030056 has been identified as a potential mTOR inhibitor

The dysregulation of the PI3K/Akt/mTOR signaling pathway is one of the crucial pathways, leading to cancer development. mTOR (Rapamycin/mammalian target of rapamycin) participates in various intracellular signaling processes, regulating cellular metabolism, proliferation, and apoptosis. Numerous mTOR inhibitors have entered clinical research but are not yet on the market. There is an urgent need to develop a drug discovery strategy to accelerate the process. This study applied a virtual screening strategy to identify an mTOR inhibitor with potential inhibitory activity against mTOR. Firstly, we employed the Vina software to dock active and inactive datasets with two proteins (4L23 and 4JT6). The sensitive protein which is based on the docking results and ROC curve analysis is selected. Then, using the KNIME molecular screening program, virtual screening, cluster analysis, and binding model analysis, the 14 hit compounds are identified. Thirdly, through kinase assay and anti-proliferative activity evaluation, the hit compound AK-968/13030056 was ultimately confirmed. Finally, we conducted molecular docking studies and anti-tumor activity research on this compound. The inhibition rate of this compound on mTOR kinase was 70.62 %, exhibiting the strongest inhibitory activity against MCF-7 cells with an IC50 of 7.49 ± 0.87 μM. Subsequently, the biocompatibility of this compound was confirmed through hemolysis testing. Pharmacological experiments including AO staining, JC-1 assays, cell migration, and quantitative real-time PCR analysis also validated its anti-tumor activity. This study has developed a precise and rapid drug discovery strategy, successfully identifying a novel compound with inhibitory activity against the mTOR protein.

Dipping contacts - a novel type of contact site at the interface between membraneless organelles and membranes.

Liquid-liquid phase separation is a major mechanism for organizing macromolecules, particularly proteins with intrinsically disordered regions, in compartments not limited by a membrane or a scaffold. The cell can therefore be perceived as a complex emulsion containing many of these membraneless organelles, also referred to as biomolecular condensates, together with numerous membrane-bound organelles. It is currently unclear how such a complex concoction operates to allow for intracellular trafficking, signaling and metabolic processes to occur with high spatiotemporal precision. Based on experimental observations of synaptic vesicle condensates - a membraneless organelle that is in fact packed with membranes - we present here the framework of dipping contacts: a novel type of contact site between membraneless organelles and membranes. In this Hypothesis, we propose that our framework of dipping contacts can serve as a foundation to investigate the interface that couples the diffusion and material properties of condensates to biochemical processes occurring in membranes. The identity and regulation of this interface is especially critical in the case of neurodegenerative diseases, where aberrant inclusions of misfolded proteins and damaged organelles underlie cellular pathology.

G Protein Subunit Beta 3 (GNB3) Variant Is Associated with Biochemical Changes in Brazilian Patients with Hypertension.

Central Illustration : G Protein Subunit Beta 3 (GNB3) Variant Is Associated with Biochemical Changes in Brazilian Patients with Hypertension. Genes and their variants associated with environmental factors contribute to the development of the hypertensive phenotype. The G protein beta 3 subunit gene (GNB3) is involved in the intracellular signaling process, and its variants have been related to susceptibility to arterial hypertension. To determine the association of the GNB3 variant (rs5443:C>T) with arterial hypertension, biochemical parameters, age, and obesity in hypertensive and normotensive individuals from Ouro Preto, Minas Gerais, Brazil. The identification of variants was performed by real-time PCR, using the TaqMan® system, in 310 samples (155 hypertensive and 155 normotensive). Biochemical analyses (renal function, lipid profile and glycemia) were performed from the serum using UV/Vis spectrophotometry and ion-selective electrode. A multiple logistic regression model was used to identify factors associated with arterial hypertension. The analysis of continuous variables with normal distribution was performed using the unpaired Student's t test; non-normal data were analyzed using Mann-Whitney. P < 0.05 was considered significant. The rs5443:C>T variant was not associated with arterial hypertension in the evaluated population (p = 0.88). Regarding biochemical measures, the T allele was associated with high levels of triglycerides, glucose and uric acid in hypertensive individuals (p < 0.05). These results show the importance of genetic diagnosis to prevent the causes and consequences of diseases and imply that the GNB3 rs5443:C>T variant may be associated with changes in the biochemical profile in hypertensive individuals.

OR0304 Novel Dual Antagonists Of The Growth Hormone Receptor And The Prolactin Receptor

Abstract Disclosure: R. Basu: None. J.J. Kopchick: None. An excess of the human growth hormone (hGH) is associated with multiple pathophysiology including acromegaly, diabetes, cancer, renal dysfunction and age-associated cognitive impairment. On the other hand, a congenital lack of GH action in humans and mice render a protective effect from the above co-morbidities. Consequently, there exists significant pharmaceutical interest in developing antagonists of GH action - rendered via binding and activating the GHR, as well as the prolactin receptor (PRLR), which is particularly relevant for PRLR-rich cancers of the breast and prostate. Our laboratory has pioneered the discovery of the first and only FDA approved GHR antagonist - Somavert (pegvisomant for injection, Pfizer Inc., USA) - currently prescribed for the treatment of acromegaly. Here we present two new and unique designs of antagonists which block the complete spectrum of GH action at both GHR and PRLR binding. The first GHR antagonist design is a full-length G120K-hGH peptide at the core, incorporating targeted cysteine (single or double) substitutions at carefully selected solvent-accessible residues distal to the binding sites. To these substituted cysteines, maleimide activated discrete PEGs (MAL-dPEG; neutral or anionic, branched, different sizes) were specifically conjugated to build a library of multiple putative GHR antagonists. Binding studies and biochemical activities reveal multiple promising GHRA candidates with high binding affinities to both GHR and PRLR, while the biological assays show robust inhibition of GH driven intracellular signaling and oncogenic processes in cultured human cancer cell lines. Intraperitoneal administration of a selected candidate (compound-G) in mice significantly reduced serum IGF1 and IGFBP3 as well, confirming in vivo efficacy. The second candidate antagonist termed ‘S1H’ is a 16-amino-acid peptide designed as a direct sequence mimetic of a unique fragment of the site-1 binding helix of the hGH molecule. To this end we have characterized S1H with mass spectrometry, circular dichroism spectropolarimetry, and in vitro biological assays using human cell lines expressing GHR. S1H inhibited GH as well as PRL induced STAT5 phosphorylation in a dose-dependent manner in multiple cell lines. Moreover, using alanine scanning mutagenesis studies, we identified a strong correlation between the helical propensity and biological activity of S1H - allowing extensive structure activity relationship studies. Thus, we present two distinct designs, preparation and characterization of dual antagonists of the GH action at the level of GHR and PRLR, with prospective applications in pathologies associated with a GH excess and also as valuable compounds to study the nature of human GH-GHR interactions. We currently continue to develop both compounds for pre-clinical validations. Presentation: Thursday, June 15, 2023

Unraveling Mechanisms of Autoimmune Skin Blistering: Applying Single-Cell Transcriptomics to Pemphigus B Cells

Unraveling Mechanisms of Autoimmune Skin Blistering: Applying Single-Cell Transcriptomics to Pemphigus B Cells

Crosstalk between Circulating Tumor Cells and Plasma Proteins-Impact on Coagulation and Anticoagulation.

Cancer metastasis is a complex process. After their intravasation into the circulation, the cancer cells are exposed to a harsh environment of physical and biochemical hazards. Whether circulating tumor cells (CTCs) survive and escape from blood flow defines their ability to metastasize. CTCs sense their environment with surface-exposed receptors. The recognition of corresponding ligands, e.g., fibrinogen, by integrins can induce intracellular signaling processes driving CTCs' survival. Other receptors, such as tissue factor (TF), enable CTCs to induce coagulation. Cancer-associated thrombosis (CAT) is adversely connected to patients' outcome. However, cancer cells have also the ability to inhibit coagulation, e.g., through expressing thrombomodulin (TM) or heparan sulfate (HS), an activator of antithrombin (AT). To that extent, individual CTCs can interact with plasma proteins, and whether these interactions are connected to metastasis or clinical symptoms such as CAT is largely unknown. In the present review, we discuss the biological and clinical relevance of cancer-cell-expressed surface molecules and their interaction with plasma proteins. We aim to encourage future research to expand our knowledge of the CTC interactome, as this may not only yield new molecular markers improving liquid-biopsy-based diagnostics but also additional targets for better cancer therapies.

Biochemical aspects of magnesium-enhanced bone regeneration

Current research is focused on practical implications of magnesium-based implants largely due to their biodegradability and ability to promote bone healing and formation. However, the mechanism underlying the osteogenesis regulation by magnesium is still unclear.We describe cellular and molecular mechanisms underlying the effect of magnesium ions (Mg2+) on bone growth following the device implantation. The presented data demonstrate magnesium-induced activation of canonical Wnt/β-catenin signaling pathway in human bone marrow stromal cells resulting in their differentiation into osteoblasts, osteogenic effect and recovery of bone defects. We describe the role of the molecular mechanisms responsible for osteopromotive properties of Mg2+ and associated with unique transient receptor potential melastatin 7 (TRPM7) cation channels mediating the Mg2+ influx. TRPM7-mediated Mg2+ influx is important for platelet-derived growth factor (PDGF)-induced proliferation, adhesion, and migration of human osteoblasts, as well as for promotion of Mg2+-associated bone regeneration.We discuss the effect of Mg2+ on intracellular signaling processes, expression of the vascular endothelial growth factor (VEGF), hypoxia-inducible factor-2α, and peroxisome proliferator-activated receptor-γ coactivator 1α. Mg2+ can promote bone regeneration by enhancing the production of type X collagen and VEGF by osteogenic cells in bone marrow.

Identification of key factors driving inflammation-induced sensitization of muscle sensory neurons.

Sensory neurons embedded in muscle tissue that initiate pain sensations, i.e., nociceptors, are temporarily sensitized by inflammatory mediators during musculoskeletal trauma. These neurons transduce peripheral noxious stimuli into an electrical signal [i.e., an action potential (AP)] and, when sensitized, demonstrate lower activation thresholds and a heightened AP response. We still do not understand the relative contributions of the various transmembrane proteins and intracellular signaling processes that drive the inflammation-induced hyperexcitability of nociceptors. In this study, we used computational analysis to identify key proteins that could regulate the inflammation-induced increase in the magnitude of AP firing in mechanosensitive muscle nociceptors. First, we extended a previously validated model of a mechanosensitive mouse muscle nociceptor to incorporate two inflammation-activated G protein-coupled receptor (GPCR) signaling pathways and validated the model simulations of inflammation-induced nociceptor sensitization using literature data. Then, by performing global sensitivity analyses that simulated thousands of inflammation-induced nociceptor sensitization scenarios, we identified three ion channels and four molecular processes (from the 17 modeled transmembrane proteins and 28 intracellular signaling components) as potential regulators of the inflammation-induced increase in AP firing in response to mechanical forces. Moreover, we found that simulating single knockouts of transient receptor potential ankyrin 1 (TRPA1) and reducing the rates of Gαq-coupled receptor phosphorylation and Gαq subunit activation considerably altered the excitability of nociceptors (i.e., each modification increased or decreased the inflammation-induced fold change in the number of triggered APs compared to when all channels were present). These results suggest that altering the expression of TRPA1 or the concentration of intracellular Gαq might regulate the inflammation-induced increase in AP response of mechanosensitive muscle nociceptors.

Monitoring the Reversibility of GPCR Signaling by Combining Photochromic Ligands with Label‐free Impedance Analysis

AbstractG protein‐coupled cell surface receptors (GPCR) trigger complex intracellular signaling cascades upon agonist binding. Classic pharmacological assays provide information about binding affinities, activation or blockade at different stages of the signaling cascade, but real time dynamics and reversibility of these processes remain often disguised. We show that combining photochromic NPY receptor ligands, which can be toggled in their receptor activation ability by irradiation with light of different wavelengths, with whole cell label‐free impedance assays allows observing the cell response to receptor activation and its reversibility over time. The concept demonstrated on NPY receptors may be well applicable to many other GPCRs providing a deeper insight into the time course of intracellular signaling processes.

Monitoring the Reversibility of GPCR Signaling by Combining Photochromic Ligands with Label-free Impedance Analysis.

G protein-coupled cell surface receptors (GPCR) trigger complex intracellular signaling cascades upon agonist binding. Classic pharmacological assays provide information about binding affinities, activation or blockade at different stages of the signaling cascade, but real time dynamics and reversibility of these processes remain often disguised. We show that combining photochromic NPY receptor ligands, which can be toggled in their receptor activation ability by irradiation with light of different wavelengths, with whole cell label-free impedance assays allows observing the cell response to receptor activation and its reversibility over time. The concept demonstrated on NPY receptors may be well applicable to many other GPCRs providing a deeper insight into the time course of intracellular signaling processes.