Diverse Signaling Research Articles

Mask-Free Direct Printing of Highly Customizable, Conformable, Robust, and Recyclable Microelectrodes for Advanced Curvy Electronics.

Highly conformal and mechanically robust curvy electronics that seamlessly adapt to sophisticated and unpredictable 3D geometries provide breakthrough solutions in advanced fields such as health monitoring, wireless energy transmission, and human-computer interface. Nevertheless, existing material choices along with manufacturing techniques substantially impede these electronics from achieving their full potential. This study presents a mask-free and straightforward direct writing and transfer (DW&T) technique that employs a polytetrafluoroethylene film as a temporary substrate, utilizing the phase transition of printed electrodes between hydrogel and dry states to enable cost-effective fabrication of conformally adhering conductive microelectrode patterns on nearly all 3D surfaces. The resultant microelectrodes demonstrate extensively adjustable feature dimensions (linewidth 50-400 µm; height 0.07-2.3 µm; pitch 20 µm in minimum) and possess distinct electrical and optical characteristics, in addition to exhibiting significant stability under severe bending and stretching strains and recyclability. To demonstrate the capabilities of the DW&T, imperceptible and customizable substrate-free electronic skin (e-skin) on human skin is developed. The e-skin maintains ultraconformal and seamless contact with the skin, does not impede the natural sensations and physiological changes of its hosts, and achieves high-fidelity recording of diverse electrophysiological signals.

Identification of HOXA9 methylation as an epigenetic biomarker predicting prognosis and guiding treatment choice in acute myeloid leukemia

BackgroundThe homeobox (HOX) genes especially for HOXA cluster play crucial roles in leukemogenesis. HOXA overexpression caused by genetic alterations, such as KMT2A rearrangements, NUP98- fusions and FLT3-ITD mutations, is frequently identified in AML. However, very few studies determined the DNA methylation-mediated epigenetic regulation of the HOXA cluster genes in AML.MethodsWe systematically first screened the prognostic value of HOXA cluster genes methylation in AML from The Cancer Genome Atlas (TCGA) datasets. Afterwards, the candidate prognosis-related gene HOXA9 were selected for clinical relevance analysis and were further validated in another independent cohort from our research center.ResultsThe methylation of HOXA9, among HOXA cluster genes, negatively correlated with adverse prognosis and expression were screened and identified in AML among TCGA datasets. Clinically, HOXA9 hypomethylation was positively correlated with specific subtypes of AML, such as French-American-British (FAB)-M5/M7, normal karyotype and FLT3, NPM1 and DNMT3A mutation, whereas negatively associated with FAB-M3, t(15;17), t(8;21) and t(16;16). Importantly, AML patients with HOXA9 hypomethylation may profit from transplantation, whereas AML patients with HOXA9 hypermethylation could not, suggesting that HOXA9 methylation may be used to guide therapeutic selection between transplantation and chemotherapy. Bioinformatics analysis demonstrated the association of HOXA9 expression with diverse leukemia-related genes (HOXAs, SOSTDC1, MEG3, miR-10a, miR-381 and miR-193b) and signaling pathways (PI3K-Akt signaling) in AML. Subsequently, we further validate the hypomethylation pattern of HOXA9 in AML patients and the epigenetic regulation of HOXA9 methylation in AML cell-lines.ConclusionsHOXA9 methylation linked to HOXA9 expression correlates with diverse genetic abnormalities of AML, such as normal karyotype, t(15;17), t(8;21), t(16;16) and FLT3, NPM1 and DNMT3A mutations. Moreover, HOXA9 hypomethylation may be associated with adverse prognosis, and may guide treatment choice in AML.

Phospho-seq: integrated, multi-modal profiling of intracellular protein dynamics in single cells

Cell signaling plays a critical role in neurodevelopment, regulating cellular behavior and fate. While multimodal single-cell sequencing technologies are rapidly advancing, scalable and flexible profiling of cell signaling states alongside other molecular modalities remains challenging. Here we present Phospho-seq, an integrated approach that aims to quantify cytoplasmic and nuclear proteins, including those with post-translational modifications, and to connect their activity with cis-regulatory elements and transcriptional targets. We utilize a simplified benchtop antibody conjugation method to create large custom neuro-focused antibody panels for simultaneous protein and scATAC-seq profiling on whole cells, alongside both experimental and computational strategies to incorporate transcriptomic measurements. We apply our workflow to cell lines, induced pluripotent stem cells, and months-old retinal and brain organoids to demonstrate its broad applicability. We show that Phospho-seq can provide insights into cellular states and trajectories, shed light on gene regulatory relationships, and help explore the causes and effects of diverse cell signaling in neurodevelopment.

Brainstem neuropeptidergic neurons link a neurohumoral axis to satiation.

Hunger is evolutionarily hardwired to ensure that an animal has sufficient energy to survive and reproduce. Just as important as knowing when to start eating is knowing when to stop eating. Here, using spatially resolved single-cell phenotyping, we characterize a population of neuropeptidergic neurons in the brainstem's dorsal raphe nucleus (DRN) and describe how they regulate satiation. These neurons track food from sensory presentation through ingestion, integrate these signals with slower-acting humoral cues, and express cholecystokinin (CCK). These CCK neurons bidirectionally regulate meal size, driving a sustained meal termination signal with a built-in delay. They are also well positioned to sense and respond to ingestion: they express a host of metabolic signaling factors and are integrated into an extended network known to regulate feeding. Together, this work demonstrates how DRN CCK neurons regulate satiation and identifies a likely conserved cellular mechanism that transforms diverse neurohumoral signals into a key behavioral output.

Targeting SIRT1 by Scopoletin to Inhibit XBB.1.5 COVID-19 Life Cycle.

Natural products have historically driven pharmaceutical discovery, but their reliance has diminished with synthetic drugs. Approximately 35% of medicines originate from natural products. Scopoletin, a natural coumarin compound found in herbs, exhibits antioxidant, hepatoprotective, antiviral, and antimicrobial properties through diverse intracellular signaling mechanisms. Furthermore, it also enhances the activity of antioxidants. Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) causes viral pneumonia through cytokine storms and systemic inflammation. Cellular autophagy pathways play a role in coronavirus replication and inflammation. The Silent Information Regulator 1 (SIRT1) pathway, linked to autophagy, protects cells via FOXO3, inhibits apoptosis, and modulates SIRT1 in type-II epithelial cells. SIRT1 activation by adenosine monophosphate-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR) enhances the autophagy cascade. This pathway holds therapeutic potential for alveolar and pulmonary diseases and is crucial in lung inflammation. Angiotensin-converting enzyme 2 (ACE-2) activation, inhibited by reduced expression, prevents COVID-19 virus entry into type-II epithelial cells. The coronavirus disease 2019 (COVID-19) virus binds ACE-2 to enter into the host cells, and XBB.1.5 COVID-19 displays high ACE-2-binding affinity. ACE-2 expression in pneumocytes is regulated by signal transducers and activators of transcription-3 (STAT3), which can increase COVID-19 virus replication. SIRT1 regulates STAT3, and the SIRT1/STAT3 pathway is involved in lung diseases. Therapeutic regulation of SIRT1 protects the lungs from inflammation caused by viral-mediated oxidative stress. Scopoletin, as a modulator of the SIRT1 cascade, can regulate autophagy and inhibit the entry and life cycle of XBB.1.5 COVID-19 in host cells.

Species-specific optimization of oxylipin ionization in LC-MS: a design of experiments approach to improve sensitivity.

Oxylipins are diverse bioactive signaling molecules, which occur in very low concentrations in complex matrices, posing challenges in achieving consistent and sensitive analysis. UHPLC-MS/MS is the preferred technique to separate and quantify these molecules, often optimized using a time-consuming trial-and-error approach. In this study, we applied the design of experiments (DoE) approach to systematically investigate the ionization properties of multiple oxylipin species. Fractional factorial and central composite designs were employed to detect relevant instrument parameters and optimize signal intensity in ESI-MS/MS analysis. Response surface modeling revealed distinct ionization and fragmentation behaviors between polar and apolar oxylipins, driven by their responses to interface temperature and collision-induced dissociation (CID) gas pressure. Particularly, prostaglandins and lipoxins benefit from higher CID gas pressure and lower temperatures compared to the lipophilic HODEs and HETEs to achieve optimal intensity in multiple reaction monitoring analysis. While global source parameters were optimized, analyte-specific entrance/exit potentials and collision energies required individual adjustments. The final method was applied to analyze seven oxylipin classes including leukotrienes, prostaglandins, lipoxins, resolvins, HETEs, HODES, and HoTrEs. Although improvements in lower limits of quantification were modest (< 1pg on-column), signal-to-noise ratios increased two-fold for lipoxins and resolvins and three- to four-fold for leukotrienes and HETEs, enhancing detection at trace levels. This DoE-guided strategy provides a powerful tool to improve UHPLC-MS/MS analysis of oxylipins across various instrument vendors, guiding the way towards inter-laboratory comparability.

The Role of Pomegranate (Punica granatum) in Cancer Prevention and Treatment: Modulating Signaling Pathways From Inflammation to Metastasis.

Punica granatum, commonly known as pomegranate, is a traditional medicinal agent owing to its antiquity. The scientific literature has shown that pomegranate extracts exhibit favorable modulation of diverse signaling pathways. These pathways encompass those implicated in inflammation, angiogenesis, hyperproliferation, cellular transformation, tumorigenesis initiation, and ultimately, a reduction in advanced metastasis and tumorigenesis. Pomegranate extracts in this context can be attributed to their high polyphenol content, which has been observed to possess inhibitory properties toward specific signaling pathways associated with cancer. As a formidable pathology, cancer is the most significant cause of death worldwide after cardiovascular disease. The annual incidence of cancer-related mortality has increased progressively. Modifying one's dietary patterns, engaging in regular physical exercise, and maintaining an optimal body mass index are three straightforward measures that an individual may undertake to mitigate their susceptibility to cancer. Incorporating diverse vegetables and fruits into one's dietary regimen exhibits promising potential for preventing a minimum of 20% cancer incidence and approximately 200,000 cancer-related mortalities annually. Vegetables and fruits contain high levels of minerals and phytochemicals, which help alleviate and prevent the harmful effects of cancer. These substances are safe and exhibit minimal toxicity in biological systems. Furthermore, they exhibit antioxidant properties and have garnered extensive approval for their use as nutritional supplements. Pomegranates are used in ancient cultures to prevent and treat various diseases. Extensive research on pomegranate extract, fruit, oil, and juice has revealed promising findings regarding their potential anti-proliferative, anti-tumorigenic, and anti-inflammatory properties through the modification of various signaling pathways related to cancer, thus demonstrating their potential as drugs to prevent and treat cancer. Emerging research indicates that pomegranate can potentially prevent and treat different cancers, including prostate, bladder, breast, skin, lung, and colon cancer.

A Comprehensive Appraisal of Bisbenzylisoquinoline Alkaloids Isolated From Genus Cyclea for Anticancer Potential.

The pharmaceutical industry and academia are continuously searching for novel and effective anticancer lead compounds to ensure patient safety, provide a cure, and surpass all other obstacles. Given the indeterminate nature of cancer etiology, the importance of drugs capable of targeting multiple pathways cannot be overstated. Among naturally occurring compounds, bisbenzylisoquinoline (BBIQ) alkaloids, such as berberine, tetrandrine, chelidonine, and berbamine, have demonstrated significant anticancer potential by modulating diverse signaling pathways. Several of these compounds are currently in clinical trials, highlighting their relevance in cancer treatment. This review emphasizes the need for further investigation into the anticancer properties of BBIQ alkaloids, particularly those isolated from eight Cyclea species in India. With around 27 BBIQ alkaloids identified, these compounds hold promise, especially in combating multidrug resistance-a critical challenge in cancer therapy. Given the rising cancer incidence, these alkaloids warrant a deeper exploration of their therapeutic potential.

Transcellular regulation of ETI-induced cell death.

To address the persistent challenge of cell death spread and limitation during effector-triggered immunity (ETI), we propose a 'concentric circle' model. This model outlines a regulatory framework, integrating multiple cells and diverse signaling molecules, including salicylic acid (SA), jasmonic acid (JA), and Ca2+. By accounting for the varying concentrations and spatiotemporal distributions of these molecules, our model aims for precision in immune defense and regulated cell death. To validate this model, a pathosystem-triggering ETI without pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) is required. Here, we review potential ETI elicitors, including victorin, thaxtomin A, and second messengers. We anticipate that future discovery of 'pure' ETI-triggering effectors will provide deeper insights into the transcellular regulation of immune response in plants.

Dual Ionic Signal Detection: Modulation of Surface Charge of Nanofluidic Iontronics by Dual-Split Gate Voltages.

Nanofluidic iontronics, including the field-effect ionic diode (FE-ID) and field-effect ionic transistor (FE-IT), represent emerging nanofluidic logic devices that have been employed in sensitive analyses. Making analyte recognitions in predefined nanofluidic devices has been verified to improve the sensitivity and selectivity using a single ionic signal, such as ionic current amplification, rectification, and Coulomb blockade. However, the detection of analytes in complex systems generally necessitates more diverse signals beyond just ionic currents. Here, we demonstrated that dual ionic signals, steady ionic switching ratio, and transient response time (ts) act as detection signals modulated by dual-split gate voltages along the nanochannel for the detection of charged analytes. With an increase in gate voltage, the switching ratio decreases in both FE-ID and FE-IT, whereas the response time exhibits an exponential increase specifically in the FE-ID. Moreover, the response time shows no significant correlation with the external transmembrane voltage in the FE-IT. These results contribute to the optimization of reconfigurable iontronics through gate voltage modulation, providing a theoretical foundation for multiple ionic signal detection.

MXene–MWCNT Conductive Network for Long-Lasting Wearable Strain Sensors with Gesture Recognition Capabilities

In this work, a conductive composite film composed of multi-walled carbon nanotubes (MWCNTs) and multi-layer Ti3C2Tx MXene nanosheets is used to construct a strain sensor on sandpaper Ecoflex substrate. The composite material forms a sophisticated conductive network with exceptional electrical conductivity, resulting in sensors with broad detection ranges and high sensitivities. The findings indicate that the strain sensing range of the Ecoflex/Ti3C2Tx/MWCNT strain sensor, when the mass ratio is set to 5:2, extends to 240%, with a gauge factor (GF) of 933 within the strain interval from 180% to 240%. The strain sensor has demonstrated its robustness by enduring more than 33,000 prolonged stretch-and-release cycles at 20% cyclic tensile strain. Moreover, a fast response time of 200 ms and detection limit of 0.05% are achieved. During application, the sensor effectively enables the detection of diverse physiological signals in the human body. More importantly, its application in a data glove that is coupled with machine learning and uses the Support Vector Machine (SVM) model trained on the collected gesture data results in an impressive recognition accuracy of 93.6%.

A General Mechanism for Initiating the General Stress Response in Bacteria.

The General Stress Response promotes survival of bacteria in adverse conditions, but how sensor proteins transduce species-specific signals to initiate the response is not known. The serine/threonine phosphatase RsbU initiates the General Stress Response in B. subtilis upon binding a partner protein (RsbT) that is released from sequestration by environmental stresses. We report that RsbT activates RsbU by inducing otherwise flexible linkers of RsbU to form a short coiled-coil that dimerizes and activates the phosphatase domains. Importantly, we present evidence that related coiled-coil linkers and phosphatase dimers transduce signals from diverse sensor domains to control the General Stress Response and other signaling across bacterial phyla. This coiled-coil linker transduction mechanism additionally suggests a resolution to the mystery of how shared sensory domains control serine/threonine phosphatases, diguanylate cyclases and histidine kinases. We propose that this provides bacteria with a modularly exchangeable toolkit for the evolution of diverse signaling pathways.

Prediction of Multi-targeting Pharmacological Activity of Bioactive Compounds from Medicinal Plants Against Hepatocellular Carcinoma Through Advanced Network Pharmacology and Bioinformatics-Based Investigation.

The primary objective of this study was to identify bioactive compounds from four medicinal plants with multi-targeting activity against hepatocellular carcinoma (HCC). A comprehensive analysis led to the identification of a subset of compounds possessing favorable drug-likeness, pharmacokinetics, and absence of toxicity profiles. Target analysis for 42 phytochemicals revealed 210 potential targets associated with HCC. Protein-protein interaction (PPI) analysis of these targets uncovered five critical hub genes, STAT3, SRC, AKT1, MAPK3, and EGFR, in our study. Correlation analysis of these hub genes indicated a strong positive correlation between EGFR, MAPK3, and SRC expression highlighting their interconnected roles in HCC. Survival analysis underscored the significant prognostic role of these hub genes in HCC underscoring their potential as biomarkers. The co-expression analysis unveiled an intricate network of interactions among the hub genes, while the enrichment analysis demonstrated their enrichment in diverse biological and signaling pathways related to HCC. Molecular docking analysis between the seven phytochemicals and five identified targets revealed that bauerenol exhibited good affinity towards all the targets. Subsequent molecular dynamics (MD) simulations demonstrated that bauerenol formed stable complexes with STAT3, AKT1, EGFR, and MAPK3, suggesting its potential as a multi-targeted inhibitor. Our research suggests that bauerenol shows promise as an inhibitor for HCC targets and stands out as a notable lead compound. However, further experimental studies are necessary to confirm its activity and to evaluate its potential as a therapeutic agent for HCC.

Neurons as Immunomodulators: From Rapid Neural Activity to Prolonged Regulation of Cytokines and Microglia.

Regulation of the brain's neuroimmune system is central to development, normal function, and disease. Neuronal communication to microglia, the primary immune cells of the brain, is well known to involve purinergic signaling mediated via ATP secretion and the cytokine fractalkine. Recent evidence shows that neurons release multiple cytokines beyond fractalkine, yet these are less studied and poorly understood. In contrast to ATP, cytokines are a class of signaling molecule that are much larger, with longer signaling and farther diffusion. We posit that neuron-expressed cytokines are an essential mechanism of neuron-microglia communication that arises as part of both normal learning and memory and in response to tissue pathology. Thus, neurons are underappreciated immunomodulatory cells that express diverse immunomodulatory signals. While neuronally sourced cytokines have been understudied, new technical advances make this a timely topic. The goal of this review is to define what is known about the cytokines expressed from neurons, how they are regulated, and the effects of these cytokines on microglia. We delineate key knowledge gaps and needs for new tools to define and analyze neuronal roles in immunomodulation. Given that cytokines are central regulators of microglial function, a broad new body of work is required to illuminate functional links between these neuronally expressed cytokines and sustained and transient microglial function.

Genome-Wide Analysis and Expression Profiling of Watermelon VQ Motif-Containing Genes Under Abiotic and Biotic Stresses

Valine-glutamine (VQ) motif-containing proteins play important roles in diverse plant developmental processes and signal transduction in response to biotic and abiotic stresses. However, no systematic investigation has been conducted on VQ genes in watermelon. In this study, we identified 31 watermelon VQ genes, which were classified into six subfamilies (I–VI). All of the deduced proteins contained a conserved FxxxVQxL/F/VTG motif. Eleven ClVQs were involved in segment duplication, which was the main factor in the expansion of the VQ family in watermelon. Numerous stress- and hormone-responsive cis-elements were detected in the putative promoter region of the ClVQ genes. Green fluorescent protein fusion proteins for ten selected ClVQs were localized in the nucleus, but three ClVQs also showed signals in cell membranes and the cell wall, thus confirming their predicted divergent functionality. Quantitative real-time PCR (qRT-PCR) analysis indicated that the majority of ClVQ genes were specifically or preferentially expressed in certain tissues or organs, especially in the male flower. Analyses of RNA-sequencing data under osmotic, cold, and drought stresses and Cucumber green mottle mosaic virus (CGMMV) infection revealed that the majority of ClVQ genes, especially those from subfamily IV, were responsive to these stresses. The results provide useful information for the functional characterization of watermelon ClVQ genes to unravel their biological roles.

Light-eye-body axis: exploring the network from retinal illumination to systemic regulation.

The human body is an intricate system, where diverse and complex signaling among different organs sustains physiological activities. The eye, as a primary organ for information acquisition, not only plays a crucial role in visual perception but also, as increasing evidence suggests, exerts a broad influence on the entire body through complex circuits upon receiving light signals which is called non-image-forming vision. However, the extent and mechanisms of light's impact on the body through the eyes remain insufficiently explored. There is also a dearth of comprehensive reviews elucidating the intricate interplay between light, the eye, and the systemic connections to the entire body. Herein, we propose the concept of the light-eye-body axis to systematically encapsulate the extensive non-image-forming effects of light signals received by the retina on the entire body. We reviewed the visual-neural structure basis of the light-eye-body axis, summarized the mechanism by which the eyes regulate the whole body and the current research status and challenges within the physiological and pathological processes involved in the light-eye-body axis. Future research should aim to expand the influence of the light-eye-body axis and explore its deeper mechanisms. Understanding and investigating the light-eye-body axis will contribute to improving lighting conditions to optimize health and guide the establishment of phototherapy standards in clinical practice.

Intracellular metal ion-based chemistry for programmed cell death.

Intracellular metal ions play essential roles in multiple physiological processes, including catalytic action, diverse cellular processes, intracellular signaling, and electron transfer. It is crucial to maintain intracellular metal ion homeostasis which is achieved by the subtle balance of storage and release of metal ions intracellularly along with the influx and efflux of metal ions at the interface of the cell membrane. Dysregulation of intracellular metal ions has been identified as a key mechanism in triggering programmed cell death (PCD). Despite the importance of metal ions in initiating PCD, the molecular mechanisms of intracellular metal ions within these processes are infrequently discussed. An in-depth understanding and review of the role of metal ions in triggering PCD may better uncover novel tools for cancer diagnosis and therapy. Specifically, the essential roles of calcium (Ca2+), iron (Fe2+/3+), copper (Cu+/2+), and zinc (Zn2+) ions in triggering PCD are primarily explored in this review, and other ions like manganese (Mn2+/3+/4+), cobalt (Co2+/3+) and magnesium ions (Mg2+) are briefly discussed. Further, this review elaborates on the underlying chemical mechanisms and summarizes these metal ions triggering PCD in cancer therapy. This review bridges chemistry, immunology, and biology to foster the rational regulation of metal ions to induce PCD for cancer therapy.

Mathematical models of intercellular signaling in breast cancer.

The development and regulation of healthy and cancerous breast tissue is guided by communication between cells. Diverse signals are exchanged between cancer cells and non-cancerous cells of the tumor microenvironment (TME), influencing all stages of tumor progression. Mathematical models are essential for understanding how this complex network determines cancer progression and the effectiveness of treatment. We reviewed the current dynamical mathematical models of intercellular signaling in breast cancer, examining models with cancer cells only, fibroblasts, endothelial cells, macrophages and the immune system as whole. We categorized the goals and complexity of these models, to highlight how they can explain many features of cancer emergence and progression. We found that dynamical models of intercellular signaling can elucidate tissue-level dysregulation in cancer by explaining: i) maintenance of non-heritable intratumor phenotypic heterogeneity, ii) transitions between tumor dormancy and accelerated invasive growth, iii) stromal support of tumor vascularization and growth factor enrichment and iv) suppression of immune infiltration and cancer surveillance. These models also provide a framework to propose novel TME-targeting treatment strategies. However, most models were focused on a highly selected and small set of signaling interactions between a few cell types, and their translational applicability were severely limited by the availability of tumor-specific data for personalized model calibration. Mathematical models of breast cancer have many challenges and opportunities to incorporate signaling. The four key challenges are: 1) finding ways to treat signaling networks as a context-dependent language that incorporates non-linear and non-additive responses, 2) identifying the key cell phenotypes that signals control and understanding the feedbacks between signals and phenotype that determine the progression of cancer, (3) estimating parameters of specific patient tumors early in treatment, 4) linking models with novel data collection methods that have single cell and spatial resolution. As our approaches advance, it is our hope that dynamical mathematical models of inter-cellular signaling can play a central role in identifying and testing new treatment strategies as well as forecasting impacts of disease treatment.

Cholesterol affects the binding of proteins to phosphatidic acid without influencing its ionization properties.

Phosphatidic acid (PA) through its unique negatively charged phosphate headgroup binds to various proteins to modulate multiple cellular events. To perform such diverse signaling functions, the ionization and charge of PA's headgroup relies on the properties of vicinal membrane lipids and changes in cellular conditions. Cholesterol has conspicuous effects on lipid properties and membrane dynamics. In eukaryotic cells, its concentration increases along the secretory pathway, reaching its highest levels towards the plasma membrane. Moreover, membrane cholesterol levels are altered in certain diseases such as Alzheimer's disease, cancer and in erythrocytes of hypercholesteremia patients. Hence, those changing levels of cholesterol could affect PA's charge and alter binding to effector protein. However, no study has investigated the direct impact of cholesterol on the ionization properties of PA. Here, we used 31P MAS NMR to explore the effects of increasing cholesterol concentrations on the chemical shifts and pKa2 of PA. We find that, while the chemical shifts of PA change significantly at high cholesterol concentrations, surprisingly, the pKa2 and charge of PA under these conditions are not modified. Furthermore, using in vitro lipid binding assays we found that higher cholesterol levels increased PA binding of the Spo20p PA sensor. Finally, in cellulo experiments demonstrated that depleting cholesterol from neurosecretory cells halts the recruitment of this sensor upon PA addition. Altogether, these data suggest that the intracellular cholesterol gradient may be an important regulator of proteins binding to PA and that a disruption of those levels in certain pathologies may also affect PA binding to its target proteins and subsequent signaling pathways.

No evidence of quantitative honest signaling in aposematic traits of the green and black dendrobatid frog Dendrobates auratus in Costa Rica

Abstract Aposematism is an antipredator strategy in which conspicuous coloration acts as a warning of chemical defenses to potential predators. Evidence suggests that aposematism largely functions under positive frequency-dependent selection, which is thought to maintain uniformity of aposematic signals. Many studies of aposematic organisms have found evidence that color signals and defenses are positively correlated, indicating a quantitatively honest aposematic signal. Dendrobatid poison frogs represent a well-studied group of aposematic organisms that in addition to exhibiting a diversity of color signals also display unique defensive behaviors. Few studies have examined if both behavior and coloration act as quantitative honest signals of alkaloid defenses in poison frogs. We aimed to determine if coloration and behavior are quantitatively honest signals in the green and black poison frog (Dendrobates auratus) among six populations from Costa Rica. We (1) evaluated antipredator displays by using behavioral assays in the field, (2) assessed frog conspicuousness and pattern using digital images, and (3) quantified alkaloid profiles from frog skin secretions. We found that Pacific populations are less conspicuous in coloration, had greater quantities of alkaloids, and more frequently performed body-raising defensive behaviors when compared to Caribbean populations. Our results do not support the hypothesis that aposematic traits in D. auratus are quantitatively honest. Rather, our results suggest that phenotypic differences among populations may represent different phenotypic optima for advertising unprofitability to predators based on local environmental conditions, leading to the diversification of aposematic signals in this species.