Intracellular Signal Transduction Research Articles

Unfolded protein response: An essential element of intestinal homeostasis and a potential therapeutic target for inflammatory bowel disease.

Different physiological and pathological situations can produce alterations in the cell's endoplasmic reticulum (ER), leading to a condition known as ER stress, which can trigger an intricate intracellular signal transduction system known as the unfolded protein response (UPR). UPR is primarily tailored to restore proteostasis and ER equilibrium; otherwise, if ER stress persists, it can cause programmed cell death as a cytoprotective mechanism and drive inflammatory processes. Therefore, since intestinal cells strongly rely on UPR for their biological functions and unbalanced UPR has been linked to inflammatory, metabolic, and immune disorders, here we discussed the role of the UPR within the intestinal tract, focusing on the UPR contribution to inflammatory bowel disease development. Importantly, we also highlighted the promising potential of UPR components as therapeutic targets for intestinal inflammatory diseases.

Cell-Instructive Biomaterials with Native-Like Biochemical Complexity.

Biochemical signals in native tissue microenvironments instruct cell behavior during many biological processes ranging from developmental morphogenesis and tissue regeneration to tumor metastasis and disease progression. The detection and characterization of these signals using spatial and highly resolved quantitative methods have revealed their existence as matricellular proteins in the matrisome, some of which are bound to the extracellular matrix while others are freely diffusing. Including these biochemical signals in engineered biomaterials can impart enhanced functionality and native-like complexity, ultimately benefiting efforts to understand, model, and treat various diseases. In this review, we discuss advances in characterizing, mimicking, and harnessing biochemical signals in developing advanced engineered biomaterials. An overview of the diverse forms in which these biochemical signals exist and their effects on intracellular signal transduction is also provided. Finally, we highlight the application of biochemically complex biomaterials in the three broadly defined areas of tissue regeneration, immunoengineering, and organoid morphogenesis.

IL-21 signaling promotes IgM+ B cell proliferation and antibody production via JAK/STAT3 and AKT pathways in early vertebrates.

IL-21 is a type I cytokine that is produced by activated CD4+ T cells and has a significant impact on the growth, survival, and functional activation of B lymphocytes. While IL-21 has been identified in several teleost fish species, its function and associated mechanisms focus on teleost fish B cells remain largely unknown. In this study, we aimed to investigate the effects of IL-21 (OnIL-21) on IgM+ B cells from Nile tilapia (Oreochromis niloticus), as well as the intracellular signaling transduction pathway involved. Through intraperitoneal injection of recombinant OnIL-21 (rOnIL-21), we observed that IL-21 exerted significant effects on Nile tilapia IgM+ B cells, including the promotion of IgM+ B cell proliferation, induction of IgM secretion, and up-regulation of inflammatory cytokines. These findings suggest that OnIL-21 enhances the ability of IgM+ B cells in humoral immunity. Furthermore, when IgM+ B cells were stimulated with rOnIL-21 in vitro, we observed a significant up-regulation in antibody secretion ability (sIgM), as well as increased expression of IFN-γ and IL-10. To further understand the regulatory mechanism of OnIL-21, we demonstrated that OnIL-21 binds to its heterodimer receptor complex (OnIL-21R/Onγc) to exert its function. This binding triggers the conserved JAK/STAT3 and AKT pathways, which in turn regulate the expression of genes involved in B cell proliferation, antibody secretion, and cytokine expression. Collectively, our findings establish that IL-21 plays a crucial role in the regulation of humoral immunity in lower vertebrates, and this regulation is mediated through conserved signaling pathways across vertebrates.

Synergistic Anticancer Strategy Targeting ECM Stiffness: Integration of Matrix Softening and Mechanical Signal Transduction Blockade in Primary Liver Cancers.

The development of primary liver cancer (hepatocellular carcinoma [HCC] and intrahepatic cholangiocarcinoma [ICC]) is linked to its physical microenvironment, particularly extracellular matrix (ECM) stiffness. Potential anticancer strategies targeting ECM stiffness include prevention/reversal of the stiffening process and disruption of the response of cancer cells to mechanical signals from ECM. However, each strategy has limitations. Therefore, the authors propose integrating them to maximize their strengths. Compared with HCC, ICC has a stiffer ECM and a worse prognosis. Therefore, ICC is selected to investigate mechanisms underlying the influence of ECM stiffness on cancer progression and application of the integrated anticancer strategy targeting ECM stiffness. In summary, immunofluorescence results for 181 primary liver cancer tissue chips (ICC, n=91; HCC, n=90) and analysis of TCGA mRNA-sequencing demonstrate that ECM stiffness can affect phenotypes of primary liver cancers. The YAP1/ABHD11-AS1/STAU2/ZYX/p-YAP1 pathway is a useful entry point for exploration of specific mechanisms of mechanical signal conduction from the ECM in ICC cells and their impact on cancer progression. Moreover, a synergistic anticancer strategy targeting ECM stiffness (ICCM@NPs + siABHD11-AS1@BAPN) is constructed by integrating ECM softening and blocking intracellular mechanical signal transduction in ICC and can provide insights for the treatment of cancers characterized by stiff ECM.

Ionic control of small GTPase HRas using calmodulin.

HRas is a small GTPase that plays physiologically important roles in various intracellular signal transduction processes, such as cell growth and proliferation. The structure and action mechanisms of HRas have been well-characterized, leading to widespread its use as a molecular switch in bionanomachines. calmodulin, a calcium ion-binding protein, acts as an ion-binding molecular switch and activates the target enzymes. We previously demonstrated that the fusion protein of HRas (M13-HRas) with the calmodulin target peptide M13 at the N-terminus of HRas exhibits reversible regulation of GTPase activity and the interaction between M13-HRas and the downstream signaling factor Raf by calcium ions with calmodulin. In this study, we prepared two new HRas fusion proteins with the M13 peptide at the C-terminus (HRas-M13) and both termini (M13-HRas-M13) of HRas and analyzed the calcium-dependent regulation of HRas function. M13-HRas-M13 more efficiently controlled GTPase, interaction with Raf, and the HRas regulator GEF by calcium ions with calmodulin.

Regulation of Vascular Injury and Repair by P21-Activated Kinase 1 and P21-Activated Kinase 2: Therapeutic Potential and Challenges.

The PAK (p21-activated kinases) family is a class of intracellular signal transduction protein kinases that regulate various cellular functions, mainly through their interactions with small GTP enzymes. PAK1 and PAK2 in the PAK kinase family are key signal transduction molecules that play important roles in various biological processes, including morphological changes, migration, proliferation, and apoptosis, and are involved in the progression of many diseases. Abnormal expression or dysregulation of PAK1 and PAK2 may be associated with several diseases, including cancer, neurological diseases, etc. The current research mainly focuses on studying the role of PAK and PAK inhibitors in the regulation of cancer progression, but relatively few reports are available that explore their potential role in cardiovascular diseases. Vascular injury and repair are complex processes involved in many cardiovascular conditions, including atherosclerosis, restenosis, and hypertension. Emerging research suggests that PAK1 and PAK2 have pivotal roles in vascular endothelial cell functions, including migration, proliferation, and angiogenesis. These kinases also modulate vascular smooth muscle relaxation, vascular permeability, and structural alterations, which are critical in the development of atherosclerosis and vascular inflammation. By targeting these activities, PAK proteins are essential for both normal vascular physiology and the pathogenesis of vascular diseases, highlighting their potential as therapeutic targets for vascular health. This review focuses on recent studies that offer experimental insights into the mechanisms by which PAK1 and PAK2 regulate the biological processes of vascular injury and repair and the therapeutic potential of the current existing PAK inhibitors in vascular-related diseases. The limitations of treatment with some PAK inhibitors and the ways that future development can overcome these challenges are also discussed.

High Extracellular K+ Skews T-Cell Differentiation Towards Tumour Promoting Th2 and Treg Subsets.

Potassium ions (K+) released from dying necrotic tumour cells accumulate in the tumour microenvironment (TME) and increase the local K+ concentration to 50mM (high-[K+]e). Here, we demonstrate that high-[K+]e decreases expression of the T-cell receptor subunits CD3ε and CD3ζ and co-stimulatory receptor CD28 and thereby dysregulates intracellular signal transduction cascades. High-[K+]e also alters the metabolic profiles of T-cells, limiting the metabolism of glucose and glutamine, consistent with functional exhaustion. These changes skew T-cell differentiation, favouring Th2 and iTreg subsets that promote tumour growth while restricting antitumour Th1 and Th17 subsets. Similar phenotypes were noted in T-cells present within the necrosis-prone core versus the outer zones of hepatocellular carcinoma (HCC)/colorectal carcinoma (CRC) tumours as analysed by GeoMx digital spatial profiling and flow-cytometry. Our results thus expand the understanding of the contribution of high-[K+]e to the immunosuppressive milieu in the TME.

Metabolism: a potential regulator of neutrophil fate.

Neutrophils are essential components of the innate immune system that defend against the invading pathogens, such as bacteria, viruses, and fungi, as well as having regulatory roles in various conditions, including tissue repair, cancer immunity, and inflammation modulation. The function of neutrophils is strongly related to their mode of cell death, as different types of cell death involve various cellular and molecular alterations. Apoptosis, a non-inflammatory and programmed type of cell death, is the most common in neutrophils, while other modes of cell death, including NETOsis, necrosis, necroptosis, autophagy, pyroptosis, and ferroptosis, have specific roles in neutrophil function regulation. Immunometabolism refers to energy and substance metabolism in immune cells, and profoundly influences immune cell fate and immune system function. Intercellular and intracellular signal transduction modulate neutrophil metabolism, which can, in turn, alter their activities by influencing various cell signaling pathways. In this review, we compile an extensive body of evidence demonstrating the role of neutrophil metabolism in their various forms of cell death. The review highlights the intricate metabolic characteristics of neutrophils and their interplay with various types of cell death.

In the Brain of Phosphodiesterases: Potential Therapeutic Targets for Schizophrenia.

Intracellular cyclic nucleotides (cyclic adenosine monophosphate and cyclic guanosine monophosphate) and downstream cellular signal transduction are regulated by phosphodiesterases (PDEs). The neuroplasticity, neurotransmitter pathways, and neuroinflammation-controlling functions of PDEs were demonstrated in numerous in vitro and animal model studies. We comprehensively reviewed the literature regarding the expression of PDEs in various brain regions. Subsequently, articles regarding schizophrenia and PDEs were examined. The pathophysiological mechanisms of schizophrenia and PDEs in preclinical and clinical investigations are briefly reviewed. Particularly for those who do not respond to conventional antipsychotics, specific PDE inhibitors may offer innovative therapeutic alternatives. Although the connection between schizophrenia and PDEs is intriguing, additional research is required. Comprehending the brain's PDE isoforms, their therapeutic potential, and any adverse effects of inhibiting them is essential for progress in this field.

Identification of the P24 Gene Family Related to Vesicular Transport in Cyclocarya paliurus and Their Expression Analysis Under Salt Stress

Vesicle transport is a fundamental mechanism for intracellular substance transfer and signal transduction, involving the formation, transport, fusion with target membranes, and release of vesicle contents within cells. Issues such as disruption of water balance, difficulty in regulating osmotic pressure, and oxidative stress caused by salt stress can lead to disturbances in the secretion system of plants, thus affecting plant growth and development. Cyclocarya paliurus (C. paliurus), widely used in traditional Chinese medicine, has not been previously reported in terms of how the vesicle transport P24 gene regulates its adaptation to salt stress. In this research project, a total of eight CpP24 genes were successfully identified. Upon examination of gene architecture and conserved sequence elements, the CpP24 genes exhibited a variation in exon count, ranging from 4 to 6. Moreover, the CpP24 gene family’s reaction to salt stress and specific stressors including methyl jasmonate (MeJA), sodium hydrosulfide (NaHS), and sodium nitroprusside (SNP) was further explored in our study. Comprehensive analysis of the expression patterns of CpP24 genes under various conditions showed that salt stress induced the expression of these genes, and the combined treatment of salt stress with specific stresses caused changes in their expression. This study lays a theoretical foundation for further probing into the physiological functions of C. paliurus and the underlying mechanisms regarding its response to environmental stress.

Progress in the mechanism of functional dyspepsia: roles of mitochondrial autophagy in duodenal abnormalities.

Mitochondria are the main source of energy for cellular activity. Their functional damage or deficiency leads to cellular deterioration, which in turn triggers autophagic reactions. Taking mitochondrial autophagy as a starting point, the present review explored the mechanisms of duodenal abnormalities in detail, including mucosal barrier damage, release of inflammatory factors, and disruption of intracellular signal transduction. We summarized the key roles of mitochondrial autophagy in the abnormal development of the duodenum and examined the in-depth physiological and pathological mechanisms involved, providing a comprehensive theoretical basis for understanding the pathogenesis of functional dyspepsia. At present, it has been confirmed that an increase in the eosinophil count and mast cell degranulation in the duodenum can trigger visceral hypersensitive reactions and cause gastrointestinal motility disorders. In the future, it is necessary to continue exploring the molecular mechanisms and signaling pathways of mitochondrial autophagy in duodenal abnormalities. A deeper understanding of mitochondrial autophagy provides important references for developing treatment strategies for functional dyspepsia, thereby improving clinical efficacy and patient quality of life.

Molecular mechanisms of hepatic lipid metabolism disorders: Focus on mitochondrial quality control

AbstractAlcohol‐associated liver disease (ALD) and nonalcoholic fatty liver disease (NAFLD) are the two predominant forms of chronic liver disease worldwide. Regardless of alcohol consumption, patients with NAFLD and ALD exhibit disturbances in lipid metabolism, progressing from simple steatosis to steatohepatitis, fibrosis, and ultimately cirrhosis. The precise mechanisms underlying the pathogenesis of NAFLD and ALD remain unclear. However, numerous studies have highlighted mitochondrial dysfunction as a hallmark of both diseases. Beyond their canonical metabolic function, mitochondria could influence hepatocytes through oxidative stress, intracellular signaling transduction, inflammation, and cell death, all of which are regulated by the mitochondrial quality control (MQC) system. Abnormalities in MQC, including defective mitophagy, erroneous mitochondrial dynamics, and delayed biogenesis, comprise mitochondrial morphological structure, function, and lifespan, resulting in hepatocyte damage. This review explores the involvement of MQC in the pathogenesis of NAFLD and ALD and identifies promising therapeutic targets aimed at enhancing MQC, potentially alleviating metabolic liver disease.

Biological Importance of Complex Sphingolipids and Their Structural Diversity in Budding Yeast Saccharomyces cerevisiae.

Complex sphingolipids are components of eukaryotic biomembranes and are involved in various physiological functions. In addition, their synthetic intermediates and metabolites, such as ceramide, sphingoid long-chain base, and sphingoid long-chain base 1-phosphate, play important roles as signaling molecules that regulate intracellular signal transduction systems. Complex sphingolipids have a large number of structural variations, and this structural diversity is considered an important molecular basis for their various physiological functions. The budding yeast Saccharomyces cerevisiae has simpler structural variations in complex sphingolipids compared to mammals and is, therefore, a useful model organism for elucidating the physiological significance of this structural diversity. In this review, we focus on the structure and function of complex sphingolipids in S. cerevisiae and summarize the response mechanisms of S. cerevisiae to metabolic abnormalities in complex sphingolipids.

DGKH-mediated phosphatidic acid oncometabolism as a driver of self-renewal and therapy resistance in HCC.

HCC is characterized by metabolic pathway aberrations, which enable cancer cells to meet their energy demands and accelerate malignant progression. Identifying novel metabolic players governing therapy resistance and self-renewal in HCC is crucial, as these properties are likely responsible for tumor recurrence. Clinical traits and RNA-seq of patients with HCC in The Cancer Genome Atlas were used for weighted gene coexpression network analysis, where 1 module was significantly correlated with advanced pathological stage and stem cell population maintenance. Further analysis of this module by integrating data obtained from HCC patient nonresponders to tyrosine kinase inhibitors identified 361 commonly deregulated genes. Intriguingly, these genes are significantly enriched in the intracellular signal transduction pathway, with diacylglycerol kinase eta (DGKH) ranked as the most enriched gene in poorly differentiated HCC tumors. Clinically, DGKH was elevated in tumor tissues compared to nontumor tissues. Patients with higher DGKH expression exhibited a more undifferentiated state and were less responsive to tyrosine kinase inhibitors. Functional assays using DGKH-manipulated HCC cell lines demonstrated that DGKH augmented aggressive features, including cancer stemness, therapy resistance, and metastasis. Upstream of DGKH , we discovered that the E1A-associated protein p300 (EP300) binds to DGKH's promoter region, thereby increasing its transcriptomic expression. Mechanistically, DGKH promotes mTOR signaling by producing phosphatidic acid. In an immunocompetent mouse model, cotreatment with sorafenib and liver-directed AAV8-mediated Dgkh depletion significantly reduced tumor burden, self-renewal, phosphatidic acid production, and mTOR signaling. Our research demonstrated that DGKH is a crucial oncometabolic regulator of cancer stemness and therapy resistance, suggesting that inhibiting DGKH may lead to more effective HCC treatment.

The molecular toll pathway repertoire in anopheline mosquitoes

Innate immunity in mosquitoes has received much attention due to its potential impact on vector competence for vector-borne disease pathogens, including malaria parasites. The nuclear factor (NF)-κB-dependent Toll pathway is a major regulator of innate immunity in insects. In mosquitoes, this pathway controls transcription of the majority of the known canonical humoral immune effectors, mediates anti-bacterial, anti-fungal and anti-viral immune responses, and contributes to malaria parasite killing. However, besides initial gene annotation of putative Toll pathway members and genetic analysis of the contribution of few key components to immunity, the molecular make-up and function of the Toll pathway in mosquitoes is largely unexplored. To facilitate functional analyses of the Toll pathway in mosquitoes, we report here manually annotated and refined gene models of Toll-like receptors and all putative components of the intracellular signal transduction cascade across 19 anopheline genomes, and in two culicine genomes. In addition, based on phylogenetic analyses, we identified differing levels of evolutionary constraint across the intracellular Toll pathway members, and identified a recent radiation of TOLL1/5 within the Anopheles gambiae complex. Together, this study provides insight into the evolution of TLRs and the putative members of the intracellular signal transduction cascade within the genus Anopheles.

NEUROTROPIC EFFECTS OF ENDOGENOUS COMPOUNDS – TYRONOME COMPONENTS IN THE CENTRAL NERVOUS SYSTEM

Background. During the last decades, data on potential cytoprotective effects of decarboxylated and deiodinated endogenous compounds – metabolites of thyroid hormones, constituting the thyronome, have been accumulated. The aim of this review is to systematize the biological effects of thyronome components in the central nervous system from the position of their possible role as potential neuroprotectants. Material and methods. English- and Russian-language full-text articles from PubMed, Mendeley, and e-library electronic databases were selected for analysis using query «(thyroid OR thyroid hormone metabolite OR *-iodo-thyronamine OR thyronamine OR TAAR OR thyronome OR T0AM OR T1AM OR thyroacetic acid) AND (brain OR central nervous system OR CNS OR stroke OR neurodegenerat*)». The search depth amounted to 10 years. Results. The review systematizes the most important neurotropic properties of 3-T1AM and other thyronome components, including their influence on behavioral effects, memory, pain threshold level, apoptosis, autophagy, and excitotoxic neuronal death, and describes the role of individual receptors and intracellular signal transduction pathways in the realization of these properties. Conclusion. The components of thyronome, in particular 3-T1AM, demonstrate a wide range of potential neuroprotective properties, and for its potential use in the clinic, it is relevant to find ways to increase local concentration in the brain or permeability to the BBB, as well as the development of more effective synthetic analogues.

Synthesis of a 13C/2H Labeled Building Block to Probe the Phosphotyrosine Interactome Using Biomolecular NMR Spectroscopy.

Phosphotyrosine (pTyr) recognition coordinates the assembly of protein complexes, thus controlling key events of cell cycle, cell development and programmed cell death. Although many aspects of membrane receptor function and intracellular signal transduction have been deciphered in the last decades, the details of how phosphorylation alters protein-protein interaction and creates regulating switches of protein activity and localization often remains unclear. We developed a synthetic route to a protected phophotyrosine building block with isolated 13C-1H spins in the aromatic ring. The compound can be used for solid phase peptide synthesis (SPPS) and readily applied to study affinity, dynamics and interactions on an atomic level using NMR spectroscopy. As a first example, we prepared an isotopologue of a pTyr containing 12mer peptide (pY1021) as part of the platelet-derived growth factor to analyze the binding to the phospholipase C-γ (PLCγ-1) SH2 domain.

Characterization of Ksg1 protein kinase-dependent phosphoproteome in the fission yeast S. pombe

Ksg1 is an essential protein kinase of the fission yeast S. pombe that belongs to the AGC kinase family and is homologous to the mammalian PDPK1 kinase. Previous studies have shown that Ksg1 functions in the nutrient-sensing TOR signaling pathway and is involved in the phosphorylation and activation of other AGC kinases, thereby affecting various downstream targets related to metabolism, cell division, stress response, and gene expression. To date, the molecular function of Ksg1 has been analyzed using its temperature sensitive mutants or mutants expressing its truncated isoforms, which are not always suitable for functional studies of Ksg1 and the identification of its targets. To overcome these limitations, we employed a chemical genetic strategy and used a conditional ksg1as mutant sensitive to an ATP analog. Combining this mutant with quantitative phosphoproteomics analysis, we identified 1986 phosphosites that were differentially phosphorylated when Ksg1as kinase was inhibited by an ATP analog. We found that proteins whose phosphorylation was dysregulated after inhibition of Ksg1as kinase were mainly represented by those involved in the regulation of cytokinesis, contractile ring contraction, cell division, septation initiation signaling cascade, intracellular protein kinase cascade, barrier septum formation, protein phosphorylation, intracellular signal transduction, cytoskeleton organization, cellular response to stimulus, or in RNA, ncRNA and rRNA processing. Importantly, proteins with significantly down-regulated phosphorylation were specifically enriched for R-X-X-S and R-X-R-X-X-S motifs, which are typical consensus substrate sequences for phosphorylation by the AGC family of kinases. The results of this study provide a basis for further analysis of the role of the Ksg1 kinase and its targets in S. pombe and may also be useful for studying Ksg1 orthologs in other organisms.

Extracellular bimolecular fluorescence complementation for investigating membrane protein dimerization: a proof of concept using class B GPCRs.

Bimolecular fluorescence complementation (BiFC) methodology uses split fluorescent proteins to detect interactions between proteins in living cells. To date, BiFC has been used to investigate receptor dimerization by splitting the fluorescent protein between the intracellular portions of different receptor components. We reasoned that attaching these split proteins to the extracellular N-terminus instead may improve the flexibility of this methodology and reduce the likelihood of impaired intracellular signal transduction. As a proof-of-concept, we used receptors for calcitonin gene-related peptide, which comprise heterodimers of either the calcitonin or calcitonin receptor-like receptor in complex with an accessory protein (receptor activity-modifying protein 1). We created fusion constructs in which split mVenus fragments were attached to either the C-termini or N-termini of receptor subunits. The resulting constructs were transfected into Cos7 and HEK293S cells, where we measured cAMP production in response to ligand stimulation, cell surface expression of receptor complexes, and BiFC fluorescence. Additionally, we investigated ligand-dependent internalization in HEK293S cells. We found N-terminal fusions were better tolerated with regards to cAMP signaling and receptor internalization. N-terminal fusions also allowed reconstitution of functional fluorescent mVenus proteins; however, fluorescence yields were lower than with C-terminal fusion. Our results suggest that BiFC methodologies can be applied to the receptor N-terminus, thereby increasing the flexibility of this approach, and enabling further insights into receptor dimerization.

Exosomal microRNA as a key regulator of PI3K/AKT pathways in human tumors.

MicroRNAs (miRNAs) are conserved non-protein-coding RNAs that are naturally present in organisms and can control gene expression by suppressing the translation of mRNA or causing the degradation of mRNA. MicroRNAs are highly concentrated in the PI3K/AKT pathway, and abnormal activation of the PI3K/AKT pathway plays a role in cancer progression. The AKT/PI3K pathway is critical for cellular functions and can be stimulated by cytokines and in normal situations. It is involved in regulating various intracellular signal transduction, including development, differentiation, transcriptional regulation, protein, and synthesis. There is a growing body of evidence indicating that miRNAs, which are abundant in exosomes released by different cells, can control cellular biological activities via modulating the PI3K/AKT pathway, hence influencing cancer progression and drug resistance. This article provides an overview of the latest research progress regarding the function and medical use of the PI3K/AKT pathway and exosomal miRNA/AKT/PI3K axis in the behaviors of cancer cells.