The Non-receptor Tyrosine Kinase Pyk2 in Brain Function and Neurological and Psychiatric Diseases

The PTK2B gene is associated with obesity, adiposity, and leptin levels in children and adolescents

Previous studies determined that Pyk2 is involved in several diseases in which the symptomatology presents alterations in energy balance. However, its role in obesity is poorly understood. To evaluate the metabolic role of the Pyk2 gene (PTK2B) in children and adolescents with obesity we measured its mRNA expression levels in peripheral blood mononuclear cells. For that we performed a cross-sectional study involving 130 Caucasian subjects that was divided into two groups according to BMI. Data showed increased PTK2B mRNA expression in children and adolescents with obesity. Interestingly, a positive correlation has been found between the levels of PTK2B with weight, BMI, BMI Z score, fat mass, waist circumference, waist to height ratio, diastolic blood pressure, and leptin. In addition, it is indicated that high levels of PTK2B gene expression might be a predictor of obesity development. This work provides important insights into the previously undescribed role of Pyk2 in obesity.

Cellular signaling pathways in the nervous system activated by various mechanical and electromagnetic stimuli

Mechanical stimuli, such as stretch, shear stress, or compression, activate a range of biomolecular responses through cellular mechanotransduction. In the nervous system, studies on mechanical stress have highlighted key pathophysiological mechanisms underlying traumatic injury and neurodegenerative diseases. However, the biomolecular pathways triggered by mechanical stimuli in the nervous system has not been fully explored, especially compared to other body systems. This gap in knowledge may be due to the wide variety of methods and definitions used in research. Additionally, as mechanical stimulation techniques such as ultrasound and electromagnetic stimulation are increasingly utilized in psychological and neurorehabilitation treatments, it is vital to understand the underlying biological mechanisms in order to develop accurate pathophysiological models and enhance therapeutic interventions. This review aims to summarize the cellular signaling pathways activated by various mechanical and electromagnetic stimuli with a particular focus on the mammalian nervous system. Furthermore, we briefly discuss potential cellular mechanosensors involved in these processes.

Coupling of Alzheimer's Disease Genetic Risk Factors with Viral Susceptibility and Inflammation

Alzheimer's disease (AD) is a neurodegenerative disease characterized by persistent cognitive decline. Amyloid plaque deposition and neurofibrillary tangles are the main pathological features of AD brain, though mechanisms leading to the formation of lesions remain to be understood. Genetic efforts through genome-wide association studies (GWAS) have identified dozens of risk genes influencing the pathogenesis and progression of AD, some of which have been revealed in close association with increased viral susceptibilities and abnormal inflammatory responses in AD patients. In the present study, we try to present a list of AD candidate genes that have been shown to affect viral infection and inflammatory responses. Understanding of how AD susceptibility genes interact with the viral life cycle and potential inflammatory pathways would provide possible therapeutic targets for both AD and infectious diseases.

Targeting PYK2 with heterobifunctional T6BP helps mitigate MASLD and MASH-HCC progression

BACKGROUND & AIMS

The mechanisms underlying the regulation of hepatocyte non-receptor tyrosine kinases in metabolic dysfunction-associated steatohepatitis (MASH) remain largely unclear.

METHODS

Hepatocyte-specific overexpression or deletion and anti-protein tyrosine kinase 2 beta (PYK2) or anti-TRAF6-binding protein (T6BP) crosslinking were utilised to study fatty liver protection by T6BP. P-PTC, a peptide-proteolysis targeting chimaera, degrades PYK2 to block MASH progression.

RESULTS

Since PYK2 activation is promoter signalling in steatohepatitis development, we find that T6BP is a novel and critical suppressor of PYK2 that reduces hepatic lipid accumulation, pro-inflammatory factor release, and pro-fibrosis production by ubiquitin ligase CBL to degrade PYK2. Mechanistic evidence suggests that T6BP directly targets PYK2 and prevents its N-terminal FERM domain-triggered dimerization, disrupting downstream PYK2-JNK signalling hyperactivation. Additionally, T6BP favourably recruits CBL, a particular E3 ubiquitin ligase targeting PYK2, to form a complex and degrade PYK2. T6BP (F1), a core fragment of T6BP, directly blocks N-terminal FERM domain-associated dimerization of PYK2, followed by T6BP-recruiting CBL-mediated PYK2 degradation in a typical T6BP-dependent manner when the tiny fragment is specifically expressed using thyroxine binding globulin (TBG)-ground vectors. This inhibits the progression of MASH, metabolic dysfunction-associated steatotic liver disease (MASLD)-related HCC (MASH-HCC), and metabolic syndrome in dietary rodent models. First-ever peptide-proteolysis targeting chimaera (P-PTC) based on the core segment of T6BP as a ligand for targeted recruitment of CBL targeting metabolic disorders like MASH has been devised and validated in animal models.

CONCLUSIONS

Our study revealed a previously unknown mechanism: identification of T6BP as a key eliminator of fatty liver strongly contributes to the development of promising therapeutic targets, and the discovery of crucial fragments of T6BP-based pharmacon that interrupt PYK2 dimerization are novel and viable treatments for fatty liver and its advanced symptoms and complications.

IMPACT AND IMPLICATIONS

Excessive high-energy diet ingestion is critical in driving steatohepatitis via regulation of hepatocyte non-receptor tyrosine kinases. The mechanisms under lying the regulation of hepatocyte PYK2 in metabolic dysfunction-associated steatohepatitis (MASH) remain largely unclear. Here, we found that T6BP as a critical fatty liver eliminator has a significant impact on the development of promising therapeutic targets. Additionally, vital T6BP-based pharmacon fragments that impede PYK2 dimerization have been found, offering new and effective treatments for advanced fatty liver symptoms and complications.

Autocrine VEGF drives neural stem cell proximity to the adult hippocampus vascular niche

The vasculature is a key component of adult brain neural stem cell (NSC) niches. In the adult mammalian hippocampus, NSCs reside in close contact with a dense capillary network. How this niche is maintained is unclear. We recently found that adult hippocampal NSCs express VEGF, a soluble factor with chemoattractive properties for vascular endothelia. Here, we show that global and NSC-specific VEGF loss led to dissociation of NSCs and their intermediate progenitor daughter cells from local vasculature. Surprisingly, though, we found no changes in local vascular density. Instead, we found that NSC-derived VEGF supports maintenance of gene expression programs in NSCs and their progeny related to cell migration and adhesion. In vitro assays revealed that blockade of VEGF receptor 2 impaired NSC motility and adhesion. Our findings suggest that NSCs maintain their own proximity to vasculature via self-stimulated VEGF signaling that supports their motility towards and/or adhesion to local blood vessels.

The Role of Necroptosis in Cerebral Ischemic Stroke

Cerebral ischemia, also known as ischemic stroke, accounts for nearly 85% of all strokes and is the leading cause of disability worldwide. Due to disrupted blood supply to the brain, cerebral ischemic injury is trigged by a series of complex pathophysiological events including excitotoxicity, oxidative stress, inflammation, and cell death. Currently, there are few treatments for cerebral ischemia owing to an incomplete understanding of the molecular and cellular mechanisms. Accumulated evidence indicates that various types of programmed cell death contribute to cerebral ischemic injury, including apoptosis, ferroptosis, pyroptosis and necroptosis. Among these, necroptosis is morphologically similar to necrosis and is mediated by receptor-interacting serine/threonine protein kinase-1 and -3 and mixed lineage kinase domain-like protein. Necroptosis inhibitors have been shown to exert inhibitory effects on cerebral ischemic injury and neuroinflammation. In this review, we will discuss the current research progress regarding necroptosis in cerebral ischemia as well as the application of necroptosis inhibitors for potential therapeutic intervention in ischemic stroke.

Comprehensive Overview of Alzheimer's Disease: Etiological Insights and Degradation Strategies

Alzheimer's disease (AD) is the most prevalent neurodegenerative disorder and affects millions of individuals globally. AD is associated with cognitive decline and memory loss that worsens with aging. A statistical report using U.S. data on AD estimates that approximately 6.9 million individuals suffer from AD, a number projected to surge to 13.8 million by 2060. Thus, there is a critical imperative to pinpoint and address AD and its hallmark tau protein aggregation early to prevent and manage its debilitating effects. Amyloid-β and tau proteins are primarily associated with the formation of plaques and neurofibril tangles in the brain. Current research efforts focus on degrading amyloid-β and tau or inhibiting their synthesis, particularly targeting APP processing and tau hyperphosphorylation, aiming to develop effective clinical interventions. However, navigating this intricate landscape requires ongoing studies and clinical trials to develop treatments that truly make a difference. Genome-wide association studies (GWASs) across various cohorts identified 40 loci and over 300 genes associated with AD. Despite this wealth of genetic data, much remains to be understood about the functions of these genes and their role in the disease process, prompting continued investigation. By delving deeper into these genetic associations, novel targets such as kinases, proteases, cytokines, and degradation pathways, offer new directions for drug discovery and therapeutic intervention in AD. This review delves into the intricate biological pathways disrupted in AD and identifies how genetic variations within these pathways could serve as potential targets for drug discovery and treatment strategies. Through a comprehensive understanding of the molecular underpinnings of AD, researchers aim to pave the way for more effective therapies that can alleviate the burden of this devastating disease.

Unveiling Immune-related feature genes for Alzheimer's disease based on machine learning

The identification of diagnostic and therapeutic biomarkers for Alzheimer's Disease (AD) remains a crucial area of research. In this study, utilizing the Weighted Gene Co-expression Network Analysis (WGCNA) algorithm, we identified RHBDF2 and TNFRSF10B as feature genes associated with AD pathogenesis. Analyzing data from the GSE33000 dataset, we revealed significant upregulation of RHBDF2 and TNFRSF10B in AD patients, with correlations to age and gender. Interestingly, their expression profile in AD differs notably from that of other neurodegenerative conditions. Functional analysis unveiled their involvement in immune response and various signaling pathways implicated in AD pathogenesis. Furthermore, our study demonstrated the potential of RHBDF2 and TNFRSF10B as diagnostic biomarkers, exhibiting high discrimination power in distinguishing AD from control samples. External validation across multiple datasets confirmed the robustness of the diagnostic model. Moreover, utilizing molecular docking analysis, we identified dinaciclib and tanespimycin as promising small molecule drugs targeting RHBDF2 and TNFRSF10B for potential AD treatment. Our findings highlight the diagnostic and therapeutic potential of RHBDF2 and TNFRSF10B in AD management, shedding light on novel strategies for precision medicine in AD.

Molecularly imprinted nanoparticles reveal regulatory scaffolding features in Pyk2 tyrosine kinase

Pyk2 is a multi-domain non-receptor tyrosine kinase that serves dual roles as a signaling enzyme and scaffold. Pyk2 activation involves a multi-stage cascade of conformational rearrangements and protein interactions initiated by autophosphorylation of a linker site. Linker phosphorylation recruits Src kinase, and Src-mediated phosphorylation of the Pyk2 activation loop confers full activation. The regulation and accessibility of the initial Pyk2 autophosphorylation site remains unclear. We employed peptide-binding molecularly imprinted nanoparticles (MINPs) to probe the regulatory conformations controlling Pyk2 activation. MINPs differentiating local structure and phosphorylation state revealed that the Pyk2 autophosphorylation site is protected in the autoinhibited state. Activity profiling of Pyk2 variants implicated FERM and linker residues responsible for constraining the autophosphorylation site. MINPs targeting each Src docking site disrupt the higher-order kinase interactions critical for activation complex maturation. Ultimately, MINPs targeting key regulatory motifs establish a useful toolkit for probing successive activational stages in the higher-order Pyk2 signaling complex.

Hippocampal Pyk2 regulates specific social skills: Implications for schizophrenia

Pyk2 has been shown previously to be involved in several psychological and cognitive alterations related to stress, Huntington's disease, and Alzheimer's disease. All these disorders are accompanied by different types of impairments in sociability, which has recently been linked to improper mitochondrial function. We hypothesize that Pyk2, which regulates mitochondria, could be associated with the regulation of mitochondrial dynamics and social skills. In the present manuscript, we report that a reduction of Pyk2 levels in mouse pyramidal neurons of the hippocampus decreased social dominance and aggressivity. Furthermore, social interactions induced robust Pyk2-dependent hippocampal changes in several oxidative phosphorylation complexes. We also observed that Pyk2 levels were increased in the CA1 pyramidal neurons of schizophrenic subjects, occurring alongside changes in different direct and indirect regulators of mitochondrial function including DISC1 and Grp75. Accordingly, overexpressing Pyk2 in hippocampal CA1 pyramidal cells mimicked some specific schizophrenia-like social behaviors in mice. In summary, our results indicate that Pyk2 might play a role in regulating specific social skills likely via mitochondrial dynamics and that there might be a link between Pyk2 levels in hippocampal neurons and social disturbances in schizophrenia.

PYK2, a hub of signaling networks in breast cancer progression

Breast cancer (BC) involves complex signaling networks characterized by extensive cross-communication and feedback loops between and within multiple signaling cascades. Many of these signaling pathways are driven by genetic alterations of oncogene and/or tumor-suppressor genes and are influenced by various environmental cues. We describe unique roles of the non-receptor tyrosine kinase (NRTK) PYK2 in signaling integration and feedback looping in BC. PYK2 functions as a signaling hub in various cascades, and its involvement in positive and negative feedback loops enhances signaling robustness, modulates signaling dynamics, and contributes to BC growth, epithelial-to-mesenchymal transition (EMT), stemness, migration, invasion, and metastasis. We also discuss the potential of PYK2 as a therapeutic target in various BC subtypes.

Lipids regulate peripheral serotonin release via gut CD1d

The crosstalk between the immune and neuroendocrine systems is critical for intestinal homeostasis and gut-brain communications. However, it remains unclear how immune cells participate in gut sensation of hormones and neurotransmitters release in response to environmental cues, such as self-lipids and microbial lipids. We show here that lipid-mediated engagement of invariant natural killer T (iNKT) cells with enterochromaffin (EC) cells, a subset of intestinal epithelial cells, promoted peripheral serotonin (5-HT) release via a CD1d-dependent manner, regulating gut motility and hemostasis. We also demonstrated that inhibitory sphingolipids from symbiotic microbe Bacteroides fragilis represses 5-HT release. Mechanistically, CD1d ligation on EC cells transduced a signal and restrained potassium conductance through activation of protein tyrosine kinase Pyk2, leading to calcium influx and 5-HT secretion. Together, our data reveal that by engaging with iNKT cells, gut chemosensory cells selectively perceive lipid antigens via CD1d to control 5-HT release, modulating intestinal and systemic homeostasis.

Clutching at Guidance Cues: The Integrin-FAK Axis Steers Axon Outgrowth

Integrin receptors are essential contributors to neurite outgrowth and axon elongation. Activated integrins engage components of the extracellular matrix, enabling the growth cone to form point contacts, which connect the extracellular substrate to dynamic intracellular protein complexes. These adhesion complexes facilitate efficient growth cone migration and neurite extension. Major signalling pathways mediated by the adhesion complex are instigated by focal adhesion kinase (FAK), whilst axonal guidance molecules present in vivo promote growth cone turning or retraction by local modulation of FAK activity. Activation of FAK is marked by phosphorylation following integrin engagement, and this activity is tightly regulated during neurite outgrowth. FAK inhibition slows neurite outgrowth by reducing point contact turnover; however, mutant FAK constructs with enhanced activity stimulate aberrant outgrowth. Importantly, FAK is a major structural component of maturing adhesion sites, which provide the platform for actin polymerisation to drive leading edge advance. In this review, we discuss the coordinated signalling of integrin receptors and FAK, as well as their role in regulating neurite outgrowth and axon elongation. We also discuss the importance of the integrin-FAK axis in vivo, as integrin expression and activation are key determinants of successful axon regeneration following injury.

Metamodulation of presynaptic NMDA receptors: New perspectives for pharmacological interventions

Metamodulation shifted the scenario of the central neuromodulation from a simplified unimodal model to a multimodal one. It involves different receptors/membrane proteins physically associated or merely colocalized that act in concert to control the neuronal functions influencing each other. Defects or maladaptation of metamodulation would subserve neuropsychiatric disorders or even synaptic adaptations relevant to drug dependence. Therefore, this "vulnerability" represents a main issue to be deeply analyzed to predict its aetiopathogenesis, but also to propose targeted pharmaceutical interventions. The review focusses on presynaptic release-regulating NMDA receptors and on some of the mechanisms of their metamodulation described in the literature. Attention is paid to the interactors, including both ionotropic and metabotropic receptors, transporters and intracellular proteins, which metamodulate their responsiveness in physiological conditions but also undergo adaptation that are relevant to neurological dysfunctions. All these structures are attracting more and more the interest as promising druggable targets for the treatment of NMDAR-related central diseases: these substances would not exert on-off control of the colocalized NMDA receptors (as usually observed with NMDAR full agonists/antagonists), but rather modulate their functions, with the promise of limiting side effects that would favor their translation from preclinic to clinic.

The role of genetic risk factors of Alzheimer's disease in synaptic dysfunction

Alzheimer's disease (AD) is a neurodegenerative disease characterized by the progressive deterioration of cognitive functions. Due to the extended global life expectancy, the prevalence of AD is increasing among aging populations worldwide. While AD is a multifactorial disease, synaptic dysfunction is one of the major neuropathological changes that occur early in AD, before clinical symptoms appear, and is associated with the progression of cognitive deterioration. However, the underlying pathological mechanisms leading to this synaptic dysfunction remains unclear. Recent large-scale genomic analyses have identified more than 40 genetic risk factors that are associated with AD. In this review, we discuss the functional roles of these genes in synaptogenesis and synaptic functions under physiological conditions, and how their functions are dysregulated in AD. This will provide insights into the contributions of these encoded proteins to synaptic dysfunction during AD pathogenesis.

Wide-spread enhancer effect of SNP rs2279590 on regulating epoxide hydrolase-2 and protein tyrosine kinase 2-beta gene expression

Polymorphisms in the PTK2B-CLU locus have been associated with various neurodegenerative disorders including pseudoexfoliation glaucoma, Alzheimer's and Parkinson's. Many of these genomic variants are within enhancer elements and modulate genes associated with the disease pathogenesis. However, mechanisms by which they control the gene expression is unknown. Previously, we have shown that clusterin enhancer element surrounding rs2279590 intronic variant, a risk factor in the pathogenesis of pseudoexfoliation glaucoma modulates gene expression of clusterin (CLU), protein tyrosine kinase 2 beta (PTK2B) and epoxide hydrolase 2 (EPHX2). Here, we explored the mechanism by which rs2279590 enhancer regulates their gene expression through chromosome conformation capture assays. 3C assays revealed a strong enhancer-promoter chromatin interaction between rs2279590 enhancer and promoters of genes CLU, PTK2B and EPHX2 in the HEK293 wild type cells. Moreover, genomic knockout of rs2279590 element significantly decreases the chromatin-chromatin cross-linking frequency suggesting gene regulation at transcriptional level through formation of chromatin loop. In addition, molecular assays showed a significantly decreased expression of EPHX2 but not PTK2B at both mRNA and protein level in the lens capsule of pseudoexfoliation affected patients in comparison to control subjects implying a role of EPHX2 in the pathogenesis of pseudoexfoliation.

Molecular and Cellular Crosstalk between Bone and Brain: Accessing Bidirectional Neural and Musculoskeletal Signaling during Aging and Disease

Molecular omics technologies, including proteomics, have enabled the elucidation of key signaling pathways that mediate bidirectional communication between the brain and bone tissues. Here we provide a brief summary of the clinical and molecular evidence of the need to study the bone-brain axis of cross-tissue cellular communication. Clear clinical and molecular evidence suggests biological interactions and similarities between bone and brain cells. Here we review the current mass spectrometric techniques for studying brain and bone diseases with an emphasis on neurodegenerative diseases and osteoarthritis/osteoporosis, respectively. Further study of the bone-brain axis on a molecular level and evaluation of the role of proteins, neuropeptides, osteokines, and hormones in molecular pathways linked to bone and brain diseases is critically needed. The use of mass spectrometry and other omics technologies to analyze these cross-tissue signaling events and interactions will help us better understand disease progression and comorbidities and potentially identify new pathways and targets for therapeutic interventions. Proteomic measurements are particularly favorable for investigating the role of signaling and secreted and circulating analytes and identifying molecular and metabolic pathways implicated in age-related diseases.

Microglia PTK2B/Pyk2 in the Pathogenesis of Alzheimer's Disease

Alzheimer's disease (AD) is a highly hereditary disease with complex genetic susceptibility factors. Extensive genome-wide association studies have established a distinct susceptibility link between the protein tyrosine kinase 2β (PTK2B) gene and late-onset Alzheimer's disease (LOAD), but the specific pathogenic mechanisms remain incompletely understood. PTK2B is known to be expressed in neurons, and recent research has revealed its more important significance in microglia. Elucidating the role of PTK2B high expression in microglia in AD's progression is crucial for uncovering novel pathogenic mechanisms of the disease. Our review of existing studies suggests a close relationship between PTK2B/proline-rich tyrosine kinase 2 (Pyk2) and tau pathology, and this process might be β-amyloid (Aβ) dependence. Pyk2 is hypothesized as a pivotal target linking Aβ and tau pathologies. Concurrently, Aβ-activated Pyk2 participates in the regulation of microglial activation and its proinflammatory functions. Consequently, it is reasonable to presume that Pyk2 in microglia contributes to amyloid-induced tau pathology in AD via a neuroinflammatory pathway. Furthermore, many things remain unclear, such as identifying the specific pathways that lead to the release of downstream inflammatory factors due to Pyk2 phosphorylation and whether all types of inflammatory factors can activate neuronal kinase pathways. Additionally, further in vivo experiments are essential to validate this hypothesized pathway. Considering PTK2B/Pyk2's potential role in AD pathogenesis, targeting this pathway may offer innovative and promising therapeutic approaches for AD.

Insight into Glyproline Peptides' Activity through the Modulation of the Inflammatory and Neurosignaling Genetic Response Following Cerebral Ischemia-Reperfusion

Glyprolines are Gly-Pro (GP)- or Pro-Gly (PG)-containing biogenic peptides. These peptides can act as neutrophil chemoattractants, or atheroprotective, anticoagulant, and neuroprotective agents. The Pro-Gly-Pro (PGP) tripeptide is an active factor of resistance to the biodegradation of peptide drugs. The synthetic Semax peptide, which includes Met-Glu-His-Phe (MEHF) fragments of adrenocorticotropic hormone and the C-terminal tripeptide PGP, serves as a neuroprotective drug for the treatment of ischemic stroke. Previously, we revealed that Semax mostly prevented the disruption of the gene expression pattern 24 h after a transient middle cerebral artery occlusion (tMCAO) in a rat brain model. The genes of this pattern were grouped into an inflammatory cluster (IC) and a neurotransmitter cluster (NC). Here, using real-time RT-PCR, the effect of other PGP-containing peptides, PGP and Pro-Gly-Pro-Leu (PGPL), on the expression of a number of genes in the IC and NC was studied 24 h after tMCAO. Both the PGP and PGPL peptides showed Semax-unlike effects, predominantly without changing gene expression 24 h after tMCAO. Moreover, there were IC genes (iL1b, iL6, and Socs3) for PGP, as well as IC (iL6, Ccl3, Socs3, and Fos) and NC genes (Cplx2, Neurod6, and Ptk2b) for PGPL, that significantly changed in expression levels after peptide administration compared to Semax treatment under tMCAO conditions. Furthermore, gene enrichment analysis was carried out, and a regulatory gene network was constructed. Thus, the spectra of the common and unique effects of the PGP, PGPL, and Semax peptides under ischemia-reperfusion were distinguished.

Spatially resolved gene regulatory and disease-related vulnerability map of the adult Macaque cortex

Single cell approaches have increased our knowledge about the cell type composition of the non-human primate (NHP), but a detailed characterization of area-specific regulatory features remains outstanding. We generated single-cell transcriptomic and chromatin accessibility (single-cell ATAC) data of 358,237 cells from prefrontal cortex (PFC), primary motor cortex (M1) and primary visual cortex (V1) of adult female cynomolgus monkey brain, and integrated this dataset with Stereo-seq (spatial enhanced resolution omics-sequencing) of the corresponding cortical areas to assign topographic information to molecular states. We identified area-specific chromatin accessible sites and their targeted genes, including the cell type-specific transcriptional regulatory network associated with excitatory neurons heterogeneity. We reveal calcium ion transport and axon guidance genes related to specialized functions of PFC and M1, identified the similarities and differences between adult macaque and human oligodendrocyte trajectories, and mapped the genetic variants and gene perturbations of human diseases to NHP cortical cells. This resource establishes a transcriptomic and chromatin accessibility combinatory regulatory landscape at a single-cell and spatially resolved resolution in NHP cortex.

Deciphering the Heterogeneity of the Internal Environment of Hippocampal Neurons during Maturation by Raman Spectroscopy

Hippocampal neurons are sensitive to changes in the internal environment and play a significant role in controlling learning, memory, and emotions. A remarkable characteristic of the aging brain is its ability to shift from a state of normal inflammation to excessive inflammation. Various cognitive abilities of the elderly may suffer from serious harm due to the change in the neural environment. Hippocampal neurons may have various subsets involved in controlling their internal environment at different stages of development. Developmental differences may eventually result from complex changes in the dynamic neuronal system brought on by metabolic changes. In this study, we used an in vitro hippocampal neuron model cultured in C57BL/6J mice in conjugation with Raman spectroscopy to examine the relative alterations in potential biomarkers, such as levels of metabolites in the internal environment of hippocampal neurons at various developmental stages. The various differentially expressed genes (DEGs) of hippocampal neurons at various developmental stages were simultaneously screened using bioinformatics, and the biological functions as well as the various regulatory pathways of DEGs were preliminarily analyzed, providing an essential reference for investigating novel therapeutic approaches for diseases that cause cognitive impairment, such as Alzheimer's disease. A stable hippocampal neuron model was established using the GIBCO C57BL/6J hippocampal neuron cell line as a donor and in vitro hippocampal neuron culture technology. The Raman peak intensities of culture supernatants from the experimental groups incubated for 0, 7, and 14 days in vitro(DIV) were examined. The GEO database was used to screen for different DEGs associated with various developmental stages. The data was then analyzed using a statistical method called orthogonal partial least squares discriminant analysis (OPLS-DA). The levels of ketogenic and glycogenic amino acids (such as tryptophan, phenylalanine, and tyrosine), lipid intake rate, glucose utilization rate, and nucleic acid expression in the internal environment of hippocampal neurons were significantly different in the 14 DIV group compared to the 0 DIV and 7 DIV groups (P < 0.01). The top 10 DEGs with neuronal maturation were screened, and the results were compared to the OPLS-DA model's analysis of the differential peaks. It was found that different genes involved in maturation can directly relate to changes in the body's levels of ketogenic and glycogenic amino acids (P < 0.01). The altered expression of the maturation-related genes epidermal growth factor receptor, protein tyrosine kinase 2-beta, discs large MAGUK scaffold protein 2, and Ras protein-specific guanine nucleotide releasing factor 1 may be connected to the altered uptake of ketogenic and glycogenic amino acids and nucleic acids in the internal environment of neurons at different developmental stages. The levels of ketogenic, glycogenic amino acids, and lipid intake increased while glucose utilization decreased, which may be related to mature neurons' metabolism and energy use. The decline in nucleic acid consumption could be connected to synaptic failure. The Raman spectroscopy fingerprint results of relevant biomarkers in conjugation with multivariable analysis and biological action targets suggested by differential genes interpret the heterogeneity of the internal environment of mature hippocampal neurons in the process of maturation, open a new idea for exploring the dynamic mechanism of the exchange energy metabolism of information molecules in the internal environment of hippocampal neurons, and provide a new method for studying this process.

The protein kinase CK1: Inhibition, activation, and possible allosteric modulation

Protein kinases play a vital role in biology and deregulation of kinases is implicated in numerous diseases ranging from cancer to neurodegenerative diseases, making them a major target class for the pharmaceutical industry. However, the high degree of conservation that exists between ATP-binding sites among kinases makes it difficult for current inhibitors to be highly specific. In the context of neurodegeneration, several groups including ours, have linked different kinases such as CK1 and Alzheimer’s disease for example. Strictly CK1-isoform specific regulators do not exist and known CK1 inhibitors are inhibiting the enzymatic activity, targeting the ATP-binding site. Here we review compounds known to target CK1, as well as other inhibitory types that could benefit CK1. We introduce the DNA-encoded library (DEL) technology that might represent an interesting approach to uncover allosteric modulators instead of ATP competitors. Such a strategy, taking into account known allosteric inhibitors and mechanisms, might help designing modulators that are more specific towards a specific kinase, and in the case of CK1, toward specific isoforms.

PYK2 senses calcium through a disordered dimerization and calmodulin-binding element

Multidomain kinases use many ways to integrate and process diverse stimuli. Here, we investigated the mechanism by which the protein tyrosine kinase 2-beta (PYK2) functions as a sensor and effector of cellular calcium influx. We show that the linker between the PYK2 kinase and FAT domains (KFL) encompasses an unusual calmodulin (CaM) binding element. PYK2 KFL is disordered and engages CaM through an ensemble of transient binding events. Calcium increases the association by promoting structural changes in CaM that expose auxiliary interaction opportunities. KFL also forms fuzzy dimers, and dimerization is enhanced by CaM binding. As a monomer, however, KFL associates with the PYK2 FERM-kinase fragment. Thus, we identify a mechanism whereby calcium influx can promote PYK2 self-association, and hence kinase-activating trans-autophosphorylation. Collectively, our findings describe a flexible protein module that expands the paradigms for CaM binding and self-association, and their use for controlling kinase activity.

Protein tyrosine kinase 2-beta is shown to function as a sensor and effector of cellular calcium influx through self-association.

Pyk2 Regulates MAMs and Mitochondrial Dynamics in Hippocampal Neurons

Pyk2 is a non-receptor tyrosine kinase enriched in hippocampal neurons, which can be activated by calcium-dependent mechanisms. In neurons, Pyk2 is mostly localised in the cytosol and dendritic shafts but can translocate to spines and/or to the nucleus. Here, we explore the function of a new localisation of Pyk2 in mitochondria-associated membranes (MAMs), a subdomain of ER-mitochondria surface that acts as a signalling hub in calcium regulation. To test the role of Pyk2 in MAMs’ calcium transport, we used full Pyk2 knockout mice (Pyk2^−/−) for in vivo and in vitro studies. Here we report that Pyk2^−/− hippocampal neurons present increased ER-mitochondrial contacts along with defective calcium homeostasis. We also show how the absence of Pyk2 modulates mitochondrial dynamics and morphology. Taken all together, our results point out that Pyk2 could be highly relevant in the modulation of ER-mitochondria calcium efflux, affecting in turn mitochondrial function.