BDNF activated TrkB/IRR receptor chimera promotes survival of sympathetic neurons through Ras and PI-3 kinase signaling

Developing a novel neutralizing monoclonal antibody against TrkB

The TrkB receptor, which is highly expressed in various human cancers and considered a pro-oncogene, was targeted to develop neutralizing monoclonal antibodies against its immunoglobulin-like (Ig-like) domains. Recombinant TrkB-IgL peptide, including the Ig-like C2 type 1 (Ig-C2-type 1) and Ig-like C2 type 2 (Ig-C2-type 2) domains, was expressed and purified from E. coli. Mice were immunized with this peptide, and hybridoma clones producing anti-TrkB-IgL antibodies were generated. Among 23 ELISA-positive TrkB-IgL hybridoma clones, four (TrkB-IgL 5.11, 4.11, 4.6, 4.3) showed anti-proliferative effects compared to the control on human breast cancer (MCF-7) and human colon cancer (HCT116) cells, as assessed using the xCELLigence system. Western blot analysis revealed that TrkB-IgL 5.11 and 4.11 significantly suppressed TrkB-mediated signaling pathways compared to the control. Purified TrkB-IgL monoclonal antibodies (mAbs) exhibited anti-proliferative effects compared to both positive and negative controls using the xCELLigence system. The TrkB-IgL 5.11 mAb notably suppressed phosphorylation of TrkB, Akt, and ERK and induced Caspase-3 and Caspase-9 activities in a dose-dependent manner, as determined by Western blotting. Additionally, immunostaining confirmed the localization of these mAbs on the SH-SY5Y cell membrane, which is known for high TrkB expression. In conclusion, the TrkB-IgL 5.11 antibody effectively inhibits cancer cell proliferation and induces apoptosis by suppressing key signaling pathways. These findings demonstrate the potential of this antibody as a therapeutic agent for cancers that overexpress TrkB. Additionally, it is considered a promising candidate for humanization, which would facilitate its application in cancer treatment.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-024-04063-x.

Evaluation of VEGF, BDNF, TRKB expression in oral epithelial dysplasia, oral verrucous carcinoma and oral squamous cell carcinoma and their role as prognostic indicator

BACKGROUND

Oral squamous cell carcinoma (OSCC) is a serious health disease that can lead to a reduced quality of life or even death. It ranks sixth in terms of cancer expansion. It is one of India's primary causes of natural death. In OSCC such potentially malignant Disorders (PMDs) are precancerous lesions with such a high risk of progression. Tumor angiogenesis is a one of the basic biomarkers that may influence the proliferation of a precancerous lesion into the cancerous lesion. Tropomyosin receptor kinase B (TrkB), vascular endothelial growth factor (VEGF), and brain-derived neurotrophic factor (BDNF) also play important roles in carcinogenesis by promoting angiogenesis. The construction of new vessels of blood from existing vasculature is referred as angiogenesis.

AIM OF THE STUDY

To get deep insights of immunohistochemistry expression of VEGF, BDNF, and TRKB in oral epithelial dysplasia (OED), verrucous carcinoma (VC), and OSCC.

MATERIAL AND METHODS

The study included 100 formalin-fixed paraffin-embedded tissue blocks from 20 cases of OED, 20 cases of VC, and 60 cases of OSCC [20 cases of well-differentiated oral squamous cell carcinoma (WD-OSCC), 20 cases of moderately differentiated oral squamous cell carcinoma (MD-OSCC), and 20 cases of poorly differentiated oral squamous cell carcinoma (PD-OSCC). The staining intensity and distribution of VEGF, BNDF, and TrkB were examined and statistically analyzed using analysis of variance (ANOVA), post hoc Bonferroni test, independent t-test, Pearson's Chi-square test, and Pearson's correlation coefficient test.

RESULTS

The immunoexpression of VEGF, BDNF, and TrkB was found to be elevated in the order of OEDs, VC, and OSCC. The percentage of positive was highest in PD-OSCC, followed by MD-OSCC and WD-OSCC.

CONCLUSION

Based on our findings, angiogenesis plays a significant role in tumor growth and metastasis. A substantial relationship was discovered between VEGF, BDNF, TrkB expression, and increases in vascularity throughout the transition from OEDs to VCs and OSCCs.

Identification of INSRR as an immune-related gene in the tumor microenvironment of glioblastoma by integrated bioinformatics analysis

Gliomas are the most common malignant tumors in the central nervous system. The tumor microenvironment (TME) plays a crucial role in tumor proliferation, invasion, angiogenesis, and immune escape. However, little is known about TME in gliomas. The purpose of this study was to explore the biomarkers associated with TME in glioblastoma (GBM) to predict immunotherapy effectiveness and prognosis in patients. Based on RNA-seq transcriptome data and clinical features of 1222 samples (113 normal samples and 1109 tumor samples) in The Cancer Genome Atlas (TCGA) database, the ImmuneScore, StromalScore, and ESTIMATEScore were calculated by ESTIMATE algorithm. The differentially expressed genes (DEGs) and differentially mutated genes (DMGs) were determined in the TCGA GBM cohort. Furthermore, gene set enrichment analysis (GSEA) was used to investigate the enrichment pathways of INSRR genes with abnormal expression. The proportion of tumor-infiltrating immune cells (TIICs) was evaluated by CIBERSORT. Frequent mutations of TP53, EGFR, and PTEN occurred in high and low immune scores. The cross-analysis of DEGs and DMGs revealed that INSRR was an immune-related biomarker in the TCGA GBM cohort. According to GSEA, the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway with INSRR abnormal expression were IgA-produced intestinal immune network and Alzheimer's disease, oxidative phosphorylation, and Parkinson's disease, respectively. Additionally, INSRR expression was correlated with dendritic cells activated, dendritic cells resting, T cells CD8, and T cell gamma delta. INSRR is associated with the immune microenvironment in GBM and is used as a biomarker to predict immune invasion.

The thrombin receptor links brain derived neurotrophic factor to neuron cholesterol production, resiliency and repair after spinal cord injury

Despite concerted efforts to identify CNS regeneration strategies, an incomplete understanding of how the needed molecular machinery is regulated limits progress. Here we use models of lateral compression and FEJOTA clip contusion-compression spinal cord injury (SCI) to identify the thrombin receptor (Protease Activated Receptor 1 (PAR1)) as an integral facet of this machine with roles in regulating neurite growth through a growth factor- and cholesterol-dependent mechanism. Functional recovery and signs of neural repair, including expression of cholesterol biosynthesis machinery and markers of axonal and synaptic integrity, were all increased after SCI in PAR1 knockout female mice, while PTEN was decreased. Notably, PAR1 differentially regulated HMGCS1, a gene encoding a rate-limiting enzyme in cholesterol production, across the neuronal and astroglial compartments of the intact versus injured spinal cord. Pharmacologic inhibition of cortical neuron PAR1 using vorapaxar in vitro also decreased PTEN and promoted neurite outgrowth in a cholesterol dependent manner, including that driven by suboptimal brain derived neurotrophic factor (BDNF). Pharmacologic inhibition of PAR1 also augmented BDNF-driven HMGCS1 and cholesterol production by murine cortical neurons and by human SH-SY5Y and iPSC-derived neurons. The link between PAR1, cholesterol and BDNF was further highlighted by demonstrating that the deleterious effects of PAR1 over-activation are overcome by supplementing cultures with BDNF, cholesterol or by blocking an inhibitor of adenylate cyclase, Gαi. These findings document PAR1-linked neurotrophic coupling mechanisms that regulate neuronal cholesterol metabolism as an important component of the machinery regulating CNS repair and point to new strategies to enhance neural resiliency after injury.

Upregulation of the BDNF/TrKB pathway promotes epithelial-mesenchymal transition, as well as the migration and invasion of cervical cancer

Brain-derived neurotrophic factor (BDNF) has previously been demonstrated to be associated with several types of cancer. In addition, its receptor, tropomyosin related kinase B (TrkB) is involved in tumor invasion and metastasis. Epithelial-mesenchymal transition (EMT) is associated with metastasis in cancers. Thus, The aim of the present study was to examine whether BDNF/TrKB expression is linked to a poor survival and the acquisition of the EMT phenotype in cervical cancer. We found that a high positive expression of BDNF/TrKB was associated with poor survival in cervical cancer. Our results revealed that high expression levels of BDNF/TrKB were observed in cervical cancer compared to normal cells. Importantly, we demonstrated that the silencing of TrKB suppressed the activation of EMT via the downregulation of N-cadherin, vimentin, matrix metalloproteinase (MMP)2 and MMP9, and the upregulation of E-cadherin and tissue inhibitor of metalloproteinases (TIMP)2, which resulted in suppressed cell proliferation, migration and invasion. Furthermore, high phosphorylation levels of ERK and Akt were observed in the cervical cancer cells, while these levels were decreased in the cells in which TrKB was knocked down. On the whole, these findings suggest that the BDNF/TrKB pathway is a promising target for the prevention of tumor proliferation, invasion, metastasis and EMT in cervical cancer cells.

Alkaline pH induces IRR-mediated phosphorylation of IRS-1 and actin cytoskeleton remodeling in a pancreatic beta cell line

Secretion of mildly alkaline (pH 8.0-8.5) juice to intestines is one of the key functions of the pancreas. Recent reports indicate that the pancreatic duct system containing the alkaline juice may adjoin the endocrine cells of pancreatic islets. We have previously identified the insulin receptor-related receptor (IRR) that is expressed in islets as a sensor of mildly alkaline extracellular media. In this study, we show that those islet cells that are in contact with the excretory ducts are also IRR-expressing cells. We further analyzed the effects of alkaline media on pancreatic beta cell line MIN6. Activation of endogenous IRR but not of the insulin receptor was detected that could be inhibited with linsitinib. The IRR autophosphorylation correlated with pH-dependent linsitinib-sensitive activation of insulin receptor substrate 1 (IRS-1), the primary adaptor in the insulin signaling pathway. However, in contrast with insulin stimulation, no protein kinase B (Akt/PKB) phosphorylation was detected as a result of alkali treatment. We observed overexpression of several early response genes (EGR2, IER2, FOSB, EGR1 and NPAS4) upon alkali treatment of MIN6 cells but those were IRR-independent. The alkaline medium but not insulin also triggered actin cytoskeleton remodeling that was blocked by pre-incubation with linsitinib. We propose that the activation of IRR by alkali might be part of a local loop of signaling between the exocrine and endocrine parts of the pancreas where alkalinization of the juice facilitate insulin release that increases the volume of secreted juice to control its pH and bicabonate content.

Prenatal Cocaine Exposure Upregulates BDNF-TrkB Signaling

Prenatal cocaine exposure causes profound changes in neurobehavior as well as synaptic function and structure with compromised glutamatergic transmission. Since synaptic health and glutamatergic activity are tightly regulated by brain-derived neurotrophic factor (BDNF) signaling through its cognate tyrosine receptor kinase B (TrkB), we hypothesized that prenatal cocaine exposure alters BDNF-TrkB signaling during brain development. Here we show prenatal cocaine exposure enhances BDNF-TrkB signaling in hippocampus and prefrontal cortex (PFCX) of 21-day-old rats without affecting the expression levels of TrkB, P75^NTR, signaling molecules, NMDA receptor—NR1 subunit as well as proBDNF and BDNF. Prenatal cocaine exposure reduces activity-dependent proBDNF and BDNF release and elevates BDNF affinity for TrkB leading to increased tyrosine-phosphorylated TrkB, heightened Phospholipase C-γ1 and N-Shc/Shc recruitment and higher downstream PI3K and ERK activation in response to ex vivo BDNF. The augmented BDNF-TrkB signaling is accompanied by increases in association between activated TrkB and NMDARs. These data suggest that cocaine exposure during gestation upregulates BDNF-TrkB signaling and its interaction with NMDARs by increasing BDNF affinity, perhaps in an attempt to restore the diminished excitatory neurotransmission.

Insulin receptor-related receptor as an extracellular alkali sensor

The insulin receptor-related receptor (IRR), an orphan receptor tyrosine kinase of the insulin receptor family, can be activated by alkaline media both in vitro and in vivo at pH >7.9. The alkali-sensing property of IRR is conserved in frog, mouse, and human. IRR activation is specific, dose-dependent and quickly reversible and demonstrates positive cooperativity. It also triggers receptor conformational changes and elicits intracellular signaling. The pH sensitivity of IRR is primarily defined by its L1F extracellular domains. IRR is predominantly expressed in organs that come in contact with mildly alkaline media. In particular, IRR is expressed in the cell subsets of the kidney that secrete bicarbonate into urine. Disruption of IRR in mice impairs the renal response to alkali loading attested by development of metabolic alkalosis and decreased urinary bicarbonate excretion in response to this challenge. We therefore postulate that IRR is an alkali sensor that functions in the kidney to manage metabolic bicarbonate excess.

Activation of Erk1/2 phosphorylation but not of Akt/Pkb through an inducible CSF1R/IRR-receptor construct in INS-1E beta-cells

CONTEXT

The insulin receptor-related receptor (IRR) is an orphan receptor belonging to the insulin receptor (IR) family. Despite its unknown function, the specific tissue expression and the high sequence homology with the IR and the insulin-like growth factor 1 receptor (IGF1R) suggest a biological role in beta-cells.

OBJECTIVES

In this study we investigated the influence of a stimulatable IRR-tyrosine kinase on major IR/IGF1R signaling pathways and on proliferation and apoptosis of INS-1E beta-cells.

METHODS

INS-1E cells were stably transfected with a colony stimulating factor 1 receptor (CSF1R)/IRR construct activated by a macrophage colony stimulating factor.

RESULTS AND CONCLUSION

After stimulation the construct showed time and dose dependent autophosphorylation and transient extracellular signal regulated kinase 1/2 activation. Protein kinase b was not phosphorylated and also an effect on proliferation and apoptosis of INS-1E could not be demonstrated. Thus, no obvious biologic function of the IRR is present in INS-1E beta-cells.

Dimerization of tyrosine phosphatase PTPRO decreases its activity and ability to inactivate TrkC

Receptor-protein tyrosine phosphatases (RPTPs), like receptor tyrosine kinases, regulate neuronal differentiation. While receptor tyrosine kinases are dimerized and activated by extracellular ligands, the extent to which RPTPs dimerize, and the effects of dimerization on phosphatase activity, are poorly understood. We have examined a neuronal type III RPTP, PTPRO; we find that PTPRO can form dimers in living cells, and that disulfide linkages in PTPROs intracellular domain likely regulate dimerization. Dimerization of PTPROs transmembrane and intracellular domains, achieved by ligand binding to a chimeric fusion protein, decreases activity toward artificial peptides and toward a putative substrate, tropomyosin-related kinase C (TrkC). Dephosphorylation of TrkC by PTPRO may be physiologically relevant, as it is efficient, and TrkC and PTPRO can be co-precipitated from transfected cells. Inhibition of PTPROs phosphatase activity by dimerization is interesting, as dimerization of a related RPTP, CD148/PTPRJ, increases activity. Thus, our results suggest a complex relationship between dimerization and activity in type III RPTPs.

Neurotrophic factors in autonomic nervous system plasticity and dysfunction

During development, neurotrophic factors are known to play important roles in regulating the survival of neurons in the autonomic nervous system (ANS) and the formation of their synaptic connectivity with their peripheral targets in the cardiovascular, digestive, and other organ systems. Emerging findings suggest that neurotrophic factors may also affect the functionality of the ANS during adult life and may, in part, mediate the effects of environmental factors such as exercise and dietary energy intake on ANS neurons and target cells. In this article, we describe the evidence that ANS neurons express receptors for multiple neurotrophic factors, and data suggesting that activation of those receptors can modify plasticity in the ANS. Neurotrophic factors that may regulate ANS function include brain-derived neurotrophic factor, nerve growth factor, insulin-like growth factors, and ciliary neurotrophic factor. The possibility that perturbed neurotrophic factor signaling is involved in the pathogenesis of ANS dysfunction in some neurological disorders is considered, together with implications for neurotrophic factor-based therapeutic interventions.

Identification and characterization of compounds that potentiate NT-3-mediated Trk receptor activity

Neurotrophins are a family of secreted proteins that play an important role in the development, differentiation, and survival of neurons. Studies also suggest that aberrant neurotrophin signaling may play a role in processes underlying disease states such as schizophrenia, Alzheimer's disease, and depression. Whereas the development of agents that selectively stimulate neurotrophin signaling has proven to be difficult, compounds have been identified that potentiate neurotrophin 3 (NT-3)-mediated activation of trk A. In the present studies, we extend those initial observations to identify compounds that also potentiate NT-3-mediated activation of trk B. Compound potentiation of NT-3 was observed using several readouts of transfected and endogenous trk receptor activity, including trk receptor phosphorylation, mitogen-activated protein kinase phosphorylation, reporter assay activity (beta-lactamase and luciferase), cell survival and neurite extension assays. Studies using chimeric trk receptors demonstrated that the extracellular domain is essential for compound potentiation and rule out interaction with intracellular signaling molecules as a mechanism of compound activity. Thus, the present studies demonstrate that trk B receptor activity can be potentiated by small-molecule compounds via the extracellular domain of the receptor and provide reagents for further evaluating the role of NT-3-mediated trk A and trk B activity in vivo.

Expression of the insulin receptor-related receptor is induced by the preovulatory surge of luteinizing hormone in thecal-interstitial cells of the rat ovary

The insulin receptor-related receptor (IRR) is a member of the insulin receptor family that, on its own, recognizes neither insulin nor any of the identified insulin-related peptides. In both the nervous system and peripheral tissues, IRR mRNA is detected in cells that also express trkA, the nerve growth factor tyrosine kinase receptor. In the ovary, the trkA gene is transiently activated in thecal-interstitial cells of large antral follicles at the time of the preovulatory surge of gonadotropins. The present study shows that the IRR gene is expressed in the same ovarian compartment, that IRR mRNA content increases strikingly in these cells in the afternoon of the first proestrus, and that--as in the case of trkA mRNA--the increase is caused by gonadotropins. The IRR mRNA species primarily affected is that encoding the full-length receptor; its increased abundance was accompanied by a corresponding change in IRR protein content. An extensive molecular search using several approaches, including the screening of cDNA libraries and PCR amplification with degenerate primers, did not yield an IRR ligand. Phylogenetic analysis of 20 insulin-related sequences and 15 relaxin family peptides from selected vertebrates indicated that the mammalian genome is unlikely to contain an additional ligand expressed from a distinct gene that is closely related to the insulin family. Although the functional nature of the relationship between IRR and trkA receptors is unknown, the remarkable temporal and spatial specificities of their coordinated expression in the ovary before ovulation suggests that they target a functionally related set of downstream events associated with the ovulatory process.

Increased IL-1beta in cortex of aged rats is accompanied by downregulation of ERK and PI-3 kinase

Ageing is accompanied by a myriad of changes, which lead to deficits in synaptic function and recent studies have identified an increase in concentration of the proinflammatory cytokine, interleukin-1beta (IL-1beta), as a factor which significantly contributes to deterioration of cell function. Here, we consider that increased IL-1beta concentration and upregulation of IL-1beta-induced cell signalling cascades may be accompanied by downregulation of survival signals, perhaps as a consequence of decreased neurotrophins-associated signalling. The data indicate that increased IL-1beta concentration was coupled with downregulation of ERK and phosphoinositide-3 kinase (PI-3 kinase) in cortical tissue prepared from aged rats. These changes could not be attributed to decreased concentration of NGF or BDNF but the evidence suggested that they may be a consequence of an age-related change in the anti-inflammatory cytokine, IL-4. Significantly, treatment of aged rats with eicosapentaenoic acid reversed the age-related increases in IL-1beta and IL-1beta-induced signalling and also the age-related changes in IL-4, ERK and PI-3 kinase.

Rapid disease development in scrapie-infected mice deficient for CD40 ligand

The inhibition of CD40-CD40L interaction-mediated signalling was suggested as a therapeutic strategy for the treatment of Alzheimer's disease. Conversely, CD40-deficient neurons were reported to be more vulnerable to stress associated with ageing as well as nerve growth factor-beta and serum withdrawal. We studied the scrapie infection of CD40L-deficient (CD40L(-/-)) mice to see whether ablation of the CD40L gene would be beneficial or detrimental in this model of a neurodegenerative amyloidosis. CD40L(-/-) mice died on average 40 days earlier than wild-type control mice and exhibited a more pronounced vacuolation of the neuropil and an increased microglia activation. The experimental model indicates that a deficiency for CD40L is highly detrimental in prion diseases and reinforces the neuroprotective function of intact CD40-CD40L interactions. The stimulation of neuroprotective pathways may represent a possibility to delay therapeutically the disease onset in prion infections of the central nervous system.

Cognitive effects of atypical antipsychotics: focus on bipolar spectrum disorders

Studies examining cognitive dysfunction in bipolar disorder have documented neuropsychologic impairment in some patients. Recollection memory, attention, and visual information processing may be particularly impaired in patients with bipolar illness. Cognitive impairment appears to worsen with illness progression, and may have a significant impact on function. Pharmacotherapy to treat bipolar disorder including lithium, anticonvulsants, antidepressants, and atypical antipsychotics may have varying effects on cognitive functioning. Treatment with atypical antipsychotics has been associated with improvement in various cognitive measures in patients with schizophrenia, and the little data available in patients with bipolar disorder suggest the potential for similar benefits. Studies to determine if current treatments for bipolar disorder can prevent, delay, or even improve cognitive dysfunction are needed.

Peripheral nerve induces macrophage neurotrophic activities: regulation of neuronal process outgrowth, intracellular signaling and synaptic function

Rat cortical neurons cultured in conditioned media from human monocyte-derived macrophages (MDM) show increased neuronal protein synthesis, neurite outgrowth, mitogen-activating protein kinase activity, and synaptic function. Neurotrophic properties of human MDM-conditioned media are significantly enhanced by human peripheral nerve and to a more limited extent by CD40 ligand pre-stimulation. Such positive effects of MDM secretions on neuronal function parallel the secretion of brain-derived neurotrophic factor (BDNF). MDM activation cues may serve to balance toxic activities produced during neurodegenerative diseases and thus, under certain circumstances, mitigate neuronal degeneration.