G Protein-regulated inducer of neurite outgrowth (GRIN) modulates Sprouty protein repression of mitogen-activated protein kinase (MAPK) activation by growth factor stimulation

NELL2 as a potential marker of outcome in the cerebrospinal fluid of patients with tuberculous meningitis: preliminary results from a single-center observational study

OBJECTIVE

To detect the changes in Nel-like 2 (NELL2) in cerebrospinal fluid (CSF) in the outcome of tuberculous meningitis (TBM) patients and to initially evaluate its potential as a marker.

METHODS

We collected the clinical data of patients with suspected TBM in the First People's Hospital of Zunyi from November 2017 to January 2021 and retained their CSF. According to the selection and exclusion criteria, the TBM group (11 cases) and the control group (18 cases) were obtained. Western blotting (WB) was used to detect the level of NELL2 in the CSF of the two groups, especially the change in NELL2 before and after treatment in TBM patients.

RESULTS

The level of NELL2 in the TBM group was lower than that in the control group (P < 0.05), and the level of NELL2 showed an increasing trend after anti-tuberculosis treatment in the TBM group.

CONCLUSIONS

NELL2 in the CSF of TBM patients decreased significantly. Anti-tuberculosis treatment can improve the level of NELL2, which may become one of the potential markers of outcome in the cerebrospinal fluid of patients with tuberculous meningitis.

MicroRNA-143-3p promotes human cardiac fibrosis via targeting sprouty3 after myocardial infarction

Myocardial infarction (MI) is one of the most catastrophic diseases threatening human health in the world. Because cardiomyocytes have a minuscule regenerative potential, the natural repair of infarct healing after MI shows fibrotic scar. MicroRNA-143-3p (miR-143-3p) plays a critical regulatory role in various pathophysiological processes in the heart. Sprouty3 (SPRY3) is predicted to be a potential fibrosis-associated target gene of miR-143-3p. The aim was to explore the role and mechanism of miR-143-3p in the infarct healing after MI in vivo and in vitro. Myocardial samples were obtained during autopsy from 12 human patients with or without MI. An increase in miR-143-3p mRNA levels was detected in the infarct zone of human MI samples. Moreover, silencing expression of miR-143-3p by antagomir-143-3p alleviated fibrotic scar in MI model of mice. To assess the mechanism by which miR-143-3p may function in fibrosis, human cardiac fibroblasts (HCFs) were transfected with miR-143-3p mimics and inhibitors. MiR-143-3p overexpression promoted HCFs proliferation, migration, transformation, and extracellular matrix (ECM) excessive accumulation. Additionally, miR-143-3p inhibitors reversed the fibrosis effect of HCFs treated with transforming growth β1 (TGFβ1) in vitro. Importantly, a luciferase reporter assay demonstrated that miR-143-3p could directly bind to the 3'-untranslational region (3'-UTR) of SPRY3 mRNA. Lastly, HCFs transfected with SPRY3 siRNA (si-SPRY3) enhanced the activation of the P38, ERK, and JNK pathways in the process of fibrosis. MiR-143-3p promoted fibrosis along with SPRY3 degradation and the activation of its downstream P38, ERK, and JNK pathways. Our results may contribute to improve the quality of life in MI patients by interfering with the role of miR-143-3p in MI area.

FGF1 protects neuroblastoma SH-SY5Y cells from p53-dependent apoptosis through an intracrine pathway regulated by FGF1 phosphorylation

Neuroblastoma, a sympathetic nervous system tumor, accounts for 15% of cancer deaths in children. In contrast to most human tumors, p53 is rarely mutated in human primary neuroblastoma, suggesting impaired p53 activation in neuroblastoma. Various studies have shown correlations between fgf1 expression levels and both prognosis severity and tumor chemoresistance. As we previously showed that fibroblast growth factor 1 (FGF1) inhibited p53-dependent apoptosis in neuron-like PC12 cells, we initiated the study of the interaction between the FGF1 and p53 pathways in neuroblastoma. We focused on the activity of either extracellular FGF1 by adding recombinant rFGF1 in media, or of intracellular FGF1 by overexpression in human SH-SY5Y and mouse N2a neuroblastoma cell lines. In both cell lines, the genotoxic drug etoposide induced a classical mitochondrial p53-dependent apoptosis. FGF1 was able to inhibit p53-dependent apoptosis upstream of mitochondrial events in SH-SY5Y cells by both extracellular and intracellular pathways. Both rFGF1 addition and etoposide treatment increased fgf1 expression in SH-SY5Y cells. Conversely, rFGF1 or overexpressed FGF1 had no effect on p53-dependent apoptosis and fgf1 expression in neuroblastoma N2a cells. Using different FGF1 mutants (that is, FGF1^K132E, FGF1^S130A and FGF1^S130D), we further showed that the C-terminal domain and phosphorylation of FGF1 regulate its intracrine anti-apoptotic activity in neuroblastoma SH-SY5Y cells. This study provides the first evidence for a role of an intracrine growth factor pathway on p53-dependent apoptosis in neuroblastoma, and could lead to the identification of key regulators involved in neuroblastoma tumor progression and chemoresistance.

Cross-regulation of Phosphodiesterase 1 and Phosphodiesterase 2 Activities Controls Dopamine-mediated Striatal α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid (AMPA) Receptor Trafficking

Dopamine, a key striatal neuromodulator, increases synaptic strength by promoting surface insertion and/or retention of AMPA receptors (AMPARs). This process is mediated by the phosphorylation of the GluA1 subunit of AMPAR by cyclic nucleotide-dependent kinases, making cyclic nucleotide phosphodiesterases (PDEs) potential regulators of synaptic strength. In this study, we examined the role of phosphodiesterase 2 (PDE2), a medium spiny neuron-enriched and cGMP-activated PDE, in AMPAR trafficking. We found that inhibiting PDE2 resulted in enhancement of dopamine-induced surface GluA1 expression in dopamine receptor 1-expressing medium spiny neurons. Using pharmacological and genetic approaches, we found that inhibition of PDE1 resulted in a decrease in surface AMPAR levels because of the allosteric activation of PDE2. The cross-regulation of PDE1 and PDE2 activities results in counterintuitive control of surface AMPAR expression, making it possible to regulate the directionality and magnitude of AMPAR trafficking.

The developing story of Sprouty and cancer

Sprouty proteins are evolutionarily conserved modulators of MAPK/ERK pathway. Through interacting with an increasing number of effectors, mediators, and regulators with ultimate influence on multiple targets within or beyond ERK, Sprouty orchestrates a complex, multilayered regulatory system and mediates a crosstalk among different signaling pathways for a coordinated cellular response. As such, Sprouty has been implicated in various developmental and physiological processes. Evidence shows that ERK is aberrantly activated in malignant conditions. Accordingly, Sprouty deregulation has been reported in different cancer types and shown to impact cancer development, progression, and metastasis. In this article, we have tried to provide an overview of the current knowledge about the Sprouty physiology and its regulatory functions in health, as well as an updated review of the Sprouty status in cancer. Putative implications of Sprouty in cancer biology, their clinical relevance, and their proposed applications are also revisited. As a developing story, however, role of Sprouty in cancer remains to be further elucidated.

iTRAQ-based quantitative proteomic analysis of cerebrospinal fluid reveals NELL2 as a potential diagnostic biomarker of tuberculous meningitis

Tuberculous meningitis (TBM) is a serious complication of tuberculosis that affects the central nervous system. As TBM may result in permanent sequelae and death, rapid, accurate diagnostic tests using novel biomarkers are required for the early diagnosis and treatment of TBM. A quantitative proteomic study was therefore performed to identify differential proteins in the cerebrospinal fluid (CSF) obtained from TBM patients (n=12) and healthy controls (n=12). CSF samples were labelled with iTRAQ™ and analyzed by LC-MS/MS. Gene ontology and Pathway analysis were conducted using DAVID bioinformatics resources. Neural epidermal growth factor-like like 2 (NELL2) with the largest fold-change value was selected for validation by western blotting. Proteomic phenotyping revealed over-representation in two inflammation-associated processes, complement and coagulation cascades as well as cell adhesion molecules. Western blotting showed a significant decrease in NELL2 levels in TBM subjects compared to healthy controls. The AUC analysis revealed NELL2 was able to distinguish TBM subjects from healthy controls with 83.3% sensitivity and 75% specificity. In conclusion, the results showed that CSF NELL2 is a potential diagnostic biomarker for TBM. Further evaluation of these findings in larger studies including anti-tuberculosis medicated and unmedicated patient cohorts with other intracranial infectious diseases is required for clinical translation.

Functionally selective dopamine D₂, D₃ receptor partial agonists

Dopamine D2 receptor-promoted activation of Gα(o) over Gα(i) may increase synaptic plasticity and thereby might improve negative symptoms of schizophrenia. Heterocyclic dopamine surrogates comprising a pyrazolo[1,5-a]pyridine moiety were synthesized and investigated for their binding properties when low- to subnanomolar K(i) values were determined for D(2L), D(2S), and D3 receptors. Measurement of [(35)S]GTPγS incorporation at D(2S) coexpressed with G-protein subunits indicated significant bias for promotion of Gα(o1) over Gα(i2) coupling for several test compounds. Functionally selective D(2S) activation was most striking for the carbaldoxime 8b (Gα(o1), pEC50 = 8.87, E(max) = 65%; Gα(i2), pEC50 = 6.63, E(max) = 27%). In contrast, the investigated 1,4-disubstituted aromatic piperazines (1,4-DAPs) behaved as antagonists for β-arrestin-2 recruitment, implying significant ligand bias for G-protein activation over β-arrestin-2 recruitment at D(2S) receptors. Ligand efficacy and selectivity between D(2S) and D3 activation were strongly influenced by regiochemistry and the nature of functional groups attached to the pyrazolo[1,5-a]pyridine moiety.

Cannabinoid receptor signaling in progenitor/stem cell proliferation and differentiation

Cannabinoids, the active components of cannabis (Cannabis sativa) extracts, have attracted the attention of human civilizations for centuries, much earlier than the discovery and characterization of their substrate of action, the endocannabinoid system (ECS). The latter is an ensemble of endogenous lipids, their receptors [in particular type-1 (CB1) and type-2 (CB2) cannabinoid receptors] and metabolic enzymes. Cannabinoid signaling regulates cell proliferation, differentiation and survival, with different outcomes depending on the molecular targets and cellular context involved. Cannabinoid receptors are expressed and functional from the very early developmental stages, when they regulate embryonic and trophoblast stem cell survival and differentiation, and thus may affect the formation of manifold adult specialized tissues derived from the three different germ layers (ectoderm, mesoderm and endoderm). In the ectoderm-derived nervous system, both CB1 and CB2 receptors are present in neural progenitor/stem cells and control their self-renewal, proliferation and differentiation. CB1 and CB2 show opposite patterns of expression, the former increasing and the latter decreasing along neuronal differentiation. Recently, endocannabinoid (eCB) signaling has also been shown to regulate proliferation and differentiation of mesoderm-derived hematopoietic and mesenchymal stem cells, with a key role in determining the formation of several cell types in peripheral tissues, including blood cells, adipocytes, osteoblasts/osteoclasts and epithelial cells. Here, we will review these new findings, which unveil the involvement of eCB signaling in the regulation of progenitor/stem cell fate in the nervous system and in the periphery. The developmental regulation of cannabinoid receptor expression and cellular/subcellular localization, together with their role in progenitor/stem cell biology, may have important implications in human health and disease.

Suppression of outward K⁺ currents by WIN55212-2 in rat retinal ganglion cells is independent of CB1/CB2 receptors

Cannabinoid CB1 receptor (CB1R) signaling system is extensively distributed in the vertebrate retina. Activation of CB1Rs regulates a variety of functions of retinal neurons through modulating different ion channels. In the present work we studied effects of this receptor signaling on K(+) channels in retinal ganglion cells by patch-clamp techniques. The CB1R agonist WIN55212-2 (WIN) suppressed outward K(+) currents in acutely isolated rat retinal ganglion cells in a dose-dependent manner, with an IC50 of 4.7 μM. We further showed that WIN mainly suppressed the tetraethylammonium (TEA)-sensitive K(+) current component. While CB1Rs were expressed in rat retinal ganglion cells, the WIN effect on K(+) currents was not blocked by either AM251/SR141716, specific CB1R antagonists, or AM630, a selective CB2R antagonist. Consistently, cAMP-protein kinase A (PKA) and mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) signaling pathways were unlikely involved in the WIN-induced suppression of the K(+) currents because both PKA inhibitors H-89/Rp-cAMP and MAPK/ERK1/2 inhibitor U0126 failed to block the WIN effects. WIN-induced suppression of the K(+) currents was not observed when WIN was intracellularly applied. Furthermore, an endogenous ligand of the cannabinoid receptor anandamide, the specific CB1R agonist ACEA and the selective CB2R agonist CB65 also suppressed the K(+) currents, and the effects were not blocked by AM251/SR141716 or AM630 respectively. All these results suggest that the WIN-induced suppression of the outward K(+) currents in rat retinal ganglion cells, thereby regulating the cell excitability, were not through CB1R/CB2R signaling pathways.

ERK regulation of phosphodiesterase 4 enhances dopamine-stimulated AMPA receptor membrane insertion

AMPA-type glutamate receptor (AMPAR) trafficking is essential for modulating synaptic transmission strength. Prior studies that have characterized signaling pathways underlying AMPAR trafficking have identified the cAMP/PKA-mediated phosphorylation of GluA1, an AMPAR subunit, as a key step in the membrane insertion of AMPAR. Inhibition of ERK impairs AMPAR membrane insertion, but the mechanism by which ERK exerts its effect is unknown. Dopamine, an activator of both PKA and ERK, induces AMPAR insertion, but the relationship between the two protein kinases in the process is not understood. We used a combination of computational modeling and live cell imaging to determine the relationship between ERK and PKA in AMPAR insertion. We developed a dynamical model to study the effects of phosphodiesterase 4 (PDE4), a cAMP phosphodiesterase that is phosphorylated and inhibited by ERK, on the membrane insertion of AMPAR. The model predicted that PKA could be a downstream effector of ERK in regulating AMPAR insertion. We experimentally tested the model predictions and found that dopamine-induced ERK phosphorylates and inhibits PDE4. This regulation results in increased cAMP levels and PKA-mediated phosphorylation of DARPP-32 and GluA1, leading to increased GluA1 trafficking to the membrane. These findings provide unique insight into an unanticipated network topology in which ERK uses PDE4 to regulate PKA output during dopamine signaling. The combination of dynamical models and experiments has helped us unravel the complex interactions between two protein kinase pathways in regulating a fundamental molecular process underlying synaptic plasticity.

Regulation of neurite growth by inorganic pyrophosphatase 1 via JNK dephosphorylation

Neural cell differentiation during development is controlled by multiple signaling pathways, in which protein phosphorylation and dephosphorylation play an important role. In this study, we examined the role of pyrophosphatase1 (PPA1) in neuronal differentiation using the loss and gain of function analysis. Neuronal differentiation induced by external factors was studied using a mouse neuroblastoma cell line (N1E115). The neuronal like differentiation in N1E115 cells was determined by morphological analysis based on neurite growth length. In order to analyze the loss of the PPA1 function in N1E115, si-RNA specifically targeting PPA1 was generated. To study the effect of PPA1 overexpression, an adenoviral gene vector containing the PPA1 gene was utilized to infect N1E115 cells. To address the need for pyrophosphatase activity in PPA1, D117A PPA1, which has inactive pyrophosphatase, was overexpressed in N1E115 cells. We used valproic acid (VPA) as a neuronal differentiator to examine the effect of PPA1 in actively differentiated N1E115 cells. Si-PPA1 treatment reduced the PPA1 protein level and led to enhanced neurite growth in N1E115 cells. In contrast, PPA1 overexpression suppressed neurite growth in N1E115 cells treated with VPA, whereas this effect was abolished in D117A PPA1. PPA1 knockdown enhanced the JNK phosphorylation level, and PPA1 overexpression suppressed it in N1E115 cells. It seems that recombinant PPA1 can dephosphorylate JNK while no alteration of JNK phosphorylation level was seen after treatment with recombinant PPA1 D117A. Enhanced neurite growth by PPA1 knockdown was also observed in rat cortical neurons. Thus, PPA1 may play a role in neuronal differentiation via JNK dephosphorylation.

Endocannabinoids via CB₁ receptors act as neurogenic niche cues during cortical development

During brain development, neurogenesis is precisely regulated by the concerted action of intrinsic factors and extracellular signalling systems that provide the necessary niche information to proliferating and differentiating cells. A number of recent studies have revealed a previously unknown role for the endocannabinoid (ECB) system in the control of embryonic neuronal development and maturation. Thus, the CB(1) cannabinoid receptor in concert with locally produced ECBs regulates neural progenitor (NP) proliferation, pyramidal specification and axonal navigation. In addition, subcellularly restricted ECB production acts as an axonal growth cone signal to regulate interneuron morphogenesis. These findings provide the rationale for understanding better the consequences of prenatal cannabinoid exposure, and emphasize a novel role of ECBs as neurogenic instructive cues involved in cortical development. In this review the implications of altered CB(1)-receptor-mediated signalling in developmental disorders and particularly in epileptogenesis are briefly discussed.