Hippocampal SorCS2 overexpression represses chronic stress-induced depressive-like behaviors by promoting the BDNF-TrkB system.

BACKGROUND: Emerging data has demonstrated that in mature neurons, SorCS2 localizes to the postsynaptic density of dendritic spines and facilitates plasma membrane sorting of TrkB by interacting with it, transmitting positive signaling from BDNF on neurons. Thus, it is possible that SorCS2 plays a role in the pathophysiology of depression by regulating the BDNF-TrkB system. METHODS: In the present study, SorCS2 expression in different brain regions [hippocampus, medial prefrontal cortex (mPFC), hypothalamus, amygdala, ventral tegmental area (VTA), and nucleus accumbens (NAc)] was thoroughly investigated in the chronic social defeat stress (CSDS) and chronic unpredictable mild stress (CUMS) models of depression. The changes in depressive-like behaviors, the hippocampal BDNF signaling cascade, and amounts of hippocampal immature neurons were further investigated after SorCS2 overexpression by microinjection of the adenovirus associated virus vector containing the coding sequence of mouse SorCS2 (AAV-SorCS2) into the hippocampus of mice exposed to CSDS or CUMS. RESULTS: It was found that both CSDS and CUMS significantly decreased the protein and mRNA expression of SorCS2 in the hippocampus but not in other brain regions. Chronic stress also notably downregulated the level of hippocampal SorCS2-TrkB binding in mice. In contrast, AAV-based genetic overexpression of hippocampal SorCS2 fully reversed the chronic stress-induced not only depressive-like behaviors but also decreased SorCS2-TrkB binding, BDNF signaling pathway, and amounts of immature neurons in the hippocampus of mice. CONCLUSION: All these results suggest that enhancing the hippocampal SorCS2 expression protects against chronic stress, producing antidepressant-like actions. Hippocampal SorCS2 may participate in depression neurobiology and be a potential antidepressant target. SIGNIFICANCE STATEMENT: Targeting of proteins to distinct subcellular compartments is essential for neuronal activity and modulated by VPS10P domain receptors which include SorCS2. In mature neurons, SorCS2 localizes to the postsynaptic density of dendritic spines and facilitates plasma membrane sorting of TrkB by interacting with it, transmitting positive signaling from BDNF on neurons. Our study is the first direct evidence preliminarily showing that SorCS2 plays a role in depression neurobiology. It was found that chronic stress induced not only depressive-like behaviors but also decreased SorCS2 expression in the hippocampus. Chronic stress did not affect SorCS2 expression in the mPFC, hypothalamus, amygdala, VTA, or NAc. In contrast, genetic overexpression of hippocampal SorCS2 prevented against chronic stress, producing antidepressant-like actions in mice. Thus, hippocampal SorCS2 is a potential participant underlying depression neurobiology and may be a novel antidepressant target. Our study may also extend the knowledge of the neurotrophic hypothesis of depression.

MiR-130a-3p regulates neural stem cell differentiation in vitro by targeting Acsl4.

In the adult mammalian brain, neural stem cells (NSCs) are the precursor cells of neurons that contribute to nervous system development, regeneration, and repair. MicroRNAs (miRNAs) are small non-coding RNAs that regulate cell fate determination and differentiation by negatively regulating gene expression. Here, we identified a post-transcriptional mechanism, centred around miR-130a-3p that regulated NSC differentiation. Importantly, overexpressing miR-130a-3p promoted NSC differentiation into neurons, whereas inhibiting miR-130a-3p function reduced the number of neurons. Then, the quantitative PCR, Western blot and dual-luciferase reporter assays showed that miR-130a-3p negatively regulated acyl-CoA synthetase long-chain family member 4 (Acsl4) expression. Additionally, inhibition of Acsl4 promoted NSC differentiation into neurons, whereas silencing miR-130a-3p partially suppressed the neuronal differentiation induced by inhibiting Acsl4. Furthermore, overexpressing miR-130a-3p or inhibiting Acsl4 increased the levels of p-AKT, p-GSK-3ß and PI3K. In conclusion, our results suggested that miR-130a-3p targeted Acsl4 to promote neuronal differentiation of NSCs via regulating the Akt/PI3K pathway. These findings may help to develop strategies for stem cell-mediated treatment for central nervous system diseases.

miR-103-3p targets Ndel1 to regulate neural stem cell proliferation and differentiation.

The regulation of adult neural stem cells (NSCs) is critical for lifelong neurogenesis. MicroRNAs (miRNAs) are a type of small, endogenous RNAs that regulate gene expression post-transcriptionally and influence signaling networks responsible for several cellular processes. In this study, miR-103-3p was transfected into neural stem cells derived from embryonic hippocampal neural stem cells. The results showed that miR-103-3p suppressed neural stem cell proliferation and differentiation, and promoted apoptosis. In addition, miR-103-3p negatively regulated NudE neurodevelopment protein 1-like 1 (Ndel1) expression by binding to the 3' untranslated region of Ndel1. Transduction of neural stem cells with a lentiviral vector overexpressing Ndel1 significantly increased cell proliferation and differentiation, decreased neural stem cell apoptosis, and decreased protein expression levels of Wnt3a, ß-catenin, phosphor-GSK-3ß, LEF1, c-myc, c-Jun, and cyclin D1, all members of the Wnt/ß-catenin signaling pathway. These findings suggest that Ndel1 is a novel miR-103-3p target and that miR-103-3p acts by suppressing neural stem cell proliferation and promoting apoptosis and differentiation. This study was approved by the Animal Ethics Committee of Nantong University, China (approval No. 20200826-003) on August 26, 2020.

miR-33-3p Regulates PC12 Cell Proliferation and Differentiation In Vitro by Targeting Slc29a1.

MicroRNA-33-3p (miR-33-3p) has been widely investigated for its roles in lipid metabolism and mitochondrial function; however, there are few studies on miR-33-3p in the context of neurological diseases. In this study, we investigated the functional role of miR-33-3p in rat pheochromocytoma PC12 cells. A miR-33-3p mimic was transduced into PC12 cells, and its effects on proliferation, apoptosis, and differentiation were studied using the MTS assay, EdU labeling, flow cytometry, qRT-PCR, western blot, ELISA, and immunofluorescence. We found that miR-33-3p significantly suppressed PC12 cell proliferation, but had no effect on apoptosis. Furthermore, miR-33-3p promoted the differentiation of PC12 cells into Tuj1-positive and choline acetyltransferase-positive neuron-like cells. Mechanistically, miR-33-3p repressed the expression of Slc29a1 in PC12 cells. Importantly, knocking down Slc29a1 in PC12 cells inhibited proliferation and induced differentiation into neuron-like cells. In conclusion, this study showed that miR-33-3p regulated Slc29a1, which in turn controlled the proliferation and differentiation of PC12 cells. Thus, we hypothesize that the miR-33-3p/Slc29a1 axis could be a promising therapeutic target for recovering neurons and the cholinergic nervous system.

Long non-coding RNA GAS5 promotes PC12 cells differentiation into Tuj1-positive neuron-like cells and induces cell cycle arrest.

Growth arrest-specific 5 (GAS5) is an anti-oncogene that has been extensively studied in tumors. However, research on GAS5 in the context of nervous system disease is rare at present. This study aimed to investigate the role of the long non-coding RNA GAS5 in rat pheochromocytoma cells (PC12 cells). GAS5-overexpressing lentivirus was transfected into PC12 cells, and expression levels of GAS5 and C-myc were detected by real-time PCR. Ratios of cells in S phase were detected by 5-ethynyl-2'-deoxyuridine. Immunohistochemical staining was used to detect the immunoreactivity of neuron microtubule markers Tuj1, doublecortin, and microtubule-associated protein 2. Apoptosis was detected by flow cytometry, while expression of acetylcholine in cells was detected by western blot assay. We found that GAS5 can promote PC12 cells to differentiate into Tuj1-positive neuron-like cells with longer processes. In addition, cell proliferation and cell cycle were significantly suppressed by GAS5, whereas it had no effect on apoptosis of PC12 cells. Our results indicate that GAS5 could increase the expression of choline acetyltransferase and acetylcholine release. Thus, we speculate that GAS5 is beneficial to the recovery of neurons and the cholinergic nervous system.

Denervated hippocampus provides a favorable microenvironment for neuronal differentiation of endogenous neural stem cells.

Fimbria-fornix transection induces both exogenous and endogenous neural stem cells to differentiate into neurons in the hippocampus. This indicates that the denervated hippocampus provides an environment for neuronal differentiation of neural stem cells. However, the pathways and mechanisms in this process are still unclear. Seven days after fimbria fornix transection, our reverse transcription polymerase chain reaction, western blot assay, and enzyme linked immunosorbent assay results show a significant increase in ciliary neurotrophic factor mRNA and protein expression in the denervated hippocampus. Moreover, neural stem cells derived from hippocampi of fetal (embryonic day 17) Sprague-Dawley rats were treated with ciliary neurotrophic factor for 7 days, with an increased number of microtubule associated protein-2-positive cells and decreased number of glial fibrillary acidic protein-positive cells detected. Our results show that ciliary neurotrophic factor expression is up-regulated in the denervated hippocampus, which may promote neuronal differentiation of neural stem cells in the denervated hippocampus.