Chromatin Remodeling Factor SMARCA5 is Essential for Hippocampal Memory Maintenance via Metabolic Pathways in Mice.

Gene transcription and new protein synthesis regulated by epigenetics play integral roles in the formation of new memories. However, as an important part of epigenetics, the function of chromatin remodeling in learning and memory has been less studied. Here, we showed that SMARCA5 (SWI/SNF related, matrix-associated, actin-dependent regulator of chromatin, subfamily A, member 5), a critical chromatin remodeler, was responsible for hippocampus-dependent memory maintenance and neurogenesis. Using proteomics analysis, we found protein expression changes in the hippocampal dentate gyrus (DG) after the knockdown of SMARCA5 during contextual fear conditioning (CFC) memory maintenance in mice. Moreover, SMARCA5 was revealed to participate in CFC memory maintenance via modulating the proteins of metabolic pathways such as nucleoside diphosphate kinase-3 (NME3) and aminoacylase 1 (ACY1). This work is the first to describe the role of SMARCA5 in memory maintenance and to demonstrate the involvement of metabolic pathways regulated by SMARCA5 in learning and memory.

miRNA-126a-3p participates in hippocampal memory via alzheimer's disease-related proteins.

Memory formation and consolidation necessitate gene expression and new protein synthesis. MicroRNAs (miRNAs), a family of small noncoding RNAs that inhibit target gene mRNA expression, are involved in new memory formation. In this study, elevated miR-126a-3p (miR-126) levels were found to contribute to the consolidation of contextual fear memory. Using different commonly mined algorithms and luciferase reporter assay, we found two Alzheimer's disease (AD)-related proteins, namely EFHD2 and BACE1, but not ADAM9, were the targets downregulated by miR-126 after CFC training. Moreover, we indicated that upregulated miR-126 could promote the formation of contextual fear memory by modulating its target EFHD2. Finally, we demonstrated that miR-126 overexpression in dentate gyrus of hippocampus could reduce Aß plaque area and neuroinflammation, as well as rescue the hippocampal memory deficits in APP/PS1 mice. This study adds to the growing body of evidence for the role of miRNAs in memory formation and demonstrates the implication of EFHD2 protein regulated by miR-126 in the adult brain.

Dysregulation of non-coding RNAs mediates cisplatin resistance in hepatocellular carcinoma and therapeutic strategies.

Hepatocellular carcinoma (HCC) is the fourth major contributor to cancer-related deaths worldwide, and patients mostly have poor prognosis. Although several drugs have been approved for the treatment of HCC, cisplatin (CDDP) is still applied in treatment of HCC as a classical chemotherapeutic drug. Unfortunately, the emergence of CDDP resistance has caused HCC patients to exhibit poor drug response. How to mitigate or even reverse CDDP resistance is an urgent clinical issue to be solved. Because of critical roles in biological functional processes and disease developments, non-coding RNAs (ncRNAs) have been extensively studied in HCC in recent years. Importantly, ncRNAs have also been demonstrated to be involved in the development of HCC to CDDP resistance process. Therefore, this review highlighted the regulatory roles of ncRNAs in CDDP resistance of HCC, elucidated the multiple potential mechanisms by which HCC develops CDDP resistance, and attempted to propose multiple drug delivery systems to alleviate CDDP resistance. Recently, ncRNA-based therapy may be a feasible strategy to alleviate CDDP resistance in HCC. Meanwhile, nanoparticles can overcome the deficiencies in ncRNA-based therapy and make it possible to reverse tumor drug resistance. The combined use of these strategies provides clues for reversing CDDP resistance and overcoming the poor prognosis of HCC.

miR-151-5p modulates APH1a expression to participate in contextual fear memory formation.

Long-term memory formation requires gene expression and new protein synthesis. MicroRNAs (miRNAs), a family of small non-coding RNAs that inhibit target gene mRNA expression, are involved in new memory formation. In this study, elevated miR-151-5p (miR-151) levels were found to be responsible for hippocampal contextual fear memory formation. Using a luciferase reporter assay, we demonstrated that miR-151 targets APH1a, a protein that has been identified as a key factor in γ-secretase activity, namely APH1a. Blocking miR-151 can upregulate APH1a protein levels and subsequently impair hippocampal fear memory formation. These results indicate that miR-151 is involved in hippocampal contextual fear memory by inhibiting APH1a protein expression. This work provides novel evidence for the role of miRNAs in memory formation and demonstrates the implication of APH1a protein in miRNA processing in the adult brain.

Elevating Integrin-linked Kinase expression has rescued hippocampal neurogenesis and memory deficits in an AD animal model.

Alterations in adult neurogenesis have been regarded as a major cause of cognitive impairment in Alzheimer's disease (AD). The underlying mechanism of neurogenesis deficiency in AD remains unclear. In this study, we reported that Integrin-linked Kinase (ILK) protein levels and phosphorylation were significantly decreased in the hippocampus of APP/PS1 mice. Increased ILK expression of dentate gyrus (DG) rescued the hippocampus-dependent neurogenesis and memory deficits in APP/PS1 mice. Moreover, we demonstrated that the effect of ILK overexpression in the hippocampus was exerted via AKT-GSK3ß pathway. Finally, we found that Fluoxetine, a selective serotonin reuptake inhibitor, could improve the impaired hippocampal neurogenesis and memory by enhancing ILK-AKT-GSK3ß pathway activity in APP/PS1 mice. Thus, these findings demonstrated the effects of ILK on neurogenesis and memory recovery, suggesting that ILK is an important therapeutic target for AD prevention and treatment.

miR-181a Participates in Contextual Fear Memory Formation Via Activating mTOR Signaling Pathway.

Long-term memory formation has been proven to require gene expression and new protein synthesis. MicroRNAs (miRNAs), as an endogenous small non-coding RNAs, inhibit the expression of their mRNA targets, through which involve in new memory formation. In this study, elevated miR-181a levels were found to be responsible for hippocampal contextual fear memory consolidation. Using a luciferase reporter assay, we indicated that miR-181a targets 2 upstream molecules of mTOR pathway, namely, PRKAA1 and REDD1. Upregulated miR-181a can downregulate the PRKAA1 and REDD1 protein levels and promote mTOR activity to facilitate hippocampal fear memory consolidation. These results indicate that miR-181a is involved in hippocampal contextual fear memory by activating the mTOR signaling pathway. This work provides a novel evidence for the role of miRNAs in memory formation and demonstrates the implication of mTOR signaling pathway in miRNA processing in the adult brain.

HDAC7 Ubiquitination by the E3 Ligase CBX4 Is Involved in Contextual Fear Conditioning Memory Formation.

Histone acetylation, an epigenetic modification, plays an important role in long-term memory formation. Recently, histone deacetylase (HDAC) inhibitors were demonstrated to promote memory formation, which raises the intriguing possibility that they may be used to rescue memory deficits. However, additional research is necessary to clarify the roles of individual HDACs in memory. In this study, we demonstrated that HDAC7, within the dorsal hippocampus of C57BL6J mice, had a late and persistent decrease after contextual fear conditioning (CFC) training (4-24 h), which was involved in long-term CFC memory formation. We also showed that HDAC7 decreased via ubiquitin-dependent degradation. CBX4 was one of the HDAC7 E3 ligases involved in this process. Nur77, as one of the target genes of HDAC7, increased 6-24 h after CFC training and, accordingly, modulated the formation of CFC memory. Finally, HDAC7 was involved in the formation of other hippocampal-dependent memories, including the Morris water maze and object location test. The current findings facilitate an understanding of the molecular and cellular mechanisms of HDAC7 in the regulation of hippocampal-dependent memory.SIGNIFICANCE STATEMENT The current findings demonstrated the effects of histone deacetylase 7 (HDAC7) on hippocampal-dependent memories. Moreover, we determined the mechanism of decreased HDAC7 in contextual fear conditioning (CFC) through ubiquitin-dependent protein degradation. We also verified that CBX4 was one of the HDAC7 E3 ligases. Finally, we demonstrated that Nur77, as one of the important targets for HDAC7, was involved in CFC memory formation. All of these proteins, including HDAC7, CBX4, and Nur77, could be potential therapeutic targets for preventing memory deficits in aging and neurological diseases.

Integrin-linked Kinase is Essential for Environmental Enrichment Enhanced Hippocampal Neurogenesis and Memory.

Environment enrichment (EE) has a variety of effects on brain structure and function. Brain-derived neurotrophic factor (BDNF) is essential for EE-induced hippocampal neurogenesis and memory enhancement. However, the intracellular pathway downstream of BDNF to modulate EE effects is poorly understood. Here we show that integrin-linked kinase (ILK) levels are elevated upon EE stimuli in a BDNF-dependent manner. Using ILK-shRNA (siILK) lentivirus, we demonstrate that knockdown of ILK impairs EE-promoted hippocampal neurogenesis and memory by increasing glycogen synthase kinase-3ß (GSK3ß) activity. Finally, overexpressing ILK in the hippocampus could rescue the neurogenesis and memory deficits in BDNF(+/-) mice. These results indicate that ILK is indispensable for BDNF-mediated hippocampal neurogenesis and memory enhancement upon EE stimuli via regulating GSK3ß activity. This is a new insight of the precise mechanism in EE-enhanced memory processes and ILK is a potentially important therapeutic target that merits further study.

Syntaxin 8 modulates the post-synthetic trafficking of the TrkA receptor and inflammatory pain transmission.

Nerve growth factor (NGF) promotes the survival, maintenance, and neurite outgrowth of sensory and sympathetic neurons, and the effects are mediated by TrkA receptor signaling. Thus, the cell surface location of the TrkA receptor is crucial for NGF-mediated functions. However, the regulatory mechanism underlying TrkA cell surface levels remains incompletely understood. In this study, we identified syntaxin 8 (STX8), a Q-SNARE protein, as a novel TrkA-binding protein. Overexpression and knockdown studies showed that STX8 facilitates TrkA transport from the Golgi to the plasma membrane and regulates the surface levels of TrkA but not TrkB receptors. Furthermore, STX8 modulates downstream NGF-induced TrkA signaling and, consequently, the survival of NGF-dependent dorsal root ganglia neurons. Finally, knockdown of STX8 in rat dorsal root ganglia by recombinant adeno-associated virus serotype 6-mediated RNA interference led to analgesic effects on formalin-induced inflammatory pain. These findings demonstrate that STX8 is a modulator of TrkA cell surface levels and biological functions.

Gypenosides pre-treatment protects the brain against cerebral ischemia and increases neural stem cells/progenitors in the subventricular zone.

Gypenosides (GPs) have been reported to have neuroprotective effects in addition to other bioactivities. The protective activity of GPs during stroke and their effects on neural stem cells (NSCs) in the ischemic brain have not been fully elucidated. Here, we test the effects of GPs during stroke and on the NSCs within the subventricular zone (SVZ) of middle cerebral artery occlusion (MCAO) rats. Our results show that pre-treatment with GPs can reduce infarct volume and improve motor function following MCAO. Pre-treatment with GPs significantly increased the number of BrdU-positive cells in the ipsilateral and contralateral SVZ of MCAO rats. The proliferating cells in both sides of the SVZ were glial fibrillary acidic protein (GFAP)/nestin-positive type B cells and doublecortin (DCX)/nestin-positive type A cells. Our data indicate that GPs have neuroprotective effects during stroke which might be mediated through the enhancement of neurogenesis within the SVZ. These findings provide new evidence for a potential therapy involving GPs for the treatment of stroke.

Transcriptome profiling analysis of the mechanisms underlying the BDNF Val66Met polymorphism induced dysfunctions of the central nervous system.

Brain-derived neurotrophic factor (BDNF) Val66Met polymorphism affects postnatal behaviors and is associated with a variety of neuropsychiatric disorders. However, the mechanisms underlying the BDNF(Met) variant induced dysfunctions of the central nervous system remain obscure. In order to identify the candidate genes and pathways responsible for the dysfunctions associated with this BDNF variation, we analyzed the expression of genes in the hippocampus, prefrontal cortex, and amygdala of the BDNF(Met) variant mice in comparison with the wild-type mice using Illumina bead microarray. Transcriptome profiling analysis revealed region-distinctive and gene-dose dependent changes of gene expression associated with the BDNF(Met) variant. BDNF(Met) variant mice exhibited altered expression of genes associated with translational machinery, neuronal plasticity and mitochondrial function based on the gene ontology (GO) annotation. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that the chemokine, cell adhesion, ubiquitin-proteosome and wnt signaling pathways were altered in the BDNF(Met) variant mice brain. Finally, the CX3CL1/CX3CR1 signaling was identified to be impaired in the hippocampus and microinjection of CX3CL1 into the hippocampus could rescue the hippocampal dependent memory deficits in BDNF(Met/Met) mice, indicating that CX3CL1 may be an effective treatment option for memory disorders in humans with this genetic BDNF variation. These findings will help us further understanding the molecular mechanisms involved in the BDNF(Met) associated behavior and neuroanatomy alternations.

Phosphorylation of cofilin regulates extinction of conditioned aversive memory via AMPAR trafficking.

Actin dynamics provide an important mechanism for the modification of synaptic plasticity, which is regulated by the actin depolymerizing factor (ADF)/cofilin. However, the role of cofilin regulated actin dynamics in memory extinction process is still unclear. Here, we observed that extinction of conditioned taste aversive (CTA) memory led to temporally enhanced ADF/cofilin activity in the infralimbic cortex (IrL) of the rats. Moreover, temporally elevating ADF/cofilin activity in the IrL could accelerate CTA memory extinction by facilitating AMPAR synaptic surface recruitment, whereas inhibition of ADF/cofilin activity abolished AMPAR synaptic surface trafficking and impaired memory extinction. Finally, we observed that ADF/cofilin-regulated synaptic plasticity was not directly coupled to morphological changes of postsynaptic spines. These findings may help us understand the role of ADF/cofilin-regulated actin dynamics in memory extinction and suggest that appropriate manipulating ADF/cofilin activity might be a suitable way for therapeutic treatment of memory disorders.