Neuronal Menin Overexpression Rescues Learning and Memory Phenotype in CA1-Specific α7 nAChRs KD Mice

The perturbation of nicotinic cholinergic receptors is thought to underlie many neurodegenerative and neuropsychiatric disorders, such as Alzheimer’s and schizophrenia. We previously identified that the tumor suppressor gene, MEN1, regulates both the expression and synaptic targeting of α7 nAChRs in the mouse hippocampal neurons in vitro. Here we sought to determine whether the α7 nAChRs gene expression reciprocally regulates the expression of menin, the protein encoded by the MEN1 gene, and if this interplay impacts learning and memory. We demonstrate here that α7 nAChRs knockdown (KD) both in in vitro and in vivo, initially upregulated and then subsequently downregulated menin expression. Exogenous expression of menin using an AAV transduction approach rescued α7 nAChRs KD mediated functional and behavioral deficits specifically in hippocampal (CA1) neurons. These effects involved the modulation of the α7 nAChR subunit expression and functional clustering at the synaptic sites. Our data thus demonstrates a novel and important interplay between the MEN1 gene and the α7 nAChRs in regulating hippocampal-dependent learning and memory.

Elevated Sodium Pump α3 Subunit Expression Promotes Colorectal Liver Metastasis via the p53-PTEN/IGFBP3-AKT-mTOR Axis

The sodium pump α3 subunit is associated with colorectal liver metastasis. However, the underlying mechanism involved in this effect is not yet known. In this study, we found that the expression levels of the sodium pump α3 subunit were positively associated with metastasis in colorectal cancer (CRC). Knockdown of the α3 subunit or inhibition of the sodium pump could significantly inhibit the migration of colorectal cancer cells, whereas overexpression of the α3 subunit promoted colorectal cancer cell migration. Mechanistically, the α3 subunit decreased p53 expression, which subsequently downregulated PTEN/IGFBP3 and activated mTOR, leading to the promotion of colorectal cancer cell metastasis. Reciprocally, knockdown of the α3 subunit or inhibition of the sodium pump dramatically blocked this effect in vitro and in vivo via the downregulation of mTOR activity. Furthermore, a positive correlation between α3 subunit expression and mTOR activity was observed in an aggressive CRC subtype. Conclusions: Elevated expression of the sodium pump α3 subunit promotes CRC liver metastasis via the PTEN/IGFBP3-mediated mTOR pathway, suggesting that sodium pump α3 could represent a critical prognostic marker and/or therapeutic target for this disease.

The effect of age and sex on the expression of GABA signaling components in the human hippocampus and entorhinal cortex

Gamma-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the nervous system. The GABA signaling system in the brain is comprised of GABA synthesizing enzymes, transporters, GABAA and GABAB receptors (GABAAR and GABABR). Alterations in the expression of these signaling components have been observed in several brain regions throughout aging and between sexes in various animal models. The hippocampus is the memory centre of the brain and is impaired in several age-related disorders. It is composed of two main regions: the Cornu Ammonis (CA1-4) and the Dentate Gyrus (DG), which are interconnected with the Entorhinal Cortex (ECx). The age- and sex-specific changes of GABA signaling components in these regions of the human brain have not been examined. This study is the first to determine the effect of age and sex on the expression of GABA signaling components-GABAAR α1,2,3,5, β1-3, γ2, GABABR R1 and R2 subunits and the GABA synthesizing enzymes GAD 65/67-in the ECx, and the CA1 and DG regions of the human hippocampus using Western blotting. No significant differences were found in GABAAR α1,2,3,5, β1-3, γ2, GABABR R1 and R2 subunit and GAD65/76 expression levels in the ECx, CA1 and DG regions between the younger and older age groups for both sexes. However, we observed a significant negative correlation between age and GABAAR α1subunit level in the CA1 region for females; significant negative correlation between age and GABAAR β1, β3 and γ2 subunit expression in the DG region for males. In females a significant positive correlation was found between age and GABAAR γ2 subunit expression in the ECx and GABABR R2 subunit expression in the CA1 region. The results indicate that age and sex do not affect the expression of GAD 65/67. In conclusion, our results show age- and sex-related GABAA/BR subunit alterations in the ECx and hippocampus that might significantly influence GABAergic neurotransmission and underlie disease susceptibility and progression.

PATH-14. ALPHA CARDIAC ACTIN EXPRESSION IS OBSERVED IN AGGRESSIVE GLIOMA SUBTYPES AND GLIOBLASTOMA STEM CELLS

BACKGROUND Alterations in actin subunit expression have previously been observed in multiple cancers. In glioblastoma (GBM), the expression of ACTC1 has been associated with a more invasive phenotype and with shorter survival. We sought to explore the diversity of actin subunit expression across glioma subtypes and patient derived glioblastoma stem cells (GSCs). METHODS Bioinformatic analysis of multiple glioma databases was performed to profile actin subunit (ACTA1, ACTA2, ACTC1, ACTG1, ACTG2, and ACTB) mRNA levels. Expression levels were also evaluated in normal brain in comparison to liver and heart tissue. Western blot was used to analyze protein expression in GSCs, surgical tissue and human fetal astrocytes. RESULTS The primary actin subunits expressed in normal brain are beta actin (ACTB) and gamma actin (ACTG1). RNA sequencing of tissue from multiple glioma subtypes or different brain regions reveals a global increase in ACTG1 and ACTB abundance in gliomas compared to normal brain. LGG-GCIMP high and LGG-co-deleted glioma subtypes have the lowest ACTC1 expression. LGG-GCIMP low (HR 9.75, P< 0.001), LGG-mesenchymal-like (HR11.1, P< 0.001), LGG-classic-like (HR10.96, P< 0.001) subtypes are associated with ACTC1 expression. ACTC1, ACTCB, and ACTG protein expression was observed in GSCs, freshly resected GBM tissue, and human fetal astrocytes. CONCLUSIONS Gliomas have a specific pattern of actin subunit expression that differs in actin subunit type and abundance when compared to normal adult brain. Expression of ACTC1 is found in aggressive glioma subtypes and is shared by GSCs and human fetal astrocytes. Investigation into the neurodevelopmental role of ACTC1 and its contribution to oncogenic transformation in GBM is warranted.

Salt-Sensitivity of Volume and Blood Pressure in a Mouse with Globally Reduced ENaC γ Subunit Expression

The epithelial Na+ channel (ENaC) promotes the absorption of Na+ in the aldosterone-sensitive distal nephron, colon, and respiratory epithelia. Deletion of genes encoding ENaC's subunits results in early post-natal mortality. We present initial characterization of a mouse with dramatically suppressed expression of ENaC's γ subunit. We used this hypomorphic (γmt) allele to explore the importance of this subunit in homeostasis of electrolytes and body fluid volume. At baseline, γ subunit expression in γmt/mt mice was markedly suppressed in kidney and lung, while electrolytes resembled those of littermate controls. Aldosterone levels in γmt/mt mice exceeded those seen in littermate controls. Quantitative magnetic resonance (QMR) measurement of body composition revealed similar baseline body water, lean tissue mass, and fat tissue mass in γmt/mt mice and controls. γmt/mt mice exhibited a more rapid decline in body water and lean tissue mass in response to a low Na+ diet than controls. Replacement of drinking water with 2% saline selectively and transiently increased body water and lean tissue mass in γmt/mt mice, relative to controls. Lower blood pressures were variably observed in γmt/mt mice on a high salt diet, compared to controls. γmt/mt also exhibited reduced diurnal blood pressure variation, a "non-dipping" phenotype, on a high Na+ diet. While ENaC in renal tubules and colon work to prevent extracellular fluid volume depletion, our observations suggest that ENaC in other tissues may participate in regulating extracellular fluid volume and blood pressure.

Heat Stress Regulates the Expression of TPK1 Gene at Transcriptional and Post-Transcriptional Levels in Saccharomyces cerevisiae

In Saccharomyces cerevisiae, cAMP regulates a number of different cellular processes, such as cell growth, metabolism, stress resistance and gene transcription. The intracellular target for this second messenger in yeast cells is the cAMP-dependent protein kinase (PKA). The way in which a broad specificity protein kinase mediates one right physiological response after cAMP increase indicates that specificity is highly regulated in the cAMP / PKA system. Here we address the mechanism through which cAMP-PKA signalling mediates its response to heat shock thermotolerance in Saccharomyces cerevisiae. Yeast PKA is a tetrameric holoenzyme composed of a regulatory (Bcy1) subunit dimer and two catalytic subunits (Tpk1, Tpk2 and Tpk3). PKA subunits are differentially expressed under certain stress conditions. In the present study we show that, although the mRNA levels of TPK1 are upregulated upon heat shock at 37℃, no change is detected in Tpk1 protein levels. The half-life of TPK1 mRNA increases and this mRNA condensates in cytoplasmic foci upon thermal stress. The resistance of TPK1 mRNA foci to cycloheximide-induced disassembly, together with the polysome profiling analysis suggest that TPK1 mRNA is impaired for entry into translation. TPK1 mRNA foci and TPK1 expression were also evaluated during thermotolerance. The crosstalk of cAMP-PKA pathway and cell wall integrity (CWI) signalling was also studied. Wsc3 sensor and other components of the CWI pathway are necessary for the upregulation of TPK1 mRNA upon heat shock conditions. The assembly in cytoplasmic foci upon thermal stress shows to be dependent of Wsc3. Finally, evidence of an increase in the abundance of Tpk1 in the PKA holoenzyme in response to heat shock is presented. The results indicate the existence of a mechanism that exclusively regulates Tpk1 subunit expression, which contributes to cAMP-PKA specificity and also suggest that a recurrent stress enhanced the fitness for the coming favorable conditions.

Enhancement of the GluN2B subunit of glutamatergic NMDA receptors in rat brain areas after cocaine abstinence

Background: Cocaine use disorder is associated with compulsive drug-seeking and drug-taking, whereas relapse may be induced by several factors, including stress, drug-related places, people, and cues. Recent observations strongly support the involvement of the N-methyl-D-aspartate (NMDA) receptors in cocaine use disorders and abstinence, whereas withdrawal in different environments may affect the intensification of relapse. Methods: The aim of this study was to examine the GluN2B subunit expression and its association with the postsynaptic density protein 95 (PSD95) in several brain structures in rats with a history of cocaine self-administration and housed either in an enriched environment or in an isolated condition. Furthermore, a selective antagonist of the GluN2B subunit—CP 101,606 (10 and 20 mg/kg) administered during exposure to cocaine or a drug-associated conditional stimulus (a cue) was used to evaluate seeking behavior in rats. Results: In rats previously self-administering cocaine, we observed an increase in the GluN2B expression in the total homogenate from the dorsal hippocampus under both enriched environment and isolation. Cocaine abstinence under isolation conditions increased the GluN2B and GluN2B/PSD95 complex levels in the PSD fraction of the prelimbic cortex in rats previously self-administering cocaine. Administration of CP 101,606 attenuated cue-induced cocaine-seeking behavior only in isolation-housed rats. Conclusion: In summary, in this study we showed region-specific changes in both the expression of GluN2B subunit and NMDA receptor trafficking during cocaine abstinence under different housing conditions. Furthermore, we showed that the pharmacological blockade of the GluN2B subunit may be useful in attenuating cocaine-seeking behavior.