Illustrating the biological functions and diagnostic value of transmembrane protein family members in glioma.

Background: It is well-established that patients with glioma have a poor prognosis. Although the past few decades have witnessed unprecedented medical advances, the 5-year survival remains dismally low. Objective: This study aims to investigate the role of transmembrane protein-related genes in the development and prognosis of glioma and provide new insights into the pathogenesis of the disease. Methods: The datasets of glioma patients, including RNA sequencing data and relative clinical information, were obtained from The Cancer Genome Atlas (TCGA), Chinese Glioma Genome Atlas (CGGA) and Gene Expression Omnibus (GEO) databases. Prognostic transmembrane protein-related genes were identified by univariate Cox analysis. New disease subtypes were recognized based on the consensus clustering method, and their biological uniqueness was verified via various algorithms. The prognosis signature was constructed using the LASSO-Cox regression model, and its predictive power was validated in external datasets by receiver operating characteristic (ROC) curve analysis. An independent prognostic analysis was conducted to evaluate whether the signature could be considered a prognostic factor independent of other variables. A nomogram was constructed in conjunction with traditional clinical variables. The concordance index (C-index) and Decision Curve Analysis (DCA) were used to assess the net clinical benefit of the signature over traditional clinical variables. Seven different softwares were used to compare the differences in immune infiltration between the high- and low-risk groups to explore potential mechanisms of glioma development and prognosis. Hub genes were found using the random forest method, and their expression was based on multiple single-cell datasets. Results: Four molecular subtypes were identified, among which the C1 group had the worst prognosis. Principal Component Analysis (PCA) results and heatmaps indicated that prognosis-related transmembrane protein genes exhibited differential expression in all four groups. Besides, the microenvironment of the four groups exhibited significant heterogeneity. The 6 gene-based signatures could predict the 1-, 2-, and 3-year overall survival (OS) of glioma patients. The signature could be used as an independent prognosis factor of glioma OS and was superior to traditional clinical variables. More immune cells were infiltrated in the high-risk group, suggesting immune escape. According to our signature, many genes were associated with the content of immune cells, which revealed that transmembrane protein-related genes might influence the development and prognosis of glioma by regulating the immune microenvironment. TMEM158 was identified as the most important gene using the random forest method. The single-cell datasets consistently showed that TMEM158 was expressed in multiple malignant cells. Conclusion: The expression of transmembrane protein-related genes is closely related to the immune status and prognosis of glioma patients by regulating tumor progression in various ways. The interaction between transmembrane protein-related genes and immunity during glioma development lays the groundwork for future studies on the molecular mechanism and targeted therapy of glioma.

Arginine Reduces Glycation in γ2 Subunit of AMPK and Pathologies in Alzheimer's Disease Model Mice.

The metabolism disorders are a common convergence of Alzheimer's disease (AD) and type 2 diabetes mellitus (T2DM). The characteristics of AD are senile plaques and neurofibrillary tangles (NFTs) composed by deposits of amyloid-ß (Aß) and phosphorylated tau, respectively. Advanced glycation end-products (AGEs) are a stable modification of proteins by non-enzymatic reactions, which could result in the protein dysfunction. AGEs are associated with some disease developments, such as diabetes mellitus and AD, but the effects of the glycated γ2 subunit of AMPK on its activity and the roles in AD onset are unknown. METHODS: We studied the effect of glycated γ2 subunit of AMPK on its activity in N2a cells. In 3 × Tg mice, we administrated L-arginine once every two days for 45 days and evaluated the glycation level of γ2 subunit and function of AMPK and alternation of pathologies. RESULTS: The glycation level of γ2 subunit was significantly elevated in 3 × Tg mice as compared with control mice, meanwhile, the level of pT172-AMPK was obviously lower in 3 × Tg mice than that in control mice. Moreover, we found that arginine protects the γ2 subunit of AMPK from glycation, preserves AMPK function, and improves pathologies and cognitive deficits in 3 × Tg mice. CONCLUSIONS: Arginine treatment decreases glycated γ2 subunit of AMPK and increases p-AMPK levels in 3 × Tg mice, suggesting that reduced glycation of the γ2 subunit could ameliorate AMPK function and become a new target for AD therapy in the future.

Nmnat2 attenuates amyloidogenesis and up-regulates ADAM10 in AMPK activity-dependent manner.

Amyloid-ß (Aß) accumulating is considered as a causative factor for formation of senile plaque in Alzheimer's disease (AD), but its mechanism is still elusive. The Nicotinamide mononucleotide adenylyltransferase 2 (Nmnat2), a key redox cofactor for energy metabolism, is reduced in AD. Accumulative evidence has shown that the decrease of α-secretase activity, a disintegrin and metalloprotease domain 10 (ADAM10), is responsible for the increase of Aß productions in AD patient's brain. Here, we observe that the activity of α-secretase ADAM10 and levels of Nmnat2 are significantly decreased, meanwhile there is a simultaneous elevation of Aß in Tg2576 mice. Over-expression of Nmnat2 increases the mRNA expression of α-secretase ADAM10 and its activity and inhibits Aß production in N2a/APPswe cells, which can be abolished by Compound C, an AMPK antagonist, suggesting that AMPK is involved in over-expression of Nmnat2 against Aß production. The further assays demonstrate that Nmnat2 activates AMPK by up-regulating the ratio of NAD+/NADH, moreover AMPK agonist AICAR can also increase ADAM10 activity and reduces Aß1-40/1-42. Taken together, Nmnat2 suppresses Aß production and up-regulates ADAM10 in AMPK activity-dependent manner, suggesting that Nmnat2 may serve as a new potential target in arresting AD.

AMPK Ameliorates Tau Acetylation and Memory Impairment Through Sirt1.

Alzheimer's disease (AD) is the most common neurodegenerative disease, but its underlying mechanism is still unclear and the identities of drugs for AD also lack. Tau acetylation has become potentially important post-translational modification of tau. Levels of tau acetylation are significantly enhanced in AD patients and transgenic mouse models of AD, but the underlying mechanism and roles of tau hyperacetylation in AD onset maintain elusive. In the current study, we found that tau acetylation is obviously enhanced and the activities of AMP-activated protein kinase (AMPK) and sirtuin1 (Sirt1) are significantly decreased in APP/PS1 and streptozotocin (STZ) mice and high glucose (HG)-treated cells. Moreover, we demonstrated that activation of AMPK reduces the level of tau acetylation and ameliorates memory impairment, and its mechanism is associated with activation of Sirt1. Taken together, AMPK might be a crucial upstream molecular to regulate acetylation of tau and become a new target for AD therapy in the future.

The overexpression of RBM3 alleviates TBI-induced behaviour impairment and AD-like tauopathy in mice.

The therapeutic hypothermia is an effective tool for TBI-associated brain impairment, but its side effects limit in clinical routine use. Hypothermia up-regulates RNA-binding motif protein 3 (RBM3), which is verified to protect synaptic plasticity. Here, we found that cognitive and LTP deficits, loss of spines, AD-like tau pathologies are displayed one month after TBI in mice. In contrast, the deficits of LTP and cognitive, loss of spines and tau abnormal phosphorylation at several sites are obviously reversed in TBI mice combined with hypothermia pre-treatment (HT). But, the neuroprotective role of HT disappears in TBI mouse models under condition of blocking RBM3 expression with RBM3 shRNA. In other hand, overexpressing RBM3 by AAV-RBM3 plasmid can mimic HT-like neuroprotection against TBI-induced chronic brain injuries, such as improving LTP and cognitive, loss of spines and tau hyperphosphorylation in TBI mouse models. Taken together, hypothermia pre-treatment reverses TBI-induced chronic AD-like pathology and behaviour deficits in RBM3 expression dependent manner, RBM3 may be a potential target for neurodegeneration diseases including Alzheimer disease.

Upregulation of AMPK Ameliorates Alzheimer's Disease-Like Tau Pathology and Memory Impairment.

The studies have shown that 5'-adenosine monophosphate (AMP)-activated protein kinase (AMPK) is involved in Alzheimer's disease (AD) pathology, but the effects of AMPK on AD-like Tau abnormal phosphorylation and its underlying mechanism remains unclear. Herein, we found that the mRNA expression and activity of AMPK are significantly decreased in the brains of the aging C57 mice and 3 × Tg AD mice when compared with their respective control. Moreover, when downregulation of AMPK with AAV-siAMPK-eGFP in the hippocampus CA3 of 3-month-old C57 mice, the mice display AD-like Tau hyperphosphorylation, fear memory impairment, and glycogen synthase kinase-3ß (GSK3ß) activity increased. On the other hand, there are also AD-like Tau hyperphosphorylation, impairment of fear memory, and AMPK activity decreased in streptozotocin (STZ) mice. Interestingly, AMPK overexpression could efficiently rescue AD-like Tau phosphorylation and brain impairment in STZ mice. Moreover, the activity of GSK3ß and the level of Tau phosphorylation (Ser396 and Thr231 sites) were significantly decreased in HEK293 Tau cells transfected by AMPK plasmid or treated with agonists salicylate (SS), but GSK3ß agonists Wortmannin (Wort) could ablate AMPK-mediated Tau dephosphorylation. Taken together, the study indicated that AMPK reduces Tau phosphorylation and improves brain function and inhibits GSK3ß in AD-like model. These findings proved that AMPK might be a new target for AD in the future.

Inhibition of mTORC1 improves STZ-induced AD-like impairments in mice.

Alzheimer's disease (AD) and type 2 diabetes mellitus (T2DM) share some pathological features, including tau hyperphosphorylation and deficits in insulin signaling, but the underlying mechanism and effective drugs for treating AD are unknown. The AD-like brain impairments are almost same in both of mouse type 2 DM models induced by the multiple low-dose intraperitoneal (i.p.) streptozotocin (STZ) injection and twice intracerebroventricular (i.c.v.) STZ injection. We found that memory disorders, impairment of insulin signaling, and AD-like tauopathies were exhibited in two different STZ-induced mouse models and that the level of Advanced Glycation End Products (AGEs) was increased in two STZ mouse models. Inhibition of mTORC1 with rapamycin reversed the deficits of insulin signaling associated kinases activity, decreased levels of AGEs and AD-like tau phosphorylation, and also improved memory deficit in both STZ mice. Rapamycin attenuated HG-induced tau hyperphosphorylation via the AKT/AMPK/GSK-3ß pathways and p70S6K in SH-SY5Y cells. Taken together, these data demonstrated that rapamycin improved STZ-induced AD-like tauopathies and memory deficit in mice via improving p70S6K and AKT/AMPK/GSK-3ß signaling and decreasing AGEs. Therefore, regulating insulin signaling via mTORC1 is a new strategy for preventing T2DM-associated AD, and mTORC1 is a potential drug target.

The Down-Expression of ACE and IDE Exacerbates Exogenous Amyloid-ß Neurotoxicity in CB2R-/- Mice.

Alzheimer's disease (AD) is characterized by neuritic plaques and neurofibrillary tangles. It is reported that enzymatic degradation of amyloid-ß (Aß) plays a pivotal role in Aß accumulation and type-2 cannabinoid receptor (CB2R) participates in Aß processing in the brain; however, the underlying mechanisms remain unclear. We determined that Aß degradation-related proteins are significantly different between CB2R-/- mice and wild-type (WT) mice via proteomic analysis. Moreover, the data demonstrated that the angiotensin converting enzyme (ACE) and insulin-degrading enzyme (IDE) levels are substantially attenuated, and the Aß level is significantly enhanced in CB2R-/--Aß1 - 42 mice compared with that of WT-Aß1 - 42 mice. Furthermore, Aß-mediated synaptic dysfunction, the loss of memory associated proteins, and the suppression of glutamatergic transmission are more severe in CB2R-/--Aß1 - 42 mice than that in WT-Aß1 - 42 mice. CB2R activation could decrease Aß1 - 40 and Aß1 - 42 levels and enhance ACE and IDE levels with its selective agonist JWH133; however, AM630 (CB2R antagonist) abrogates all changes induced by JWH133 in N2a cells with AßPP overexpression. Taken together, our study demonstrated that the deletion of CB2R reduces exogenous Aß degradation and aggravates the toxicity of Aß via the reduction of ACE and IDE, which suggests that CB2R is involved in the onset of AD and a potential therapeutic target for AD.

Deletion of Type-2 Cannabinoid Receptor Induces Alzheimer's Disease-Like Tau Pathology and Memory Impairment Through AMPK/GSK3ß Pathway.

Although several studies have shown that type-2 cannabinoid receptor (CB2R) is involved in Alzheimer's disease (AD) pathology, the effects of CB2R on AD-like tau abnormal phosphorylation and its underlying mechanism remain unclear. Herein, we employed the CB2R-/- mice as the animal model to explore roles of CB2R in regulating tau phosphorylation and brain function. We found that CB2R-/- mice display AD-like tau hyperphosphorylation, hippocampus-dependent memory impairment, increase of GSK3ß activity, decrease of AMPK and Sirt1 activity and mitochondria dysfunction. Interestingly, AICAR or resveratrol (AMPK agonist) could efficiently rescue most alternations caused by solo deletion of CB2R in CB2R-/- mice. Moreover, JWH133, a selective agonist of CB2R, reduces phosphorylation of tau and GSK3ß activity in HEK293 tau cells, but the effects of JWH133 on phosphorylation of tau and GSK3ß disappeared while blocking AMPK activity with compound C or Prkaa2-RNAi. Taken together, our study indicated that deletion of CB2R induces behavior damage and AD-like pathological alternation via AMPK/GSK3ß pathway. These findings proved that CB2R/AMPK/GSK3ß pathway can be a promising new drug target for AD.

Hypothermia pretreatment improves cognitive impairment via enhancing synaptic plasticity in a traumatic brain injury model.

Posttraumatic hypothermia attenuates cognitive deficits caused by TBI when it is administered at an early stage. However, little is known regarding the effect of hypothermia pretreatment on cognitive deficits one month after TBI. In the current study, the behavior test revealed that hypothermia pretreatment mitigates the learning and memory impairment induced by TBI in mice. Hypothermia treatment significantly increased the expression of PSD93, PSD95 and NR2B one month after TBI in the cortex and hippocampus compared with the normothermia group. Hypothermia pretreatment also restored the decreased spine number and the impairment in LTP and decreased the number of activated microglia one month after TBI. On the other hand, hypothermia pretreatment increased glucose metabolism in TBI mice. Taken together, these data suggested that hypothermia pretreatment is an effective method with which to prevent spine loss, maintain normal LTP and preserve learning and memory function after TBI. The neuroprotective role might be associated with the preservation of postsynaptic protein expression, the inhibition of activated microglia and the increase in glucose metabolism.