Tau-Induced Ca2+/Calmodulin-Dependent Protein Kinase-IV Activation Aggravates Nuclear Tau Hyperphosphorylation

CaMK modulates sensory neural activity to control longevity and proteostasis

The impact of neural activity on aging and longevity remains poorly understood, with limited understanding of the specific neuron groups and molecular mechanisms that regulate lifespan. In this study, we uncover a correlation between human longevity and reduced CaMK4 expression in the frontal cortex. We further show that this link is conserved in Caenorhabditis elegans, where the loss of the homolog CMK-1 leads to increased longevity and enhanced proteostasis. These beneficial effects are primarily driven by suppressed excitation in the primary thermosensory AFD neurons, particularly at elevated temperatures that trigger hyperactivation. In the thermosensory neural circuit, suppression of AFD neuron activity promotes the release of INS-1/insulin from AIZ, which in turn activates DAF-16/FOXO in the intestine. Our findings reveal a causal mechanism through which sensory neural activity governs lifespan and organismal proteostasis, highlighting the significance of CaMK in shaping these processes through the regulation of neural activity.

The interaction between dysfunction of vasculature and tauopathy in Alzheimer's disease and related dementias

Tauopathy is one of the pathological features of Alzheimer's disease and related dementias (ADRD). At present, there have been many studies on the formation, deposition, and intercellular transmission of tau in neurons and immune cells. The vasculature is an important component of the central nervous system. This review discusses the interaction between vasculature and tau in detail from three aspects. (1) The vascular risk factors (VRFs) discussed in this review include diabetes mellitus (DM), abnormal blood pressure (BP), and hypercholesterolemia. (2) In ADRD pathology, the hyperphosphorylation and deposition of tau interact with disrupted vasculature, such as different cells (endothelial cells, smooth muscular cells, and pericytes), the blood-brain barrier (BBB), and the cerebral lymphatic system. (3) The functions of vasculature are regulated by various signaling transductions. Endothelial nitric oxide synthase/nitric oxide, calcium signaling, Rho/Rho-associated coiled-coil containing Kinase, and receptors for advanced glycation end products are discussed in this review. Our findings indicate that the prevention and treatment of vascular health may be a potential target for ADRD combination therapy. HIGHLIGHTS: Persistent VRFs increase early disruption of vascular mechanisms and are strongly associated with tau pathology in ADRD. Cell dysfunction in the vasculature causes BBB leakage and drainage incapacity of the cerebral lymphatic system, which interacts with tau pathology. Signaling molecules in the vasculature regulate vasodilation and contraction, angiogenesis, and CBF. Abnormal signaling transduction is related to tau hyperphosphorylation and deposition.

Proximity labeling of the Tau repeat domain enriches RNA-binding proteins that are altered in Alzheimer's disease and related tauopathies

In Alzheimer's disease (AD) and other tauopathies, tau dissociates from microtubules and forms toxic aggregates that contribute to neurodegeneration. Although some of the pathological interactions of tau have been identified from postmortem brain tissue, these studies are limited by their inability to capture transient interactions. To investigate the interactome of aggregate-prone fragments of tau, we applied an in vitro proximity labeling technique using split TurboID biotin ligase (sTurbo) fused with the tau microtubule repeat domain (TauRD), a core region implicated in tau aggregation. We characterized sTurbo TauRD co-expression, robust enzyme activity and nuclear and cytoplasmic localization in a human cell line. Following enrichment of biotinylated proteins and mass spectrometry, we identified over 700 TauRD interactors. Gene ontology analysis of enriched TauRD interactors highlighted processes often dysregulated in tauopathies, including spliceosome complexes, RNA-binding proteins (RBPs), and nuclear speckles. The disease relevance of these interactors was supported by integrating recombinant TauRD interactome data with human AD tau interactome datasets and protein co-expression networks from individuals with AD and related tauopathies. This revealed an overlap with the TauRD interactome and several modules enriched with RBPs and increased in AD and Progressive Supranuclear Palsy (PSP). These findings emphasize the importance of nuclear pathways in tau pathology, such as RNA splicing and nuclear-cytoplasmic transport and establish the sTurbo TauRD system as a valuable tool for exploring the tau interactome.

Calcium signaling hypothesis: A non-negligible pathogenesis in Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) presents a significant challenge to global healthcare systems, with an exacerbation by an aging population. Although the plethora of hypotheses are proposed to elucidate the underlying mechanisms of AD, from amyloid-beta (Aβ) accumulation and Tau protein aggregation to neuroinflammation, a comprehensive understanding of its pathogenesis remains elusive. Recent research has highlighted the critical role of calcium (Ca2+) signaling pathway in the progression of AD, indicating a complex interplay between Ca2+ dysregulation and various pathological processes.

AIM OF REVIEW

This review aims to consolidate the current understanding of the role of Ca2+ signaling dysregulation in AD, thus emphasizing its central role amidst various pathological hypotheses. We aim to evaluate the potential of the Ca2+ signaling hypothesis to unify existing theories of AD pathogenesis and explore its implications for developing innovative therapeutic strategies through targeting Ca2+ dysregulation.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The review focuses on three principal concepts. First, the indispensable role of Ca2+ homeostasis in neuronal function and its disruption in AD. Second, the interaction between Ca2+ signaling dysfunction and established AD hypotheses posited that Ca2+ dysregulation is a unifying pathway. Third, the dual role of Ca2+ in neurodegeneration and neuroprotection, highlighting the nuanced effects of Ca2+ levels on AD pathology.

Novel cuproptosis metabolism-related molecular clusters and diagnostic signature for Alzheimer's disease

Background

Alzheimer's disease (AD) is a progressive neurodegenerative disorder with no effective treatments available. There is growing evidence that cuproptosis contributes to the pathogenesis of this disease. This study developed a novel molecular clustering based on cuproptosis-related genes and constructed a signature for AD patients.

Methods

The differentially expressed cuproptosis-related genes (DECRGs) were identified using the DESeq2 R package. The GSEA, PPI network, GO, KEGG, and correlation analysis were conducted to explore the biological functions of DECRGs. Molecular clusters were performed using unsupervised cluster analysis. Differences in biological processes between clusters were evaluated by GSVA and immune infiltration analysis. The optimal model was constructed by WGCNA and machine learning techniques. Decision curve analysis, calibration curves, receiver operating characteristic (ROC) curves, and two additional datasets were employed to confirm the prediction results. Finally, immunofluorescence (IF) staining in AD mice models was used to verify the expression levels of risk genes.

Results

GSEA and CIBERSORT showed higher levels of resting NK cells, M2 macrophages, naïve CD4+ T cells, neutrophils, monocytes, and plasma cells in AD samples compared to controls. We classified 310 AD patients into two molecular clusters with distinct expression profiles and different immunological characteristics. The C1 subtype showed higher abundance of cuproptosis-related genes, with higher proportions of regulatory T cells, CD8+T cells, and resting dendritic cells. We subsequently constructed a diagnostic model which was confirmed by nomogram, calibration, and decision curve analysis. The values of area under the curves (AUC) were 0.738 and 0.931 for the external datasets, respectively. The expression levels of risk genes were further validated in mouse brain samples.

Conclusion

Our study provided potential targets for AD treatment, developed a promising gene signature, and offered novel insights for exploring the pathogenesis of AD.

Expression of ITPR2 regulated by lncRNA-NONMMUT020270.2 in LPS-stimulated HT22 cells

Background

Long non-coding RNA (lncRNA)-NONMMUT020270.2 is downregulated and co-expressed with inositol 1,4,5-trisphosphate receptor type 2 (ITPR2) in the hippocampus of Alzheimer's disease (AD) mice. However, whether the expression of ITPR2 was regulated by lncRNA-NONMMUT020270.2 remains unclear. we aimed to investigate regulating relationship of lncRNA-NONMMUT020270.2 and ITPR2.

Methods

HT22 cells were firstly transfected with the pcDNA3.1-lncRNA-NONMMUT020270.2 overexpression plasmid or with the lncRNA-NONMMUT020270.2 smart silencer, and then were stimulated with lipopolysaccharide (LPS) for 24h. The mRNA expression levels of lncRNA-NONMMUT020270.2 and ITPR2 were measured by reverse transcription-quantitative PCR. Cell viability was assessed using a Cell Counting Kit 8 assay. The expression of Aβ1-42 was detected by ELISA. The expression levels of p-tau, caspase-1, and inositol trisphosphate receptor (IP3R) proteins were detected by western-blotting. Nuclear morphological changes were detected by Hoechst staining. Flow cytometry and Fluo-3/AM were carried out to determine cell apoptosis and the intracellular Ca2+.

Results

LPS significantly decreased cell viability, and ITPR2 mRNA and IP3R protein expression levels. While it markedly enhanced the expression levels of p-tau and Aβ1-42, cell apoptosis rate, as well as intracellular Ca2+ concentration (P < 0.05). In addition, lncRNA-NONMMUT020270.2 overexpression significantly increased the expressions levels of ITPR2 mRNA and IP3R protein (P < 0.05), and inhibited expression of p-tau and Aβ1-42, cell apoptosis rate, and reduced intracellular Ca2+ concentration (P < 0.05). By contrast, lncRNA-NONMMUT020270.2 silencing notably downregulated expressions levels of ITPR2 mRNA and IP3R protein (P < 0.05), and elevated expression levels of p-tau and Aβ1-42, cell apoptosis rate, and intracellular Ca2+ concentration (P < 0.05).

Conclusion

lncRNA-NONMMUT020270.2 was positively correlated with ITPR2 expression in LPS-induced cell. Downregulating the lncRNA-NONMMUT020270.2 and ITPR2 may promote cell apoptosis and increase intracellular Ca2+ concentration.

Nuclear face of Tau: an inside player in neurodegeneration

Tau (Tubulin associated unit) protein is a major hallmark of Alzheimer's disease (AD) and tauopathies. Tau is predominantly an axonal protein with a crucial role in the stabilization and dynamics of the microtubules. Since the discovery of Tau protein in 1975, research efforts were concentrated on the pathophysiological role of Tau protein in the context of the microtubules. Although, for more than three decades, different localizations of Tau protein have been discovered e.g., in the nuclear compartments. Discovery of the role of Tau protein in various cellular compartments especially in the nucleus opens up a new fold of complexity in tauopathies. Data from cellular models, animal models, and the human brain indicate that nuclear Tau is crucial for genome stability and to cope with cellular distress. Moreover, it's nature of nuclear translocation, its interactions with the nuclear DNA/RNA and proteins suggest it could play multiple roles in the nucleus. To comprehend Tau pathophysiology and efficient Tau-based therapies, there is an urgent need to understand whole repertoire of Tau species (nuclear and cytoplasmic) and their functional relevance. To complete the map of Tau repertoire, understanding of various species of Tau in the nucleus and cytoplasm, identification if specific transcripts of Tau, isoforms and post-translational modifications could foretell Tau's localizations and functions, and how they are modified in neurodegenerative diseases like AD, is urgently required. In this review, we explore the nuclear face of Tau protein, its nuclear localizations and functions and its linkage with Alzheimer's disease.

A Comprehensive Review of the Effects of Glycemic Carbohydrates on the Neurocognitive Functions Based on Gut Microenvironment Regulation and Glycemic Fluctuation Control

Improper glycemic carbohydrates (GCs) consumption can be a potential risk factor for metabolic diseases such as obesity and diabetes, which may lead to cognitive impairment. Although several potential mechanisms have been studied, the biological relationship between carbohydrate consumption and neurocognitive impairment is still uncertain. In this review, the main effects and mechanisms of GCs' digestive characteristics on cognitive functions are comprehensively elucidated. Additionally, healthier carbohydrate selection, a reliable research model, and future directions are discussed. Individuals in their early and late lives and patients with metabolic diseases are highly susceptible to dietary-induced cognitive impairment. It is well known that gut function is closely related to dietary patterns. Unhealthy carbohydrate diet-induced gut microenvironment disorders negatively impact cognitive functions through the gut-brain axis. Moreover, severe glycemic fluctuations, due to rapidly digestible carbohydrate consumption or metabolic diseases, can impair neurocognitive functions by disrupting glucose metabolism, dysregulating calcium homeostasis, oxidative stress, inflammatory responses, and accumulating advanced glycation end products. Unstable glycemic status can lead to more severe neurological impairment than persistent hyperglycemia. Slow-digested or resistant carbohydrates might contribute to better neurocognitive functions due to stable glycemic response and healthier gut functions than fully gelatinized starch and nutritive sugars.

TRPV1 Modulator Ameliorates Alzheimer-Like Amyloid-β Neuropathology via Akt/Gsk3β-Mediated Nrf2 Activation in the Neuro-2a/APP Cell Model

Alzheimer's disease (AD) is a progressive and irreversible neurodegenerative disorder for which there is no effective therapeutic strategy. PcActx peptide from the transcriptome of zoantharian Palythoa caribaeorum has recently been identified and verified as a novel antagonist of transient receptor potential cation channel subfamily V member 1 (TRPV1). In the present study, we further investigated the neuroprotective potential of PcActx peptide and its underlying mechanism of action, in an N2a/APP cell model of AD. Both Western blot and RT-PCR analysis revealed that PcActx peptide markedly inhibited the production of amyloid-related proteins and the expression of BACE1, PSEN1, and PSEN2. Moreover, PcActx peptide notably attenuated the capsaicin-stimulated calcium response and prevented the phosphorylation of CaMKII and CaMKIV (calcium-mediated proteins) in N2a/APP cells. Further investigation indicated that PcActx peptide significantly suppressed ROS generation through Nrf2 activation, followed by enhanced NQO1 and HO-1 levels. In addition, PcActx peptide remarkably improved Akt phosphorylation at Ser 473 (active) and Gsk3β phosphorylation at Ser 9 (inactive), while pharmacological inhibition of the Akt/Gsk3β pathway significantly attenuated PcActx-induced Nrf2 activation and amyloid downregulation. In conclusion, PcActx peptide functions as a TRPV1 modulator of intercellular calcium homeostasis, prevents AD-like amyloid neuropathology via Akt/Gsk3β-mediated Nrf2 activation, and shows promise as an alternative therapeutic agent for AD.

Dihydroartemisinin Induces O-GlcNAcylation and Improves Cognitive Function in a Mouse Model of Tauopathy

BACKGROUND

Tauopathies are a group of neurodegenerative disorders, including Alzheimer's disease (AD) and frontotemporal lobar degeneration with tau pathology. Hyperphosphorylation modification promotes tau protein misfolding and aggregation into neurofibrillary tangles, leading to impairments of synaptic plasticity and learning and memory. However, very limited therapeutic strategies are available.

OBJECTIVE

In the present study, we wanted to investigate the potential effects of Dihydroartemisinin (DHA) on tauopathies.

METHODS

We constructed adeno-associated virus carrying hTau cDNA (AAVhTau) to establish a mouse model of tauopathy through intrahippocampal microinjection. Using a combination of behavioral test, electrophysiological recording, and western blotting assay, we examined the neuroprotective effects of DHA on learning and memory deficits in mice with tauopathy.

RESULTS

DHA improved learning and memory and increased hippocampal CA1 long-term potentiation (LTP) in mice overexpressed human tau (hTau) in the hippocampus. More importantly, further study revealed that DHA could induce protein O-GlcNAcylation modification and reduce protein phosphorylation. O-GlcNAc transferase inhibitor alloxan could suppress DHA-induced protein O-GlcNAcylation, and subsequently prevent therapeutic effect of DHA on the deficits of learning and memory as well as synaptic plasticity in hTau mice.

CONCLUSION

These results indicate that DHA may exert neuroprotective role in tauopathy through a crosstalk between O-GlcNAcylation and phosphorylation, suggesting a potential therapeutic for learning and memory deficits associated with tau pathology.

Tau Acetylation in Entorhinal Cortex Induces its Chronic Hippocampal Propagation and Cognitive Deficits in Mice

BACKGROUND

Increased tau acetylation at K174, K274, K280, and K281 has been observed in the brains of Alzheimer's disease (AD) patients or in transgenic mice, but the role of acetylation in tau propagation is elusive.

OBJECTIVE

To study the effect of tau acetylation in entorhinal cortex on tau transmission and learning and memory.

METHODS

Stereotactic brain injection, behavioral test, electrophysiological recording, immunohistochemistry, and immunofluorescence were used.

RESULTS

We constructed the hyperacetylation mimics of tau (AAV-Tau-4Q), the non-acetylation tau mutant (AAV-Tau-4R), and the wild-type tau (AAV-Tau-WT). By overexpressing these different tau proteins in the entorhinal cortex (EC) of 2-month-old mice, we found that overexpressing Tau-4Q in EC for 3 or 6 months (to 5 or 8 months of age) neither induces tau propagation to dentate gyrus (DG) nor glial activation in DG, nor spatial memory deficit. However, overexpressing Tau-WT and Tau-4Q in EC for 13.5 months (15.5 months of age) at 2 months promoted tau propagation respectively to granulosa and hilus of DG with glial activation, synaptic dysfunction, and memory deficit, while overexpressing Tau-4R abolished tau propagation with improved cellular pathologies and cognitive functions. Furthermore, overexpressing Tau-4Q in unilateral DG of 2-month-old mice for 8 weeks also promoted its contralateral transmission with glial activation, and mice with tau (Tau-WT, Tau-4Q, and Tau-4R) overexpression in DG showed cognitive deficits compared with the empty vector controls.

CONCLUSION

Tau acetylation induces a time-dependent propagation from EC to DG, and only hippocampus but not EC tau accumulation induces cognitive deficits.

Cytoskeletal Arrest: An Anoxia Tolerance Mechanism

Polymerization of actin filaments and microtubules constitutes a ubiquitous demand for cellular adenosine-5′-triphosphate (ATP) and guanosine-5′-triphosphate (GTP). In anoxia-tolerant animals, ATP consumption is minimized during overwintering conditions, but little is known about the role of cell structure in anoxia tolerance. Studies of overwintering mammals have revealed that microtubule stability in neurites is reduced at low temperature, resulting in withdrawal of neurites and reduced abundance of excitatory synapses. Literature for turtles is consistent with a similar downregulation of peripheral cytoskeletal activity in brain and liver during anoxic overwintering. Downregulation of actin dynamics, as well as modification to microtubule organization, may play vital roles in facilitating anoxia tolerance. Mitochondrial calcium release occurs during anoxia in turtle neurons, and subsequent activation of calcium-binding proteins likely regulates cytoskeletal stability. Production of reactive oxygen species (ROS) formation can lead to catastrophic cytoskeletal damage during overwintering and ROS production can be regulated by the dynamics of mitochondrial interconnectivity. Therefore, suppression of ROS formation is likely an important aspect of cytoskeletal arrest. Furthermore, gasotransmitters can regulate ROS levels, as well as cytoskeletal contractility and rearrangement. In this review we will explore the energetic costs of cytoskeletal activity, the cellular mechanisms regulating it, and the potential for cytoskeletal arrest being an important mechanism permitting long-term anoxia survival in anoxia-tolerant species, such as the western painted turtle and goldfish.

Xestospongin C, a Reversible IP3 Receptor Antagonist, Alleviates the Cognitive and Pathological Impairments in APP/PS1 Mice of Alzheimer's Disease

Exaggerated Ca2+ signaling might be one of primary causes of neural dysfunction in Alzheimer's disease (AD). And the intracellular Ca2+ overload has been closely associated with amyloid-β (Aβ)-induced endoplasmic reticulum (ER) stress and memory impairments in AD. Here we showed for the first time the neuroprotective effects of Xestospongin C (XeC), a reversible IP3 receptor antagonist, on the cognitive behaviors and pathology of APP/PS1 AD mice. Male APP/PS1-AD mice (n = 20) were injected intracerebroventricularly with XeC (3μmol) via Alzet osmotic pumps for four weeks, followed by cognition tests, Aβ plaque examination, and ER stress-related protein measurement. The results showed that XeC pretreatment significantly improved the cognitive behavior of APP/PS1-AD mice, raising the spontaneous alteration accuracy in Y maze, decreasing the escape latency and increasing the target quadrant swimming time in Morris water maze; XeC pretreatment also reduced the number of Aβ plaques and the overexpression of ER stress proteins 78 kDa glucose-regulated protein (GRP-78), caspase-12, and CAAT/enhancer-binding protein (C/EBP) homologous protein (CHOP) in the hippocampus of APP/PS1 mice. In addition, in vitro experiments showed that XeC effectively ameliorated Aβ1 - 42-induced early neuronal apoptosis and intracellular Ca2+ overload in the primary hippocampal neurons. Taken together, IP3R-mediated Ca2+ disorder plays a key role in the cognitive deficits and pathological damages in AD mice. By targeting the IP3 R, XeC might be considered as a novel therapeutic strategy in AD.

The Regulating Mechanism of Chrysophanol on Protein Level of CaM-CaMKIV to Protect PC12 Cells Against Aβ25-35-Induced Damage

Objective

To investigate the neuroprotective effect of chrysophanol (CHR) on PC12 treated with Aβ_25-35, and the involved mechanism.

Methods

After the establishment of an AD cell model induced by Aβ_25-35, the cell survival rate was detected by MTT, cell apoptosis was assayed by Hoechst 33342 staining, mRNA expressions of calmodulin (CaM), calcium/calmodulin-dependent protein kinase kinase (CaMKK), calcium/calmodulin-dependent protein kinase IV (CaMKIV) and tau (MAPT; commonly known as tau) were determined by qRT-PCR, and protein levels of CaM, CaMKK, CaMKIV, phospho-CaMKIV (p-CaMKIV), tau and phospho-tau (p-tau) were detected by Western blot analysis.

Results

When pretreated with CHR before exposure to Aβ_25-35, PC12 cells showed that increased cell viability and reduced apoptosis. The qRT-PCR results indicated that the deposition of Aβ_25-35 triggers a decrease in levels of CaM, CaMKK, CaMKIV, and tau in PC12 cells. In addition, Western blot results also suggested that Aβ_25-35 decreases the protein expression of CaM, CaMKK, CaMKIV, p-CaMKIV, and the ratio of p-tau to tau in PC12 cells. However, the above effects were significantly alleviated after the treatment of CHR.

Conclusion

CHR plays a neuroprotective role in AD though decreasing the protein level of CaM-CaMKK-CaMKIV and the expression of p-tau downstream.

Tolfenamic acid inhibits GSK-3β and PP2A mediated tau hyperphosphorylation in Alzheimer's disease models

Tolfenamic acid, a nonsteroidal anti-inflammatory drug, alleviated learning and memory deficits and decreased the expression of specificity protein 1 (SP1)-mediated cyclin-dependent kinase-5 (CDK5), a major protein kinase that regulates hyperphosphorylated tau, in Alzheimer's disease (AD) transgenic mice. However, whether tolfenamic acid can regulate the major tau protein kinase, glycogen synthase kinase-3β (GSK-3β), or tau protein phosphatase, protein phosphatase 2A (PP2A), further inhibiting hyperphosphorylation of tau, remains unknown. To this end, tolfenamic acid was administered i.p. in a GSK-3β overactivation postnatal rat model and orally in mice after intracerebroventricular (ICV) injection of okadaic acid (OA) to develop a PP2A inhibition model. We used four behavioural experiments to evaluate memory function in ICV-OA mice. In this study, tolfenamic acid attenuated memory dysfunction. Tolfenamic acid decreased the expression of hyperphosphorylated tau in the brain by inhibiting GSK-3β activity, decreasing phosphorylated PP2A (Tyr307), and enhancing PP2A activity. Tolfenamic acid also increased wortmannin (WT) and GF-109203X (GFX) induced phosphorylation of GSK-3β (Ser9) and prevented OA-induced downregulation of PP2A activity in PC12 cells. Altogether, these results show that tolfenamic acid not only decreased SP1/CDK5-mediated tau phosphorylation, but also inhibited GSK-3β and PP2A-mediated tau hyperphosphorylation in AD models.

Overexpression of Purinergic P2X4 Receptors in Hippocampus Rescues Memory Impairment in Rats with Type 2 Diabetes

Purinergic receptors have been reported to be involved in brain disorders. In this study, we explored their roles and mechanisms underlying the memory impairment in rats with type 2 diabetes mellitus (T2DM). T2DM rats exhibited a worse performance in the T-maze and Morris water maze (MWM) than controls. Microglia positive for P2X purinoceptor 4 (P2X4R) in the hippocampus were reduced and activated microglia were increased in T2DM rats. Long Amplicon PCR (LA-PCR) showed that DNA amplification of the p2x4r gene in the hippocampus was lower in T2DM rats. Minocycline significantly reduced the number of activated microglia and the mean distance traveled by T2DM rats in the MWM. Most importantly, P2X4R overexpression suppressed the activated microglia and rescued the memory impairment of T2DM rats. Overall, T2DM led to excessive activation of microglia in the hippocampus, partly through the DNA damage-mediated downregulation of P2X4Rs, thus contributing to memory impairment.

Interneuron Accumulation of Phosphorylated tau Impairs Adult Hippocampal Neurogenesis by Suppressing GABAergic Transmission

Phospho-tau accumulation and adult hippocampal neurogenesis (AHN) impairment both contribute importantly to the cognitive decline in Alzheimer's disease (AD), but whether and how tau dysregulates AHN in AD remain poorly understood. Here, we found a prominent accumulation of phosphorylated tau in GABAergic interneurons in the dentate gyrus (DG) of AD patients and mice. Specific overexpression of human tau (hTau) in mice DG interneurons induced AHN deficits but increased neural stem cell-derived astrogliosis, associating with a downregulation of GABA and hyperactivation of neighboring excitatory neurons. Chemogenetic inhibition of excitatory neurons or pharmacologically strengthening GABAergic tempos rescued the tau-induced AHN deficits and improved contextual cognition. These findings evidenced that intracellular accumulation of tau in GABAergic interneurons impairs AHN by suppressing GABAergic transmission and disinhibiting neural circuits within the neurogenic niche, suggesting a potential of GABAergic potentiators for pro-neurogenic or cell therapies of AD.

Regulation of Multifunctional Calcium/Calmodulin Stimulated Protein Kinases by Molecular Targeting

Multifunctional calcium/calmodulin-stimulated protein kinases control a broad range of cellular functions in a multitude of cell types. This family of kinases contain several structural similarities and all are regulated by phosphorylation, which either activates, inhibits or modulates their kinase activity. As these protein kinases are widely or ubiquitously expressed, and yet regulate a broad range of different cellular functions, additional levels of regulation exist that control these cell-specific functions. Of particular importance for this specificity of function for multifunctional kinases is the expression of specific binding proteins that mediate molecular targeting. These molecular targeting mechanisms allow pools of kinase in different cells, or parts of a cell, to respond differently to activation and produce different functional outcomes.

Effect of Apolipoprotein E Genotypes on Huntington's Disease Phenotypes in a Han Chinese Population

Huntington's disease (HD) is an autosomal dominant degenerative disease that mainly encompasses movement, cognition, and behavioral symptoms. The apolipoprotein E (APOE) gene is thought to be associated with many neurodegenerative diseases. Here, we enrolled a cohort of 223 unrelated Han Chinese patients with HD and 1241 unrelated healthy controls in Southeastern China and analyzed the correlation between APOE genotypes and HD phenotypes. The results showed that the frequency of the E4 allele (7.1%) in HD patients was statistically less than that in controls (12.0%) (P =0.004). In addition, we divided patients into motor-onset and non-motor-onset groups, and analyzed the relationship with APOE genotypes. The results, however, were negative. Furthermore, the age at onset (AAO), defined as the age at the onset of motor symptoms, was compared in each APOE genotype subgroup and multivariate regression analysis was used to exclude the interference of CAG repeat length on AAO, but no association was found between APOE genotypes and AAO. Finally, we analyzed adult-onset HD to exclude the interference caused by juvenile HD (n = 13), and the results were negative. Therefore, our study suggests that APOE may not be a genetic modifier for HD, especially for adult-onset HD among Chinese of Han ethnicity. To the best of our knowledge, this is the first study of the correlation between APOE genotypes and HD phenotypes in a Han Chinese population.

Nature of Tau-Associated Neurodegeneration and the Molecular Mechanisms

Neurodegeneration is defined as the progressive loss of structure or function of the neurons. As the nature of degenerative cell loss is currently not clear, there is no specific molecular marker to measure neurodegeneration. Therefore, researchers have been using apoptotic markers to measure neurodegeneration. However, neurodegeneration is completely different from apoptosis by morphology and time course. Lacking specific molecular marker has been the major hindrance in research of neurodegenerative disorders. Alzheimer's disease (AD) is the most common neurodegenerative disorder, and tau accumulation forming neurofibrillary tangles is a hallmark pathology in the AD brains, suggesting that tau must play a critical role in AD neurodegeneration. Here we review part of our published papers on tau-related studies, and share our thoughts on the nature of tau-associated neurodegeneration in AD.

Calcium-Binding Proteins in the Nervous System during Hibernation: Neuroprotective Strategies in Hypometabolic Conditions?

Calcium-binding proteins (CBPs) can influence and react to Ca2+ transients and modulate the activity of proteins involved in both maintaining homeostatic conditions and protecting cells in harsh environmental conditions. Hibernation is a strategy that evolved in vertebrate and invertebrate species to survive in cold environments; it relies on molecular, cellular, and behavioral adaptations guided by the neuroendocrine system that together ensure unmatched tolerance to hypothermia, hypometabolism, and hypoxia. Therefore, hibernation is a useful model to study molecular neuroprotective adaptations to extreme conditions, and can reveal useful applications to human pathological conditions. In this review, we describe the known changes in Ca2+-signaling and the detection and activity of CBPs in the nervous system of vertebrate and invertebrate models during hibernation, focusing on cytosolic Ca2+ buffers and calmodulin. Then, we discuss these findings in the context of the neuroprotective and neural plasticity mechanisms in the central nervous system: in particular, those associated with cytoskeletal proteins. Finally, we compare the expression of CBPs in the hibernating nervous system with two different conditions of neurodegeneration, i.e., platinum-induced neurotoxicity and Alzheimer's disease, to highlight the similarities and differences and demonstrate the potential of hibernation to shed light into part of the molecular mechanisms behind neurodegenerative diseases.

RNA Interference Screening Reveals Host CaMK4 as a Regulator of Cryptococcal Uptake and Pathogenesis

Cryptococcus neoformans, the causative agent of cryptococcosis, is an opportunistic fungal pathogen that kills over 200,000 individuals annually. This yeast may grow freely in body fluids, but it also flourishes within host cells. Despite extensive research on cryptococcal pathogenesis, host genes involved in the initial engulfment of fungi and subsequent stages of infection are woefully understudied. To address this issue, we combined short interfering RNA silencing and a high-throughput imaging assay to identify host regulators that specifically influence cryptococcal uptake. Of 868 phosphatase and kinase genes assayed, we discovered 79 whose silencing significantly affected cryptococcal engulfment. For 25 of these, the effects were fungus specific, as opposed to general alterations in phagocytosis. Four members of this group significantly and specifically altered cryptococcal uptake; one of them encoded CaMK4, a calcium/calmodulin-dependent protein kinase. Pharmacological inhibition of CaMK4 recapitulated the observed defects in phagocytosis. Furthermore, mice deficient in CaMK4 showed increased survival compared to wild-type mice upon infection with C. neoformans This increase in survival correlated with decreased expression of pattern recognition receptors on host phagocytes known to recognize C. neoformans Altogether, we have identified a kinase that is involved in C. neoformans internalization by host cells and in host resistance to this deadly infection.