Activation of D2-like dopamine receptors improves the neuronal network and cognitive function of PPT1KI mice.

Palmitoyl-protein thioesterase 1 (PPT1) is a lysosomal depalmitoylation enzyme that mediates protein posttranslational modifications. Loss-of-function mutation of PPT1 causes a failure of the lysosomal degradation of palmitoylated proteins and results in a congenital disease characterized by progressive neuronal degeneration referred to as infantile neuronal ceroid lipofuscinosis (INCL). A mouse knock-in model of PPT1 (PPT1-KI) was established by introducing the R151X mutation into exon 5 of the PPT1 gene, which exhibited INCL-like pathological lesions. We previously reported that hippocampal γ oscillations were impaired in PPT1 mice. Hippocampal γ oscillations can be enhanced by selective activation of the dopamine D4 receptor (DR4), a dopamine D2-like receptor. In this study, we investigated the changes in DR expression and the effects of dopamine and various DR agonists on neural network activity, cognition and motor function in PPT1KI mice. Cognition and motor defects were evaluated via Y-maze, novel object recognition and rotarod tests. Extracellular field potentials were elicited in hippocampal slices, and neuronal network oscillations in the gamma frequency band (γ oscillations) were induced by perfusion with kainic acid (200 nM). PPT1KI mice displayed progressive impairments in γ oscillations and hippocampus-related memory, as well as abnormal expression profiles of dopamine receptors with preserved expression of DR1 and 3, increased membrane expression of DR4 and decreased DR2 levels. The immunocytochemistry analysis revealed the colocalization of PPT1 with DR4 or DR2 in the soma and large dendrites of both WT and PPT1KI mice. Immunoprecipitation confirmed the interaction between PPT1 and DR4 or DR2. The impaired γ oscillations and cognitive functions were largely restored by the application of exogenous dopamine, the selective DR2 agonist quinpirole or the DR4 agonist A412997. Furthermore, the administration of A412997 (0.5 mg/kg, i.p.) significantly upregulated the activity of CaMKII in the hippocampus of 5-month-old PPT1KI mice. Collectively, these results suggest that the activation of D2-like dopamine receptors improves cognition and network activity in PPT1KI mice and that specific DR subunits may be potential targets for the intervention of neurodegenerative disorders, such as INCL.

Fluvoxamine prompts the antitumor immune effect via inhibiting the PD-L1 expression on mice-burdened colon tumor.

A colon tumor, one of the digestive tract malignant tumors, is harmful to human health. A potential new treatment still deserves attention. The development of a new drug needs more resources, including time and expense. Therefore, the old drug with new targets has become a current research hotspot. Fluvoxamine, as an antidepressant, could play an effect on inhibiting 5-hydroxytryptamine reuptake. In the present research, the antitumor effects and possible mechanisms of fluvoxamine are validated. The results showed that fluvoxamine significantly suppressed the migration and proliferation of tumor cells, and increased the apoptosis in vitro. Additionally, fluvoxamine significantly delays tumor development, and prompts the apoptosis in tumor tissues of mice-burdened colon tumors in vivo. The tumor suppression might be related with that fluvoxamine inhibits the expression of phosphorylated signal transducer and activator of transcription 3, matrix metalloproteinase 2, and cleaved-caspase 3. Importantly, fluvoxamine significantly reduces the expression level of programmed cell death ligand 1. This could be a possible reason that treatment with fluvoxamine drives the infiltration of T lymphocytes and M1-type macrophages in tumor tissues. Taken together, this research suggests that fluvoxamine might be a promising drug to treat colon cancer by inhibiting the proliferation and migration, inducing apoptosis, and even increasing the immune response of antitumor.

Seizures in PPT1 Knock-In Mice Are Associated with Inflammatory Activation of Microglia.

Infantile neuronal ceroid lipofuscinosis (INCL), the most severe form of neuronal ceroid lipofuscinoses, is caused by mutations in the lysosomal enzyme palmitoyl protein thioesterase 1 (PPT1). Typical symptoms of this disease include progressive psychomotor developmental retardation, visual failure, seizures, and premature death. Here, we investigated seizure activity and relevant pathological changes in PPT1 knock-in mice (PPT1 KI). The behavior studies in this study demonstrated that PPT1 KI mice had no significant seizure activity until 7 months of age, and local field potentials also displayed epileptiform activity at the same age. The expression levels of Iba-1 and CD68 demonstrated, by Western blot analysis, the inflammatory cytokine TNF-α content measured with enzyme-linked immunosorbent assay, and the number of microglia demonstrated by immunohistochemistry (IHC) were significantly increased at age of 7 months, all of which indicate microglia activation at an age of seizure onset. The increased expression of GFAP were seen at an earlier age of 4 months, and such an increase reached its peak at age of 6 months, indicating that astrocyte activation precedes microglia. The purinergic P2X7 receptor (P2X7R) is an ATP-sensitive ionic channel that is highly expressed in microglia and is fundamental to microglial activation, proliferation, cytokines release and epilepsy. We show that the ATP concentration in hippocampal tissue in PPT1 KI mice was increased using an enhanced ATP assay kit and demonstrated that the antagonist of P2X7R, A-438079, significantly reduced seizures in PPT1 KI mice. In contrast to glial cell activation and proliferation, a significant reduction in synaptic proteins GABAAR was seen in PPT1 KI mice. These results indicate that seizure in PPT1 KI mice may be associated with microglial activation involved in ATP-sensitive P2X7R signaling and impaired inhibitory neurotransmission.

The physiological modulation by intracellular kinases of hippocampal γ-oscillation in vitro.

Hippocampal network oscillations at gamma frequency band (γ-oscillation, 20-80 Hz) are synchronized synaptic activities generated by the interactions between the excitatory and inhibitory interneurons and are associated with higher brain function such as learning and memory. Despite extensive studies about the modulation of intracellular kinases on synaptic transmission and plasticity, little is known about the effects of these kinases on γ-oscillations. In this study, we examined the effects of several critical intracellular kinases such as cyclic AMP-dependent protein kinase (PKA), protein kinase B (PKB)/Akt, protein kinase C (PKC), extracellular-regulated protein kinases (ERK) and AMP-activated protein kinase (AMPK), known to regulate synaptic transmission, on hippocampal γ-oscillations in vitro. We found that AMPK inhibitor but not PKA, PKC, or ERK inhibitor, strongly enhanced the power of γ-oscillation (γ-power) and that Akt inhibitor weakly increased γ-power. Western blot analysis confirmed that AMPK inhibitor reduced the expression of p-AMPK but not total AMPK. By using the slice whole cell voltage-clamp technique, we found that AMPK inhibitor increased the frequency but not amplitude of spontaneous inhibitory postsynaptic currents (sIPSC) and had no effect on either frequency or amplitude of spontaneous excitatory postsynaptic currents (sEPSC). Therefore, AMPK activation negatively modulates hippocampal γ-oscillation via modulation of the inhibitory neurons.

Levetiracetam induction of theta frequency oscillations in rodent hippocampus in vitro.

Levetiracetam (LEV) has been demonstrated to improve cognitive function. Hippocampal theta rhythm (4-12 Hz) is associated with a variety of cognitively related behaviors, such as exploration in both humans and animal models. We investigated the effects of LEV on the theta rhythm in the rat hippocampal CA3 in hippocampal slices in vitro. We found that LEV increased the theta power in a dose-dependent manner. The increase in theta power can be blocked by GABAA receptor (GABAAR) or NMDA receptor (NMDAR) antagonists but not by AMPA receptor antagonist, indicating the involvement of GABAAR and NMDAR in the induction of theta activity. Interestingly, LEV enhancement of theta power can be also blocked by taurine or GABA-A agonist THIP, indicating that LEV induction of theta may be related to the indirect boosting of GABA action via reduction of extrasynaptic GABAAR activation. Furthermore, the increased theta power can be partially reduced by the mACh receptor (mAChR) antagonist atropine but not by nACh receptor antagonists, suggesting that mAChR activation provides excitatory input into local network responsible for LEV-induced theta. Our study demonstrated that LEV induced a novel theta oscillation in vitro, which may have implications in the treatment of the neuronal disorders with impaired theta oscillation and cognitive function.

Tau accumulation induces synaptic impairment and memory deficit by calcineurin-mediated inactivation of nuclear CaMKIV/CREB signaling.

Intracellular accumulation of wild-type tau is a hallmark of sporadic Alzheimer's disease (AD), but the molecular mechanisms underlying tau-induced synapse impairment and memory deficit are poorly understood. Here we found that overexpression of human wild-type full-length tau (termed hTau) induced memory deficits with impairments of synaptic plasticity. Both in vivo and in vitro data demonstrated that hTau accumulation caused remarkable dephosphorylation of cAMP response element binding protein (CREB) in the nuclear fraction. Simultaneously, the calcium-dependent protein phosphatase calcineurin (CaN) was up-regulated, whereas the calcium/calmodulin-dependent protein kinase IV (CaMKIV) was suppressed. Further studies revealed that CaN activation could dephosphorylate CREB and CaMKIV, and the effect of CaN on CREB dephosphorylation was independent of CaMKIV inhibition. Finally, inhibition of CaN attenuated the hTau-induced CREB dephosphorylation with improved synapse and memory functions. Together, these data indicate that the hTau accumulation impairs synapse and memory by CaN-mediated suppression of nuclear CaMKIV/CREB signaling. Our findings not only reveal new mechanisms underlying the hTau-induced synaptic toxicity, but also provide potential targets for rescuing tauopathies.

Correcting miR92a-vGAT-Mediated GABAergic Dysfunctions Rescues Human Tau-Induced Anxiety in Mice.

Patients with Alzheimer's disease (AD) commonly show anxiety behaviors, but the molecular mechanisms are not clear and no efficient intervention exists. Here, we found that overexpression of human wild-type, full-length tau (termed htau) in hippocampus significantly decreased the extracellular γ-aminobutyric acid (GABA) level with inhibition of γ oscillation and the evoked inhibitory postsynaptic potential (eIPSP). With tau accumulation, the mice show age-dependent anxiety behaviors. Among the factors responsible for GABA synthesis, release, uptake, and transport, we found that accumulation of htau selectively suppressed expression of the intracellular vesicular GABA transporter (vGAT). Tau accumulation increased miR92a, which targeted vGAT mRNA 3' UTR and inhibited vGAT translation. Importantly, we found that upregulating GABA tones by intraperitoneal injection of midazolam (a GABA agonist), ChR2-mediated photostimulating and overexpressing vGAT, or blocking miR92a by using specific antagomir or inhibitor efficiently rescued the htau-induced GABAergic dysfunctions with attenuation of anxiety. Finally, we also demonstrated that vGAT level decreased while the miR92a increased in the AD brains. These findings demonstrate that the AD-like tau accumulation induces anxiety through disrupting miR92a-vGAT-GABA signaling, which reveals molecular mechanisms underlying the anxiety behavior in AD patients and potentially leads to the development of new therapeutics for tauopathies.

The Emerging Roles of CIB1 in Cancer.

Calcium and integrin-binding protein 1 (CIB1) is an EF-hand calcium binding protein, which is involved in many cellular processes, including calcium signaling, cell survival and proliferation, cell migration, cell adhesion and apoptosis. A number of studies have found that CIB1 is ubiquitously expressed and is related to various human diseases, such as cancer, Alzheimer's disease (AD), cardiac hypertrophy and male infertility. The mechanism of CIB1 in human diseases is still not clear, although multiple functions of CIB1 are modulated by interacting with numerous interacting partners. As a calcium binding protein, the roles of CIB1 in calcium signaling by binding calcium or modulating some key modulators, such as calcineurin, integrin, inositol 1,4,5-trisphosphate receptor (IP3R) and taste 1 receptor member 2 (TAS1R2). The tumor promoting mechanisms of CIB1 have been described in different aspects, including promoting tumor cell cycle and proliferation, inhibiting tumor cell apoptosis, and mediating tumor cell migration and angiogenesis. In addition, multiple functions of CIB1, such as neural development, taste or gustation functions, and virus infection are also elucidated. These recent advances have significantly expanded our understanding of the knowledge of CIB1 and highlighted the potential mechanisms of CIB1 in tumor progression.

Nicotinic modulation of Ca2+ oscillations in rat cortical neurons in vitro.

The roles of nicotine on Ca(2+) oscillations [intracellular Ca(2+) ([Ca(2+)]i) oscillation] in rat primary cultured cortical neurons were studied. The spontaneous [Ca(2+)]i oscillations (SCO) were recorded in a portion of the neurons (65%) cultured for 7-10 days in vitro. Application of nicotine enhanced [Ca(2+)]i oscillation frequency and amplitude, which were reduced by the selective α4ß2-nicotinic acetylcholine receptors (nAChRs) antagonist dihydro-ß-erythroidine (DHßE) hydrobromide, and the selective α7-nAChRs antagonist methyllycaconitine citrate (MLA, 20 nM). DHßE reduced SCO frequency and prevented the nicotinic increase in the frequency. DHßE somewhat enhanced SCO amplitude and prevented nicotinic increase in the amplitude. MLA (20 nM) itself reduced SCO frequency without affecting the amplitude but blocked nicotinic increase in [Ca(2+)]i oscillation frequency and amplitude. Furthermore, coadministration of both α4ß2- and α7-nAChRs antagonists completely prevented nicotinic increment in [Ca(2+)]i oscillation frequency and amplitude. Thus, our results indicate that both α4ß2- and α7-nAChRs mediated nicotine-induced [Ca(2+)]i oscillations, and two nAChR subtypes differentially regulated SCO.

Activity- and development-dependent down-regulation of TARPγ8 and GluA1 in cultured rat hippocampal neurons.

AIM: Transmembrane AMPA receptor regulatory proteins (TARPs) regulate the trafficking and expression of AMPA receptors that are essential for the fast excitatory synaptic transmission and plasticity in the brain. This study aimed to investigate the activity-dependent regulation of TARPγ8 in cultured rat hippocampal neurons. METHODS: Rat hippocampal neurons cultured for 7-8 DIV or 17-18 DIV were exposed to the AMPA receptor agonist AMPA at a non-toxic concentration (100 µmol/L) for 4 h. The protein levels of TARPγ8 and AMPA receptor subunits (GluA1 and GluA2) were measured using Western blotting analysis. AMPA-induced currents were recorded in the neurons using a whole-cell recording method. RESULTS: Four-hour exposure to AMPA significantly decreased the protein levels of TARPγ8 and GluA1 in the neurons at 17-18 DIV, but did not change the protein level of TARPγ8 in the neurons cultured at 7-8 DIV. AMPA-induced down-regulation of TARPγ8 and GluA1 was largely blocked by the calpain inhibitor calpeptin (50 µmol/L), but not affected by the caspase inhibitor zVAD (50 µmol/L). Four-hour exposure to AMPA significantly decreased AMPA-induced currents in the neurons at 17-18 DIV, which was blocked by co-exposure to calpeptin (50 µmol/L). CONCLUSION: The down-regulation of TARPγ8 and GluA1 protein levels and AMPA-induced currents in cultured rat hippocampal neurons is activity- and development-dependent, and mediated by endogenous calpain.

[Portable Epileptic Seizure Monitoring Intelligent System Based on Android System].

The clinical electroencephalogram (EEG) monitoring systems based on personal computer system can not meet the requirements of portability and home usage. The epilepsy patients have to be monitored in hospital for an extended period of time, which imposes a heavy burden on hospitals. In the present study, we designed a portable 16-lead networked monitoring system based on the Android smart phone. The system uses some technologies including the active electrode, the WiFi wireless transmission, the multi-scale permutation entropy (MPE) algorithm, the back-propagation (BP) neural network algorithm, etc. Moreover, the software of Android mobile application can realize the processing and analysis of EEG data, the display of EEG waveform and the alarm of epileptic seizure. The system has been tested on the mobile phones with Android 2. 3 operating system or higher version and the results showed that this software ran accurately and steadily in the detection of epileptic seizure. In conclusion, this paper provides a portable and reliable solution for epileptic seizure monitoring in clinical and home applications.

Involvement of Bim in Photofrin-mediated photodynamically induced apoptosis.

BACKGROUND/AIMS: Photodynamic therapy (PDT) is a promising noninvasive technique, which has been successfully applied to the treatment of human cancers. Studies have shown that the Bcl-2 family proteins play important roles in PDT-induced apoptosis. However, whether Bcl-2-interacting mediator of cell death (Bim) is involved in photodynamic treatment remains unknown. In this study, we attempt to determine the effect of Bim on Photofrin photodynamic treatment (PPT)-induced apoptosis in human lung adenocarcinoma ASTC-a-1 cells. METHODS: The translocation of Bim/Bax of the cells were monitored by laser confocal scanning microscope. The levels of Bim protein and activated caspase-3 in cells were detected by western blot assay. Caspase-3 activities were measured by Caspase-3 Fluorogenic Substrate (Ac-DEVD-AFC) analysis. The induction of apoptosis was detected by Hoechst 33258 and PI staining as well as flow cytometry analysis. The effect of Bim on PPT-induced apoptosis was determined by RNAi. RESULTS: BimL translocated to mitochondria in response to PPT, similar to the downstream pro-apoptotic protein Bax activation. PPT increased the level of Bim and activated caspase-3 in cells and that knockdown of Bim by RNAi significantly protected against caspase-3 activity. PPT-induced apoptosis were suppressed in cells transfected with shRNA-Bim. CONCLUSION: We demonstrated the involvement of Bim in PPT-induced apoptosis in human ASTC-a-1 lung adenocarcinoma cells and suggested that enhancing Bim activity might be a potential strategy for treating human cancers.

Transcranial Direct Current Stimulation Ameliorates Behavioral Deficits and Reduces Oxidative Stress in 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine-Induced Mouse Model of Parkinson's Disease.

PURPOSE: Oxidative stress is involved in the pathological process of Parkinson's disease (PD). The present study was designed to investigate the effects of transcranial direct current stimulation (tDCS) on the oxidative stress in a mouse model of PD induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). METHODS: The animals were modulated by tDCS. Behavioral alterations were observed after three weeks of tDCS treatment using rotary performance tests. The mice were sacrificed for the measurement of the level of dopamine (DA), enzymatic tyrosine hydroxylase (TH), nonenzymatic malonaldehyde (MDA), an enzymatic superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) in the mouse brain and serum. RESULTS: The mice treated with MPTP had an increased MDA level but a decreased SOD and GSH-Px activity, as well as a behavior impairment. These abnormalities were significantly attenuated by tDCS treatment and by levodopa and benserazide. DISCUSSION: The study demonstrated that the tDCS could have a potential for the therapeutic usage in the PD.

Prescription consisting of Vitamin C and Baicalin inhibits tumor growth by enhancing the antioxidant capacity in vivo.

PURPOSE: To explore the antitumor effect of prescription consisting of Vitamin C (Vc) and Baicalin (PVB). METHODS: To explore the antitumor effect of PVB, using U14 cervical tumor-bearing mice model was used and the drugs were administrated through the gavages. Spectrophotometry was used to determine the content of superoxide dismutase (SOD), malondialdehyde (MDA) and cytokines IL-2, Il-4 and IFN-γ. RESULTS: PVB had a better antitumor effect than baicalin and Vc used alone with an inhibition rate of 58.18% (p<0.05); PVB significantly improved the spleen index (p<0.01), and significantly reduced MDA content (p<0.01) but increased SOD activity in liver tissue and serum (p<0.01). CONCLUSIONS: PVB shows better antitumor effect than Vc and baicalin used alone, and it can significantly enhance the immunity and antioxidant capacity of the mice.

Co-activation of nAChR and mGluR induces γ oscillation in rat medial septum diagonal band of Broca slices.

AIM: To examine whether co-activation of nAChR and mGluR1 induced γ oscillation (20-60 Hz) in rat medial septum diagonal band of Broca (MSDB) slices. METHODS: Rat brain sagittal slices containing the MSDB were prepared. Extracellular field potentials were recorded with glass microelectrodes. The nAChR and mGluR1 agonists were applied to the slices to induce network activity. Data analysis was performed off-line using software Spike 2. RESULTS: Co-application of the nAChR agonist nicotine (1 µmol/L) and the mGluR1 agonist dihydroxyphenylglycine (DHPG, 25 µmol/L) was able to induce γ oscillation in MSDB slices. The intensity of nAChR and mGluR1 activation was critical for induction of network oscillation at a low (θ oscillation) or high frequency (γ oscillation): co-application of low concentrations of the two agonists only increased the power and frequency of oscillation within the range of θ, whereas γ oscillation mostly appeared when high concentrations of the two agonists were applied. CONCLUSION: Activation of mGluR1 and nAChR is able to program slow or fast network oscillation by altering the intensity of receptor activation, which may provide a mechanism for modulation of learning and memory.

VMP1: a multifaceted regulator of cellular homeostasis with implications in disease pathology.

Vacuole membrane protein 1 (VMP1) is an integral membrane protein that plays a pivotal role in cellular processes, particularly in the regulation of autophagy. Autophagy, a self-degradative mechanism, is essential for maintaining cellular homeostasis by degradation and recycling damaged organelles and proteins. VMP1 involved in the autophagic processes include the formation of autophagosomes and the subsequent fusion with lysosomes. Moreover, VMP1 modulates endoplasmic reticulum (ER) calcium levels, which is significant for various cellular functions, including protein folding and cellular signaling. Recent studies have also linked VMP1 to the cellular response against viral infections and lipid droplet (LD). Dysregulation of VMP1 has been observed in several pathological conditions, including neurodegenerative diseases such as Parkinson's disease (PD), pancreatitis, hepatitis, and tumorogenesis, underscoring its potential as a therapeutic target. This review aims to provide an overview of VMP1's multifaceted roles and its implications in disease pathology.

The PTB and PRR domains of numb regulate neurite outgrowth by influencing voltage-gated calcium channel expression and kinetics.

Numb is an evolutionarily conserved protein that regulates the differentiation of neuronal progenitor cells through unknown mechanisms. Numb has four alternative splice variants with different lengths of phosphotyrosine-binding (PTB) and proline-rich regions (PRR) domains. In this study, we demonstrated that Numb expression was increased in the primary cultures of rat cortical and hippocampal neurons over time in vitro, and Numb antisense inhibited neurite outgrowth. We verified that cells overexpressing short PTB (SPTB) or long PTB (LPTB) domains exhibited differentiation or proliferation, respectively. SPTB-mediated differentiation was related to the PRR domains, as cells expressing SPTB/LPRR had longer dendrites and more branched dendrites than cells expressing SPTB/SPRR. The differentiation of both cell types was completely blocked by the Ca2+ chelator. Western blot analysis revealed the increased total protein expression of voltage-gated calcium channel (VGCC) subunit α1C and α1D in cells expressing SPTB and LPTB Numb. The increased expression of the VGCC ß3 subunit was only observed in cells expressing SPTB Numb. Immunocytochemistry further showed that SPTB-mediated cell differentiation was associated with increased membrane expression of VGCC subunits α1C, α1D and ß3, which corresponded to the higher Ca2+ current (ICa) densities. Furthermore, we found that VGCC of cells transfected with SPTB/SPRR or SPTB/LPRR Numb isoforms exhibit steady-state inactivation (SSI) in both differentiated and undifferentiated phenotypes. A similar SSI of VGCC was observed in the differentiated cells transfected with SPTB/SPRR or SPTB/LPRR Numb isoforms, whereas a left shift SSI of VGCC in cells expressing SPTB/LPRR was detected in the undifferentiated cells. Collectively, these data indicate that SPTB domain is essential for neurite outgrowth involving in membrane expression of VGCC subunits, and LPRR plays a role in neuronal branching and the regulation of VGCC inactivation kinetics.

Palmitoylation regulates myelination by modulating the ZDHHC3-Cadm4 axis in the central nervous system.

The downregulation of Cadm4 (Cell adhesion molecular 4) is a prominent feature in demyelination diseases, yet, the underlying molecular mechanism remains elusive. Here, we reveal that Cadm4 undergoes specific palmitoylation at cysteine-347 (C347), which is crucial for its stable localization on the plasma membrane (PM). Mutation of C347 to alanine (C347A), blocking palmitoylation, causes Cadm4 internalization from the PM and subsequent degradation. In vivo experiments introducing the C347A mutation (Cadm4-KI) lead to severe myelin abnormalities in the central nervous system (CNS), characterized by loss, demyelination, and hypermyelination. We further identify ZDHHC3 (Zinc finger DHHC-type palmitoyltransferase 3) as the enzyme responsible for catalyzing Cadm4 palmitoylation. Depletion of ZDHHC3 reduces Cadm4 palmitoylation and diminishes its PM localization. Remarkably, genetic deletion of ZDHHC3 results in decreased Cadm4 palmitoylation and defects in CNS myelination, phenocopying the Cadm4-KI mouse model. Consequently, altered Cadm4 palmitoylation impairs neuronal transmission and cognitive behaviors in both Cadm4-KI and ZDHHC3 knockout mice. Importantly, attenuated ZDHHC3-Cadm4 signaling significantly influences neuroinflammation in diverse demyelination diseases. Mechanistically, we demonstrate the predominant expression of Cadm4 in the oligodendrocyte lineage and its potential role in modulating cell differentiation via the WNT-ß-Catenin pathway. Together, our findings propose that dysregulated ZDHHC3-Cadm4 signaling contributes to myelin abnormalities, suggesting a common pathological mechanism underlying demyelination diseases associated with neuroinflammation.

Tripeptidyl peptidase II coordinates the homeostasis of calcium and lipids in the central nervous system and its depletion causes presenile dementia in female mice through calcium/lipid dyshomeostasis-induced autophagic degradation of CYP19A1.

Rationale: Tripeptidyl peptidase II (TPP2) has been proven to be related to human immune and neurological diseases. It is generally considered as a cytosolic protein which forms the largest known protease complex in eukaryotic cells to operate mostly downstream of proteasomes for degradation of longer peptides. However, this canonical function of TPP2 cannot explain its role in a wide variety of biological and pathogenic processes. The mechanistic interrelationships and hierarchical order of these processes have yet to be clarified. Methods: Animals, cells, plasmids, and viruses established and/or used in this study include: TPP2 knockout mouse line, TPP2 conditional knockout mouse lines (different neural cell type oriented), TRE-TPP2 knockin mouse line on the C57BL/6 background; 293T cells with depletion of TPP2, ATF6, IRE1, PERK, SYVN1, UCHL1, ATG5, CEPT1, or CCTα, respectively; 293T cells stably expressing TPP2, TPP2 S449A, TPP2 S449T, or CCTα-KDEL proteins on the TPP2-depleted background; Plasmids for eukaryotic transient expression of rat CYP19A1-Flag, CYP19A1 S118A-Flag, CYP19A1 S118D-Flag, Sac I ML GFP Strand 11 Long, OMMGFP 1-10, G-CEPIA1er, GCAMP2, CEPIA3mt, ACC-GFP, or SERCA1-GFP; AAV2 carrying the expression cassette of mouse CYP19A1-3 X Flag-T2A-ZsGreen. Techniques used in this study include: Flow cytometry, Immunofluorescence (IF) staining, Immunohistochemical (IHC) staining, Luxol fast blue (LFB) staining, ß-galactosidase staining, Lipid droplet (LD) staining, Calcium (Ca2+) staining, Stimulated emission depletion (STED) imaging, Transmission electron microscopic imaging, Two-photon imaging, Terminal deoxynucleotidyl transferase (TdT) dUTP nick-end Labeling (TUNEL) assay, Bromodeoxyuridine (BrdU) assay, Enzymatic activity assay, Proximity ligation assay (PLA), In vivo electrophysiological recording, Long-term potentiation (LTP) recording, Split-GFP-based mitochondria-associated membrane (MAM) detection, Immunoprecipitation (IP), Cellular fractionation, In situ hybridization, Semi-quantitative RT-PCR, Immunoblot, Mass spectrometry-based lipidomics, metabolomics, proteomics, Primary hippocampal neuron culture and Morris water maze (MWM) test. Results: We found that TPP2, independent of its enzymatic activity, plays a crucial role in maintaining the homeostasis of intracellular Ca2+ and phosphatidylcholine (PC) in the central nervous system (CNS) of mice. In consistence with the critical importance of Ca2+ and PC in the CNS, TPP2 gene ablation causes presenile dementia in female mice, which is closely associated with Ca2+/PC dysregulation-induced endoplasmic reticulum (ER) stress, abnormal autophagic degradation of CYP19A1 (aromatase), and estrogen depletion. This work therefore uncovers a new role of TPP2 in lipogenesis and neurosteroidogenesis which is tightly related to cognitive function of adult female mice. Conclusion: Our study reveals a crucial role of TPP2 in controlling homeostasis of Ca2+ and lipids in CNS, and its deficiency causes sexual dimorphism in dementia. Thus, this study is not only of great significance for elucidating the pathogenesis of dementia and its futural treatment, but also for interpreting the role of TPP2 in other systems and their related disorders.

CaMKIIα-TARPγ8 signaling mediates hippocampal synaptic impairment in aging.

Aging-related decline in memory and synaptic function are associated with the dysregulation of calcium homeostasis, attributed to the overexpression of voltage-gated calcium channels (VGCC). The membrane insertion of AMPAR governed by the AMPAR auxiliary proteins is essential for synaptic transmission and plasticity (LTP). In this study, we demonstrated the hippocampal expression of the transmembrane AMPAR regulatory proteins γ-8 (TARPγ8) was reduced in aged mice along with the reduced CaMKIIα activity and memory impairment. We further showed that TARPγ8 expression was dependent on CaMKIIα activity. Inhibition of CaMKIIα activity significantly reduced the hippocampal TARPγ8 expression and CA3-CA1 LTP in young mice to a similar level to that of the aged mice. Furthermore, the knockdown of hippocampal TARPγ8 impaired LTP and memory in young mice, which mimicked the aging-related changes. We confirmed the enhanced hippocampal VGCC (Cav-1.3) expression in aged mice and found that inhibition of VGCC activity largely increased both p-CaMKIIα and TARPγ8 expression in aged mice, whereas inhibition of NMDAR or Calpains had no effect. In addition, we found that the exogenous expression of human TARPγ8 in the hippocampus in aged mice restored LTP and memory function. Collectively, these results indicate that the synaptic and cognitive impairment in aging is associated with the downregulation of CaMKIIα-TARPγ8 signaling caused by VGCC activation. Our results suggest that TARPγ8 may be a key molecular biomarker for brain aging and that boosting CaMKIIα-TARPγ8 signaling may be critical for the restoration of synaptic plasticity of aging and aging-related diseases.