Microtubule-associated Protein Research Articles

Frequency of C9orf72, GRN, and MAPT pathogenic variants in patients recruited at the Belgrade Memory Center.

Most of the heritability in frontotemporal dementia (FTD) is accounted for by autosomal dominant hexanucleotide expansion in the chromosome 9 open reading frame 72 (C9orf72), pathogenic/likely pathogenic variants in progranulin (GRN), and microtubule-associated protein tau (MAPT) genes. Until now, there has been no systematic analysis of these genes in the Serbian population. Herein, we assessed the frequency of the C9orf72 expansion, pathogenic/likely pathogenic variants in GRN and MAPT in a well-characterized group of 472 subjects (FTD, Alzheimer's disease - AD, mild cognitive impairment - MCI, and unspecified dementia - UnD), recruited in the Memory Center, Neurology Clinic, University Clinical Center of Serbia. The C9orf72 repeat expansion was detected in 6.98% of FTD cases (13.46% familial; 2.6% sporadic). In the UnD subgroup, C9orf72 repeat expansions were detected in 4.08% (8% familial) individuals. Pathogenic variants in the GRN were found in 2.85% of familial FTD cases. Interestingly, no MAPT pathogenic/likely pathogenic variants were detected, suggesting possible geographical specificity. Our findings highlight the importance of wider implementation of genetic testing in neurological and psychiatric practice managing patients with cognitive-behavioral and motor symptoms.

Inhalation of hydrogen gas mitigates sevoflurane-induced neuronal apoptosis in the neonatal cortex and is associated with changes in protein phosphorylation.

Inhalation of hydrogen (H2) gas is therapeutically effective for cerebrovascular diseases, neurodegenerative disorders, and neonatal brain disorders including pathologies induced by anesthetic gases. To understand the mechanisms underlying the protective effects of H2 on the brain, we investigated the molecular signals affected by H2 in sevoflurane-induced neuronal cell death. We confirmed that neural progenitor cells are susceptible to sevoflurane and undergo apoptosis in the retrosplenial cortex of neonatal mice. Co-administration of 1-8% H2 gas for 3 h to sevoflurane-exposed pups suppressed elevated caspase-3-mediated apoptotic cell death and concomitantly decreased c-Jun phosphorylation and activation of the c-Jun pathway, all of which are induced by oxidative stress. Anesthesia-induced increases in lipid peroxidation and oxidative DNA damage were alleviated by H2 inhalation. Phosphoproteome analysis revealed enriched clusters of differentially phosphorylated proteins in the sevoflurane-exposed neonatal brain that included proteins involved in neuronal development and synaptic signaling. H2 inhalation modified cellular transport pathways that depend on hyperphosphorylated proteins including microtubule-associated protein family. These modifications may be involved in the protective mechanisms of H2 against sevoflurane-induced neuronal cell death.

CEP41, a ciliopathy-linked centrosomal protein, regulates microtubule assembly and cell proliferation.

Centrosomal proteins play pivotal roles in orchestrating microtubule dynamics, and their dysregulation leads to disorders, including cancer and ciliopathies. Understanding the multifaceted roles of centrosomal proteins is vital to comprehend their involvement in disease development. Here, we report novel cellular functions of CEP41, a centrosomal and ciliary protein implicated in Joubert syndrome. We show that CEP41 is an essential microtubule-associated protein with microtubule-stabilizing activity. Purified CEP41 binds to preformed microtubules, promotes microtubule nucleation and suppresses microtubule disassembly. When overexpressed in cultured cells, CEP41 localizes to microtubules and promotes microtubule bundling. Conversely, shRNA-mediated knockdown of CEP41 disrupts the interphase microtubule network and delays microtubule reassembly, emphasizing its role in microtubule organization. Further, we demonstrate that the association of CEP41 with microtubules relies on its conserved rhodanese homology domain (RHOD) and the N-terminal region. Interestingly, a disease-causing mutation in the RHOD domain impairs CEP41-microtubule interaction. Moreover, depletion of CEP41 inhibits cell proliferation and disrupts cell cycle progression, suggesting its potential involvement in cell cycle regulation. These insights into the cellular functions of CEP41 hold promise for unraveling the impact of its mutations in ciliopathies.

Vanillin-Isatin Hybrid-Induced MARK4 Inhibition As a Promising Therapeutic Strategy against Hepatocellular Carcinoma.

Microtubule affinity-regulating kinase 4 (MARK4) is a serine-threonine kinase that phosphorylates microtubule-associated proteins (MAPs) and increases the microtubule dynamics. Due to its direct involvement in initiation, cell division, progression, and cancer metastasis, MARK4 is considered a potential therapeutic target. Here, we designed, synthesized, and characterized vanillin-isatin hybrids and evaluated their MARK4 inhibitory potential. All of the compounds strongly bind to MARK4 and interact closely with the active site residues. Finally, the compound VI-9 was selected for further investigation due to its high binding affinity and strong MARK4 inhibitory potential. Tau-phosphorylation assay has further confirmed that VI-9 significantly reduced the activity of MARK4. Compared with vanillin, VI-9 showed a better binding affinity and MARK4 inhibitory potential. Cell viability assays on human hepatocellular carcinoma (HCC) cell lines C3A and SNU-475 revealed that VI-9 inhibited their growth and proliferation. In addition, these compounds were nontoxic (up to 200 μM) for noncancerous (HEK-293) cells. Interestingly, VI-9 induces apoptosis and decreases the metastatic potential of the C3A and SNU-475 cell lines. The present work opens a newer avenue for vanillin-isatin hybrids and their derivatives in developing MARK4-targeted anticancer therapies.

Quantitative cellular pathology of the amygdala in temporal lobe epilepsy and correlation with magnetic resonance imaging volumetry, tissue microstructure, and sudden unexpected death in epilepsy risk factors.

Amygdala enlargement can occur in temporal lobe epilepsy, and increased amygdala volume is also reported in sudden unexpected death in epilepsy (SUDEP). Apnea can be induced by amygdala stimulation, and postconvulsive central apnea (PCCA) and generalized seizures are both known SUDEP risk factors. Neurite orientation dispersion and density imaging (NODDI) has recently provided additional information on altered amygdala microstructure in SUDEP. In a series of 24 surgical temporal lobe epilepsy cases, our aim was to quantify amygdala cellular pathology parameters that could predict enlargement, NODDI changes, and ictal respiratory dysfunction. Using whole slide scanning automated quantitative image analysis methods, parallel evaluation of myelin, axons, dendrites, oligodendroglia, microglia, astroglia, neurons, serotonergic networks, mTOR-pathway activation (pS6) and phosphorylated tau (pTau; AT8, AT100, PHF) in amygdala, periamygdala cortex, and white matter regions of interest were compared with preoperative magnetic resonance imaging data on amygdala size, and in 13 cases with NODDI and evidence of ictal-associated apnea. We observed significantly higher glial labeling (Iba1, glial fibrillary acidic protein, Olig2) in amygdala regions compared to cortex and a strong positive correlation between Olig2 and Iba1 in the amygdala. Larger amygdala volumes correlated with lower microtubule-associated protein (MAP2), whereas higher NODDI orientation dispersion index correlated with lower Olig2 cell densities. In the three cases with recorded PCCA, higher MAP2 and pS6-235 expression was noted than in those without. pTau did not correlate with SUDEP risk factors, including seizure frequency. Histological quantitation of amygdala microstructure can shed light on enlargement and diffusion imaging alterations in epilepsy to explore possible mechanisms of amygdala dysfunction, including mTOR pathway activation, that in turn may increase the risk for SUDEP.

Mitochondrial Role on Cellular Apoptosis, Autophagy, and Senescence during Osteoarthritis Pathogenesis.

Authors have demonstrated that apoptosis activation is a pathway related to cartilage degradation characteristics of the OA process. Autophagy is an adaptive response to protect cells from various environmental changes, and defects in autophagy are linked to cell death. In this sense, decreased autophagy of chondrocytes has been observed in OA articular cartilage. The aim of this work was to study the role of OA mitochondria in apoptosis, autophagy, and senescence, using OA and Normal (N) transmitochondrial cybrids. Results: OA cybrids incubated with menadione showed a higher percentage of late apoptosis and necrosis than N cybrids. Stimulation of cybrids with staurosporine and IL-1β showed that OA cybrids were more susceptible to undergoing apoptosis than N cybrids. An analysis of the antioxidant response using menadione on gene expression revealed a lower expression of nuclear factor erythroid 2-like 2 and superoxide dismutase 2 in OA than N cybrids. Activation of microtubule-associated protein 1A/1B-light chain 3 was reduced in OA compared to N cybrids. However, the percentage of senescent cells was higher in OA than N cybrids. Conclusion: This work suggests that mitochondria from OA patients could be involved in the apoptosis, autophagy, and senescence of chondrocytes described in OA cartilage.

Dexmedetomidine Inhibits Hippocampal Neuronal Damage Caused by Persistent Isoflurane-Induced Hypotension in Rat Model of Chronic Cerebral Hypoperfusion.

Purpose The purpose of this study was to investigate the effect of dexmedetomidine (DEX) on hypotension-induced neuronal damage in a chronic cerebral hypoperfusion (CCH) model of rats, an established model of cerebral white matter lesions (WML) in humans, which is prevalent in the elderly and closely related to cognitive decline. Methods The CCH model rats were randomly assigned to one of four groups: normotension + no DEX (NN) group (n = 6), normotension + DEX (ND) group (n = 6), hypotension + no DEX (HN) group (n = 6), or hypotension + DEX (HD) group (n = 6). Under isoflurane anesthesia, mean arterial blood pressure was maintained at or above 80 mmHg (normotension) or below 60 mmHg (hypotension) for a duration of two hours. The DEX groups received 50 μg of DEX intraperitoneally. Two weeks later, the Y-maze test and, after preparing brain slices, immunohistochemical staining were performed using antibodies against neuronal nuclei (NeuN), microtubule-associated protein 2 (MAP2), glial fibrillary acidic protein (GFAP), and Ionized calcium-binding adapter molecule 1 (Iba1). Results Behavioral observations showed no significant differences among the groups. Significant reductions of both NeuN-positive cells and the MAP2-positive area were found in the hippocampal CA1 in the HN group compared with NN and ND groups, but not in the HD group. GFAP and Iba-1-positive areas were significantly increased in the HN group, but not in the HD group. Conclusion DEX significantly ameliorated hypotension-induced neuronal damage and both astroglial and microglial activation in the CA1 region of CCH rats.

Effects of Maternal Smoke Exposure on Endoplasmic Reticulum Stress and Autophagy in the Lungs of Offspring Mice.

Cigarette smoke (CS) induces autophagy and endoplasmic reticulum (ER) stress in the lungs. Research suggests that maternal exposure to CS during pregnancy leads to decreased lung function in offspring. However, the effects of maternal CS exposure on lung autophagy and ER stress in offspring during pregnancy remain unclear. C57BL/6J female mice were divided into the AA (air treatment during both pre-pregnancy and pregnancy), AS (air treatment during pre-pregnancy and CS treatment during pregnancy), SA (CS treatment during pre-pregnancy and air treatment during pregnancy), and SS (CS treatment during both pre-pregnancy and pregnancy) groups. The male offspring mice were selected to the study and euthanized 49 days after birth for the study. Hematoxylin and eosin (HE) staining was employed to observe pathological alterations, while transmission electron microscopy (TEM) was utilized to examine ultrastructure and autophagic vesicles. Additionally, the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) method was applied to identify apoptosis in lung tissues. Immunofluorescence, Real-Time PCR, and Western Blot analyses were conducted to assess the expression of ER stress and autophagy-related markers in lung tissues. The findings revealed that exposure to CS heightened the extent of pathological damage and the abundance of autophagosomes in the lungs of offspring mice. TUNEL results indicated an increased fluorescence intensity in the AS, SA and SS groups, with the most significant in AS and SS groups. Furthermore, CS exposure augmented the fluorescence intensity and expression of ER stress and autophagy-related proteins. The expression of C/EBP-homologous protein (CHOP) exhibited no discernible difference between the SA and SS groups but showed a significant increase in the AS group. Conversely, the expression levels of glucose-regulated protein 78 (GRP78), Caspase-12, Beclin-1, and microtubule-associated protein 1 light chain 3 (LC3) exhibited no significant difference between the AS and SA groups, whereas they were significantly upregulated in the SS group. Preconceptional and gestational exposure to CS heightened ER stress and autophagy in the lungs of mouse offspring. However, in mothers who smoked, withdrawal from CS during pregnancy led to a reduction in ER stress and autophagy in the lungs of their offspring.

Acupotomy alleviates knee osteoarthritis in rabbit by regulating chondrocyte mitophagy Pink1-Parkin pathway.

To investigate the effect of acupotomy, on mitophagy and the Pink1-Parkin pathway in chondrocytes from rabbits with knee osteoarthritis (KOA). A KOA model was established via the modified Videman method. Rabbits were randomly divided into a control group (CON), KOA group and KOA + acupotomy group (Acu). Rabbits in the acupotomy group were subjected to acupotomy for 4 weeks after model establishment. The behavior of the rabbits before and after intervention was recorded. Cartilage degeneration was evaluated by optical microscopy and fluorescence microscopy. The level of mitophagy was evaluated by transmission electron microscopy, immunofluorescence and enzyme-linked immunosorbent assay (ELISA). The expression of phosphatase and tensin homolog (PTEN)-induced kinase 1 (Pink1)-Parkin mitophagy pathway components was evaluated by immunofluorescence, Western blotting and real-time polymerase chain reaction. In rabbits with KOA, joint pain, mobility disorders and cartilage degeneration were observed, the Mankin score was increased, collagen type Ⅱ (Col-Ⅱ) expression was significantly decreased, mitophagy was inhibited, mitochondrial function was impaired, and factors associated with the Pink1-Parkin pathway were inhibited. Acupotomy regulated the expression of Pink1-Parkin pathway-related proteins, the mitophagy-related protein microtubule-associated protein-1 light chain-3, the translocase of the outer membrane, and the inner mitochondrial membrane 23; increased the colocalization of mitochondria and autophagosomes; promoted the removal of damaged mitochondria; restored mitochondrial adenosine-triphosphate (ATP) production; and alleviated cartilage degeneration in rabbits with KOA. Acupotomy played a role in alleviating KOA in rabbits by activating mitophagy in chondrocytes via the regulation of proteins that are related to the Pink1-Parkin pathway.

Shaping human brain development and vulnerability through alternative splicing

Alternative splicing contributes to shaping lineage-specific gene expression and phenotypes. In this issue of Cell Genomics, Recinos, Bao, Wang, etal.1 report that the balance between splicing isoforms of the microtubule-associated protein Tau in the brain is differentially regulated among primates by the RNA-binding protein MBNL2, with consequences for protein aggregation and neurodegeneration in humans.

Astragali Radix-Salviae Miltiorrhizae Radix et Rhizoma alleviates acute lung injury in rats by regulating autophagy via PI3K/Akt/mTOR pathway

This study aims to reveal the effects of the herb pair Astragali Radix-Salviae Miltiorrhizae Radix et Rhizoma(AR-SMRR) on phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin(PI3K/Akt/mTOR) pathway and autophagy in the lung tissue of the rat model of acute lung injury(ALI). Fifty adult male SD rats were randomized into sham, model, autophagy inhibition(intraperitoneal injection of chloroquine at 10 mg·kg~(-1)), autophagy induction(intraperitoneal injection of rapamycin at 15 mg·kg~(-1)), and AR-SMRR(5 g·kg~(-1), gavage) groups. The rats in the sham group received intratracheal instillation of normal saline, and those in other groups received intratracheal instillation of lipopolysaccharide(LPS, 5 mg·kg~(-1)) for the modeling of ALI. Seven days before the operation, the rats in the sham and model groups were administrated with normal saline, and those in other groups with corresponding drugs. Specimens were collected 24 h after modeling. The pathological changes of the lung tissue were observed under a light microscope. The lung wet/dry weight ratio and the lactate dehydrogenase(LDH) activity and total protein concentration in the bronchoalveolar lavage fluid(BALF) were measured. Western blot was employed to measure the protein levels of microtubule-associated protein 1-light chain 3(LC3), beclin-1, p62, PI3K, Akt, and mTOR. Compared with the sham group, the model group showed increased histopathological score of the lung tissue, lung wet/dry weight ratio, and LDH activity and protein concentration in BALF. Autophagy inhibition further increased these indicators compared with the model group, while autophagy induction and AR-SMRR lowered the levels. In addition, AR-SMRR up-regulated the protein levels of LC3-Ⅱ and beclin-1, down-regulated the expression of p62, and inhibited the expression of p-PI3K, p-Akt, and p-mTOR in the lung tissue of ALI rats. The findings suggest that AR-SMRR can alleviate the lung injury and edema in the rat model of ALI induced by LPS by enhancing autophagy via down-regulating PI3K/Akt/mTOR signaling pathway.

The effect of long-term magnesium treatment on changes in hepatic autophagic and apoptotic ability of type 2 diabetic female rats and their offspring

AimWe investigated the role of magnesium sulfate (MgSO4) and insulin administration on improved autophagy and apoptosis to prevent diabetes in high-fat diet (HFD)-diabetic parents and their offspring. MethodsA HFD and a low dose of streptozotocin (STZ) were used to induce diabetes. Animals were assigned to four groups: non-diabetic control (NDC), diabetic control (DC), the diabetic group received insulin (INS), and the diabetic group received magnesium (MG). The duration of the research was 6 months, and offspring were fed a normal diet for 4 months. Blood glucose was determined weekly in rats (parents and offspring). The gene expression of adenosine monophosphate-activated protein kinase (AMPKα1), Bcl-2-interacting myosin-like coiled-coil protein (Becline-1), P62, Microtubule-associated protein 1 light chain 3 (LC3-II), and caspase-9 of liver tissues were assessed using Real-time PCR. ResultThe analysis of maternal gene expression data showed that treatment with MG and INS considerably augmented the AMPKα1 and LC3-II genes expression and diminished P62 and caspase-9 expression. Also, a significant decrease in the expression of AMPKα1, LC3-II, P62, and Becline-1 was observed in the female offspring in the MG and INS groups. Significant alterations in levels of AMPKα1, Beclin-1, P62, and caspase-9 mRNA were not observed between groups in male offspring, but the expression of LC3-II considerably diminished in the groups compared with the DC group. DiscussionOur data demonstrated that MG supplementation strengthened the mother's autophagy and reduced the transmission of damage to the female offspring. In the male offspring, the transmission of damage was generally less, and MG improved the autophagy condition in the male offspring. Our findings support the presence of a link between autophagy induction and MG-modified biomaterials and determine a potential mechanism of MG-mediated diabetes and autophagy.

Impaired autophagy mechanisms associated with phospholamban-R14del disease

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): Leducq Foundation Phospholamban (PLN) is a key modulator of sarcoplasmic reticulum Ca2+ homeostasis and cardiac contractility. The PLN variant c.40_42delAGA (p.R14del) leads to arrhythmogenic cardiomyopathy characterized by life-threatening ventricular arrhythmias and sudden cardiac death. A large number of PLN-R14del carriers have been identified worldwide, although the expanding use of genetic testing and increased awareness is unveiling a higher frequency. PLN-containing aggregates are emerging as a hallmark of this disease, and are increasingly believed to be associated with disease pathogenesis. However, the mechanism leading to the formation of aggregates is unknown. We performed an in depth molecular and cellular analysis utilizing in vitro systems to determine if these aggregates result from aberrations in autophagy, and the underlying mechanisms. Utilizing cell culture systems we studied the expression level and subcellular distribution of fundamental autophagy-related proteins and evaluated the impact of autophagy inducers and inhibitors. Expression of PLN-R14del in different cell culture systems (HEK293 and H9c2 cells) was found to result in PLN aggregate formation, which were determined to contain the autophagy marker proteins sequestosome-1 (p62) and microtubule-associated protein light chain 3 (LC3), indicating inefficient degradation by the autophagy pathway. In support of this, PLN-R14del expressing cells were shown to exhibit increased p62 and LC3-II protein levels. This was associated with significantly reduced autophagic flux, as demonstrated by examination of LC3-II protein levels after autophagy inhibition. Moreover, by detailed immunofluorescence analysis, we determined reduced co-localization of the autophagosomal protein LC3 and the lysosomal associated membrane protein 1 (LAMP1) in PLN-R14del cells, suggesting impaired autophagosome-lysosome fusion. We next examined the distribution of key proteins mediating autophagosome-lysosome membrane fusion including the Ras-related protein Rab7, the ultraviolet radiation resistance-associated gene (UVRAG) and membrane tether proteins. In PLN-R14del transfected cells, significant alterations in their co-localization with LC3 were observed, indicating their impaired recruitment to the autophagosomes. Importantly, in PLN-WT cells changes in cytosolic Ca2+ levels by thapsigargin treatment were found to recapitulate the autophagic defects of PLN-R14del, suggesting that Ca2+ alterations are a contributing factor of PLN-R14del mediated aberrant autophagy. In conclusion, our findings reveal a causal relationship between PLN-R14del and autophagy dysregulation, through inhibition of autophagosome-lysosome fusion and autophagic flux reduction. This ultimately leads to aggregate formation, an early pathological sign in human patients.

Autophagy Regulates Transglutaminase-1 Expression and Vitamin C Enhances Autophagic Activity in Keratinocytes

Vitamin C, known for its various effects on the skin, promotes epidermal differentiation and enhances skin barrier function. However, the underlying mechanism remains unclear. Autophagy is an intracellular degradation system that maintains cellular homeostasis. Although autophagy decrement has been associated with barrier defects in skin diseases, the mechanism by which autophagy regulates skin barrier function remains insufficiently understood. Therefore, this study aimed to investigate the relationship between autophagy and transglutaminase-1 (TGase-1), a molecule required to form the cornified envelope that contributes to skin barrier function. We also examined the effect of vitamin C on autophagy in epidermal keratinocytes. Autophagy modulation through the knockdown of autophagy-related molecules (ATG5, ATG7, and ATG13) significantly decreased TGase-1 expression in human epidermal keratinocytes. Furthermore, vitamin C treatment enhanced the autophagic activity of epidermal keratinocytes and suppressed TGase-1 expression decrease in ATG13 knockdown cells. In conclusion, TGase-1 expression can be regulated by autophagy, and vitamin C may be involved in skin barrier function through autophagy activation. Abbreviations: TGase-1: transglutaminase-1; CE: cornified envelope; ATG5: autophagy related 5; ATG7: autophagy related 7, ATG13: autophagy related 13, LOR: loricrin; FLG: filaggrin; TBP: TATA-box binding protein; LC3: microtubule-associated protein 1 light chain 3; CQ: chloroquine; VC: vitamin C; CTL: control.

Human tau N-terminal domain-specific monoclonal antibodies: screening and application in blood detection

The antibodies to the microtubule-associated protein tau play a role in basic and clinical studies of Alzheimer's disease (AD) and other tauopathies. With the recombinant human tau441 as the immunogen, the hybridoma cell strains secreting the anti-human tau N-terminal domain (NTD-tau) monoclonal antibodies were generated by cell fusion and screened by limiting dilution. The purified monoclonal antibodies were obtained by inducing the mouse ascites and affinity chromatography. The sensitivity and specificity of the monoclonal antibodies were examined by indirect ELISA and Western blotting, respectively. A double antibody sandwich ELISA method for detecting human tau protein was established and optimized. The results showed that the positive cloning rate of hybridoma cells was 83.6%. A stable cell line producing ZD8F7 antibodies was established, and the antibody titer in the supernatant of the cell line was 1:16 000. The antibody titer in the ascitic fluid was higher than 1:256 000; and the titer of purified ZD8F7 monoclonal antibodies was higher than 1:128 000. The epitope analysis showed that the ZD8F7 antibody recognized tau21-37 amino acid in the N-terminal domain. The Western blotting results showed that the ZD8F7 antibody recognized the recombinant human tau protein of 50-70 kDa and the human tau protein of 50 kDa in the brain tissue of transgenic AD model mice (APP/PS1/tau). With ZD8F7 as a capture antibody, a quantitative detection method for human tau protein was established, which showed a linear range of 7.8-500.0 pg/mL and could identify human tau protein in the brain tissue of AD transgenic mice and human plasma but not recognize the mouse tau protein. In conclusion, the human NTD-tau-specific monoclonal antibody and the double antibody sandwich ELISA method established in this study are highly sensitive and can serve as a powerful tool for the detection of tau protein in neurodegenerative diseases.

Neuronal glutathione depletion elevates the Aβ42/Aβ40 ratio and tau aggregation in Alzheimer's disease mice.

Alzheimer's disease (AD) involves reduced glutathione levels, causing oxidative stress and contributing to neuronal cell death. Our prior research identified diminished glutamate-cysteine ligase catalytic subunit (GCLC) as linked to cell death. However, the effect of GCLC on AD features such as amyloid and tau pathology remained unclear. To address this, we investigated amyloid pathology and tau pathology in mice by combining neuron-specific conditional GCLC knockout mice with amyloid precursor protein (App) knockin (KI) or microtubule-associated protein tau (MAPT) KI mice. Intriguingly, GCLC knockout resulted in an increased Aβ42/40 ratio. Additionally, GCLC deficiency in MAPT KI mice accelerated the oligomerization of tau through intermolecular disulfide bonds. These findings suggest that the decline in glutathione levels, due to aging or AD pathology, may contribute to the progression of AD.

P.002 Distinct neuropsychiatric symptom trajectories in frontotemporal dementia across genetic mutations

Background: Frontotemporal dementia (FTD) often presents with varying neuropsychiatric symptoms (NPS), which may differ based on genetic mutations. We hypothesized distinct NPS trajectories in FTD progression among carriers of chromosome 9 open reading frame 72 (C9orf72), progranulin (GRN), and microtubule-associated protein tau (MAPT) mutations. Methods: We analyzed 1662 participants from ALLFTD, including 342 C9orf72, 148 GRN, 168 MAPT mutation carriers, and 1004 noncarriers. We categorized participants into four stages based on CDR plus NACC FTLD global scores: 1) Presymptomatic (consistent CDR=0), 2) Early conversion (CDR increasing from 0 to 0.5), 3) Advanced conversion (CDR increasing from 0.5 to ≥1.0), and 4) Symptomatic (CDR>1.0). The Neuropsychiatric Inventory-Questionnaire (NPI-Q) assessed NPS changes, analyzed using a mixed-effects model, accounting for age and baseline scores. Results: Our results indicated similar NPS trajectories in the presymptomatic stage for all groups. Notably, during early conversion, C9orf72 and GRN carriers exhibited significantly higher NPI-Q score increases than MAPT carriers, primarily in psychosis and hyperactivity domains. In later stages, increases in NPS were similar across groups. Conclusions: This study suggests familial FTD progression, particularly in TDP-43 pathology, may involve more severe NPS like psychosis or hyperactivity, differing from tau pathology or sporadic FTD. Further research is needed to explore these distinct trajectories.

N-Acetylneuraminic Acid Inhibits Melanogenesis via Induction of Autophagy

N-acetylneuraminic acid (Neu5Ac) is the predominant form of sialic acid present in the glossy swiftlet (Collocalia esculenta). It is also the only form of sialic acid detected in the human body. In this study, we investigated the mechanism underlying melanogenesis inhibition by Neu5Ac. We discovered that a reduction in tyrosinase protein levels led to an inhibition of melanin production by Neu5Ac. Additionally, the mRNA and protein levels of ubiquitin-specific protease (USP5) and microtubule-associated protein 1 light chain 3 (LC3)-II increased, while those of p62 decreased, indicating enhanced autophagic activity. Lysosomal cathepsin L2 protein levels also increased, and immunostaining revealed colocalization of lysosomal membrane protein (LAMP)-1 and tyrosinase. Additionally, levels of chaperonin containing T-complex polypeptide (CCT), implicated in increased autophagic flux, were elevated. Altogether, these findings suggest that tyrosinase-containing coated vesicles are transported by Neu5Ac into the autophagic degradation pathway, suppressing mature melanosome generation. This process involves increased USP5 levels preventing recognition of polyubiquitin by proteasomes. Furthermore, elevated CCT3 protein levels may enhance autophagic flux, leading to the incorporation of tyrosinase-containing coated vesicles into autophagosomes. These autophagosomes then fuse with lysosomes for cathepsin L2–mediated degradation. Thus, our findings suggest that Neu5Ac reduces tyrosinase activity and inhibits melanosome maturation by promoting selective autophagic degradation of abnormal proteins by p62.

A helping HAND: therapeutic potential of MAGL inhibition against HIV-1-associated neuroinflammation.

Human immunodeficiency virus (HIV) affects nearly 40 million people globally, with roughly 80% of all people living with HIV receiving antiretroviral therapy. Antiretroviral treatment suppresses viral load in peripheral tissues but does not effectively penetrate the blood-brain barrier. Thus, viral reservoirs persist in the central nervous system and continue to produce low levels of inflammatory factors and early viral proteins, including the transactivator of transcription (Tat). HIV Tat is known to contribute to chronic neuroinflammation and synaptodendritic damage, which is associated with the development of cognitive, motor, and/or mood problems, collectively known as HIV-associated neurocognitive disorders (HAND). Cannabinoid anti-inflammatory effects are well documented, but therapeutic utility of cannabis remains limited due to its psychotropic effects, including alterations within brain regions encoding reward processing and motivation, such as the nucleus accumbens. Alternatively, inhibiting monoacylglycerol lipase (MAGL) has demonstrated therapeutic potential through interactions with the endocannabinoid system. The present study utilized a reward-related operant behavioral task to quantify motivated behavior in female Tat transgenic mice treated with vehicle or MAGL inhibitor MJN110 (1 mg/kg). Brain tissue was collected to assess dendritic injury and neuroinflammatory profiles, including dendritic microtubule-associated protein (MAP2ab) intensity, microglia density, microglia morphology, astrocyte density, astrocytic interleukin-1ß (IL-1ß) colocalization, and various lipid mediators. No significant behavioral differences were observed; however, MJN110 protected against Tat-induced dendritic injury by significantly upregulating MAP2ab intensity in the nucleus accumbens and in the infralimbic cortex of Tat(+) mice. No or only minor effects were noted for Iba-1+ microglia density and/or microglia morphology. Further, Tat increased GFAP+ astrocyte density in the infralimbic cortex and GFAP+ astrocytic IL-1ß colocalization in the nucleus accumbens, with MJN110 significantly reducing these measures in Tat(+) subjects. Lastly, selected HETE-related inflammatory lipid mediators in the striatum were downregulated by chronic MJN110 treatment. These findings demonstrate anti-inflammatory and neuroprotective properties of MJN110 without cannabimimetic behavioral effects and suggest a promising alternative to cannabis for managing neuroinflammation.

Lineage-specific splicing regulation of MAPT gene in the primate brain

Divergence of precursor messenger RNA (pre-mRNA) alternative splicing (AS) is widespread in mammals, including primates, but the underlying mechanisms and functional impact are poorly understood. Here, we modeled cassette exon inclusion in primate brains as a quantitative trait and identified 1,170 (∼3%) exons with lineage-specific splicing shifts under stabilizing selection. Among them, microtubule-associated protein tau (MAPT) exons 2 and 10 underwent anticorrelated, two-step evolutionary shifts in the catarrhine and hominoid lineages, leading to their present inclusion levels in humans. The developmental-stage-specific divergence of exon 10 splicing, whose dysregulation can cause frontotemporal lobar degeneration (FTLD), is mediated by divergent distal intronic MBNL-binding sites. Competitive binding of these sites by CRISPR-dCas13d/gRNAs effectively reduces exon 10 inclusion, potentially providing a therapeutically compatible approach to modulate tau isoform expression. Our data suggest adaptation of MAPT function and, more generally, a role for AS in the evolutionary expansion of the primate brain.