Biology subjects

Endo, A.

Publications and source records attributed to Endo, A..

9 recordsLinked to original sources

bioRxiv2026

BRCA2 loss triggers a downward spiral of genomic instability via ROS-dependent metabolic collapse

BRCA2 plays a central role in maintaining genome integrity through homologous recombination and replication-fork protection, yet the compensatory networks sustaining BRCA2-deficient cells remain unclear. Here we show BRCA2 enforces a homeostatic mechanism aligning mitochondrial respiration with DNA repair capacity in both cancer and non-cancer contexts. Genome-wide CRISPR screening identified glutathione metabolism and base-excision repair as the key compensatory networks sustaining BRCA2-deficient cells by detoxifying mitochondria-derived reactive oxygen species. BRCA2 loss provokes an acute mitochondrial ROS surge, causing 8-oxoguanine accumulation and a systemic metabolic crisis marked by NAD+ and glutathione depletion. PARP inhibitor targets DNA replication vulnerabilities, increasing the cellular requirement for BRCA2. The resulting oxidative burden primes cells for TP53-dependent apoptosis in G1 during olaparib treatment, which extends cytotoxicity beyond canonical S-phase stress. These findings indicate BRCA2 prevents metabolic flux from outpacing repair capacity, providing a rationale for combining PARP inhibition with redox modulation to enhance efficacy and overcome resistance. HighlightsO_LIAcute BRCA2 loss induces ROS and mitochondrial dysfunction creating a metabolic scar C_LIO_LIOxidative lesions drive PARP hyperactivation and precipitate a cellular NAD crisis C_LIO_LIPARP inhibitors provoke TP53-dependent apoptosis in G1 beyond replication stress in S phase C_LIO_LIGlutathione deficiency exacerbates bone marrow failure under BRCA2 depletion C_LIO_LIBRCA2 tightly couples mitochondrial redox homeostasis to genomic maintenance C_LI

cell biology↗

bioRxiv2025

Tbx1 heterozygosity in the oligodendrocyte lineage has distinct effects on myelinated axons in the fimbria and on behaviors related to neurodevelopmental disorders in mice.

Constitutive heterozygosity of Tbx1, a T-box transcription factor gene located within the 22q11.2 deletion region, results in behavioral deficits and altered composition of myelinated axons in the fimbria, together with reduced levels of an oligodendrocyte precursor cell (OPC) marker, in mice. However, the cellular origins of these effects and the extent to which axonal changes causally contribute to behavioral impairments remain unclear. We hypothesized that Tbx1 deficiency specifically within the oligodendrocyte lineage contributes to myelin and behavioral phenotypes. To test this hypothesis, we first demonstrated through in vitro siRNA knockdown that Tbx1 regulates both OPCs and mature oligodendrocytes. Subsequently, we assessed the impact of Tbx1 heterozygosity initiated in OPCs on behavioral and myelin phenotypes in male conditional PdgfrCre;Tbx1+/flox mice. These mice exhibited Cre-mediated recombination in Pdgfr-expressing brain regions and in the OPC progeny within the fimbria. At one month of age, the mutants displayed a higher rate of spontaneous alternation at the longest inter-trial interval in the T-maze compared to their wild-type littermates--an effect that was dissipated at two months. No significant phenotypic abnormalities were observed in conditional PdgfrCre;Tbx1+/flox mice regarding neonatal ultrasonic vocalizations, social interaction, novel object approach, anxiety-like behavior (elevated plus maze), or open-field locomotion and thigmotaxis. Electron microscopic analysis revealed a compositional shift in myelinated axons within the fimbria of adult male mutants, characterized by an increased number of myelinated axons in the 300-800 nm diameter range and a decreased number in the [~]1,200 nm and [~]1,400 nm ranges, with myelin thickness remaining unchanged across diameters. These findings indicate that Tbx1 heterozygosity in the oligodendrocyte lineage leads to a selective shift towards smaller myelinated axons in the fimbria and a transiently higher level of capacity for working memory and cognitive flexibility. However, it does not replicate the full spectrum of myelination abnormalities or the broader cognitive and social deficits observed in constitutive Tbx1 heterozygotes, suggesting that Tbx1 deficiency in non-oligodendrocyte lineage cells may lead to altered myelination and neurodevelopmental behavioral impairments.

neuroscience↗

bioRxiv2025

Reliable Detection of SGLT2 Protein through Knockout-based Antibody Characterization and Optimized Procedures

IntroductionSodium-glucose cotransporter 2 (SGLT2) is a key mediator of renal glucose reabsorption. Its pharmacological inhibition exerts cardio- and reno-protective benefits. Despite widespread clinical interest, reliable detection of SGLT2 protein remains challenging due to concerns regarding the specificity of available antibodies. MethodsThis study assessed the specificity of eight commercially available anti-SGLT2 antibodies by immunohistochemistry and Western blotting. Genetically engineered Sglt2-deficient mice and rats, generated via clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 (CRISPR/Cas9) technology, were employed as definitive negative controls. Additionally, human kidney tissues, including renal cell carcinoma samples, were analyzed. ResultsAmong the antibodies tested, few exhibited robust specificity, characterized by substantial immunostaining with minimal background in wild-type kidney tissues and complete absence of staining in Sglt2-deficient samples. In renal cell carcinoma samples, a validated antibody detected SGLT2 immunostaining in proximal tubules of non-tumor regions but not in tumor areas. Subcellular localization studies revealed that SGLT2 was enriched within proximal tubular microvilli, partially overlapping with its co-factor PDZK1IP1 (MAP17). LRP2 (megalin) and NHE3 were placed at the microvillar base and did not colocalize with SGLT2. Western blotting identified a specific SGLT2 band at approximately 55 kDa in kidney lysates using several antibodies under optimized procedures. This band was shifted to approximately 45 kDa after enzymatic removal of N-linked glycans. One antibody detected a weak band at the same molecular mass even in kidney lysates from Sglt2-deficient rodents. ConclusionsConsiderable variability exists in the specificity of commercially available anti-SGLT2 antibodies. Only a limited number of antibodies are suitable for reliable detection of SGLT2 in rodent and human samples. Rigorous antibody characterization, including the use of knockout controls and optimized experimental conditions, is essential to ensure reproducibility and prevent misinterpretation in studies investigating the biological and pathophysiological roles of SGLT2.

molecular biology↗

bioRxiv2025

Metabolic cell death of labile iron deficiency as a vulnerability of head and neck squamous cancer cells evaded by BACH1

Head and neck squamous cell carcinoma (HNSCC) remains difficult to treat due to the lack of molecularly targeted drugs with high anti-tumor efficacy and safety. To investigate the involvement of the transcription factor BACH1, which is known to promote the metastasis of various cancers, in the malignant properties of HNSCC cells, we examined the effects of BACH1 depletion with short interfering RNAs in human HNSCC cell lines. We found that knockdown of BACH1 induced cell death due to depletion of intracellular labile iron which is not tightly bound to protein. Mitochodrial electron transfer chain activity was severely reduced but efficiently resuced with supplementation of iron in the medium. By combining chromatin immunoprecipitation-sequence and RNA-sequence analyses, we found that BACH1 represses ferritin genes in HNSCC cells. BACH1 knockdown was found to enhance the effect of tipifarnib, a selective inhibitor of farnesyltransferase required for HRAS activation, resulting in efficient inhibition of proliferation of HNSCC cell lines in vitro. These results indicate that BACH1 is essential for maintaining the amount of labile iron in HNSCC cells to evade metabolic cell death of iron deficiency and to proliferate. BACH1 can be a target for conferring Tipifarnib sensitivity to HNSCC cells.

cancer biology↗

bioRxiv2025

Ubiquitination-activated TAB-TAK1-IKK-NF-kB axis modulates gene expression for cell survival in the lysosomal damage response

The lysosomal damage response is important for the maintenance of cellular homeostasis. Although the mechanisms underlying the repair and autophagic elimination of damaged lysosomes have been elucidated, the early signal transduction pathways and genes induced in response to lysosomal damage remain elusive. We performed transcriptome and proteome analyses and found that the TAB-TAK1- IKK-NF-{kappa}B axis is activated by K63-linked ubiquitin chains that accumulate on damaged lysosomes. This activates the expression of various transcription factors and cytokines that promote anti-apoptosis and intercellular signaling. The findings highlight the crucial role of ubiquitin-regulated signal transduction and gene expression in cell survival and cell-cell communication in response to lysosomal damage. The results suggest that the ubiquitin system is not only involved in the removal of damaged lysosomes by lysophagy, but also functions in the activation of cellular signaling for cell survival.

cell biology↗

bioRxiv2022

An attenuated vaccinia vaccine encoding the SARS-CoV-2 spike protein elicits broad and durable immune responses, and protects cynomolgus macaques and human ACE2 transgenic mice from SARS-CoV-2 and its variants

As long as the coronavirus disease 2019 (COVID-19) pandemic continues, new variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) with altered antigenicity will emerge. The development of vaccines that elicit robust, broad, and durable protection against SARS-CoV-2 variants is urgently needed. We have developed a vaccine (rDIs-S) consisting of the attenuated vaccinia virus DIs strain platform carrying the SARS-CoV-2 S gene. rDIs-S induced neutralizing antibody and T-lymphocyte responses in cynomolgus macaques and human angiotensin converting enzyme 2 (hACE2) transgenic mice, and showed broad protection against SARS-CoV-2 isolates ranging from the early-pandemic strain (WK-521) to the recent Omicron BA. 1 variant (TY38-839). Using a tandem mass tag (TMT) -based quantitative proteomic analysis of lung homogenates from hACE2 transgenic mice, we found that, among mice subjected to challenge infection with WK-521, vaccination with rDIs-S prevented protein expression related to the severe pathogenic effects of SARS-CoV-2 infection (tissue destruction, inflammation, coagulation, fibrosis, and angiogenesis) and restored protein expression related to immune responses (antigen presentation and cellular response to stress). Furthermore, long-term studies in mice showed that rDIs-S maintains S protein-specific antibody titers for at least 6 months after a 1st vaccination. Thus, rDIs-S appears to provide broad and durable protective immunity against SARS-CoV-2, including current and possibly future variants.

microbiology↗

bioRxiv2021

Placental mammals acquired the functional region and domain in NRK for regulating the CK2-PTEN-AKT pathway and placental cell proliferation

The molecular evolution processes underlying the acquisition of the placenta in eutherian ancestors are not fully understood. Mouse NCK-interacting kinase (NIK)-related kinase (NRK) is expressed highly in the placenta and plays a role in preventing placental hyperplasia. Here, we show the molecular evolution of NRK, which confers its function for inhibiting placental cell proliferation. Comparative genome analysis identified NRK orthologues across vertebrates, which share the kinase and citron homology (CNH) domains. Evolutionary analysis revealed that NRK underwent extensive amino acid substitutions in the ancestor of placental mammals and has been since conserved. Biochemical analysis of mouse NRK revealed that the CNH domain binds to phospholipids, and a region in NRK binds to and inhibits casein kinase-2 (CK2), which we named the CK2-inhibitory region (CIR). Cell culture experiments suggest the following: (1) mouse NRK is localised at the plasma membrane via the CNH domain, where the CIR inhibits CK2. (2) This mitigates CK2-dependent phosphorylation and inhibition of PTEN, and (3) leads to the inhibition of AKT signalling and cell proliferation. Nrk deficiency increased phosphorylation levels of PTEN and AKT in mouse placenta, supporting our hypothesis. Unlike mouse NRK, chicken NRK did not bind to phospholipids and CK2, decrease phosphorylation of AKT, or inhibit cell proliferation. Both the CNH domain and CIR have evolved under purifying selection in placental mammals. Taken together, our study suggests that placental mammals acquired the phospholipid-binding CNH domain and CIR in NRK for regulating the CK2-PTEN-AKT pathway and placental cell proliferation.

molecular biology↗

bioRxiv2021

The molecular basis of ubiquitin-specific protease 8 autoinhibition by the WW-like domain

Ubiquitin-specific protease 8 (USP8) is a deubiquitinating enzyme involved in multiple membrane trafficking pathways. The enzyme activity is inhibited by binding to 14-3-3 proteins, and mutations of the 14-3-3 binding motif in USP8 are related to Cushings disease. However, the molecular basis of USP8 enzyme activity regulation remains unclear. Here, we identified amino acids 645-684 of USP8 as an autoinhibitory region, which our pull-down and single-molecule FRET assay results suggested interacts with the catalytic USP domain. In silico modelling indicated that the region forms a WW-like domain structure, plugs the catalytic cleft, and narrows the entrance to the ubiquitin-binding pocket. Furthermore, 14-3-3 was found to inhibit USP8 enzyme activity partly by enhancing the interaction between the WW-like and USP domains. These findings provide the molecular basis of USP8 autoinhibition via the WW-like domain. Moreover, they suggest that the release of autoinhibition may underlie Cushings disease caused by USP8 mutations.

biochemistry↗

bioRxiv2019

Fine-scale family structure shapes influenza transmission risk in households: insights from a study of primary school students in Matsumoto city, 2014/15.

BackgroundHouseholds are important settings for the transmission of seasonal influenza. Previous studies found that the per-person risk of within-household transmission decreases with household size. However, more detailed heterogeneities driven by household composition and contact patterns have not been studied. MethodsWe employed a mathematical model which accounts for infections both from outside and within the household. The model was applied to citywide primary school surveillance data of seasonal influenza in 2014/15 season in Matsumoto city, Japan. We compared a range of models to estimate the structure of household transmission. ResultsFamilial relationship and household composition strongly influenced the transmission patterns of seasonal influenza in households. Children had substantially high risk of infection from outside the household (up to 20%) compared with adults (1-3%). Intense transmission was observed within-generation (between children/parents/grandparents) and also between mother and child, with transmission risks typically ranging around 5-20% depending on the pair and household composition. ConclusionsWe characterised heterogeneity in household transmission patterns of influenza. Children were identified as the largest source of secondary transmission, with family structure influencing infection risk. This suggests that vaccinating children would have stronger secondary effects on transmission than would be assumed without taking into account transmission patterns within the household.

epidemiology↗