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Biology subjects

Takahashi, T.

Publications and source records attributed to Takahashi, T..

At least 19 recordsLinked to original sources

Secretion is a second fate for p62 and is coupled to KEAP1/NRF2 signaling

Cells degrade the autophagy receptor p62/sequestosome 1 (SQSTM1) in lysosomes. By knocking the HiBiT peptide into the endogenous SQSTM1 locus, we show that export is a second, quantitatively comparable fate. Specifically, p62 leaves cells continuously inside membrane-enclosed carriers at a rate similar to that of LC3B. Blocking lysosomal degradation amplifies release through an ATG5- and FIP200-dependent route, whereas a basal route persists in autophagy-deficient cells. Thus, p62 exits by at least two parallel pathways. Export requires PB1-mediated self-oligomerization but not LC3 binding, Kelch-like ECH-associated protein 1 (KEAP1) binding, or an intact ubiquitin-associated domain. Hence, oligomerization is the sorting determinant. KEAP1 is also released, and dominant-negative RAB27A retains both proteins inside cells and lowers nuclear factor erythroid 2-related factor 2 transcriptional output. Secretion is therefore a second outlet for the p62-KEAP1 module, and its interruption co-varies with a dampened oxidative stress response.

cell biology↗

Enhancing the hyaline cartilage regenerative potential of induced pluripotent stem cell-derived chondrocyte cell sheets

Introduction Autologous and allogeneic chondrocyte cell sheet transplantation has shown safety and potential efficacy for cartilage defects associated with knee osteoarthritis. Although polydactyly-derived chondrocyte (PDC) cell sheets have been used clinically for allogeneic transplantation, a scalable and reliable alternative cell source is needed. This study aimed to establish a proof-of-concept protocol for generating chondrocyte cell sheets from clinical-grade human induced pluripotent stem cells (iPS cells). Methods Cartilaginous tissue was generated from human iPS cells, and isolated chondrocytes were used to fabricate iPS cell-derived chondrocyte sheets. In Phase 1, sheets were produced in high-serum medium under normoxic, hypoxic, or hypoxic/high-seeding-density conditions and compared with PDC sheets using a three-dimensional in vitro model and xenogeneic orthotopic transplantation in an immunodeficient rat model. In Phase 2, sheets were produced in low-serum medium under hypoxic/high-seeding-density conditions and evaluated for cartilage-related gene expression, secreted factors, cell surface marker expression, and in vivo cartilage repair. Results In Phase 1, hypoxic/high-seeding-density culture enhanced in vitro chondrogenic properties. However, after transplantation, iPS cell-derived chondrocyte sheets formed fibrotic repair tissue, whereas PDC sheets generated hyaline-like cartilage. In Phase 2, low-serum culture increased expression of cartilage-related genes, including collagen type II alpha 1 (COL2A1) and SRY-box transcription factor 9 (SOX9), enhanced secretion of transforming growth factor beta 1 and melanoma inhibitory activity, and upregulated CD9, CD26, CD56, CD201, CD227, and GD2. Low-serum iPS cell-derived chondrocyte sheets regenerated hyaline cartilage at 4 weeks, and the repair tissue was maintained at 12 weeks without bone formation. Conclusions A robust fabrication protocol enabled human iPS cell-derived chondrocyte sheets to regenerate hyaline-like cartilage in vivo. These findings support their potential as a scalable cell source for clinical cartilage repair.

bioengineering↗

A region-specific murine intestinal monolayer platform for assessing iron form-dependent transepithelial transport

Iron absorption in the small intestine has classically been described by the duodenal DMT1/FPN1 pathway for inorganic non-heme iron, yet emerging evidence suggests that chemically distinct iron forms may use region-specific routes. Nicotianamine (NA), a plant-derived metal chelator, can form NA-iron (NA-Fe) complexes and has been proposed to support intestinal iron absorption through amino acid transporter pathways. However, direct comparisons of transepithelial transfer of inorganic iron and NA-Fe across defined small intestinal regions under controlled epithelial conditions remain limited. Here, we established region-specific 2D epithelial monolayers derived from duodenal and proximal jejunal crypt organoids from male ICR mice cultured on Transwell inserts. Transcriptomic profiling indicated partial retention of regional identity, and barrier integrity was confirmed by junctional marker localization, transepithelial electrical resistance, and low paracellular permeability. We then examined expression and polarized localization of candidate transporters for inorganic iron (Dmt1/Fpn1) and NA-Fe (Pat1/Lat2). Finally, we quantified transepithelial transport using apical loading of isotope-labeled iron (55Fe) or NA-55Fe and measured radioactivity appearing in the basolateral compartment as the primary readout of transepithelial flux. Basolateral appearance of inorganic 55Fe was comparable between duodenum- and proximal jejunum-derived monolayers, whereas NA-55Fe exhibited significantly greater basolateral appearance in proximal jejunum-derived monolayers. These findings demonstrate that organoid derived, region-specific monolayers provide a tractable epithelial platform to evaluate iron form-dependent, region-specific transepithelial transfer and to enable further mechanistic dissection of NA-Fe transport. NEW & NOTEWORTHYNon-heme iron absorption may depend on iron chemical form and intestinal region, but direct epithelial comparisons are scarce. We established duodenum and proximal jejunum derived murine intestinal organoid monolayers on Transwells and quantified transepithelial flux using isotope-labeled iron. Inorganic 55Fe showed no clear regional difference, whereas NA-55Fe displayed greater basolateral appearance in proximal jejunum-derived monolayers. This platform enables mechanistic studies of NA-iron complex transport.

physiology↗

Leveraging archaeological specimens to investigate failed invasions: A case study on Okhotsk pigs, northern Japan

Invasive species pose a major threat to biodiversity, yet our understanding of failed invasions/translocations, instances where alien/introduced species fail to establish, remains limited. Investigating the factors behind failed invasions is critical for improving prevention and management strategies for modern biological invasions. Here, we propose a novel framework that utilizes archaeological archives to uncover evidence of failed invasions. We estimated the biological and ecological factors contributing to the failed invasion of pigs from later prehistory to recent times (299 cal BC to 1900 AD) on Rebun Island in far northern Japan by synthesizing the evidence obtained from stable isotopes, zooarchaeology, and historical documents. Despite the anthropogenic introductions of pigs into Rebun Island, pigs did not establish a feral population and disappeared after ca. 1200 AD. We identified reduced propagule pressure, abiotic resistance due to the cold climate, and decreased resources as the three key factors that contributed to the disappearance of pigs. Pigs are one of the most widespread invasive species globally, and this study represents a novel approach to studying failed invasions using archaeological data, which aligns with the framework of conservation paleobiology.

ecology↗

Large-scale brain network differences during deliberate and spontaneous mind-wandering in a sustained attention task: An electroencephalography source-level connectivity study

Mind-wandering (MW), the shift of attention away from an ongoing task, can be classified as either deliberate or spontaneous, depending on whether these internal thoughts arise intentionally or unintentionally. Previous functional magnetic resonance imaging-based resting state studies have shown that spontaneous MW traits are positively correlated with coupling within the default mode network (DMN), whereas deliberate MW traits are positively correlated with coupling both within the DMN and between the DMN and control-or attention-related networks. However, state-based functional connectivity during each MW episode remains unknown. Addressing this knowledge gap, we investigated how deliberate and spontaneous MW differentially involve state-based large-scale network interactions during a sustained attention task using electroencephalography (EEG), which captures rapid network dynamics. Thirty-one participants performed the gradual-onset continuous performance task using 64-channel EEG. Mental states were classified via experience-sampling probes as on-task, deliberate, or spontaneous MW. EEG data from 1-s pre-probe epochs were analyzed using source estimation and the weighted phase lag index to assess functional connectivity within and across the DMN, control network (CN), dorsal attention network (DAN), and salience network (SN) in the delta, theta, alpha, and beta frequency bands. Relative to both spontaneous MW and the on-task state, deliberate MW was characterized by significantly stronger alpha band functional connectivity. A prominent connectivity cluster was centered on the right frontal operculum-insula of the SN, linking regions across the SN, CN, and DMN. In addition, deliberate MW exhibited enhanced SN-DAN-DMN coupling compared with the on-task state. By contrast, spontaneous MW did not show significant connectivity differences relative to the on-task state in any frequency band. Taken together, these results suggest that alpha band network interactions centered on the SN may contribute to the intentional regulation of internally directed thought during deliberate MW.

neuroscience↗

In vivo xenogenic reconstitution of human alveolar epithelial architecture and function

An urgent need exists for lung models that accurately replicate human physiological profiles. We developed a chimeric mouse model enabling targeted ablation of alveolar type 2 (AT2) cells and lung macrophages, creating niches for endoscopically transplanted human induced pluripotent stem cell (hiPSC)-derived lung progenitors (hLPs). These engrafted cells were retained for 24 weeks, demonstrating self-renewal and differentiation potential, surfactant protein secretion, and maintaining alveolar phosphate homeostasis, suggesting their maturation into AT2 cells. Furthermore, transplantation of hLPs derived from disease-specific hiPSCs recapitulated the phenotype of pulmonary alveolar microlithiasis. The architecture, function, and metabolism of human alveolar epithelium were accurately replicated in vivo. This model has the potential to link experimental models and first-in-human studies, facilitating the development of novel therapies for intractable lung diseases.

developmental biology↗

Artificial hibernation uncovers distinct synaptic engram architecture for memory retention

The memory trace at the neuronal and synaptic levels remains controversial. Stable, larger spines are thought to support memory, but the high turnover of dendritic spines and the drifting of neuronal representations following memory formation suggest alternative possibilities. To elucidate a structural trace underlying memory retention, we utilize a mouse model of artificial hibernation. During hibernation, hippocampal neurons exhibited a substantial reduction in their activity and an extensive elimination of dendritic spines and synapses. Despite these changes, their memory and associated hippocampal neuronal representations are intact after arousal. We find that a subset of spines is maintained during hibernation. These spatially clustered engram-engram synapses are exclusively protected from elimination and characterized by synaptic contacts with multi-synaptic boutons. These findings suggest that synaptic engram architecture, rather than larger spines per se, is resilient to network remodeling and underlies long-term memory retention.

neuroscience↗

Structure-guided development of a potent human B0AT1 inhibitor effective in a mouse model of phenylketonuria

B0AT1 is a neutral amino acid transporter responsible for the (re)absorption in the intestine and kidney. Here, we developed small-molecule inhibitors of B0AT1 as a therapeutic strategy to a transient pocket, located [~]17 [A] away from the substrate-binding site and unique to the outward-open conformation, and stabilize an outward-occluded conformation that prevents the conformational transitions required for transport. Guided by structural insights, we optimized an initial inhibitor (Cinromide) to improve potency and cross-species activity, yielding compound 3, which inhibits both human and mouse B0AT1 with submicromolar IC_50 values. In a PKU mouse model (Pahenu2), oral administration of compound 3 increased urinary Phe excretion and significantly reduced plasma Phe. Our findings identify a druggable allosteric site in B0AT1, demonstrate its utility for achieving potent and selective inhibition in vivo, and establish allosteric blockade as a therapeutic approach for PKU and other SLC6-family transporters.

pharmacology and toxicology↗

Wounding activates the HSFA1 transcription factors to promote cellular reprogramming in Arabidopsis

Mechanical injury is a primary trigger for cellular reprogramming during organ regeneration, yet the molecular mechanisms that link wounding to reprogramming remain poorly understood. In this study we identify the Arabidopsis HEAT SHOCK FACTOR A1 (HSFA1) class of transcription factors, being key regulators of the heat stress response, as central players in wound-induced callus formation and shoot regeneration. Loss of HSFA1 function in the hsfa1abd triple mutants severely impairs cellular reprogramming, reducing callus formation from wounded hypocotyls, as well as shoot regeneration from explants. Conversely, overexpression of the HSFA1d gain-of-function variant markedly enhances regeneration. Time-series RNA-seq and ChIP-seq analyses revealed that HSFA1s directly activate the key reprogramming regulators WOUND-INDUCED DEDIFFERENTIATION 1 (WIND1), PLETHORA 3 (PLT3) and ZINC FINGER OF ARABIDOPSIS THALIANA 6 (ZAT6). Furthermore, we demonstrate that HSFA1d activity is attenuated by SIZ1-mediated SUMOylation, linking post-translational modification to the regulation of wound responses. Our findings establish HSFA1s as an early transcriptional hub that integrates wound signals with the activation of a broad gene network that drives cellular reprogramming, thereby providing a mechanistic framework for understanding how stress-responsive transcription factors control regeneration.

plant biology↗

Novel humanized anti-Nav1.7 antibodies with long-lasting, side-effect-free analgesic effects

Neuropathic pain remains difficult to treat effectively because of the limitations of current pain medications. The Nav1.7 sodium channel plays a crucial role in pain sensation. The development of selective inhibitors has been challenging because of the high similarity among Nav channel subtypes. To address this issue, we developed monoclonal antibodies that selectively target Nav1.7 and humanized them for clinical use for the first time. When administered systemically to neuropathic pain model rats, a potent analgesic effect was observed that lasted for at least 96 hours. Electrophysiological studies revealed that the antibody reduced mechanically-evoked and spontaneous neuronal activity in the model. Importantly, the antibodies did not impact physiological pain or motor function. Collectively, our findings suggest that these novel Nav1.7-targeting antibodies are potentially effective analgesic drugs for chronic pain, including neuropathic pain. Our novel humanized anti-Nav1.7 antibodies have the potential to be used for the development of new analgesic, and one such antibody, S-151128 is currently in clinical trial.

pharmacology and toxicology↗

Pseudovirus-Mediated Proximity Labeling Identifies Candidate Host Cell Membrane Proteins Involved in Viral Attachment

Viral infections represent a significant threat to humanity, as exemplified by the COVID-19 pandemic. To mitigate the associated damage, it is essential to understand the biological characteristics of causative viruses. In this study, we report a novel method for identifying host cell molecules (including virus receptor) required for viral attachment, referred to here as "Host Cell Attachment Factors (HCAFs)". Our approach utilizes proximity labeling (PL) technology: pseudoviruses engineered to express a PL enzyme are applied to host cells, where they bind and initiate proximity labeling. Since HCAFs are expected to be localized near viral attachment sites, candidate HCAFs are specifically tagged by the PL process. Analysis of influenza HCAFs enabled the identification of multiple candidate molecules. Subsequent virus attachment experiments using CHO cells suggested that NRP1 may serve as an HCAF for influenza viruses. Given its simplicity and rapid turnaround, this method is adaptable to a wide range of enveloped viruses, including pandemic viruses that require emergency analysis.

microbiology↗

In vivo deep-brain microscopy at submicrometer resolution with refractive index-matched prism interfaces

The mammalian brain is a thick and densely layered structure comprising a huge number of neurons that work together to process information and regulate brain functions. Although various optical methods have been developed to investigate deep brain dynamics, they are limited by technical constraints, invasiveness, suboptimal spatial resolution, and/or a restricted field of view. To overcome these limitations, we developed an implantable, optically optimized microprism interface with a refractive index matched to that of brain tissue and water, enabling minimally-invasive, wide-field two-photon imaging method with enhanced brightness and sub-micron resolution in deep prefrontal areas.

neuroscience↗

Nocturnal intraocular pressure rise is regulated by norepinephrine via RHOB

Intraocular pressure (IOP), a key factor in glaucoma development, is regulated by aqueous humor (AH) dynamics, with inflow from the ciliary body and outflow through the trabecular meshwork (TM). IOP has a circadian rhythm entrained by sympathetic norepinephrine (NE) from the superior cervical ganglion. Herein, we investigated its underlying regulatory mechanisms in the TM. Through comprehensive gene expression analysis of human TM cells and mouse eyes, we identified 18 genes upregulated by NE stimulation, including the small GTPase RAS homologous protein B (RHOB). Promoter assays revealed RHOB upregulation via the cyclic adenosine monophosphate (cAMP) response element on its promotor. NE stimulation for 6-9 h increased RHOB level and cellular adhesion, and suppressed liquid permeability in the TM cells, indicating a time-dependent effect. RHOB deficiency increased TM macrophage phagocytosis and eliminated NE-induced suppression of phagocytosis and permeability, whereas RHOB overexpression had the opposite effect. Instillations of RHO or RHO-kinase inhibitors to mice eye reduced nocturnal and NE-induced IOP elevation. Our findings suggest that NE can elevate IOP via RHOB-mediated inhibition of TM phagocytosis, positioning RHOB as a potential glaucoma treatment target and IOP rhythm regulator.

pathology↗

Golgi retention of KIT in gastrointestinal stromal tumour cells is phospholipase D activity-dependent

A constitutively active mutant of the receptor protein-tyrosine kinase KIT is a major cause of gastrointestinal stromal tumours (GISTs). Recently, we discovered that during biosynthetic transport, the KIT mutant (KITmut) is retained in the Golgi/trans-Golgi network (TGN), where it activates downstream molecules. This retention is dependent on the phospholipase C{gamma}2-protein kinase D2-PI4 kinase III{beta} (PLC{gamma}2-PKD2-PI4KIII{beta}) pathway, which KITmut activates at the Golgi/TGN. The activated cascade aberrantly recruits GGA1 and the {gamma}-adaptin subunit of AP1, resulting in KITmut retention in the Golgi/TGN. However, the precise mechanisms, including the mediators and effectors in the pathway, remain unclear. In humans, the phosphatidic acid-generating enzymes, phospholipase D1 (PLD1) and PLD2, are known downstream proteins of PKD. In the presence of the PLD inhibitor CAY10594, KITmut is released from the Golgi/TGN and subsequently degraded in lysosomes, leading to signal inactivation. Knockdown experiments indicated that PLD2 plays a role in KITmut retention. KITmut activates PLD2 through PKD2, but not PI4KIII{beta}, for Golgi/TGN retention. PLD activity is required for the association of {gamma}-adaptin with GGA1. Therefore, the KIT-PLC{gamma}2-PKD2 pathway separately activates PLD2 and PI4KIII{beta} to recruit {gamma}-adaptin and GGA1. Collectively, these results suggest that KITmut retention is dependent on the activation of the PLC{gamma}2-PKD2-PLD2 cascade in GIST.

cell biology↗

Differential O-Glc elongation on the specific EGF repeat within a ligand binding domain regulates NOTCH1 signaling

Three types of O-linked glycosylation - O-glucose, O-fucose, and O-N-acetylglucosamine - are crucial for the function of Notch receptors, which regulates critical cell fate determination processes in a wide variety of contexts. O-Glucose glycans are added to serine residues located between the first and second conserved cysteines within the epidermal growth factor (EGF) -like repeats in the Notch extracellular domain. Previously, O-glucose glycans were shown to be extended to a trisaccharide structure with two xyloses via an 1-3 linkage. Our recent studies, however, indicated that the O-glucose glycan on NOTCH1 EGF10 can be extended by hexose and Neu5Ac. Here, we demonstrated that this hexose- and Neu5Ac-extended glycan has a 3-sialyllactose-like structure synthesized by specific members of two isoenzyme families, B4GALT1 and ST3GAL4. Using mass spectrometry, we identified this modification exclusively on NOTCH1 EGF10 and NOTCH3 EGF9 (equivalent to NOTCH1 EGF10), with no detection in any other EGF domains in NOTCH1-3. Sequence comparison and mutagenesis experiments identified one amino acid at position -2 of the fourth cysteine in the EGF domain as crucial for the galactose elongation of O-glucose glycans. We further demonstrated that this site-specific elongation of O-glucose on NOTCH1 EGF10 significantly impact ligand binding and signal transduction of NOTCH1. Our findings contribute to the understanding of the intricate regulatory mechanisms of Notch receptor function mediated by distinct positions and structures of O-glycans. Significance StatementNotch, a signaling receptor critical for development, differentiation, and homeostasis in multicellular organisms, undergoes multiple post-translational glycan modifications to regulate its function. While O-glucose glycan elongation by xylose was previously known, we identified an O-glucose glycan extended by galactose and Neu5Ac on specific epidermal growth factor (EGF) -like repeats of certain Notch paralogs, NOTCH1 and NOTCH3. As far as we know, this structure has not been reported on any other proteins. We identify the enzymes involved in the biosynthesis of this glycan and demonstrate that modifications at a specific site on Notch direct receptor functions, including ligand binding and Notch signaling.

biochemistry↗

Fatty acyl-CoA reductase FAR1 is essential for testicular seminolipid synthesis, spermatogenesis, and male fertility

Seminolipids are testis-specific ether glycolipids that are important for spermatogenesis. The fatty alcohol (ether-linked alkyl moiety) in ether lipids is generated from an acyl-CoA by fatty acyl-CoA reductase (FAR). To date, the diversity of the alkyl and acyl moieties in seminolipids, the specific stage of spermatogenesis during which seminolipids are produced, and the FAR isozyme (FAR1 or FAR2) involved in the synthesis of the alkyl moieties have remained largely unclear. Here, we demonstrated that Far1 is expressed in the mouse testis via quantitative RT-PCR analysis, whereas Far2 was barely detectable. In situ hybridization and quantitative RT-PCR analysis of spermatogenic cells separated via FACS revealed that Far1 is expressed in spermatogonia, spermatocytes, and spermatids. We generated Far1 knockout (KO) mice and found that male Far1 KO mice were infertile. In these mice, sperms were absent in the epididymides and the testes were small, with multinucleated cells and vacuoles in the seminiferous tubules. LC-MS/MS analysis showed that the vast majority of seminolipids (> 90%) in wild-type mouse testes contained C16:0 in both the alkyl and the acyl moieties. Seminolipids were present in all subclasses of spermatogenic cells in wild-type mice, but they were absent in Far1 KO mice. Instead, the production of non-ether, diacyl-type sulfogalactosyl lipids (sulfogalactosyl diacylglycerols) was induced in Far1 KO mice. In conclusion, the alkyl and acyl moieties of seminolipids in the testis are low in diversity, and Far1 is essential for seminolipid synthesis and spermatogenesis.

biochemistry↗

Effect of environmental conditions on seed germination and seedling growth in Cuscuta campestris

The dodder, Cuscuta, is an obligate parasitic plant that cannot survive without a host plant and causes major damage to crop yields. To know its growth characteristics before parasitism, we examined the effect of various environmental conditions on seed germination and seedling growth in Cuscuta campestris. As for the effect of light on germination, far-red light was rather preferable to red light and the reversible response of the seeds to red and far-red light was confirmed, implicating a phytochrome-mediated signaling opposite to that in many seed plants. Among amino acids, aspartic acid and alanine had a promotive effect and histidine had an inhibitory effect on germination. We further found that, in addition to gibberellic acid, methyl jasmonate was stimulatory to germination and shoot elongation. While 2,4-D extended the viability of trichomes around the root cap, kinetin induced the formation of scale leaves on the shoot and calli at the base of the shoot and the root tip. RT-PCR experiments confirmed that expression of a putative RbcS gene for photosynthesis showed no response to light but that of a Phytochrome A homolog was increased in the dark. Our results indicate that some of the molecular mechanisms to respond to light and hormone signals are uniquely modified in dodder seedlings, providing a clue for understanding the survival strategy of parasitic plants.

plant biology↗

Oxidized low-density lipoprotein potentiates angiotensin II-induced Gq activation through the AT1-LOX1 receptor complex: Implications for renal dysfunction

Chronic kidney disease (CKD) and atherosclerotic heart disease, frequently associated with dyslipidemia and hypertension, represent significant health concerns. We investigated the interplay among these conditions, focusing on the role of oxidized low-density lipoprotein (oxLDL) and angiotensin II (Ang II) in renal injury via G protein q subunit (Gq) signaling. We hypothesized that oxLDL enhances Ang II-induced Gq signaling via the AT1 (Ang II type 1 receptor)-LOX1 (lectin-like oxLDL receptor) complex. Based on CHO and renal cell model experiments, oxLDL alone did not activate Gq signaling. However, when combined with Ang II, it significantly potentiated Gq-mediated inositol phosphate 1 production and calcium influx in cells expressing both LOX-1 and AT1 but not in AT1-expressing cells. This suggests a critical synergistic interaction between oxLDL and Ang II in the AT1-LOX1 complex. Conformational studies using AT1 biosensors have indicated a unique receptor conformational change due to the oxLDL-Ang II combination. In vivo, wild-type mice fed a high-fat diet with Ang II infusion presented exacerbated renal dysfunction, whereas LOX-1 knockout mice did not, underscoring the pathophysiological relevance of the AT1-LOX1 interaction in renal damage. These findings highlight a novel mechanism of renal dysfunction in CKD driven by dyslipidemia and hypertension and suggest the therapeutic potential of AT1-LOX1 receptor complex in patients with these comorbidities.

molecular biology↗