Biology subjects

Kimura, Y.

Publications and source records attributed to Kimura, Y..

At least 19 recordsLinked to original sources

bioRxiv2026

Non-cell-autonomous removal of protein aggregates via trogocytosis

Protein aggregate formation can cause cell damage and contribute to tissue pathologies including neurodegeneration. Protein aggregates are normally eliminated by cell-intrinsic mechanisms of lysosomal (autophagic) degradation. However, degradative capacity varies between cell types, raising the possibility that high-capacity cell types, such as macrophages, may contribute to aggregate disposal from the low-capacity cells. Here, we show that cellular protein aggregates are removed by macrophages via trogocytosis -- a partial engulfment of the target cells. Lysosomal stress upon protein aggregate accumulation promotes cell surface expression of the transmembrane isoform of the macrophage growth factor CSF1 (tmCSF1), which is detected by macrophages through the CSF1 receptor to drive trogocytosis. Insufficient or impaired degradation of protein aggregates in lysosomes results in their transport along microtubules to the plasma membrane where they physically associate with tmCSF1. This enables macrophages to specifically trogocytose protein aggregates. These findings reveal a protein homeostasis system that eliminates protein aggregates in a non-cell-autonomous manner.

cell biology↗

bioRxiv2026

Generalized Morphogenesis Theory: A Flow-Inertia Modeling Framework for Cross-Scale Dynamics of Dissipative Structures

Understanding structural similarities across dynamical systems at different scales remains a central problem in nonlinear science [1, 3]. Here we propose a modeling framework for cross-scale morphogenetic dynamics, termed Generalized Morphogenesis Theory (GMT), based on a flow-inertia formulation: O_FD O_INLINEFIG[Formula 1]C_INLINEFIGM_FD(1)C_FD where S denotes system state, E environmental input, F (E, S) a driving function, and {micro}(S) an inertia function representing resistance to change. This formulation provides a structural representation that encompasses several classical dynamical models--including Newtonian relaxation, logistic growth, and reaction-diffusion systems [13]--under appropriate parameterizations. Non-dimensionalization reveals a small set of control parameters governing regime transitions. Empirical validation is performed across two independent scales. At the organism scale, crop growth time-series datasets from multiple species exhibit consistent multiplicative dynamics F (E, S) = f (E) {middle dot} S, statistically preferred over additive alternatives in 5 of 6 independently tested systems ({Delta}AIC ranging from +2 to +891; R2 up to 0.98). Independently estimated inertia time constants agree in two plant systems (cucumber:{tau} = 3.7 days, CV=3.3%; maize:{tau} = 36.8 days, CV=17.3%), with the 10-fold ratio consistent with structural complexity differences. At the molecular scale, publicly available perturbation transcriptomics datasets (Perturb-seq) show directional response structures consistent with the proposed flow-inertia decomposition (93% causal direction agreement across three independent datasets; p < 10-25). Across domains, recurrent dynamical motifs are organized into 12 canonical design patterns, derived from a 2 x 2 x 3 orthogonal structure (4 elementary operations x 3 temporal scales), associated with stability classes and bifurcation conditions. These results suggest that the flow-inertia formulation functions as a domain-independent structural modeling principle for dissipative morphogenesis.

systems biology↗

bioRxiv2026

Dopamine shapes brain metastate dynamics

Dopamines influence on large-scale network dynamics, especially on the default mode network (DMN), remains uncertain, as fMRI studies have produced mixed results. One likely contributor to these discrepancies is reliance on traditional functional connectivity analyses, which typically derive a single metric (e.g., the Pearson correlation coefficient) from the entire time series and thus fail to capture network dynamics. To address this issue, we combined a dopaminergic challenge (mazindol, a dopamine transporter [DAT] reuptake inhibitor), PET, resting-state fMRI, and hidden Markov modeling (HMM) to characterize time-varying alterations in human large-scale functional networks following acute DAT blockade. We found that mazindol-induced increases in endogenous dopamine altered the balance between the brains functional "metastates," two recurrent higher-order network configurations that each encompass multiple HMM-derived brain states. Mazindol increased the time participants spent in an internally oriented cognitive metastate and decreased the time spent in a sensorimotor-perceptual metastate, with the DMN showing the most pronounced lengthening. In exploratory analyses, declines in [{superscript 1}{superscript 1}C]raclopride binding, a PET index of D2 dopamine receptor availability reflecting increased striatal extracellular dopamine levels, tended to show a positive correlation with the prolongation of these cognitive states. These findings indicate that dopamine is closely linked to shifts from sensorimotor and perceptual to cognitive brain metastates, potentially underpinning the prioritization of internally oriented over externally driven psychological processes. Our results highlight the importance of dynamic, time-resolved connectivity approaches for understanding neuromodulatory actions in the human brain and suggest that dopamine helps regulate the dynamic balance between functionally competing large-scale brain networks.

neuroscience↗

bioRxiv2026

Microglial Lag3 Drives α-Synuclein--induced Neurotoxic Activated (A1) Astrocytes and Neurodegeneration

BackgroundNeuroinflammation and pathologic -synuclein (-syn) aggregation cooperate to drive dopaminergic neurodegeneration in Parkinsons disease, but the glial receptors that couple extracellular -syn to inflammatory cascades remain incompletely defined. Microglia express higher levels of lymphocyte activation gene 3 (Lag3) than neurons, yet the contribution of microglial Lag3 to -syn recognition, glial crosstalk, and neurodegeneration is unknown. MethodsBiochemical binding assays, live-cell imaging, cytokine profiling, and neuron-microglia-astrocyte co-culture paradigms were used to define Lag3-dependent -syn preformed fibril (PFF) binding, uptake, and microglial activation. To interrogate in vivo function, microglia-specific Lag3 conditional knockout mice (Lag3L/L-Cx3cr1CreER) and littermate controls received unilateral intrastriatal -syn PFF injections, followed by histological, biochemical, and behavioral assessments of -syn pathology, gliosis, nigrostriatal integrity, and motor performance. Results-syn PFFs bound microglial Lag3 with high specificity and nanomolar affinity and required Lag3 for efficient fibril internalization and induction of proinflammatory cytokines. Microglial Lag3 deficiency markedly blunted -syn PFF-evoked microglial activation, prevented cytokine-driven conversion of astrocytes into neurotoxic reactive A1 astrocytes, and abolished astrocyte-dependent neuronal death in vitro. In vivo, microglia-specific Lag3 deletion reduced cortical, striatal, and substantia nigra pS129 -syn pathology, suppressed microgliosis and A1 astrocyte induction, preserved substantia nigra dopaminergic neurons and striatal dopamine transporter/tyrosine hydroxylase expression, and ameliorated -syn PFF-induced motor deficits. ConclusionsThis study identifies microglial Lag3 as a key receptor linking extracellular -syn PFF recognition to inflammatory amplification, neurotoxic reactive A1 astrocyte conversion, and dopaminergic neurodegeneration. Together with prior work on neuronal Lag3, these findings support a cell-type-specific dual-axis model in which neuronal Lag3 mediates -syn propagation while microglial Lag3 drives glia-dependent neurotoxicity, positioning Lag3 as a promising precision therapeutic target in -synucleinopathies.

neuroscience↗

bioRxiv2025

Sigma-1 Receptor Promotes Glycolysis in Neuronal Systems by Suppressing GRIM19

Sigma-1 receptor (S1R) is a Ca2+ sensitive, ligand-operated receptor chaperone protein present on the endoplasmic reticulum (ER) membrane and more specifically at the mitochondria-associated ER membrane (MAM). Upon activation by ER calcium depletion or ligand binding, S1R can increase calcium efflux from the ER into the mitochondria by chaperoning IP3 receptor type3 (Ip3R3). Mitochondrial metabolism has an intricate relationship with glycolysis. Despite S1R affecting mitochondria, the relevance of S1R to glycolysis and its impact on the overall cellular energy metabolism is not known. This study utilizes wild-type (Wt) and S1R knockout (S1R KO) Neuro2a (N2a) cells and Wt and S1R KO mice for primary culture of cortical neurons studies and longitudinal in-vivo imaging. In this manuscript we describe the fundamental functions of S1R on glycolysis, mitochondrial activity and NAD+/NADH metabolism, keystone coenzymes essential for glycolysis and for mitochondrial activity. Both N2a cells and cortical neurons lacking S1R had reduced glycolytic activity, and increased mitochondria complex I protein GRIM19 but no change in mitochondrial oxygen consumption. Furthermore, we observed an increased NAD+/NADH ratio in S1R KO condition. Positron emission tomography revealed decreased [18F]fluorodeoxyglucose brain uptake in S1R KO mice. We observed that knocking down GRIM19 in S1R KO condition rescued the glycolysis deficit. Altogether, these data show for the first time that S1R modulates glycolysis and NAD metabolism in various neuronal systems. This new insight on the S1R function may lead to new therapeutic applications of S1R ligands where compromised glycolysis and cellular NAD+/NADH ratios occur such as aging and neurodegeneration.

cell biology↗

bioRxiv2025

The glomerulus as a selective gate for tumor-derived extracellular vesicles in urine

Urinary small extracellular vesicles (sEVs), which can reflect systemic conditions, hold great promise for non-invasive cancer diagnostics, yet the mechanism by which tumor-derived sEVs reach urine remains unclear. Here, we demonstrate that the glomerulus actively transcytoses circulating tumor-derived sEVs into urine. Using CRISPR gRNA-tagged glioma sEVs and bioluminescent/fluorescent GeNL-tagged lung and pancreatic cancer sEVs, we tracked their journey from tumors to urine in multiple mouse models. In vivo and in vitro analyses revealed endocytic uptake and transcytotic release by glomerular cells, accompanied by changes in sEV size and surface composition. GeNL-tagged sEVs consistently showed higher signals in urine than plasma, indicating selective excretion. These findings redefine the glomerulus as a dynamic regulator of EV processing and establish a mechanistic foundation for urinary liquid biopsy.

cancer biology↗

bioRxiv2024

Neutralizing antibody evasion of SARS-CoV-2 JN.1 derivatives KP.3, KP.3.1.1, LB.1, and XEC

The emergence of SARS-CoV-2 variants poses ongoing challenges to vaccine efficacy. We evaluated neutralizing antibody responses against JN.1 and its derivatives (KP.3, KP.3.1.1, LB.1, and XEC) in healthcare workers who received seven doses of BNT162b2, including XBB.1.5 monovalent vaccine. In COVID-19-naive individuals, KP.3.1.1 and LB.1 showed substantial immune escape, while previously infected individuals maintained neutralization activity against all variants. We also demonstrated that JN.1-based immunization induces robust cross-neutralizing activity against emerging variants. A single amino acid deletion at position 31 in the spike protein significantly impacted immune evasion. These findings support the potential effectiveness of JN.1-based vaccines while highlighting the need for continued surveillance and vaccine optimization.

immunology↗

bioRxiv2024

BLOC: buildable and linkable organ on a chip

Microphysiological systems (MPSs) are attractive alternatives to animal experiments in physiology, pathophysiology, and drug development. However, conventional MPSs are designed for specific applications and have low versatility and scalability. Here, we developed a "Buildable and Linkable Organ on a Chip" (BLOC) to construct diverse MPSs. The Culture, Control, and Analysis BLOCs were standardized to the same size and linked using inlet/outlet joints for perfusion. Radiation-induced chemical reactions were used to suppress the adsorption and absorption of small hydrophobic molecules by BLOCs composed of polydimethylsiloxane. BLOCs for 2D/3D culture could also encapsulate radiation-crosslinked protein hydrogels with designed stiffness and microtopography to mimic the microenvironment in vivo. A perfusion device connecting Culture BLOCs was designed for a toxicity assay mimicking the systemic circulation using six types of organoids. An automatic enzyme-linked immunosorbent assay device connecting Culture, Control, and Analysis BLOCs detected proteins released from organoids. BLOCs, which users can freely configure to suit their needs, is expected to become powerful tools in basic research and preclinical trials using MPSs.

bioengineering↗

bioRxiv2024

Fabrication, evolution, and mutual conversion of D-fucose-activatable and -repressible acetyltransferase upon mutations

The fusion of different proteins can result in the linkage-dependent emergence of molecular switches. In cases where allosteric regulation is designed between the input and output modules of fusion proteins, it is hard to predict whether on-switching or off-switching will occur. However, binding-induced folding, a non-allosteric molecular switch mechanism, has the potential to quickly establish a mutually regulatory relationship between the two fused proteins, in the way whether on-switching or off-switching will occur would be predictable. We inserted chloramphenicol acetyltransferase (CAT) from E. coli into a loop of a D-fucose-responsive mutant of transcription factor AraC, using linker libraries with various lengths. We found that on-switches tend to emerge when two proteins are fused with a small pitch gap at the junction, while fusion designs with a large pitch gap result in the frequent emergence of off-switches. Both types of switches rapidly evolved their switching efficiency upon mutations, establishing the D-fucose-on and -off regulation of CAT activity without disrupting the D-fucose-inducible logic of AraC function. To our surprise, both one-input/two-output split gates thus obtained could be easily inter-converted upon mutations. Through mutations, proteins not only frequently acquire properties as binding-induced folders, but also rapidly establish and evolve a mutual regulatory relationship with unrelated fusion partners, as well as transform their regulatory logic.

synthetic biology↗

bioRxiv2023

The vestibulospinal nucleus is a locus of balance development

Mature vertebrates maintain posture using vestibulospinal neurons that transform sensed instability into reflexive commands to spinal motor circuits. Postural stability improves across development. However, due to the complexity of terrestrial locomotion, vestibulospinal contributions to postural refinement in early life remain unexplored. Here we leveraged the relative simplicity of underwater locomotion to quantify the postural consequences of losing vestibulospinal neurons during development in larval zebrafish of undifferentiated sex. By comparing posture at two timepoints, we discovered that later lesions of vestibulospinal neurons led to greater instability. Analysis of thousands of individual swim bouts revealed that lesions disrupted movement timing and corrective reflexes without impacting swim kinematics, and that this effect was particularly strong in older larvae. Using a generative model of swimming, we showed how these disruptions could account for the increased postural variability at both timepoints. Finally, late lesions disrupted the fin/trunk coordination observed in older larvae, linking vestibulospinal neurons to postural control schemes used to navigate in depth. Since later lesions were considerably more disruptive to postural stability, we conclude that vestibulospinal contributions to balance increase as larvae mature. Vestibulospinal neurons are highly conserved across vertebrates; we therefore propose that they are a substrate for developmental improvements to postural control. SIGNIFICANCE STATEMENTMany animals experience balance improvements during early life. Mature vertebrates use vestibulospinal neurons to transform sensed instability into postural corrections. To understand if/how these neurons shape postural development, we ablated them at two developmentally important timepoints in larval zebrafish. Loss of vestibulospinal neurons disrupted specific stabilizing behaviors (swim timing, tilt correction, and fin/body coordination) more profoundly in older fish. We conclude that postural development happens in part by changes to vestibulospinal neurons -- a significant step towards understanding how developing brains gain the ability to balance.

neuroscience↗

bioRxiv2023

Mutational destabilisation accelerates the evolution of novel sensory and network functions

Binding-induced folding1-4 (BIF) is a promising mechanism that can be used to rapidly convert binders into sensors/regulators without allosteric design. Here we showed that allosteric regulatory proteins AraC can acquire BIF mechanism without compromising their inherent allosteric mechanisms, with high frequency upon mutations. This opened an opportunity to compare the evolutionary capacity of the allosteric and non-allosteric modes of a specific sensory protein. We found that AraC evolved novel sensory function far more rapidly in BIF mode than in allosteric mode. This newly acquired (non-allosteric) sensory function is distinguishable both in its response logic and in sensitivity from original (allosteric) one, and they can be operated simultaneously, independently, and cooperatively, allowing the construction of complex regulatory networks behaviours such as a selective NIMPLY/OR converter and width-tuneable band-pass filter. Together with its high frequency of emergence, BIF can be an overlooked evolutionary driver of the invention of novel biosensors and complex regulatory networks in nature and laboratory.

synthetic biology↗

bioRxiv2023

Macrophages sense ECM mechanics and growth factor availability through cytoskeletal remodeling to regulate their tissue repair program

Tissue resident macrophages play important roles in tissue homeostasis and repair. However, how macrophages monitor and maintain tissue integrity is not well understood. The extracellular matrix (ECM) is a key structural and organizational component of all tissues. Here, we find that macrophages sense the mechanical properties of the ECM in order to regulate a specific tissue repair program. We show that macrophage mechanosensing is mediated by cytoskeletal remodeling and can be performed in three-dimensional environments through a non-canonical, integrin-independent mechanism analogous to amoeboid migration. We find that these cytoskeletal dynamics also integrate biochemical signaling by CSF1 and ultimately regulate chromatin accessibility to control the mechanosensitive gene expression program. This study suggests a distinct mode of ECM mechanosensing and growth factor signaling through which macrophages may regulate tissue repair and fibrosis.

immunology↗

bioRxiv2023

Pathological Tau transmission initiated by binding lymphocyte-activation gene 3

The spread of prion-like protein aggregates is believed to be a common driver of pathogenesis in many neurodegenerative diseases. Accumulated tangles of filamentous Tau protein are considered pathogenic lesions of Alzheimers disease (AD) and related Tauopathies, including progressive supranuclear palsy, and corticobasal degeneration. Tau pathologies in these illnesses exhibits a clear progressive and hierarchical spreading pattern that correlates with disease severity1, 2. Clinical observation combined with complementary experimental studies3, 4 have shown that Tau preformed fibrils (PFF) are prion-like seeds that propagate pathology by entering cells and templating misfolding and aggregation of endogenous Tau. While several receptors of Tau are known, they are not specific to the fibrillar form of Tau. Moreover, the underlying cellular mechanisms of Tau PFF spreading remains poorly understood. Here, we show that the lymphocyte-activation gene 3 (Lag3) is a cell surface receptor that binds to PFF, but not monomer, of Tau. Deletion of Lag3 or inhibition of Lag3 in primary cortical neurons significantly reduces the internalization of Tau PFF and subsequent Tau propagation and neuron-to-neuron transmission. Propagation of Tau pathology and behavioral deficits induced by injection of Tau PFF in the hippocampus and overlying cortex are attenuated in mice lacking Lag3 selectively in neurons. Our results identify neuronal Lag3 as a receptor of pathologic Tau in the brain, and for AD and related Tauopathies a therapeutic target. One Sentence SummaryLag3 is a neuronal receptor specific for Tau PFF, and is required for uptake, propagation and transmission of Tau pathology.

neuroscience↗

bioRxiv2023

In depth amino acid mutational analysis of the key interspecific incompatibility transmembrane factor Stigmatic Privacy 1

O_LIIn plants, there is an active prezygotic interspecific-incompatibility mechanism to prevent unfavorable hybrids between two species. We previously reported that an uncharacterized protein with four-transmembrane domains, named as Stigmatic Privacy 1 (SPRI1), is responsible for rejecting hetero-specific pollen grains in Arabidopsis thaliana. C_LIO_LIWe have conducted a functional study of the SPRI1 protein, via point-mutational experiments and biochemical analysis. We studied the molecular regulatory mechanisms of SPRI1 and the relationships with its function. C_LIO_LIThe alanine- and glycine-scanning experiments together with the evolutional analysis showed that the structural integrity of the C-terminal regions of the extracellular domain of this protein is important for its function. In addition, we found two cysteines (C67 and C80) within the extracellular domain that may be involved in the formation of intermolecular disulfide bonds. SPRI1 may form homo-multimers and is present as part of a ca. 300 kDa complex. C_LIO_LIOur present study indicates that molecular complex formation ability of SPRI1 may be important to maintain its stability and interspecific incompatibility functions in cells. C_LI

plant biology↗

bioRxiv2023

Gravitational and mechanical forces drive mitochondrial translation through the cell adhesion-FAK axis

Life on Earth has evolved in a form suitable for the gravitational force of 1 x g. Although the pivotal role of gravity in gene expression has been revealed by multiomics approaches in space-flown samples and astronauts, the molecular details of how mammalian cells harness gravity have remained unclear. Here, we showed that mitochondria utilize gravity to activate protein synthesis within the organelle. Genome-wide ribosome profiling revealed reduced mitochondrial translation in mammalian cells and Caenorhabditis elegans under both microgravity at the International Space Station and simulated microgravity in a 3D-clinostat on the ground. We found that attenuation of cell adhesion through laminin-integrin interactions causes the phenotype. The downstream signaling pathway including FAK, RAC1, PAK1, BAD, and Bcl-2 family proteins in the cytosol, and mitochondrial fatty acid synthesis (mtFAS) pathway in the matrix maintain mitochondrial translation at high level. Mechanistically, a decreased level of mitochondrial malonyl-CoA, which is consumed by activated mtFAS, leads to a reduction in the malonylation of the translational machinery and an increase in the initiation and elongation of in organello translation. Consistent with the role of integrin as a mechanosensor, we observed a decrease in mitochondrial translation via the minimization of mechanical stress in mouse skeletal muscle. Our work provides mechanistic insights into how cells convert gravitational and mechanical forces into translation in an energy-producing organelle.

molecular biology↗

bioRxiv2023

Physicochemical properties of the vacuolar membrane and cellular factors determine formation of vacuolar invaginations

Vacuoles change their morphology in response to stress. In yeast exposed to chronically high temperatures, vacuolar membranes get deformed and invaginations are formed. We show that phase-separation of vacuolar membrane occurred after heat stress leading to the formation of the invagination. In addition, Hfl1, a vacuolar membrane-localized Atg8-binding protein, was found to suppress the excess vacuolar invaginations after heat stress. At that time, Hfl1 formed foci at the neck of the invaginations in wild-type cells, whereas it was efficiently degraded in the vacuole in the atg8{Delta} mutant. Genetic analysis showed that the endosomal sorting complex required for transport (ESCRT) machinery was necessary to form the invaginations irrespective of Atg8 or Hfl1. In contrast, a combined mutation with the vacuole BAR domain protein Ivy1 led to vacuoles in hfl1{Delta}ivy1{Delta} and atg8{Delta}ivy1{Delta} mutants having constitutively invaginated structures; moreover, these mutants showed stress-sensitive phenotypes. Our findings suggest that vacuolar invaginations result from the combination of changes in the physiochemical properties of the vacuolar membrane and other cellular factors. Summary statementVacuolar invaginations occur through a combination of the changes of physiochemical properties of the vacuolar membrane and other cellular factors in yeast. Particularly, Hfl1 suppresses the excess invaginations.

cell biology↗

bioRxiv2022

Enhanced mTORC1 signaling and Protein Synthesis in Parkinson Disease Pathogenesis

Pathologic -syn destabilizes the TSC 1 and 2 complex leading to mTORC1 activation, enhanced protein translation and neurodegeneration in PD. AbstractPathological -synuclein (-syn) plays an important role in the pathogenesis of -synucleinopathies such as Parkinsons disease (PD). Disruption of protein homeostasis is thought be central to PD pathogenesis, however the molecular mechanism of this deregulation is poorly understood. Here we report that pathologic -syn binds to tuberous sclerosis protein (TSC) 2 and destabilizes the TSC1-TSC2 complex leading to activation of the mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) and enhanced mRNA translation. Dopamine neuron loss, behavioral deficits and aberrant biochemical signaling in the -syn preformed fibril (PFF) and Drosophila -syn transgenic models of pathologic -syn induced degeneration were attenuated by genetic and pharmacologic inhibition of mTOR and protein translation. Our findings establish a potential molecular mechanism by which pathologic -syn activates mTORC1 leading to enhanced protein translation and concomitant neurodegeneration in PD.

neuroscience↗

bioRxiv2022

Plastic loss of motile cilia in the internal gills of Polypterus in response to high CO2 or terrestrial environments

The evolutionary transition of vertebrates from water to land during the Devonian period was accompanied by major changes in animal respiratory systems in terms of physiology and morphology. Indeed, the fossil record of the early tetrapods has revealed the existence of internal gills, which are vestigial fish-like traits used underwater. However, the fossil record provides only limited data on the process of the evolutionary transition of gills from fish to early tetrapods. This study investigated the gills of Polypterus senegalus, a basal ray-finned/amphibious fish which shows many ancestral features of stem Osteichthyes. Based on scanning electron microscopy observations and transcriptome analysis, the existence of motile cilia in the gills was revealed which may create a flow on the gill surface leading to efficient ventilation or remove particles from the surface. Interestingly, these cilia were observed to disappear after rearing in terrestrial or high CO2 environments, which mimics the environmental changes in the Devonian period. The cilia re-appeared after being returned to the original aquatic environment. The ability of plastic changes of gills in Polypterus revealed in this study may allow them to survive in fluctuating environments, such as shallow swamps. The ancestor of Osteichthyes is expected to have possessed such plasticity in the gills, which may be one of the driving forces behind the transition of vertebrates from water to land.

evolutionary biology↗