Biology subjects

Takahashi, N.

Publications and source records attributed to Takahashi, N..

At least 19 recordsLinked to original sources

bioRxiv2026

N-terminal intrinsically disordered region mediates self-catalytic interfacial nucleation of Aspergillus oryzae hydrophobin RolA

Hydrophobins are biosurfactant proteins that coat the cell surfaces of filamentous fungi. On the conidial surface, hydrophobins self-assemble into rodlets, forming a dense hydrophobic film that promotes air-dispersibility. Although rodlet formation is closely associated with the physiology of filamentous fungi, its underlying molecular mechanisms remain largely unknown. Previously, we revealed that RolA, a hydrophobin derived from Aspergillus oryzae, forms rodlets at the air-water interface. In this study, we focused on the flexible N-terminal region of RolA, which lacks a well-defined tertiary structure, and hypothesized that this intrinsically disordered region regulates rodlet formation. To investigate its role, we used RolA mutants with reduced charges in the N-terminal region and analyzed the rodlet formation process on the surface of a water-in-air sessile droplet using atomic force microscopy. In addition, we quantitatively characterized rodlet formation at the air-water interface by applying a kinetic perspective to the interfacial tension change profiles obtained from dynamic surface tension measurements. The results suggested that RolA first forms a monolayer at the air-water interface, then rodlet formation proceeds through the continuous supply of free RolA monomers from the bulk phase to the interfacial RolA film. Our molecular dynamics simulations of RolA at the interface supported a model in which RolA molecules within the interfacial film interact with free monomers in the bulk phase through their N-terminal regions. These results reveal a previously unidentified role of the N-terminal region in rodlet formation and provide a more comprehensive framework for understanding the molecular mechanism underlying RolA rodlet formation.

biophysics↗

bioRxiv2026

Ocular Safety and Efficacy of AAV-mediated Tyrosinase Gene Augmentation in a Nonhuman Primate Model

PurposeOculocutaneous albinism type 1 (OCA1) is an inherited disorder caused by tyrosinase (TYR) gene mutations. Affected individuals experience visual impairment and severe photosensitivity from ocular hypomelanosis, with no current treatments. We evaluated the safety and efficacy of a TYR-encoding adeno-associated virus (AAV) vector in healthy rhesus macaques as a potential OCA1 treatment. MethodsA novel AAV2-based capsid (ATX002) was packaged with the human VMD2 promoter and TYR (hTYR) fused with mGreenLantern (mGL). Two adult rhesus macaques were injected with ATX002-hVMD2-hTYR-mGL subretinally (OD) and intravitreally (OS). Safety and efficacy were assessed via comprehensive ophthalmic examination, fundus photography, spectral-domain optical coherence tomography (SD-OCT), and full-field electroretinography at baseline and defined timepoints up to 12 weeks post-injection, followed by post-mortem immunohistochemistry (IHC). ResultsBoth subretinal doses induced localized hypermelanosis by 3 weeks post-injection, which persisted through the study endpoint and was accompanied by measurable thickening of the retinal pigment epithelium (RPE) on SD-OCT. Histological IHC confirmed successful RPE transduction via robust mGL fluorescence, corroborating in vivo findings by revealing localized RPE hyperplasia and transgene-expressing cells adjacent to regions of de novo hypermelanosis. Intravitreal delivery did not induce any changes to the RPE. Transient uveitis was observed but successfully managed with anti-inflammatory treatment. ConclusionsSubretinal AAV-TYR delivery is a safe and effective approach with the potential to induce RPE pigmentation. These findings support the use of AAV-TYR gene therapy for OCA1, demonstrating efficacy and a manageable safety profile in a large-animal model, and provide a critical bridge toward human clinical translation.

bioengineering↗

bioRxiv2026

Gingipain-containing products from Porphyromonas gingivalis promote epithelial CCL20 signaling and γδ T-cell accumulation in COPD-like airways

Chronic obstructive pulmonary disease (COPD) is a progressive inflammatory airway disease in which impaired mucosal barrier function may increase susceptibility to aspirated oral microbial products. Periodontal disease has been associated with COPD development and exacerbation, but the epithelial mechanisms linking periodontal pathogens to pulmonary immune remodeling remain unclear. Here, we investigated whether gingipain-containing Porphyromonas gingivalis culture supernatant (PCS) promotes {gamma}{delta} T-cell-associated inflammation in COPD-like airways. Repeated intratracheal administration of PCS to {beta}ENaC-transgenic mice induced airway-centered immune cell accumulation and increased {gamma}{delta} TCR-positive cell accumulation, together with elevated expression of the {gamma}{delta} T-cell-associated cytokines Ifng and Il17a. PCS also increased pulmonary Ccl20 and Ccr6 expression, whereas epithelial alarmin-related genes and M2 macrophage-associated responses were not induced in parallel. In ENaC-overexpressing human airway epithelial cells, PCS induced CCL20 and F2RL1, the gene encoding protease-activated receptor 2 (PAR-2), and reduced the N-terminal PAR-2 signal, consistent with proteolytic receptor cleavage. Direct PAR-2 activation reproduced CCL20 induction, whereas pharmacological PAR-2 inhibition suppressed PCS-induced CCL20 expression. In contrast, PAR-1 inhibition or LPS neutralization with polymyxin B did not suppress this response. These findings support a mucosal epithelial protease-sensing model in which gingipain-containing P. gingivalis products activate PAR-2-dependent CCL20 production in airway epithelial cells and are associated with CCR6-linked {gamma}{delta} T-cell accumulation in COPD-like airways. Contribution to the field statementPeriodontal disease is often associated with chronic obstructive pulmonary disease, but how oral bacterial products affect lung inflammation remains unclear. This study shows that protease-rich products from the periodontal pathogen Porphyromonas gingivalis can be sensed by airway epithelial cells under COPD-like conditions. This response induces a chemokine signal that is linked to the accumulation of {gamma}{delta} T cells, a type of immune cell involved in inflammatory responses. Our findings suggest that the airway epithelium acts as an immune sensor, converting signals from aspirated oral bacterial protease into lung inflammation. This work provides a mechanistic framework for understanding how oral dysbiosis may contribute to immune remodeling in COPD.

immunology↗

bioRxiv2026

Hepatobiliary Progenitor-like Reprogramming in Liver Metastases

Metastatic progression requires cancer cells to adapt to the unique constraints of distant organ microenvironments, yet the mechanisms that drive organ-specific adaptations remain poorly understood. Here, we show that the liver actively rewrites metastatic cancer cell identity, driving tumor cells toward a hepatobiliary progenitor-like state. Through integrated transcriptomic, proteomic, metabolomic, and epigenomic analyses of patient-derived rapid-autopsy samples and experimental models, we identify this state as selectively enriched in liver metastases. It is characterized by co-activation of hepatic and biliary/progenitor regulators HNF4A and SOX9 and is observed across multiple epithelial cancers, indicating a conserved response to the hepatic niche. Mechanistically, hepatocyte-derived TGF-{beta} and hypoxia converge to activate a HIF-1-ACLY axis, increasing nuclear acetyl-coenzyme A availability and histone acetylation at hepatic lineage regulatory elements to drive hepatobiliary reprogramming. This coordinated niche-response program can be captured transcriptionally and is associated with inferior overall survival. Disruption of this pathway suppresses hepatic reprogramming and impairs liver metastatic fitness. These findings identify the liver as an active determinant of metastatic cell fate, linking microenvironmental signaling to metabolic and chromatin remodeling programs that enable lineage plasticity. More broadly, they reveal organ-specific reprogramming as a fundamental principle of metastasis and a therapeutic vulnerability in liver metastases.

cancer biology↗

bioRxiv2026

Early apelin receptor activation attenuates elastase-induced emphysema and preserves endothelial apelin receptor signaling in mice

Alveolar capillary endothelial cells are positioned adjacent to the alveolar epithelium and contribute to lung homeostasis and injury responses. Single-cell studies have identified aerocyte capillary endothelial cells (aCap), which are specialized for gas exchange, and general capillary endothelial cells (gCap), which contribute to endothelial maintenance and inflammatory signaling. Apelin and its receptor are differentially enriched across these endothelial compartments, but their roles in emphysema development remain incompletely understood. Using an elastase-induced emphysema model in male C57BL/6J mice, we combined bulk RNA sequencing, CIBERSORTx-based cell-type deconvolution, histology, inflammatory assays, pulmonary function testing, and pharmacologic activation of the apelin receptor with [Pyr1]-Apelin-13. At 24 hours after elastase exposure, the inferred fraction of gCap was reduced, and lung expression of apelin and the apelin receptor was decreased. Early [Pyr1]-Apelin-13 administration reduced lung inflammatory mediator expression, Ly6G-positive neutrophil accumulation, bronchoalveolar lavage neutrophil counts, and matrix metalloproteinase-9 activity. Early treatment also attenuated subsequent airspace enlargement, whereas treatment initiated after emphysema was established did not improve physiological or histological outcomes. In a chronic {beta}ENaC-transgenic mouse model, the inferred gCap fraction was maintained, the aCap fraction was reduced, and apelin receptor activation did not improve disease phenotypes. These findings suggest that early activation of the apelin receptor modifies acute inflammatory and endothelium-associated responses following elastase injury and limits emphysematous remodeling in mice. Together, these results support a time-sensitive role for apelin-APJ signaling during the early phase of emphysema development.

molecular biology↗

bioRxiv2026

Amorphous-to-Rodlet Structural Transition Governs the Interfacial Functions of Aspergillus oryzae Hydrophobin RolA

Hydrophobins are low-molecular-weight biosurfactant proteins that coat the cell surface of filamentous fungi, making it hydrophobic and supporting morphogenesis. On conidia, hydrophobins self-assemble to form rod-shaped multimeric structures known as rodlets. Previously, we reported that hydrophobin RolA from the industrial fungus Aspergillus oryzae first forms an amorphous film at the air-water interface and then undergoes structural rearrangement to form a densely packed rodlet film. This raised the question of whether the amorphous or the rodlet film is more important for the biological functions of RolA. In this study, to compare the properties of amorphous films with those of rodlet films, we used RolA mutants that had lost the ability to form rodlets and therefore remained in the amorphous state. We found that the rodlet film was more rigid than the amorphous film and had stronger surface activity and a greater capacity to change surface wettability. RolA altered the properties of A. oryzae conidia only when it was in the rodlet state. These findings highlight the functional versatility of RolA and show that their dynamic structural transitions directly modulate their function.

microbiology↗

bioRxiv2026

Dietary lipids attenuate IGF-1-Akt and injure epithelial-endothelial injury program that accelerates obstructive lung disease

Background Altered lipid metabolism is increasingly implicated in chronic obstructive pulmonary disease (COPD), but it remains unclear how a pre-existing obstructive lung state modifies the response to systemic lipid excess. We investigated whether high-fat diet (HFD) amplifies COPD-relevant lung injury and examined epithelial and vascular programs associated with this response. Methods Male wild-type (WT) and beta-epithelial sodium channel-transgenic ({beta}ENaC-Tg) mice were fed control diet or HFD for 10-11 weeks. Lung structure and function, whole-lung transcriptomes, Akt-FOXO1 signaling, apoptosis-related responses, and pulmonary vascular profiles were assessed. Streptozotocin-induced insulin-deficient diabetes and pharmacological IGF-1 receptor inhibition were used as mechanistic comparators. Palmitate responses were examined in human bronchial epithelial cells, ENaC-hyperactive epithelial cells, and endothelial cells, including conditioned-medium transfer. HFD preconditioning was also evaluated in an elastase-induced emphysema model. Statistical analyses included unpaired two-tailed Student's t tests, one-way ANOVA with Tukey-Kramer or Dunnett multiple-comparison testing, Pearson correlation, and Benjamini-Hochberg correction for RNA-sequencing analyses. Results HFD produced similar increases in body weight, glycemia, and adiposity in WT and {beta}ENaC-Tg mice, while further increasing distal-airspace enlargement and reducing FEV0.1/FVC in {beta}ENaC-Tg mice. Lung transcriptomics revealed coordinated remodeling of lipid metabolic, PI3K-Akt, and vascular programs. HFD reduced Akt phosphorylation, increased FOXO1 and Fasl, and increased TUNEL-positive cells in epithelial regions. Palmitate attenuated IGF-1-induced Akt activation in bronchial epithelial cells, whereas IGF-1 receptor inhibition reproduced Akt suppression and apoptosis-related responses without fully reproducing the HFD phenotype. HFD preconditioning also increased elastase-induced airspace enlargement, accompanied by parallel upregulation of FOXO1 and TUNEL positivity. HFD reduced pulmonary CD34-positive vascular profiles, and palmitate activated endothelial cells directly and through conditioned media from ENaC-hyperactive epithelium. In men with airflow obstruction, hepatic steatosis coincided with lower percent-predicted FEV1. Conclusions Dietary lipid stress amplifies obstructive lung injury and engages complementary epithelial and vascular responses. Impaired epithelial IGF-1-Akt signaling and epithelial-endothelial crosstalk provide a mechanistic framework linking systemic metabolic stress to reduced resilience of the obstructive lung.

molecular biology↗

bioRxiv2025

Structural and Thermodynamic Determinants of Anti-PGE2 mAb Specificity

We investigated the molecular determinants underlying the highly specific recognition of prostaglandin (PG) E2 and its structural analogues by an anti-PGE2 monoclonal antibody (mAb) and its Fab fragment using high-resolution X-ray crystallography coupled with detailed thermodynamic analyses, including conditions that mimic macromolecular crowding. Crystal structures of the Fab fragment in complex with PGE2, PGE1, and ONO5 were determined at 1.9 [A], 1.7 [A], and 1.7 [A] resolution, respectively, and the antigen-free Fab structure was solved at 2.0 [A]. The Fab accommodates the L-shaped PG scaffold within a deep antigen-binding crevasse formed between the {beta}-sheet frameworks of the VH and VL domains, where ligand recognition is mediated by multiple water-bridged hydrogen bonds and extensive hydrophobic contacts, including putative CH-O and CH-{pi} interactions. Comparison of antigen-free and ligand-bound structures revealed compensatory conformational rearrangements accompanied by reorganization of bound water networks. Upon PG binding, a short 310 helix forms at the tip of CDR-H1, stabilized by a cluster of hydrogen bonds and capping water molecules. This helix formation is associated with rotation of the VL domain and an increased Fab elbow angle. The CDR-H1 loop undergoes a flip-in transition in which Phe29H inserts into a hydrophobic cavity while Glu31H is extruded toward solvent, accompanied by {pi}-{pi} stacking between Tyr27H and Tyr32H. These changes collectively reduce hydrophobic surface area and promote enthalpy-driven ligand binding. The flexible -chain of PGE1, lacking the C5-C6 double bond, adopts altered conformations that disrupt C1-carboxyl interactions with three aromatic residues and lead to closure of a secondary water channel, consistent with subtle but meaningful differences in binding thermodynamics and crystallographic temperature factors relative to PGE2 and ONO5. Isothermal titration calorimetry (ITC) revealed high-affinity, enthalpy-driven PG binding to the Fab, in agreement with differential scanning calorimetry (DSC), which showed increased thermal stability upon complex formation. Under macromolecular crowding conditions induced by high bovine serum albumin (BSA) concentrations, PG binding to the intact mAb--but not to the Fab--exhibited improved discrimination between PGE2 and PGE1, suggesting that reduced entropy-enthalpy compensation under crowding amplifies subtle structural mismatches in ligand binding.

molecular biology↗

bioRxiv2025

M-Sec promotes the production of infectious HIV-1 virus through the exocyst complex

We have demonstrated that the cellular protein M-Sec promotes the transmission of human immunodeficiency virus type 1 (HIV-1). However, the underlying mechanism is not fully understood. Here, we report that M-Sec promotes the production of infectious HIV-1 virus. The major viral structural protein Gag distributed as many puncta in infected cells, which is one of the indicators of viral particle formation. The knockdown of M-Sec hindered the Gag puncta formation and co-localization of Gag with the viral envelope protein Env in cells, and reduced the amount of Env and infectivity of the produced virus. Consistent with these results, the over-expression of M-Sec induced the accumulation of Gag puncta, Gag/Env co-localization, and Env incorporation into virus and viral infectivity. M-Sec is known to bind phosphatidylinositol 4,5-bisphosphate (PIP2) and a small GTPase Ral, both of which were required for the M-Sec-mediated HIV-1 regulation. The exocyst complex, which is the downstream effector of Ral, was also required for the M-Sec-mediated HIV-1 regulation. Because PIP2, Ral and the exocyst complex are important for the M-Sec-mediated formation of the long plasma membrane protrusions, the present study suggests that M-Sec promotes HIV-1 transmission by acting on both cell structures and viral production through these overlapping components. Author SummaryDespite an effective anti-retroviral therapy, human immunodeficiency virus type 1 (HIV-1) persists in a fraction of infected cells, which is an obstacle to cure. HIV-1 exploits the cell-to-cell infection for its transmission, which is more efficient than infection by cell-free virus. Thus, it is important to fully understand the process of cell-to-cell infection towards the HIV-1 cure. We previously identified M-Sec as the cellular protein that potentiates the cell-to-cell infection of HIV-1. However, the underlying mechanism is not fully explained. In this study, we discovered that M-Sec promotes the production of infectious HIV-1 particles. Mechanistically, M-Sec affects the intracellular dynamics of the major viral structural protein Gag, which leads to an efficient incorporation of the viral envelope protein Env into viral particles. This activity of M-Sec depends on PIP2 (the phosphoinositide), Ral (the small GTPase), and the exocyst complex (the downstream effector of Ral), all of which are involved in vesicular trafficking. Thus, the present study identifies M-Sec and related molecular components as potential targets of anti-HIV-1 strategies.

microbiology↗

bioRxiv2025

Astrocytic FABP5 drives non-cell-autonomous oligodendrocyte injury in multiple system atrophy by promoting TNF signaling and ferroptotic stress

Multiple system atrophy (MSA) is a fatal -synucleinopathy characterized by progressive parkinsonism, cerebellar and autonomic dysfunction. Currently, the mechanisms driving cerebellar white matter neuroinflammation and degeneration in MSA are poorly understood. Here, we identified fatty acid-binding protein 5 (FABP5) as a key factor regulating cerebellar inflammation in MSA pathogenesis in a detailed study of human, mouse and cultured astrocytes. Firstly, transcriptomic profiling of human MSA cerebellar white matter revealed activation of pro-inflammatory and ferroptotic pathways, with FABP5 identified as a key pathway component that is upregulated. We confirmed that FABP5 is upregulated in reactive astrocytes in the PLP--syn transgenic mouse model, also in LPS-treated primary astrocytes. Fabp5 silencing suppressed TNF signaling, mitigated ferroptosis, and restored mitochondrial function. These findings suggest astrocytic FABP5 as a central intracellular regulator linking glial inflammation, ferroptosis, and mitochondrial injury. Overall, this mechanism suggests that FABP5 drives pathology mediated by astrocytes oligodendroglia in MSA, therefore representing a novel and promising therapeutic target.

neuroscience↗

bioRxiv2025

High-speed atomic force microscopy reveals surface-catalyzed elongation mechanism of fungal functional amyloid, hydrophobin RolA

Hydrophobins, a type of functional amyloid, are conserved in filamentous fungi and act as a protective coat in the fibrous form called rodlet. Rodlets form hierarchical structures where they are bundled and densely aligned, contributing to the hydrophobicity of the mycelium surface. However, the formation mechanism of the hierarchical structures is completely unknown. In this study we used high-speed atomic force microscopy to directly observe the structural dynamics of hierarchical structure formation by hydrophobin RolA from the industrial fungus Aspergillus oryzae at a single-fibril level and revealed its mechanism. The elongation of rodlets occurred at both ends and was discontinuous, alternating between periods when they could elongate (growth state) and could not elongate (pause state). This suggests an equilibrium of two distinct structural states at the rodlet ends. We also discovered an aggregation pathway, termed "surface-catalyzed elongation", in which elongation is promoted by lateral interactions between bundled rodlets. Surface-catalyzed elongation decreased the energy barrier of both structural switching between growth and pause states and elongation at rodlet ends, doubling the elongation rate in bundled rodlets. The rodlet surface could be considered as a catalyst for the elongation of neighboring rodlets. Surface-catalyzed elongation could contribute to rodlet bundling, whereby rodlets tend to form oriented domain structures, and our Monte Carlo simulations confirmed this. Surface-catalyzed elongation may be a universal concept to explain the hierarchical assembly mechanism of amyloid fibrils, so it could contribute to the advancement of amyloid research in general.

biophysics↗

bioRxiv2025

Lamin A/C Deficiency Drives Genomic Instability and Poor Survival in Small-Cell Lung Cancer through Increased R-loop Accumulation

Lamin A/C (LMNA), a key component of the nuclear envelope, is essential for maintaining nuclear integrity and genome organization [1]. While LMNA dysregulation has been implicated in genomic instability across cancer and aging, the underlying mechanisms remain poorly understood [2]. Here, we investigate LMNAs role in small-cell lung cancer (SCLC), a highly aggressive malignancy characterized by extreme genomic instability [3, 4]. We demonstrate that LMNA depletion promotes R-loop accumulation, transcription-replication conflicts, replication stress, DNA breaks, and micronuclei formation. Mechanistically, LMNA loss disrupts nuclear pore complex distribution, reducing phenylalanine-glycine (FG)-nucleoporin incorporation and impairing RNA export efficiency. Furthermore, we show that LMNA expression is epigenetically repressed by EZH2 during SCLC differentiation from neuroendocrine (NE) to non-NE states. Clinically, low LMNA levels correlate with significantly worse survival in SCLC patients. These findings uncover a novel role for LMNA in safeguarding genome integrity and shaping tumor heterogeneity, with broad implications for cancer and aging. Significance StatementLamin A/C, a key structural component of the nuclear envelope, is frequently lost or mutated in cancer, laminopathies, and aging-related disorders. Lamin A/C loss is associated with genomic instability, but the underlying mechanisms remain incompletely understood. We demonstrate that LMNA loss drives genomic instability by promoting R-loop accumulation through disrupted nuclear pore dynamics and impaired RNA export. These findings reveal a previously unrecognized link between LMNA loss, nuclear envelope dysfunction, and genome instability. Targeting this pathway could help mitigate genomic instability in aging and laminopathies, while leveraging R-loop accumulation may enhance the efficacy of DNA-damaging therapies in cancer.

cancer biology↗

bioRxiv2025

Distinct roles of cortical layer 5 subtypes in associative learning

Adaptive behavior is critically dependent on associative learning, where environmental cues are linked with subsequent positive or negative outcomes. In mammals, primary neocortical sensory areas serve as pivotal nodes in this process, processing stimuli and distributing information to cortical and subcortical networks. Layer 5 (L5) of the cortex comprises two types of pyramidal projection neurons--intratelencephalic (IT) and extratelencephalic (ET) neurons--each with distinct downstream targets. Despite the crucial function of L5 as a main output node of the cortex, the specific contributions of these L5 neuronal subtypes to associative learning remain poorly understood. In the present study, by leveraging transgenic mouse lines, we distinguished IT and ET neurons in the primary somatosensory cortex and examined their roles in a whisker-based frequency-discrimination learning task. Longitudinal two-photon calcium imaging revealed distinct response characteristics between IT and ET neurons throughout learning. Interestingly, the activity of IT neurons hardly changed over the five days of learning, while the activity of ET neurons developed robustly. Furthermore, IT neurons appeared to show stimuli encoding from the beginning, whereas the ET neurons became increasingly responsive to stimuli associated with reward. Chemogenetic silencing of either IT or ET neurons both impaired learning, but in strikingly distinct ways, each associated with a different phase of learning. By modeling the response characteristics of IT and ET neurons using a reinforcement learning framework, we show that IT neurons primarily encode sensory stimuli, and their representations are critical for forming stimulus-reward associations. ET neurons instead represent the value of the stimulus, used for refining behavior. Thus, our results delineate the distinct roles of L5 IT and ET neurons, underscoring their integral and complementary contributions to associative learning.

neuroscience↗

bioRxiv2024

The crucial role of intercellular calcium wave propagation triggered by influenza A virus in promoting infection

Influenza A viruses (IAVs) initially infect a few host cells, and the infection subsequently spreads to neighboring cells. However, the molecular mechanisms underlying this expansion remain unclear. Here, we show that IAV infection upregulates the frequency of intercellular calcium wave propagations (iCWPs) that mediate the spread of IAVs. ADP released from initially infected cells mediated iCWPs via the P2Y1 receptor. The generation of iCWPs and spread of viral infection were inhibited by a P2Y1 antagonist. Enhanced endocytosis in the surrounding cells that received ADP signaling upregulated viral entry. Expression of IAV matrix protein 2 (M2) in initially infected cells triggered iCWPs through ADP diffusion, thereby increasing infection, whereas an ion permeability-deficient mutation of M2 or inhibition of its ion channel activity suppressed iCWPs. Therefore, intercellular calcium signaling is essential for early expansion and potential establishment of IAV infection, which offers a promising target for IAV prophylaxis.

cell biology↗

bioRxiv2024

Metastatic organotropism in small cell lung cancer

Metastasis is the leading cause of cancer-related deaths, yet its regulatory mechanisms are not fully understood. Small-cell lung cancer (SCLC) is the most metastatic form of lung cancer, with most patients presenting with widespread disease, making it an ideal model for studying metastasis. However, the lack of suitable preclinical models has limited such studies. We utilized rapid autopsy-derived tumors to develop xenograft models that mimic key features of SCLC, including histopathology, rapid and widespread development of metastasis to the liver, brain, adrenal, bone marrow, and kidneys within weeks, and response to chemotherapy. By integrating in vivo lineage selection with comprehensive bulk and single cell multiomic profiling of transcriptomes and chromatin accessibility, we identified critical cellular programs driving metastatic organotropism to the liver and brain, the most common sites of SCLC metastasis. Our findings reveal the key role of nuclear-cytoskeletal interactions in SCLC liver metastasis. Specifically, the loss of the nuclear envelope protein lamin A/C, encoded by the LMNA gene, increased nuclear deformability and significantly increased the incidence of liver metastasis. Human liver metastases exhibited reduced LMNA expression compared to other metastatic sites, correlating with poorer patient outcomes and increased mortality. This study introduces novel preclinical models for SCLC metastasis and highlights pathways critical for organ-specific metastasis, offering new avenues for the development of targeted therapies to prevent or treat metastatic disease.

cancer biology↗

bioRxiv2024

Identification of M-Sec as a unique cellular regulator of CSF-1 receptor activation

Fms, the CSF-1 receptor encoding tyrosine kinase, is essential for tissue macrophage development, and the therapeutic target for many tumors. However, it is not completely understood how Fms activation is regulated. Here, we identify the cellular protein M-Sec as a unique regulator of Fms. In macrophages, Fms forms large aggregates via unknown mechanisms. We found that the inhibition or knockdown of reduced Fms aggregate formation and functional response of macrophages to CSF-1, which was consistent with reduced Fms activation after CSF-1 stimulation. When expressed in 293 cells, M-Sec augmented Fms aggregate formation and CSF-1-induced Fms activation. CSF-1 and M-Sec bind the cellular phosphatidylinositol 4,5-biphosphate (PIP2). The removal of PIP2-binding motif of Fms or M-Sec, or the depletion of cellular PIP2 reduced Fms aggregate formation. Moreover, M-Sec altered cellular distribution of PIP2. Since CSF-1-induced dimerization of Fms is critical for its activation, our findings suggest that M-Sec augments large Fms aggregate formation via PIP2, which brings Fms monomers close to each other and enables the efficient dimerization and activation of Fms in response to CSF-1.

molecular biology↗

bioRxiv2024

2-monopalmitin, but not 1-monopalmitin, enhances hypothalamic leptin responsiveness, energy balance, and glucose homeostasis under overnutrition

Nutrient excess, a major driver of obesity, diminishes hypothalamic responses to exogenously administered leptin, a critical hormone for energy balance. Here, we found that 2-monopalmitin, but not 1-monopalmitin or palmitic acid, enhances hypothalamic leptin responsiveness in ex vivo brain slices. Centrally administered 2-monopalmitin markedly restored the leptin-induced suppression of food intake and reduction of body weight in diet-induced obese mice. Peripherally administered 2-monopalmitin also enhanced the anorectic effect of centrally administered leptin. Furthermore, daily 2-monopalmitin treatment protected against diet-induced body weight gain, and the energy expenditure of 2-monopalmitin-treated mice was significantly enhanced in a leptin-dependent manner. We also demonstrated that 2-monopalmitin lowered blood glucose levels, improved glucose and insulin tolerance, and protected mice against HFD-induced peripheral insulin resistance at the cellular and whole-body levels. Finally, treatment with 2-monopalmitin protected against LPS-induced leptin resistance, and decreased the hypothalamic levels of SOCS3, an inhibitor of leptin actions, and inflammatory cytokines. Altogether, our results showed that 2-monopalmitin in the brain, but not 1-monopalmitin or palmitic acid, is critical for linking overnutrition to the control of neural leptin actions.

physiology↗

bioRxiv2024

Genomic alterations and transcriptional phenotypes in circulating tumor DNA and matched metastatic tumor

BackgroundProfiling circulating cell-free DNA (cfDNA) has become a fundamental practice in cancer medicine, but the effectiveness of cfDNA at elucidating tumor-derived molecular features has not been systematically compared to standard single-lesion tumor biopsies in prospective cohorts of patients. The use of plasma instead of tissue to guide therapy is particularly attractive for patients with small cell lung cancer (SCLC), a cancer whose aggressive clinical course making it exceedingly challenging to obtain tumor biopsies. MethodsHere, a prospective cohort of 49 plasma samples obtained before, during, and after treatment from 20 patients with recurrent SCLC, we study cfDNA low pass whole genome (0.1X coverage) and exome (130X) sequencing in comparison with time-point matched tumor, characterized using exome and transcriptome sequencing. ResultsDirect comparison of cfDNA versus tumor biopsy reveals that cfDNA not only mirrors the mutation and copy number landscape of the corresponding tumor but also identifies clinically relevant resistance mechanisms and cancer driver alterations not found in matched tumor biopsies. Longitudinal cfDNA analysis reliably tracks tumor response, progression, and clonal evolution. Genomic sequencing coverage of plasma DNA fragments around transcription start sites shows distinct treatment-related changes and captures the expression of key transcription factors such as NEUROD1 and REST in the corresponding SCLC tumors, allowing prediction of SCLC neuroendocrine phenotypes and treatment responses. Conclusions These findings have important implications for non-invasive stratification and subtype-specific therapies for patients with SCLC, now treated as a single disease.

cancer biology↗