Biology subjects

Chakrabarti, P.

Publications and source records attributed to Chakrabarti, P..

9 recordsLinked to original sources

bioRxiv2026

USP18-STAT2 axis enhances hepatic resilience under proteotoxic stress

The liver is a metabolic hub with a high protein turnover that renders it uniquely susceptible to proteotoxic stress. Perturbation of proteostasis, either by proteasomal inhibitors or in chronic liver diseases, could adversely impact liver physiology. Here, we show that proteasomal inhibition unexpectedly suppresses basal type I interferon (IFN-I) signaling in the murine liver. Proteasomal inhibition by bortezomib selectively downregulates a subset of interferon-stimulated genes (ISGs), among which USP18 and ISG15 emerge as critical determinants of hepatocellular survival. We identify USP18 as a central cytoprotective factor that prevents proteotoxic apoptosis independently of its deubiquitinase activity, but strictly requires its scaffolding function mediated by isoleucine-60 and interaction with STAT2. Mechanistically, proteotoxic stress disrupts IRF9 nuclear translocation, attenuating USP18 transcription, and drives USP18 and other ISGs into insoluble aggregates with kinetics distinct from canonical IFN-I-induced insolubility. Strikingly, IFN-I priming preserves ISG solubility, restores USP18 abundance, and confers resistance to proteotoxic cell death. Together, these findings uncover an unanticipated link between proteostasis and innate immune signaling, and establish the USP18-STAT2 axis to enhance hepatic resilience under proteotoxic stress.

cell biology↗

bioRxiv2026

Glucose-dependent regulation of hepatic adipsin controls glucose uptake and tolerance

Complement factor D, also known as adipsin, is produced by adipose tissue, and the liver that links metabolic regulation with innate immunity. Despite its established systemic functions, the regulation of hepatic adipsin expression and its contribution to metabolic disease remain poorly defined. Here, we show that hepatic adipsin protein abundance is markedly increased in individuals with type 2 diabetes (T2D), and positively correlates with glycated hemoglobin, despite unchanged mRNA expression. Concordantly, hepatic adipsin protein levels were elevated in multiple murine models of hyperglycemia, including type 1 diabetes (T1D), T2D, and following fasting-refeeding transitions. In cultured hepatocytes, glucose exposure induced a rapid, dose-dependent increase in adipsin protein without altering transcript abundance, demonstrating post-transcriptional regulation. Mechanistically, glucose stimulates adipsin translation via dephosphorylation of eukaryotic initiation factor 2 (eIF2), and activation of the mammalian target of rapamycin, mediated by the 5' untranslated region of adipsin mRNA. Functionally, hepatocyte-specific depletion of adipsin impaired postprandial glucose tolerance, with reduced glucose uptake and a marked downregulation of glucose transporter type 2 (GLUT2). Taken together, these findings identify hepatic adipsin as a glucose-responsive translational target that couples nutrient availability to metabolic adaptation, revealing a new layer of regulation with potential relevance to diabetes pathogenesis. HighlightsO_LIHepatic adipsin protein increases in type 2 diabetes and correlates with glycemic status independent of mRNA expression. C_LIO_LIGlucose induces adipsin translation through eIF2 dephosphorylation and mTOR activation. C_LIO_LImTOR controls adipsin synthesis via structured 5'UTR of adipsin mRNA. C_LIO_LILiver-specific adipsin depletion impairs post-prandial glucose tolerance by downregulating GLUT2. C_LIO_LIHepatic adipsin acts as a glucose-responsive effector of glycemic control. C_LI

cell biology↗

bioRxiv2025

Insights from U.S. beekeeper triage surveys following unusually high honey bee colony losses 2024-2025

In January of 2025, U.S. commercial beekeepers reported unusually high honey bee colony losses as they prepared colonies for almond pollination. Two industry groups launched nationwide surveys to document colony losses between June 2024 and March 2025 across all scales of beekeeping. This study analyzes these survey data to assess colony losses, estimate financial impacts, and identify correlations with beekeeper management practices and geographical locations. Unlike past surveys, commercial beekeepers experienced more severe losses than smaller-scale beekeepers during this period. Respondents, managing over half of U.S. colonies, most frequently cited Varroa mites as the cause for their losses. Varroa mites were followed by pesticides and pathogens in the case of commercial beekeepers and by queen failure and weather in the case of smaller-scale beekeepers. Although Varroa was the most frequently cited cause, losses did not significantly differ between users and non-users of amitraz, suggesting that rising amitraz resistance alone does not explain observed trends. Differences in protein and carbohydrate feeding frequencies also played a role in net losses. While colony loss rates and financial concern varied widely among respondents, commercial beekeepers understandably showed higher sensitivity to financial impacts, with concerns increasing linearly with loss severity. This study highlights the value of beekeeper surveys which, alongside direct analyses of bee samples and longitudinal studies, help identify effective management strategies and environmental risks. Such insights are crucial for addressing the leading causes of colony losses on a national scale, and ultimately aid in safeguarding honey bee health, pollination services, and agricultural production. HighlightsO_LIUnprecedented honey bee colony losses C_LIO_LIIndications of disease stress C_LIO_LIHigh economic pain for commercial beekeepers and growers C_LI

ecology↗

bioRxiv2025

Sensitizing Immune-Refractory Ovarian Tumors via p53 Mutation-Tailored Immunotherapy

High-grade serous ovarian cancer demonstrates limited responsiveness to immune checkpoint inhibitors, owing in part to immunosuppressive environments shaped by nearly universal p53 aberrations. Utilizing an immunocompetent mouse model and individual p53 mutations, we identified a dependence of the p53-R270H mutation (equivalent of human R273H) on regulatory T cells (Tregs) and the PD-1/PD-L1 axis. Analysis of patient datasets associated R273H with elevated levels of two p53 targets, PD-L1 and amphiregulin (AREG), a Tregs growth factor. In contrast to p53-R172H tumors, where there was limited activity, dual antibody therapy targeting AREG and PD-L1 selectively and effectively inhibited R270H tumors. This involved polarization toward M1 macrophages, infiltration of CD8+ T cells, diminished Ly6G+ neutrophils and downregulation of interleukin-4. In patient-derived R273C organoids, the combination treatment reduced the CD4/CD8 ratio. This study is the first to establish a mutation-tailored therapeutic approach that leverages the capacity of p53 to modulate immunosuppressive mechanisms.

cancer biology↗

bioRxiv2021

Genomic surveillance and phylodynamic analyses reveal emergence of novel mutation and co-mutation patterns within SARS-CoV2 variants prevalent in India

Emergence of distinct viral clades has been observed in SARS-CoV2 variants across the world and India. Identification of the genomic diversity and the phylodynamic profiles of the prevalent strains of the country are critical to understand the evolution and spread of the variants. We performed whole-genome sequencing of 54 SARS-CoV2 strains collected from COVID-19 patients in Kolkata, West Bengal during August to October 2020. Phylogeographic and phylodynamic analyses were performed using these 54 and other sequences from India and abroad available in GISAID database. Spatio-temporal evolutionary dynamics of the pathogen across various regions and states of India over three different time periods in the year 2020 were analyzed. We estimated the clade dynamics of the Indian strains and compared the clade specific mutations and the co-mutation patterns across states and union territories of India over the time course. We observed that GR, GH and G (GISAID) or 20B and 20A (Nextstrain) clades were the prevalent clades in India during middle and later half of the year 2020. However, frequent mutations and co-mutations observed within the major clades across time periods do not show much overlap, indicating emergence of newer mutations in the viral population prevailing in the country. Further, we explored the possible association of specific mutations and co-mutations with the infection outcomes manifested within the Indian patients.

genomics↗

bioRxiv2021

Inhibition of Extracellular Vesicle-Associated MMP2 Abrogates Intercellular Transfer of Hepatic miR-122 to Tissue Macrophages and Curtails Liver Inflammation

microRNA-122 (miR-122), a liver specific regulatory RNA, plays an important role in controlling metabolic homeostasis in mammalian liver cells. Interestingly, miR-122 is also a proinflammatory microRNA and when exported to tissue resident macrophage induces expression of inflammatory cytokines there. We found intercellular transfer of miR-122 in lipid exposed liver plays a role in liver inflammation. Exploring the mechanism of intercellular miR-122 transfer from hepatic cells, we detected MMP2 on the membrane of extracellular vesicles derived from hepatic cells which proved to be essential for transfer of extracellular vesicles and their miRNA content from hepatic to non-hepatic cells. Matrix metalloprotease 2 or MMP2 is a metalloproteinase that plays a key role in shaping and remodelling the extracellular matrix of human tissue by targeting degradation of matrix proteins. MMP2 was found to increase the movement of the EVs along the extracellular matrix to enhance their uptake in recipient cells. Inhibition of MMP2 restricts functional transfer of hepatic miRNAs across the hepatic and non-hepatic cell boundaries. By targeting MMP2, we could reduce the innate immune response in mammalian liver by preventing intra-tissue miR-122 transfer. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=176 SRC="FIGDIR/small/425217v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@aec3b0org.highwire.dtl.DTLVardef@1b18e87org.highwire.dtl.DTLVardef@47e75org.highwire.dtl.DTLVardef@10a48e0_HPS_FORMAT_FIGEXP M_FIG C_FIG O_LIHuman hepatocytes on exposure to high lipid export out miRNAs including proinflammatory miR-122. C_LIO_LIExtracellular miR-122 is taken up by tissue macrophages to get them activated to produce inflammatory cytokines. C_LIO_LIMMP2 present on the surface of the EVs released by hepatocyte is essential for miRNA transfer to macrophage cells C_LIO_LIInhibition of MMP2 prevents miR-122 transfer to macrophage and stops activation of recipient macrophage. C_LI

cancer biology↗

bioRxiv2020

Lipid Droplets Promote Phase Separation of Ago2 to Accelerate Dicer1 Loss and Decelerate miRNA Activity in Lipid Exposed Hepatic Cells

miR-122 is a liver specific miRNA that plays an important role in controlling metabolic homeostasis in mammalian liver cells. Interestingly, miR-122 on exposure to lipotoxic stress is reduced in liver cells. To fight stress, miRNA processor Dicer1 is depleted to cause reduced miR-122 production and the lowering of miRNA level ensures a better stress response in hepatocytes under lipotoxic stress. Interestingly, lipid droplets, formed in the liver cells on exposure to high fat, ensure cytoplasmic phase separation of Ago2 and prevent interaction of Ago2 with Dicer1. Lipid droplets bind miRNA and enhance miRNA-Ago2 uncoupling and Ago2 phase separation. Loss of interaction between Ago2 and Dicer1 eventually facilitates export and lowering of cellular Dicer1, a process also dependent on the endosomal maturation controller protein Alix, thereby ceasing pre-miRNA processing by Dicer1 in lipid exposed cells. Depletion of lipid droplets by downregulation of Perilipins with siRNAs resulted in a rescue of cellular Dicer1 level and Ago2-Dicer1 interaction. This is a novel mechanism that liver cells adopt to restrict cellular miRNA levels under stress condition. Thus, lipid droplets prevent cell death upon exposure to high fat by reducing intra and extracellular pool of miR-122 in hepatic tissue.

cell biology↗

bioRxiv2020

Transcriptional regulator PAX4 links Receptor Tyrosine Kinases and cytoskeleton stability in Alzheimer's disease and type 2 diabetes

Alzheimers Disease (AD) and Type 2 Diabetes (T2D) share a common hallmark of insulin resistance. Besides Insulin Receptor (IR), two non-canonical RTKs, ALK and RYK, exhibit significant and consistent functional downregulation in post-mortem AD and T2D tissues. Incidentally, both have Grb2 as a common downstream adapter and NOX4 as a common ROS producing factor. Here we show that Grb2 and NOX4 play critical roles in reducing the severity of both the diseases. The study demonstrates that the abundance of Grb2 in degenerative conditions, in conjunction with NOX4, reverse cytoskeletal degradation by counterbalancing the network of small GTPases. PAX4, a transcription factor for both Grb2 and NOX4, emerges as the key link between the common pathways of AD and T2D. Both ALK and RYK downregulation elevate the PAX4 level by reducing its suppressor ARX via Wnt/{beta}-Catenin signaling pathway. For the first time, this study brings together RTKs other than Insulin Receptor (IR), their common transcription factor PAX4 and both AD and T2D pathologies on a common regulatory platform.

neuroscience↗

bioRxiv2019

Resveratrol prevents amyloid fibrillation of insulin by arresting it in a bioactive oligomeric form

Insulin fibrillation is a limiting factor for its long-term storage because of considerably reduced bioavailable moieties. Deposition of fibrillated insulin can also cause subcutaneous insulin amyloidoma. Toxic phenolic compounds along with Zinc are used during commercial preparation of insulin to stabilize it in a hexameric form. Designed or repurposed natural small molecules with anti-amyloidogenic properties could thus be attractive agents for preventing insulin fibrillation. Natural polyphenolic compounds which have been shown to serve as anti-amyloid agents for proteins associated with neurodegenerative diseases are potential candidates for such function.\n\nIn this study we have demonstrated that resveratrol, a natural polyphenol, can not only prevent insulin fibrillation but can also preserve insulin in a bioactive oligomeric form even at high temperature. While investigating the influence of some natural polyphenols on human insulin (hINS) in a condition inductive to amyloid fibrillation at physiological pH, we found attenuation, to different extents, of insulin fibril formation. However, visualization of polyphenol-treated hINS revealed that resveratrol in particular has the unique ability to arrest hINS before the onset of fibrillation growth in soluble oligomeric forms with discrete spherical morphology. Importantly, insulin treated with resveratrol retains its full biological activity in vivo and exerts no toxicity towards cell lines. Structural characterization of the major population of resveratrol-induced insulin oligomers by cryo-EM and single particle 3D reconstruction revealed its morphology that resembled crystal structure of insulin hexamer formulated with phenolic compounds. Thus, our study suggests that resveratrol can be an effective nontoxic substituent of phenolic compounds for insulin preservation.

biochemistry↗