Search bioRxiv⌕ Search

Biology subjects

Sahu, R.

Publications and source records attributed to Sahu, R..

14 recordsLinked to original sources

Androgen Receptor mediates beige adipocyte homeostasis and plasticity

Male adipose tissue undergoes profound post-pubertal remodeling characterized by the progressive transition of beige adipocytes toward a white adipocyte phenotype. Although androgen signaling has been implicated in adipose tissue biology, its role in beige adipocyte remodeling and metabolic plasticity remains poorly understood. Here we show that androgen receptor (AR) signaling is dynamically activated in inguinal white adipose tissue during the post-pubertal beige-to-white transition in male mice. Inducible deletion of AR in beige adipocytes impaired this remodeling process, resulting in the persistence of multilocular beige-like adipocytes despite reduced thermogenic competence and marked mitochondrial abnormalities. Transcriptomic and cistromic analyses identified AR as a direct regulator of adipocyte metabolic and differentiation programs, whereas immune-related transcriptional signatures in AR-deficient adipose tissue primarily reflected macrophage infiltration and inflammatory remodeling. Loss of AR promoted mitochondrial dysfunction, mitophagy, and altered glucose handling, while cell-autonomous AR silencing in beige adipocytes recapitulated key defects in mitochondrial organization and adipocyte identity. Longitudinal and metabolic challenge studies further demonstrated that AR signaling is required for age-associated adipose remodeling and adaptive beige adipocyte plasticity during high-fat diet feeding and cold exposure. Together, these findings identify AR as a central regulator of beige adipocyte remodeling, mitochondrial homeostasis, and adaptive metabolic function in male adipose tissue.

physiology↗

IRES-mediated translation of delta160p53 regulates p53 functions and fine-tunes cancer homeostasis

Mutations in p53 and its 12 isoforms can alter its functions. As N-terminally truncated isoforms of p53 (delta40p53, delta133p53, and delta160p53) participate in tetramer formation, they are important regulators of cancer fate. Although delta40p53- and delta133p53-mediated regulation of cancer is well reported, the mechanism underlying delta160p53 production and its functional role remains unclear. We investigated the internal ribosomal entry site (IRES)-mediated translation of {Delta}160p53 and its role in cancer regulation. As differential synthesis of delta160p53 was observed under different stress conditions, IRES-mediated translation of this isoform was demonstrated using bicistronic luciferase constructs. No cryptic promoters or splicing sites were detected in the IRES sequence. Cell death and late apoptosis were significantly decreased, while proliferation, the number of cells in the S phase, and drug resistance were induced by delta160p53. Furthermore, delta160p53 did not induce p53-responsive promoters. RNA sequencing analysis of delta160p53 overexpression showed similar results, along with the inhibition of other tumor suppressor genes. Overall, our results provide insights into IRES-mediated translation of delta160p53, which can be considered a novel target for cancer treatment.

molecular biology↗

Viral Protease Nsp5 Hijacks La Autoantigen to Orchestrate the Translation to Replication Transition in SARS-CoV-2

Viruses genetically encode proteins to regulate their life cycle. To translate this genetic information, most viruses exploit host translation machinery. Host dependency leads to competition between viral RNA and host mRNAs. Most viruses overcome it by inhibiting cap-dependent translation of host mRNAs and shifting its own translation into cap-independent mode. This switch is largely orchestrated by host RNA binding proteins (RBPs) by binding to viral 5UTRs. Here we demonstrate that human La autoantigen (La protein) specifically binds to GCAC sequence near the initiator AUG within the 5UTR of SARS-CoV-2 RNA promoting viral non-structural protein synthesis by cap independent translation, while suppressing replication early in infection. Interestingly, around 18-24 h post-infection, the viral protease Nsp5 cleaves La at a conserved LQ site, abrogating its 5'UTR interaction, which correlates with reduced polysome association and increased viral RNA availability for replication. MD simulation and docking study suggests that the cleavage disrupts La dimerization and truncates its C-terminal intrinsically disordered region, reducing RNA-binding affinity and conformational stability required for translation-competent ribonucleoprotein complexes. Results put forward a unique mechanism by which Nsp5-mediated proteolysis of La drives the temporal switch from translation to replication of SARS-CoV-2.

microbiology↗

Interdependent androgen and glucocorticoid receptor signalling shapes prostate epithelial homeostasis

Androgen signalling is essential for prostate secretory functions and epithelial cell maintenance, yet how this signal is translated into a transcriptional output remains poorly understood. Androgens functions are primarily mediated by the androgen receptor (AR), which binds hormone response elements similar to those of other steroid receptors, including the glucocorticoid receptor (GR). Here we show that AR and GR are co-expressed in the prostate epithelium, and co-located within nuclear foci. Moreover, GR promotes the formation and dynamics of AR nuclear condensates, and heterodimerizes with AR in a ligand-binding domain-dependent manner. In addition, subtle variations within the hormone response element sequence direct the co-recruitment of AR and GR into activator or repressor complexes to activate or repress gene expression. Finally, prostate-specific deletion of GR in mice disrupts AR nuclear distribution, impairs AR-dependent gene networks involved in epithelial maintenance, and promotes the expression of genes involved in metabolism and cell cycle, resulting in altered tissue homeostasis. Thus, these findings identify GR as an integral component of the AR transcriptional machinery in epithelial cells of the healthy prostate, and reveal how shared cis-regulatory elements are interpreted to generate distinct transcriptional outcomes.

cell biology↗

Bone Morphogenetic Protein Pathway Modulates Parkinson's Disease Genetic Risk and Promotes Motor Recovery

Progress toward disease-modifying Parkinsons disease (PD) therapies is hindered by limited understanding of pathogenic drivers and lack of therapies that restore the damaged dopaminergic (DA) neurons driving motor deficits. We investigated the role of the bone morphogenetic protein (BMP) pathway in PD using common and rare genetic variants across large-scale datasets. Single-variant analyses identified nominal associations with PD risk and onset age. A BMP polygenic risk score (PRS) was significantly associated with PD risk (OR = 1.21, empirical P = 1.0 x 10-), a result replicated in proxy-case analyses (OR = 1.14, empirical P = 1.0 x 10-) and remained significant after sensitivity testing. To test the results functional relevance, we genetically and pharmacologically inhibited BMP signaling in mice, which induced motor deficits and PD-like neuropathology. In a -synuclein preformed fibril (PFF) mouse model, BMP5 and BMP7 (BMP5/7) demonstrated neuroprotective effects when administered concurrently with -synuclein PFFs. Importantly, when delivered after PFFs-induced motor symptoms onset, BMP5/7 demonstrated neurorestorative effects, ameliorating both motor impairments and neuropathology. These findings provide first evidence that BMP signaling variations contribute to polygenic PD risk, identify a physiological role for this pathway in safeguarding against PD-related pathology, and demonstrate BMPs therapeutic potential for disease modification.

neuroscience↗

The Kifc3 Motor Protein Controls Centrosomal Factor Cep192 in Ontogenic Coordination of Megakaryocyte Development

The distinct features of neonatal megakaryocytes, high proliferation and inefficient platelet production, have clinical repercussions. A diminished capacity for stress thrombopoiesis, the response to acute drops in platelet counts, contributes to the high prevalence of thrombocytopenia in premature infants and to impaired platelet recovery after umbilical cord blood stem cell transplantation. High proliferation also promotes leukemogenesis in babies with Down Syndrome (DS). The transcriptional coactivator Mkl1/MrtfA participates in programming the ontogenic shift from fetal/neonatal to adult-type megakaryopoiesis; in this activity it is opposed by the DS-associated kinase Dyrk1a. In a screen for downstream ontogenic effectors in human progenitors, we identified the kinesin Kifc3 as a factor selectively decreased in adult megakaryocytes and whose knockdown in neonatal megakaryocytes induced adult-type morphogenesis with augmented platelet release. Kifc3 acts as a minus-end directed motor for centrosomal delivery of various cargos. Centrosomal release of Cep192 has recently been found induce cellular process extensions through actin remodeling, reminiscent of megakaryocyte platelet release. In our studies, Cep192 showed striking upregulation and dispersion in adult vs neonatal megakaryocytes, and Kifc3 knockdown recapitulated this effect in neonatal megakaryocytes. A role for Cep192 in promoting megakaryocyte morphogenesis, distinct from its role in centrosome biogenesis, was demonstrated in vitro and in vivo. In silico screening for Kifc3 inhibitors identified a small molecule that affected neonatal megakaryocytes similarly to Kifc3 knockdown, indicating feasibility for therapeutic argeting of the Kifc3-Cep192 pathway in clinical conditions associated with fetal-type megakaryopoiesis. Key PointsO_LIThe motor protein Kifc3 dictates megakaryocyte ontogeny in association with its control of the centrosomal actin-remodeling factor Cep192. C_LIO_LIKnockdown or small molecule targeting of Kifc3 enhances neonatal megakaryocyte morphogenesis and thrombopoiesis. C_LI

developmental biology↗

Interaction and co-phase separation of SARS-CoV-2 nucleocapsid protein and human hnRNPA1 and its implications for viral life cycle

The nucleocapsid (N) protein of SARS-CoV-2 is central to viral assembly and replication. It binds viral RNA to form a helical nucleocapsid and enabling genome packaging and release into host cells. Human hnRNPA1, one of the most abundant RNA-binding proteins in eukaryotes, regulates key aspects of RNA metabolism, including splicing, transcription, localisation, and transport. Here, we report a direct physical interaction between SARS-CoV-2 N protein and hnRNPA1 with moderate affinity (Kd [~] 0.18 M), primarily mediated through their intrinsically disordered regions. Furthermore, we found that these proteins co-phase separate in vitro and co-localise within stress granules in cells. In vivo studies reveal that hnRNPA1 suppresses viral replication, suggesting that the N protein - hnRNPA1 interaction plays an important role in modulating the viral life cycle.

biochemistry↗

Androgen receptor imprints satellite cells stemness and preserves their reservoir for lifelong regeneration and optimal repair

Skeletal muscle stem cells (MuSC) are the guardians of muscle regeneration, sustaining tissue integrity through a delicate balance of quiescence, activation, and lineage commitment. While numerous molecular cues have been implicated in regulating these processes, the influence of androgen receptor (AR) signaling, an essential hormonal pathway for male muscle physiology, has remained largely unexplored. Here, we show that AR expression defines quiescent MuSC and acts as a safeguard of their dormancy. Integrated multi-omic analyses reveal a redistribution of AR binding from quiescence-maintenance loci to regulatory elements driving activation and metabolic reprogramming during repair. Loss of AR in young adult mice disrupts this balance, precipitating premature cell-cycle entry, skewed division modalities, depletion of the stem cell reservoir, and destabilization of the niche. These defects converge with hallmarks of aging-associated androgen decline, while androgen supplementation restores regenerative competence. Together, our findings establish AR signaling as a pivotal determinant of MuSC fate and a cornerstone of skeletal muscle homeostasis.

developmental biology↗

Glucocorticoid Receptor Signaling in Myeloid Cells Orchestrates Inflammation Resolution and Muscle Repair

Glucocorticoids are key regulators of inflammation and tissue repair, yet their precise role in muscle regeneration remains incompletely understood. Here, we investigate the impact of myeloid-specific glucocorticoid receptor (GR) invalidation on macrophage dynamics and muscle stem cell function following acute injury. We demonstrate that the loss of GR in myeloid cells leads to increased macrophage accumulation, driven by altered proliferation and recruitment, without affecting fibro-adipogenic progenitor differentiation or satellite cell proliferation and differentiation under steady-state conditions. Transcriptomic and cistrome analyses at early regeneration stages reveal that GR directly regulates gene networks involved in efferocytosis and cell cycle control in myeloid cells. Importantly, administration of dexamethasone during the pro-inflammatory phase markedly delays muscle regeneration by impairing monocyte-to-macrophage transition and promoting macrophage proliferation in a myeloid-GR dependent manner, ultimately reducing satellite cell proliferation and myogenesis. In contrast, dexamethasone treatment during the anti-inflammatory phase exerts limited effects on muscle recovery. Together, our findings uncover a critical temporal role of GR signaling in myeloid cells in coordinating inflammatory resolution and stem cell function during muscle repair, and highlight the complexity of glucocorticoid actions in regenerative contexts.

developmental biology↗

Dual role of Human antigen R in Dengue virus infection: suppression of replication and promotion of cap-independent translation

Host RNA-binding proteins (RBPs) play a pivotal role in regulating dengue virus (DENV) translation and replication through interactions with untranslated regions (UTRs) of viral RNA. We investigated host proteins associated with detergent-resistant membranes (DRMs) of the DENV replication complex and identified Human antigen R (HuR) as a key RBP enriched in the DRM. HuR was found to negatively regulate DENV replication by binding the DENV-3'UTR and impeding the association of polypyrimidine tract-binding protein (PTB), a known RNA stabilizer. Additionally, infection-induced modulation of HuR stabilized host mRNAs involved in innate immunity. Interestingly, in vivo validation in AG129 mice model highlights an inverse correlation between HuR expression and viral load and implicates HuR in cytokine dysregulation. Notably, HuR promoted cap-independent translation of viral RNA during later stages of infection, when cap-dependent translation is suppressed. These findings reveal a dual role for HuR: restricting viral RNA replication while enhancing translation, highlighting its critical, phase-specific function in the DENV life cycle. Author summaryUnderstanding how Dengue virus interacts with human cells is key to finding better treatments. Our study looked at a human protein called HuR, which normally control the stability and the use of RNA inside our cells. We discovered that HuR has two important but opposite roles during dengue infection. Early on, it slows down the viruss ability to make copies of its genetic material, helping to reduce infection. But later, when the virus struggles to use the normal method of making proteins, HuR steps in to help the virus make its proteins in a different way. This double-edged role of HuR shows how the virus cleverly uses host cell machinery at different stages of infection. Overall, this study uncovers the novel role of a specific RNA-binding protein of the host in orchestrating dengue virus infection and pathogenesis, highlighting its potential as a target for antiviral therapies. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=110 SRC="FIGDIR/small/666571v1_ufig1.gif" ALT="Figure 1"> View larger version (16K): org.highwire.dtl.DTLVardef@1a5a0fdorg.highwire.dtl.DTLVardef@ec7734org.highwire.dtl.DTLVardef@860cf0org.highwire.dtl.DTLVardef@bb65f5_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

Macrophage Cholesterol Homeostasis Underpins the role of Sertraline as an Adjunctive Agent in Tuberculosis Therapy.

Cellular metabolism plays a deterministic role in the macrophage responses to intracellular pathogens such as Mycobacterium tuberculosis (Mtb) and infection control. Here, we demonstrate that the significant rewiring of the macrophage cholesterol metabolism by sertraline (SRT), an FDA-approved antidepressant, effectively enhances bacterial control. SRT, by virtue of its potent cationic amphiphilicity leads to the accumulation of lysosomal cholesterol in macrophages and activating the transcription factor SREBP2 and enhancing cholesterol biosynthesis. By specific gene silencing and biochemical inhibition assays, we further demonstrate that this metabolic reprogramming promotes lysosomal membrane permeabilization, mitochondrial reactive oxygen species (ROS) generation, heightened IL-1{beta} release, collectively enhancing macrophage bactericidal activity. Our results thus highlight a previously underappreciated link between cholesterol homeostasis and inflammasome activation, which contributes to improved Mtb clearance in the presence of adjunctive sertraline therapy. Statement of significanceTuberculosis remains a leading cause of global mortality, and treatment success is limited due to a long treatment regimen. This study identifies macrophage cholesterol homeostasis as a central pathway to enhance anti-tubercular therapy. We show that Sertraline, an FDA-approved antidepressant, a cationic amphiphilic drug (CAD), reprograms cholesterol trafficking through NPC1 inhibition. This drives the consequential processing of the master regulator SREBP2, accompanied by lysosomal membrane permeabilization. Collectively, these lead to mitochondrial ROS production and activation of NLRP3 signalling, boosting inflammasome-mediated bacterial clearance. By establishing cholesterol sequestration as the mechanistic basis of host-directed activity of sertraline and distinguishing it from ineffective CADs, our work provides a mechanistic framework for developing cholesterol-modulating host-directed adjuncts to improve TB treatment outcomes. Graphical abstract: SRT induced lysosomal cholesterol accumulation results in enhanced bacterial control via inflammasome activation O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=101 SRC="FIGDIR/small/665474v3_ufig1.gif" ALT="Figure 1"> View larger version (34K): org.highwire.dtl.DTLVardef@1019b4dorg.highwire.dtl.DTLVardef@7b0ae8org.highwire.dtl.DTLVardef@9297eorg.highwire.dtl.DTLVardef@1832bef_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

Human antigen R differentially modulates the translation of SARS-CoV-2 genomic and sub-genomic RNAs

Severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) viral RNA associates with different RNA-binding host proteins at each stage of its life cycle. We found sequence dependent binding of one such important protein, human antigen R (HuR) to SARS-CoV-2 5'UTR and studied its potential role in virus life cycle. The knockdown and knockout studies revealed importance of such binding in viral translation. We identified 5'-UTR mutations in SARS-CoV-2 variants of concern that altered the HuR-binding affinity. Interestingly, HuR enhanced non-structural protein translation through the genomic 5'-UTR, by promoting polypyrimidine tract-binding protein binding to the 5'-UTR. However, HuR suppressed the structural protein translation from sub genomic 5UTR. HuR knockout increased the sensitivity to remdesivir treatment by decreasing its half-maximal inhibitory concentration. An antisense oligonucleotide (whose binding site overlapped the HuR-binding site) reduced viral RNA levels in wild-type cells but not HuR-knockout cells. Our results indicate that HuR regulates the balance between SARS-CoV-2 structural and non-structural proteins and guides the infection of viral variants, implying that HuR can potentially be targeted for therapeutic interventions. Author SummaryViruses interacts with various host proteins throughout their life cycle. One significant protein is HuR, an RNA-binding protein that regulates RNA stability and translation. HuR binds to viral RNAs at the 5UTR or 3UTR, impacting their translation and replication. We identified conserved HuR binding sites in the SARS-CoV-2 5UTR across different beta coronaviruses. This binding enhanced the initiation of translation from the genomic 5 UTR, increasing the production of non-structural proteins essential for viral replication. Additionally, we discovered that another host protein, PTB, promotes HuR binding to the viral 5 UTR, facilitating its loading onto ribosomes. Conversely, HuR plays an antagonistic role concerning subgenomic RNAs (sgRNAs), which code for structural proteins, by regulating and limiting their levels. This dual regulation indicates that the virus exploits HuR for its benefit while the host employs it to control viral spread. Targeting HuR may help manipulate the SARS-CoV-2 life cycle. We found that HuR knockout increased sensitivity to the antiviral drug Remdesivir. Using an antisense oligonucleotide to block HuR binding effectively reduced viral RNA levels. Our findings highlight the critical role of HuR in regulating viral protein production and its potential as a therapeutic target.

microbiology↗

Transgenic Mouse Models Establish a Protective Role of Type 1 IFN Response in SARS-CoV-2 infection-related Immunopathology

Type 1 interferon (IFN-I) response is the first line of host defense against invading viruses. In the absence of definite mouse models, the role of IFN-I in SARS-CoV-2 infections remained to be perplexing. Here, we developed two mouse models, one with constitutively high IFN-I response (hACE2; Irgm1-/-) and the other with dampened IFN-I response (hACE2; Ifnar1-/-) to comprehend the role of IFN-I response during SARS-CoV-2 invasion. We found that hACE2; Irgm1-/- mice were resistant to lethal SARS-CoV-2 infection with substantially reduced cytokine storm and immunopathology. In striking contrast, a severe SARS-CoV-2 infection along with immune cells infiltration, inflammatory response, and enhanced pathology was observed in the lungs of hACE2; Ifnar1-/- mice. Additionally, hACE2; Ifnar1-/- mice were highly susceptible to SARS-CoV-2 neuroinvasion in the brain accompanied by immune cell infiltration, microglia/astrocytes activation, cytokine response, and demyelination of neurons. The hACE2; Irgm1-/- Ifnar1-/- double knockout mice or hACE2; Irgm1-/- mice treated with STING or RIPK2 pharmacological inhibitors displayed loss of the protective phenotypes observed in hACE2; Irgm1-/- mice suggesting that heightened IFN-I response accounts for the observed immunity. Taken together, we explicitly demonstrate that IFN-I protects from lethal SARS-CoV-2 infection, and Irgm1 (IRGM) could be an excellent therapeutic target. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=133 SRC="FIGDIR/small/520843v1_ufig1.gif" ALT="Figure 1"> View larger version (51K): org.highwire.dtl.DTLVardef@a3aad4org.highwire.dtl.DTLVardef@12452fcorg.highwire.dtl.DTLVardef@1c43dc0org.highwire.dtl.DTLVardef@b2167d_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

Autoimmunity Risk Gene IRGM is a Master Negative Regulator of Interferon Response by Controlling the Activation of cGAS STING and RIG-I-MAVS Signaling Pathways

Activation of type 1 interferon response is extensively connected with the antiviral immunity and pathogenesis of autoimmune diseases. Here, we found that IRGM, whose deficiency is linked with the genesis of several autoimmune disorders, is a master negative regulator of the interferon response. Mechanistically, we show that IRGM interacts with nucleic acid sensor proteins, including cGAS and RIG-I, and mediates their autophagic degradation to restrain activation of interferon signaling. Further, IRGM maintains mitophagy flux, and its deficiency results in the accumulation of defunct leaky mitochondria that releases cytosolic DAMPs triggering activation of interferon responses via cGAS-STING and RIG-I-MAVS signaling axis. Due to an enduring type 1 IFN response in IRGM-deficient cells and mice, they were intrinsically resistant to infection of the Japanese Encephalitis virus, Herpes Simplex virus, and Chikungunya virus. Altogether, this study defines the molecular mechanisms by which IRGM maintains interferon homeostasis and protects from autoimmune diseases. Further, it identifies IRGM as a broad therapeutic target for defense against viruses.\n\nGraphical Abstract\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=126 SRC=\"FIGDIR/small/815506v1_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (48K):\norg.highwire.dtl.DTLVardef@1d4822org.highwire.dtl.DTLVardef@6aebbcorg.highwire.dtl.DTLVardef@19a9b72org.highwire.dtl.DTLVardef@1539195_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗