Biology subjects

Balaji, K. N.

Publications and source records attributed to Balaji, K. N..

10 recordsLinked to original sources

bioRxiv2026

Lysine specific demethylase 1 (LSD1) regulates host alpha-ketoglutarate levels to modulate lipid peroxidation during Mycobacterium tuberculosis infection

Mycobacterium tuberculosis (Mtb) subverts host immune responses via modulation of host epigenome and metabolism. In this study, we underscore a role for the epigenetic modifier, Lysine Specific Demethylase 1 (LSD1), in regulating macrophage metabolism to support mycobacterial pathogenesis. In ex vivo and in vivo infection models, LSD1 inhibition reduced mycobacterial CFU alleviating lung pathology. Metabolomic analysis of Mtb infected, LSD1 deficient macrophages revealed increased levels of alpha-ketoglutarate (AKG), a crucial TCA cycle metabolite via regulating genes implicated in glutamine breakdown. Moreover, exogenous addition of AKG resulted in reduced oxidative stress and attenuated lipid peroxidation (LPO) with a consequent decrease in Mtb survival. Blocking glutamine breakdown in LSD1 deficient macrophages failed to reduce LPO and promoted Mtb intracellular survival, highlighting the role of LSD1-AKG axis in this immunomodulation. Dietary supplementation of AKG to Mtb infected mice improved lung pathology, limited Mtb dissemination and reduced the levels of oxidative Malondialdehyde adducts. Therefore, we highlight a host protective role of AKG during Mtb pathogenesis through suppression of lipid peroxidation and uncover an epigenetic-metabolic axis exploited by Mtb, thereby positing dietary supplementation of AKG as a potential therapeutic strategy against Tuberculosis.

immunology↗

bioRxiv2025

Infection with Mycobacterium tuberculosis orchestrates the PRMT5-dependent methylation of NCOA4 to govern host ferroptosis

Mycobacterium tuberculosis (Mtb) increases availability of free iron resulting in ferroptosis of host macrophages to facilitate its survival and dissemination. A critical factor for elevated levels of labile iron is the overt accumulation of the protein nuclear receptor coactivator 4 (NCOA4), that promotes autophagic degradation of ferritin in a process termed as ferritinophagy. Here, we identify a novel post-translational modification on NCOA4 that is essential for its interaction with ferritin in iron-replete condition of Mtb-infected cells. Specifically, protein arginine methyltransferase 5 (PRMT5), confers a symmetric-dimethylation on NCOA4 that promotes ferritinophagy-mediated ferroptosis. Using loss-of-function studies, we show that PRMT5 is required for lipid peroxidation, bacterial survival, and dissemination in Mtb-infected mice. Also, overexpression of a methylation-deficient mutant of NCOA4 phenocopy depletion of PRMT5 and reduced ferritinophagy in Mtb-infected cells. Furthermore, PRMT5-mediated methylation reduces the nuclear availability of NCOA4 and impairs its co-activatory role to nuclear receptors such as vitamin D3. Thus, our findings uncover the key interaction between NCOA4 and ferritin that regulates ferroptosis and mycobacterial survival during infection. Perturbation of this interaction results in reduced Mtb loads and alleviated disease pathology.

microbiology↗

bioRxiv2025

Activin A mediated KAT8 expression induces ferroptosis during Mycobacterium tuberculosis infection

Activin A, a secretory glycoprotein, has been shown to be upregulated in TB patients, and its levels are correlated with disease severity. Here, we identify a functional role for activin A and the downstream SMAD2/3 signalling in Mtb pathogenesis and dissemination. Molecular assays, including ChIP and loss-of-function analysis, demonstrated that Activin A regulates the expression of lysine acetyltransferase (KAT) 8, which in turn regulates HO-1 levels and Mtb-induced ferroptosis. Mechanistically, we identify KAT8-mediated acetylation of NRF2 during Mtb infection, leading to enhanced nuclear availability of the transcription factor and increased expression of HO-1. Finally, utilizing an in vivo mouse model of TB, we show that the pharmacological inhibition of activin A receptor and KAT8 restricts Mtb burden, dissemination and ameliorates TB pathology. Thus, we report a novel role for activin A in regulating NRF2 localisation and outline its potential consequences during TB.

immunology↗

bioRxiv2024

Deregulation of epigenetic factor, KDM6A, is involved during Candida albicans mediated delayed wound healing

Deregulation of wound healing process leads to chronic non-healing wounds. Opportunistic fungal pathogens like Candida albicans is known to colonize open wounds leading to delayed, insufficient, or disorganized healing. In our study, we investigate the regulatory mechanisms orchestrating this C. albicans mediated delay of wound healing and underscore a critical role for the transcription factor c-AMP Response Element Binding Protein (CREB) in regulating pro-inflammatory cytokines and genes implicated in wound healing. Parallelly, we found the epigenetic factor, KDM6A (Ubiquitously Transcribed tetratricopeptide repeat on chromosome X, also known as UTX) to be downregulated upon infection and modulating expression of metalloproteinases during C. albicans governed wound healing impairment. Mechanistically, we observed enhanced recruitment of EZH2, a methyl transferase, over the promoters of KDM6A during infection, hence, governing its expression. Our findings, therefore, underscore a role of KDM6A and CREB in C. albicans mediated delayed wound healing.

immunology↗

bioRxiv2024

Histone demethylase LSD1 regulates lipid homeostasis duringCryptococcus neoformans infection

An opportunistic fungal pathogen, Cryptococcus neoformans (C. neoformans), causes cryptococcal meningitis and is frequently associated with high mortality in immunocompromised individuals, particularly in HIV patients. Formation of metabolically altered lipid-rich foamy macrophages has been reported as a successful strategy employed by various intracellular pathogens to secure a nutrient source and niche within the host. Herein, we elucidate the involvement of macroautophagy, specifically lipophagy, in lipid dysregulation during C. neoformans infection. Our study highlights a pivotal role of lipophagy during infection, showing that C. neoformans driven activation of WNT-signaling leads to an aberrant lipid accumulation in host macrophages under the regulatory role of a histone modifier, Lysine Specific Demethylase 1 (LSD1). In a murine model of pulmonary infection, targeting host LSD1 led to a significant reduction in lung fungal burden, accompanied by amelioration of lung pathology and reduction of lipid content in the lungs. The study highlights the significance of host epigenetic regulation in modulating foamy macrophage formation through the regulation of lipophagy during C. neoformans pathogenesis.

immunology↗

bioRxiv2022

Mycobacterium tuberculosis infection elevates SLIT2 expression to modulate oxidative stress responses in macrophages

Mycobacterium tuberculosis (Mtb), the causative agent of the pulmonary ailment, tuberculosis (TB), continues to thrive owing to a disorganized immune response against it by the host. Among other factors, the rewiring of distinct host signaling pathways is effectuated by the intracellular bacterium, resulting in pathogen-favorable outcomes. Oxidative stress build-up is a key cellular manifestation that occurs during mycobacterial infection. Enhanced oxidative stress is brought about by the cumulative effect of elevated reactive oxygen species generation as well as the inept ability of the cell to mitigate ROS levels. Here, we report the increased expression of the neuronal ligand, SLIT2, during mycobacterial infection in macrophages. By employing loss of function analysis using specific inhibitors, we attribute the heightened expression of SLIT2 to the Mtb-mediated phosphorylation of the p38/JNK pathways. Also, using chromatin immunoprecipitation (ChIP) analysis, we found reduced levels of the repressive H3K27me3 signature on the Slit2 promoter during mycobacterial infection. Furthermore, SLIT2 was found to promote the expression of cellular pantetheinase, Vanin1 (VNN1), that contributed to copious levels of ROS within the macrophage cellular milieu. Thus, we dissect essential molecular details leading to the robust expression of SLIT2 during Mtb infection while outlining the potential consequences of SLIT2 upregulation in infected macrophages. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=143 SRC="FIGDIR/small/512188v1_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@352ec6org.highwire.dtl.DTLVardef@19209e5org.highwire.dtl.DTLVardef@c7c546org.highwire.dtl.DTLVardef@168ab61_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2021

PRMT5 epigenetically regulates the E3 ubiquitin ligase ITCH to influence lipid accumulation during mycobacterial infection

Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), triggers enhanced accumulation of lipids to generate foamy macrophages (FMs). This process has been often attributed to the surge in the expression of lipid influx genes with a concomitant decrease in those involved in lipid efflux genes. Here, we define an Mtb-orchestrated modulation of the ubiquitination mechanism of lipid accumulation markers to enhance lipid accretion during infection. We find that Mtb infection represses the expression of the E3 ubiquitin ligase, ITCH, resulting in the sustenance of key lipid accrual molecules viz. ADRP and CD36, that are otherwise targeted by ITCH for proteasomal degradation. In line, overexpressing ITCH in Mtb-infected cells was found to suppress Mtb-induced lipid accumulation. Molecular analyses including loss-of-function and ChIP assays demonstrated a role for the concerted action of the transcription factor YY1 and the arginine methyl transferase PRMT5 in restricting the expression of Itch gene by conferring repressive symmetrical H4R3me2 marks on its promoter. Consequently, siRNA-mediated depletion of YY1 or PRMT5 rescued ITCH expression, thereby compromising the levels of Mtb-induced ADRP and CD36 and limiting FM formation during infection. Accumulation of lipids within the host has been implicated as a pro-mycobacterial process that aids in pathogen persistence and dormancy. In our study, perturbation of PRMT5 enzyme activity resulted in compromised lipid levels and reduced mycobacterial survival in primary murine macrophages (ex vivo) and in a therapeutic mouse model of TB infection (in vivo). These findings provide new insights on the role of PRMT5 and YY1 in augmenting mycobacterial pathogenesis. Thus, we posit that our observations could help design novel adjunct therapies and combinatorial drug regimen for effective anti-TB strategies. Author SummaryMycobacterium tuberculosis generates lipid-laden cells (foamy macrophages-FMs) that offer a favorable shelter for its persistence. During infection, we observe a significant reduction in the expression of the E3 ubiquitin ligase, ITCH. This repression allows the sustenance of key lipid accretion molecules (ADRP and CD36), by curbing their proteasomal degradation. Further, we show the repression of ITCH to be dependent on the concerted action of the bifunctional transcription factor, YY1 and the arginine methyl transferase, PRMT5. NOTCH signaling pathway was identified as a master-regulator of YY1 expression. In vitro and in vivo analyses revealed the significance of PRMT5 in regulating FM formation and consequently mycobacterial burden.

microbiology↗

bioRxiv2021

Combinatorial transcriptional codes specify macrophage polarization destinations

Macrophages are driven to form distinct functional phenotypes in response to different immunological stimuli, in a process widely referred to as macrophage polarization. Transcriptional regulators that guide macrophage polarization in response to a given trigger remain largely unknown. In this study, we interrogate the programmable landscape in macrophages to find regulatory panels that determine the precise polarization state that a macrophage is driven to. Towards this, we configure an integrative network analysis pipeline that utilizes macrophage transcriptomes in response to 28 distinct stimuli and reconstructs contextualized human gene regulatory networks, and identifies epicentres of perturbations in each case. We find that these contextualized regulatory networks form a spectrum of thirteen distinct clusters with M1 and M2 at the two ends. Using our computational pipeline, we identify combinatorial panels of epicentric regulatory factors (RFs) for each polarization state. We demonstrate that a set of three RFs i.e., CEBPB, NFE2L2 and BCL3, is sufficient to change the polarization destination from M1 to M2. siRNA knockdown of the 3-RF set in THP1 derived M0 cells, despite exposure to an M1 stimulant, significantly attenuated the shift to M1 phenotype, and instead increased the expression of M2 markers. Single knockdown of each RF also showed a similar trend. The siRNA-mediated knockdown of the 3-RF set rendered the macrophages hyper-susceptible to Staphylococcus aureus infection, demonstrating the importance of these factors in modulating immune responses. Overall, our results provide insights into the transcriptional mechanisms underlying macrophage polarization and identify key regulatory factors that may be targeted to modulate immune responses.

systems biology↗

bioRxiv2021

Preexisting mycobacterial infection modulates Candida albicans-driven pyroptosis

Active tuberculosis patients are at high risk of co-infection with opportunistic fungal pathogen C. albicans. However, the molecular mechanisms that orchestrate pathogenesis of Mycobacterium tuberculosis (Mtb)-C. albicans co-infection remains elusive. In the current study, we utilise a mouse model to demonstrate that Mtb promotes macrophage environment conducive for C. albicans survival. Mtb-dependent PKC{zeta}-WNT signalling axis induces expression of an E3 ubiquitin ligase, COP1. A secondary infection of C. albicans in such Mtb-infected macrophages causes COP1 to mediate the proteasomal degradation of IRF9, a cardinal factor that we identified to arbitrate an inflammatory programmed cell death, pyroptosis. In vivo experiments mimicking a preexisting Mtb infection demonstrate that inhibition of pyroptosis in mice results in increased C. albicans burden and aberrant lung tissue architecture, leading to increased host mortality. Together, our study reveals the crucial role of pyroptosis regulation for manifesting a successful C. albicans-Mtb co-infection.

microbiology↗

bioRxiv2021

G9a and Sirtuin6 epigenetically modulate host cholesterol accumulation to facilitate mycobacterial survival

Cholesterol derived from the host milieu forms a critical factor for mycobacterial pathogenesis. However, the molecular circuitry co-opted by Mycobacterium tuberculosis (Mtb) to accumulate cholesterol in host cells remains obscure. Here, we report that a functional amalgamation of WNT-responsive histone modifiers G9a (H3K9 methyltransferase) and Sirt6 (H3K9 deacetylase) orchestrate cholesterol build-up in in-vitro and in-vivo models of Mtb infection. Mechanistically, G9a, along with SREBP2, drives the expression of cholesterol biosynthesis and uptake genes; while Sirt6 represses the genes involved in cholesterol efflux. The accumulated cholesterol promotes the expression of antioxidant genes leading to reduced oxidative stress, thereby supporting Mtb survival. In corroboration, loss-of-function of G9a in vitro and in vivo by pharmacological inhibition; or utilization of BMDMs derived from Sirt6 KO mice or in vivo infection in Sirt6 heterozygous mice; hampers host cholesterol accumulation and restricts Mtb burden. These findings shed light on the novel roles of G9a and Sirt6 during Mtb infection and highlight the previously unknown contribution of host cholesterol in potentiating anti-oxidative responses for aiding Mtb survival.

microbiology↗