Biology subjects

Sundaramurthy, V.

Publications and source records attributed to Sundaramurthy, V..

6 recordsLinked to original sources

bioRxiv2025

Cell cycle-dependent variation in endocytosis drives phenotypic diversity in M. tuberculosis

Cell-to-cell heterogeneity is a hallmark of biology, yet how host variability shapes intracellular pathogen phenotypes is unclear. Using single cell approaches and redox-sensitive Mycobacterium tuberculosis reporters, we reveal that interphase-driven shifts in endocytic capacity create distinct intracellular niches. Bacilli residing in high-endocytic G2 cells adopt more oxidized redox states, whereas those in low-endocytic G1 cells remain reduced, generating phenotypic diversity within a single infected population. Experimental manipulation of host cell cycle stage reprograms endocytic capacity and intrabacterial redox, establishing a causal link between host state and pathogen diversification. Notably, the finding that the cell cycle regulates endocytic capacity constitutes a fundamental cell-biological discovery with broad implications. This variability persists in post-differentiated macrophages, indicating that proliferative history imprints functional diversity onto innate immune cells. Together, these results identify interphase-regulated endocytosis as a host-intrinsic mechanism that shapes Mycobacterium tuberculosis phenotypes and suggest new host-directed avenues to influence infection trajectories and persistence.

cell biology↗

bioRxiv2025

DNMT3A Stability Is Maintained by Ubiquitin-Specific Peptidase 11 (USP11) and Sumoylation Countering Degradation

DNA methyltransferase 3A (DNMT3A) plays crucial roles in mammalian development and hematopoiesis. DNMT3A protein instability is associated with blood diseases such as myelodysplastic syndrome (MDS), acute myeloid leukemia (AML), as well as Tatton-Brown-Rahman syndrome, an overgrowth disorder. We found that certain unstable DNMT3A mutations cause DNMT3A localization changes, resulting in loss of function. This mislocalization is partially rescued by E1 enzyme inhibition or stable USP11 expression, as DNMT3A stability is maintained by deubiquitinating enzyme USP11 countering degradation by CUL4-DCAF8 E3 ligase. We also found that USP11 enhances DNMT3A SUMOylation by promoting the interaction between DNMT3A and SUMO E3 ligases. DNMT3A SUMOylation also is essential to maintain DNMT3A protein stability. Furthermore, we found USP11 enhances the binding of DNMT3A to the polycomb complex and maintains DNMT3A DNA methyltransferase (MTase) activity. This study uncovers the mechanism for DNMT3A protein turnover through USP11, which is essential to DNMT3A function, and may be a therapeutic approach for diseases caused by DNMT3A protein instability.

biochemistry↗

bioRxiv2022

Niacinamide enhances cathelicidin mediated SARS-CoV-2 membrane disruption

The continual emergence of new SARS-CoV-2 variants threatens the effectiveness of worldwide vaccination programs and highlights the need for complementary strategies for a sustainable containment plan. A promising approach is to mobilize the bodys own antimicrobial peptides (AMPs), to combat SARS-CoV-2 infection and propagation. We have found that human cathelicidin (LL37), an AMP found at epithelial barriers as well as in various bodily fluids, has the capacity to neutralise multiple strains of SARS-CoV-2. Biophysical and computational studies indicate that LL37s mechanism of action is through the disruption of the viral membrane. This antiviral activity of LL37 is enhanced by the hydrotropic action of niacinamide, which may increase the bioavailability of the AMP. Interestingly, we observed inverse correlation between LL37 levels and disease severity of COVID-19 positive patients, suggesting enhancement of AMP response would be an effective therapeutic avenue to mitigate disease severity and overcome vaccine escape.

pathology↗

bioRxiv2020

Niclosamide inhibits SARS-CoV2 entry by blocking internalization through pH-dependent CLIC/GEEC endocytic pathway

Many viruses utilize the host endo-lysosomal network to infect cells. Tracing the endocytic itinerary of SARS-CoV2 can provide insights into viral trafficking and aid in designing new therapeutic targets. Here, we demonstrate that the receptor binding domain (RBD) of SARS-CoV2 is internalized via the clathrin and dynamin-independent, pH-dependent CLIC/GEEC (CG) endocytic pathway. Endosomal acidification inhibitors like BafilomycinA1 and NH4Cl, which inhibit the CG pathway, strongly block the uptake of RBD. Using transduction assays with SARS-CoV2 Spike-pseudovirus, we confirmed that these acidification inhibitors also impede viral infection. By contrast, Chloroquine neither affects RBD uptake nor extensively alters the endosomal pH, yet attenuates Spike-pseudovirus entry, indicating a pH-independent mechanism of intervention. We screened a subset of FDA-approved acidification inhibitors and found Niclosamide to be a potential SARS-CoV2 entry inhibitor. Niclosamide, thus, could provide broader applicability in subverting infection of similar category viruses entering host cells via this pH-dependent endocytic pathway.

cell biology↗

bioRxiv2020

Acidosis, Zinc and HMGB1 in Sepsis: A Common Connection Involving Sialoglycan Recognition

Blood pH is tightly regulated between 7.35-7.45, with values below 7.3 during sepsis being associated with lactic acidosis, low serum zinc, and release of proinflammatory HMGB1 from activated and/or necrotic cells. Using an ex vivo whole blood system to model lactic acidosis, we show that while HMGB1 does not engage leukocyte receptors at physiological pH, lowering pH with lactic acid facilitates binding. At normal pH, micromolar zinc supports plasma sialoglycoprotein binding by HMGB1, which is markedly reduced when pH is adjusted with lactic acid to sepsis levels. Glycan array studies confirmed zinc and pH-dependent HMGB1 binding to sialoglycans typical of plasma glycoproteins. Thus, proinflammatory effects of HMGB1 are suppressed via plasma sialoglycoproteins until drops in pH and zinc release HMGB1 to trigger downstream immune activation. Significance StatementHMGB1 sequestered by plasma sialoglycoproteins at physiological pH is released when pH and zinc concentrations fall in sepsis.

immunology↗

bioRxiv2019

Robust lysosomal rewiring in Mtb infected macrophages mediated by Mtb lipids restricts the intracellular bacterial survival

Intracellular pathogens commonly manipulate the host lysosomal system for their survival, however whether this affects the organization and functioning of the lysosomal system itself is not known. Here, we show using in vitro and in vivo infections that the lysosomal content and activity is globally elevated in M. tuberculosis infected macrophages. The enhanced lysosomal state is sustained over time and defines an adaptive homeostasis of the infected cell. Lysosomal alterations are caused by mycobacterial surface components, notably the cell wall lipid SL-1, which functions through the mTORC1-TFEB axis. Mtb mutant defective for SL-1 levels shows reduced lysosomal content and activity compared to wild type. Importantly, this phenotype is conserved during in vivo infection. The alteration in lysosomal phenotype in mutant Mtb lead to decreased lysosomal delivery of Mtb, and importantly, increased survival of intracellular Mtb. These results define the global alterations in the host lysosomal system as a crucial distinguishing feature of Mtb infected macrophages that is host protective and contribute to the containment of the pathogen.

cell biology↗