Biology subjects

Mondal, D. K.

Publications and source records attributed to Mondal, D. K..

3 recordsLinked to original sources

bioRxiv2026

Functional characterization of a cytosolic malic enzyme crucial for pyridine nucleotide homeostasis, redox balance, and virulence in Leishmania major

Malic enzymes (MEs) occupy a central node in metabolism, by catalyzing the reversible oxidative decarboxylation of malate to pyruvate, thereby contributing to maintenance of NADPH homeostasis. Leishmania spp. are known to encode two ME isoforms, however only one from Leishmania major has been functionally characterised till date to be a mitochondrial enzyme, playing critical role in gluconeogenesis. Here, we cloned and functionally characterized the second isoform, LmME2. Colocalization and subcellular fractionation analysis established that LmME2 localizes to the cytosol. Kinetic analyses of purified LmME2 revealed comparable rates of malate decarboxylation and pyruvate carboxylation, however, pyruvate carboxylation predominated in parasite cell lysates, indicating that the directionality of the reaction is metabolically regulated in cellular environment. Consistent with this, we identified oxaloacetate, ATP and fumarate as allosteric modulators of LmME2 activity. To dissect its physiological role, we generated CRISPR-Cas9-mediated LmME2 knockout parasites (LmME2-/-). Interestingly, LmME2 deletion did not alter NADPH levels but depleted both NADP+ and NAD+ pools, with reduction in NAD+ being more pronounced. This disruption of pyridine nucleotide homeostasis resulted in elevated intracellular ROS levels. Furthermore, inhibition of the pentose phosphate pathway, the alternative cytosolic source of NADPH, severely impaired the growth of LmME2-/- strain, highlighting the role of LmME2 in maintaining parasite fitness. These metabolic defects translated into markedly diminished intracellular survival of LmME2-/- parasites and its attenuated virulence in mice. Collectively, our findings identify LmME2 as the first functionally characterized cytosolic malic enzyme in Leishmania and establish it as a redox-associated virulence factor. These results further highlight LmME2 as a promising antileishmanial drug target.

cell biology↗

bioRxiv2023

Decorin suppresses tumor lymphangiogenesis: A mechanism to curtail cancer progression

The complex interplay between malignant cells and the cellular and molecular components of the tumor stroma is a key aspect of cancer growth and development. These tumor-host interactions are often affected by soluble bioactive molecules such as proteoglycans. Decorin, an archetypical small leucine-rich proteoglycan primarily expressed by stromal cells, affects cancer growth in its soluble form by interacting with several receptor tyrosine kinases (RTK). Overall, decorin leads to a context-dependent and protracted cessation of oncogenic RTK activity by attenuating their ability to drive a pro-survival program and to sustain a pro-angiogenic network. Through an unbiased transcriptomic analysis using deep RNAseq, we discovered that decorin downregulated a cluster of tumor-associated genes involved in lymphatic vessel development when systemically delivered to mice harboring breast carcinoma allografts. We found that Lyve1 and Podoplanin, two established markers of lymphatic vessels, were markedly suppressed at both the mRNA and protein levels and this suppression correlated with a significant reduction in tumor lymphatic vessels. We further discovered that soluble decorin, but not its homologous proteoglycan biglycan, inhibited lymphatic vessel sprouting in an ex vivo 3D model of lymphangiogenesis. Mechanistically, we found that decorin interacted with VEGFR3, the main lymphatic RTK, and its activity was required for the decorin-mediated block of lymphangiogenesis. Finally, we discovered that Lyve1 was in part degraded via decorin-evoked autophagy in a nutrient- and energy-independent manner. These findings implicate decorin as a new biological factor with anti-lymphangiogenic activity and provide a potential therapeutic agent for curtailing breast cancer growth and metastasis.

cell biology↗

bioRxiv2020

Functional partnership between carbonic anhydrase and malic enzyme in promoting gluconeogenesis in Leishmania major

Leishmania has a remarkable ability to proliferate under widely fluctuating levels of essential nutrients, such as glucose. For this the parasite is heavily dependent on its gluconeogenic machinery. One perplexing aspect of gluconeogenesis in Leishmania is the lack of the crucial pyruvate carboxylase (PC) gene. PC-catalyzed conversion of pyruvate to oxaloacetate is a key entry point through which gluconeogenic amino acids are funnelled into this pathway. Absence of PC in Leishmania thus raises question about the mechanism of pyruvate entry into the gluconeogenic route. We report here that this task is accomplished in Leishmania major through a novel functional partnership between its mitochondrial malic enzyme (LmME) and cytosolic carbonic anhydrase (LmCA1). Using a combination of pharmacological inhibition studies with genetic manipulation, we showed that both these enzymes are necessary in promoting gluconeogenesis and supporting parasite growth under glucose limiting condition. Functional crosstalk between LmME and LmCA1 was evident when it was observed that the growth retardation caused by inhibition of any one of these enzymes could be protected to a significant extent by overexpressing the other enzyme. We also found that while LmCA1 exhibited constitutive expression, LmME protein level was strongly upregulated in low glucose condition. Notably, both LmME and LmCA1 were found to be important for survival of Leishmania amastigotes within host macrophages. Taken together, our results indicate that LmCA1 by virtue of its CO2 concentrating ability stimulates LmME-catalyzed pyruvate carboxylation, thereby driving gluconeogenesis through pyruvate-malate-oxaloacetate bypass pathway. Additionally, our study establishes LmCA1 and LmME as promising therapeutic targets.

biochemistry↗