Biology subjects

Naeem, R.

Publications and source records attributed to Naeem, R..

3 recordsLinked to original sources

bioRxiv2022

Glutamine mimicry suppresses tumor progression through asparagine metabolism in pancreatic ductal adenocarcinoma

In pancreatic ductal adenocarcinoma (PDAC), glutamine is a critical nutrient that drives a wide array of metabolic and biosynthetic processes that support tumor growth. Despite this established dependency, the targeting of specific enzymes involved in glutamine metabolism is yet to yield any clinical benefit. Here, we have examined the therapeutic potential of 6-diazo-5-oxo-L-norleucine (DON), a glutamine antagonist that broadly inhibits glutamine metabolism. We found that DON treatment significantly blocks PDAC tumor growth and attenuates metastasis. Interestingly, we link the effectiveness of DON in PDAC to asparagine (Asn) metabolism. By inhibiting asparagine synthetase (ASNS), DON significantly reduces intracellular Asn production and Asn supplementation rescues the anti-proliferative effects of DON. We discern that PDAC cells upregulate expression of ASNS as a metabolic adaptation and that modulating ASNS levels can impact DON efficacy. Strikingly, in patient-derived organoids, DON responsiveness is inversely correlated with ASNS expression, a feature that is not observed for other metabolic enzymes targeted by DON. We find that treatment with L-asparaginase (ASNase), an enzyme that catabolizes free Asn, synergizes with DON to impact the viability of PDAC cells. Finally, we identify that a combination therapy of DON and ASNase has a significant impact on metastasis. These results shed light on the mechanisms that drive the effects of glutamine mimicry and point to the utility of co-targeting adaptive responses to control PDAC progression.

cancer biology↗

bioRxiv2022

Illuminating histidine phosphorylation in the pancreatic tumor microenvironment

Development of phosphohistidine (pHis) antibodies has significantly advanced our understanding of pHis contributions to tumor biology, including a tumor suppressive role for a pHis phosphatase, a metastasis suppressive role for His kinases, and pHis regulation of T cell receptor signaling. Using these antibodies, we investigated pHis pathway regulation in the mouse pancreatic tumor microenvironment. We identified deregulated expression of pHis and pHis phosphatases that correlated with mouse pancreatic tumor progression. We developed a protocol to circumvent the acid and heat-sensitivity of pHis signals, enabling their co-staining with other proteins in FFPE tissue, identifying a significant enrichment of 1-pHis and a subtype of 3-pHis signals (Gly-3-pHis) in the stroma. We discovered increased Gly-3-pHis levels in tumor-associated myeloid cells mainly resulting from elevated ATP citrate lyase 3-pHis levels and predicted the existence of pHis in cell-cell adhesion proteins. We provide evidence that mitochondrial delocalization of PGAM5, a pHis phosphatase with increased expression during pancreatic tumorigenesis, occurs in tumor cells as compared to stromal cells, enabling access to PGAM5s known cytoplasmic substrate, pHis-NME (Non-MEtastatic), and two potential Gly-3-pHis substrates, SCS (Succinyl CoA Synthetase) and {beta}-catenin. Overall, we introduce a new method and possible targets for future studies of pHis pathway deregulation during tumorigenesis.

cancer biology↗

bioRxiv2018

WhiB6 is required for the secretion-dependent regulation of ESX-1 substrates in pathogenic mycobacteria.

The mycobacterial type VII secretion system ESX-1 is responsible for the secretion of a number of proteins that play important roles during host infection. The regulation of the expression of secreted proteins is often essential to establish successful infection. Using transcriptome sequencing, we found that the abrogation of ESX-1 function in Mycobacterium marinum leads to a pronounced increase in gene expression levels of the espA operon during the infection of macrophages, suggesting an important role in ESX-1-mediated virulence during the early phase of infection. In addition, the disruption of ESX-1-mediated protein secretion also leads to a specific down-regulation of the ESX-1 substrates, but not of the structural components of this system, during growth in culture medium. This effect is observed in both M. marinum and M. tuberculosis. We established that down-regulation of ESX-1 substrates is the result of a regulatory process that is influenced by the putative transcriptional regulator whib6, which is located adjacent to the esx-1 locus. In addition, the overexpression of the ESX-1-associated PE35/PPE68 protein pair resulted in a significantly increased secretion of the ESX-1 substrate EsxA, demonstrating a functional link between these proteins. Taken together, these data show that WhiB6 is required for the secretion-dependent regulation of ESX-1 substrates and that ESX-1 substrates are regulated independently from the structural components, both during infection and as a result of active secretion.

microbiology↗