Biology subjects

Asad, M.

Publications and source records attributed to Asad, M..

6 recordsLinked to original sources

bioRxiv2025

TIGIT expression dictates the immunosuppressive reprogramming of myeloid cells in glioblastoma

Glioblastoma (GBM) is a deadly brain cancer with near-universal recurrence despite maximal treatment for which new innovations are sorely needed. Immunotherapy has yet to make significant gains in GBM treatment despite revolutionizing other cancer therapies, due in part to GBM-mediated immune suppression. This immune derangement proceeds through several mechanisms, but increasing evidence points to critical roles for tumor-derived extracellular vesicles (EVs) and immunosuppressive myeloid cells as key factors in this process. In the present study, we demonstrate broad expression of TIGIT across myeloid cell populations in the GBM microenvironment, a finding recapitulated by conditioning healthy monocytes with GBM-derived EVs. Further, knockdown of TIGIT expression reduced the immunosuppressive polarization of monocytes, resulting in improvement in T cell function. This finding proceeded in an NLRP3-dependent manner, with substantial co-localization of TIGIT and NLRP3 expression prior to knockdown. These findings point to a novel role for TIGIT expression in diverse myeloid cells in the GBM microenvironment as a marker of immunosuppressive activity and further indicate a hierarchy of immunomodulatory protein activity in these myeloid cells, with TIGIT knockdown unmasking the pro-inflammatory activity of NLRP3. This study bolsters understanding of the immunosuppressive complexities of myeloid cells in the GBM microenvironment, while lending further support to prevention or attenuation of immunosuppressive myeloid cell activity as a means of restoring immune function in GBM. Graphical abstract(Created in BioRender. Asad, M. (2025) https://BioRender.com/euiljoq O_FIG O_LINKSMALLFIG WIDTH=153 HEIGHT=200 SRC="FIGDIR/small/648993v2_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@13dc389org.highwire.dtl.DTLVardef@1f06765org.highwire.dtl.DTLVardef@14200forg.highwire.dtl.DTLVardef@144f245_HPS_FORMAT_FIGEXP M_FIG C_FIG Key PointsO_LITumor-mediated immune suppression is a key barrier to the development of effective immunotherapies for GBM. C_LIO_LITIGIT is broadly expressed in myeloid cells within the GBM microenvironment and can be induced by GBM-derived extracellular vesicles. C_LIO_LIKnockdown of TIGIT reduces immunosuppressive polarization of monocytes and enhances T cell activity via NLRP3 signaling, implicating TIGIT expression as a targetable modifier of immunosuppressive activity in GBM-associated myeloid cells. C_LI Importance of the StudyGlioblastoma (GBM) remains a formidable clinical challenge, with poor prognosis and limited response to current immunotherapies. This study uncovers a novel immunosuppressive axis involving TIGIT expression in myeloid cells, which are key players in the GBM tumor microenvironment. By demonstrating GBM-derived extracellular vesicles induce TIGIT in healthy monocytes and TIGIT knockdown diminishes immunosuppressive polarization in an NLRP3-dependent manner, this study highlights TIGIT as both a marker and modulator of immune dysfunction in GBM. These findings introduce a functional hierarchy of immunoregulatory proteins in tumor-associated myeloid cells, positioning TIGIT as a potential checkpoint target. Restoring immune activity by disrupting this axis could enhance the efficacy of immunotherapy in GBM. Thus, this research not only advances our understanding of tumor-induced immune suppression but also opens a promising therapeutic avenue to reinvigorate anti-tumor immunity in a cancer type historically resistant to immunotherapeutic approaches.

cancer biology↗

bioRxiv2024

A selective S-acyltransferase inhibitor suppresses tumor growth

S-acyltransferases play integral roles in essential physiological processes including regulation of oncogenic signaling pathways. While discovered over 40 years ago the field still lacks specific S-acylation inhibitors thus the potential benefit of pharmacologically targeting S-acyltransferases for human disease is still unknown. Here we report the identification of an orally bioavailable acyltransferase inhibitor SD-066-4 that inhibits the acyltransferase ZDHHC20. We identified a specific alanine residue that accommodates the methyl group of SD-066-4, thus providing isoform selectivity. SD-066-4 stably reduces EGFR S-acylation in Kras mutant cells and blocks the growth of Kras mutant lung tumors extending overall survival. We find that lung cancer patients harboring deletions in ZDHHC20 or ZDHHC14 concurrent with Kras alterations have a significant survival benefit, underscoring the translational importance of these enzymes.

cancer biology↗

bioRxiv2022

Small-molecule inhibitors targeting prokaryotic ClpQ protease in Plasmodium display anti-malarial efficacies against blood and liver stages

The ATP-dependent ClpQY system is a prokaryotic proteasome-like machinery in the mitochondrion of malaria parasite, Plasmodium. This protease system is identified as a validated target for malaria intervention. Here we have identified drug-like small chemical compounds, pyrimidotriazine derivatives, as specific inhibitors of P. falciparum ClpQ (PfClpQ) having effective parasiticidal efficacies on asexual and liver stages. Screening of the Malaria Box compound library, using a robust in vitro activity assay, identified a hit compound targeting the PfClpQ protease with IC50 at ~750nM. Further, Structure-Activity Relationship (SAR) analysis, using a small library of derivatives of the hit compound, identified three potential lead compounds, ICGEB-L1, ICGEB-L2 and ICGEB-L3, which inhibited enzyme activity with IC50 in 100-200nM ranges. The three lead compounds effectively inhibited in vitro asexual stage parasite growth in similar concentration ranges with ~100-fold selectivity over mammalian cell line; in addition, these compounds effectively inhibited in vitro growth and maturation of hepatocytic stage parasites with EC50 in low nano-molar ranges. These compounds were found to effectively block the development of trophozoite stages to schizont stage, concurrently arresting development and segregation of parasite mitochondria, in asexual as well as hepatocytic stages of the parasite. These morphological and developmental effects of the drugs on parasites mimic the data from genetic ablation of PfClpQ. Importantly, all three compounds showed significant in vivo anti-parasitic efficacies on blood stages of P. berghei mouse malaria model. Overall these results suggest that these PfClpQ targeting compounds are promising candidates to develop new anti-malarials.

microbiology↗

bioRxiv2022

Dual role of an essential HtrA2/Omi protease in the human malaria parasite: maintenance of mitochondrial homeostasis and induction of apoptosis like cell death under cellular stress

HtrA family of serine protease is known to play role in mitochondrial homeostasis as well as in the programmed cell death. Mitochondrial homeostasis and metabolism are crucial for survival and propagation of malaria parasite within the host. Here we have functionally characterized a Plasmodium falciparum HtrA2 (PfHtrA2) protein, which harbours trypsin like protease activity that can be inhibited by its specific inhibitor, ucf-101. Transgenic parasite line was generated, using HA-glmS C-terminal tagging approach, for localization as well as for inducible knockdown of PfHtrA2. The PfHtrA2 was localized in the parasite mitochondrion during asexual life cycle. Genetic ablation of PfHtrA2 caused significant parasite growth inhibition, decreased replication of mtDNA, increased mitochondrial ROS production, caused mitochondrial fission/fragmentation, and hindered parasite development. However, ucf-101 treatment had no effect on the parasite growth, suggesting non-protease/chaperone role of PfHtrA2 in the parasite. Under cellular stress conditions, inhibition of PfHtrA2 by ucf-101 reduced activation of the caspase like protease as well as parasite cell death, suggesting involvement of protease activity of PfHtrA2 in apoptosis like cell death in the parasite. Under these cellular stress conditions, the PfHtrA2 gets processed but remains localized in the mitochondrion, suggesting that it acts within the mitochondrion by cleaving intra-mitochondrial substrate(s). This was further supported by trans-expression of PfHtrA2 protease domain in the parasite cytosol, which was unable to induce any cell death in the parasite. Overall, we show specific role of PfHtrA2 in maintaining mitochondrial homeostasis as well as in regulating the stress induced cell death.

cell biology↗

bioRxiv2021

A Plasmodium falciparum lysophospholipase regulates fatty acid acquisition for membrane biogenesis to enable schizogonic asexual division

Phospholipid metabolism is crucial for membrane biogenesis and homeostasis during the intracellular life cycle of Plasmodium falciparum. To generate large amounts of phospholipids required during blood stages, the parasite massively scavenge, recycle and reassemble host lipids. P. falciparum possesses an unusual large number of lysophospholipases. However, their functional roles and importance remain to be elucidated. Here, we functionally characterized one of P. falciparum lysophospholipase (PfLPL3) (Gene ID PF3D7_1476800), to reveal its critical role in parasite propagation during asexual blood stages. We generated a transgenic parasite line using GFP-glmS C-terminal tagging approach, for localization as well as inducible knockdown of PfLPL3. PfLPL3 displayed a dynamic localization throughout asexual stages, mainly localizing in the host parasite interface: parasitophorous vacuole space and expanding into the tubulovesicular network within the host cell. Inducible knock-down of PfLPL3 hindered normal intraerythrocytic cycle, specifically causing disruption in parasite development from trophozoites to schizont, as well as reduction in number of merozoites progenies. Thus, down-regulation of PfLPL3 significantly inhibited parasite growth suggesting its critical role for proper parasite propagation during blood stages. Detailed lipidomic analyses showed that PfLPL3 generates fatty-acids for the synthesis of neutral lipids DAG and TAG, whilst controlling the timely synthesis of phospholipids that are crucial for membrane biogenesis required for merozoite development during asexual cycle. Setting up an in vitro activity based screening of Malaria Box allowed identification of specific inhibitors of PfLPL3 having potent parasitical efficacies. These compounds are pertinent both as anti-malarial drug candidates and chemical tools specifically targeting membrane biogenesis during asexual blood stages.

microbiology↗

bioRxiv2019

A lysophospholipase plays role in generation of neutral-lipids required for hemozoin formation in malaria parasite

Phospholipid metabolism is crucial for membrane dynamics in malaria parasites during entire cycle in the host cell. Plasmodium falciparum harbours several members of phospholipase family, which play key role in phospholipid metabolism. Here we have functionally characterized a parasite lysophospholipase (PfLPL1) with a view to understand its role in lipid homeostasis. We used a regulated fluorescence affinity tagging, which allowed endogenous localization and transient knock-down of the protein. PffLPL1localizes to dynamic vesicular structures that traffic from parasite periphery, through the cytosol to get associated as a multi-vesicular neutral lipid rich body next to the food-vacuole during blood stages. Down-regulation of the PfLPL1 disrupted parasite lipid-homeostasis leading to significant reduction of neutral lipids in lipid-bodies. This hindered conversion of heme to hemozoin, leading to food-vacuole abnormalities, which in turn disrupted parasite development cycle and significantly inhibited parasite growth. Detailed lipidomic analyses of inducible knock-down parasites confirmed role of PfLPL1 in generation of neutral lipid through recycling of phospholipids. Our study thus suggests a specific role of PfLPL1 to generate neutral lipids in the parasite, which are essential for parasite survival.\n\nImportancePresent study was undertaken with a view to understand the functional role of a unique lipase (lysophopholipase, PfLPL1) of the human malaria parasite. We utilized genetic approaches for GFP tagging as well as to knock-down the target protein in the parasite. Our studies showed that PfLPL1 associates closely with the lysosome like organelle in the parasite, the food-vacuole. During the blood stage parasite cycle, the food-vacuole is involved in degradation of host haemoglobin and conversion of heme to hemozoin. Genetic knock-down approaches and detailed lipidomic studies confirmed that PfLPL1 protein plays key role in generation of neutral lipid stores in the parasite; neutral lipids are essentially required for hemozoin formation in the parasite, a vital function of the food-vacuole. Overall, this study identified specific role of PfLPL1 in the parasite which is essential for parasite survival.

microbiology↗