Parasite Cell Biology

INFECTIOUS DISEASES / Parasitic Diseases

Research Interests

Functional biology of parasite proteases, developmental regulation of cell organelles, cellular stress and parasite cell-death, protein trafficking machinery, new anti-malarials

Description of Research

Functional Biology of Plasmodium falciparum proteases
Our group is working on several parasite proteases that may be involved in organelle biogenesis and parasite survival. One of these protease systems is the ClpQY system, an ATP dependent protease machinery, which is the prokaryotic counterpart of eukaryotic 20S proteasome. Detailed biochemical and functional characterization of the P. falciparum ClpQ protease (PfClpQ) showed that the protease machinery is essential for survival of the parasite; further, we have shown that the PfClpQY machinery plays essential role in development of functional mitochondria in the parasite. These studies validated the P. falciparum ClpQ protease as a drug target in the parasite.

Another protease machinery characterized by our group is a cyanobacterial ClpAP serine protease system in the parasite. Using the GFP targeting approach the ClpAP protease machinery was localized in the relict plastid in the parasite, the apicoplast. A chemical library screening strategy identified PfClpP specific inhibitor; using this inhibitor we showed that the ClpP protease play important role in development of parasite apicoplast and thus it is essential for survival of the parasite.

Cellular Stress and parasite Cell-death
Another research theme of the group is to understand the molecular and cellular events in the parasite after induction of cellular stresses. Detailed proteomic and cell biology studies showed that persistent ER stress induces unfolded protein response and cause structural abnormalities in endoplasmic reticulum. The ER stress response is subsequently transmitted to mitochondria and initiates a cascade of cellular events including: rise in cytosolic calcium levels, activation of VAD-FMK-binding proteases, dysregulation of mitochondrial development and suppression of protein translation machinery. This cascade of events ultimately leads to apoptosis like parasite cell death. Further, induction of organelle specific stress, by selective inhibition of mitochondrial metabolic pathways, is also shown to initiate a similar cascade of cellular events, which in turn causes parasite cell death with apoptosis like features.

Protein-trafficking machinery in the parasite
Using different genetic and GFP-targeting approaches the group is studying protein trafficking in the parasite. Previously, we studied the trafficking and processing of an important food vacuole protease, falcipain-2, a major hemoglobinase. A dynamin-like C-terminal Eps15 homology domain containing protein of P. falciparum (PfEHD) was characterized by our group recently; PfEHD plays a role in generation of endocytic vesicles at the parasite plasma membrane, that are subsequently targeted to the neutral lipid generation/storage site localized near the food vacuole. A P. falciparum adaptor protein of vesicular transport was also characterized, which is involved in trafficking of specific cargo proteins to apical secretory organelles in merozoite, which play important role during invasion.

Development of new anti-malarials
One of our major goals is to develop new anti-malarial compounds targeting selected parasite proteins. In this direction, we are collaborating with national and international research groups including University Health Network (Toronto, Canada), Institute of Cell Biology (Bern, Switzerland), Technical University of Munich (Germany), LifeCare Innovations (India) and National Chemistry Laboratory (India), which have expertise in synthetic chemistry, medicinal chemistry and parasitology. Several lead compounds are developed by our group using in silico and high-throughput screening followed by medicinal chemistry campaign, these compounds inhibit different drug targets: falcipain-2, ClpP, ClpQ and ODCase. Based upon these results, the group was awarded “Malaria Box Challenge Grant” by Medicine for Malaria Venture (MMV, Switzerland). Studies under this project identified lead anti-malarial compounds, which inhibit various parasite stages.

The Group has recently made ground-breaking advances in understanding and characterizing a novel Plasmodium falciparum merozoite glideosome complex, and proteasome shuttle/interacting proteins, which play key roles in the invasion of red blood cells and protein homeostasis respectively (Saini, E et al., PLOS Pathogens. 2021; Onchieku et al., 2021, Pathogens), thereby opening novel ways of potentially blocking parasite infection and development. The Group has also characterized essential lipid metabolism pathways in the parasite as novel drug targets (Asad et al., BMC Biol 2021; Sheokand et al., Biochem J 2021).

Recent Publications