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SUMMARY
Our research focuses on understanding of the molecular signal and machinery involved in egress Plasmodium falciparum merozoites from host erythrocytes, involving multidisciplinary approach such as live cell imaging, molecular biology, cell biology and protein chemistry. P. falciparum causes the most virulent form of malaria in humans leading to tremendous morbidity and mortality. All the clinical symptoms of malaria are attributed to the blood stage of the parasite life cycle. To complete its life cycle in blood stage, P. falciparum merozoites invade erythrocytes, replicate, and then exit by a process known as egress. The egress of P. falciparum merozoites from the host erythrocytes is an essential yet poorly understood process. Live video microscopy has played a special role in studies on egress and invasion. Real-time light microscopic visualization of in vitro blood-stage egress in live parasites has been performed in the simian parasite Plasmodium knowlesi and in P. falciparum. In both cases it was observed that egress is a rapid event following by a quick degradation of parasitophorus and host cell plasma membrane. A cascade of proteolytic events plays a major role in degradation of membranes leading to egress of merozoites. However, the signals that regulate the temporal activation and/or secretion of proteases upon maturation of merozoites in intra-erythrocytic schizonts remain unclear. We have demonstrated for the first time a role of intracellular Ca2+ in regulation of egress of P. falciparummerozoites from schizonts. A sharp rise in intracellular Ca2+ just before egress, observed by time-lapse video microscopy, suggested a role for intracellular Ca2+ in this process. Chelation of intracellular free Ca2+ with chelators such as BAPTA-AM or inhibition of Ca2+ release with phospholipase C (PLC) inhibitors blocks merozoite egress. Interestingly, chelation of intracellular Ca2+ in schizonts was found to block the discharge of a key protease PfSUB1 (subtilisin like protease1) from apical organelle exonemes of P. falciparum merozoites to parasitophorous vacuole (PV). This leads to inhibition of processing of PfSERA5 (serine repeat antigen5); block in parasitophorous vacuolar membrane (PVM) rupture and merozoite egress. A complete understanding of the steps regulating egress of P. falciparummerozoites may provide novel targets for development of drugs that block egress and limit parasite growth. We are now studying the role of perforin like proteins in release of egress of P. falciparummerozoites. |
FELLOWSHIPS AND AWARDS
• Innovative Young Biotechnologist Award 2013, Dept. of Biotechnology, New Delhi • INSA International Travel Award to attend World Congress on Drug Discovery and Therapy: Boston (2013) • DST International Travel Award to attend World Congress on Drug Discovery and Therapy, Boston, USA (2013) • Gates Foundation Travel Award to attend Gordon Research Conference on Malaria, Lucca, Italy (2013) • International Travel Award to attend the Gordon Research Conference on Malaria, Oxford, London (2009) • Innovative Young Biotechnology Fellowship, Dept. of Biotechnology, Govt. of India (2009-13) • Best paper presentation, International Conference on Radiation Damage and its Modification, India (2002) • Humboldt-Kolleg Travel Award to attend a symposium on Genetics and Human Health, Manipal, India (2001) GRANTS • 8/13 – 8/16 [INR 1,00,00,000] Principal Investigator: Identification of molecular signals involved in egress of Plasmodium falciparum merozoites from host erythrocytes. Funding Agency: Department of Biotechnology, India. • 9/13 – 9/16 [22,00,000] Principal Investigator: Molecular characterization of Perforin Like Protein 1 involved in egress of Plasmodium falciparum merozoites. Funding Agency: Department of Science &Technology, India. • 9/13-12/13 [INR 3,00,000] Principal Investigator: A multicolor flowcytometric approach to enumerate endothelial microparticles: Relevance for the evaluation of endothelial dysfunction in cerebral malaria. Funding Agency: BD Biosciences research grant. • 8/10 – 8/13 [INR 56,00,000] Principal Investigator: Role of calcium signaling in egress of Plasmodium falciparum merozoites from host erythrocytes. Funding Agency: Department of Biotechnology, New Delhi • 1/12 – 8/14 [INR 29,00,000] Co-Investigator: Molecular machinery involved in apical organelle discharge in Plasmodium falciparum merozoites during host cell invasion. Funding Agency: Department of Science &Technology, India. Amount: • 9/11 – 8/16 [INR 11,43,00,000] Co-Investigator: Understanding critical events in biology of blood stage of malaria parasites, Program Support Grant to Malaria Group, ICGEB. Funding Agency: Department of Biotechnology, India. STUDENT PROJECT/ THESIS SUPERVISION 1. Signaling in egress of Plasmodium falciparum merozoites from host erythrocytes Swati Garg, Project work, IYBA, Department of Biotechnology (completed) 2. Second Messengers of Molecular Signaling involved in egress of Plasmodium falciparum merozoites from host erythrocytes Shalini Agarawal, New Delhi. IYBA, Department of Biotechnology (ongoing) 3. Targeting the signaling machinery modulating secretion of invasins: A Novel approach for combating Malaria. Thesis on going (Poonam Dangi, Shiv Nadar University) 4. In silico Screening, Synthesis and Validation of small molecules against Perforin Like protein 1 an essential player in Plasmodium falciparum merozoites egress. Thesis ongoing (Vijeta sharma, Shiv Nadar University) |