Research Groups
Mammalian Biology: Malaria
Research Interests and Description
Staff Research Scientist: Asif Mohmmed, PhD
Group Leader: Virander Chauhan
Research Interests
Characterization of novel drug targets for Plasmodium falciparum. Functional characterization of parasite proteases. Antigen discovery. Protein trafficking machinery in the malaria parasite.
Description of Research
Functional characterization of Plasmodium falciparum proteases as novel drug targets
We have been working on ATP dependent protease machineries in the parasite as novel drug targets, and have identified the P. falciparum ClpQY protease system as a potential drug target machinery in the parasite. The ClpQY system is the prokaryotic counterpart of eukaryotic 20S proteasome that plays an important role in cell cycle regulation. We have carried out detailed biochemical and biological characterization of the P. falciparum ClpQ protease (PfClpQ) that harbors threonine protease specific activity. Detailed genetic studies using transgenic parasite lines have confirmed that the protease machinery is essential for survival of the parasite. We have developed a structure model of the ClpQY complex and have identified the interface residues between PfClpQ protease and PfClpY ATPase subunits; we also carried out a detailed characterization of their interaction. These studies may form the basis to design strategies to target this protease machinery to develop new anti-malarials.
We have identified and characterized cyanobacterial ClpP serine protease machinery in the parasite. The PfClpP was localized in the apicoplast using a GFP-targeting approach, immunoelectron microscopy and immunofluorescence assays. A set of cell permeable b-lactones, which specifically bind with the active site of prokaryotic ClpP, were screened using an in vitro protease assay of PfClpP. A PfClpP-specific protease inhibitor was identified in the screen, labelled as U1-lactone. In vitro growth of the asexual stage parasites was significantly inhibited by U1-lactone treatment. The U1-treated parasites showed developmental arrest at the late-schizont stage. We further show that the U1-lactone treatment resulted in formation of abnormal apicoplasts which were not able to grow and segregate in the parasite progeny; these effects were also evident by blockage in the replication of the apicoplast genome. Overall, the PfClpP protease has confirmed localization in the apicoplast and it plays animportant role in the development of functional apicoplasts. We are now trying to design more potent inhibitors for PfClpP that could be developed as new anti-malarials.
Identification and characterization of Merozoite Surface/Apical Proteins: novel vaccine target antigens
This project is focused on novel merozoite surface/apical organelle proteins that might be involved in merozoite attachment and its invasion in RBC. We screened the P. falciparum proteome database and selected some of the hypothetical proteins that grouped in transcriptome analysis with other P. falciparum antigens, which have previously been associated with the process of merozoite invasion, to study further. We carried out localization of these proteins in the parasite by a GFP targeting approach. A novel asparagine rich merozoite protein was identifed that localizes in the apical ends of the secretory organelle rhoptries in the merozoites, and was named P. falciparum, apical, asparagines-rich protein (PfAARP). In addition, we have also identified and characterized a novel merozoite surface protein in P. falciparum (PfDBLMSP) that harbors a central Duffy binding-like (DBL) domain and a secreted polymorphic antigen associated with a merozoites (SPAM) domain. Detailed studies suggest that these proteins play an important role in RBC binding during invasion of the merozoites into the host RBCs. These results support PfAARP and PfDBLMSP as novel vaccine/drug target candidates.
Recent Publications
Rizzi, L., Sundararaman, S., Cendic, K., Vaiana, N., Korde, R., Sinha, D., Mohmmed, A., Malhotra, P., Romeo, S. 2011. Design and synthesis of protein-protein interaction mimics as Plasmodium falciparum cysteine protease, falcipain-2 inhibitors. Eur J Med Chem 46, 2083‑2090 PubMed link
Mazumdar S., Mukherjee P., Yazdani S.S., Jain S.K., Mohmmed A., Chauhan V.S. 2010. A Plasmodium falciparum merozoite surface protein-1 (MSP-1) - merozoite surface protein-3 (MSP-3) chimeric protein: immunogenicity using human compatible adjuvants and induction of protective immune response. Infect Immun 78, 872-83 PubMed link
Ranjan, R. Chugh, M., Kumar, S., Singh, S., Kanodia, S., Hossain, M., Korde, R., Grover, A., Dhawan, S., Chauhan, V., Reddy, V., Mohmmed, A., Malhotra, P. 2010. Proteome Analysis Reveals a Large Merozoite Surface Protein-1 Associated Complex on the Plasmodium falciparum Merozoite Surface. J Proteome Res 10, 680-691 PubMed link
Rathore, S., Sinha, D., Asad, M., Böttcher, T., Afreen, F., Chauhan, V.S., Gupta, D., Sieber, S., Mohmmed, A. 2010. A cyanobacterial serine protease of Plasmodium falciparum is targeted to the apicoplast and plays important role in its growth and development. Mol Microbiol 77, 873–890 PubMed link
Srivastava A., Singh S., Dhawan S., Mahmood Alam M., Mohmmed A., Chitnis C.E. 2010. Localization of apical sushi protein in Plasmodium falciparum merozoites. Mol Biochem Parasitol 174,66-9 PubMed link
