Conserved and Lineage-specific Functions of Plasmodium Membrane Transport Proteins

KAI MATUSCHEWSKI (HUB) in partnership with Alexander Maier (ANU), Kiaran Kirk (ANU), and Giel van Dooren (ANU)

Plasmodium species are intracellular parasites that must scavenge a broad range of nutrients (including sugars, nucleosides, amino acids and vitamins) from their hosts to survive and replicate. They must also expel the waste products of their metabolism and maintain intracellular ion homeostasis. These essential processes are mediated by membrane transport proteins that facilitate the movement of molecules across biological membranes. Despite their importance, the functions of only a few membrane transporters have been characterized in these parasites.

In this project we will carry out a detailed functional profiling of membrane transport proteins (MTPs) encoded in the Plasmodium berghei genome and a cross-species comparison to orthologous gene in the human parasite Plasmodium falciparum [1] and a distant apicomplexan relative, Toxoplasma gondii. Employing advanced selection protocols in the murine malaria model parasite P. berghei [2] the Matuschewski group (HUB) has recently published a proof-of-concept study that entailed the comprehensive genetic profiling of orphan MTPs, and uncovered distinct vital roles for >50% of the target genes during the P. berghei life cycle [3]. Experimental genetics combined with biochemical profiling in P. falciparum in the Maier and Kirk groups (ANU) uncovered the physiological roles of a gametocyte-specific ABC transporter [4].

In this project, we aim to identify the function of membrane transport proteins in apicomplexan parasites, and elucidate their importance for parasite survival, virulence and life cycle progression. The student will build on a recent systematic bioinformatics re-analysis of Plasmodium and Toxoplasma MTPs performed at ANU. Representative MTPs will be analysed to determine their function and importance for parasite biology. The student will, for each MTP of interest, use a broad range of techniques, including endogenous gene tagging to determine protein localization, targeted gene deletion and regulated gene knockdown to determine the importance of the protein for parasite biology, and heterologous expression in Xenopus oocytes to elucidate substrate selectivity and functional characteristics of the MTP protein. MTPs representing channels, pumps, and porters will be selected for targeted gene deletion, regulated gene expression, and endogenous tagging to profile phenotypes and spatial-temporal expression in the entire P. berghei life cycle encompassing mosquito, liver and blood stages, in P. falciparum blood cultures, and in the lytic cycle of T. gondii. Cross-species complementation in all three parasites will reveal whether some MTPs are tailored to their specific host cell or largely interchangeable. In a future project, MTPs with broad and narrow parasite/host ranges will be characterized by biochemical assays and metabolic profiling. This work will identify and validate new targets for therapeutic intervention and uncover common and unique principles in parasite/host coevolution and metabolic flexibility of malarial and related parasites.

Interlinkages: Ian Cockburn (ANU), Edda Klipp (HUB), Frank Mockenhaupt (Charité), Simone Reber (HUB), Melanie Rug (ANU), Allen Rodrigo (ANU), Leif Erik Sander (Charité), Christian Schmitz-Linneweber (HUB).

References:

(1) Martin, R. et al. (2009) Mol. Microbiol. 74: 519-528

(2) Kenthirapalan, S. et al. (2012) Int. J. Parasitol. 42: 1185-1192

(3) Kenthirapalan, S. et al. (2016) Nat. Commun. 7: 10519

(4) Tran, P. et al. (2014) Nat. Commun. 5: 4773