Research Area B

Parasite genetics and adaptations

During coevolution with the invertebrate and vertebrate hosts Plasmodium parasites adopted a wide range of tailored variations of a typical eukaryotic cell inventory, ranging from unique proteins and expression regulation, to specialized organelles and remodelling of the infected host cell. A better molecular understanding of these adaptations can aid in interpretations of malaria-related pathology and expose novel Achilles’ heels for malaria therapy. A prominent example of how distinct adaptations can be exploited includes Plasmodium susceptibility to a range of antibiotics that inhibit the essential function of the non-photosynthetic plastid organelle, termed apicoplast. In this research area six projects study the composition, function, and regulation of key features, including organelles, membrane structures and protein complexes, in Plasmodium parasites and in their host cells.


projects

Project B1

Analysis of a novel family of organelle-directed RNA binding proteins in Plasmodium falciparum

 

CHRISTIAN SCHMITZ-LINNEWEBER (HUB) in partnership with Giel van Dooren (ANU)

 

The project combines RNA biochemistry and experimental genetics towards a systematic analysis of Plasmodium organellar RNA metabolism. By organelle enrichment combined with proteomics and genome-wide profiling of signature binding sites the study will focus on a novel family of apicomplexan organellar RNA binding proteins and their functions in ribosome biogenesis and mRNA turnover. 

Birte Steinhöfel

Project B1 - 2nd Cohort

RNA Processing and Turnover in Apicomplexan Organelles

 

CHRISTIAN SCHMITZ-LINNEWEBER (HUB) in partnership with Melanie Rug (ANU) and Alexander Maier (ANU)

 

Apicoplasts and mitochondria contain their own genetic information. Gene expression in these organelles is essential for parasite survival. Antibiotics targeting gene expression in the apicoplast and mitochondrion serve as potent antimalarials. Very little is known about the organellar gene expression machinery in Apicomplexans. We recently identified a family of RNA binding proteins named heptatricopeptide repeat proteins. Members of this family were demonstrated to reside in RNA granules in human mitochondria and play a role in rRNA and mRNA processing. Initial gene tagging and knock-out approaches demonstrated that these proteins reside in mitochondria and are essential for parasite survival. Their exact functions in mitochondrial RNA metabolism remains enigmatic. In general, RNA turnover and its regulation is hardly addressed in Apicomplexans, neither in organelles nor in the nucleo-cytoplasmic compartment. This project aims at filling this gap in our knowledge.

Zala Gluhic



Project B2

Characterisation of the virulence complex of the malaria parasite

 

MELANIE RUG (ANU) in partnership with Kai Matuschewski (HUB) and Alyssa Ingmundson (HUB)

 

Inside erythrocytes, Plasmodium refurbishes its host cell by inducing novel organelles, such as Maurer’s clefts, which are trafficking hubs for the export of virulence factors.In this project previously unrecognized proteins of the exported virulence complex will be analysed by state-of-the-art  imaging tools, including correlative light and electron microscopy, in the human and murine model pathogens. 

Project B2 - 2nd Cohort 

'New Permeability Pathway' Structure and Function in Plasmodium falciparum

 

MELANIE RUG (ANU) in partnership with Andreas Herrmann and Thomas Korte (HU) 



Project B3

Characterizing protein function at the parasite-host interface during both liver and blood infection stages.

 

ALYSSA INGMUNDSON (HUB) in partnership with Melanie Rug (ANU)

 

Host cell remodelling also occurs in Plasmodium-infected liver cells, and in the complementary project novel P. berghei proteins at the parasite-host interface that are shared between liver and blood stages will be studied by experimental genetic and biochemical techniques to characterize the molecular repertoire of parasite-induced host cell structures.

Julie-Anne Gabelich

Project B3 - 2nd Cohort 

Characterizing Plasmodium Protein Function at the Parasite-Host Interface During both Liver and Blood Infection Stages

 

ALYSSA INGMUNDSON (HUB) in partnership with Melanie Rug (ANU) and Alexander Maier (ANU) 

 

While protein export and host cell membrane remodeling are processes conserved across Plasmodium species, their influence on the ability of parasites to thrive in their hosts has been primarily studied in Plasmodium falciparum. While P. falciparum is the deadliest malaria species, it is evolutionarily distinct from the other human-infecting species, such as P. vivax and P. knowlesi. We have been studying P. berghei proteins that are conserved in most human- or rodent-infecting species, but absent from P. falciparum. These proteins are expressed in both the liver and blood stages of infection and are exported into the host red blood cell where they localize to membranes formed in the host cytoplasm and influence the ability of infected red blood cells to sequester in the microvasculature.

Florian Kirscht



Project B4 - 1st Cohort

Tubulin – A novel lead to antimalarial drug discovery

 

SIMONE REBER (HUB) in partnership with Kevin Saliba (ANU)

 

The highly dynamic microtubulecytoskeleton plays an essential  role in the structural integrity of malarial parasites. Consistent with its important role, microtubule-disruptive drugs have great potential as anti-malarial agents. The current therapeutic options

of microtubule-disruptive drugs, however, are limited by their high toxicity to mammalian cells. The aim of this PhD project is to characterize Plasmodium tubulin biochemically and biophysically in order to improve its druggability and to advance the potential of Plasmodium tubulin as anti-malarial.

Will Hirst

Project B4 - 2nd Cohort

Tubulin - A Novel Lead to Antimalarial Drug Discovery

 

SIMONE REBER (HUB) in partnership with Kevin Saliba (ANU)

 

The highly dynamic microtubulecytoskeleton plays an essential  role in the structural integrity of malarial parasites. Consistent with its important role, microtubule-disruptive drugs have great potential as anti-malarial agents. The current therapeutic options

of microtubule-disruptive drugs, however, are limited by their high toxicity to mammalian cells. The aim of this PhD project is to characterize Plasmodium tubulin biochemically and biophysically in order to improve its druggability and to advance the potential of Plasmodium tubulin as anti-malarial.

Dominik Fachet




Project B6 - 1st Cohort

Dissecting the distinct metabolic roles of the ferredoxin redox system

 

FRANK SEEBER (HUB) in partnership with and Kevin Saliba (ANU)

 

Ferredoxin (Fd) and its reductase (FNR) are an essential redox system in the apicoplast organelle in both T. gondii and Plasmodium sp. Fd is presumably an important electron donor for the apicoplast-resident synthesis pathways of fatty acids and isoprenoid precursors. However, the precise role of this redox system is ill-defined. In particular, how Fd is capable of selectively passing on electrons via protein-protein interactions to the three different enzymes (LipA, GcpE & LytB) involved in these essential pathways is unknown.

Stephanie Henkel

Project B6 - 2nd Cohort

Structural Elucidation of the Interaction of Apicoplast-Resident Ferredoxin with its Interacting Proteins

 

FRANK SEEBER (HUB) in partnership with Christina Spry (ANU) and Kevin Saliba (ANU)

 

Previously, methodology for a two-hybrid screen of genetically encoded cyclic peptides was established in E. coli with the aim of identifying molecules that specifically inhibit the binding of Fd to LipA. In this project, we want to screen camelid single chain antibodies (nanobodies) for antibody molecules promoting (or preventing) interactions. Previously, nanobodies binding to one or both partners of a complex have been crucial for stabilizing transient complex structures, eventually allowing their 3D-structures to be solved. Currently, no 3D-structure of the complex between PfFd and PfFNR exists. Moreover, a 3D-structure of the transient interaction between Fd and LipA (or LytB or GcpE) would allow us to understand how a small protein like Fd can make specific contacts with such diverse interacting proteins and it would help in the design of novel drugs binding to Fd.

Ojo-Ajogu Akuh

 



Project B7 - 2nd Cohort

Metabolic Characterisation and Chemotherapeutic Targeting of Persistent T. gondii and P. falciparum Parasites

 

MARTIN BLUME (Robert-Koch-Institute), Kai Matuschewski (Dept. of Biology, Humboldt University Berlin), Kevin Saliba (Department Research School of Biology, ANU, Canberra)

 

Phenotypic variation in protozoan parasites is an important strategy to evade the immune responses and antimicrobial treatments. The apicomplexans Toxoplasma gondii and Plasmodium falciparum employ this strategy through the formation of tissue cysts and dormant blood stages, respectively. These stages are marked by attenuated growth and drug resistance. The ability to persist facilitates transmission to the next host. In order to successfully target these evasive stages we need to understand how resistance to antimicrobials is achieved. To this end we aim to characterize the metabolism of dormant parasites by using untargeted metabolomics and test their susceptibility to novel inhibitors.

Thomas Andersen 


Project B8 - 2nd Cohort 

Exploring Species and Stage-Dependent Differences in the Pantothenate Requirement of Malaria Parasite

 

CHRISTINA SPRY, KEVIN SALIBA (ANU) in partnership with Alyssa Ingmundson (HUB) and Martin Blume (RKI)

 

Plasmodium sp. and Toxoplasma gondii contain a specialized organelle, termed apicoplast, which harbours several essential metabolic pathways, e.g. isoprenoid and fatty acid synthesis. The plant-type ferredoxin (Fd) redox system constitutes the only known electron transfer system in the apicoplast. We previously showed that Fd provides electrons to enzymes of the isoprenoid pathway and to lipoic acid synthetase (LipA) via protein interactions. The apicoplast is also a site for iron-sulfur cluster synthesis.  This process requires a reducing source, which likely is Fd. Our unpublished work show that Fd in T. gondii (TgFd) is an essential gene. However, its individual contributions to the distinct Fd-dependent pathways are unknown. Moreover, the reported association between polymorphisms in P. falciparum Fd and artemisinin resistance [1] warrants investigation of the underlying molecular mechanism.

 

TBA