After transmission from the human to the mosquito, the malaria parasite Plasmodium falciparum encounters a new environment to which it quickly needs to adapt. Among others, stage specific proteins must be synthesized, e.g. for host cell egress and sexual reproduction. Transcripts coding for some of these proteins are already synthesized in the human host, while translation is initiated only after transmission. We have identified the protein 7-Helix-1 as a crucial component in the process of translational re-initiation. 7-Helix-1 was shown to localize to stress granules where it interacts with known ribonucleoproteins and binds repressed mRNAs. In silico analyses demonstrated that 7-Helix-1 is homologous to the human stress regulator hLanCL2, which is involved in the mTORC-pathway. Although P. falciparum has lost most of the mTORC-components, we hypothesize that 7-Helix-1 regulates translation via an mTORC-like signaling cascade.

In order to decipher the potential link between 7-Helix-1, mTORC-related components and translation, we will characterize the downstream kinases of the mTORC-pathway, KIN, PI3K and S6K, which are present in P. falciparum. To investigate the role of the three kinases during translational regulation, knockout (KO) parasite lines are generated and characterized. Further, the KO studies will be complemented with chemical inhibition/activation studies using commercial inhibitors and activators.

RT-PCRs revealed transcript expression for all three kinases in mature and activated gametocytes. Chemical inhibition of KIN by dorsomorphin lead to impaired parasite growth and developmentally arrested schizonts. Further, dorsomorphin-treated parasites were shown to be impaired in stress-induced regulation of translation activity.

The mTORC pathway is one of the most important signaling cascades in mammalian cells integrating nutrient availability and regulating protein translation. In this project, we will investigate the potential role of mTORC-related kinases in translational regulation. Data gained in this project will help us understand how the parasite is able to specifically regulate protein synthesis depending on the environment.