E-Poster with pre-recorded video presentation Lorne Infection and Immunity 2021

Investigating the role of Plasmodium falciparum exported proteins that bind the new permeability pathway complex protein RhopH2 (#238)

Thorey Jonsdottir 1 2 , Natalie Counihan 3 , Benjamin Dickerman 1 , Smitha Sudhakar 3 , Joyanta Modak 3 , Betty Kouskousis 1 , Mikha Gabriela 1 3 , Paul Sanders 1 , Hayley Bullen 1 , Tania de Koning-Ward 3 , Brendan Crabb 1 2 4 , Paul Gilson 1
  1. Burnet Institute, Melbourne, VIC, Australia
  2. University of Melbourne, Melbourne
  3. Deakin University, Waurn Ponds, Geelong
  4. Monash University, Melbourne

Every day over 1000 people die of malaria, most of who are children under the age of five. The emergence of drug resistance in Plasmodium falciparum, the causative agent of severe malaria, is alarming and we need new antimalarial drugs. A crucial part of this process is to understand the basic biology of the parasite and elucidate targetable proteins/pathways. The ability of P. falciparum to survive within the erythrocyte is dependent on the new permeability pathways (NPPs) which provide import of vital nutrients, making them an attractive drug target. The NPPs have been affiliated with the activity of three parasite proteins: RhopH1, RhopH2 and RhopH3. We previously showed that RhopH2 was associated with 30 additional proteins predicted to be exported into the erythrocyte. We therefore hypothesised that some of these exported proteins might be important for NPP function, as protein export is a prerequisite for NPP activity. Here we tagged 13 of the 30 proteins with HAglmS to conditionally knockdown individual proteins and study their role in NPP activity. An exported nanoluciferase reporter was introduced into each parasite line to observe changes in sorbitol lysis (NPP uptake) during protein knockdown. We show that none of the 13 proteins are individually required for NPP function. Reciprocal immunoprecipitation assays further showed that only six proteins were able to co-precipitate RhopH2. Majority of these six proteins are known cytoskeletal proteins and therefore likely interacting indirectly with RhopH2 due to cytoskeletal binding and not due to direct NPP function. Although the 13 proteins studied do not appear to be essential for the NPPs, this study greatly expands our current knowledge of exported proteins. We reveal for the first time the location of five new proteins, hypothesised to be exported, as well as providing a clearer picture of protein-protein interaction within the P. falciparum infected erythrocyte.