Defining the rhoptry kinome in Plasmodium falciparum and its importance for invasion of red blood cells

Malaria remains a major global health issue, caused by the apicomplexan parasites of the genus Plasmodium, with Plasmodium falciparum being the most virulent and lethal species. Malaria symptoms primarily result from repetitive cycles of parasite invasion, replication and egress within human red blood cells (RBCs). Invasion by the infective merozoite forms is facilitated by the secretion of factors from apically localized secretory organelles. Among these, the largest, known as rhoptries, contain proteins essential during invasion and subsequent intracellular development. Despite their critical role, the regulatory mechanisms governing their functions remain poorly understood. For instance, phosphorylation has been observed in several of these essential rhoptry proteins. However, the implications of these modifications are unclear, as no kinase has yet been identified within the rhoptries. Therefore, I hypothesize that kinases localize to rhoptry organelles and play important roles in merozoite invasion and intraerythrocytic development. Preliminary data supports this hypothesis, by showing that FIKK5, a non-essential kinase previously thought to be exported into RBCs, localizes to the rhoptry bulbs. Based on this, I propose to identify essential rhoptry kinases in P. falciparum and investigate their regulatory impact on other rhoptry proteins, as well as in invasion and intraerythrocytic development, using state-of-the-art proteomic, genetic and cell biological approaches. To achieve this, I will: 1) define the rhoptry kinome in P. falciparum; 2) characterize the functions of rhoptry kinases during parasite development; and 3) assess the impact rhoptry kinase disruption on the protein environment within rhoptries. Ultimately, through this proposal I will generate the first comprehensive proteome of the rhoptries in P. falciparum, while identifying the first kinases involved in regulating key rhoptry factors critical for maintaining infection of RBCs.