A kinase involved in mitosis and repression of sexual commitment in malaria parasites

Over 600,000 deaths each year are caused by the human malaria parasite Plasmodium falciparum. P. falciparum parasitises throughout the body, with significant accumulations in the heart, spleen, and bone marrow. Most importantly for malaria pathology, P. falciparum adheres to cerebral microvasculature, which restricts blood flow to the brain, resulting in coma and death. Drug resistance against frontline antimalarials is currently spreading, highlighting the critical need to develop novel antimalarials for ongoing control of malaria. Despite the commonality of replication inhibitors as antivirals or cancer therapeutics, currently no antimalarials directly target P. falciparum mitosis or cell division. During the asexual blood-stage of the P. falciparum lifecycle, the parasite undergoes schizogony whereby an initially mononucleated cell undergoes asynchronous rounds of mitosis and nuclear division in a shared cytoplasm before a single cytokinesis event that produces 16-32 daughter parasites. In addition to asexual replication, a proportion of asexual parasites commit to sexual differentiation, which is required for transmission from humans to mosquitoes. Despite their importance neither the proteins that promote asexual replication over sexual differentiation, nor those that control P. falciparum mitosis are currently unknown. This proposal investigates the P. falciparum homologue of Tousled-like kinase (TLK), which our preliminary data shows to be a key regulator of P. falciparum mitosis and suppression of sexual differentiation. Knockdown of TLK prior to mitosis prevents DNA segregation and results in the formation of aberrant mitotic spindles. If TLK is knocked down soon after reinvasion, however, it promotes a non-canonical same-cycle commitment to sexual differentiation. Same-cycle commitment had only previously been observed for upregulation of ap2-g, the master regulator transcription factor of sexual commitment. Using ultrastructure-expansion microscopy, this proposal aims to determine how TLK coordinates DNA segregation and mitotic spindle formation. Further, this proposal aims to define how TLK represses commitment to sexual differentiation using nucleosome profiling. Overall, this project will result in an in-depth analysis of the mechanisms that control P. falciparum mitosis and sexual differentiation, two therapeutically attractive but poorly understood processes.

Basic Science

Jan 2023 — Dec 2024

$140,558

United States