Deciphering the function of the protein phosphatase 1 signaling network in egress of Plasmodium spp.

Plasmodium spp., the causative agents of malaria, are obligate intracellular parasites for most of their life cycle. To facilitate proliferation and transmission, parasites must egress from their host cells – an active and highly regulated process that is essential at several stages of the parasite’s life cycle. In-depth understanding of egress of asexual parasite stages from erythrocytes during the clinical stage of the disease will provide new opportunities for target-based drug discovery, which is urgently needed to overcome extensive drug resistance. Protein kinase G (PKG) and calcium-dependent signalling pathways are well-known regulators of parasite egress from erythrocytes. Factors initiating this process, however, remain to be determined. Recently, protein phosphatase 1 (PP1), a major serine/threonine phosphatase in model organisms, was shown to be essential for egress of asexual blood stages in P. falciparum, the most virulent malaria parasite species. In Plasmodium, PP1 controls both the PKG signaling pathway and, intriguingly, the phosphorylation state of the E3 protein-ubiquitin ligase HECT1, which is thought to have a critical function in egress. Therefore, PP1 activity links the ubiquitination pathway to PKG signaling at an essential point in the Plasmodium life cycle. The hypothesis is that PP1 is a key hub regulating and integrating multiple signaling pathways to elicit egress of asexual blood stage merozoites from erythrocytes. Firstly, Thommen will identify proteins interacting with putative egress-related PP1 signaling network members (ePPMs) using a proximity labeling strategy (aim 1). Secondly, he will use a forward genetics screening approach to identify proteins functionally interacting with the selected ePPMs (aim 2). Finally, he will characterize the function of priority candi-date genes in egress using state-of-the-art reverse genetic methods (aim 3).

Results: The presented approaches will identify new regulatory factors and effector proteins, such as kinases, receptors or transcription factors, of the PP1 signaling network. The expected results will shed light on the regulatory mechanisms underlying parasite egress from the erythrocyte host cell.

Impact: Elucidating the regulation of this key process of the Plasmodium blood-stage intraerythrocytic developmental cycle holds the potential to reveal insights relevant for developing new potent antimalarial treatments. Moreover, employing a forward genetic screen for probing Plasmodium signaling pathways is novel and will pave the way for future studies in the field.

Project details

Basic Science

Aug 2024 — Jul 2026

$147,355

United States