The Plasmodium palmitoyl-S-acyl-transferase DHHC2 is essential for ookinete morphogenesis and malaria transmission

Abstract

The post-translational addition of C-16 long chain fatty acids to protein cysteine residues is catalysed by palmitoyl-S-acyl-transferases (PAT) and affects the affinity of a modified protein for membranes and therefore its subcellular localisation. In apicomplexan parasites this reversible protein modification regulates numerous biological processes and specifically affects cell motility, and invasion of host cells by Plasmodium falciparum merozoites and Toxoplasma gondii tachyzoites. Using inhibitor studies we show here that palmitoylation is key to transformation of zygotes into ookinetes during initial mosquito infection with P. berghei. We identify DHHC2 as a unique PAT mediating ookinete formation and morphogenesis. Essential for life cycle progression in asexual blood stage parasites and thus refractory to gene deletion analyses, we used promoter swap (ps) methodology to maintain dhhc2 expression in asexual blood stages but down regulate expression in sexual stage parasites and during post-fertilization development of the zygote. The ps mutant showed normal gamete formation, fertilisation and DNA replication to tetraploid cells, but was characterised by a complete block in post-fertilisation development and ookinete formation. Our report highlights the crucial nature of the DHHC2 palmitoyl-S-acyltransferase for transmission of the malaria parasite to the mosquito vector through its essential role for ookinete morphogenesis.

Maternally supplied S-acyl-transferase is required for crystalloid organelle formation and transmission of the malaria parasite

“…having a likely essential role in blood stage parasite development (18). In the present work, we provide conclusive genetic evidence of the essential role of the stage-specific S-acyl-transferase DHHC10 for mosquito infection by P. berghei.…”

“…The targets of protein palmitoylation in the early mosquito stages of the malaria parasite remain to be identified, although inhibition of palmitoylation and deletion of P. berghei dhhc2 are known to severely affect zygote elongation (18). The published rodent P. berghei (36,37) and avian Plasmodium gallinaceum (38) malaria zygote and ookinete proteomes comprehend 277 out of 1,368 (20%) P. falciparum orthologs found to be palmitoylated in P. falciparum schizonts.…”

“…Palmitoylation is crucial for P. falciparum schizogony and P. berghei ookinete formation (15,18). Here we investigated the role of a maternally provided, translationally repressed S-acyl-transferase for developmental progression in the mosquito vector.…”

The development of malaria parasites in the mosquito midgut

“…berghei retorts, which are N‐myristoylated, phosphorylated and membrane‐bound (Poulin et al ., 2013). Indeed, lipidation modifications appear to be important in general during zygote‐to‐ookinete conversion, and a palmitoyl‐S‐acyl‐transferase DHHC2 is crucial for this process (Santos et al ., 2015). Further, the sexual stage‐specific actin isoform actin 2, which was originally reported to play a role in male gametogenesis of P .…”

Dynamic proteinS-palmitoylation mediates parasite life cycle progression and diverse mechanisms of virulence

“…The study of S-palmitoylation in apicomplexan parasites is more advanced than for other infectious microorganisms, as numerous palmitoylated proteins have been characterized that are important for life cycle progression, cell viability, gametocytogenesis, trafficking, gliding motility, host-cell invasion, and egress from host cells (Beck et al , 2013, Frenal et al , 2013, Santos et al , 2015, Hopp et al , 2016, Santos et al , 2016, Tay et al , 2016). Importantly, palmitoyl proteomes have been generated using the complementary ABE and metabolic labelling strategies, in combination with stable isotope labelling with amino acids in cell culture (SILAC) for highly accurate quantification by mass spectrometry.…”