The novel conoidal methyltransferase PCKMT is responsible for the initiation of motility in concert with other conoidal proteins in Toxoplasma gondii (Exit WS)

Abstract text

Toxoplasma gondii is an obligate intracellular parasite critically depending on invasion and egress from infected cells to ensure survival. A crucial structure for these processes is the apical complex which is highly conserved in most apicomplexans. Within this structure, the conoid, constructed by tubulin fibers, and preconoidal rings are crucial for parasite motility, invasion, and egress. Recently, we identify two proteins that localise to the preconoidal rings in two independent splitCas9 phenotypic screens: CGP and PCKMT. These proteins appear to be responsible for the initiation of motility after egress signalling. While CGP is an important structural protein for the stability of the preconoidal rings and localisation of many proteins at this structure, PCKMT, a putative lysine methyltransferase, is critical for the recruitment of formin 1 (FRM1) to the conoid. To further identify interacting proteins of CGP, FRM1 and PCKMT, we performed proximity labeling experiments using TurboID tags. These assays revealed that FRM1, CGP and PCKMT possibly interact directly with each other. Other important components for motility such as GAC and AKMT were also identified, together with additional, hypothetical identified proteins. AKMT is a methyltransferase that has been shown to affect the recruitment of GAC to the apical complex and therefore is required for motility. We hypothesise that the coordinated activation of methylation by AKMT and PCKMT is not only required for the recruitment of GAC and FRM-1 to the conoid, but a prerequisite for the initiation and maintenance of gliding motility. We currently compare the methylation of candidate proteins in presence and absence of AKMT and PCKMT respectively in an attempt to decipher the regulation of motility by methylation.