Cytoadherence and consequential migration are crucial for pathogens to establish colonization in the host. In contrast to the nonadherent isolate of Trichomonas vaginalis, the adherent one expresses more actin-related machinery proteins with more active flagellate-amoeboid morphogenesis, amoeba migration, and cytoadherence, activities that were abrogated by an actin assembly blocker. By immunoprecipitation coupled with label-free quantitative proteomics, an F-actin capping protein (TvFACPα) was

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... identified from the actin-centric interactome, with an atypically greater binding preference to G-actin than F-actin. TvFACPα partially colocalized with F-actin at the parasite pseudopodia protrusion and formed the protein complexes with α-actin through its c-terminal domain. Meanwhile, TvFACPα overexpression suppresses F-actin polymerization, amoeboid morphogenesis, and cytoadherence in this parasite. Ser2 phosphorylation of TvFACPα enriched in the amoeboid stage of adhered trophozoites was reduced by a CKII inhibitor. The site-directed mutagenesis and CKII inhibitor treatment revealed that Ser2 phosphorylation acts as a switching signal to alter TvFACPα actin-binding activity and consequent actin cytoskeleton behaviors. Through CKII signaling, TvFACPα also controls the conversion of adherent trophozoite from amoeboid migration to flagellate form with axonemal motility. Together, CKII-dependent Ser2 phosphorylation regulates TvFACPα binding actin to fine-tune cytoskeleton dynamics and drive crucial behaviors underlying host colonization of T. vaginalis.