Abstract
In 2009, apicortin was identified in silico as a characteristic protein of apicomplexans that also occurs in the placozoa, Trichoplax adhaerens. Since then, it has been found that apicortin also occurs in free-living cousins of apicomplexans (chromerids) and in flagellated fungi. It contains a partial p25-α domain and a doublecortin (DCX) domain, both of which have tubulin/microtubule binding properties. Apicortin has been studied experimentally in two very important apicomplexan pathogens, Toxoplasma gondii and Plasmodium falciparum. It is localized in the apical complex in both parasites. In T. gondii, apicortin plays a key role in shaping the structure of a special tubulin polymer, conoid. In both parasites, its absence or downregulation has been shown to impair pathogen–host interactions. Based on these facts, it has been suggested as a therapeutic target for treatment of malaria and toxoplasmosis.
Highlights
Research Centre for Natural Sciences, Institute of Enzymology, Magyar Tudósok Körútja 2, Abstract: In 2009, apicortin was identified in silico as a characteristic protein of apicomplexans that occurs in the placozoa, Trichoplax adhaerens
These results show that apicortin influences the organization, shape, and stability of the tubulin polymers, and connects other conoid components to the tubulin core (Table 1)
Apicortin was localized on the surface of the parasite in the subpellicular region of both the trophozoites and the schizonts, where apicortin was co-localized with merozoite surface protein 1 (MSP1) and myosin A tail interacting protein (MTIP)
Summary
Apicortin, when identified, was shown to occur in apicomplexan parasites and in the placozoan animal, Trichoplax adhaerens [1]. Later it has been found that apicortin occurs in chromerids, the recently discovered [3,4], free-living cousins of apicomplexans [5] This is not surprising, given the phylogenetic proximity and the structural similarity of these phyla. Animal draft genomes and transcriptomes contain sometimes nucleotide sequences, contigs and TSAs (transcriptome shot-gun assemblies), homologous to apicortin, but they have been shown to be contaminations from parasitizing apicomplexans, based on sequence similarities and GC ratios [11,12]. The protein that contains the p25alpha domain varies depending on the phylum; e.g., it is the so called “long-type” TPPP in animals (except T. adhaerens) [10,17], a fungal-type TPPP and apicortin in flagellated fungi [8], while the “short-type” TPPP and apicortin are found in apicomplexan species [10]. With the exceptions of two nonflagellated fungi and some apicomplexans, apicortin can be found only in species which are flagellated, at least in some life stage
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