Plasmodium knowlesi skeleton-Binding protein 1 localizes to the 'sinton and mulligan stipplings' in the cytoplasm of monkey and human erythrocytes

Abstract

The malaria parasite, Plasmodium, exports protein products to the infected erythrocyte t introduce modifications necessary for the establishment of nutrient acquisition and surfac display of host interaction ligands. Erythrocyte remodeling impacts parasite virulence and diseas pathology and is well documented for the human malaria parasite Plasmodium falciparum but has been less described for other Plasmodium species. For P. falciparum, th exported protein skeleton-binding protein 1 (PfSBP1) is involved in the trafficking of erythrocyt surface ligands and localized to membranous structures within the infected erythrocyte termed Maurer's clefts. In this study, we analyzed SBP1 orthologs across the Plasmodiu genus by BLAST analysis and conserved gene synteny, which were also recently describe by de Niz et al. (2016). To evaluate the localization of an SBP1 ortholog, we utilized the zoonoti malaria parasite, Plasmodium knowlesi. Immunofluorescence assay of transgenic P knowlesi parasites expressing epitope-Tagged recombinant PkSBP1 revealed a punctat staining pattern reminiscent of Maurer's clefts, following infection of either monkey or huma erythrocytes. The recombinant PkSBP1-positive puncta co-localized with Giemsa-staine structures, known as 'Sinton and Mulligan' stipplings. Immunoelectron microscopy als showed that recombinant PkSBP1 localizes within or on the membranous structures akin t the Maurer's clefts. The recombinant PkSBP1 expressed in P. falciparum-infected erythrocyte co-localized with PfSBP1 at the Maurer's clefts, indicating an analogous trafficking pattern A member of the P. knowlesi 2TM protein family was also expressed and localized t membranous structures in infected monkey erythrocytes. These results suggest that the traffickin machinery and induced erythrocyte cellular structures of P. knowlesi are similar followin infection of both monkey and human erythrocytes, and are conserved with P. falciparum.