Identification of signals and factors facilitating transport of STEVOR to the Maurer`s clefts of Plasmodium falciparum

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The human malarial parasite Plasmodium falciparum exports proteins beyond its own plasma membrane to distinct locations within its host erythrocyte, including the erythrocyte cytoplasm and surface, as well as to membranous structures of parasite origin termed Maurer's clefts. The trafficking signals and factors mediating this unique "extracellular" protein secretory pathway are largely uncharacterized. Previous work from our laboratory has suggested that transport of STEVOR, a resident trans-membrane protein of Maurer's clefts, is mediated by a multi-step signaling pathway composed of three signals: an N-terminal signal peptide, a recessed targeting signal contained within 55 amino acids, and a trans-membrane domain. These signals have to work in concert to allow proper trafficking of STEVOR to Maurer's clefts. The data were generated by investigating the sub-cellular localization of various STEVOR-GFP fusion proteins. Here, we propose to carry out a detailed mutational analysis of the 55 amino acids containing the targeting signal, and furthermore, identify components of the P. falciparum secretory pathway that interacts with this signal in trafficking of STEVOR to the Maurer's clefts. The proposed experimental design includes, apart from an alanine scan across the targeting signal, transfection technology to express GFP fusion chimeras, a yeast two-hybrid screen to identify factors interacting with the targeting signal, and the generation of antibodies to characterize these putative factors of the P. falciparum secretory pathway.