Analysis of recombinant merozoite surface protein-1 of Plasmodium falciparum expressed in mammalian cells

Synthetic chimeric DNA constructs with a reduced A + T content coding for f ull-length merozoite surface protein-1 of Plasmodium falciparum (MSP1) and three fragments thereof were expressed in HeLa cells. To target the recombi nant proteins to the surface of the host cell the DNA sequences coding for the N-terminal signal sequence and for the putative C-terminal recognition/ attachment signal for the glycosyl-phosphatidyl-inositol (GPI)-anchor of MS P1 were replaced by the respective DNA sequences of the human decay-acceler ating-factor (DAF). The full-length recombinant protein, hu-MSP1-DAF, was s tably expressed and recognised by monoclonal antibodies that bind to the N- terminus or the C-terminus of the native protein, respectively. Its apparen t molecular mass is higher as compared to the native protein and it is post -translationally modified by attachment of N-glycans whereas native MSP1 is not glycosylated. Immunofluorescence images of intact cells show a clear s urface staining. After permeabilization hu-MSP1-DAF can be detected in the cytosol as well. As judged by protease treatment of intact cells 25% of rec ombinant MSP1 is located on the surface. This fraction of hu-MSPI-DAF can b e cleaved off the cell membrane by phosphatidylinositol-specific phospholip ase C indicating that the protein is indeed bound to the cell membrane via a GPI-anchor. Human erythrocytes do not adhere to the surface of mammalian cells expressing either of the constructs made in this study. (C) 1999 Publ ished by Elsevier Science Ireland Ltd. All rights reserved.