PEXEL-independent trafficking of Plasmodium falciparum SURFIN4.2 to the parasite-infected red blood cell and Maurer's clefts

SURFIN4.2 is a parasite-infected red blood cell (iRBC) surface associated protein of Plasmodium falciparum. To analyze the region responsible for the intracellular trafficking of SURFIN4.2 to the iRBC and Maurer's clefts, a panel of transgenic parasite lines expressing recombinant SURFIN4.2 fused with green fluorescent protein was generated and evaluated for their localization. We found that the cytoplasmic region containing a tryptophan rich (WR) domain is not necessary for trafficking, whereas the transmembrane (TM) region was. Two PEXEL-like sequences were shown not to be responsible for the trafficking of SURFIN4.2, demonstrating that the protein is trafficked in a PEXEL-independent manner. N-terminal replacement, deletion of the cysteine-rich domain or the variable region also did not prevent the protein from localizing at the iRBC or Maurer's clefts. A recombinant SURFIN4.2 protein possessing 50 amino acids upstream of the TM region, TM region itself and a part of the cytoplasmic region was shown to be trafficked into the iRBC and Maurer's clefts, suggesting that there are no essential trafficking motifs in the SURFIN4.2 extracellular region. A mini-SURFIN4.2 protein containing WR domain was shown by Western blotting to be more abundantly detected in a Triton X-100-insoluble fraction, compared to the one without WR domain. We suggest that the cytoplasmic region containing the WR may be responsible for their difference in solubility. (C) 2011 Elsevier Ireland Ltd. All rights reserved.