Uptake of proteins and degradation of human serum albumin by Plasmodium falciparum-infected human erythrocytes.
BACKGROUND
Intraerythrocytic malaria parasites actively import obligate nutrients from serum and export proteins and lipids to erythrocyte cytoplasm and membrane. The import of macromolecules in the malaria parasite has been the subject of many debates. To understand the import of macromolecules by the parasite, we studied the uptake of proteins by Plasmodium falciparum infected human erythrocyte.


METHODS
Proteins were biotin labelled individually, purified on a gel filtration column and added to uninfected and infected asynchronized culture. The uptake of these proteins by malaria parasites was determined by western blot analysis of parasite pellet and their different fractions using streptavidin-horseradish conjugate. To further confirm this import, we studied the uptake of 125I-labelled proteins by western blot analysis as well as used direct immunofluorescence method.


RESULTS
Here we show that biotin labelled and radio-iodinated polypeptides of molecular sizes in the range of 45 to 206 kDa, when added in the culture medium, get direct access to the parasite membrane through a membrane network by by-passing the erythrocyte cytosol. The import of these polypeptides is ATP-dependent as sodium azide treatment blocks this uptake. We also show that malaria parasites have the ability to take up and degrade biotin labelled human serum albumin, which has been shown to be essential for the parasite growth.


CONCLUSIONS
These results can be used, as a basis to explore the role of human serum albumin in the intraerythrocytic development of parasites, and this in turn can be an important adjunct to the development of novel antimalarial drugs.
El Tahir
Ahmed
A
Department of Biochemistry and Nutrition, Faculty of Medicine, University of Gezira, P.O.Box 20, Sudan. ahmedeltahirm@yahoo.com
Malhotra
Pawan
P
Chauhan
Virander S
VS
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002457:Cell Extracts / Q000737:chemistry; D004912:Erythrocytes / Q000187:drug effects / Q000469:parasitology*; D006801:Humans; D010446:Peptide Fragments / Q000378:metabolism; D010963:Plasmodium falciparum / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism*; D011506:Proteins / Q000737:chemistry / Q000378:metabolism*; D015800:Protozoan Proteins / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012709:Serum Albumin / Q000737:chemistry / Q000378:metabolism*; D019810:Sodium Azide / Q000494:pharmacology; D000099053:Histidine-Rich Glycoprotein
D002457:Cell Extracts; D010446:Peptide Fragments; D011506:Proteins; D015800:Protozoan Proteins; D011994:Recombinant Proteins; D012709:Serum Albumin; D000099053:Histidine-Rich Glycoprotein; D019810:Sodium Azide