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PROCYCLIC TRYPANOSOMA BRUCEI USES
LIPOPHORIN, THE VECTOR LIPOPROTEIN, AS LIPID SOURCE.
*Simão,A.A., *Ximenes, A., *Atella, G.C.
*Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro
African trypanosomes are flagellated protozoan parasites, causing sleeping sickness in man and related diseases in livestock. Trypanosoma brucei has a biphasic life cycle alternating between the mammalian host and the insect vector tsetse fly. In Trypanosomatids, endocytosis and exocytosis occur exclusively at the flagellar pocket, a deep invagination of the plasma membrane where the flagellum extends from the cell. Both bloodstream and procyclic trypanosomes are capable of internalizing macromolecules
In the invertebrate host hemolymph lipophorin (Lp) is a major haemolymphatic lipoprotein which carries and distributes many lipid classes among the tissues involved in lipid absortion, storage and utilization.
Trypanosomatids have incomplete de novo lipid synthesis. Therefore, they avidly take up lipids from host lipoproteins presumably satisfying their requirements for growth and differentiation. In this work we demonstrate that the parasite was able to uptake lipophorin.
To examine the Lp endocytosis by T. brucei, cells were incubated in the presence of LP-I125. After different times, cells were collected and the radioactivity was determined by gamma counting. Lp was found associated with the parasites and the uptake increased up to 180 minutes. We incubated the parasite in the presence of Pi32. The lipids were extracted and analyzed by thin-layer chromatography. We observed that phosphatidylcholine was the major phospholipid found. These data suggest that T. brucei is capable of receiving lipids from lipophorin; whether this is a specific transfer or and endocytic process remains to be investigated.
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