TY - JOUR
T1 - Role of acidic compartments in Trypanosoma brucei, with special reference to low-density lipoprotein processing
AU - Coppens, Isabelle
AU - Baudhuin, Pierre
AU - Opperdoes, Fred R.
AU - Courtoy, Pierre J.
N1 - Funding Information:
The authors would like to thank Ms Mich6le Leruth-Deridder for analysis of the scanned gels, Lac Thanh-Vollemaere for cytochemistry and Anne Van Rompaye for isolation of trypanosomes. This investigation was supported in part by the UNDP/World bank/WHO Special Programme for Research and Training in Tropical Diseases, by grants 2.4549.88, 3.4570.88, 2.4547.91 and 1.5246.91 of the Fonds National de ia Recherche Scientifique, at which PJC was Senior Research Associate, as well. as by the Belgian State (Prime Minister's Office) Science Policy Programming (Concerted Actions, grant 88) and Framework of Interuniversity Attraction Poles (grant 44).
PY - 1993/4
Y1 - 1993/4
N2 - In the bloodstream form of Trypanosoma brucei, specific receptors mediate the endocytosis of host low-density lipoprotein particles. We have explored the fate of ligand and receptor with a biochemical approach, using inhibitors of the endocytotic apparatus. The weak base chloroquine rapidly accumulates in trypanosomes, its uptake is prevented by the proton ionophore monensin, and it induces the swelling of intracellular vacuoles, indicating that their content is acidic. Cell-associated LDL is rapidly degraded into intermediately sized fragments and TCA-soluble material that can be recovered in cell extracts and extracellular medium. Chloroquine, leupeptin and E64, but not PMSF, efficiently prevent LDL proteolysis, suggesting that degradation occurs in those acidic compartment(s) and is mediated by thiol-protease(s). Both monensin and chloroquine decrease the number of LDL receptors exposed at the cell surface, a phenomenon amplified in the presence of LDL. This provides indirect evidence that internalised LDL receptors are recycled at a rate which is slowed down by receptor occupancy and by agents that impair acidification of the endocytic organelles. Finally, chloroquine decreases by half the growth rate of procyclic trypanosomes in vitro at 5 μg ml-1. At 40 mg kg-1 per day, it also slows down the increase in parasitaemia and prolongs the survival time of infected mice by up to 2 days.
AB - In the bloodstream form of Trypanosoma brucei, specific receptors mediate the endocytosis of host low-density lipoprotein particles. We have explored the fate of ligand and receptor with a biochemical approach, using inhibitors of the endocytotic apparatus. The weak base chloroquine rapidly accumulates in trypanosomes, its uptake is prevented by the proton ionophore monensin, and it induces the swelling of intracellular vacuoles, indicating that their content is acidic. Cell-associated LDL is rapidly degraded into intermediately sized fragments and TCA-soluble material that can be recovered in cell extracts and extracellular medium. Chloroquine, leupeptin and E64, but not PMSF, efficiently prevent LDL proteolysis, suggesting that degradation occurs in those acidic compartment(s) and is mediated by thiol-protease(s). Both monensin and chloroquine decrease the number of LDL receptors exposed at the cell surface, a phenomenon amplified in the presence of LDL. This provides indirect evidence that internalised LDL receptors are recycled at a rate which is slowed down by receptor occupancy and by agents that impair acidification of the endocytic organelles. Finally, chloroquine decreases by half the growth rate of procyclic trypanosomes in vitro at 5 μg ml-1. At 40 mg kg-1 per day, it also slows down the increase in parasitaemia and prolongs the survival time of infected mice by up to 2 days.
KW - Chloroquine
KW - Endocytosis
KW - LDL proteolysis
KW - LDL receptor recycling
KW - Monensin
KW - Trypanosoma brucei
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U2 - 10.1016/0166-6851(93)90044-X
DO - 10.1016/0166-6851(93)90044-X
M3 - Article
C2 - 8479447
AN - SCOPUS:0027462199
SN - 0166-6851
VL - 58
SP - 223
EP - 232
JO - Molecular and Biochemical Parasitology
JF - Molecular and Biochemical Parasitology
IS - 2
ER -