ROLE OF ACIDIC COMPARTMENTS IN TRYPANOSOMA-BRUCEI, WITH SPECIAL REFERENCE TO LOW-DENSITY-LIPOPROTEIN PROCESSING
ROLE OF ACIDIC COMPARTMENTS IN TRYPANOSOMA-BRUCEI, WITH SPECIAL REFERENCE TO LOW-DENSITY-LIPOPROTEIN PROCESSING
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DOI：
10.1016/0166-6851(93)90044-x
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发表时间：
1993-04-01
影响因子：
1.5
通讯作者：
COURTOY, PJ
中科院分区：
文献类型：
--
作者：
COPPENS, I;BAUDHUIN, P;COURTOY, PJ
在血流形式的布氏锥虫中，特异性受体介导宿主低密度脂蛋白颗粒的内吞作用。我们已经探索了命运的配体和受体的生化方法，使用抑制剂的内吞装置。弱碱性氯喹在锥虫中迅速积累，其摄取被质子离子载体莫能菌素阻止，并诱导细胞内空泡肿胀，表明其内容物是酸性的。细胞相关LDL迅速降解为中等大小的片段和TCA可溶性物质，可在细胞提取物和细胞外培养基中回收。氯喹、亮抑酶肽和E64，而不是PMSF，有效地防止LDL蛋白水解，表明降解发生在那些酸性隔室中，并且由巯基蛋白酶介导。莫能菌素和氯喹都能减少暴露在细胞表面的LDL受体的数量，这是一种在LDL存在下放大的现象。这提供了间接的证据，即内化的LDL受体以一定的速率再循环，该速率被受体占据和损害内吞细胞器酸化的试剂减慢。最后，氯喹在5 μ g ml-1时，可使原环锥虫体外生长速率降低一半。在每天40 mg kg-1的剂量下，它还减缓了寄生虫血症的增加，并使受感染小鼠的存活时间延长了2天。
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 mug 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.