Study on endocytosis and hemoglobin uptake in different developmental stages of Trypanosoma congolense IL3000 strain.

摘要

The study aimed to show endocytosis and hemoglobin uptake in Trypanosoma congolense. All the different developmental stages of T. congolense, IL3000 strain were cultured with dextran Alexa FluorReg. 568 10,000 MW, dextran fluorescein 70,000 MW and hemoglobin labeled with Alexa FluorReg. 488. The trypanosomes were also incubated in HoechstReg. 33342 and observed by confocal laser scanning microscopy. The results showed that non-specific endocytosis was up-regulated in metacyclic form (MCF) and bloodstream form (BSF) whereas receptor-mediated hemoglobin endocytosis was highly activated only in the insect stage epimastigote form (EMF). This might indicate that the rapid uptake of surface-bound molecules in MCF and BSF may be important in the survival of the trypanosomes in the mammalian host. However, there was no observed non-specific endocytosis in the two insect stages procyclic form (PCF) and EMF, which might suggest that these stages totally depend on receptor-mediated endocytosis. Furthermore, the results showed uptake of hemoglobin in EMF but not in other stages. This might explain as to why a haptoglobin-hemoglobin receptor (TcHpHbR) has been specifically expressed in EMF stage of T. congolense. Therefore, TcHpHbR mediated hemoglobin requirement of the insect stage is probably higher than other stages because of their habitat and fully activated mitochondrial metabolism.