Synthetic arrest of Man 5 GlcNAc 2 -PP-Dol increases procyclin mRNA level and induces cell death in the bloodstream form Trypanosoma brucei brucei

The biosynthesis of N-linked glycan precursors in the endoplasmic reticulum is important for many eukaryotes. In particular, the synthesis of Man GlcNAc -PP-dolichol (M5-DLO) at the cytoplasmic face of the endoplasmic reticulum is essential for maintaining cellular functions. In Trypanosoma brucei, the unicellular organism that causes African trypanosomiasis, homologs of the mannosyltransferases ALG2 and ALG11, which are involved in the biosynthesis of M5-DLO, are found, but the effects of their deletion on cells remain unknown. In this study, we generated conditional gene knockout strains of TbALG2 and TbALG11 in the bloodstream form T. brucei. Decreased N-linked glycosylation and cell death were observed in both strains under non-permissive conditions, with TbALG2 having a greater effect than TbALG11. Transcriptomic analysis of cells losing expression of TbALG11 showed decrease in mRNAs for enzymes involved in glucose metabolism and increase in mRNAs for procyclins and variant surface glycoproteins. These results indicate that the M5-DLO biosynthetic pathway is essential for the proliferation of the bloodstream form T. brucei. They also suggest that the failure of this pathway induces the transcriptomic change.