Cloning of Trypanosoma brucei and Leishmania major genes encoding the GlcNAc-phosphatidylinositol de-N-acetylase of glycosylphosphatidylinositol biosynthesis that is essential to the African sleeping sickness parasite.
The second step of glycosylphosphatidylinositol anchor biosynthesis in all eukaryotes is the conversion of D-GlcNAcalpha1-6-d-myo-inositol-1-HPO(4)-sn-1,2-diacylglycerol (GlcNAc-PI) to d-GlcNalpha1-6-d-myo-inositol-1-HPO(4)-sn-1,2-diacylglycerol by GlcNAc-PI de-N-acetylase. The genes encoding this activity are PIG-L and GPI12 in mammals and yeast, respectively. Fragments of putative GlcNAc-PI de-N-acetylase genes from Trypanosoma brucei and Leishmania major were identified in the respective genome project data bases. The full-length genes TbGPI12 and LmGPI12 were subsequently cloned, sequenced, and shown to complement a PIG-L-deficient Chinese hamster ovary cell line and restore surface expression of GPI-anchored proteins. A tetracycline-inducible bloodstream form T. brucei TbGPI12 conditional null mutant cell line was created and analyzed under nonpermissive conditions. TbGPI12 mRNA levels were reduced to undetectable levels within 8 h of tetracycline removal, and the cells died after 3-4 days. This demonstrates that TbGPI12 is an essential gene for the tsetse-transmitted parasite that causes Nagana in cattle and African sleeping sickness in humans. It also validates GlcNAc-PI de-N-acetylase as a potential drug target against these diseases. Washed parasite membranes were prepared from the conditional null mutant parasites after 48 h without tetracycline. These membranes were shown to be greatly reduced in GlcNAc-PI de-N-acetylase activity, but they retained their ability to make GlcNAc-PI and to process d-GlcNalpha1-6-d-myo-inositol-1-HPO(4)-sn-1,2-diacylglycerol to later glycosylphosphatidylinositol intermediates. These results suggest that the stabilities of other glycosylphosphatidylinositol pathway enzymes are not dependent on GlcNAc-PI de-N-acetylase levels.
D000581:Amidohydrolases / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D015139:Blotting, Southern; D016466:CHO Cells; D002474:Cell-Free System; D002851:Chromatography, High Pressure Liquid; D003001:Cloning, Molecular; D006224:Cricetinae; D005816:Genetic Complementation Test; D017261:Glycosylphosphatidylinositols / Q000096:biosynthesis*; D018320:Leishmania major / Q000235:genetics*; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D016366:Open Reading Frames; D017386:Sequence Homology, Amino Acid; D013997:Time Factors; D014346:Trypanosoma brucei brucei / Q000235:genetics*; D014353:Trypanosomiasis, African / Q000469:parasitology*
D017261:Glycosylphosphatidylinositols; D000581:Amidohydrolases; C087696:N-acetylglucosaminyl-phosphatidylinositol de-N-acetylase