In T. brucei, PC is synthesized solely by the CDP-choline branch of the Kennedy pathway, while PE is produced exclusively via the CDP-ethanolamine branch of the Kennedy pathway [67, 69, 70]. Disruption of the enzymes of the CDP-ethanolamine pathway by RNA interference have shown that this branch of the Kennedy pathway is essential for both procyclic and bloodstream form T. brucei cell growth [69, 71]. PE and phosphatidylinositol (PI) are key phospholipids involved in the biosynthesis of glycosylphosphatidylinositol Trichostatin A solubility dmso (GPI). In trypanosomes,
a large number of surface proteins with critical role in virulence surface proteins are anchored to the plasma membrane via GPI molecules. One of these proteins is the variant surface glycoprotein (VSG), a major virulence factor that undergoes antigenic variation and enables the parasite to evade the immune system of its mammalian host . The steps involved in the biosynthesis of GPI, a process essential for T. brucei bloodstream form survival, have been
well studied. This synthesis differs in certain aspects from the pathway in mammalian cells and yeast. In T. brucei, the pool of PI used for GPI synthesis Ku-0059436 mouse is supplied from glucose-6-phosphate by the action of PI synthase, an enzyme shown to be essential in both bloodstream and procyclic form learn more trypanosomes [68, 70, 71]. A crucial step in the GPI synthesis pathway is the transfer of phosphoethanolamine (PEtN) to mannose residues on the growing GPI. In this reaction, the ethanolamine moiety is provided by PE . As described earlier, synthesis of PE in T. brucei is carried out via the CDP-ethanolamine branch of the Kennedy pathway using DAG as the initial substrate. It has been demonstrated that inhibition of PE synthesis prevents de novo GPI biosynthesis . As we demonstrated in the current paper that TbLpn catalyzes the dephosphorylation of PA into DAG, it is attractive to speculate that TbLpn plays an important role in GPI biosynthesis, and thus in the expression of this isometheptene major virulence factor.
Conclusion The results clearly identify TbLpn as a new member of the lipin family of proteins. The presence of the conserved N-LIP and C-LIP domains, and especially the ability of recombinant TbLpn to dephosphorylate phosphatidic acid indicate that this enzyme is likely to be involved in phospholipid biosynthesis in trypanosomes. Finally, the observation that, in vivo, TbLpn contains methylated arginine residues is very significant, as it is the only lipin or phosphatidic acid phosphatase to date to exhibit such a post-translational modification. Methods Trypanosome growth Procyclic form T. brucei brucei clone IsTaR1 stock EATRO 164 was grown as described in SDM-79 medium supplemented with 15% fetal bovine serum (FBS) .