Stage-specific function of sphingolipid synthases in African trypanosomes.

Unlabelled: The protozoan parasite is the only known eukaryote capable of synthesizing the three main phosphosphingolipids: sphingomyelin (SM), inositol phosphorylceramide (IPC), and ethanolamine phosphorylceramide (EPC). It has four paralogous genes encoding sphingolipid synthases (). TbSLS1 is a dedicated IPC synthase, TbSLS2 is a dedicated EPC synthase, and TbSLS3 and TbSLS4 are bifunctional SM/EPC synthases.

Multifunctional Roles of Sec13 Paralogues in the Euglenozoan .

Secretory cargos are exported from the ER via COPII coated vesicles that have an inner matrix of Sec23/Sec24 heterotetramers and an outer cage of Sec13/Sec31 heterotetramers. In addition to COPII, Sec13 is part of the nuclear pore complex (NPC) and the regulatory SEA/GATOR complex in eukaryotes, which typically have one Sec13 orthologue. The kinetoplastid parasite has two paralogues: TbSec13.

Diversification of sphingolipid synthase activities in kinetoplastid protozoa.

Phosphosphingolipids (PSL) are essential components of eukaryotic membranes. The major PSL in fungi and protists is inositol phosphorylceramide (IPC), while sphingomyelin (SM), and to a lesser extent ethanolamine phosphorylceramide (EPC) predominate in mammals. Most kinetoplastid protozoa have a syntenic locus that encodes a single sphingolipid synthase (SLS) gene.

Turnover of Variant Surface Glycoprotein in Trypanosoma brucei Is Not Altered in Response to Specific Silencing.

African trypanosomes evade the immune system of the mammalian host by the antigenic variation of the predominant glycosylphosphatidylinositol (GPI)-anchored surface protein, variant surface glycoprotein (VSG). VSG is a very stable protein that is turned over from the cell surface with a long half-life (~26 h), allowing newly synthesized VSG to populate the surface. We have recently demonstrated that VSG turnover under normal growth is mediated by a combination of GPI hydrolysis and direct shedding with intact GPI anchors.