The Glycerol‐3‐Phosphate Acyltransferase Tb GAT is Dispensable for Viability and the Synthesis of Glycerolipids in Trypanosoma brucei

Glycerolipids are the main constituents of biological membranes in Trypanosoma brucei , which causes sleeping sickness in humans. Importantly, they occur as a structural component of the glycosylphosphatidylinositol lipid anchor of the abundant cell surface glycoproteins procyclin in procyclic forms and variant surface glycoprotein in bloodstream form, that play crucial roles for the development of the parasite in the insect vector and the mammalian host, respectively. The present work reports the characterization of the glycerol‐3‐phosphate acyltransferase Tb GAT that initiates the biosynthesis of ester glycerolipids. Tb GAT restored glycerol‐3‐phosphate acyltransferase activity when expressed in a Leishmania major deletion strain lacking this activity and exhibited preference for medium length, unsaturated fatty acyl‐CoAs. Tb GAT localized to the endoplasmic reticulum membrane with its N‐terminal domain facing the cytosol. Despite that a Tb GAT null mutant in T. brucei procyclic forms lacked glycerol‐3‐phosphate acyltransferase activity, it remained viable and exhibited similar growth rate as the wild type. Tb GAT was dispensable for the biosynthesis of phosphatidylcholine, phosphatidylinositol, phosphatidylserine, and GPI ‐anchored protein procyclin. However, the null mutant exhibited a slight decrease in phosphatidylethanolamine biosynthesis that was compensated with a modest increase in production of ether phosphatidylcholine. Our data suggest that an alternative initial acyltransferase takes over Tb GAT 's function in its absence.