Fatty acid metabolism in kinetoplastid parasites : from exploring the activity of Δ6-desaturase to building a PUFAs cell-factory

Abstract

Fatty acids (FAs) are exceptional biological and chemical molecules. Recently, the attention has been focused on ω-3 polyunsaturated fatty acids (PUFAs) for their benefit to human health. These cannot be produced by humans de novo and must be acquired from our diet. Consequently, their demand is constantly increasing and thus outstripping demand with the ever-decreasing availability of sources of ω-3 PUFAs, such as plant and marine ecosystems, because of agribusiness and climate change. Novel microbial techniques and chemical total synthesis to make high value PUFAs are often costly and challenging. Therefore, there is a constant need to meet the high demand of PUFAs via innovative and bio-sustainable methods. In this scenario, this project focused on formidable producers of PUFAs: kinetoplastid parasites. They possess a unique finely regulated machinery for the biosynthesis of PUFAs. Among those, Trypanosoma brucei and Crithidia fasciculata were chosen to study the activity of a putative Δ6-desaturase from T. brucei (Tb-Δ6), and its homolog in C. fasciculata (Cf-Δ6), via genetic manipulation and chemical alteration of the fat sources in the media. Particularly, T. brucei was used as model system to unveil novel information around the PUFA pathway in these pathogens, for which little is known. Particularly, it was shown that Tb-Δ6 is essential for cell growth in the procyclic and bloodstream forms of T. brucei, and that it works in the de novo synthesis of 22C PUFAs, by displaying an effect on the remodelling of the lipid pool that resembles changes in a life-cycle stage specific manner. C. fasciculata were used as a model system in which to produce PUFAs, by using it to build an innovative PUFAs cell-factory. By overexpressing either the desaturases Cf-Δ6 or Cf-Δ4, in conjunction with the elongase Cf-Elo4, significant amounts of useful ω-3 PUFAs were yielded, that could potentially be added to the food chain at a low-cost and via a bio-sustainable approach.