de Kroon, A. I. P. M. | Search bioRxiv

bioRxiv2024

Temperature adaptation of yeast phospholipid molecular species at the acyl chain positional level

The budding yeast Saccharomyces cerevisiae is a poikilothermic organism and adapts its lipid composition to the environmental temperature to maintain membrane physical properties. Studies addressing temperature-dependent adaptation of the lipidome in yeast have described changes in the phospholipid composition at the level of sum composition (e.g. PC 32:1) and molecular composition (e.g. PC 16:0_16:1). However, to date, there is no information at the level of positional isomers (e.g. PC 16:0/16:1 versus PC 16:1/16:0). In this study, combined Collision- and Ozone-Induced Dissociation (CID/OzID) mass spectrometry was deployed to investigate homeoviscous adaptation of PC, PE, and PS sn-molecular species composition. We determined the main species to be 16:1/16:1, 16:0/16:1, 16:1/18:1, 16:0/18:1, and 18:0/16:1. In general, at higher culture temperature, the sn-1 position is increased in saturated acyl chains, whereas the sn-2 position mainly is increased in acyl chain length. PC mainly increases in 16:0/16:1 and 16:0/18:1, at the expense of 16:1/16:1, whereas PS and PE increase in 16:1/18:1, at the expense of 16:1/16:1 and 16:0/16:1. Our data suggest distinct adaptation mechanisms of the sn-1 and sn-2 acyl chains, and different manners of sn-molecular species adaptation between PC and PE/PS.

biochemistry↗

bioRxiv2021

Acyl chain shortening induced by inhibition of acetyl-CoA carboxylase renders phosphatidylcholine redundant

Phosphatidylcholine (PC) is an abundant membrane lipid component in most eukaryotes including yeast. PC has been assigned a multitude of functions in addition to that of building block of the lipid bilayer. Here we show that PC is evolvable essential in yeast by isolating suppressor mutants devoid of PC that exhibit robust growth. The requirement for PC is suppressed by monosomy of chromosome XV, or by a point mutation in the ACC1 gene encoding acetyl-CoA carboxylase. Although these two genetic adaptations rewire lipid biosynthesis differently, both decrease Acc1 activity thereby reducing the average acyl chain length. Accordingly, soraphen A, a specific inhibitor of Acc1, rescues a yeast mutant with deficient PC synthesis. In the aneuploid suppressor, up-regulation of lipid synthesis is instrumental to accomplish feed-back inhibition of Acc1 by acyl-CoA produced by the fatty acid synthase (FAS). The results show that yeast regulates acyl chain length by fine-tuning the activities of Acc1 and FAS, and indicate that PC evolved by benefitting the maintenance of membrane fluidity.

biochemistry↗