We recently described a new route for the synthesis of PtdEtn from exogenous lyso-PtdEtn, which we have termed the exogenous lysolipid metabolism (ELM) pathway. The ELM pathway for lyso-PtdEtn requires the action of plasma membrane P-type ATPases Dnf1p and Dnf2p, and their requisite ss-subunit, Lem3p, for the active uptake of lyso-PtdEtn. In addition, the acyl-CoA dependent acyltransferase, Ale1p, mediates the acylation of the imported lysolipid to form PtdEtn. We now report that these components of the lyso-PtdEtn ELM pathway are also active with lyso-PtdCho as a substrate. Lyso-PtdCho supports the growth of a choline auxotrophic pem1 pem2 strain. Uptake of radiolabeled lyso-PtdCho was impaired by the dnf2 and lem3 mutations. Introduction of a lem3 mutation into a pem1 pem2 background impaired the ability of the resulting strain to grow with lyso-PtdCho as the sole precursor of PtdCho. After import of lyso-PtdCho, the recently characterized lyso-PtdEtn acyltransferase, Ale1p, functioned as the sole lyso-PtdCho acyltransferase in yeast. A pem1 pem2 ale1 strain grew with lyso-PtdCho as a substrate, but showed a profound reduction in PtdCho content when lyso-PtdCho was the only precursor of PtdCho. Ale1p acylates lyso-PtdCho with a preference for monounsaturated acyl-CoA species, and the specific LPCAT activity of Ale1p in yeast membranes is >50 fold higher than the basal rate of de novo aminoglycerophospholipid biosynthesis from PtdSer synthase activity. In addition to lyso-PtdCho, lyso-PtdEtn, and lyso-PtdOH, Ale1p was also active with lyso-PtdSer, lyso-PtdGro, and lyso-PtdIns as substrates. These results establish a new pathway for the net synthesis of PtdCho in yeast, and provide new tools for the study of PtdCho synthesis, transport, and remodeling.
|Evidence ID||Analyze ID||Interactor||Interactor Systematic Name||Interactor||Interactor Systematic Name||Type||Assay||Annotation||Action||Modification||Phenotype||Source||Reference||Note|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Gene Ontology Term||Gene Ontology Term ID||Qualifier||Aspect||Method||Evidence||Source||Assigned On||Reference||Annotation Extension|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Phenotype||Experiment Type||Experiment Type Category||Mutant Information||Strain Background||Chemical||Details||Reference|
|Evidence ID||Analyze ID||Regulator||Regulator Systematic Name||Target||Target Systematic Name||Experiment||Conditions||Strain||Source||Reference|