Neuropathy target esterase and its yeast homologue degrade phosphatidylcholine to glycerophosphocholine in living cells.
Eukaryotic cells control the levels of their major membrane lipid, phosphatidylcholine (PtdCho), by balancing synthesis with degradation via deacylation to glycerophosphocholine (GroPCho). Here we present evidence that in both yeast and mammalian cells this deacylation is catalyzed by neuropathy target esterase (NTE), a protein originally identified by its reaction with organophosphates, which cause nerve axon degeneration. YML059c, a Saccharomyces cerevisiae protein with sequence homology to NTE, had similar catalytic properties to the mammalian enzyme in assays of microsome preparations and, like NTE, was localized to the endoplasmic reticulum. Yeast lacking YML059c were viable under all conditions examined but, unlike the wild-type strain, did not convert PtdCho to GroPCho. Despite the absence of the deacylation pathway, the net rate of [(14)C]choline incorporation into PtdCho in YML059c-null yeast was not greater than that in the wild type; this was because, in the null strain diminished net uptake of extracellular choline and decreased formation of the rate-limiting intermediate, CDP-choline, resulted in a reduced rate of PtdCho synthesis. In [(14)C]choline labeling experiments with cultured mammalian cell lines, production of [(14)C]GroPCho was enhanced by overexpression of catalytically active NTE and was diminished by reduction of endogenous NTE activity mediated either by RNA interference or organophosphate treatment. We conclude that NTE and its homologues play a central role in membrane lipid homeostasis.
Zaccheo
Oliver
O
Medical Research Council Toxicology Unit and Department of Genetics, University of Leicester, Leicester LE1 9HN, United Kingdom.
Dinsdale
David
D
Meacock
Peter A
PA
Glynn
Paul
P
D000818:Animals; D019556:COS Cells; D002265:Carboxylic Ester Hydrolases / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D002470:Cell Survival; D004305:Dose-Response Relationship, Drug; D004721:Endoplasmic Reticulum / Q000648:ultrastructure; D005838:Genotype; D005997:Glycerylphosphorylcholine / Q000737:chemistry*; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008563:Membrane Lipids / Q000737:chemistry; D018613:Microscopy, Confocal; D008861:Microsomes / Q000378:metabolism; D008954:Models, Biological; D010641:Phenotype; D010713:Phosphatidylcholines / Q000737:chemistry*; D034622:RNA Interference; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D013696:Temperature; D013997:Time Factors; D014162:Transfection
D008563:Membrane Lipids; D010713:Phosphatidylcholines; D005997:Glycerylphosphorylcholine; D002265:Carboxylic Ester Hydrolases; C021859:neurotoxic esterase