title: Human homologues of LAG1 reconstitute Acyl-CoA-dependent ceramide synthesis in yeast.
abstract: Lag1p and Lac1p are two highly homologous membrane proteins of the endoplasmic reticulum. lag1delta lac1delta double mutants in Saccharomyces cerevisiae lack an acyl-CoA-dependent ceramide synthase and are either very sick or nonviable, depending on the genetic background. LAG1 and LAC1 are members of a large eukaryotic gene family that shares the Lag1 motif, and some members of this family additionally contain a DNA-binding HOX homeodomain. Here we show that several human LAG1 homologues can rescue the viability of lag1delta lac1delta yeast cells and restore acyl-CoA-dependent ceramide and sphingolipid biosynthesis. When tested in a microsomal assay, Lac1p and Lag1p had a strong preference for C26:0-CoA over C24:0-CoA, C20-CoA, and C16-CoA, whereas some human homologues preferred C24:0-CoA and CoA derivatives with shorter fatty acids. This suggests that LAG1 proteins are related to substrate recognition and to the catalytic activity of ceramide synthase enzymes. CLN8, another human LAG1 homologue implicated in ceroid lipofuscinosis, could not restore viability to lag1delta lac1delta yeast mutants.
authors.affiliation: Department of Medicine, University of Fribourg, CH-1700 Fribourg, Switzerland.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Guillas
authors.forename: James C
authors.initials: JC
authors.lastname: Jiang
authors.forename: Christine
authors.initials: C
authors.lastname: Vionnet
authors.forename: Carole
authors.initials: C
authors.lastname: Roubaty
authors.forename: Danièle
authors.initials: D
authors.lastname: Uldry
authors.forename: Rachel
authors.initials: R
authors.lastname: Chuard
authors.forename: Jinqing
authors.initials: J
authors.lastname: Wang
authors.forename: S Michal
authors.initials: SM
authors.lastname: Jazwinski
authors.forename: Andreas
authors.initials: A
authors.lastname: Conzelmann
mesh_terms: D000214:Acyl Coenzyme A / Q000378:metabolism*; D001483:Base Sequence; D002518:Ceramides / Q000096:biosynthesis*; D006801:Humans; D008565:Membrane Proteins / Q000502:physiology*; D008861:Microsomes / Q000378:metabolism; D008969:Molecular Sequence Data; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000502:physiology*; D013379:Substrate Specificity
chemical_list: D000214:Acyl Coenzyme A; D002518:Ceramides; C087436:LAG1 protein, S cerevisiae; D008565:Membrane Proteins; D029701:Saccharomyces cerevisiae Proteins