title: LASS5 is the predominant ceramide synthase isoform involved in de novo sphingolipid synthesis in lung epithelia.
abstract: Ceramide is a key bioactive mediator that inhibits surfactant phosphatidylcholine (PtdCho) synthesis in lung epithelia. Ceramide availability is governed by sphingomyelin (SM) hydrolysis, but less is known regarding its de novo synthesis. In this study, we observed that ceramide synthesis within murine lung epithelia was associated with high-level ceramide synthase (dihydroceramide synthase) activity. Longevity assurance homolog 5 (LASS5) was the predominant ceramide synthase isoform detected in lung epithelia, whereas relatively lower level expression was detected for the other five mammalian homologs. Pulmonary LASS5 was developmentally regulated, but its expression was spatially and gender nonspecific. Exogenously expressed LASS5 in lung epithelia was membrane-associated, triggering increased ceramide synthesis, whereas knockdown studies using fumonisin B1 or LASS5 small, interfering RNA reduced ceramide synthase activity by 78% or 45%, respectively. Overexpression of LASS5 also reduced PtdCho synthesis, but maximal inhibition was achieved when LASS5 was coexpressed with a plasmid encoding a neutral sphingomyelinase involved in SM hydrolysis. These results demonstrate that LASS5 is the major ceramide synthase gene product involved in sphingolipid production that may also regulate PtdCho metabolism in pulmonary epithelia.
authors.affiliation: Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA.
authors.forename: Zhiwei
authors.initials: Z
authors.lastname: Xu
authors.forename: Jiming
authors.initials: J
authors.lastname: Zhou
authors.forename: Diann M
authors.initials: DM
authors.lastname: McCoy
authors.forename: Rama K
authors.initials: RK
authors.lastname: Mallampalli
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism; D002518:Ceramides / Q000378:metabolism; D003001:Cloning, Molecular; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000166:cytology* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D020868:Gene Silencing; D005822:Genetic Vectors; D006868:Hydrolysis; D008168:Lung / Q000166:cytology / Q000196:embryology / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D010088:Oxidoreductases / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D020033:Protein Isoforms; D012313:RNA / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013107:Sphingolipids / Q000378:metabolism*; D013347:Subcellular Fractions; D013997:Time Factors; D014162:Transfection
chemical_list: D002518:Ceramides; D010713:Phosphatidylcholines; D020033:Protein Isoforms; D034741:RNA, Small Interfering; D013107:Sphingolipids; D012313:RNA; D010088:Oxidoreductases; C108138:dihydroceramide desaturase