title: Fatty acid 2-hydroxylase regulates cAMP-induced cell cycle exit in D6P2T schwannoma cells.
abstract: Sphingolipids are ubiquitous components of eukaryotic cells that regulate various cellular functions. In many cell types, a fraction of sphingolipids contain 2-hydroxy fatty acids, produced by fatty acid 2-hydroxylase (FA2H), as the N-acyl chain of ceramide [hydroxyl fatty acid (hFA)-sphingolipids]. FA2H is highly expressed in myelin-forming cells of the nervous system and in epidermal keratinocytes. While hFA-sphingolipids are thought to enhance the physical stability of specialized membranes produced by these cells, physiological significance of hFA-sphingolipids in many other cell types is unknown. In this study, we report novel roles for FA2H and hFA-sphingolipids in the regulation of the cell cycle. Treatment of D6P2T Schwannoma cells with dibutyryl-cAMP (db-cAMP) induced exit from the cell cycle with concomitant upregulation of FA2H. Partial silencing of FA2H in D6P2T cells resulted in 60-70% reduction of hFA-dihydroceramide and hFA-ceramide, with no effect on nonhydroxy dihydroceramide and ceramide. Under these conditions, db-cAMP no longer induced cell cycle exit, and cells continued to grow and divide. Immunoblot analyses revealed that FA2H silencing prevented db-cAMP-induced upregulation of cyclin-dependent kinase inhibitors p21 and p27. These results provide evidence that FA2H is a negative regulator of the cell cycle and facilitates db-cAMP-induced cell cycle exit in D6P2T cells.
authors.affiliation: Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA.
authors.forename: Nathan L
authors.initials: NL
authors.lastname: Alderson
authors.forename: Hiroko
authors.initials: H
authors.lastname: Hama
mesh_terms: D000818:Animals; D003994:Bucladesine / Q000494:pharmacology*; D002453:Cell Cycle / Q000187:drug effects* / Q000502:physiology*; D045744:Cell Line, Tumor; D002518:Ceramides / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism; D020868:Gene Silencing; D006899:Mixed Function Oxygenases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D009442:Neurilemmoma / Q000201:enzymology* / Q000473:pathology*; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D013107:Sphingolipids / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D002518:Ceramides; D005227:Fatty Acids; D034741:RNA, Small Interfering; D013107:Sphingolipids; D003994:Bucladesine; D006899:Mixed Function Oxygenases; C019081:fatty acid alpha-hydroxylase