FA2H is responsible for the formation of 2-hydroxy galactolipids in peripheral nervous system myelin

Abstract

Myelin in the mammalian nervous system has a high concentration of galactolipids [galactosylceramide (GalCer) and sulfatide] with 2-hydroxy fatty acids. We recently reported that fatty acid 2-hydroxylase (FA2H), encoded by the FA2H gene, is the major fatty acid 2-hydroxylase in the mouse brain. In this report, we show that FA2H also plays a major role in the formation of 2-hydroxy galactolipids in the peripheral nervous system. FA2H mRNA and FA2H activity in the neonatal rat sciatic nerve increased rapidly during developmental myelination. The contents of 2-hydroxy fatty acids were ?5% of total galactolipid fatty acids at 4 days of age and increased to 60% in GalCer and to 35% in sulfatides at 60 days of age. The chain length of galactolipid fatty acids also increased significantly during myelination. FA2H expression in cultured rat Schwann cells was highly increased in response to dibutyryl cyclic AMP, which stimulates Schwann cell differentiation and upregulates myelin genes, such as UDP-galactose:ceramide galactosyltransferase and protein zero. These observations indicate that FA2H is a myelination-associated gene. FA2H-directed RNA interference (RNAi) by short-hairpin RNA expression resulted in a reduction of cellular 2-hydroxy fatty acids and 2-hydroxy GalCer in D6P2T Schwannoma cells, providing direct evidence that FA2H-dependent fatty acid 2-hydroxylation is required for the formation of 2-hydroxy galactolipids in peripheral nerve myelin. Interestingly, FA2H-directed RNAi enhanced the migration of D6P2T cells, suggesting that, in addition to their structural role in myelin, 2-hydroxy lipids may greatly influence the migratory properties of Schwann cells.-Maldonado, E. N., N. L. Alderson, P. V. Monje, P. M. Wood, and H. Hama. FA2H is responsible for the formation of 2-hydroxy galactolipids in peripheral nervous system myelin. J. Lipid Res. 2008. 49: 153-161.

Survival strategies of a sterol auxotroph

“…To survive under these conditions, Drosophila increase production of sphingolipids with a doubly desaturated LCB and hydroxylated fatty acid moieties. Sphingolipid hydroxylation promotes hydrogen bonding and tighter packing (Lofgren and Pascher, 1977), and these lipids are abundant in membranes that are specialized to perform barrier functions, such as myelin and the gut apical membrane (Maldonado et al, 2008;Uchida et al, 2007). Thus, it seems plausible that these lipids might substitute for sterols in maintaining some biophysical properties of the membrane, such as impermeability.…”

“…No enzyme that produces sphingolipid bases with two double bonds has yet been identified in any organism; however, the Drosophila genome contains a single homolog of fatty acid 2-hydroxylase (FA2H). This enzyme generates the a-hydroxy fatty acids present in some vertebrate sphingolipids (Maldonado et al, 2008;Mizutani et al, 2008;Uchida et al, 2007). To determine whether it has a similar activity in Drosophila, we altered its levels and measured the resulting changes in sphingolipid fatty acid hydroxylation.…”

Fatty acid 2-hydroxylase regulates cAMP-induced cell cycle exit in D6P2T Schwannoma cells

“…Interestingly, silencing FA2H expression in epidermal keratinocytes not only reduced the synthesis of hFA-sphingolipids, but also resulted in profound disturbance of lamellar body formation and intracellular transport (24). In D6P2T Schwannoma cells, migration properties were enhanced by silencing FA2H expression (23). These observations suggest that FA2H and hFA-sphingolipids regulate specific intracellular processes, although underlying molecular mechanisms for these effects are unknown.…”

“…cDNA was synthesized using the Bio-Rad iScript cDNA synthesis kit. Realtime quantitative PCR was performed on a BioRad MyiQ singlecolor, real-time PCR detection system as described (23). The abundance of FA2H mRNA was normalized against 18S rRNA content using the DDC t method (26).…”

“…1). FA2H is required for the synthesis of hFAgalactolipids in myelin (21)(22)(23) and hFA-ceramide and hFA-glucosylceramide in the epidermis (24). During development, FA2H expression is highly upregulated as myelinforming cells and epidermal keratinocytes begin to produce large quantities of hFA-sphingolipids.…”