Special sphingolipids in skin and testis

(R. Sandhoff)

Expression of conventional and ultra long chain-polyunsaturated sphingolipids during spermatogenesis. Modified from R. Sandhoff (2010) FEBS Lett. 584:1907-13.
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In most cells the acyl moieties of sphingolipids are of long chain type (C16-C24) and often saturated. In skin, however, a substantial amount of ceramides contains amide-bound ultra long chain (C >28) and omega-hydroxylated fatty acids (omegaOH-ULC-FAs). Together with other ceramides, cholesterol and free fatty acids they are found in extracellular lipid lamellae of the stratum corneum, where they help to establish the epidermal water permeability barrier (WPB). This WPB prevents land dwelling animals from desiccation. As a consequence, a complete block in the biosynthesis of ceramides with omegaOH-ULC-FAs leads to death within hours. Elucidating intracellular biosynthesis, regulation and transport of ceramides with ULC-FAs is a fundamental requirement for understanding skin pathophysiology, and therefore is part of our current research.
Differentiating male germ cells are the other cell type so far known to express sphingolipids with ULC-FA moieties. However, the ULC-FAs of these sphingolipids are polyunsaturated (ULC-PUFAs). We could show that these complex glycolipids are essential for spermatogenesis. Their molecular function is still unresolved and this is part of our current research.

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