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

Nathan L. Alderson and Hiroko Hama

Biochemistry and Molecular Biology, Medical Univeristy of South Carolina, Charleston, SC 29425-5090

Corresponding Author: hama{at}musc.edu

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 (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 the current 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 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 non-hydroxy 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.

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