Oleoylamine and sphingosine stimulation of phosphatidylserine synthesis by LAN-2 cells is protein kinase C independent

The presence of sphingosine and oleoylamine in the culture medium of LA-N-2 cells stimulated the incorporation of [3H]serine into its corresponding phospholipid, phosphatidylserine (PtdSer). The optimum stimulation for sphingosine and oleoylamine were 50 microM and 100 microM, respectively. Oleoylamine increased the incorporation of [3H]serine over 6-fold while sphingosine increased the incorporation of [3H]serine over 2.5-fold. The amount of radioactivity found in water-soluble components and in protein was similar to that found with control LA-N-2 cells. The incorporation of [3H]choline and [3H]ethanolamine into their corresponding phospholipids were decreased in the presence of either oleoylamine or sphingosine. A protein kinase C (PKC) activator, DiC8, and a PKC inhibitor, H7, did not influence the enhanced phosphatidylserine formation by sphingosine and oleoylamine. In addition, there were no differences in the stimulatory effect of sphingosine and oleoylamine discernable between PKC down-regulated cells or controls. These observations indicate that this oleoylamine and sphingosine mediated enhanced phosphatidylserine synthesis is PKC-independent.