Sphingosine kinase assay system with fluorescent detection in high performance liquid chromatography

Activation of Sphingosine kinase (Sphk) increases a bioactive lipid, sphingosine 1-phosphate (S1P) and has been observed in a variety of cancer cells. Therefore, inhibition of Sphk activity was an important target for the development of anticancer drugs. As a searching tool for Sphk inhibitor, we developed fluorescent Sphk activity assay combined with high performance liquid chromatography (HPLC). Previously we established murine teraticarcinoma mutant F9-12 cells which lack S1P lyase and stably express Sphk1. By using F9-12 cells, optimal assay conditions were established as follows; 100 mu M Of C-17-Sph and 30 mu g protein of F9-12 cells lysate in 20 min. Sphingosine analog C17-Sph was efficiently phosphorylated by Sphk activity (K-m:67.08 mu M, V-max :1507.5 pmol/min/mg). New product C17-S1P was separated from S1P in reversed-phase HPLC. In optimized conditions, 300 nM of phorbol 12-myristate 13-acetate (PIMA) increased Sphk activity approximately twice while 20 mu M of N,N-dimethylsphingosine (DIMS) reduced 70% of Sphk activity in F9-12 cells lysate. In conclusion, we established non-radioactive but convenient Sphk assay system by using HPLC and F9-12 cells.