Fluorescence-based assay of sphingosine kinases

Area of Science:

• Biochemistry
• Enzymology
• Cell Biology

Background:

• Sphingosine kinase (SphK) activity is crucial in cell signaling.
• Traditional assays for SphK activity rely on radiolabeled substrates and complex separation techniques.
• A need exists for simpler, more accessible methods to quantify SphK enzymatic activity.

Purpose of the Study:

• To develop and validate a novel fluorescence-based assay for measuring sphingosine kinase activity.
• To provide a convenient alternative to radiometric assays for SphK activity determination.
• To demonstrate the assay's utility in detecting SphK inhibitors.

Main Methods:

• A novel fluorescent substrate, 15-NBD-Sph (sphingosine derivative labeled with 7-nitrobenz-2-oxa-1,3-diazole), was synthesized.
• Sphingosine-1-phosphate product was separated from the substrate using chloroform/methanol extraction at pH 8.5.
• Fluorescence detection quantified the sphingosine-1-phosphate in the aqueous phase.

Main Results:

• The assay successfully detected phosphorylation of 15-NBD-Sph by human and murine sphingosine kinases 1 and 2.
• The sphingosine-1-phosphate product was recovered with >98% efficiency in the aqueous phase.
• The assay demonstrated suitability for measuring SphK activity in purified enzymes and cell lysates.

Conclusions:

• A robust and convenient fluorescence-based assay for sphingosine kinase activity has been established.
• This assay serves as a valuable alternative to radiometric methods, simplifying SphK activity measurement.
• The developed method is well-suited for high-throughput screening and the discovery of novel SphK inhibitors.