Inhibitor screening and selectivity assessment against multiple cellular protein kinases by capillary electrophoresis...

A method that can be used for screening protein kinase inhibitors (PKIs) and simultaneously assessing their selectivity is described. The method is based on simultaneously assaying multiple cellular protein kinases by performing capillary electrophoresis (CE) separation and measuring the peak areas of the phosphorylated substrate peptides. The powerful separation capability of CE combined with the highly sensitive and selective laser-induced fluorescence (LIF) detector enables the direct screening of PKIs against cell lysates, which are used as an inexpensive source of enzymes. Four cell lines, three specific substrate peptides labeled with 5-carboxyfluorescein (5-FAM), two relative specific PKIs (TBB and H-89) and one non-specific PKI (staurosporine) were utilized to prove the methodology. With this method, the inhibitory activity of the tested compounds against multiple protein kinases was identified in parallel by comparing the peak areas of the phosphorylated substrates with those obtained in the absence of any inhibitors. The reduced peak area of the phosphorylated substrate definitively represents a positive screening result. Simultaneously, assaying the inhibition of one inhibitor against mutiple cellular protein kinases enables the assessment of its selectivity. Compared to the conventional, single-target screening format, the cell lysate-based multi-target method is more informative, more straightforward and more cost effective.