Measurement of kinase activation in single mammalian cells

We demonstrate a new method for the simultaneous measurement of the activat ion of key regulatory enzymes within single cells. To illustrate the capabi lities of the technique, the activation of protein kinase C (PKC), protein kinase A (PKA), calcium-calmodulin activated kinase II (CamKII), and cdc2 p rotein kinase (cdc2K) was measured in response to both pharmacological or p hysiological stimuli. This assay strategy should be applicable to a broad r ange of intracellular enzymes, including phosphatases, proteases, nucleases , and other kinases.