Localized measurement of kinase activation in oocytes of Xenopus laevis

We have combined a rapid cytoplasmic sampling technique with capillary electrophoresis to measure the activation of protein kinase C (PKC) in a small region (approximately 60 μm) of a Xenopus oocyte. The phosphorylation of a fluorescent PKC substrate was measured following addition of a pharmacological or physiological stimulus to an oocyte. When substrates for cdc2 kinase (cdc2K), PKC, and protein kinase A (PKA) were comicroinjected into an oocyte, all three substrates could be identified on the electropherogram after cytoplasmic sampling. With this new method, it should be possible to measure simultaneously the activation of multiple different kinases in a single cell, enabling the quantitative dissection of signal transduction pathways.