Differential localization of protein kinase C isotypes in equine eosinophils and neutrophils

Phorbol esters, which activate protein kinase C (PKC), stimulate equine eos inophil superoxide production and adherence. After showing that superoxide production could be inhibited by the nonselective PKC inhibitors, staurospo rine and bisindolymaleimide I, the PBC isotypes in equine eosinophils were characterized, because evidence suggests that individual isotypes may play distinct roles in regulating eosinophil function, Western blots demonstrate d that equine eosinophils expressed PKC alpha, beta, delta, epsilon, iota, and zeta, However, unlike the equine neutrophil, the majority of the PKC wa s detected in the particulate fraction of the cell. Despite this unusual lo cation, the PKC in equine eosinophils was activatable, suggesting that it i s functionally competent. The regulatory role of PKC in equine eosinophils may reflect the association of activity with the particulate fraction and t he profile of isotype expression.