Expression and activation of protein kinase C-zeta in eosinophils after allergen challenge

Protein kinase (PK) C is an increasingly diverse family of enzymes that has been implicated in a range of cellular functions within the eosinophil. Us ing isoform-specific polyclonal antibodies, we have explored the expression of PKC isoforms in circulating eosinophils. Initial studies demonstrated t he presence of the alpha, beta I, beta II, and zeta and the low-level expre ssion of the delta, epsilon, iota, and mu isoforms but no detectable expres sion of the gamma, eta, and theta isoforms in both normal and asthmatic sub jects. There was no difference in the total protein expression between thes e two groups. Subsequent studies examined the expression and activation of PKC isoforms in circulating eosinophils from asthmatic patients before and 24 h after a late asthmatic response to an inhaled allergen. Cellular fract ionation showed PKC-alpha and PKC-beta II to be mainly located in the cytos ol, whereas PKC-beta I was constitutively more expressed in the membrane. N o changes in expression or subcellular localization of these isoforms were seen after allergen challenge. In contrast, PKC-zeta expression was increas ed after allergen challenge, and we demonstrated a significant PKC-zeta tra nslocation to the membrane, in keeping with activation of the enzyme. Our r esults suggest that 24 h after allergen exposure of asthmatic patients, the re is increased expression and activation of eosinophil PKC-zeta that corre lates with late asthmatic responses recorded between 4 and 10 h postallerge n challenge.