The epsilon isoform of protein kinase C is involved in regulation of the LTD4-induced calcium signal in human intestinal epithelial cells

We investigated the potential roles of specific isoforms of protein kinase C (PKC) in the regulation of leukotriene Da-induced Ca2+ signaling in the intestinal epithelial cell line Int 407. RT-PCR and Western blot analysis revealed that these cells express the PKC isoforms alpha, beta II, delta, epsilon, zeta, and mu, but not betaI, gamma, eta, or theta. The inflammatory mediator leukotriene D-4 (LTD4) caused the TPA-sensitive PKC isoforms alpha, delta, and epsilon, but not beta II, to rapidly translocate to a membrane-enriched fraction. The PKC inhibitor GF109203X at 30 muM but not 2 muM significantly impaired the LTD4-induced Ca2+ signal, indicating that the response involves a novel PKC isoform, such as delta or epsilon, but not alpha. LTD4-induced Ca2+ signaling was significantly suppressed in cells pretreated with TPA for 15 min and was abolished when the pretreatment was prolonged to 2 h. Immunoblot analysis revealed that the reduction in the LTD4-induced calcium signal coincided with a reduction in the cellular content of PKC epsilon and, to a Limited extent, PKC delta. LTD4-induced Ca2+ signaling was also markedly suppressed by microinjection of antibodies against PKC epsilon but not PKC delta. These data suggest that PKC epsilon plays a unique role in regulation of the LTD4-dependent Ca2+ signal in intestinal epithelial cells. (C) 2001 Academic Press.