Role of Calcium Ionophore A23187-Induced Activation of IkappaB Kinase 2 in Mast Cells

Background: Mast cells are known to play a pivotal role in allergic diseases by releasing granules containing histamine and other preformed chemical mediators. Cross-linking of high-affinity receptors for IgE (Fc epsilon RI) on mast cells results in rapid increases in intracellular free calcium concentration [Ca2+](i) and consequent activation of many transcription factors, including NFAT, NF-kB, JNK and CREB. Ca2+ signaling is essential for many cellular activities such as proliferation, gene expression and degranulation in mast cells. In addition to Ca2+ signaling, previous reports have shown that IkappaB kinase 2 (IKK2 or IKK beta), a central component of the IKK complex mediating NF-kB activation, also plays a crucial role in Fc epsilon RI-mediated degranulation and cytokine production. Moreover, it has been demonstrated that activation of PKC beta, a calcium-dependent PKC isoform, leads to IKK2 activation in many cell types. However, the roles of Ca 2+ signaling and PKC beta in the activation of IKK2 in mast cells remain largely unknown. Methods: We investigated the effect of PKC inhibitor Go6976 on calcium ionophore A23187-induced activation of IKK2 in mast cells. We also examined the role of IKK2 in A23187-induced NF-kB-dependent gene induction, degranulation, proinflammatory cytokine production and extracellular signal-regulated kinases 1 and 2 (ERK1/2) activation by using IKK2-deficient (IKK2(-/-)) fetal liver-derived mast cells (FLMCs). Results: A23187 activated IKK2 and NF-kB even in the presence of Go6976 in mast cells. A23187-induced degranulation, cytokine production and activation of ERK1/2 were diminished in IKK2(-/-)FLMCs compared to those in wild-type FLMCs. Conclusions: Ca2+-IKK2 signaling is involved in the degranulation and cytokine production in activated mast cells by a mechanism independent of PKC beta. Copyright (C) 2013 S. Karger AG, Basel