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 (FcεRI) on mast cells results in rapid increases in intracellular free calcium concentration [Ca(2+)]i and consequent activation of many transcription factors, including NFAT, NF-κB, JNK and CREB. Ca(2+) signaling is essential for many cellular activities such as proliferation, gene expression and degranulation in mast cells. In addition to Ca(2+) signaling, previous reports have shown that IkappaB kinase 2 (IKK2 or IKKβ), a central component of the IKK complex mediating NF-κB activation, also plays a crucial role in FcεRI-mediated degranulation and cytokine production. Moreover, it has been demonstrated that activation of PKCβ, a calcium-dependent PKC isoform, leads to IKK2 activation in many cell types. However, the roles of Ca(2+) signaling and PKCβ in the activation of IKK2 in mast cells remain largely unknown. METHODS: We investigated the effect of PKC inhibitor Gö6976 on calcium ionophore A23187-induced activation of IKK2 in mast cells. We also examined the role of IKK2 in A23187-induced NF-κB-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-κB even in the presence of Gö6976 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: Ca(2+)-IKK2 signaling is involved in the degranulation and cytokine production in activated mast cells by a mechanism independent of PKCβ.
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 (FcεRI) on mast cells results in rapid increases in intracellular free calcium concentration [Ca(2+)]i and consequent activation of many transcription factors, including NFAT, NF-κB, JNK and CREB. Ca(2+) signaling is essential for many cellular activities such as proliferation, gene expression and degranulation in mast cells. In addition to Ca(2+) signaling, previous reports have shown that IkappaB kinase 2 (IKK2 or IKKβ), a central component of the IKK complex mediating NF-κB activation, also plays a crucial role in FcεRI-mediated degranulation and cytokine production. Moreover, it has been demonstrated that activation of PKCβ, a calcium-dependent PKC isoform, leads to IKK2 activation in many cell types. However, the roles of Ca(2+) signaling and PKCβ in the activation of IKK2 in mast cells remain largely unknown. METHODS: We investigated the effect of PKC inhibitor Gö6976 on calcium ionophore A23187-induced activation of IKK2 in mast cells. We also examined the role of IKK2 in A23187-induced NF-κB-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-κB even in the presence of Gö6976 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:Ca(2+)-IKK2 signaling is involved in the degranulation and cytokine production in activated mast cells by a mechanism independent of PKCβ.
Authors: Sebastian Drube; Franziska Weber; Christiane Göpfert; Romy Loschinski; Mandy Rothe; Franziska Boelke; Michaela A Diamanti; Tobias Löhn; Julia Ruth; Dagmar Schütz; Norman Häfner; Florian R Greten; Ralf Stumm; Karin Hartmann; Oliver H Krämer; Anne Dudeck; Thomas Kamradt Journal: Oncotarget Date: 2015-10-06