Differential use of BTK and PLC in FcεRI- and KIT-mediated mast cell activation: A marginal role of BTK upon KIT activation

Publication date: Available online 11 December 2019Source: Biochimica et Biophysica Acta (BBA) - Molecular Cell ResearchAuthor(s): Anne Simonowski, Thomas Wilhelm, Pardes Habib, Carolin N. Zorn, Michael HuberAbstractIn mast cells (MCs), the TEC family kinase (TFK) BTK constitutes a central regulator of antigen (Ag)-triggered, FcεRI-mediated PLCγ phosphorylation, Ca2+ mobilization, degranulation, and pro-inflammatory cytokine production. Less is known about the function of BTK in the context of stem cell factor (SCF)-induced KIT signaling. In bone marrow-derived MCs (BMMCs), Ag stimulation caused intense phosphorylation of BTK at Y551 in its active center and at Y223 in its SH3-domain, whereas in response to SCF only Y223 was significantly phosphorylated. Further data using the TFK inhibitor Ibrutinib indicated that BTK Y223 is phosphorylated by a non-BTK TFK upon SCF stimulation. In line, SCF-induced PLCγ1 phosphorylation was stronger attenuated by Ibrutinib than by BTK deficiency. Subsequent pharmacological analysis of PLCγ function revealed a total block of SCF-induced Ca2+ mobilization by PLC inhibition, whereas only the sustained phase of Ca2+ flux was curtailed in Ag-stimulated BMMCs. Despite this severe stimulus-dependent difference in inducing Ca2+ mobilization, PLCγ inhibition suppressed Ag- and SCF-induced degranulation and pro-inflammatory cytokine production to comparable extents, suggesting involvement of additional TFK(s) or PLCγ-dependent signaling compone...
Source: Biochimica et Biophysica Acta (BBA) Molecular Cell Research - Category: Molecular Biology Source Type: research