The PH domain adaptor protein Bam32/DAPP1 functions in mast cells to restrain Fc[inline image]RI-induced calcium flux and granule release

• Published in: Molecular immunology 2010-12, Vol.48 (1-3), p.89-97
• Main Authors: Hou, Sen, Pauls, Samantha D, Liu, Peimei, Marshall, Aaron J
• Format: Article
• Language: English
• ISSN: 0161-5890
• DOI: 10.1016/j.molimm.2010.09.007

Mast cell activation triggered by IgE binding to its high affinity receptor Fc[inline image]RI is highly dependent on signaling via phosphoinositde 3-kinases (PI3K). The phosphoinositide phosphatase SHIP controls mast cell activation by regulating accumulation of D3 phosphoinositide second messengers generated by PI3K. The PH domain adaptor protein Bam32/DAPP1 binds specifically to the D3 phosphoinositides PI(3,4,5)P3 and PI(3,4)P2 (the substrate and product of SHIP respectively). In B cells, Bam32 is phosphorylated by Src family kinases including Lyn, and is required for antigen receptor-induced activation; however the function of Bam32 in mast cells is unknown. Here we report that Bam32 is expressed in mast cells, is recruited to the plasma membrane upon stimulation and functions in Fc[inline image]RI signaling. Examination of bone marrow-derived mast cells (BMMC) isolated from Bam32-deficient mice revealed enhanced Fc[inline image]RI-induced degranulation and IL-6 production, indicating that Bam32 may function to restrain signaling via Fc[inline image]RI. These enhanced degranulation responses were PI3K-dependent, as indicated by blockade with PI3K inhibitors wortmannin or IC87114. While Bam32-deficient BMMC showed reduced Fc[inline image]RI-induced activation of mitogen-activated protein kinases ERK and JNK, Fc[inline image]RI-induced calcium flux and phosphorylation of PLC gamma 1 and Akt were increased. Bam32-deficient BMMC showed significantly reduced phosphorylation of Lyn and SHIP, indicating reduced activity of inhibitory signaling pathways. Together our results identify Bam32 as a novel regulator of mast cell activation, potentially functioning in membrane-proximal integration of positive and negative signaling pathways.