SHP-1 exhibits a pro-apoptotic function in antigen-stimulated mast cells: positive regulation of mitochondrial death pathways and negative regulation of survival signaling pathways.

Src homology region 2 domain-containing phosphatase-1 (SHP-1) is known to act as a negative signal modulator in mast cells but its roles in cell survival and cell death are poorly understood. We previously reported that SHP-1 also positively regulates mast cell activation signaling by acting as an adaptor protein. In the present study, we examined whether SHP-1 plays a role in antigen (Ag)-induced activation-induced mast cell death. Bone marrow-derived mast cells (BMMCs) from SHP-1-deficient motheaten (me) mice (me-BMMCs) were significantly less susceptible to store-operated Ca(2+) channel (SOC) activation, Ag-induced cell death and DNA fragmentation than BMMCs from their wild-type littermates (WT-BMMCs). Subsequent experiments revealed that the differences in these cellular susceptibilities to SOC activation and cell death resulted from the extent of the mitochondrial permeability transition pore (mPTP) opening. Specifically, mPTP opening was sufficiently persistent in WT-BMMCs to evoke mitochondrial integrity disruption, while mPTP opening was too transient to cause the minimal mitochondrial integrity collapse in me-BMMCs. In addition, pro-survival signaling including activation of mitogen-activated protein kinases (MAPKs) such as the extracellular signal-regulated protein kinases, c-Jun NH(2) terminal kinases and p38 and the expression of Bcl-x(L) were significantly prolonged in me-BMMCs compared with WT-BMMCs. Taken together, these data demonstrate that a lack of SHP-1 prevents the mPTP-mediated mitochondrial integrity collapse and augments anti-apoptotic signaling such as MAPKs and Bcl-x(L). These findings suggest that SHP-1 positively regulates mitochondrial death pathways and negatively regulates pro-survival signaling pathways.