We previously demonstrated that the Fc receptor γ-chain Y58(C-terminal tyrosine) is highly susceptible to dephosphorylation; a mechanism that controls the extent of Syk activation and the downstream signaling in mast cells. Here, we explored the importance of the γ-chain Y47 (N-terminal tyrosine) in mast cell signaling. We generated a highly sensitive and versatile phospho-specific antibody that recognized the phosphorylated Y47 in various species. Using this antibody, we found that mutation of the FcεRIβ Y219 to phenylalanine caused a loss in the phosphorylation of the γ-chain Y47, consistent with the previously described role of Y219 in Lyn association with FcεRIβ a... More
We previously demonstrated that the Fc receptor γ-chain Y58(C-terminal tyrosine) is highly susceptible to dephosphorylation; a mechanism that controls the extent of Syk activation and the downstream signaling in mast cells. Here, we explored the importance of the γ-chain Y47 (N-terminal tyrosine) in mast cell signaling. We generated a highly sensitive and versatile phospho-specific antibody that recognized the phosphorylated Y47 in various species. Using this antibody, we found that mutation of the FcεRIβ Y219 to phenylalanine caused a loss in the phosphorylation of the γ-chain Y47, consistent with the previously described role of Y219 in Lyn association with FcεRIβ and subsequent FcεRIγ phosphorylation. These conditions also diminished the tyrosine phosphorylation of Syk and LAT1 but, surprisingly, not the phosphorylation of Akt at T308. Mutation of Y47 or Y58 of the γ-chain also caused a marked inhibition of Syk and LAT1 phosphorylation, but only the latter mutant showed a reduction in Akt phosphorylation. These findings show that the full phosphorylation of Syk and LAT1 requires the FcεRIβ Y219 and both Y47 and Y58 of the γ-chain. However, T308 phosphorylation of Akt is largely independent of FcεRIγ Y47 phosphorylation and of the Lyn-binding site (Y219) on the FcεRIβ.
