Type II phosphatidylinositol 4-kinases interact with FcεRIγ subunit in RBL-2H3 cells.

Ligation of high-affinity IgE receptor I (FceRI) on RBL-2H3 cells leads to recruitment of FceRI and type II phosphatidylinositol 4-kinases (PtdIns 4-kinases) into lipid rafts. Lipid raft integrity is required for the activation of type II PtdIns 4-kinases and signal transduction through FceRIc during RBL-2H3 cell activation. However, the molecular mechanism by which PtdIns 4-kinases are coupled to FceRI signaling is elusive. Here, we report association of type II PtdIns 4-kinase activity with FceRIc subunit in anti-FceRIc immunoprecipitates. FceRIc-associated PtdIns 4-kinase activity increases threefold upon FceRI ligation in anti- FceRIc immunoprecipitates. Biochemical characterization of PtdIns 4-kinase activity associated with FceRIc reveals that it is a type II PtdIns 4-kinases. Canonical tyrosine resi- dues mutation in FceRIc ITAM (Y65 and Y76) reveals that these two tyrosine residues in c subunit are required for its interaction with type II PtdIns 4-kinases.