Fc-receptor stimulation in myeloid cells results in increased oxygen consumption, termed the respiratory burst, which is coupled to a rapid and transient increase in tyrosine phosphorylation of cellular proteins. In a previous paper in this journal we showed that the protein tyrosine phosphatase (PTPase) inhibitors sodium orthovanadate and phenylarsine oxide (PAO) block the FcγRI-induced respiratory burst in interferon-γ- differentiated U937 cells (U937IF) while augmenting the FcγRI-induced tyrosine phosphorylation of cellular proteins. Herein we examine the effects of PTPase inhibitors on specific molecules involved in FcγRI signaling. We show that orthovanadate and PAO augmented the FcγRI-induced tyrosine phosphorylation of the adaptor protein CBL. CBL interactions with other phosphoproteins, among them SHC and CRKL, were also augmented in response to pretreatment with the PTPase inhibitors. SHC was tyrosine phosphorylated in response to FcγRI stimulation of U937IF cells and bound to the SH2 domain of GRB2 in a stimulation-dependent manner. In fusion protein pull-down experiments the interaction of SHC with the SH2 domain of GRB2 was increased in PTPase inhibitor pretreated U937IF cells in response to FcγRI stimulation. Our data support the hypothesis that a tyrosine dephosphorylation event is required for effective transmission of the FcγRI signal to result in activation of the myeloid respiratory burst response.
ASJC Scopus subject areas
- Cell Biology