Serine/threonine phosphorylation of the γ-subunit after activation of the high-affinity Fc receptor for immunoglobulin G

D. L. Durden, H. Rosen, J. A. Cooper

Research output: Contribution to journalArticle

25 Scopus citations

Abstract

In this report we show that interferon γ treatment of U937 cells induces increased expression of the γ-subunit of the high-affinity Fc receptor for IgG (FcγRI). Interferon treatment results in a 10-old increased expression of the γ-subunit and induces expression of a phosphorylated form (γ1). The increased expression of the γ subunit correlates with its ability to transmit a signal via FcγR, as measured by activation of the respiratory burst using insoluble immune complexes. During FcγR activation, a mobility shift occurs in the phosphorylated form of this γ1-subunit. Phospho-amino acid analysis demonstrates that this γ1 subunit is threonine phosphorylated in resting differentiated U937 cells and becomes predominantly serine phosphorylated on Fc receptor activation. The mobility shift in the γ-subunit can be induced by treating U937 cells with phorbol 12-myristate 13-acetate or by monoclonal antibody cross-linking of FcγRI. Hence the γ-subunit is serine phosphorylated in response to FcγRI and protein kinase C activation. Therefore the γ-subunit, initially described as a subunit of FcγRI, now appears to be involved in signal transduction via FcγRI. The data also suggest that the γ-subunit, in contrast with the ζ-subunit of the T-cell receptor-CD3 complex, is a substrate for serine/threonine kinase(s) in the cell. The serine phosphorylation of the γ-subunit suggests a divergence of structure and function between the γ-subunit and its homologue, the ζ-subunit of the T-cell receptor. Phosphorylation of the γ-subunit on serine may play some regulatory role in FcγRI signal transduction in myeloid cells.

Original languageEnglish (US)
Pages (from-to)569-577
Number of pages9
JournalBiochemical Journal
Volume299
Issue number2
DOIs
StatePublished - 1994

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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