c-Jun activating binding protein 1 binds to the IgA receptor and modulates protein levels of FcalphaRI and FcRgamma-chain.

The receptor for IgA, FcαRI or CD89, is expressed on myeloid cells and can trigger phagocytosis, tumor cell lysis, and release of inflammatory mediators. These functions critically depend on the associated FcR γ-chain; however, some biological functions, like receptor internalization, are solely mediated by FcαRI α-chain. Little is known as to how FcαRI regulates these processes and the FcαRI intracellular domain does not contain recognized signalling motifs. We searched for associating proteins and identified c-Jun activating binding protein 1 (JAB1) as a binding partner specifically for FcαRI. We found increased FcαRI surface expression after ectopic expression of JAB1 as well as diminished protein levels of total FcR γ-chain levels after JAB1 knock-down. These data functionally link JAB1 with controlling protein expression levels of FcαRI-FcR γ-chain protein complex.