Molecular Characterization Of The Dimer Formation Of Fc Alpha/Mu Receptor (Cd351)

Fc alpha/mu R (CD351) is an Fc receptor for both IgA and IgM and forms an atypical dimer that is resistant to reduction by 2-mercaptoethanol or boiling. We previously demonstrated that the cytoplasmic portion of Fc alpha/mu R is required for dimer formation and for its efficient cell-surface expression. However, the biochemical nature of these phenomena has not been determined. By using a BW5147 mouse cell line expressing deletion mutants of the cytoplasmic region of Fc alpha/mu R, we found that the region spanning amino acids 504-523 was required for efficient cell-surface expression, whereas the region spanning amino acids 481-490 was required for dimmer formation. Immunoblotting analyses of transfectants simultaneously expressing Flag-tagged Fc alpha/mu R and hemagglutinin-tagged Fc alpha/mu R suggested that Fc alpha/mu R does not form homodimers. Instead, our data suggest that Fc alpha/mu R forms heterodimers with an as-yet-unknown molecule with a molecular weight of 60-70 kDa. (C) 2013 Elsevier Ltd. All rights reserved.