| Abstract: |
The zeta-subunit is a component of the Fc-gamma receptor of natural killer cells (Fc-gamma-RIII or CD16), as well as the multimeric T-cell receptor/CD3 complex, and is required for assembly of both native receptors. The role of the zeta-subunit in human Fc-gamma-RIIIA assembly differs from its role in T-cell receptor/CD3 complex assembly. The transmembrane domain of the Fc-gamma-RIIIA alpha-subunit forms noncovalent interactions with the comparable domain of the zeta-subunit and is sufficient for surface expression of the Fc-gamma-RIIIA complex. In the absence of these interactions, sequences in the transmembrane domain of the Fc-gamma-RIIIA alpha-subunit signal its degradation. Leu-46, present in the transmembrane domain of the human zeta-subunit, is important for assembly with the Fc-gamma-RIIIA alpha-subunit. Substitution of this leucine with an isoleucine, as found in the mouse zeta-subunit, significantly reduces this interaction. In contrast, the mouse and human zeta-subunits interact with the pentameric T-cell receptor/CD3 complex, resulting in surface expression of this receptor. |
