What are Fc fusion proteins and why are they used?
Cytokines and particularly the extra cellular domains of cytokine receptors may be expressed as Fc fusion proteins. The Fc region comprises the hinge region and the CH2 and CH3 domains of human IgG1. The Fc domain facilitates the dimerisation of the fusion protein via the formation of disulfide bonds. This in turn will greatly increase the neutralising ability of the protein relative to monomeric receptor forms. Additionally, Fc fusion proteins are known to exhibit increased half-life in vivo. Expression of an Fc fusion protein can increase the binding affinity of particular receptors relative to that of the soluble monomer. This provides the receptor-Fc dimer a number of advantages over the corresponding monomeric receptor equivalents (e.g. soluble Interleukin receptor monomers). Advantages include increased protein half-life, increased ligand binding affinity, and minimising the natural membrane bound receptor complexes.
