FcγRIII, synonymously also referred to CD16, is a type III Fcγ receptor which has other two identified members: a high-affinity receptor FcγRI (CD64) and a low-affinity one FcγRII (CD32). This transmembrane protein, FcγRIII, contains two extracellular immunoglobulin (Ig)-like domains with low-affinity for IgG. It is responsible for antibody-dependent cellular cytotoxicity. FcγRIII is expressed on large granular lymphocytes of both nature killer (NK)- and T-cell types. There are two different isoforms of it in humans named FcγRIIIa and FcγRIIIb, sharing 96% sequence identity in extracellular Ig binding regions. FcγRIIIa is a transmembrane receptor found on macrophages, mast and NK cells. FcγRIIIb is expressed exclusively on neutrophils and functions as the only Fc receptor anchored via a glycosyl-phosphatidylinositol (GPI) linker to the cell membrane.
MET, also known as c-MET or HGFR (Hepatocyte growth factor receptor), is a transmembrane tyrosine kinase receptor that is encoded in humans by the MET gene. This receptor in charge of tyrosine-kinase activity is mapped at the chromosome 7q31.2 with 1408 amino acids. MET and its ligand HGF/SF (Hepatocyte growth factor/Scatter factor) are expressed in many tissues, principally in epithelial and mesenchymal origin cells, respectively. After binding to ligands, this tyrosine-protein kinase is rapidly internalized, polyubiquitinated and then degraded in a proteasome-dependent manner. MET is over-expressed in numerous types of neoplasms, such as tumors of the kidney, pancreas, thyroid and osteosarcoma. And it is reported that various mutations of MET gene are correlated with papillary renal carcinomas.