CD146: biosynthesis and production of a soluble form in human cultured endothelial cells

We previously identified the S-Endo 1-associated antigen (CD146), an endothelial member of the immunoglobulin superfamily with a characteristic V-V-C2-C2-C2 Ig domain structure. In cultured human endothelial cells, we investigated its biosynthesis by immunoprecipitation and pulse-chase labeling. CD146 was synthesized as a 100 kDa precursor form, which was processed into a 120 kDa mature form. In the culture media of endothelial cells, we observed a CD146 soluble form that was about 10 kDa smaller than cell-associated CD146. In parallel with soluble forms of other members of the immunoglobulin superfamily, soluble CD146 could modulate and control the functions of the molecule.