Production and purification of recombinant long protein isoforms of FGF11 subfamily

The FGF11 subfamily of FGF proteins also known as fibroblast growth factor homologous factors (FHFs) includes four proteins, FGF11, FGF12, FGF13, and FGF14. They are mainly expressed in excitable cells but are also present in fibroblasts or osteoclasts, where their function is much less understood. Each FGF11-14 protein has at least two isoforms formed by alternative splicing, which differ in both cellular localization and function. Until recently, only the short isoforms had been efficiently produced and purified in recombinant form. Here, we developed a protocol to produce in the bacterial expression system and efficiently purify the long "a" isoforms of FGF11, FGF12, FGF13 and FGF14. In addition, we characterized their biophysical and biological properties, demonstrating that they activate downstream signaling and, unlike short "b" isoforms, induce cell proliferation.