Generation of aminoterminally truncated, stable types of bioactive bovine and porcine fibroblast growth factor 4 in E scherichia coli

Fibroblast growth factor 4 ( FGF 4) is a crucial growth factor for the development of mammalian embryos. We previously produced hexahistidine‐tagged, bovine and porcine FGF 4 ( P ro 32 to L eu 206 ) proteins without a secretory signal peptide at the aminoterminus in E scherichia coli . Here, we found that these were unstable; site‐specific cleavage between S er 54 and L eu 55 in both FGF 4 derivatives was identified. In order to generate stable FGF 4 derivatives and to investigate their biological activities, aminoterminally truncated and hexahistidine‐tagged bovine and porcine FGF 4 ( L eu 55 to L eu 206 ) proteins, termed H isb FGF 4 L and H isp FGF 4 L , respectively, were produced in E . coli . These FGF 4 derivatives were sufficiently stable and exerted mitogenic activities in fibroblasts. Treatment with the FGF 4 derivatives promoted the phosphorylation of ERK 1/2, which are crucial kinases in the FGF signaling pathway. In the presence of PD 173074, an FGF receptor inhibitor, the phosphorylation of ERK 1/2 was inhibited and resulted in abolition of the growth‐promoting activity of FGF 4 derivatives. Taken together, we demonstrate that H isb FGF 4 L and H isp FGF 4 L are capable of promoting the proliferation of bovine‐ and porcine‐derived cells, respectively, via an authentic FGF signaling pathway. These FGF 4 derivatives may be applicable for dissecting the roles of FGF 4 during embryogenesis in cattle and pigs.