Functional comparison of high and low molecular weight basic fibroblast growth factors

Acid-electrolyzed functional water (FW) is obtained through the electrolysis of sodium chloride solution. Stimulation of the human fibroblastic cell line HeLa by FW led to the augmented secretion of basic fibroblast growth factor (bFGF). Immunoprecipitation followed by Western blot analysis revealed that both high and low molecular weight isoforms of bFGF were secreted in response to FW treatment. To explore intracellular bFGF localization, a cell fractionation assay was performed. Despite the presence of nuclear localization signals within the N-terminal portion of these proteins, the high molecular weight isoforms (34, 24, 22.5, and 21 kDa) were localized in the cytoplasm. FW stimulation drastically reduced the amount of intracytoplasmically localized isoforms, and the 34-kDa isoform was found to localize in a DNase-sensitive fraction, suggesting a weak nuclear attachment. By contrast, the 24-kDa isoform remained in the nucleus even after FW stimulation. Functional differences between the 34- and 18-kDa isoforms were examined further. Chinese hamster ovary cells were transfected with expression plasmids for each isoform. By treating each transfectant with FW, both isoforms were secreted successfully into the culture supernatants. Stimulation of HeLa cells with these supernatants resulted in the augmented secretion of vascular endothelial growth factor (VEGF). To further confirm the functionality of these isoforms, an in vitro transcription/translation reaction was performed; both of the isoforms induced VEGF secretion from HeLa cells. Taken together, these results indicate that the high molecular weight 34-kDa isoform and low molecular weight 18-kDa mature bFGF isoform have identical roles in VEGF induction.