Thrombin cleaves the high molecular weight forms of basic fibroblast growth factor (FGF-2): a novel mechanism for the control of FGF-2 and thrombin activity.

The fgf-2 gene encodes low molecular weight (LMW, 18 kDa) and high molecular weight (HMW, 22-24 kDa) forms that originate from alternative translation of a single mRNA and exhibit diverse biological functions. HMW fibroblast growth factor-2 (FGF-2) inhibits cell migration and induces cell transformation or growth arrest in a cell type- and dose-dependent fashion. Conversely, LMW FGF-2 upregulates both cell proliferation and migration in most cell types. Although transcriptional and translational regulation of HMW and LMW FGF-2 has been extensively investigated, little is known about post-translational control of their relative expression. Here we report that thrombin, a key coagulation factor and inflammatory mediator, cleaves HMW FGF-2 into an LMW FGF-2-like form that stimulates endothelial cell migration and proliferation. The effect of thrombin on these cell functions requires HMW FGF-2 cleavage. This post-translational control mechanism adds a novel level of complexity to the regulation of FGF-2, and links the activities of thrombin and FGF-2 in patho-physiological processes in which both molecules are expressed.