Mitogenic effects of coagulation factor XII and factor XIIa on HepG2 cells.

Abstract

The structure of coagulation factor XII (Hageman factor), inferred from its DNA sequence, includes two epidermal growth factor (EGF)-homologous domains in its amino-terminal region. This suggests that factor XII may exhibit EGF-like activities. Reciprocal antigenic crossreactivity between factor XII and EGF was shown by exposing purified human factor XII or mouse EGF to anti-mouse EGF or anti-human factor XII. Western blot analysis showed that anti-mouse EGF recognized intact factor XII at 80 kDa. Together, these results suggest that the EGF-homologous domains are accessible for anti-EGF binding in native factor XII. To determine whether factor XII has mitogenic activity, HepG2 or L cells (104 cells per well) were grown in serum-free medium in the presence or absence of factor XII or kaolin-activated factor XII (factor XIIa). Both factors XII and XIIa (6.0 jug/ml) enhanced cell proliferation by --2-fold (P < 0.001 and P < 0.005, respectively). In contrast, L cells, which are not EGF target cells, were not affected by either factor XII or factor XIIa. Various doses of factor XII enhanced cell proliferation, PH~thymidine incorporation, and [3H]leucine incorporation in HepG2 cells cultured under the same conditions. These data indicate that factor XII, like EGF, is a mitogen for HepG2 cells and suggest a possible autocrine role in the liver.Factor XII is a procoagulant, found in normal plasma, that participates directly or indirectly in activation of the intrinsic clotting pathway, factor VII, fibrinolysis, and the reninangiotensin and kallikrein-kinin systems (1-3). The structure of factor XII, inferred from its DNA and amino acid sequences, includes two epidermal growth factor (EGF)-homologous domains in the amino-terminal region (4-7). This suggests that factor XII may mimic EGF and act as a growth factor, Hepatocytes and hepatoma cells are target cells for EGF and hepatocytes synthesize factor XII, raising the possibility that factor XII may act as an autocrine or paracrine hepatocyte growth factor, perhaps in a feedback process, to regulate liver growth or productive activity under physiologic conditions. EGF is a well-characterized mitogen that stimulates the proliferation of numerous cell types in vitro and of epithelial cells in vivo. The EGF receptor is detectable on a large variety of cell types, mostly epithelial. Available evidence indicates that the EGF receptor mediates the biological signals of EGF and possibly those of two EGF-like growth factors-namely, transforming growth factor a and the vaccinia virus growth factor (8), which have amino acid sequences homologous to EGF (9). Since the putative tertiary structure of factor XII includes domains that appear to be homologous to EGF (4-7), we examined whether factor XII might have growth factor activity as well.Growth factors can elicit numerous responses in target cells. Among these are (i) early cellular responses, such as increased protein synthesis; (ii) later cellular responses, such as increased DNA synthesis; and (iii) the definitive ce...

The structure of the FnI-EGF-like tandem domain of coagulation factor XII solved using SIRAS

“…The putative interaction of FXII with the EGF receptor has been implicated in stimulating the division of cells (Schmeidler-Sapiro et al, 1991;Gordon et al, 1996) with EGF and TGFa (Garrett et al, 2002;Ogiso et al, 2002) served as templates to dock FXII-FnIE to EGFR. A superposition of the FXIIFnIE structure onto that of EGF bound to EGFR showed that the FnI domain overlaps with domain I of EGFR (Fig.…”

“…The binding of FXII to the surface of these cells results in the activation of several kinase signalling pathways, leading to mitosis. Some studies have attributed this to interaction between one of the EGF-like domains of FXII and the EGF receptor (EGFR) on these cells (Schmeidler-Sapiro et al, 1991;Gordon et al, 1996). An indirect activation model has also been proposed in which FXII binds to the uPA receptor via its FnII domain, after which a multiple receptor complex is formed (LaRusch et al, 2010).…”

“…Extensive research has been performed on the type of surfaces and molecules that activate FXII in vitro, leading to initiation of the intrinsic coagulation pathway and the kallikreinkinin system (Griep et al, 1986;Tazi et al, 1992;Matata et al, 1996). The search for a physiological function of FXII has resulted in a number of possible roles, such as the induction of mitosis (Schmeidler-Sapiro et al, 1991;Gordon et al, 1996), angiogenesis (LaRusch et al, 2010), inflammation reactions (Jansen et al, 1996) and complement activation (Ghebrehiwet et al, 1981). Additionally, FXII has been found to have an important role in thrombus formation (Renné et al, 2005;Meijden et al, 2009).…”

The proteinase activated receptor-2 (PAR-2) mediates mitogenic responses in human vascular endothelial cells.

“…Recently, the concept that serine proteases may have direct cellular effects has also gained recognition. For example, plasmin and coagulation Factor XIIa are known to activate directly certain cell types (18,19). Likewise, thrombin displays profound actions at the cellular level (20) that are more completely characterized (21)(22)(23)(24).…”

Heparan Sulfate Proteoglycans Mediate Factor XIIa Binding to the Cell Surface

“…The ability of FXII/FXIIa to stimulate proliferation of alveolar type II cells, aortic smooth muscle cells, hepatocytes, and endothelial cells has been described previously (43,44). Furthermore, FXII/FXIIa-induced endothelial cell proliferation was shown to be physiologically relevant because it had a profound impact on angiogenesis (45). Thus, HS-dependent sequestration of FXII/FXIIa to the cell surface may have important (but not related to its procoagulant activities) consequences in vivo.…”