Novel Cross-Talk between Three Cardiovascular Regulators: Thrombin Cleavage Fragment of Jagged1 Induces Fibroblast Growth Factor 1 Expression and Release

Abstract

Angiogenesis is controlled by several regulatory mechanisms, including the Notch and fibroblast growth factor (FGF) signaling pathways. FGF1, a prototype member of FGF family, lacks a signal peptide and is released through an endoplasmic reticulum-Golgi-independent mechanism. A soluble extracellular domain of the Notch ligand Jagged1 (sJ1) inhibits Notch signaling and induces FGF1 release. Thrombin, a key protease of the blood coagulation cascade and a potent inducer of angiogenesis, stimulates rapid FGF1 release through a mechanism dependent on the major thrombin receptor protease-activated receptor (PAR) 1. This study demonstrates that thrombin cleaves Jagged1 in its extracellular domain. The sJ1 form produced as a result of thrombin cleavage inhibits Notch-mediated CBF1/Suppressor of Hairless [(Su(H)]/Lag-1-dependent transcription and induces FGF1 expression and release. The overexpression of Jagged1 in PAR1 null cells results in a rapid thrombin-induced export of FGF1. These data demonstrate the existence of novel cross-talk between thrombin, FGF, and Notch signaling pathways, which play important roles in vascular formation and remodeling. INTRODUCTIONFibroblast growth factor (FGF) family members exhibit a variety of biological activities. During embryogenesis, they regulate mesoderm induction, neurulation, and formation of the circulatory and skeletal systems (Fallon et al., 1994;Friesel and Maciag, 1999). During postnatal development, they play a crucial role in angiogenesis, tissue regeneration, inflammation, and pathogenesis of some tumors (Christofori and Luef, 1997;Friesel and Maciag, 1999;Woolley et al., 2000;Javerzat et al., 2002;Okunieff et al., 2003). The biological effects of FGFs are mediated through the activation of four transmembrane phosphotyrosine kinase receptors (FGFR1-4) (McKeehan et al., 1998), with the participation of cell surface proteoglycans (Ornitz and Itoh, 2001), and consequently require FGF release. FGF1 is a potent proangiogenic factor, which supports the survival of endothelial cells in vitro, stimulates the growth of vessels, and enhances the repair of infarctic lesions in vivo (Sellke et al., 1996;Schumacher et al., 1998;Friesel and Maciag, 1999;Buehler et al., 2002). FGF1 lacks a signal peptide in its primary structure (Friesel and Maciag, 1999), and, similar to other signal peptide-less extracellular regulatory proteins, it undergoes nonclassical export (for review, see Prudovsky et al., 2003;Nickel, 2005;Prudovsky et al., 2008).Thrombin, the key protease of the blood coagulation cascade, induces the expression of several growth factors (Bassus et al., 2001;Cucina et al., 2002;Cao et al., 2006) and exhibits proangiogenic activity (Steinhoff et al., 2005). We recently demonstrated that thrombin, through activation of the protease-activated receptor (PAR) 1, rapidly induces FGF1 expression and its release under nonstress conditions, revealing an interplay between thrombin signaling and nonclassical FGF1 release (Duarte et al., 2006). PAR1 is activated through the proteolyti...

Notch Signaling Activation Is Associated with Patient Mortality and Increased FGF1-Mediated Invasion in Squamous Cell Carcinoma of the Oral Cavity

“…Although FGF1 is not a classical target of Notch transcription, ours is not the first evidence of a regulatory relationship between Notch and FGF signaling. In several previous studies, the constitutive activation of canonical (CBF1 dependent) Notch-mediated transcription was found to suppress FGF1 expression, while inhibition of CBF1 and its coactivator MAML induced FGF1 expression and transport into the extracellular compartment (31)(32)(33). Surprisingly, we observed evidence of the opposite, as in vitro Notch activation increased FGF1 transcript levels and produced an FGF1-dependent invasive phenotype.…”

Phosphatidylserine externalization and membrane blebbing are involved in the nonclassical export of FGF1

“…Recombinant FGF1:HA adenovirus was produced, purified, and titered as described (Duarte et al, 2008). Briefly, CRE8 cells were transfected with SfiI -digested pAdlox-derived constructs, and infected with the ψ5 virus.…”

Characterization of the chemotactic and mitogenic response of SMCs to PDGF‐BB and FGF‐2 in fibrin hydrogels

“…Recent evidence has demonstrated that fibrinogen alone can augment the proliferation rates of specific carcinoma cells and endothelial cells in response to FGF‐2, and that this appears to be attributable to fibrinogen‐FGF‐2 binding 37, 38. Similarly, thrombin promotes endogenous FGF‐1 expression in endothelial cells39 and FGF‐2 in SMCs,40 upregulates VEGF expression in SMCs via endogenous PDGF and FGF‐2 activity,41 can itself be a significant SMC mitogen and chemoattractant in vitro at concentrations of 0.5 U/mL in a process likely involving FGF‐2 release and FGFR‐1 transactivation,42 and can significantly impact fibrin gel structural and mechanical properties which could affect cellular behavior 43. While thrombin can affect SMC proliferation rates in 2D culture systems, the role of thrombin in modulating SMC proliferation in 3D culture systems is less established.…”