The Angiogenic Factors Cyr61 and Connective Tissue Growth Factor Induce Adhesive Signaling in Primary Human Skin Fibroblasts

Abstract

The angiogenic inducers cysteine-rich angiogenic protein 61 (Cyr61) and connective tissue growth factor (CTGF) are structurally related, extracellular matrixassociated heparin-binding proteins. Both can stimulate chemotaxis and promote proliferation in endothelial cells and fibroblasts in culture and induce neovascularization in vivo. Encoded by inducible immediate early genes, Cyr61 and CTGF are synthesized upon growth factor stimulation in cultured fibroblasts and during cutaneous wound healing in dermal fibroblasts. Recently, we have shown that adhesion of primary human fibroblasts to immobilized Cyr61 is mediated through integrin ␣ 6 ␤ 1 and cell surface heparan sulfate proteoglycans (HSPGs) (Chen, N., Chen, C.-C., and Lau, L.F. (2000) J. Biol. Chem. 275, 24953-24961), providing the first demonstration of an absolute requirement for HSPGs in integrin-mediated cell attachment. We show in this study that CTGF also mediates fibroblast adhesion through the same mechanism and demonstrate that fibroblasts adhesion to immobilized Cyr61 or CTGF induces distinct adhesive signaling responses consistent with their biological activities. Compared with fibroblast adhesion to fibronectin, laminin, or type I collagen, cell adhesion to Cyr61 or CTGF induces 1) more extensive and prolonged formation of filopodia and lamellipodia, concomitant with formation of integrin ␣ 6 ␤ 1 -containing focal complexes localized at leading edges of pseudopods; 2) activation of intracellular signaling molecules including focal adhesion kinase, paxillin, and Rac with similar rapid kinetics; 3) sustained activation of p42/p44 MAPKs lasting for at least 9 h; and 4) prolonged gene expression changes including up-regulation of MMP-1 (collagenase-1) and MMP-3 (stromelysin-1) mRNAs and proteins sustained for at least 24 h. Together, these results establish Cyr61 and CTGF as bona fide adhesive substrates with specific signaling capabilities, provide a molecular basis for their activities in fibroblasts through integrin ␣ 6 ␤ 1 and HSPG-mediated signaling during attachment and indicate that these proteins may function in matrix remodeling through the activation of metalloproteinases during angiogenesis and wound healing.

The contribution of adhesion signaling to lactogenesis

“…CTGF/CCN2 enhanced the levels of β1 integrin on the surface of the cells (Weston et al 2003;Morrison et al 2010) and contributed to the adhesion via binding to α6β1 integrin, a common laminin receptor (Chen et al 2001;Leu et al 2003;Tong and Brigstock 2006). CTGF/CCN2 also enhanced binding of cells to the common fibronectin receptor, α 5 β1 integrin (Frazier et al 1996;Blom et al 2001;Weston et al 2003).…”

Suppression of Cell Proliferation and Signaling Transduction by Connective Tissue Growth Factor in Non–Small Cell Lung Cancer Cells

“…1-3). The CCN proteins are multifunctional and are involved in cell adhesion, angiogenesis, cell differentiation, and tumorigenesis (4)(5)(6)(7)(8). CTGF was first identified as a mitogen from human umbilical vein endothelial cells, and expression of CTGF is inducible by tumor growth factor-h in fibroblasts (9).…”

WISP-1 attenuates p53-mediated apoptosis in response to DNA damage through activation of the Akt kinase

“…Two members of the CCN family, CTGF and Cyr61, signal through the integrin receptors ␣ v ␤ 3 , ␣ IIb ␤ 3 , ␣ v ␤ 5 , and ␣ 6 ␤ 1 (Kireeva et al 1998;Babic et al 1999;Jedsadayanmata et al 1999;Chen et al 2001;Grzeszkiewicz et al 2001). Integrin receptors have been shown to play a role in cell migration and proliferation, and can affect cancer cell invasion and growth (Giancotti and Ruoslahti 1999;Ruoslahti 1999).…”