Identification of a Novel Integrin α6β1 Binding Site in the Angiogenic Inducer CCN1 (CYR61)

Abstract

The angiogenic inducer CCN1 (cysteine-rich 61, CYR61), a secreted matricellular protein of the CCN family, is a ligand of multiple integrins, including ␣ 6 ␤ 1 . Previous studies have shown that CCN1 interaction with integrin ␣ 6 ␤ 1 mediates adhesion of fibroblasts, endothelial cells, and smooth muscle cells, as well as migration of smooth muscle cells. Recently, we have reported that CCN1-induced tubule formation of unactivated endothelial cells is also mediated through integrin ␣ 6 ␤ 1 . In this study, we demonstrate that human skin fibroblasts adhere specifically to the T1 sequence (GQKCIVQTTSWSQCSKS) within domain III of CCN1, and this process is blocked by anti-␣ 6 and anti-␤ 1 monoclonal antibodies. Alanine substitution mutagenesis of the T1 sequence further defines the sequence TTSWSQC-SKS as the critical determinant for mediating ␣ 6 ␤ 1 -dependent adhesion. Soluble T1 peptide specifically inhibits fibroblast adhesion to CCN1 in a dose-dependent manner. Furthermore, T1 also inhibits cell adhesion to other ␣ 6 ␤ 1 ligands, including CCN2 (CTGF), CCN3 (NOV), and laminin, but not to ligands of other integrins. In addition, T1 specifically inhibits ␣ 6 ␤ 1 -dependent tubule formation of unactivated endothelial cells in a CCN1-containing collagen gel matrix. To confirm that T1 binds integrin ␣ 6 ␤ 1 directly, we perform affinity chromatography and show that integrin ␣ 6 ␤ 1 is isolated from an octylglucoside extract of fibroblasts on T1-coupled Affi-gel. Taken together, these findings define the T1 sequence in CCN1 as a novel binding motif for integrin ␣ 6 ␤ 1 , providing the basis for the development of peptide mimetics to examine the functional role of ␣ 6 ␤ 1 in angiogenesis.

Polarized expression of integrin β1 in diencephalic roof plate during chick development, a possible receptor for SCO‐spondin

“…For instance, the TSR domain of thrombospondin-1 is an integrin ligand pan-␤1 specific, and this interaction is crucial for its function (Calzada et al, 2004;Short et al, 2005). Also, the angiogenic inducer CCN1 binds integrin ␣6␤1 by a TSR domain (Leu et al, 2003). Given its several TSR motifs, we speculate that SCO-spondin has the ability to bind simultaneously several molecules of integrin ␤1 to potentially exert different roles.…”

“…For instance, mice carrying mutations in integrin ␣6 and those lacking integrin ␤1 show defects in the anchorage of radial glial processes at the meningeal basement membrane in the cerebral and cerebellar cortex (Georges-Labouesse et al, 1998;Graus-Porta et al, 2001;Milner and Campbell, 2002;Belvindrah et al, 2007). On the other hand, integrins interact with the TSR domain of several members of the TSR superfamily (Leu et al, 2003;Calzada et al, 2004;Short et al, 2005). Remarkably, activity-blocking antibodies against integrin ␤1 inhibited the ability of the TSR domains of SCO-spondin to induce neurite outgrowth in vitro (Bamdad et al, 2004).…”

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).…”

New molecular insights into peripheral T cell lymphomas

“…In particular, an analysis of ours (10) might explain the dissemination pattern of PTCL-NOSs, which involves frequent extranodal sites and bone marrow and spreads to peripheral blood, because it demonstrates the upregulation of the FN1, LAMB1, COL1A2, COL3A1, COL4A1, COL4A2, and COL12A1 genes, which promote local invasion and metastasis in different types of human cancers (33)(34)(35). In addition, our analysis revealed the deregulation of genes involved in apoptosis (e.g., MOAP1, ING3, GADD45A and GADD45B) (36)(37)(38)(39)(40)(41)(42) and chemo-resistance (e.g., CYR61 and NNMT) (33)(34)(35)(43)(44)(45)(46)(47)(48)(49)(50)(51)(52)(53), which may be responsible for the poor response to conventional chemotherapy.…”