Primary chondrocytes from quail embryo epiphysis (quail epiphyseal chondrocytes, QEC) can grow either in suspension or in monolayer. In this study, the adhesion of QEC to collagen II was used as a model to study the regulation of the ligand-binding activity of integrin receptors that allows these cells to undergo a rapid transition from suspension to an adherent state. Preincubation of suspension QEC (QECSP) with the disintegrin echistatin increased by 40% their adhesion to collagen II. An inverse relationship between immobilized collagen density and echistatininduced increase of chondrocyte adhesion was observed, thus suggesting that the disintegrin acts by increasing the ligand-binding affinity of collagen receptor(s). Further, echistatin activity does not appear to depend upon a direct binding of the disintegrin to collagen receptor(s). In fact, immobilized anti-beta1 antibodies, but not immobilized echistatin, served as effective binding sites for QECSP. Echistatin failed to stimulate chondrocyte adhesion to collagen in the presence of metabolic inhibitors, while an activating anti-beta1 antibody was still effective. Thus, echistatin may promote cell adhesion by interfering with energy-dependent signals that keep the collagen receptor(s) in a low-affinity state. Adhesion experiments performed in the presence of pharmacological inhibitors indicate that phosphatidyl inositol 3-kinase (PI3-K)/protein kinase C (PKC) and protein kinase A (PKA) pathways may transmit opposing signals on chondrocyte adhesion, and that collagen receptors are kept in a low-affinity state by PI3-kinase/PKC signalling. Since echistatin is a high-affinity ligand for alfavbeta3 integrin, the effect of the function-blocking anti-alfavbeta3 antibody LM609 was investigated. Like echistatin, LM609 stimulated chondrocyte adhesion to collagen and failed to support their attachment. Therefore, our data suggest that alfavbeta3-antagonists might regulate the binding activity of the beta1 collagen receptor, which in turn leads to the rapid transition of chondrocytes fromsuspensi on to an adherent state.
Modulation of chondrocyte adhesion to collagen by echistatin / Belisario, MARIA ANTONIETTA; Tafuri, Simona; Pontarelli, Gianfranco; Staiano, Norma; Gionti, Elisa. - In: EUROPEAN JOURNAL OF CELL BIOLOGY. - ISSN 0171-9335. - STAMPA. - 84:(2005), pp. 833-842.
Modulation of chondrocyte adhesion to collagen by echistatin.
BELISARIO, MARIA ANTONIETTA;TAFURI, SIMONA;PONTARELLI, GIANFRANCO;STAIANO, NORMA;GIONTI, ELISA
2005
Abstract
Primary chondrocytes from quail embryo epiphysis (quail epiphyseal chondrocytes, QEC) can grow either in suspension or in monolayer. In this study, the adhesion of QEC to collagen II was used as a model to study the regulation of the ligand-binding activity of integrin receptors that allows these cells to undergo a rapid transition from suspension to an adherent state. Preincubation of suspension QEC (QECSP) with the disintegrin echistatin increased by 40% their adhesion to collagen II. An inverse relationship between immobilized collagen density and echistatininduced increase of chondrocyte adhesion was observed, thus suggesting that the disintegrin acts by increasing the ligand-binding affinity of collagen receptor(s). Further, echistatin activity does not appear to depend upon a direct binding of the disintegrin to collagen receptor(s). In fact, immobilized anti-beta1 antibodies, but not immobilized echistatin, served as effective binding sites for QECSP. Echistatin failed to stimulate chondrocyte adhesion to collagen in the presence of metabolic inhibitors, while an activating anti-beta1 antibody was still effective. Thus, echistatin may promote cell adhesion by interfering with energy-dependent signals that keep the collagen receptor(s) in a low-affinity state. Adhesion experiments performed in the presence of pharmacological inhibitors indicate that phosphatidyl inositol 3-kinase (PI3-K)/protein kinase C (PKC) and protein kinase A (PKA) pathways may transmit opposing signals on chondrocyte adhesion, and that collagen receptors are kept in a low-affinity state by PI3-kinase/PKC signalling. Since echistatin is a high-affinity ligand for alfavbeta3 integrin, the effect of the function-blocking anti-alfavbeta3 antibody LM609 was investigated. Like echistatin, LM609 stimulated chondrocyte adhesion to collagen and failed to support their attachment. Therefore, our data suggest that alfavbeta3-antagonists might regulate the binding activity of the beta1 collagen receptor, which in turn leads to the rapid transition of chondrocytes fromsuspensi on to an adherent state.File | Dimensione | Formato | |
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