Fibronectin fibrillogenesis involves the heparin II binding domain of fibronectin.
Fibronectin matrix assembly is thought to involve binding interactions between the amino-terminal I1-5 repeats and the first type III repeat (III1). Here we report that a third site, located within the III12-14 repeats of the carboxyl-terminal heparin II domain of fibronectin, is also involved in fibrillogenesis. Heparin II fragments inhibited fibril formation and binding of 125I-labeled fibronectin and/or 70-kDa fragments to the cell surface, deoxycholate-insoluble matrix, and adsorbed 160-kDa cell adhesion fragments of fibronectin. The inhibitory effects of heparin II fragments were as large or up to 20 times larger than those of a 44-kDa fibronectin fragment containing the III1 repeat. Under physiological conditions, amino-terminal fragments of fibronectin containing the I1-5 repeats interacted preferentially with proteolytically derived heparin II fragments and a recombinant III12-14 peptide both in solution and in solid phase, indicating that matrix assembly may involve direct interactions between I1-5 and III12-14 repeats. Interactions between the I1-5 repeats and 160-kDa fragments containing the III12-14 and III1 repeats could be inhibited by >/= 90% by either an anti-III13-14 monoclonal antibody (mAb) (IST-2) or an anti-III1 mAb (9D2), suggesting that cooperative interactions between III12-14 and III1 repeats may also promote binding of the I1-5 repeats. Neither mAb IST-2 nor mAb 9D2, alone or in combination, inhibited binding of 125I-labeled 70-kDa fragments to cycloheximide-treated cells plated on the 160-kDa substrate, suggesting that additional I1-5 binding sites, independent of the III1 and III12-14 repeats, may be involved in fibrillogenesis.
Bultmann
H
H
Department of Pathology and Laboratory Medicine, University of Wisconsin Medical School, Madison, Wisconsin 53706, USA.
Santas
A J
AJ
Peters
D M
DM
D000906:Antibodies / Q000494:pharmacology; D001665:Binding Sites; D002448:Cell Adhesion; D002478:Cells, Cultured; D005109:Extracellular Matrix / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology; D005353:Fibronectins / Q000235:genetics / Q000378:metabolism*; D006493:Heparin / Q000378:metabolism; D006801:Humans; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid
D000906:Antibodies; D005353:Fibronectins; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; D006493:Heparin