A collagen-like glycoprotein of the extracellular matrix is the undegraded form of type VI collagen

Abstract

The 140 000-dalton collagenous glycoprotein (CGP) from calf aorta and ligament characterized by Gibson & Cleary (1982) [Gibson, M.A., & Cleary, E.G. (1982) Biochem. Biophys. Res. Commun. 105, 1288-1295] has been studied. In the electron microscope, rotary-shadowed CGP molecules appear similar to the dimers of type VI collagen (short-chain collagen, intima collagen) described by other authors [Furthmayr, H., Wiedemann, H., Timpl, R., Odermatt, E., & Engel, J. (1983) Biochem. J. 211, 303-311] except that they have larger globular domains. As shown by gel electrophoresis, pepsin treatment of CGP at 4 degrees C either before or after reduction releases polypeptide chains corresponding in size to those of type VI collagen. Electron microscopic examination shows that pepsin digestion of nonreduced CGP removes the outer globular domains, reduces the size of the inner ones, and separates the paired central strands. The residual structures look like type VI collagen dimers. When intact CGP is reduced, monomers with two large globular ends are obtained. Pepsin digestion of monomers removes most or all of both globular domains. In immunoblots, CGP and its pepsin-derived fragments react with antibodies directed against type VI collagen. The results indicate that type VI collagen is an integral component of CGP.

Molecular assembly, secretion, and matrix deposition of type VI collagen.

“…Type VI collagen from medium of cells cultured in the presence of ascorbic acid (Fig. 5 a) resembled images of the tissue forms of type VI collagen (15,24). Most of the structures were ~ 150 nm long and had a central, 60-nm-long rodlike region with two closely associated globules at each end.…”

“…The 140-kD component has therefore been thought to be the genuine type VI collagen (11,12,15,24). However, a larger polypeptide has also been noted in some type VI collagen preparations, and Trueb and Bornstein (21) presented evidence for a type VI procollagen chain of 250-kD.…”

“…One outstanding feature of both the pepsin fragments and the larger forms of type VI collagen is the extensive interchain disulfide cross-linking. It appears from chemical and morphological analyses of type VI collagen that it contains relatively short triple-helical domains, contributing one-third or less to the total mass of the protein (7,10,13,15,19).The molecular architecture (2, 7, 13, 15), the large amount of globular structure, and the extensive disulfide cross-linking in type VI collagen suggest that it is unique among collagens, but little is known about its biosynthesis, processing, and biological function. Type VI collagen is synthesized by fibroblasts and muscle cells in culture and is deposited into their extracellular matrix (l l, 13, 22, 24).…”

Distribution of type VI collagen expression in synovial tissue and cultured synoviocytes: relation to fibronectin expression.

“…Type VI collagen is also found in the blood vessel walls. This is not surprising because type VI collagen has been previously isolated from vascular connective tissue.5 10 In rheumatoid synovium type VI collagen is extensively deposited both in the interstitial connective tissue and along the lining of the synovial membrane, suggesting increased synthesis by the proliferating lining cells and by interstitial connective tissue cells. These findings suggest differences in the expression of type VI collagen between rheumatoid and normal synovium.…”

Collagen type VI in neural crest development: Distribution in situ and interaction with cells in vitro

“…The triple-helical collagenous portion of the molecule is relatively short and is flanked by extended noncollagenous domains, which after rotary shadowing appear as prominent globules. These terminal globules are thought to be important for the macromolecular assembly of the molecule (Furthmayr et al, 1983;von der Mark et al, 1984;Jander et al, 1984;Engvall et al, 1986;Kuo et al, 1989). Monomers of Col VI associate intracellularly to form disulfidestabilized tetramers which organize into linear polymeric complexes after secretion from the cell.…”