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Structural and functional comparison of type IX collagen-proteoglycan from chicken cartilage and vitreous humor.

1991; Elsevier BV; Volume: 266; Issue: 8 Linguagem: Inglês

10.1016/s0021-9258(19)67713-6

1083-351X

Randolph G. Brewton, David W. Wright, Richard Mayne,

Osteoarthritis Treatment and Mechanisms

Type IX collagen-proteoglycan is a major component of hyaline cartilages where it is located on the surface of the collagen fibrils so that a collagenous domain of the molecule (called COL3) and a non-collagenous domain (called NC4) project at periodic distances away from the surface of the fibril.Type IX collagen-proteoglycan is also present on the surface of the collagen fibrils of the adult chicken vitreous but, unlike cartilage, lacks the NC4 domain and possesses a very long chondroitin sulfate chain which provides an extensive coat to the fibril.A monoclonal antibody (called 4D6) is described which will distinguish cartilage from vitreous type IX collagen.To form the epitope for 4D6 two peptides called C2 and C5 derived, respectively, from the al(1X) and a3(IX) chains are required.Further analysis shows that specificity for 4D6 resides only in the C2 peptide from cartilage and not in C5.These results are entirely consistent with recent evidence that there are two promoters for transcription of the al(1X) chain which will result in an al(1X) chain in which the NC4 domain is either present or absent and that expression of these two promoters has tissue specificity (Nishimura, I., Muragaki, Y., and Olsen, B. R. (1989) J. Biol. Chern. 264, 20033-20041). In addition, the function of type IX collagen in cartilage and vitreous may differ with the long chondroitin sulfate chains of vitreous type IX collagen being responsible for the gel-like matrix of this tissue.Considerable progress has recently been made in understanding the structure and potential functions of type IX collagen in hyaline cartilages (reviewed in Refs. 1 and 2).Electron microscopic observations of isolated collagen fibrils after rotary shadowing show that type IX collagen is located on the surface of the fibrils in a highly ordered array (3,4).A collagenous domain of the molecule (called COL3) projects periodically from the surface of the fibril and, at the end of this domain, a prominent knob is always visualized.This knob is called the NC4 domain (1) and is derived largely from the amino terminus of the al(1X) chain with much smaller contributions from the a2(IX) and a3(IX) chains (2, 5 ) .The interaction between type IX collagen and type I1 collagen on