Large and small splice variants of collagen XII: differential expression and ligand binding.

Abstract

Abstract. Collagen XII has a short collagenous tail and a very large, three-armed NC3 domain consisting primarily of fibronectin type III repeats. Differential splicing within this domain gives rise to a large (320 kD) and a small (220 kD) subunit; the large but not the small can carry glycosaminoglycan. To investigate whether collagen XII variants have distinct expression patterns and functions, we generated antibody and cDNA probes specific for the alternatively spliced domain. We report here that the large variant has a more restricted expression in embryonic tissue than the small. For example, whereas the small variant is widespread in the dermis, the large is limited to the base of feather buds. Distinct proportions of mRNA for the two variants were detected depending on the tissue. Monoclonal antibodies allowed us to separate collagen XII variants, and to show that homo-and heterotrimers exist. Collagen XII variants differ in ligand binding. Small subunits interact weakly with heparin via their COOH-terminal domain. Large subunits have additional, stronger heparin-binding site(s) in their NH2-terminal extra domain. In vivo, both large and small collagen XII are associated with interstitial collagen. Here we show biochemically and ultrastructurally that collagen XII can be incorporated into collagen I fibrils when it is present during, but not after, fibril formation. Removal of the collagenous domain of collagen XII reduces its coprecipitation with collagen I. Our results indicate that collagen XII is specifically associated with fibrillar collagen, and that the large variant has binding sites for extracellular ligands not present in the small variant.group of fibril-associated collagens with interrupted triple helices (FACIT; types IX, XII, XIV) 1 has recently been discovered (for review see Mayne and Brewton, 1993;Shaw and Olsen, 1991;Van der Rest et al., 1990). The prototype FACIT is collagen IX, a heterotrimeric molecule with four noncoUagenous (NC1 to NC4) and three triple-helical domains (Col1 to Col3) (Ninomiya and Olsen, 1984). The et2(IX) chain carries chondroitin sulfate on the NC3 domain (McCormick et al., 1987). Collagen IX is covalently bound to the surface of collagen II fibrils in cartilage (Vaughan et al., 1988;Wu et al., 1992). Its function might be to regulate the diameter of collagen II fibrils, and to link them to other collagen fibrils, extraDrs. Koch, Trueb, and Chiquet's present address is M. E.

Mechanoregulation of gene expression in fibroblasts

“…When cells were pretreated with cytochalasin-B, an actin depolymerizing drug, and latrunculin A, an actin cytoskeleton disrupting drug, the stretching-induced tenascin-C mRNA expression was abolished, indicating that an intact cytoskeleton is required for stretching-induced tenascin-C mRNA expression (Chiquet et al, 2003;Sarasa-Renedo and Chiquet, 2005). Collagen XII has an expression pattern similar to that of tenascin-C and has been shown to co-assemble with collagen I during fibril formation (Koch et al, 1995). A mechanoresponsive control element was also localized in the collagen XII gene (Chiquet et al, 1998).…”

Primary structure of the long and short splice variants of mouse collagen XII and their tissue‐specific expression during embryonic development

“…One possibility is obviously that there is an indirect interaction between collagens I and XII. In fact, in experiments with isolated and purified matrix components it has been shown that type XI1 collagen and its homologue type XIV bind to heparin and dermatan sulfate (Brown et al, 1993;Font et al, 1993;Koch et al, 1995). It is therefore possible that interactions with the glycosaminoglycan side chains of fibril-associated proteoglycans such as decorin may mediate the association with collagen fibrils.…”

Mechanical Strain Increases Expression of Type XII Collagen in Murine Osteoblastic MC3T3-E1 Cells

“…Type XII collagen α1 chain (α1(XII)) is encoded by a single gene, and differential splicing within NC3, one of the collagenase-resistant globular domains in the amino terminus of the α1(XII), results in a long and a short variant. The long form can carry a glycosaminoglycan (Koch et al, 1995) and is detected as early as Day 3 embryo of chick (Akimoto et al, 2002). It was reported that the NC3 domain of α1(XII) could modulate the biomechanical properties of collagen gel contraction in vitro (Nishiyama et al, 1994), and interacted with decorin and fibromodulin (Font et al, 1996;Font et al, 1998) and tenascin-X (Veit et al, 2006b).…”