A targeted mutation at the known collagenase cleavage site in mouse type I collagen impairs tissue remodeling.

Abstract

Abstract. Degradation of type I collagen, the most abundant collagen, is initiated by collagenase cleavage at a highly conserved site between Gly775 and I1e776 of the od(I) chain. Mutations at or around this site render type I collagen resistant to collagenase digestion in vitro. We show here that mice carrying a collagenaseresistant mutant Colla-1 transgene die late in embryogenesis, ascribable to overexpression of the transgene, since the same mutation introduced into the endogenous Colla-1 gene by gene targeting permitted normal development of mutant mice to young adulthood. With increasing age, animals carrying the targeted mutation developed marked fibrosis of the dermis similar to that in human scleroderma. Postpartum involution of the uterus in the mutant mice was also impaired, with persistence of collagenous nodules in the uterine wall. AIthough type I collagen from the homozygous mutant mice was resistant to cleavage by human or rat fibroblast collagenases at the helical site, only the rat collagenase cleaved collagen trimers at an additional, novel site in the nonhelical N-telopeptide domain. Our results suggest that cleavage by murine collagenase at the N-telopeptide site could account for resorption of type I collagen during embryonic and early adult life. During intense collagen resorption, however, such as in the immediate postpartum uterus and in the dermis later in life, cleavage at the helical site is essential for normal collagen turnover. Thus, type I collagen is degraded by at least two differentially controlled mechanisms involving collagenases with distinct, but overlapping, substrate specificities.T YPE I collagen is among the most abundant components of the extracellular matrix of many tissues, particularly in skin, tendons, ligaments, uterus, large blood vessels and bone. The helical trimeric molecules of type I collagen comprise two al(I) chains and one ~2(I) chain, encoded by two separate genes, Colla-1 and Colla-2, respectively (50). In mice, type I collagen is first synthesized in the mesenchymal stroma of the head, heart and somites at day 8 of gestation (E8) and its production continues throughout development and postnatal life (27). It has been demonstrated that type I collagen is critical for bone development (9, 10), hematopoiesis (29, 37), integrity of the vascular system (29) and for mesenchymal-epithelial induction in organogenesis (6).The collagen content of different tissues during development and in adult animals is tightly regulated by coordinated processes of synthesis and degradation (2,8,57 teoporosis or inflammatory joint diseases) or excessive deposition (e.g. pulmonary fibrosis or scleroderma) (32, 39). The degradation of type I collagen requires the action of specific collagenases since native, triple-helical molecules are resistant to attack by proteolytic enzymes at 37°C and neutral pH. The collagenases are members of a family of proteinases, the metalloproteinases or matrixins, all of which contain a catalytic zinc-binding domain that includes the sequence moti...

Fibrin-Induced Skin Fibrosis in Mice Deficient in Tissue Plasminogen Activator

“…However, there is evidence to suggest that fibrotic scenarios develop in mice if MMP activity is reduced. Mice with a targeted mutation in the collagenase cleavage site in the collagen type I molecule 54,55 show a number of alterations in tissue remodeling, reflecting the inability to degrade type I collagen, including a thickening of the dermis and fascia similar to fibrin-injected skin in the present study. Haraguchi and colleagues 56 showed that when rats with experimental glomerulonephritis were treated with recombinant tPA, a significant increase in plasmin was observed that resulted not only in reduced fibrin deposition but also a significant increase in MMP activation and a concomitant reduction of collagen accumulation in the glomeruli.…”

Cell Surface-bound Collagenase-1 and Focal Substrate Degradation Stimulate the Rear Release of Motile Vascular Smooth Muscle Cells

“…This substrate was prepared from tails of transgenic mice bearing a targeted collagen mutation at collagenase-1 cleavage site. The mutation constitutes a substitution of 3 amino acids at the collagenase cleavage site of the ␣1(I) collagen chain (30,31). As shown in Fig.…”

Spatio‐temporal regulation and cleavage by matrix metalloproteinase stromelysin‐3 implicate a role for laminin receptor in intestinal remodeling during Xenopus laevis metamorphosis

“…However, it has been much more challenging to study substrate cleavage by MMPs in vivo, largely due to the difficulty of detecting the cleaved products. A combination of molecular, genetic, and cell biological studies have provided strong evidence to support the cleavage of type I collagen by collagenase 1 (MMP1) or other collagenases in vivo (Wu et al, 1990;Liu et al, 1995;Pilcher et al, 1997). In addition, by using mouse deficient in matrilysin (MMP7), the intestinal paneth cell ␣-defensins (cryptdins) and epithelial cell surface-bound proteoglycan syndecan-1 were identified as in vivo substrates of this MMP (Wilson et al, 1999;Li et al, 2002), aided in part by the formation of stable cleavage products.…”