Collagen fibrillogenesis in vitro: interaction of types I and V collagen regulates fibril diameter.
The small-diameter fibrils of the chick corneal stroma are heterotypic, composed of both collagen types I and V. This tissue has a high concentration of type V collagen relative to other type I-containing tissues with larger-diameter fibrils, suggesting that heterotypic interactions may have a regulatory role in the control of fibril diameter. The interactions of collagen types I and V were studied using an in vitro self-assembly system. Collagens were purified from lathyritic chick embryos in the presence of protease inhibitors. The type V collagen preparations contained higher molecular weight forms of the alpha 1(V) and alpha 2(V) chains constituting 60-70% of the total. Rotary-shadow electron micrographs showed a persistence of a small, pepsin-sensitive terminal region in an amount consistent with that seen by electrophoresis. In vitro, this purified type V collagen formed thin fibrils with no apparent periodicity, while type I collagen fibrils had a broad distribution of large diameters. However, when type I collagen was mixed with increasing amounts of type V collagen a progressive and significant decrease in both the mean fibril diameter and the variance was observed for D periodic fibrils. The amino-terminal domain of the type V collagen molecule was required for this regulatory effect and in its absence little diameter reducing activity was observed. Electron microscopy using collagen type-specific monoclonal antibodies demonstrated that the fibrils formed were heterotypic, containing both collagen types I and V. These data indicate that the interaction of type V with type I collagen is one mechanism modulating fibril diameter and is at least partially responsible for the regulation of collagen fibril formation.
Birk
D E
DE
Department of Pathology, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway 08854.
Fitch
J M
JM
Babiarz
J P
JP
Doane
K J
KJ
Linsenmayer
T F
TF
D000818:Animals; D000911:Antibodies, Monoclonal; D002642:Chick Embryo; D003094:Collagen / Q000302:isolation & purification / Q000378:metabolism*; D003238:Connective Tissue / Q000378:metabolism / Q000648:ultrastructure*; D003315:Cornea / Q000378:metabolism / Q000648:ultrastructure*; D004591:Electrophoresis, Polyacrylamide Gel; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D011108:Polymers
D000911:Antibodies, Monoclonal; D011108:Polymers; D003094:Collagen