Susceptibility of type V collagen to neutral proteases: evidence that the major molecular species is a thrombin-sensitive heteropolymer, [.alpha.1(V)]2.alpha.2(V)

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Abstract
The susceptibility of human type V collagen to several neutral proteases was examined. Thrombin cleaved the .alpha.1(V) and .alpha.2(V) chains of this protein at 34.degree. C, producing 2 pairs of fragments with apparent MW of 95,000 and 10,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Two-dimensional 125I-labeled peptide mapping of the larger fragments demonstrated that the upper band [which comigrated with .alpha.1(I)] was derived from the .alpha.1(V) and .alpha.2(V) chains, while the other component (which comigrated with .alpha.2(I)) was a product of .alpha.1(V) alone. Cleavage of type V collagen, containing .alpha.3(V) chains, with thrombin produced an analogous pattern with 3 high MW bands. Chymotrypsin and trypsin cleaved type V collagen at 37.degree. C but not at lower temperatures. Digestion of type V collagen with elastase at 37.degree. C resulted in selective proteolysis of .alpha.2(V), leaving .alpha.1(V) essentially intact. Pepsin treatment of type V collagen from which .alpha.2(V) had been removed by elastase treatment resulted in nearly complete degradation of .alpha.1(V). Apparently, a major fraction of native type V collagen is a heteropolymer with the chain composition [.alpha.1(V)]2.alpha.2(V). Cleavage of type V collagen by thrombin may have physiologic significance in that breakdown in pericellular matrix may be an important step in the response of a tissue to injury.