title: Abnormal type I collagen metabolism by cultured fibroblasts in lethal perinatal osteogenesis imperfecta.
abstract: Cultured skin fibroblasts from seven consecutive cases of lethal perinatal osteogenesis imperfecta (OI) expressed defects of type I collagen metabolism. The secretion of [14C]proline-labelled collagen by the OI cells was specifically reduced (51-79% of control), and collagen degradation was increased to twice that of control cells in five cases and increased by approx. 30% in the other two cases. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis revealed that four of the OI cell lines produced two forms of type I collagen consisting of both normally and slowly migrating forms of the alpha 1(I)- and alpha 2(I)-chains. In the other three OI cell lines only the 'slow' alpha (I)'- and alpha 2(I)'-chains were detected. In both groups inhibition of the post-translational modifications of proline and lysine resulted in the production of a single species of type I collagen with normal electrophoretic migration. Proline hydroxylation was normal, but the hydroxylysine contents of alpha 1(I)'- and alpha 2(I)'-chains purified by h.p.l.c. were greater than in control alpha-chains. The glucosylgalactosylhydroxylysine content was increased approx. 3-fold while the galactosylhydroxylysine content was only slightly increased in the alpha 1(I)'-chains relative to control alpha 1(I)-chains. Peptide mapping of the CNBr-cleavage peptides provided evidence that the increased post-translational modifications were distributed throughout the alpha 1(I)'- and alpha 2(I)'-chains. It is postulated that the greater modification of these chains was due to structural defects of the alpha-chains leading to delayed helix formation. The abnormal charge heterogeneity observed in the alpha 1 CB8 peptide of one patient may reflect such a structural defect in the type I collagen molecule.
mesh_terms: D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D003094:Collagen / Q000378:metabolism*; D003488:Cyanogen Bromide; D004591:Electrophoresis, Polyacrylamide Gel; D005347:Fibroblasts / Q000378:metabolism*; D006801:Humans; D007231:Infant, Newborn; D008239:Lysine / Q000378:metabolism; D010013:Osteogenesis Imperfecta / Q000151:congenital / Q000378:metabolism*; D010446:Peptide Fragments / Q000032:analysis; D011347:Procollagen / Q000378:metabolism; D011392:Proline / Q000378:metabolism; D014176:Protein Biosynthesis; D012867:Skin / Q000378:metabolism
chemical_list: D010446:Peptide Fragments; D011347:Procollagen; D003094:Collagen; D011392:Proline; D008239:Lysine; D003488:Cyanogen Bromide