Spiro M J, Kumar B R, Crowley T J
Department of Medicine and Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA.
J Mol Cell Cardiol. 1992 Apr;24(4):397-410. doi: 10.1016/0022-2828(92)93194-o.
An investigation of myocardial glycoproteins was undertaken to elucidate the molecules responsible for the periodic acid-Schiff (PAS) reactivity of the increased extracellular matrix of diabetic cardiomyopathy. Perfusion with radiolabeled mannose indicated an enhanced formation of matrix components in the diabetic compared to the normal rat heart. Electrophoretic separation of radiolabeled extracts demonstrated the presence of glycoproteins with Mr values of 205, 142 and 90 kDa which could be separated by Bio-Gel A-5 m filtration. Fractionation of non-perfused hearts resulted in the isolation of only the 205 and 142 kDa components, which were shown by amino acid analyses and collagenase digestion to belong to the collagen family of proteins and by immunoblotting to represent type VI collagen. The carbohydrate content of these rat myocardial type VI collagen subunits, determined from monosaccharide analyses, was 11 and 12%, respectively, and N-glycanase digestion of the 142 kDa chain resulted in a decrease in size of approximately 14 kDa, indicating the presence of asparagine-linked units. Examination of normal and diabetic rat heart sections indicated that the latter contained abundant PAS-positive strands and nodules which corresponded to the distribution of anti type VI collagen reactivity. Moreover, immunoblots showed higher levels of Type VI collagen in diabetic than in normal heart extracts. Type VI collagen therefore appears to represent a major glycoprotein of myocardial extracellular matrix and to be implicated in diabetic cardiomyopathy.
为阐明导致糖尿病性心肌病细胞外基质增加的过碘酸希夫（PAS）反应性的分子，对心肌糖蛋白进行了研究。与正常大鼠心脏相比，用放射性标记的甘露糖灌注表明糖尿病大鼠心脏中基质成分的形成增强。放射性标记提取物的电泳分离显示存在分子量为205、142和90 kDa的糖蛋白，这些糖蛋白可通过Bio-Gel A-5 m过滤分离。对未灌注心脏进行分级分离，仅分离出205和142 kDa的成分，氨基酸分析和胶原酶消化表明它们属于胶原蛋白家族，免疫印迹表明它们代表VI型胶原蛋白。通过单糖分析确定，这些大鼠心肌VI型胶原亚基的碳水化合物含量分别为11%和12%，对142 kDa链进行N-糖苷酶消化后，其大小减少了约14 kDa，表明存在天冬酰胺连接的单元。对正常和糖尿病大鼠心脏切片的检查表明，后者含有丰富的PAS阳性条索和结节，这与抗VI型胶原反应性的分布相对应。此外，免疫印迹显示糖尿病心脏提取物中VI型胶原的水平高于正常心脏。因此，VI型胶原似乎是心肌细胞外基质的主要糖蛋白，并与糖尿病性心肌病有关。
