Crouch E, Quinones F, Chang D
Am Rev Respir Dis. 1986 Apr;133(4):618-25. doi: 10.1164/arrd.1986.133.4.618.
Pulmonary basement membranes are believed to play important roles in lung morphogenesis, in maintenance of lung alveolar architecture, and in repair after pulmonary injury. However, very little is known about the synthesis and matrix deposition of lung basement membrane macromolecules. Accordingly, we have investigated the synthesis of type IV procollagen, the major collagenous component of basement membranes, in slices of adult rat lung. After a 4-h labeling with [3H]proline, type IV procollagen chains were extracted from lung homogenates with 2 M guanidine-HCl and purified by salt fractionation and ion exchange chromatography. The chains comigrated with authentic type IV chains by SDS-PAGE and were selectively coprecipitated with antibodies to type IV collagen. Peptide mapping confirmed their identity as pro alpha 1(IV) and pro alpha 2(IV), and suggested that the chains are predominantly assembled as heteropolymers. There was no evidence for proteolytic processing of the newly synthesized type IV procollagen even though type I and III procollagens were rapidly processed to lower molecular weight intermediates and collagen. Type IV procollagen accounted for approximately 40% of the extracted radiolabeled collagen, suggesting that there may be a relatively high turnover of lung basement membrane collagen in vivo.
肺基底膜被认为在肺形态发生、肺泡结构维持以及肺损伤后的修复中发挥重要作用。然而，关于肺基底膜大分子的合成和基质沉积却知之甚少。因此，我们研究了成年大鼠肺切片中IV型前胶原（基底膜的主要胶原成分）的合成。用[3H]脯氨酸标记4小时后，从肺匀浆中用2M盐酸胍提取IV型前胶原链，并通过盐分级分离和离子交换色谱法进行纯化。这些链在SDS-PAGE中与真实的IV型链共迁移，并被IV型胶原抗体选择性共沉淀。肽图谱分析证实它们为proα1(IV)和proα2(IV)，并表明这些链主要组装成异源聚合物。即使I型和III型前胶原迅速加工成低分子量中间体和胶原，也没有证据表明新合成的IV型前胶原存在蛋白水解加工。IV型前胶原约占提取的放射性标记胶原的40%，这表明体内肺基底膜胶原可能有相对较高的周转率。
