Castillo G M, Templeton D M
Department of Clinical Biochemistry, University of Toronto, Canada.
Biochim Biophys Acta. 1992 Aug 12;1136(2):119-28. doi: 10.1016/0167-4889(92)90246-8.
Metabolism of biosynthetically [35S]sulphate-labelled heparan sulphate proteoglycan (HSPG) was studied in the isolated glomerulus. Chromatography and electrophoresis resolved HS into 5 components, designated HS1a, HS1b, and HS2 to HS4 in order of increasing Kd. Both HS1a (250 kDa) and HS1b (130 kDa) are present in the glomerular basement membrane and have glycosaminoglycan chains of 25-45 kDa. Chemical analysis of glycosaminoglycan chains indicated a similar content of 50% N-sulphation and 30% 6-O-sulphation on the hexosamine residues of all HSs, with the remaining 20% of sulphate likely at the 2-O-position of uronic acid residues. By pulse-chase analysis, the basement-membrane fraction was found to have a half-life of residency in the glomerulus of 37 h. Both HS1a and HS1b are mainly released intact into the medium and are not further broken down in that compartment. In contrast, HS2 is almost completely released into the medium immediately after synthesis and is not normally recovered from the tissue. It is a 90-kDa HSPG with a hydrophobic core protein and glycosaminoglycan chains similar in size to those of HS1. In addition to these larger PGs, HS3 and HS4 represent glycosaminoglycan chains with little or no core protein. HS1a, HS1b and HS2 were iodinated and deglycosylated. Each has a 30-kDa core protein in addition to 18 kDa of chondroitinase ABC- and nitrous-acid-resistant O-linked carbohydrate. This suggests the possibility of a single core protein with variable glycosylation and destination. HS1a has 5-6 glycosaminoglycan chains, HS1b 2-3 and HS2 1-2. We propose that basement-membrane HSPG (HS1a and HS1b) and a related, underglycosylated secreted HSPG (HS2) are the major HSPGs synthesized by the isolated glomerulus. Other molecular species may represent discrete steps in the turnover of basement-membrane HSPG.
在分离的肾小球中研究了生物合成的[35S]硫酸盐标记的硫酸乙酰肝素蛋白聚糖（HSPG）的代谢。通过色谱法和电泳将硫酸乙酰肝素（HS）分离为5种成分，按照Kd增加的顺序命名为HS1a、HS1b以及HS2至HS4。HS1a（250 kDa）和HS1b（130 kDa）均存在于肾小球基底膜中，并且具有25 - 45 kDa的糖胺聚糖链。对糖胺聚糖链的化学分析表明，所有硫酸乙酰肝素的己糖胺残基上N - 硫酸化含量均为50%，6 - O - 硫酸化含量均为30%，其余20%的硫酸盐可能位于糖醛酸残基的2 - O位。通过脉冲追踪分析发现，基底膜部分在肾小球中的驻留半衰期为37小时。HS1a和HS1b主要完整地释放到培养基中，并且在该隔室中不会进一步分解。相比之下，HS2在合成后几乎立即完全释放到培养基中，通常无法从组织中回收。它是一种90 kDa的HSPG，具有疏水核心蛋白和与HS1大小相似的糖胺聚糖链。除了这些较大的蛋白聚糖外，HS3和HS4代表几乎没有核心蛋白或没有核心蛋白的糖胺聚糖链。HS1a、HS1b和HS2被碘化并去糖基化。除了18 kDa的抗软骨素酶ABC和亚硝酸的O - 连接碳水化合物外，每种都有一个30 kDa的核心蛋白。这表明存在单个具有可变糖基化和去向的核心蛋白的可能性。HS1a有5 - 6条糖胺聚糖链，HS1b有2 - 3条，HS2有1 - 2条。我们提出基底膜HSPG（HS1a和HS1b）以及一种相关的、糖基化不足的分泌型HSPG（HS2）是分离的肾小球合成的主要HSPG。其他分子种类可能代表基底膜HSPG周转中的离散步骤。
