Ruoss S J, Gold W M, Caughey G H
Cardiovascular Research Institute, University of California, San Francisco, 94143-0911.
Biochem Biophys Res Commun. 1991 Aug 30;179(1):140-6. doi: 10.1016/0006-291x(91)91346-e.
It has been hypothesized that the dissolution of mast cell granules at the time of degranulation results from proteoglycan cleavage coupled to exocytosis. To address this hypothesis, we studied granule proteoglycan before and after exocytosis in dog mastocytoma cells, which solubilize granule contents during exocytosis. 35S-labeled proteoglycans were extracted from unstimulated whole cells and cell degranulation supernatant. Sequential anion-exchange and gel filtration chromatography, followed by specific glycosaminoglycan digestion, identified chondroitin sulfate and heparin glycosaminoglycan and proteoglycan in unstimulated cells and degranulated material alike. Glycosaminoglycan type and charge density in degranulation supernatant were unchanged compared with unstimulated cells. There was no decrease in proteoglycan size with cell activation and exocytosis. Thus, granule release and solubilization does not appear to require exocytosis-coupled degradation of granule proteoglycans. Release in association with high-m.w. proteoglycans may serve to limit rates of diffusion and activity of proteases and other mast cell mediators.
据推测，肥大细胞脱颗粒时颗粒的溶解是由蛋白聚糖裂解与胞吐作用耦合引起的。为了验证这一假设，我们研究了犬肥大细胞瘤细胞胞吐前后的颗粒蛋白聚糖，这些细胞在胞吐过程中会溶解颗粒内容物。从未刺激的全细胞和细胞脱颗粒上清液中提取了35S标记的蛋白聚糖。通过连续的阴离子交换和凝胶过滤色谱，然后进行特定的糖胺聚糖消化，在未刺激的细胞和脱颗粒物质中均鉴定出硫酸软骨素和肝素糖胺聚糖及蛋白聚糖。与未刺激的细胞相比，脱颗粒上清液中的糖胺聚糖类型和电荷密度没有变化。细胞激活和胞吐时蛋白聚糖大小没有减小。因此，颗粒释放和溶解似乎不需要颗粒蛋白聚糖的胞吐耦合降解。与高分子量蛋白聚糖相关的释放可能有助于限制蛋白酶和其他肥大细胞介质的扩散速率和活性。
