Masson D, Peters P J, Geuze H J, Borst J, Tschopp J
Institute of Biochemistry, University of Lausanne, Epalinges, Switzerland.
Biochemistry. 1990 Dec 25;29(51):11229-35. doi: 10.1021/bi00503a011.
Cytolytic T-lymphocytes (CTL) harbor cytoplasmic granules containing the lytic, pore-forming protein perforin, a family of serine proteases designated granzymes, and proteoglycans as major constituents. Growth of CTL lines in the presence of PNP-xyloside completely inhibited the glycosylation of the granule-associated chondroitin sulfate A type proteoglycans. Only short glycosaminoglycan molecules were detected. The absence of intact proteoglycans neither altered the sorting of the granule-associated proteins perforin or granzyme A nor influenced their secretion into the extracellular milieu upon T-cell receptor complex stimulation. With a weak base, the pH of the granules was determined to be acidic. At pH 5.2, granzyme A and perforin formed complexes with chondroitin sulfate A. At neutral pH, perforin and only a minor fraction of granzyme A dissociated from the proteoglycan. Upon secretion of the granule contents induced by immobilized anti-CD3 antibodies, most granzyme A molecules remained complexed with the chondroitin sulfate A glycosaminoglycans, even if synthesis of intact proteoglycans was inhibited. We suggest that granule-associated molecules complex with proteoglycans under the acidic conditions prevailing in the trans Golgi and cytolytic granules. A possible pH shift occurring during exocytosis would cause perforin, but only a minor fraction of granzyme A, to dissociate from the proteoglycans.
细胞溶解性T淋巴细胞（CTL）含有细胞质颗粒，其主要成分包括具有溶解作用的成孔蛋白穿孔素、一类称为颗粒酶的丝氨酸蛋白酶以及蛋白聚糖。在PNP-木糖苷存在的情况下，CTL系的生长完全抑制了颗粒相关硫酸软骨素A型蛋白聚糖的糖基化。仅检测到短的糖胺聚糖分子。完整蛋白聚糖的缺失既未改变颗粒相关蛋白穿孔素或颗粒酶A的分选，也未影响它们在T细胞受体复合物刺激下分泌到细胞外环境中。用弱碱测定颗粒的pH值为酸性。在pH 5.2时，颗粒酶A和穿孔素与硫酸软骨素A形成复合物。在中性pH值时，穿孔素和仅一小部分颗粒酶A与蛋白聚糖解离。在固定化抗CD3抗体诱导颗粒内容物分泌后，即使完整蛋白聚糖的合成受到抑制，大多数颗粒酶A分子仍与硫酸软骨素A糖胺聚糖复合。我们认为，在反式高尔基体和溶细胞颗粒中普遍存在的酸性条件下，颗粒相关分子与蛋白聚糖形成复合物。胞吐作用期间可能发生的pH值变化会导致穿孔素，但仅一小部分颗粒酶A与蛋白聚糖解离。
