Vladutiu G D, Rattazzi M C
Biochem J. 1980 Dec 15;192(3):813-20. doi: 10.1042/bj1920813.
The carboxylic ionophore, monensin, blocks the migration of glycoprotein-containing vesicles from the Golgi region to the plasma membrane in fibroblasts resulting in an accumulation of secretory products in the Golgi cisternae. Treatment of cultured I-cell fibroblasts with monensin (0.5 muM) decreased the abnormal excretion of beta-hexosaminidase to 40% of untreated cultures within 15 min. A corresponding intracellular accumulation of the enzyme to greater than 200% of untreated cultured by 24 h was also observed. A small intracellular accumulation and slightly enhanced excretion of beta-hexosaminidase occurred in treated normal fibroblasts cultures. The intra- and extra-cellular distribution of newly synthesized beta-hexosaminidase in both monensin-treated normal and I-cell fibroblasts were electrophoretically indistinguishable from the four bands characteristic of I-cell intracellular beta-hexosaminidase. The excreted enzyme from both cultures was found to be a low- or no-uptake form. This form of beta-hexosaminidase may have been excreted from a secondary route preceding the site of the monensin effect. The similar findings in monensin-treated normal and I-cell cultures suggest that the subcellular site of the biochemical defect in I-cell disease is at a location after the site of the monensin effect i.e. late in the Golgi region or at a post-Golgi-region location.
羧酸离子载体莫能菌素可阻止含糖蛋白的囊泡从成纤维细胞的高尔基体区域向质膜迁移，导致分泌产物在高尔基池中积累。用莫能菌素（0.5 μM）处理培养的I型细胞成纤维细胞，15分钟内β-己糖胺酶的异常排泄量降至未处理培养物的40%。到24小时时，还观察到该酶在细胞内的相应积累量增加到未处理培养物的200%以上。在处理过的正常成纤维细胞培养物中，β-己糖胺酶出现了少量的细胞内积累和排泄略有增加的情况。在莫能菌素处理的正常和I型细胞成纤维细胞中，新合成的β-己糖胺酶的细胞内和细胞外分布在电泳上与I型细胞内β-己糖胺酶的四条特征带无法区分。两种培养物中排泄出的酶均为低摄取或无摄取形式。这种形式的β-己糖胺酶可能是从莫能菌素作用位点之前的第二条途径排泄出来的。在莫能菌素处理的正常和I型细胞培养物中的类似发现表明，I型细胞疾病生化缺陷的亚细胞位点位于莫能菌素作用位点之后，即在高尔基体区域后期或高尔基体区域之后的位置。
