Cathepsin B localizes to plasma membrane caveolae of differentiating myoblasts and is secreted in an active form at physiological pH
Cathepsin B localizes to plasma membrane caveolae of differentiating myoblasts and is secreted in an active form at physiological pH
复制标题
DOI：
10.1515/bc.2006.030
复制
发表时间：
2006-02-01
影响因子：
3.7
通讯作者：
Dufresne, MJ
中科院分区：
文献类型：
--
作者：
Jane, DT;Morvay, L;Dufresne, MJ
我们的体外研究支持组织蛋白酶B基因表达的诱导与体内肌肉发生期间与肌管形成相关的分解代谢重组之间存在功能联系。我们已经测试了两个预测，这是基本的假设：（1），活性组织蛋白酶B定位于融合成肌细胞的质膜小窝;（2），活性组织蛋白酶B分泌融合成肌细胞在生理pH值。在分化过程中，L 6大鼠成肌细胞表现出融合相关的增加与25/26-kDa的，充分加工，活性形式的组织蛋白酶B的活动。免疫细胞化学研究表明，溶酶体组织蛋白酶B蛋白向融合成肌细胞膜的重新分布，以及组织蛋白酶B与膜小窝的肌肉特异性结构蛋白小窝蛋白-3的共定位。蔗糖密度分级和蛋白质印迹分析表明，组织蛋白酶B的活性形式与小窝蛋白-3、膜联蛋白-VII、β-肌营养不良蛋白聚糖和肌营养不良蛋白一起定位于小窝组分沿着。最后，“实时”活性测定和蛋白质印迹分析表明，活性组织蛋白酶B分泌融合成肌细胞在生理pH值。总的来说，这些研究支持协会的活性组织蛋白酶B与质膜小窝和分泌活性组织蛋白酶B分化成肌细胞在成肌细胞融合。
Our in vitro studies support a functional link between the induction of cathepsin B gene expression and the catabolic restructuring associated with myotube formation during myogenesis in vivo. We have tested two predictions that are basic to this hypothesis: (1) that active cathepsin B is localized to plasma membrane caveolae of fusing myoblasts; and (2) that active cathepsin B is secreted from fusing myoblasts at physiological pH. During differentiation, L6 rat myoblasts demonstrated a fusion-related increase in activity associated with the 25/26-kDa, fully processed, active form of cathepsin B. Immunocytochemical studies demonstrated a redistribution of lysosomal cathepsin B protein toward the membrane of fusing myoblasts, and a colocalization of cathepsin B with caveolin-3, the muscle-specific structural protein of membrane caveolae. Sucrose density fractionation and Western blot analysis demonstrated that an active form of cathepsin B localizes to caveolar fractions along with caveolin-3, annexin-VII, beta-dystroglycan and dystrophin. Finally, 'real-time' activity assays and Western blot analysis demonstrated that active cathepsin B is secreted from fusing myoblasts at physiological pH. Collectively, these studies support an association of active cathepsin B with plasma membrane caveolae and the secretion of active cathepsin B from differentiating myoblasts during myoblast fusion.