Lindberg I, Ahn S C, Breslin M B
Department of Biochemistry and Molecular Biology, Louisiana State University Medical Center, New Orleans 70112.
Mol Cell Neurosci. 1994 Dec;5(6):614-22. doi: 10.1006/mcne.1994.1075.
The prohormone convertases PC1 (also known as sPC3) and PC2 are known to mediate the proteolytic conversion of inactive neuropeptide and hormone precursors to bioactive peptide products. In this study we have used sucrose density centrifugation to determine the subcellular distributions of the various forms of PC1 and PC2 in three different cell types, AtT-20, beta TC3, and PC12 cells. The former two cell lines naturally express PC enzymes, while PC12 cell clones expressing PCs were obtained by stable transfection. Our data show considerable cell-line specific variation in PC processing, with PC12 cells exhibiting the most complete processing of both enzyme precursors. While in all cell lines mature forms of both enzymes were stored within particles having the same buoyant density as secretory granule markers, in some cell lines substantial amounts of mature PC1 and PC2 were also associated with the Golgi marker. Processing of the two PC precursors was not interdependent since PC12 cells expressing only one of the two PCs were fully capable of enzyme maturation. Interestingly, analysis of intracellular processing of an endogenous peptide precursor, proneurotensin, revealed that transfected PC1, but not PC2, showed enzymatic activity against this precursor.
激素原转化酶PC1（也称为sPC3）和PC2已知可介导无活性神经肽和激素前体向生物活性肽产物的蛋白水解转化。在本研究中，我们使用蔗糖密度离心法来确定三种不同细胞类型（AtT-20、βTC3和PC12细胞）中各种形式的PC1和PC2的亚细胞分布。前两种细胞系天然表达PC酶，而表达PC的PC12细胞克隆则通过稳定转染获得。我们的数据显示，在PC加工过程中存在相当大的细胞系特异性差异，PC12细胞对两种酶前体的加工最为完整。虽然在所有细胞系中，两种酶的成熟形式都储存在与分泌颗粒标记物具有相同浮力密度的颗粒中，但在某些细胞系中，大量成熟的PC1和PC2也与高尔基体标记物相关。两种PC前体的加工并不相互依赖，因为仅表达两种PC之一的PC12细胞完全能够使酶成熟。有趣的是，对内源性肽前体神经降压素原的细胞内加工分析表明，转染的PC1而非PC2对该前体具有酶活性。
