Alarcón C, Lincoln B, Rhodes C J
E. P. Joslin Research Laboratory, Joslin Diabetes Center, Brigham and Women's Hospital, Boston, Massachusetts 02215.
J Biol Chem. 1993 Feb 25;268(6):4276-80.
The biosynthesis of proinsulin is specifically stimulated by glucose in the pancreatic beta-cell, and this, in turn, places an increased demand on the mechanism for proinsulin to insulin conversion. Proteolytic proinsulin processing is catalyzed by two endopeptidases putatively identified as the subtilisin-related PC2 and PC3 convertases (Bennett, D. L., Bailyes, E. M., Nielson, E., Guest, P. C., Rutherford, N. G., Arden, S. D., and Hutton, J. C. (1992) J. Biol. Chem. 267, 15229-15236; Bailyes, E. M., Shennan, K. I. J., Seal, A. J., Smeekens, S. P., Steiner, D. F., Hutton, J. C., and Docherty, K. (1992) Biochem. J. 285, 391-394). In this study, we demonstrate in isolated rat pancreatic islets that the biosynthesis of PC3 was specifically stimulated by glucose relatively parallel to that of proinsulin. In contrast, however, PC2 biosynthesis was not glucose-regulated. The stimulation of PC3 and proinsulin biosynthesis was observed above a threshold of 4 mM glucose and reached a maximum (about 7-10-fold) above 10 mM glucose concentrations. Glucose stimulation for PC3 and proinsulin biosynthesis was rapid (occurring within 20 min and reaching a maximum by 60 min) and was not affected by the additional presence of actinomycin D, suggesting regulation predominantly at the translational level. Moreover, the intracellular signals for glucose-stimulated PC3 and proinsulin biosynthesis appeared to be similar, requiring the metabolism of glucose. PC3 has been implicated as the key endopeptidase in proinsulin to insulin conversion, in that it is the enzyme which preferentially initiates the process (Rhodes, C. J., Lincoln, B., and Shoelson, S. E. (1992) J. Biol. Chem. 267, 22719-22727). We suggest that co-ordinate stimulation of PC3 biosynthesis, along with that of its proinsulin substrate, elucidates an additional control point by which the mechanism of proprotein processing might be regulated.
在胰腺β细胞中，葡萄糖特异性地刺激胰岛素原的生物合成，这反过来又对胰岛素原转化为胰岛素的机制提出了更高的要求。蛋白水解性胰岛素原加工由两种内肽酶催化，据推测这两种酶被鉴定为枯草杆菌蛋白酶相关的PC2和PC3转化酶（贝内特，D. L.，贝利耶斯，E. M.，尼尔森，E.，格斯特，P. C.，卢瑟福，N. G.，阿登，S. D.，以及赫顿，J. C.（1992年）《生物化学杂志》267卷，第15229 - 15236页；贝利耶斯，E. M.，申南，K. I. J.，西尔，A. J.，斯米肯斯，S. P.，施泰纳，D. F.，赫顿，J. C.，以及多切蒂，K.（1992年）《生物化学杂志》285卷，第391 - 394页）。在本研究中，我们在分离的大鼠胰岛中证明，PC3的生物合成受到葡萄糖的特异性刺激，其与胰岛素原的刺激相对平行。然而，相比之下，PC2的生物合成不受葡萄糖调节。在葡萄糖浓度高于4 mM的阈值时观察到PC3和胰岛素原生物合成的刺激，在葡萄糖浓度高于10 mM时达到最大值（约7 - 10倍）。葡萄糖对PC3和胰岛素原生物合成的刺激迅速（在20分钟内发生并在60分钟时达到最大值），并且不受放线菌素D额外存在的影响，这表明主要在翻译水平进行调节。此外，葡萄糖刺激PC3和胰岛素原生物合成的细胞内信号似乎相似，需要葡萄糖的代谢。PC3被认为是胰岛素原转化为胰岛素的关键内肽酶，因为它是优先启动该过程的酶（罗兹，C. J.，林肯，B.，以及肖尔森，S. E.（1992年）《生物化学杂志》267卷，第22719 - 22727页）。我们认为，PC3生物合成与其胰岛素原底物的协同刺激阐明了前体蛋白加工机制可能被调节的另一个控制点。
