Quinn D, Orci L, Ravazzola M, Moore H P
Department of Molecular and Cell Biology, University of California, Berkeley 94720.
J Cell Biol. 1991 Jun;113(5):987-96. doi: 10.1083/jcb.113.5.987.
Human proinsulin and insulin oligomerize to form dimers and hexamers. It has been suggested that the ability of prohormones to self associate and form aggregates may be responsible for the sorting process at the trans-Golgi. To examine whether insulin oligomerization is required for proper sorting into regulated storage granules, we have constructed point mutations in human insulin B chain that have been previously shown to prevent formation of insulin hexamers (Brange, J., U. Ribel, J. F. Hansen, G. Dodson, M. T. Hansen, S. Havelund, S. G. Melberg, F. Norris, K. Norris, L. Snel, A. R. Sorensen, and H. O. Voight. 1988. Nature [Lond.]. 333:679-682). One mutant (B10His----Asp) allows formation of dimers but not hexamers and the other (B9Ser----Asp) prevents formation of both dimers and hexamers. The mutants were transfected into the mouse pituitary AtT-20 cells, and their ability to be sorted into regulated secretory granules was compared to wild-type insulin. We found that while B10His----Asp is sorted somewhat less efficiently than wild-type insulin as reported previously (Carroll, R. J., R. E. Hammer, S. J. Chan, H. H. Swift, A. H. Rubenstein, and D. F. Steiner. 1988. Proc. Natl. Acad. Sci. USA. 85:8943-8947; Gross, D. J., P. A. Halban, C. R. Kahn, G. C. Weir, and L. Villa-Kumaroff. 1989. Proc. Natl. Acad. Sci. USA. 86:4107-4111). B9Ser----Asp is targeted to granules as efficiently as wild-type insulin. These results indicate that self association of proinsulin into hexamers is not required for its targeting to the regulated secretory pathway.
人胰岛素原和胰岛素会寡聚形成二聚体和六聚体。有人提出，激素原自我缔合并形成聚集体的能力可能与反式高尔基体中的分选过程有关。为了研究胰岛素寡聚化对于正确分选到调节性储存颗粒中是否必要，我们构建了人胰岛素B链的点突变，这些突变先前已被证明可阻止胰岛素六聚体的形成（布兰奇，J.，U. 里贝尔，J. F. 汉森，G. 多德森，M. T. 汉森，S. 哈弗伦德，S. G. 梅尔贝格，F. 诺里斯，K. 诺里斯，L. 斯内尔，A. R. 索伦森，以及H. O. 沃伊特。1988年。《自然》[伦敦]。333:679 - 682）。一个突变体（B10His→Asp）允许形成二聚体但不形成六聚体，另一个（B9Ser→Asp）则阻止二聚体和六聚体的形成。将这些突变体转染到小鼠垂体AtT - 20细胞中，并将它们分选到调节性分泌颗粒中的能力与野生型胰岛素进行比较。我们发现，正如先前报道的那样（卡罗尔，R. J.，R. E. 哈默，S. J. 陈，H. H. 斯威夫特，A. H. 鲁宾斯坦，以及D. F. 施泰纳。1988年。《美国国家科学院院刊》。85:8943 - 8947；格罗斯，D. J.，P. A. 哈尔班，C. R. 卡恩，G. C. 韦尔，以及L. 维拉 - 库马罗夫。1989年。《美国国家科学院院刊》。86:4107 - 4111），B10His→Asp的分选效率比野生型胰岛素略低。而B9Ser→Asp与野生型胰岛素一样有效地靶向颗粒。这些结果表明，胰岛素原自我缔合成六聚体对于其靶向调节性分泌途径并非必需。
