Castle A M, Huang A Y, Castle J D
Department of Cell Biology, University of Virginia Health Sciences Center, Charlottesville 22908, USA.
FEBS Lett. 1998 Nov 20;439(3):341-5. doi: 10.1016/s0014-5793(98)01398-2.
Constitutively secreted proteins have traditionally been believed to be excluded from the regulated secretory pathway. In this work we show that kappa light chain and Fc fragment, two markers of the constitutive pathway, are present in the regulated pathway in AtT-20 cells. They colocalize with the endogenous hormone ACTH and they exhibit stimulus-dependent secretion. The Fc fragment, which undergoes intracellular transport at the same rate as the ACTH precursor POMC, enters the forming secretory granules, however, it is partially lost during granule maturation. These observations show that classic constitutive secretory markers are not excluded from the regulated secretory pathway and that efficient sorting for regulated secretion occurs above a background of proteins which enter the granules without sorting.
传统观点认为，组成型分泌蛋白被排除在调节型分泌途径之外。在本研究中，我们发现κ轻链和Fc片段这两个组成型途径的标志物存在于AtT - 20细胞的调节型途径中。它们与内源性激素促肾上腺皮质激素（ACTH）共定位，并且表现出刺激依赖性分泌。Fc片段与ACTH前体阿黑皮素原（POMC）以相同速率进行细胞内运输，进入正在形成的分泌颗粒，然而，它在颗粒成熟过程中会部分丢失。这些观察结果表明，经典的组成型分泌标志物并未被排除在调节型分泌途径之外，并且在没有分选就进入颗粒的蛋白质背景之上，发生了针对调节型分泌的有效分选。
