Cronshagen U, Voland P, Kern H F
Department of Cell Biology, University of Marburg, Germany.
Eur J Cell Biol. 1994 Dec;65(2):366-77.
By immunoscreening of a cDNA expression library of rat pancreas with a polyspecific antibody to purified rat zymogen granule membranes, we have cloned a cDNA coding for a novel protein of about 16 kDa (ZG-16p). By both immunocytochemistry and Western blot analysis of different fractions of rat pancreas with anti-ZG-16 antibodies, the protein could be localized in the content fraction of zymogen granules and also, to a lesser extent, bound to the granule membranes. Computer-based sequence analysis revealed no significant homologies to any of the known proteins of zymogen granules. A N-terminal portion of about 20 amino acids was predicted as a potential secretory signal sequence and may reflect the intracellular localization of the protein. As revealed by Northern blot analysis of total RNA from various organs of the rat, expression of the corresponding gene is restricted by only pancreas, colon, duodenum, and, to a much lesser extent, stomach. No traces of ZG-16 RNA were detectable in any of the other tissues tested so far. Expression of the ZG-16-gene in pancreatic cells is slightly stimulated by treatment of rats with cerulein, a decapeptide analogue of cholecystokinin, which is known to stimulate secretion in acinar cells. In contrast, treatment of the rat pancreatic tumor cell line, AR4-2J, with 10 nM dexamethasone, which has been shown to increase the synthesis and secretion of all secretory enzymes of rat pancreas accompanied with an increase in the secretory machinery, leads to a remarkable increase in the expression of ZG-16. Thus the expression pattern of the ZG-16 gene in response to hormonal stimulation of rat pancreatic acinar cells resembles those found for most of the secretory enzymes. The localization of ZG-16p and the regulation of ZG-16 gene expression in response to hormonal stimulation of pancreatic acinar cells leads us to presume that this novel protein has a functional role in the complex and ill-understood processes involved in the regulated secretory pathway of these cells.
通过用针对纯化的大鼠酶原颗粒膜的多特异性抗体对大鼠胰腺的cDNA表达文库进行免疫筛选，我们克隆了一个编码约16 kDa新蛋白（ZG-16p）的cDNA。用抗ZG-16抗体对大鼠胰腺的不同组分进行免疫细胞化学和蛋白质印迹分析，结果显示该蛋白可定位在酶原颗粒的内容物组分中，并且在较小程度上也与颗粒膜结合。基于计算机的序列分析表明，该蛋白与任何已知的酶原颗粒蛋白均无明显同源性。预测约20个氨基酸的N端部分为潜在的分泌信号序列，这可能反映了该蛋白在细胞内的定位。通过对大鼠各种器官的总RNA进行Northern印迹分析发现，相应基因的表达仅在胰腺、结肠、十二指肠以及程度较轻的胃中受到限制。在目前测试的任何其他组织中均未检测到ZG-16 RNA的痕迹。用蛙皮素（一种胆囊收缩素的十肽类似物，已知可刺激腺泡细胞分泌）处理大鼠，可轻微刺激胰腺细胞中ZG-16基因的表达。相反，用10 nM地塞米松处理大鼠胰腺肿瘤细胞系AR4-2J，已证明地塞米松可增加大鼠胰腺所有分泌酶的合成与分泌，并伴随着分泌机制的增加，结果导致ZG-16的表达显著增加。因此，ZG-16基因在大鼠胰腺腺泡细胞激素刺激下的表达模式与大多数分泌酶的表达模式相似。ZG-16p的定位以及ZG-16基因表达在胰腺腺泡细胞激素刺激下的调控，使我们推测这种新蛋白在这些细胞调节分泌途径所涉及的复杂且了解甚少的过程中具有功能作用。
