Intracellular transport of secretory proteins in the pancreatic exocrine cell. 3. Dissociation of intracellular transport from protein synthesis.
Intracellular transport of secretory proteins in the pancreatic exocrine cell. 3. Dissociation of intracellular transport from protein synthesis.
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DOI：
10.1083/jcb.39.3.580
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发表时间：
1968-12
期刊：
影响因子：
--
通讯作者：
Palade GE
中科院分区：
文献类型：
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作者：
Jamieson JD;Palade GE
已经进行了实验以确定胰腺分泌蛋白的细胞内转运是否强制性地与蛋白质合成偶联，或者它是否是可以独立调节的可分离的过程。为此，豚鼠胰腺切片用亮氨酸-3H脉冲标记3分钟，并在脉冲后在含有放线菌酮的chase培养基中孵育37分钟，浓度高达足以抑制98%的蛋白质合成。在对照组中，新合成的分泌蛋白在此期间被运输到高尔基复合体的浓缩液泡中。由于后者在细胞分级分离时在酶原颗粒级分中回收，因此通过测量（3 + 37）min孵育后在酶原颗粒级分中发现的蛋白质放射性的量来测定细胞内转运。结果表明，在蛋白质合成的最大抑制（5 × 10-4 M放线菌酮），运输进行的效率为对照的80%。对完整切片的平行放射自显影研究证实了这些数据，并进一步表明，细胞内运输的所有步骤，包括放电到腺泡腔，是独立的蛋白质合成。我们的结论是：（1）转运和蛋白质合成是可分离的过程;（2）细胞内转运不是分泌蛋白从附着的多聚核糖体连续递送到粗面内质网池的结果;（3）转运不依赖于在测试的时间限制内“特异性”非分泌蛋白的合成。
Experiments have been carried out to determine whether intracellular transport of pancreatic secretory proteins is obligatorily coupled to protein synthesis or whether it is a separable process which can be independently regulated. To this intent, guinea pig pancreatic slices were pulse labeled with leucine-3H for 3 min and incubated post-pulse for 37 min in chase medium containing cycloheximide up to concentrations sufficient to inhibit protein synthesis by 98%. In controls, newly synthesized secretory proteins are transported over this interval to condensing vacuoles of the Golgi complex. Since the latter are recovered in the zymogen granule fraction upon cell fractionation, intracellular transport was assayed by measuring the amount of protein radioactivity found in the zymogen granule fraction after a (3 + 37) min incubation. The results indicated that at maximum inhibition of protein synthesis (5 x 10-4 M cycloheximide), transport proceeded with an efficiency ∼80% of control. Parallel radioautographic studies on intact slices confirmed these data and further indicated that all the steps of intracellular transport, including discharge to the acinar lumen, were independent of protein synthesis. We conclude that: (1) transport and protein synthesis are separable processes; (2) intracellular transport is not the result of a continuous delivery of secretory proteins from attached polysomes to the cisternae of the rough endoplasmic reticulum; and (3) transport is not dependent on the synthesis of "specific" nonsecretory proteins within the time limits tested.