Biosynthesis of somatostatin in canine fundic D cells.
Biosynthesis of somatostatin in canine fundic D cells.
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犬胃底 D 细胞中生长抑素的生物合成。
DOI：
10.1172/jci113319
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发表时间：
1988
期刊：
影响因子：
--
通讯作者：
Yamada,T
中科院分区：
文献类型：
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作者：
Chiba,T;Park,J;Yamada,T
观察到胃中几乎所有的生长抑素样免疫反应都由生长抑素-14(S14)组成，而不包括生长抑素-28(S28)，这表明了前生长抑素翻译后加工的独特模式。为了研究S14在胃中由其前体产生的机制，我们研究了犬胃底D细胞生长抑素的生物合成。用[35S]半胱氨酸脉冲标记的D细胞显示放线菌亚胺可抑制S14中放射性的时间依赖性掺入。一小部分放射性被结合到S28中，但没有进入更大的前体。然而，当细胞与莫能菌素(1微米)孵育时，发现放射性掺入假定的生长抑素前体。当将[35S]半胱氨酸预先标记的细胞转移到无放射性的培养液中时，不能检测到S28到S14的转化，细胞中标记的S14的减少与培养液中的互补增加有关。外源生长抑素抑制生长抑素的生物合成，这种抑制作用可被百日咳毒素预处理所阻断。经14-乙酰佛波酯(10(-7)M)或Forsklin(10(-4)M)刺激2 h后，新合成的放射性S14的释放量分别为41%和33%，而可放射免疫测定的生长抑素仅分泌细胞总量的9%和6%。这些数据表明：(A)生长抑素主要是在眼底D细胞中合成的S14，(B)S14是通过快速处理较大的前体而产生的，但S28到S14的转化很少(如果有的话)，(C)生长抑素的生物合成是自我调节的，以及(D)新合成的S14在刺激下优先从D细胞释放。
The observation that virtually all of the somatostatin-like immunoreactivity in the stomach consists of somatostatin-14 (S14), to the exclusion of somatostatin-28 (S28), suggests a unique pattern of prosomatostatin posttranslational processing. In order to examine the mechanisms by which S14 is produced from its precursor in the stomach, we investigated the biosynthesis of somatostatin in isolated canine fundic D cells. D cells pulse-labeled with [35S]cysteine revealed a cycloheximide inhibitable time-dependent incorporation of radioactivity into S14. A small fraction of radioactivity was incorporated into S28 but not into larger precursors. However, when the cells were incubated with monensin (1 microM), incorporation of radioactivity into a presumed somatostatin precursor was noted. Upon transfer of [35S]cysteine prelabeled cells to radioactivity-free medium, no conversion of S28 to S14 could be detected and the decrease of labeled S14 in cells correlated with a complimentary increase in the culture medium. Exogenous somatostatin inhibited somatostatin biosynthesis in a fashion that could be blocked by pertussis toxin pretreatment. Stimulation of prelabeled D cells with tetradecanoyl phorbol 13-acetate (10(-7) M) or forskolin (10(-4) M) for 2 h resulted in release of 41 and 33% of the newly synthesized radioactive S14, respectively, while only 9 and 6% of the total cell content of radioimmunoassayable somatostatin was secreted. These data suggest that: (a) somatostatin is synthesized in fundic D cells primarily as S14, (b) S14 is produced by rapid processing of a larger precursor but there is little, if any, conversion of S28 to S14, (c) somatostatin biosynthesis is autoregulated, and (d) newly synthesized S14 is preferentially released from D cells in response to stimulation.