Relevant cAMP-specific phosphodiesterase isoforms in human pituitary:: Effect of Gsα mutations
Relevant cAMP-specific phosphodiesterase isoforms in human pituitary:: Effect of Gsα mutations
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DOI：
10.1210/jc.86.8.3795
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发表时间：
2001-08-01
影响因子：
5.8
通讯作者：
Spada, A
中科院分区：
文献类型：
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作者：
Persani, L;Borgato, S;Spada, A
腺苷酸环化酶产生的cAMP和磷酸二酯酶降解的cAMP都可以解释细胞内cAMP的水平。我们之前证明了携带gsp癌基因的gh分泌腺瘤中磷酸二酯酶活性增加。在这里，我们描述了人垂体和gsp +和gsp - gh分泌腺瘤中camp特异性磷酸二酯酶基因的活性和表达，并分析了这种细胞内反馈机制对camp响应元件结合蛋白磷酸化水平的影响。正常垂体和分泌gsp- gh的腺瘤表现出相似的磷酸二酯酶活性，而gsp+肿瘤的磷酸二酯酶活性高7倍。在这些肿瘤中，活性的增加主要是由于异丁基甲基黄嘌呤敏感的磷酸二酯酶4和异丁基甲基黄嘌呤不敏感的异构体。通过半定量RT-PCR，所有磷酸二酯酶4转录本在正常垂体和肿瘤垂体中均有表达。然而，gsp+组织中磷酸二酯酶4C和4D信使rna水平明显高于分泌gsp- GH的腺瘤和正常垂体。甲状腺特异性异丁基甲基黄嘌呤不敏感磷酸二酯酶8B在正常垂体中不表达，但在几乎所有gh分泌腺瘤中均可检测到，在gsp +中表达较高（P < 0.02）。因此，本研究提供了磷酸二酯酶在人垂体中的表达特征，并证明了camp特异性磷酸二酯酶4C、磷酸二酯酶4D和磷酸二酯酶8B在gsp+ gh分泌腺瘤中的显著诱导作用。在gsp -和gsp + gh分泌腺瘤中观察到相似水平的camp响应元件结合蛋白磷酸化；然而，磷酸二酯酶阻断导致camp响应元件结合蛋白磷酸化增加，在gsp+腺瘤中明显高于gsp-腺瘤。由于cAMP响应元件结合蛋白是cAMP通路的主要终点，这些结果表明，磷酸二酯酶活性的增强可能对gsp突变的表型表达有显著影响。
Both cAMP production by adenylyl cyclase and cAMP degradation by phosphodiesterases account for intracellular cAMP levels. We previously demonstrated an increased phosphodiesterase activity in GH-secreting adenomas bearing the gsp oncogene. Here we characterize both the activity and the expression of cAMP-specific phosphodiesterase genes in the human pituitary and in gsp + and gsp - GH-secreting adenomas and analyze the impact of this intracellular feedback mechanism on the levels of cAMP-responsive element-binding protein phosphorylation. Normal pituitary and gsp- GH-secreting adenomas showed similar phosphodiesterase activities, and 7-fold higher levels were observed in gsp+ tumors. In these tumors the increased activity was mainly owing to isobutyl-methyl-xanthine-sensitive phosphodiesterase 4 and to isobutyl-methyl-xanthine-insensitive isoforms. By semiquantitative RT-PCR, all phosphodiesterase 4 transcripts were expressed in the normal and tumoral pituitary. However, the levels of phosphodiesterase 4C and 4D messenger RNAs were significantly higher in gsp+ than in gsp- GH- secreting adenomas and normal pituitary. Expression of the thyroid-specific isobutyl-methyl-xanthine-insensitive phosphodiesterase 8B was absent in the normal pituitary but detectable in almost all GH-secreting adenomas and higher in gsp + (P < 0.02). Therefore, this study provides a characterization of phosphodiesterase expression in human pituitary and demonstrates a dramatic induction of the cAMP-specific phosphodiesterases 4C and phosphodiesterases 4D and phosphodiesterases 8B in gsp+ GH-secreting adenomas. Similar levels of cAMP-responsive element-binding protein phosphorylation were observed in gsp - and gsp + GH-secreting adenomas; however, phosphodiesterase blockade caused an increase in cAMP-responsive element-binding protein phosphorylation that was significantly higher in gsp+ than in gsp- adenomas. Because cAMP-responsive element-binding protein represents the principal end point of the cAMP pathway, these results suggest that the enhanced phosphodiesterase activity may have a significant impact on the phenotypic expression of gsp mutations.