Identification, localization, and function in steroidogenesis of PAP7: a peripheral-type benzodiazepine receptor- and PKA (RIalpha)-associated protein.
Identification, localization, and function in steroidogenesis of PAP7: a peripheral-type benzodiazepine receptor- and PKA (RIalpha)-associated protein.
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DOI：
10.1210/mend.15.12.0736
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发表时间：
2001-12
影响因子：
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通讯作者：
Hua Li;Babett Degenhardt;Derek Tobin;Z. Yao;K. Taskén;Vassilios Papadopoulos
中科院分区：
文献类型：
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作者：
Hua Li;Babett Degenhardt;Derek Tobin;Z. Yao;K. Taskén;Vassilios Papadopoulos
肽激素和cAMP通过加速胆固醇转运到线粒体中来急剧刺激类固醇的生物合成。外周型苯二氮卓受体（PBR）已被证明是胆固醇转运机制中不可或缺的元素。利用酵母双杂交系统和PBR作为诱饵，我们确定了与PBR相互作用的蛋白质，PBR相关蛋白PAP 7。使用PKA的调节亚基RIalpha作为诱饵，我们还分离了PAP 7。在MA-10 Leydig细胞中，谷胱甘肽-S-转移酶-PAP 7与线粒体PBR和胞浆PKA-RI α相互作用。PAP 7是一种新的52 kDa的蛋白质，存在于小鼠，大鼠和人体组织中，它有一个主要的3 kb的mRNA转录在所有组织检查。免疫组织化学和原位杂交研究表明，PAP 7是高度表达的性腺，肾上腺，海马，和不同的脑神经元和胶质细胞群体。过表达全长PAP 7增加hCG诱导的类固醇产生。然而，过度表达的部分PAP 7，其中包括PBR和PKA-RI α结合域，抑制胆固醇刺激的胆固醇转运和类固醇合成。用PAP 7的反义寡核苷酸处理MA-10细胞也抑制了hCG刺激的类固醇形成，表明PAP 7是导致类固醇生成的类固醇诱导的信号转导级联的功能元件。PAP 7可以通过将PKA同工酶靶向富含PBR的细胞器（即线粒体）来发挥作用，其中特定蛋白质底物的磷酸化可以诱导PBR形貌和功能的重组。
Peptide hormones and cAMP acutely stimulate steroid biosynthesis by accelerating the transport of cholesterol into the mitochondria. The peripheral-type benzodiazepine receptor (PBR) has been shown to be an indispensable element of the cholesterol transport machinery. Using the yeast two-hybrid system and PBR as bait, we identified a protein that interacts with PBR, the PBR-associated protein PAP7. Using the regulatory subunit RIalpha of PKA as bait, we also isolated PAP7. Glutathione-S-transferase -PAP7 interacted with both the mitochondrial PBR and cytosolic PKA-RIalpha in MA-10 Leydig cells. PAP7 is a novel 52-kDa protein present in mouse, rat, and human tissues, and it has a major 3-kb mRNA transcript in all tissues examined. Immunohistochemical and in situ hybridization studies indicated that PAP7 is highly expressed in the gonads, adrenal, hippocampus, and distinct brain neuronal and glial populations. Overexpression of the full length PAP7 increased the hCG-induced steroid production. However, overexpression of a partial PAP7, which includes the PBR- and PKA-RIalpha-binding domains, inhibited the hormone-stimulated cholesterol transport and steroid synthesis. Treatment of MA-10 cells with oligonucleotides antisense to PAP7 also inhibited the hCG-stimulated steroid formation, suggesting that PAP7 is a functional element of the hormone-induced signal transduction cascade leading to steroidogenesis. PAP7 may function by targeting the PKA isoenzyme to organelles rich in PBR, i.e. mitochondria, where phosphorylation of specific protein substrates may induce the reorganization of PBR topography and function.