Marcinkowska Ewa, Wiedłocha Antoni
Department of Reproductive Immunology, Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wrocław, Poland.
Acta Biochim Pol. 2002;49(3):735-45.
Steroid hormones in plants and in animals are very important for physiological and developmental regulation. In animals steroid hormones are recognized by nuclear receptors, which transcriptionally regulate specific target genes following binding of the ligand. In addition, numerous rapid effects generated by steroids appear to be mediated by a mechanism not depending on the activation of nuclear receptors. Although the existence of separate membrane receptors was postulated many years ago and hundreds of reports supporting this hypothesis have been published, no animal membrane steroid receptor has been cloned to date. Meanwhile, a plant steroid receptor from Arabidopsis thaliana has been identified and cloned. It is a transmembrane protein which specifically recognizes plant steroids (brassinosteroids) at the cell surface and has a serine/threonine protein kinase activity. It seems that plants have no intracellular steroid receptors, since there are no genes homologous to the family of animal nuclear steroid receptors in the genome of A. thaliana. Since the reason of the rapid responses to steroid hormones in animal cells still remains obscure we show in this article two possible explanations of this phenomenon. Using 1,25-dihydroxyvitamin D(3) as an example of animal steroid hormone, we review results of our and of other groups concordant with the hypothesis of membrane steroid receptors. We also review the results of experiments performed with ovarian hormones, that led their authors to the hypothesis explaining rapid steroid actions without distinct membrane steroid receptors. Finally, examples of polypeptide growth factor that similarly to steroids exhibit a dual mode of action, activating not only cell surface receptors, but also intracellular targets, are discussed.
植物和动物中的类固醇激素对生理和发育调节非常重要。在动物中，类固醇激素由核受体识别，核受体在配体结合后转录调节特定的靶基因。此外，类固醇产生的许多快速效应似乎是由一种不依赖于核受体激活的机制介导的。尽管多年前就有人推测存在单独的膜受体，并且已经发表了数百篇支持这一假设的报告，但迄今为止尚未克隆出动物膜类固醇受体。与此同时，一种来自拟南芥的植物类固醇受体已被鉴定和克隆。它是一种跨膜蛋白，在细胞表面特异性识别植物类固醇（油菜素类固醇），并具有丝氨酸/苏氨酸蛋白激酶活性。由于拟南芥基因组中没有与动物核类固醇受体家族同源的基因，因此植物似乎没有细胞内类固醇受体。由于动物细胞对类固醇激素快速反应的原因仍然不清楚，我们在本文中展示了对这一现象的两种可能解释。以1,25 - 二羟基维生素D(3)作为动物类固醇激素的例子，我们回顾了我们和其他研究小组与膜类固醇受体假说一致的结果。我们还回顾了用卵巢激素进行的实验结果，这些结果使作者提出了在没有明显膜类固醇受体的情况下解释类固醇快速作用的假说。最后，讨论了与类固醇类似，不仅激活细胞表面受体，还激活细胞内靶点的多肽生长因子的作用模式。
