Andric Silvana A, Janjic Marija M, Stojkov Natasa J, Kostic Tatjana S
Laboratory for Reproductive Endocrinology and Signaling, DBE, Faculty of Sciences, University of Novi Sad, Dositeja Obradovica Square 2, 21000, Novi Sad, Serbia.
Am J Physiol Endocrinol Metab. 2007 Nov;293(5):E1399-408. doi: 10.1152/ajpendo.00482.2007. Epub 2007 Sep 11.
The androgen-secreting Leydig cells produce cGMP, but the pathways responsible for generation and actions of this intracellular messenger have been incompletely characterized in these cells. Here, we show the presence of mRNA transcripts for the membrane-bound and soluble guanylyl cyclases (sGC), the cGMP-specific phosphodiesterase 5, and the cGMP-dependent protein kinase I (PKG I) and PKG II in purified rat Leydig cells from adult animals. Stimulation of both guanylyl cyclases and inhibition of phosphodiesterase 5 in vitro were accompanied by elevations in cGMP and androgen production, whereas inhibition of sGC and PKG led to a decrease in steroidogenesis. The stimulatory action of cGMP on steroidogenesis was preserved in cells with inhibited cAMP-dependent protein kinases. Experiments with exogenously added substrates revealed the dependence of cGMP-induced progesterone and androgen synthesis on cholesterol but not on 22-OH cholesterol, pregnenolone, progesterone, and Delta(4)-androstenedione. Treatment with nitric oxide donor increased phosphorylation of the steroidogenic acute regulatory protein (StAR). In contrast, inhibition of sGC and PKG, but not protein kinase A, significantly reduced StAR phosphorylation. These results suggest that cGMP contributes to the control of basal steroidogenesis in Leydig cells through the PKG-dependent modification of the StAR protein.
分泌雄激素的睾丸间质细胞可产生环磷酸鸟苷（cGMP），但这种细胞内信使的生成及作用途径在这些细胞中尚未完全明确。在此，我们发现成年动物纯化的大鼠睾丸间质细胞中存在膜结合型和可溶性鸟苷酸环化酶（sGC）、cGMP特异性磷酸二酯酶5、cGMP依赖性蛋白激酶I（PKG I）和PKG II的mRNA转录本。体外刺激鸟苷酸环化酶并抑制磷酸二酯酶5会伴随着cGMP和雄激素生成的增加，而抑制sGC和PKG则会导致类固醇生成减少。在cAMP依赖性蛋白激酶被抑制的细胞中，cGMP对类固醇生成的刺激作用依然存在。使用外源添加底物进行的实验表明，cGMP诱导的孕酮和雄激素合成依赖于胆固醇，而非22-羟基胆固醇、孕烯醇酮、孕酮和Δ4-雄烯二酮。用一氧化氮供体处理可增加类固醇生成急性调节蛋白（StAR）的磷酸化。相反，抑制sGC和PKG，而非蛋白激酶A，可显著降低StAR的磷酸化。这些结果表明，cGMP通过PKG依赖的StAR蛋白修饰作用，参与调控睾丸间质细胞的基础类固醇生成。
