Sette C, Vicini E, Conti M
Department of Gynecology and Obstetrics, Stanford University, Medical Center, California 94305-5317.
J Biol Chem. 1994 Jul 15;269(28):18271-4.
Several mRNAs coding for a cAMP-specific phosphodiesterase (ratPDE3/IVd) with divergent 5' regions have been detected in mammalian cells. To determine the physiological significance of these differences, the expression of these mRNAs and the properties of the corresponding proteins were investigated. At least three mRNA species derived from the ratPDE3/IVd gene (ratPDE3.1, ratPDE3.2, and ratPDE3.3 mRNAs) are present in Sertoli and thyroid cells and in brain. Expression of ratPDE3.1 and ratPDE3.2 but not ratPDE3.3 mRNAs was dependent on hormone stimulation. The ratPDE3.2 and ratPDE3.3 mRNA variants were translated into polypeptides with immunochemical and biochemical properties identical to the native cAMP phosphodiesterases (PDEs) found in the Sertoli cell and thyroid FRTL-5 cells. Incubation of the recombinant PDEs with the catalytic subunit of the cAMP-dependent protein kinase in a cell-free system caused the phosphorylation and activation of the ratPDE3.3 protein variant. Under the same experimental conditions, ratPDE3.1 and ratPDE3.2 protein variants were neither phosphorylated nor activated by the cAMP-dependent protein kinase. Similar results were obtained by stimulating cells expressing the three recombinant PDE variants with dibutyryl cAMP. These findings demonstrate that the ratPDE3/IVd gene codes for PDE forms subject to different regulations.
在哺乳动物细胞中已检测到几种编码具有不同5'区域的cAMP特异性磷酸二酯酶（大鼠PDE3/IVd）的mRNA。为了确定这些差异的生理学意义，对这些mRNA的表达及相应蛋白质的特性进行了研究。大鼠PDE3/IVd基因衍生的至少三种mRNA种类（大鼠PDE3.1、大鼠PDE3.2和大鼠PDE3.3 mRNA）存在于支持细胞、甲状腺细胞和大脑中。大鼠PDE3.1和大鼠PDE3.2 mRNA的表达依赖于激素刺激，而大鼠PDE3.3 mRNA的表达则不然。大鼠PDE3.2和大鼠PDE3.3 mRNA变体被翻译成具有与在支持细胞和甲状腺FRTL-5细胞中发现的天然cAMP磷酸二酯酶（PDE）相同免疫化学和生化特性的多肽。在无细胞系统中，将重组PDE与cAMP依赖性蛋白激酶的催化亚基一起孵育，会导致大鼠PDE3.3蛋白变体的磷酸化和激活。在相同实验条件下，大鼠PDE3.1和大鼠PDE3.2蛋白变体既不被cAMP依赖性蛋白激酶磷酸化，也不被其激活。用二丁酰cAMP刺激表达三种重组PDE变体的细胞也得到了类似结果。这些发现表明，大鼠PDE3/IVd基因编码的PDE形式受到不同的调控。
