Goldberg D, Segal M, Levitzki A
Department of Biological Chemistry, Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Israel.
FEBS Lett. 1994 Dec 19;356(2-3):249-54. doi: 10.1016/0014-5793(94)01273-3.
The Ras/cAMP pathway in the yeast S. cerevisiae couples the cell cycle of this unicellular organism to the availability of nutrients. Glucose derepressed S. cerevisiae cells respond to glucose addition by an intracellular rise in cAMP. In the prevailing model, yeast Ras plays a similar role to that of heterotrimeric G-proteins coupled to cell surface receptors. A crucial element of this model is that the exchanger, Cdc25 is activated by glucose. Such activation would result in a glucose-dependent rise in GTP-bound Ras concentration. We here show, in contrast to this view, that Cdc25 cannot be the receiver of the glucose signal. We suggest that the Ras-GTP/cyclase complex is the molecular element directly receiving the signal while Cdc25-dependent exchange constitutes a prerequisite for complex formation.
酵母酿酒酵母中的Ras/cAMP信号通路将这种单细胞生物的细胞周期与营养物质的可利用性联系起来。葡萄糖去阻遏的酿酒酵母细胞通过细胞内cAMP的升高对葡萄糖添加作出反应。在当前模型中，酵母Ras的作用类似于与细胞表面受体偶联的异源三聚体G蛋白。该模型的一个关键要素是，交换蛋白Cdc25被葡萄糖激活。这种激活将导致结合GTP的Ras浓度出现葡萄糖依赖性升高。然而，与这种观点相反，我们在此表明Cdc25不可能是葡萄糖信号的接收者。我们认为Ras-GTP/环化酶复合物是直接接收信号的分子元件，而Cdc25依赖性交换是复合物形成的先决条件。
