Department of Zoology, University of Iowa, Iowa City, Iowa 52242, USA.
Dev Biol. 1981 Jun;84(2):313-21. doi: 10.1016/0012-1606(81)90399-7.
When aggregating amoebas of the cellular slime mold Dictyostelium discoideum are disaggregated and morphogenesis is reinitiated, the amoebas will reaggregate in less than 1/10th the original time. When aggregating amoebas are disaggregated and resuspended either in full nutrient medium or in buffered salts solution containing dextrose, they retain this developmentally acquired capacity to rapidly reaggregate for approximately 1 hr and then lose it completely in a synchronous and discrete step which we have referred to as the "erasure event." In this report, it is demonstrated that micromolar concentrations of cAMP completely block this transition from the developmental to vegetative state, and that other cyclic nucleotides also inhibit it, but they do so at 20-fold higher concentrations. Neither the hydrolysis products of cAMP nor the vegetative chemoattractant folic acid inhibit dedifferentiation at concentrations as high as 10(-3) M, demonstrating a specificity for cyclic nucleotides and cAMP in particular. The addition of cAMP at any time during the lag period preceding the erasure event inhibits it and addition immediately after the erasure event reverses it. Since cAMP may inhibit the transition from the developmental to vegetative state intracellularly or extracellularly, we have also examined the intracellular concentration of cAMP and the levels of cAMP binding sites on the cell surface during the erasure process. Evidence is presented that the majority of cAMP binding sites on the cell surface are not necessary for the inhibition of erasure by cAMP. The results of these latter studies are discussed in terms of alternative models for the involvement of cAMP in the transition from the developing to vegetative state.
当聚集的变形虫细胞黏菌离散被解散和形态发生重新开始时，变形虫将在不到原来时间的 1/10 内重新聚集。当聚集的变形虫被解散并悬浮在完全营养培养基或含有葡萄糖的缓冲盐溶液中时，它们保留了这种快速重新聚集的发育获得的能力，大约 1 小时，然后在一个同步和离散的步骤中完全失去，我们称之为“擦除事件”。在本报告中，证明了微摩尔浓度的 cAMP 完全阻止了从发育状态到营养状态的转变，其他环核苷酸也抑制了这种转变，但它们的抑制作用要高 20 倍。cAMP 的水解产物或营养化学引诱剂叶酸即使在高达 10(-3) M 的浓度下也不会抑制去分化，这表明环核苷酸特别是 cAMP 具有特异性。在擦除事件之前的滞后期的任何时间添加 cAMP 都会抑制它，并且在擦除事件之后立即添加会逆转它。由于 cAMP 可能在细胞内或细胞外抑制从发育到营养状态的转变，我们还检查了擦除过程中细胞内 cAMP 的浓度和细胞表面 cAMP 结合位点的水平。有证据表明，细胞表面的大多数 cAMP 结合位点对于 cAMP 抑制擦除并不必要。这些后续研究的结果根据 cAMP 参与从发育到营养状态的转变的替代模型进行了讨论。
