Van Haastert P J, Kesbeke F, Reymond C D, Firtel R A, Luderus E, Van Driel R
Proc Natl Acad Sci U S A. 1987 Jul;84(14):4905-9. doi: 10.1073/pnas.84.14.4905.
Dictyostelium discoideum cells contain a single ras gene (Dd-ras) that is highly homologous to mammalian ras genes. Cell transformation with a vector carrying a ras gene with a (glycine----threonine) missense mutation at position 12 causes an altered morphogenesis. Extracellular cAMP signals regulate morphogenesis and induce chemotaxis and the activation and subsequent desensitization of adenylate and guanylate cyclase. cAMP signal transduction was investigated in Dd-ras-transformed cells. Transformants that overexpress the mutated Dd-ras-Thr12 gene show normal activation and desensitization of adenylate cyclase and normal activation of guanylate cyclase. However, cAMP induces a stronger desensitization of guanylate cyclase stimulation in the Dd-ras-Thr12 transformant than in transformants overexpressing the Dd-ras-Gly12 wild-type gene or in untransformed cells. This effect was correlated with a reduced chemotactic sensitivity of the transformant expressing the mutated Dd-ras-Thr12 gene.
盘基网柄菌细胞含有一个与哺乳动物ras基因高度同源的单一ras基因（Dd-ras）。用携带在第12位有（甘氨酸----苏氨酸）错义突变的ras基因的载体进行细胞转化会导致形态发生改变。细胞外cAMP信号调节形态发生并诱导趋化性以及腺苷酸环化酶和鸟苷酸环化酶的激活及随后的脱敏。在Dd-ras转化细胞中研究了cAMP信号转导。过表达突变的Dd-ras-Thr12基因的转化体显示腺苷酸环化酶的正常激活和脱敏以及鸟苷酸环化酶的正常激活。然而，与过表达Dd-ras-Gly12野生型基因的转化体或未转化细胞相比，cAMP在Dd-ras-Thr12转化体中诱导的鸟苷酸环化酶刺激脱敏更强。这种效应与表达突变的Dd-ras-Thr12基因的转化体的趋化敏感性降低相关。
