Fontana D R, Price P L
Dept. of Microbiology, University of Minnesota Medical School, Minneapolis 55455.
Dev Genet. 1988;9(4-5):279-92. doi: 10.1002/dvg.1020090410.
cAMP and cell-cell contact are involved in the coordination of differentiation and morphogenesis in Dictyostelium discoideum. The experiments described in this paper establish a relationship between cAMP and cell-cell contact. Contact between Enterobacter aerogenes and aggregation-competent Dictyostelium amoebae and contact between Dictyostelium amoebae themselves results in the transient secretion of cAMP and an alteration in the amount of cAMP secreted in response to subsequent stimulation by cAMP, i.e., an alteration in magnitude of a cAMP relay response. The subsequent cAMP relay response can be enhanced or diminished depending upon the number of contacts formed and the concentration of cAMP present at the time of contact. Latex beads are capable of evoking cAMP secretion. However, the bead/amoebal contact is unable to alter the magnitude of a subsequent response to cAMP. This suggests that a nonspecific interaction via cell-cell contact elicits transient cAMP secretion in aggregation-competent Dictyostelium amoebae. The two responses to cell-cell contact are distinct from each other and distinct from the cAMP relay response. 1) The dose-response curves for the responses to Enterobacter contact are clearly different. 2) Contact with latex beads can elicit cAMP secretion but not alter the magnitude of a subsequent cAMP relay response. 3) The temperature dependences of the contact-induced responses and the cAMP relay response show that only the contact-induced cAMP secretion is inhibited at 12 and 15 degrees C, while only the cAMP relay response is inhibited at 28 degrees C. A 4-second application of cAMP at the time that contact is initiated enhances both contact-induced responses. Whether the relationship between these two developmental regulators is important for the regulation of Dictyostelium development has yet to be established.
环磷酸腺苷（cAMP）和细胞间接触参与了盘基网柄菌（Dictyostelium discoideum）分化与形态发生的协调过程。本文所述实验确立了cAMP与细胞间接触之间的关系。产气肠杆菌（Enterobacter aerogenes）与具备聚集能力的盘基网柄菌变形虫之间的接触以及盘基网柄菌变形虫自身之间的接触，会导致cAMP的短暂分泌，并且会改变在随后受到cAMP刺激时所分泌的cAMP量，即cAMP信号传递反应幅度的改变。后续的cAMP信号传递反应可根据形成的接触数量以及接触时存在的cAMP浓度而增强或减弱。乳胶珠能够引发cAMP分泌。然而，珠/变形虫接触无法改变对随后cAMP反应的幅度。这表明通过细胞间接触的非特异性相互作用会在具备聚集能力的盘基网柄菌变形虫中引发短暂的cAMP分泌。对细胞间接触的两种反应彼此不同，也不同于cAMP信号传递反应。1）对产气肠杆菌接触的反应的剂量反应曲线明显不同。2）与乳胶珠接触可引发cAMP分泌，但不会改变随后cAMP信号传递反应的幅度。3）接触诱导反应和cAMP信号传递反应的温度依赖性表明，仅接触诱导的cAMP分泌在12摄氏度和15摄氏度时受到抑制，而仅cAMP信号传递反应在28摄氏度时受到抑制。在接触开始时施加4秒的cAMP会增强两种接触诱导反应。这两种发育调节因子之间的关系对于盘基网柄菌发育的调节是否重要还有待确定。
