Chisholm R L, Hopkinson S, Lodish H F
Proc Natl Acad Sci U S A. 1987 Feb;84(4):1030-4. doi: 10.1073/pnas.84.4.1030.
Extracellular cAMP plays a crucial role in regulating the developmental program of Dictyostelium discoideum, functioning as a chemotactic agent, as well as a signal that regulates expression of developmentally expressed genes. These activities appear to be mediated by a cell-surface receptor for cAMP. We have studied the regulation of this receptor in cells developed in starved suspension cultures exposed to 50 nM pulses of cAMP every 6 min. cAMP-pulsed cells display roughly 10-fold higher cAMP receptor levels than cells that developed on filters or that were starved in suspension without cAMP pulses. Based on saturation binding analysis, the superinduced binding activity represents an increase in receptor number, while receptor affinity for cAMP is unaffected. Photoaffinity labeling of superinduced cells results in specific labeling of the same molecules that are labeled in starved cells. This increased cAMP binding activity was also detected in membrane preparations from cAMP-pulsed cells. These results provide evidence for an unusual mode of receptor regulation: autogenous induction of the receptor by its ligand.
细胞外环磷酸腺苷（cAMP）在调节盘基网柄菌的发育程序中起着关键作用，它作为一种趋化剂，同时也是一种调节发育相关基因表达的信号。这些活动似乎是由一种cAMP细胞表面受体介导的。我们研究了在饥饿悬浮培养中每6分钟暴露于50 nM cAMP脉冲下发育的细胞中该受体的调节情况。与在滤膜上发育的细胞或在无cAMP脉冲的悬浮液中饥饿的细胞相比，cAMP脉冲处理的细胞显示出大约高10倍的cAMP受体水平。基于饱和结合分析，超诱导的结合活性代表受体数量的增加，而受体对cAMP的亲和力不受影响。对超诱导细胞进行光亲和标记会导致与饥饿细胞中标记的相同分子的特异性标记。在cAMP脉冲处理细胞的膜制备物中也检测到了这种增加的cAMP结合活性。这些结果为一种不寻常的受体调节模式提供了证据：受体由其配体自身诱导。
