Liu G, Newell P C
Department of Biochemistry, University of Oxford, UK.
J Cell Sci. 1994 Jul;107 ( Pt 7):1737-43. doi: 10.1242/jcs.107.7.1737.
Previous studies on the chemotactic movement of Dictyostelium have indicated a role for cyclic GMP in regulating the association of myosin II with the cytoskeleton. In this study we have examined the part played by phosphorylation of the 18 kDa myosin regulatory light chain in this event. Using streamer F mutant NP368 (which is deficient in the structural gene for cyclic GMP-specific phosphodiesterase) we find that, for the regulatory light chain kinase, the major peak of phosphorylation is delayed compared to the parental control strain XP55, occurring at 80 seconds rather than about 30 seconds in XP55. In two independently derived mutants that are unable to increase their cellular concentration of cyclic GMP (above basal levels) in response to a chemotactic stimulus of cyclic AMP (KI-10 and SA219), no increase in the phosphorylation of the light chain occurred, or movement of myosin II to the cytoskeleton. We also find a smaller peak of light chain phosphorylation that occurs within 10 seconds of cyclic AMP stimulation of the amoebae, and which is absent in the cyclic GMP-unresponsive strains. We conclude that cyclic GMP is involved in regulating light chain phosphorylation in this system. The possible significance of these findings is discussed and a model that relates these findings to published data on cytoskeletal myosin changes during chemotaxis is presented.
先前关于盘基网柄菌趋化运动的研究表明，环鸟苷酸（cGMP）在调节肌球蛋白II与细胞骨架的结合中发挥作用。在本研究中，我们检测了18 kDa肌球蛋白调节轻链磷酸化在此过程中所起的作用。使用拖尾F突变体NP368（其缺乏环鸟苷酸特异性磷酸二酯酶的结构基因），我们发现，对于调节轻链激酶而言，与亲本对照菌株XP55相比，磷酸化的主要峰值出现延迟，在NP368中出现在80秒，而在XP55中约为30秒。在两个独立衍生的突变体（KI-10和SA219）中，它们在受到环磷酸腺苷（cAMP）趋化刺激时无法提高细胞内环鸟苷酸浓度（高于基础水平），轻链磷酸化没有增加，肌球蛋白II也没有向细胞骨架移动。我们还发现，在对变形虫进行环磷酸腺苷刺激后10秒内会出现一个较小的轻链磷酸化峰值，而在对环鸟苷酸无反应的菌株中则不存在。我们得出结论，环鸟苷酸参与调节该系统中的轻链磷酸化。讨论了这些发现的可能意义，并提出了一个将这些发现与已发表的关于趋化过程中细胞骨架肌球蛋白变化的数据相关联的模型。
