Grant Paul A A, Best Sabine L, Sanmugalingam Nimalan, Alessio Rayan, Jama Abdirahman M, Török Katalin
Division of Basic Medical Sciences, St George's, University of London, Cranmer Terrace, London SW17 0RE, UK.
Cell Calcium. 2008 Nov;44(5):465-78. doi: 10.1016/j.ceca.2008.03.003. Epub 2008 Apr 23.
Persistent elevation of the intracellular free Ca(2+) concentration Ca(2+) is neurotoxic and therefore it is important to understand how it affects downstream components of the Ca(2+) signaling pathway. The response of calmodulin (CaM) and alphaCa(2+)/CaM-dependent protein kinase II (alphaCaMKII), to intracellular Ca(2+) overload in hippocampal neurons is studied by confocal imaging of fluorescently tagged proteins. Transient and persistent redistribution of CaM and alphaCaMKII together is seen from the cytosol to dendritic and somatic punctae. Typical persistent redistribution occurs following a lag of 138+/-(S.E.M.) 12 s and is complete at 460+/-(S.E.M.) 34 s (n=18), lack of Thr(286)-autophosphorylation of alphaCaMKII however promotes the formation of early transient punctae (peak at 40 s). In contrast, the T286D-mimick of phospho-Thr(286)-alphaCaMKII forms punctae with a delay >10 min, indicating that Thr(286)-autophosphorylation is antagonistic to CaMKII clustering. A two-state model is proposed in which phospho-Thr(286)-alphaCaMKII, formed immediately upon Ca(2+) stimulation, is primarily responsible for target interactions and memory functions of alphaCaMKII. However, a distinct clustering form denoted alphaCaMKII(c), generated upon persistent intracellular free Ca(2+) elevation, is deposited in the punctae which are made of self-interacting CaM/CaMKII complexes. Punctate deposition disables both the interactions and the activity of CaMKII.
细胞内游离钙离子浓度Ca(2+)的持续升高具有神经毒性，因此了解其如何影响Ca(2+)信号通路的下游成分很重要。通过对荧光标记蛋白进行共聚焦成像，研究了钙调蛋白（CaM）和αCa(2+)/CaM依赖性蛋白激酶II（αCaMKII）对海马神经元细胞内Ca(2+)过载的反应。CaM和αCaMKII共同出现从胞质溶胶到树突和体细胞斑点的瞬时和持续重新分布。典型的持续重新分布在滞后138±（标准误）12秒后发生，并在460±（标准误）34秒时完成（n = 18），然而αCaMKII缺乏苏氨酸(286)-自磷酸化会促进早期瞬时斑点的形成（在40秒时达到峰值）。相比之下，磷酸化苏氨酸(286)-αCaMKII的T286D模拟物形成斑点的延迟>10分钟，表明苏氨酸(286)-自磷酸化与CaMKII聚集相互拮抗。提出了一种双态模型，其中在Ca(2+)刺激后立即形成的磷酸化苏氨酸(286)-αCaMKII主要负责αCaMKII的靶标相互作用和记忆功能。然而，在细胞内游离Ca(2+)持续升高时产生的一种独特的聚集形式，称为αCaMKII(c)，沉积在由自相互作用的CaM/CaMKII复合物组成的斑点中。斑点状沉积会使CaMKII的相互作用和活性均失效。
