Goschzik Tobias, Cremer Harold, Gnanapragassam Vinayaga S, Horstkorte Rüdiger, Bork Kaya, Diestel Simone
Institute of Nutrition and Food Sciences, Human Metabolomics, University of Bonn, Katzenburgweg 9a, 53115 Bonn, Germany.
IBDM-Developmental Biology Institute of Marseille, UMR 7288, Case 907-Parc Scientifique de Luminy, 13288 Marseille Cedex 9, France.
Neurosci Res. 2017 Jul;120:28-35. doi: 10.1016/j.neures.2017.02.002. Epub 2017 Feb 11.
The cytoplasmic domain of the neural cell adhesion molecule NCAM contains several putative serine/threonine phosphorylation sites whose functions are largely unknown. Human NCAM140 (NCAM140) possesses a potential MAP kinase phosphorylation site at threonine (T) 803. The aim of this study was to analyze a possible phosphorylation of NCAM140 by MAP kinases and to identify the functional role of T803. We found that NCAM140 is phosphorylated by the MAP kinase ERK2 in vitro. Exchange of T803 to aspartic acid (D) which mimics constitutive phosphorylation at the respective position resulted in increased endocytosis compared to NCAM140 in neuroblastoma cells and primary neurons. Consistently, NCAM140 endocytosis was inhibited by the MEK inhibitor U0126 in contrast to NCAM140-T803D or NCAM140-T803A endocytosis supporting a role of a potential ERK2 mediated phosphorylation at this site in endocytosis. Furthermore, cells expressing NCAM140-T803D developed significantly shorter neurites than NCAM140 expressing cells indicating that a potential phosphorylation of NCAM by ERK2 also regulates NCAM-dependent neurite outgrowth.
神经细胞黏附分子NCAM的胞质结构域包含几个假定的丝氨酸/苏氨酸磷酸化位点，其功能大多未知。人NCAM140在苏氨酸（T）803处有一个潜在的丝裂原活化蛋白激酶（MAP激酶）磷酸化位点。本研究的目的是分析MAP激酶对NCAM140的可能磷酸化作用，并确定T803的功能作用。我们发现，在体外，NCAM140可被MAP激酶ERK2磷酸化。将T803替换为天冬氨酸（D）可模拟相应位置的组成型磷酸化，与神经母细胞瘤细胞和原代神经元中的NCAM140相比，其胞吞作用增强。与此一致的是，MEK抑制剂U0126可抑制NCAM140的胞吞作用，而NCAM140 - T803D或NCAM140 - T803A的胞吞作用则不受影响，这支持了该位点潜在的ERK2介导的磷酸化在胞吞作用中的作用。此外，表达NCAM140 - T803D的细胞长出的神经突明显短于表达NCAM140的细胞，这表明ERK2对NCAM的潜在磷酸化也调节了NCAM依赖的神经突生长。
