Schlatter Monika C, Buhusi Mona, Wright Amanda G, Maness Patricia F
Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599-7260, USA.
J Neurochem. 2008 Feb;104(3):731-44. doi: 10.1111/j.1471-4159.2007.05013.x. Epub 2007 Nov 6.
Close homolog of L1 (CHL1) is a transmembrane cell adhesion molecule with unique developmental functions in cortical neuronal positioning and dendritic projection within the L1 family, as well as shared functions in promotion of integrin-dependent neurite outgrowth and semaphorin3A (Sema3A)-mediated axon repulsion. The molecular mechanisms by which CHL1 mediates these diverse functions are obscure. Here it is demonstrated using a cytofluorescence assay that CHL1 is able to recruit ezrin, a member of the ezrin-radixin-moesin (ERM) family of filamentous actin binding proteins to the plasma membrane, and that this requires a membrane-proximal motif (RGGKYSV) in the CHL1 cytoplasmic domain. This sequence in CHL1 is shown to have novel functions necessary for Sema3A-induced growth cone collapse and CHL1-dependent neurite outgrowth and branching in cortical embryonic neurons. In addition, stimulation of haptotactic cell migration and cellular adhesion to fibronectin by CHL1 depends on the CHL1/ERM recruitment motif. These findings suggest that a direct or indirect interaction between CHL1 and ERM proteins mediates Sema3A-induced growth cone collapse as well as neurite outgrowth and branching, which are essential determinants of axon guidance and connectivity in cortical development.
L1 紧密同源物(CHL1)是一种跨膜细胞粘附分子,在 L1 家族中,它在皮层神经元定位和树突投射方面具有独特的发育功能,同时在促进整合素依赖性神经突生长和信号素 3A(Sema3A)介导的轴突排斥方面具有共同功能。CHL1 介导这些不同功能的分子机制尚不清楚。在此,通过细胞荧光测定法证明,CHL1 能够将丝状肌动蛋白结合蛋白埃兹蛋白 - 根蛋白 - 膜突蛋白(ERM)家族的成员埃兹蛋白招募到质膜,而这需要 CHL1 细胞质结构域中的一个膜近端基序(RGGKYSV)。CHL1 中的这一序列显示出对于 Sema3A 诱导的生长锥塌陷以及皮层胚胎神经元中 CHL1 依赖性神经突生长和分支所必需的新功能。此外,CHL1 对趋触性细胞迁移和细胞与纤连蛋白粘附的刺激取决于 CHL1/ERM 招募基序。这些发现表明,CHL1 与 ERM 蛋白之间的直接或间接相互作用介导了 Sema3A 诱导的生长锥塌陷以及神经突生长和分支,而这是皮层发育中轴突导向和连接性的重要决定因素。