Functional roles of cell adhesion molecule L1 mediates cell-cell recognition

L1分子首先在小鼠的Broin中被描述为一种大的膜糖蛋白。L1参与神经元之间的钙非依赖性细胞黏附，与钙粘蛋白不同，钙粘附素是一类钙依赖性黏附分子。这些分子与轴突生长、生长锥体导向、轴突丛生、神经元迁移和髓鞘形成等事件密切相关。这些分子的所有相互作用都可能触发细胞内事件，包括钙浓度的变化，然后是上述功能的表达。虽然L1的一些结合特性已经被表征，但粘连的细胞内后果在很大程度上仍不清楚。L1的完整形式是免疫球蛋白超家族的一个200 KDa的大分子。它含有6个Ig结构域和5个纤维连接蛋白III型结构域。我们测定了大鼠L1基因的全序列，并对其功能进行了分析。用聚合酶链式反应方法检测完整L1及其异构体的分布。虽然大鼠和小鼠的脑中只含有完整的L1，但在它们的坐骨神经中发现了短暂的L1。短型L1是由L1mRNA的选择性剪接形成的。在细胞内缺失的四个氨基酸片段中包含两个可能被酪蛋白激酶II和I磷酸化的位点，这表明L1功能发生了变化。

The L1 molecule was first described in the mouse broin as a large membrane glycoprotein. L1 is involved in Ca^<+1>-independent cell adhesion between neurons, in Contrast to the Cadherins, afamily of molecules for Ca^<+1>-dependent adhesion. These molecules have keen implicated in such events as neurite outgrowth, growth Cone guidance, axonal fasciculation, neuroral migration, and myelination. The all interactions of the molecules maytrigger intracellular events, including chages in Calcium Concentration, followed by expression of the functions described above. While some binding properties of L1 have been characterized, the intracellular consequences of adhesion have remained largely Unknown. The complete form of L1 is a large 200KDa molecule of the Ig Superfamily. It contains six Ig domains and five fibronectin type III demains. We determined the complete sequence of rat L1 and analyzed the functions by transfectants. We examined the distribution of Complete L1 and its isoform by PCR methods. while rat and mouse brains contained only the complete form L1, the short isoformot L1 is found in their sciatic nerves. The short form L1 is formed by alternative splicing of L1 mRNA.The deletion segmentot four avnino oeids in the intra cellular dowair contains two possible phosohorylation sites by casein kinase II and I,suggesting a change of L1 function.