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

L1分子首先在小鼠broin中被描述为一种大的膜糖蛋白。与钙依赖性粘附分子家族钙粘素（Cadherins）不同，L1参与神经元间的非钙依赖性细胞粘附。这些分子与神经突生长、生长锥引导、轴突成束、神经迁移和髓鞘形成等事件密切相关。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，随后是上述功能的表达。虽然L1的一些结合特性已被表征，但粘附的细胞内后果在很大程度上仍然未知。L1的完整形式是IG超家族的200 KDa大分子。它含有6个IG结构域和5个纤连蛋白III型结构域。我们测定了大鼠L1基因的全序列，并通过转染子分析了其功能。我们通过PCR方法检测了完全L1及其亚型的分布。虽然大鼠和小鼠脑仅含有完整形式的L1，但在它们的坐骨神经中发现了短的同种型L1。L1是由L1mRNA选择性剪接而成的，其胞内缺失的4个氨基酸残基中含有两个可能被酪蛋白激酶II和I磷酸化的位点，提示L1的功能发生了变化。

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.