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

L1分子首次在小鼠脑组织中被描述为一个大的膜糖蛋白。L1参与了不依赖Ca^<+1>的神经元之间的细胞粘附，这与钙粘蛋白不同，钙粘蛋白是依赖Ca^<+1>的分子家族。这些分子与神经突生长、生长锥引导、轴突束化、神经口迁移和髓鞘形成等事件密切相关。所有分子的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的一些结合特性已经被表征，但粘附在细胞内的影响在很大程度上仍然未知。L1的完整形式是一个大的200KDa的Ig超家族分子。它包含6个Ig结构域和5个III型纤维连接蛋白残基。我们确定了大鼠L1的完整序列，并通过转染分析了其功能。我们用PCR方法检测了完整L1及其异构体的分布。而大鼠和小鼠的大脑只含有完整形式的L1，在它们的坐骨神经中发现了短的同形L1。短形式L1是由L1 mRNA的选择性剪接形成的。细胞内4个avinoids的缺失片段包含两个可能被酪蛋白激酶II和I磷酸化的位点，表明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.