Heiland P C, Griffith L S, Lange R, Schachner M, Hertlein B, Traub O, Schmitz B
Department of Biochemistry, Institute of Animal Anatomy and Physiology, University of Bonn, Germany.
Eur J Cell Biol. 1998 Feb;75(2):97-106. doi: 10.1016/S0171-9335(98)80052-6.
We have previously shown that a cis interaction between the cell adhesion molecules L1 and NCAM is mediated by N-linked oligomannosidic glycans carried by L1 and that this L1/NCAM association is involved in basal neurite outgrowth from early postnatal cerebellar neurons of mouse brain [R. Horstkorte et al., J. Cell Biol. 121, 1409-1421 (1993)]. Extending these earlier studies we investigated signal transduction mechanisms elicited by this molecular interaction. We show here that phosphorylation of L1 is reduced concomitant with reduced neurite outgrowth when the L1/NCAM interaction is inhibited by oligomannosidic glycopeptides. Similarly, when a peptide of the 4th immunoglobulin (Ig)-like domain of NCAM - representing part of NCAM's carbohydrate-binding site - was added to the culture medium of the cells, neurite outgrowth and phosphorylation of L1 was strongly reduced. No effect on neurite outgrowth and phosphorylation of L1 was observed when cells were maintained in the presence of a peptide comprising part of the 1st Ig-like domain of NCAM or in the presence of the peptide encoded by the variable alternative spliced exon (VASE), which is also located in the 4th Ig-like domain of NCAM. Furthermore, phosphorylation of tyrosine and serine residues of L1 is reduced when the L1/NCAM interaction at the cell surface of cerebellar neurons is perturbed. Our observations suggest that a signal transduction mechanism is implicated in basal neurite outgrowth in which both tyrosine and serine phosphorylation of L1 represent a possible proximal step. Some of these results were presented at the International Glycoconjugate Symposium in Seattle, USA [P. C. Heiland et al., Glycoconj. J. 12, 521(1995)].
我们之前已经表明，细胞黏附分子L1和NCAM之间的顺式相互作用是由L1携带的N-连接寡甘露糖聚糖介导的，并且这种L1/NCAM关联参与了小鼠脑产后早期小脑神经元的基础神经突生长[R. Horstkorte等人，《细胞生物学杂志》121, 1409 - 1421(1993)]。扩展这些早期研究，我们研究了这种分子相互作用引发的信号转导机制。我们在此表明，当L1/NCAM相互作用被寡甘露糖糖肽抑制时，L1的磷酸化伴随着神经突生长的减少而降低。同样，当将代表NCAM碳水化合物结合位点一部分的NCAM第4个免疫球蛋白（Ig）样结构域的肽添加到细胞培养基中时，L1的神经突生长和磷酸化被强烈降低。当细胞在包含NCAM第1个Ig样结构域一部分的肽存在下或在由可变交替剪接外显子（VASE）编码的肽存在下培养时，未观察到对L1的神经突生长和磷酸化有影响，该可变交替剪接外显子也位于NCAM的第4个Ig样结构域中。此外，当小脑神经元细胞表面的L1/NCAM相互作用受到干扰时，L1的酪氨酸和丝氨酸残基的磷酸化会降低。我们的观察结果表明，一种信号转导机制与基础神经突生长有关，其中L1的酪氨酸和丝氨酸磷酸化都代表了一个可能的近端步骤。这些结果中的一些已在美国西雅图举行的国际糖缀合物研讨会上展示[P. C. Heiland等人，《糖缀合物杂志》12, 521(1995)]。
