Beggs H E, Baragona S C, Hemperly J J, Maness P F
Department of Biochemistry, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599-7260, USA.
J Biol Chem. 1997 Mar 28;272(13):8310-9. doi: 10.1074/jbc.272.13.8310.
Axonal growth cones respond to adhesion molecules and extracellular matrix components by rapid morphological changes and growth rate modification. Neurite outgrowth mediated by the neural cell adhesion molecule (NCAM) requires the src family tyrosine kinase p59(fyn) in nerve growth cones, but the molecular basis for this interaction has not been defined. The NCAM140 isoform, which is found in migrating growth cones, selectively co-immunoprecipitated with p59(fyn) from nonionic detergent (Brij 96) extracts of early postnatal mouse cerebellum and transfected rat B35 neuroblastoma and COS-7 cells. p59(fyn) did not associate significantly with the NCAM180 isoform, which is found at sites of stable neural cell contacts, or with the glycophosphatidylinositol-linked NCAM120 isoform. pp60(c-)src, a tyrosine kinase that promotes neurite growth on the neuronal cell adhesion molecule L1, did not interact with any NCAM isoform. Whereas p59(fyn) was constitutively associated with NCAM140, the focal adhesion kinase p125(fak), a nonreceptor tyrosine kinase known to mediate integrin-dependent signaling, became recruited to the NCAM140-p59(fyn) complex when cells were reacted with antibodies against the extracellular region of NCAM. Treatment of cells with a soluble NCAM fusion protein or with NCAM antibodies caused a rapid and transient increase in tyrosine phosphorylation of p125(fak) and p59(fyn). These results suggest that NCAM140 binding interactions at the cell surface induce the assembly of a molecular complex of NCAM140, p125(fak), and p59(fyn) and activate the catalytic function of these tyrosine kinases, initiating a signaling cascade that may modulate growth cone migration.
轴突生长锥通过快速的形态变化和生长速率改变对黏附分子和细胞外基质成分做出反应。神经细胞黏附分子（NCAM）介导的神经突生长需要神经生长锥中的src家族酪氨酸激酶p59^（fyn），但这种相互作用的分子基础尚未明确。在迁移生长锥中发现的NCAM140异构体，可从出生后早期小鼠小脑的非离子去污剂（Brij 96）提取物以及转染的大鼠B35神经母细胞瘤和COS-7细胞中与p59^（fyn）选择性地共免疫沉淀。p59^（fyn）与在稳定神经细胞接触部位发现的NCAM180异构体或糖基磷脂酰肌醇连接的NCAM120异构体没有明显关联。pp60^（c-src）是一种促进神经突在神经元细胞黏附分子L1上生长的酪氨酸激酶，它不与任何NCAM异构体相互作用。虽然p59^（fyn）与NCAM140组成性结合，但黏着斑激酶p125^（fak），一种已知介导整合素依赖性信号传导的非受体酪氨酸激酶，当细胞与针对NCAM细胞外区域的抗体反应时，会被招募到NCAM140 - p59^（fyn）复合物中。用可溶性NCAM融合蛋白或NCAM抗体处理细胞会导致p125^（fak）和p59^（fyn）的酪氨酸磷酸化迅速且短暂增加。这些结果表明，细胞表面的NCAM140结合相互作用诱导了NCAM1
