Clary D O, Reichardt L F
Department of Physiology, University of California, San Francisco 94143.
Proc Natl Acad Sci U S A. 1994 Nov 8;91(23):11133-7. doi: 10.1073/pnas.91.23.11133.
TrkA, a member of the receptor tyrosine kinase family, binds nerve growth factor (NGF) and subsequently activates intracellular signaling pathways. Previous studies have found variable and weak interaction of the TrkA receptor with neurotrophin 3 (NT-3), another member of the NGF family. TrkA is expressed in two splice forms, differing in the presence of an 18-bp exon in the extracellular domain. The biological responses of each isoform of the TrkA receptor were tested after transfection into the cell line PC12nnr5, a variant of PC12 cells lacking functional TrkA protein. NGF was found to activate each form of the receptor comparably. However, the TrkA isoform containing the variable exon showed significantly higher activation by NT-3, which was detected by stimulation of TrkA autophosphorylation, induction of ZIF268 transcription, and cellular differentiation. Function-perturbing antibodies to the p75 low-affinity NGF receptor potentiated the NT-3 responses of both forms of TrkA in the transfected PC12nnr5 cell lines, suggesting that the low-affinity NGF receptor suppresses the ability of TrkA to respond to NT-3.
TrkA是受体酪氨酸激酶家族的成员之一，可结合神经生长因子（NGF），随后激活细胞内信号通路。先前的研究发现，TrkA受体与NGF家族的另一个成员神经营养因子3（NT-3）之间存在可变且微弱的相互作用。TrkA以两种剪接形式表达，它们在细胞外结构域中一个18个碱基对的外显子的存在情况上有所不同。将TrkA受体的每种异构体转染到PC12nnr5细胞系（一种缺乏功能性TrkA蛋白的PC12细胞变体）中后，对其生物学反应进行了测试。发现NGF对受体的每种形式的激活程度相当。然而，含有可变外显子的TrkA异构体对NT-3的激活明显更高，这通过刺激TrkA自身磷酸化、诱导ZIF268转录和细胞分化得以检测。针对p75低亲和力NGF受体的功能干扰抗体增强了转染的PC12nnr5细胞系中两种形式的TrkA对NT-3的反应，这表明低亲和力NGF受体抑制了TrkA对NT-3的反应能力。
