de Pablo Yolanda, Pérez-García M José, Georgieva Maya V, Sanchis Daniel, Lindqvist Niclas, Soler Rosa M, Comella Joan X, Llovera Marta
Cell Signaling and Apoptosis Group, Department Ciències Mèdiques Bàsiques, IRBLLEIDA, Lleida, Spain.
J Neurochem. 2008 Jan;104(1):124-39. doi: 10.1111/j.1471-4159.2007.05027.x.
Tropomyosin-related kinase A (TrkA) receptor mediates the effects exerted by nerve growth factor on several subpopulations of neuronal cells. Ligand binding to TrkA induces receptor autophosphorylation on several tyrosine residues and the activation of signaling cascades. In this study, we describe a new site relevant for TrkA regulation, the tyrosine 701 (Y701), which is important for receptor trafficking and activation. Y701 replacement by aspartate or phenylalanine reduces receptor internalization rate and decreases the colocalization and association of TrkA with clathrin heavy chain, demonstrating that Y701 constitutes a YxxPhi (YRKF701-704) trafficking motif relevant for the regulation of receptor endocytosis. In accordance with this hypothesis, the colocalization of Y701 mutant receptors with a lysosomal marker is also reduced giving support to the involvement of the YRKF701-704 motif in the lysosomal targeting of TrkA receptors. Contrary to what was expected, substitution of Y701 for an Asp in order to mimic phosphorylation, impairs TrkA ability to mediate nerve growth factor-induced differentiation, although the mutant receptor retains its in vitro kinase activity. This is the first evidence that a Tyr residue can simultaneously regulate TrkA receptor trafficking and activity.
原肌球蛋白相关激酶A（TrkA）受体介导神经生长因子对几种神经元细胞亚群的作用。配体与TrkA结合会诱导受体在多个酪氨酸残基上发生自身磷酸化，并激活信号级联反应。在本研究中，我们描述了一个与TrkA调节相关的新位点，即酪氨酸701（Y701），它对受体转运和激活很重要。用天冬氨酸或苯丙氨酸取代Y701会降低受体内化率，并减少TrkA与网格蛋白重链的共定位和结合，这表明Y701构成了一个与受体胞吞作用调节相关的YxxPhi（YRKF701 - 704）转运基序。根据这一假设，Y701突变受体与溶酶体标记物的共定位也会减少，这支持了YRKF701 - 704基序参与TrkA受体的溶酶体靶向作用。与预期相反，用天冬氨酸取代Y701以模拟磷酸化，会损害TrkA介导神经生长因子诱导分化的能力，尽管突变受体保留了其体外激酶活性。这是第一个表明酪氨酸残基可同时调节TrkA受体转运和活性的证据。
