Fyn Tyrosine Kinase Regulates the Surface Expression of Glycosylphosphatidylinositol-linked Ephrin via the Modulation of Sphingomyelin Metabolism
Fyn Tyrosine Kinase Regulates the Surface Expression of Glycosylphosphatidylinositol-linked Ephrin via the Modulation of Sphingomyelin Metabolism
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DOI：
10.1074/jbc.m809401200
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发表时间：
2009-04-03
影响因子：
4.8
通讯作者：
Hattori, Mitsuharu
中科院分区：
文献类型：
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作者：
Baba, Atsushi;Akagi, Koshiro;Hattori, Mitsuharu
糖基磷脂酰肌醇连接的ephrin - A在多种生物学事件中发挥重要作用，例如神经元发育和免疫反应。由于ephrin - A的表面数量在这些事件中至关重要，因此ephrin - A的运输必然受到细胞内机制的调控。特别是，Src家族蛋白酪氨酸激酶调控几种膜分子的细胞内运输，并在ephrin - A的下游发挥作用；然而，它们是否影响ephrin - A的运输仍未被探究。在此，我们报道Src家族蛋白酪氨酸激酶（特别是Fyn）的活性负向调控ephrin - A的细胞表面数量。组成型激活的Fyn的表达降低了ephrin - A的表面数量。相反，显性失活Fyn的表达或应用Src家族抑制剂会增加ephrin - A2的表面数量。ephrin - A的细胞总量与其表面数量呈负相关，这表明ephrin - A在细胞内区室中更稳定。组成型激活的Fyn的表达增加了质膜上鞘磷脂簇的数量，而抑制Fyn则会减少其数量。此外，抑制鞘磷脂合成会极大地增加ephrin - A的表面数量。总之，这些结果表明Fyn通过调节鞘磷脂的代谢来调控ephrin - A的表面数量，鞘磷脂可能抑制了ephrin - A从内体到质膜的运输。此处描述的信号级联可能作为ephrin - A功能的负反馈回路的一部分发挥作用。
Glycosylphosphatidylinositol-linked ephrin-As play important roles in various biological events, such as neuronal development and immune responses. Because the surface amount of ephrin-As is critical in these events, the trafficking of ephrin-As must be regulated by intracellular machinery. In particular, Src family protein-tyrosine kinases regulate the intracellular trafficking of several membrane molecules and act downstream of ephrin-As; whether they affect the trafficking of ephrin-As, however, has remained unexplored. Here, we report that the activity of Src family protein-tyrosine kinases, particularly Fyn, negatively regulates the cell-surface amount of ephrin-As. The expression of constitutively active Fyn decreases the surface amount of ephrin-As. Conversely, the expression of dominant-negative Fyn or the application of a Src-family inhibitor increases the surface amount of ephrin-A2. The total cellular amount of ephrin-A is inversely correlated with its amount on the surface, suggesting that ephrin-As are more stable in the intracellular compartment. The expression of constitutively active Fyn increases the amount of sphingomyelin clusters on the plasma membrane, whereas inhibiting Fyn decreases it. Moreover, the inhibition of sphingomyelin synthesis greatly increases the surface amount of ephrin-As. Altogether, these results suggest that Fyn regulates the surface amount of ephrin-As by modulating the metabolism of sphingomyelin, which presumably inhibits the trafficking of ephrin-As from endosomes to the plasma membrane. The signaling cascade described here may function as part of the negative feedback loop of ephrin-A function.