Tyrosine phosphorylation mediates both activation and downmodulation of the biological activity of Vav
Tyrosine phosphorylation mediates both activation and downmodulation of the biological activity of Vav
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DOI：
10.1128/mcb.20.5.1678-1691.2000
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发表时间：
2000-03-01
影响因子：
5.3
通讯作者：
Bustelo, XR
中科院分区：
文献类型：
--
作者：
López-Lago, M;Lee, K;Bustelo, XR
Vav作为Rac GTP酶的GDP/GTP交换因子起作用，从而促进这些蛋白质从非活性（GDP结合）转变为活性（GTP结合）状态。细胞信号传导过程中Vav交换活性的刺激由酪氨酸磷酸化介导。为了了解磷酸化在调节Vav活性中的作用，我们已经开始了对信号转导过程中磷酸化的Vav残基的表征。在这里，我们表明，在这些残基之一，Y174的Y-F突变，导致Vav的致癌激活和增强其他Vav介导的信号，如细胞骨架重组，JNK激活，并刺激活化的T细胞的核因子。由Y174 F突变诱导的效应通过残基Y142或Y160中的突变进一步加强。Y174 F突变在体外对Vav的交换活性没有影响，但在体内导致更高水平的磷酸化。使用磷酸特异性抗体，我们发现，Y174是磷酸化的刺激后，促有丝分裂和抗原受体。这种磷酸化事件在Vav家族的另外两个成员Vav-2和Vav-3中是保守的。这些结果确定了一个以前未知的致癌激活的Vav的机制，并表明，该交换因子的活性是由两个拮抗磷酸化事件，一个参与Vav激活和第二个涉及Vav失活调制。
Vav works as a GDP/GTP exchange factor for Rac GTPases, thereby facilitating the transition of these proteins from the inactive (GDP-bound) into the active (GTP-bound) state. The stimulation of Vav exchange activity during cell signaling is mediated by tyrosine phosphorylation. To understand the roles of phosphorylation in the regulation of Vav activity, we have initiated the characterization of the residues of Vav that are phosphorylated during signal transduction. Here we show that a Y-to-F mutation in one of these residues, Y174, leads to the oncogenic activation of Vav and to the enhancement of other Vav-mediated signals such as those for cytoskeletal reorganization, JNK activation, and stimulation of the nuclear factor of activated T cells. The effect induced by the Y174F mutation is further accentuated by mutations in residue Y142 or Y160. The Y174F mutation has no effect on the exchange activity of Vav in vitro but results in higher levels of phosphorylation in vivo. Using a phosphospecific antibody, we found that Y174 is phosphorylated following stimulation of mitogenic and antigenic receptors. This phosphorylation event is conserved in Vav-2 and Vav-3, the other two members of the Vav family. These results identify a previously unknown mechanism for the oncogenic activation of Vav and suggest that the activity of this exchange factor is modulated by two antagonistic phosphorylation events, one involved in Vav activation and a second one implicated in Vav inactivation.