Activation of the mitogen-activated protein kinase pathway by the erythropoietin receptor.
Activation of the mitogen-activated protein kinase pathway by the erythropoietin receptor.
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促红细胞生成素受体激活丝裂原激活蛋白激酶途径。
DOI：
10.1016/s0021-9258(18)43975-0
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发表时间：
1994
期刊：
影响因子：
--
通讯作者：
Nobuo Aoki
中科院分区：
文献类型：
--
作者：
Yasuko Miura;Osamu MiuraS;James;Ihle;Nobuo Aoki
促红细胞生成素受体（EpoR）属于细胞因子受体家族，其成员缺乏酪氨酸激酶结构域。然而，最近的研究表明，细胞质酪氨酸激酶JAK2与EpoR的细胞质结构域相互作用，并在Epo与受体结合后被激活。Epo还显示刺激Ras和Raf-1的活化。本研究旨在探讨Epo诱导的酪氨酸磷酸化是否参与Ras/丝裂原活化蛋白激酶（MAP激酶）通路的激活，并确定其对EpoR生长信号传导的意义。在表达转染的野生型EpoR、Epo或IL-3的白细胞介素（IL）-3依赖性细胞系中，诱导Shc的酪氨酸磷酸化及其与Grb2的结合。这些细胞因子还诱导酪氨酸磷酸化和MAP激酶亚型ERK 1和ERK 2的活化。具有108个氨基酸的羧基末端缺失的突变体EpoR（H突变体），其具有促有丝分裂功能，但在羧基末端区域中缺乏酪氨酸磷酸化位点，显示出诱导Shc的酪氨酸磷酸化和磷酸化并激活MAP激酶的能力显著降低。突变受体（PM4突变体）失活的点突变，Trp282到精氨酸，废除与JAK2的相互作用，未能诱导任何影响Shc或MAP激酶。在细胞表达的突变体EpoR是组成性激活的点突变，Arg129到Cys，在细胞外部分的受体，无论是酪氨酸磷酸化的Shc也不激活MAP激酶磷酸化是可检测的，没有刺激Epo或IL-3。这些结果表明，EpoR的羧基末端区域可能通过Ras信号通路在MAP激酶的激活中起着至关重要的作用，Ras信号通路可能被Shc的酪氨酸磷酸化及其与Grb2的结合所激活。然而，MAP激酶的激活未能与突变体EpoR的促有丝分裂活性相关，因此可能不需要从EpoR的生长信号。
The erythropoietin receptor (EpoR) belongs to the cytokine receptor family, members of which lack a tyrosine kinase domain. Recent studies, however, have shown that a cytoplasmic tyrosine kinase, JAK2, interacts with the cytoplasmic domain of the EpoR and becomes activated upon binding of Epo to the receptor. Epo has also been shown to stimulate activation of Ras and Raf-1. The present studies were undertaken to examine the possible involvement of Epo-induced tyrosine phosphorylation in activation of the Ras/mitogen-activated protein kinase (MAP kinase) pathway and to determine its significance on the growth signaling from the EpoR. In an interleukin (IL)-3-dependent cell line expressing the transfected wild-type EpoR, Epo, or IL-3 induced tyrosine phosphorylation of Shc and its association with Grb2. These cytokines also induced tyrosine phosphorylation and activation of MAP kinase isoforms ERK1 and ERK2. A mutant EpoR with a carboxyl-terminal deletion of 108 amino acids (H mutant), which is mitogenically functional but lacks tyrosine phosphorylation sites in the carboxyl-terminal region, showed markedly diminished abilities to induce tyrosine phosphorylation of Shc and to phosphorylate and activate MAP kinases. A mutant receptor (PM4 mutant) inactivated by a point mutation, Trp282 to Arg, which abrogates the interaction with JAK2, failed to induce any effect on Shc or MAP kinases. In cells expressing a mutant EpoR that is constitutively activated by a point mutation, Arg129 to Cys, in the extracellular portion of the receptor, neither tyrosine phosphorylation of Shc nor activation of MAP kinases by phosphorylation was detectable without stimulation with Epo or IL-3. These results suggest that the carboxyl-terminal region of EpoR may play a crucial role in activation of MAP kinases through the Ras signaling pathway which may be activated by tyrosine phosphorylation of Shc and its association with Grb2. The activation of MAP kinases, however, failed to correlate with the mitogenic activity of mutant EpoRs and thus may not be required for growth signaling from the EpoR.