Dissecting the thrombopoietin receptor: Functional elements of the Mpl cytoplasmic domain
Dissecting the thrombopoietin receptor: Functional elements of the Mpl cytoplasmic domain
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DOI：
10.1073/pnas.94.6.2350
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发表时间：
1997-03-18
影响因子：
11.1
通讯作者：
Kaushansky, K
中科院分区：
文献类型：
--
作者：
Drachman, JG;Kaushansky, K
血小板生成素（TPO）通过其受体Mp1刺激巨核细胞及其祖细胞的增殖和成熟，Mp1细胞质结构域通过各种受体对接位点的活性信号复合物的组装来控制这一过程。我们测试了8个121-aa小鼠Mp1细胞质结构域的羧基截断是否能够支持细胞因子依赖性细胞系（Ba/F3）的生长，以及它们是否能够诱导tpo刺激的特定信号蛋白的酪氨酸磷酸化，随后使用受体细胞质结构域的5个酪氨酸残基的点突变来证实这一点。从这些研究中，我们证明：(i) tpo诱导的增殖被截断多达53个Mp1的c端氨基酸，包括受体酪氨酸磷酸化位点，从而适度减少；（ii） Mp1细胞质结构域69-83残基的截断/突变增强了增殖信号，可能是由受体驱动的细胞分化减少介导的；（iii） Mp1可以在Y112或Y117位点磷酸化，但不能在近端胞质三个酪氨酸残基（Y8、Y29和Y78）磷酸化；（iv） Mp1的Y112对于She和She相关的p145的酪氨酸磷酸化是必需的（SHIP）；(v)与STAT3不同，STAT5在Mp1胞质结构域中没有任何酪氨酸残基的情况下被部分磷酸化。这些研究发现Mp1的亚结构域是激活几个关键信号通路所必需的，并指出了tpo诱导的信号转导的两种潜在的新机制，一种是STAT5激活的间接途径，另一种是通过限制增殖起作用的分化结构域。
Thrombopoietin (TPO) acts through its receptor, Mp1, to stimulate the proliferation and maturation of megakaryocytes and their progenitors, The Mp1 cytoplasmic domain controls this process through assembly of an active signaling complex using various receptor docking sites, In this report, eight carboxyl truncations of the 121-aa murine Mp1 cytoplasmic domain were tested for the ability to support growth of a cytokine-dependent cell line (Ba/F3) and for their capacity to induce TPO-stimulated tyrosine phosphorylation of specific signaling proteins, Point mutations of the five tyrosine residues in the cytoplasmic domain of the receptor were subsequently used to confirm out. conclusions, From these studies we demonstrate that: (i) TPO-induced proliferation is moderately reduced by truncation of as many as 53 C-terminal amino acids of Mp1, including the sites of receptor tyrosine phosphorylation; (ii) truncation/mutation of residues 69-83 of the Mp1 cytoplasmic domain enhances proliferative signaling, perhaps mediated by a decrease in receptor-driven cellular differentiation; (iii) Mp1 can he phosphorylated at either Y112 or Y117 but not at the three proximal cytoplasmic tyrosine residues (Y8, Y29, and Y78); (iv) Y112 of Mp1 is necessary for tyrosine phosphorylation of She and She-associated p145 (SHIP); and (v) unlike STAT3, STAT5 is partially phosphorylated in the absence of any tyrosine residues in the Mp1 cytoplasmic domain, These studies identify subdomains of Mp1 necessary for activation of several critical signaling pathways and point to two potentially novel mechanisms of TPO-induced signal transduction, an indirect pathway to STAT5 activation and a differentiation domain that acts by limiting proliferation.