Regulation of luteinizing hormone-releasing hormone receptor binding by heterologous and autologous receptor-stimulated tyrosine phosphorylation.
Regulation of luteinizing hormone-releasing hormone receptor binding by heterologous and autologous receptor-stimulated tyrosine phosphorylation.
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通过异源和自体受体刺激的酪氨酸磷酸化调节黄体生成素释放激素受体的结合。
DOI：
10.1073/pnas.88.6.2244
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发表时间：
1991
影响因子：
11.1
通讯作者：
Schally,AV
中科院分区：
文献类型：
--
作者：
Liebow,C;Lee,MT;Kamer,AR;Schally,AV
胰腺癌过度表达酪氨酸激酶和促黄体生成激素释放激素（LH-RH）受体（LH-RHR）介导的酪氨酸磷酸酶。LH-RHR是一种60 kDa的蛋白质。表皮生长因子（EGF）刺激的酪氨酸激酶活性和LH-RH和生长抑素刺激的酪氨酸磷酸酶活性的底物之一也是60 kDa蛋白。这表明酪氨酸磷酸酶和酪氨酸激酶对LH-RHR的调节可能是由现有LH-RHR的磷酸化（去磷酸化）介导的。为了验证这一假设，将MIA PaCa-2细胞（一种人去分化胰腺癌细胞系）的膜在没有激素（对照）或与0.1 μ M EGF或生长抑素类似物RC-160的情况下在4 ℃下孵育1小时，以磷酸化60 kDa蛋白。通过用非放射性配体置换I125标记的[D-Trp 6]LH-RH的竞争结合实验表明，与对照组相比，EGF增加了69%的点的LH-RH结合，RC-160降低了85%的点的LH-RH结合（n = 61;均具有显著性，P <0.001）。特异性结合发生改变，与EGF预孵育后增加50-150%，RC-160后减少60-70%。用EGF或RC-160预处理后，结合亲和力常数没有变化。这表明磷酸化调节LH-RH的结合，并且可以解释LH-RH应答的EGF上调和RC-160和LH-RH下调。
Pancreatic cancers overexpress tyrosine kinase and luteinizing hormone-releasing hormone (LH-RH) receptor (LH-RHR)-mediated tyrosine phosphatase. LH-RHR is a 60-kDa protein. One of the substrates of epidermal growth factor (EGF)-stimulated tyrosine kinase activity and LH-RH- and somatostatin-stimulated tyrosine phosphatase activity is also a 60-kDa protein. This suggests the possibility that LH-RHR regulation by tyrosine phosphatase and tyrosine kinase is mediated by (de)phosphorylation of existing LH-RHR. To test this hypothesis, membranes of MIA PaCa-2 cells, a human dedifferentiated pancreatic cancer cell line, were incubated without hormone (control) or with 0.1 microM EGF or somatostatin analogue RC-160 for 1 hr at 4 degrees C to phosphorylate the 60-kDa protein. Competition binding experiments with I125-labeled [D-Trp6]LH-RH by displacement with a nonradioactive ligand showed that the LH-RH binding in 69% of the points was increased by EGF and 85% was decreased by RC-160 compared with controls (n = 61; both significant, P less than 0.001). The specific binding was altered, increasing 50-150% after preincubation with EGF and decreasing 60-70% after RC-160. No change was seen in the binding affinity constant after pretreatment with EGF or RC-160. This shows that phosphorylation regulates binding of LH-RH and may explain the up-regulation by EGF and down-regulation by RC-160 and by LH-RH of the LH-RH response.