Respiratory Diseases Research Center, Department of Respiratory Medicine, The Second Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an, Shaanxi, PR China.
FEBS Lett. 2012 Nov 2;586(21):3888-93. doi: 10.1016/j.febslet.2012.08.036. Epub 2012 Oct 3.
Endothelin-1 (ET-1) dose-dependently increased HIF1α expression in pulmonary artery smooth muscle cells (PASMCs). Inhibition of protein synthesis did not affect ET-1-induced HIF1α expression. The maximum effect of ET-1 was similar to that caused by proteasome inhibitor MG132. Further study indicates that ET-1 also dose-dependently stimulated calcineurin activation, specific calcineurin inhibitor cyclosporine A (CsA), abolished ET-1-induced HIF1α elevation, and reversed ET-1-induced RACK1 (receptor of activated protein kinase C 1) de-phosphorylation. Endothelin receptor A was found to specifically mediate the effects of ET-1. To examine whether RACK1 is particularly involved in proteasome-dependent HIF1α degradation, RACK1 was silenced by siRNA transfection. Cells lacking RACK1 exhibited significant elevation of HIF1α protein level. Taken together, our study suggests that ET-1 suppressed proteasome-dependent HIF1α degradation by calcineurin-dependent RACK1 de-phosphorylation.
内皮素-1（ET-1）可剂量依赖性地增加肺动脉平滑肌细胞（PASMCs）中的 HIF1α 表达。蛋白质合成的抑制作用不影响 ET-1 诱导的 HIF1α 表达。ET-1 的最大作用与蛋白酶体抑制剂 MG132 引起的作用相似。进一步的研究表明，ET-1 还可剂量依赖性地刺激钙调神经磷酸酶的激活，特异性钙调神经磷酸酶抑制剂环孢菌素 A（CsA）可消除 ET-1 诱导的 HIF1α 升高，并逆转 ET-1 诱导的 RACK1（蛋白激酶 C 激活受体 1）去磷酸化。发现内皮素受体 A 特异性介导 ET-1 的作用。为了研究 RACK1 是否特别参与蛋白酶体依赖性 HIF1α 降解，我们通过 siRNA 转染沉默 RACK1。缺乏 RACK1 的细胞 HIF1α 蛋白水平显著升高。总之，我们的研究表明，ET-1 通过钙调神经磷酸酶依赖性 RACK1 去磷酸化抑制蛋白酶体依赖性 HIF1α 降解。
