Department of Biochemistry, Boston University School of Medicine, Boston, MA 02118, USA.
J Cell Physiol. 2012 May;227(5):2013-21. doi: 10.1002/jcp.22929.
The angiotensin II (AngII) type I receptor (AT1) was modified by replacing its third intracellular loop and C-terminal tail with the corresponding regions from the bradykinin B2 receptor. Transgenic mice were produced that overexpress this mutated receptor (AB3T). Considerably less collagen content in the intact aorta and in primary aortic smooth muscle cells (aSMCs) cultures was observed in the transgenic mice. On the other hand, elastin content remained unchanged as measured by Western blot, and insoluble amino acid quantitation. The contraction of isolated aortas also remained unaltered. The aSMCs derived from the transgenic mice showed a reduction in AngII responsive type I collagen production. In aSMCs from transgenic mice, the cascade of Akt to the mammalian target rapamycin (mTOR) to p70 S6 kinase (p70S6K) was not AngII activated, while in the aSMCs from wild-type (WT) mice the cascade was AngII activated. Angiotensin activation of Smad2 and Stat3 was also reduced in the AB3T aSMCs. However, no change in the effect of transforming growth factor β (TGFβ) on type I collagen production was observed. Also, the activation of ERK and JNK and G-protein linked signaling remained unaltered in response to AngII. Akt and PI3K activation inhibitors blocked AngII-stimulated type I collagen expression in WT aSMCs, whereas ERK inhibitor had no such effect. Our results point to an Akt/mTOR/p70S6K regulation of collagen production by AngII with participation of Smad2 and Stat3 cascades in this process.
血管紧张素 II（AngII）I 型受体（AT1）通过替换其第三细胞内环和 C 末端尾巴，与缓激肽 B2 受体的相应区域进行了修饰。生产了过度表达这种突变受体（AB3T）的转基因小鼠。在转基因小鼠中，完整主动脉和原代主动脉平滑肌细胞（aSMCs）培养物中的胶原含量明显减少。另一方面，通过 Western blot 和不溶性氨基酸定量，弹性蛋白含量保持不变。分离的主动脉的收缩也保持不变。源自转基因小鼠的 aSMCs 显示出 AngII 反应性 I 型胶原蛋白产生减少。在源自转基因小鼠的 aSMCs 中，Akt 到哺乳动物靶标雷帕霉素（mTOR）到 p70 S6 激酶（p70S6K）的级联反应不受 AngII 激活，而在源自野生型（WT）小鼠的 aSMCs 中，级联反应受 AngII 激活。AB3T aSMCs 中的 AngII 激活 Smad2 和 Stat3 也减少。然而，转化生长因子β（TGFβ）对 I 型胶原蛋白产生的影响没有变化。此外，AngII 反应性 ERK 和 JNK 和 G 蛋白偶联信号的激活仍然不变。Akt 和 PI3K 激活抑制剂阻断了 WT aSMCs 中 AngII 刺激的 I 型胶原蛋白表达，而 ERK 抑制剂则没有这种作用。我们的结果表明，Akt/mTOR/p70S6K 调节 AngII 诱导的胶原蛋白产生，该过程涉及 Smad2 和 Stat3 级联反应。
