RAPAMYCIN SELECTIVELY INHIBITS ANGIOTENSIN-II-INDUCED INCREASE IN PROTEIN-SYNTHESIS IN CARDIAC MYOCYTES IN-VITRO - POTENTIAL ROLE OF 70-KD S6 KINASE IN ANGIOTENSIN-II-INDUCED CARDIAC-HYPERTROPHY
RAPAMYCIN SELECTIVELY INHIBITS ANGIOTENSIN-II-INDUCED INCREASE IN PROTEIN-SYNTHESIS IN CARDIAC MYOCYTES IN-VITRO - POTENTIAL ROLE OF 70-KD S6 KINASE IN ANGIOTENSIN-II-INDUCED CARDIAC-HYPERTROPHY
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DOI：
10.1161/01.res.77.6.1040
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发表时间：
1995-12-01
影响因子：
20.1
通讯作者：
IZUMO, S
中科院分区：
文献类型：
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作者：
SADOSHIMA, J;IZUMO, S
有人认为，40 S核糖体蛋白S6的磷酸化调节蛋白质合成。已经鉴定了两个不同的S6激酶家族，rsk编码的85-至99-kD S6激酶（RSK）和70-或85-kD SG激酶（p70（S6 K））。我们以前已经表明，肥大刺激，如血管紧张素II（Ang II），迅速激活RSK在心肌细胞。然而，RSK和p70（S6 K）由不同的机制调节，并且p70（S6 K），而不是RSK，是其他细胞类型中体内的生理S6激酶。使用培养的新生大鼠心室肌细胞，我们检查是否血管紧张素II激活p70（S6 K），并研究了雷帕霉素，一种有效的但间接的抑制剂p70（S6 K），对血管紧张素II诱导的肥大反应的影响。免疫印迹分析表明，心肌细胞表达70和85 kD形式的p70（S6 K）。Ang II通过I型Ang II受体引起p70（S6 K）快速而持续的激活。雷帕霉素以剂量依赖性方式抑制Ang II诱导的p70（S6 K）激活，IC 50为0.14 ng/mL（0.15 nmol/L）。雷帕霉素不抑制血管紧张素II诱导的酪氨酸激酶、丝裂原活化蛋白激酶、RSK和蛋白激酶C的活化。雷帕霉素的作用不太可能通过其对p34（cdc 2）和p33（cdh）2的作用来介导，因为Ang II在心肌细胞中不激活这些细胞周期依赖性激酶。相反，雷帕霉素对p70（S6 K）的剂量依赖性抑制与其对Ang II诱导的蛋白质合成增加的抑制密切相关。有趣的是，雷帕霉素并不影响Ang II诱导的特定基因表达的激活，包括即刻早期基因c-fos和胎儿型基因，如心房钠尿排泄因子和骨骼α-肌动蛋白。此外，雷帕霉素没有抑制血管紧张素II诱导的表型变化在蛋白质水平上，如增加心房钠尿素分泌，β-肌球蛋白重链的表达，肌动蛋白组织成肌节单位。这些结果表明，p70（S6 K）被激活的血管紧张素II和雷帕霉素敏感的信号传导机制，最有可能的p70（S6 K），在血管紧张素II诱导的增加在所有的蛋白质合成，但不是在血管紧张素II诱导的心肌细胞的特定表型的变化中起着至关重要的作用。
It has been suggested that phosphorylation of a 40S ribosomal protein, S6, regulates protein synthesis. Two distinct families of S6 kinase have been identified, the rsk-encoded 85- to 99-kD S6 kinase (RSK) and the 70- or 85-kD SG kinase (p70(S6K)). We have previously shown that hypertrophic stimuli, such as angiotensin II (Ang II), rapidly activate RSK in cardiac myocytes. However, RSK and p70(S6K) are regulated by distinct mechanisms, and p70(S6K), but not RSK, is the physiological S6 kinase in vivo in other cell types. Using cultured neonatal rat ventricular myocytes, we examined whether Ang II activates p70(S6K) and investigated the effect of rapamycin, a potent yet indirect inhibitor of p70(S6K), On the Ang II-induced hypertrophic response. Immunoblot analyses indicate that car diac myocytes express the 70- and 85-kD forms of p70(S6K). Ang II caused a rapid and sustained activation of p70(S6K) through the type I Ang II receptor. Rapamycin inhibited Ang II-induced activation of p70(S6K) in a dose-dependent manner, with an IC50 of 0.14 ng/mL (0.15 nmol/L). Rapamycin did not inhibit Ang II-induced activation of tyrosine kinase, mitogen-activated protein kinase, RSK, and protein kinase C. The effect of rapamycin is unlikely to medicated by its effect on p34(cdc2) and p33(cdh)2 because Ang II did not activate these cell cycle-dependent kinases in cardiac myocytes. In contrast, a dose-dependent inhibition of p70(S6K) by rapamycin is very closely correlated with its inhibition of the Ang II-induced increase in protein synthesis. Interestingly, rapamycin did not affect the Ang II-induced activation of specific Gene expression, including the immediate-early gene c-fos and fetal type Genes, such as atrial natriurtetic factor and skeletal alpha-actin. Moreover, rapamycin did not suppress Ang II-induced phenotypic changes at the protein level, such as increased atrial natriurctic factor secretion, expression of beta-myosin heavy chain, and organization of actin into sarcomeric units. These results indicate that p70(S6K) is activated by Ang ii and that a rapamycin-sensitive signaling mechanism, most likely p70(S6K), plays an essential role in the Ang II-induced increase In over all protein synthesis but not in Ang II-induced specific phenotypic changes in cardiac myocytes.