Role of reactive oxygen species in protein degradation in murine myotubes induced by proteolysis-inducing factor and angiotensin II
Role of reactive oxygen species in protein degradation in murine myotubes induced by proteolysis-inducing factor and angiotensin II
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DOI：
10.1016/j.cellsig.2007.04.003
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发表时间：
2007-08-01
影响因子：
4.8
通讯作者：
Tisdale，M. J.
中科院分区：
文献类型：
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作者：
Russell，S. T.;Eley，H.;Tisdale，M. J.
抗氧化剂丁基羟基甲苯和d-α-生育酚(10μM)可完全抑制蛋白分解诱导因子(PIF)和血管紧张素II(Ang II)对小鼠肌管蛋白质的降解，提示活性氧(ROS)的形成在此过程中起重要作用。PIF和Ang II均可引起肌管内ROS生成的快速和一过性增加，并遵循抛物线剂量-反应曲线，与总蛋白降解的剂量反应曲线相似。抗氧化剂通过抑制核因子-κB抑制蛋白(I-κB)的磷酸化及其随后的降解来抑制转录因子核因子-κB(NF-κB)的激活，从而减弱PIF和Ang II对泛素-蛋白酶体蛋白分解途径表达和活性的增加。PIF和Ang II产生的ROS均被二苯基碘(10μM)减弱，提示它是通过NADPH氧化酶系统介导的。胞浆磷脂酶A2、U-73122(5μM)和D609(200μM)的特异性抑制剂三氟乙酰花生四烯酸(10μM)、磷脂酶C的抑制剂和蛋白激酶C的高度特异性抑制剂Calphostin C(300 NM)也能抑制ROS的形成，这些都是NADPH氧化酶的已知激活剂。含有PKC显性负性突变体的肌管对PIF和Ang II均无促进ROS生成的作用。两种Rac1抑制剂W56(200μM)和NSC23766(10μM)也可减弱PIF和Ang II诱导的ROS生成和蛋白质降解。已知rac1在磷脂酰肌醇-3激酶(PI-3K)产物和NADPH氧化酶之间介导信号转导，而PI-3K的高选择性抑制剂LY24002(10μM)处理完全抑制PIF和Ang II引起的ROS生成和总蛋白降解，而失活类似物LY303511(100μM)则没有任何作用。在癌症恶病质的肌肉萎缩中，ROS的形成似乎很重要，因为用d-α-toCopherol(1 mg kg−1)治疗携带MAC16肿瘤的体重减轻的小鼠，可以减缓蛋白质的降解，增加骨骼肌的蛋白质合成。
The antioxidants butylated hydroxytoluene (BHT, 1 mM) and d-α-tocopherol (10 μM) completely attenuated protein degradation in murine myotubes in response to both proteolysis-inducing factor (PIF) and angiotensin II (Ang II), suggesting that the formation of reactive oxygen species (ROS) plays an important role in this process. Both PIF and Ang II induced a rapid and transient increase in ROS formation in myotubes, which followed a parabolic dose-response curve, similar to that for total protein degradation. Antioxidant treatment attenuated the increase in expression and activity of the ubiquitin–proteasome proteolytic pathway by PIF and Ang II, by preventing the activation of the transcription factor nuclear factor-κB (NF-κB), through inhibition of phosphorylation of the NF-κB inhibitor protein (I-κB) and its subsequent degradation. ROS formation by both PIF and Ang II was attenuated by diphenyleneiodonium (10 μM), suggesting that it was mediated through the NADPH oxidase system. ROS formation was also attenuated by trifluoroacetyl arachidonic acid (10 μM), a specific inhibitor of cytosolic phospholipase A2, U-73122 (5 μM) and D609 (200 μM), inhibitors of phospholipase C and calphostin C (300 nM), a highly specific inhibitor of protein kinase C (PKC), all known activators of NADPH oxidase. Myotubes containing a dominant-negative mutant of PKC did not show an increase in ROS formation in response to either PIF or Ang II. The two Rac1 inhibitors W56 (200 μM) and NSC23766 (10 μM) also attenuated both ROS formation and protein degradation induced by both PIF and Ang II. Rac1 is known to mediate signalling between the phosphatidylinositol-3 kinase (PI-3K) product and NADPH oxidase, and treatment with LY24002 (10 μM), a highly selective inhibitor of PI-3K, completely attenuated ROS production in response to both PIF and Ang II, and inhibited total protein degradation, while the inactive analogue LY303511 (100 μM) had no effect. ROS formation appears to be important in muscle atrophy in cancer cachexia, since treatment of weight losing mice bearing the MAC16 tumour with d-α-tocopherol (1 mg kg−1) attenuated protein degradation and increased protein synthesis in skeletal muscle.