Antiretroviral-Induced Defects in Muscle Protein Synthesis

描述(由申请人提供)：HIV-1蛋白酶抑制剂一般对脂肪和碳水化合物代谢有许多已知的影响。我们使用体内和体外模型系统的数据表明，吲哚那韦和洛比那韦都通过损害控制mRNA翻译的多个步骤而显著减少骨骼肌的蛋白质合成。该项目的长期目标是阐明洛匹那韦通过改变肌肉蛋白质平衡而导致肌病的机制。这项拟议的研究将检验的工作假设是，洛比那韦在基础条件下和对选定的合成代谢刺激的反应中，拮抗包括真核细胞起始因子(ELF)4F和elF2/2B在内的细胞生长信号系统。因此，洛匹那韦通过破坏帽依赖的翻译控制和43S预启动复合体的形成来改变蛋白质平衡。此外，洛匹那韦对肽链的延长也有不利影响。为了解决我们假设中隐含的问题，这项拟议的研究有以下具体目的：(1)阐明洛比那韦损害骨骼肌elF2B活性的机制；(2)确定mTOR(哺乳动物雷帕霉素靶标)营养信号复合体的变化是否导致洛比那韦诱导的4E-BP1磷酸化改变；(3)确定洛比那韦增加真核细胞延长因子(EEF)-2磷酸化的机制以及这种变化本身是否损害肽链延长本身；(4)阐明洛比那韦损害肌肉对营养信号(如亮氨酸)的正常合成代谢反应的机制；以及(5)确定介导齐多夫定(AZT)和拉米夫定(3TC)对洛匹那韦所致蛋白质合成减少的增强作用的生化位点。利用大鼠和培养的人类心肌细胞进行的互补性研究将被用来阐明洛比那韦降低骨骼肌翻译效率的机制，从而使人们更全面地了解这种艾滋病毒蛋白水解酶抑制剂单独以及与其他抗逆转录病毒药物联合使用所产生的代谢障碍。需要这样的数据才能充分发挥这种药物的潜力，并避免该药物在长期治疗艾滋病毒感染者方面可能出现的陷阱。

DESCRIPTION (provided by applicant): HIV-1 protease inhibitors in general have a number of known effects on lipid and carbohydrate metabolism. Our data using both in vivo and in vitro model systems indicate that both indinavir and lopinavir also markedly decrease protein synthesis in skeletal muscle by impairing multiple steps in the control of mRNA translation. The long-term goal of this project is to elucidate the mechanisms by which lopinavir produces myopathy by altering muscle protein balance. The working hypothesis to be tested by the proposed research is that lopinavir antagonizes cell growth signaling systems, that include both eukaryotic initiation factor (elF) 4F and elF2/2B, under both basal conditions and in response to selected anabolic stimuli. Thus, lopinavir alters protein balance by impairing cap-dependent translational control and the formation of the 43S pre-initiation complex. Further, lopinavir adversely effects peptide-chain elongation. To address the questions implicit in our hypothesis, the proposed research has the following Specific Aims: (1) Elucidate the mechanism by which lopinavir impairs elF2B activity in skeletal muscle; (2) Determine whether alterations in the mTOR (mammalian target of rapamycin) nutrient signaling complex are responsible for lopinavir-induced alterations in 4E-BP1 phosphorylation; (3) Determine the mechanism by which lopinavir increases eukaryotic elongation factor (eEF)-2 phosphorylation and whether this change impairs peptide-chain elongation per se; (4) Elucidate the mechanism by which lopinavir impairs the normal anabolic response to nutritional signals (e.g., leucine) in muscle; and (5) Identify the biochemical loci mediating the potentiating effect of zidovudine (AZT) and lamivudine (3TC) on the lopinavir-induced decrease in protein synthesis. Complementary studies using both rats and cultured human myocytes will be used to elucidate the mechanism by which skeletal muscle translation efficiency is reduced by lopinavir, thereby leading to a more complete understanding of the metabolic disturbances produced by this HIV protease inhibitor alone and in combination with other antiretroviral agents. Such data is needed to both realize the full potential and avoid possible pitfalls of this drug in the long-term treatment of HIV-infected individuals.