Myocardial ischemic activation of the Akt pathway

描述（由申请人提供）：PI-3激酶/Akt通路是预处理提供的心脏保护的潜在介质。本提案的主要目的是鉴定由PI-3激酶/Akt通路激活的心脏保护末端效应器。热休克因子-1 （HSF-1）是一种启动热休克蛋白70 （HSP70）表达的转录因子，热休克蛋白70是一种与缺血预处理提供的心脏保护相关的分子伴侣。NFkB在缺血预处理中的作用也已得到证实。HSF-1和NFkB的激活受到GSK-3的负调控，这种调控被Akt磷酸化糖原合成酶激酶(GSK)-3b所消除。GSK-3在抑制HSF-1和NFkB中的相对作用将被确定。我们还将研究另一种Akt底物凋亡信号调节激酶1 （ASK1）。我们将确定Akt与ASK1的关联，以及随后Akt介导的ASK-1 Ser83位点磷酸化，负调控p38MAPK和Jun激酶的激活以及细胞凋亡的开始。这可能涉及ASK1与14-3-3蛋白的相互作用。我们还将研究Akt与小热休克蛋白HSP27之间的关系，HSP27作为Akt的支架蛋白。我们将确定HSP27与Akt联合促进Akt抗凋亡功能的能力。心肌缺血时启动PI-3激酶激活并调节Akt活性的信号通路尚未阐明。肌细胞中糖变性复合物的破坏会降低Akt和GSK-3的磷酸化，引发细胞凋亡。我们认为b-三磷酸甘聚糖（bDG）组装了一个信号分子复合物，允许与PI-3K的p85亚基结合并激活，启动Akt磷酸化。我们认为PI-3激酶/Akt的激活需要bDG复合物相关膜的内吞作用。这类似于最近报道的缺血预处理是由内体g蛋白偶联受体激活途径介导的。这些研究将提供不可逆缺血性心肌损伤的分子机制和预适应的末端效应。这可能允许药物模式的发展，治疗延迟心肌缺血和保存心肌梗塞损害。

DESCRIPTION (provided by applicant): The PI-3 kinase/Akt pathway is a potential mediator of the cardioprotection provided by preconditioning. The primary purpose of this proposal is the identification of the cardioprotective end-effectors that are activated by the PI-3 kinase/Akt pathway. Heat shock factor-1 (HSF-1) is a transcription factor that initiates the expression of heat shock protein 70 (HSP70), a molecular chaperone that has been associated with the cardioprotection provided by ischemic preconditioning. A role for NFkB in ischemic preconditioning has also been demonstrated. HSF-1 and NFkB activation are negatively regulated by GSK-3 and this regulation is abrogated by the phosphorylation of glycogen synthase kinase (GSK)-3b by Akt. The relative role of GSK-3 in the inhibition of HSF-1 and NFkB will be determined. We will also examine an alternative Akt substrate apoptosis signal regulating kinase 1 (ASK1). We will determine the association of Akt with ASK1 and the subsequent Akt mediated phosphorylation of ASK-1 at Ser83, negatively regulating the activation of p38MAPK and Jun kinase and the initiation of apoptosis. This might involve the interaction of ASK1 with 14-3-3 protein. We will also examine the association of Akt with the small heat shock protein, HSP27, which functions as a scaffolding protein for Akt. We will determine the ability of HSP27, in association with Akt, to facilitate the anti-apoptotic function of Akt. The signaling pathways that initiate PI-3 kinase activation during myocardial ischemia and regulate Akt activity have not been elucidated. Disruption of the dystroglycan complex in muscle cells decreases Akt and GSK-3 phosphorylation, initiating apoptosis. We propose that b-dystroglycan (bDG) assembles a complex of signaling molecules that allows an association with and activation of the p85 subunit of PI-3K, initiating Akt phosphorylation. We propose that PI-3 kinase/Akt activation requires endocytosis of this membrane associated the bDG complex. This is analogous to the recent report that ischemic preconditioning is mediated by an endosomal G-protein coupled receptor activation pathway. These studies will afford a molecular understanding of the mechanisms of irreversible ischemic myocardial injury and the end effectors of preconditioning. This may allow the development of pharmacologic modalities for the therapeutic delay of myocardial ischemia and the preservation of myocardium jeopardized by infarction.