Myocardial ischemic activation of the Akt pathway

描述(申请人提供)：PI-3激酶/Akt通路是预适应所提供的心脏保护的潜在介体。这项建议的主要目的是确定由PI-3激酶/Akt通路激活的心脏保护性末端效应器。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是一种分子伴侣，与缺血预适应提供的心脏保护作用有关。NFkB在缺血预适应中的作用也已被证明。HSF-1和NFkB的激活受GSK-3的负性调节，这种调节被Akt对糖原合成酶激酶(GSK)-3b的磷酸化所取消。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底物凋亡信号调节蛋白1(ASK1)。我们将确定Akt与ASK1的关联，以及随后Akt介导的Ask-1在Ser83处的磷酸化，负向调节p38MAPK和Jun激酶的激活和启动细胞凋亡。这可能与ASK1与14-3-3蛋白的相互作用有关。我们还将研究Akt与小的热休克蛋白HSP27的关联，HSP27是Akt的支架蛋白。我们将确定HSP27与Akt结合的能力，以促进Akt的抗凋亡功能。在心肌缺血时启动PI-3激酶激活和调节Akt活性的信号通路尚未阐明。肌肉细胞中肌营养不良蛋白聚糖复合体的破坏会降低Akt和GSK-3的磷酸化，从而启动细胞凋亡。我们认为，b-dystroglan(BDG)组装了一个信号分子复合体，允许与PI-3K的P85亚单位结合并激活，启动Akt的磷酸化。我们认为PI-3激酶/Akt的激活需要BDG复合体相关膜的内吞作用。这类似于最近的报道，即缺血预适应是由内体G蛋白偶联受体激活途径介导的。这些研究将使我们从分子水平上了解不可逆的缺血性心肌损伤的机制以及预适应的终末效应。这可能会为延迟治疗心肌缺血和保护因心肌梗死而受损的心肌开发药物。

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.