HuR Regulation of HSP 70 in Brain Reperfusion

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DESCRIPTION (provided by applicant): The long-term goal of the DeGracia laboratory is to investigate the basic cellular pathology of ischemia/reperfusion (l/R) brain injury to provide a foundation to develop effective clinical therapies. l/R injury underlies the morbidity and mortality associated with stroke and cardiac arrest and resuscitation. There are currently no effective therapies to halt neuronal death following brain l/R. Here, we propose a novel mechanism of regulation of the 70 kDa inducible heat shock protein HSP70. l/R-resistant neurons (e.g. hippocampal CA3), synthesize HSP70 protein early in reperfusion. l/R-vulnerable neurons (hippocampal CAI), transcribe ample hsp70 mRNA, but fail to synthesize the HSP70 protein. Our preliminary data shows nuclear export of the mRNA-stabilizing protein HuR correlates with HSP70 translation. HuR binds ARE-containing mRNAs, and hsp70 mRNA contains an ARE sequence. To assess the role of HuR in regulating HSP70 synthesis, we propose the following aims: 1. To determine the subcellular localization of HuR and hsp70 mRNA in the reperfused hippocampus. This aim will determine whether the subcellular location of hsp70 mRNA correlates with the location of HuR and whether the location of hsp70 mRNA differs between ischemia-resistant CA1 and ischemia-vulnerable CAS neurons. 2. To determine if HuR nuclear export is causally linked to HSP70 translation. 5' adenosine monophosphate- activated protein kinase (AMPK) activation causes nuclear retention of HuR and worsens stroke outcome. HuR subcellular localization, HSP70 translation, and cell survival will be determined following ischemia and reperfusion in the presence of pharmacologic activation or inhibition of AMPK. Public Heath Relevance: Thousands die from ischemic brain injury annually. These studies will increase our understanding of why the brain is damaged following stroke or cardiac arrest and potentially contribute to development of treatments.