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Blood, 1 October 2008, Vol. 112, No. 7, pp. 2787-2794.
Prepublished online as a Blood First Edition Paper on July 15, 2008; DOI 10.1182/blood-2008-02-141630.
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Submitted February 26, 2008
Accepted June 26, 2008
Tissue-type plasminogen activator and the low density lipoprotein receptor-related protein induce Akt phosphorylation in the ischemic brain
Jie An, Chen Zhang, Rohini Polavarapu, Xiaohui Zhang, Xiumei Zhang, and Manuel Yepes*
Neurology, Emory University, Atlanta, GA, United States
Institute of Pharmacology, Shandong University School of Medicine, Jinan, China
* Corresponding author; email: myepes{at}emory.edu.
Tissue-type plasminogen activator (tPA) is found in the intravascular space and in the central nervous system. The low density lipoprotein receptor-related protein (LRP) is expressed in neurons and in perivascular astrocytes. During cerebral ischemia tPA induces the shedding of LRP's extracellular domain from perivascular astrocytes and this is followed by the development of cerebral edema. Protein kinase B (Akt) is a serine/threonine kinase that plays a critical role not only in cell survival but also in the regulation of the permeability of the blood-brain barrier. We found that in the early phases of the ischemic insult the interaction between tPA and LRP induces Akt phosphorylation (pAkt) in perivascular astrocytes and inhibits pAkt in neurons. Co-immunoprecipitation studies indicate that pAkt and LRP's intracellular domain interact in perivascular astrocytes, and that this interaction is dependent upon the presence of tPA and results in the development of edema. Together, these results indicate that in the early stages of cerebral ischemia the interaction between tPA and LRP in perivascular astrocytes induces the activation of a cell signaling event mediated by pAkt that leads to increase in the permeability of the blood-brain barrier.

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