Stroke is a common affliction among veterans, and treatments are few. Work by our labs and those of our collaborators' have focused on the protective potential of heat shock proteins, namely, the highly inducible 70 kD heat shock protein (HSP70). HSP70 appears to have cytoprotective properties by nature of its chaperone functions, presumably leading to enhancement of nascent protein folding and prevention of protein aggregation. However, work in related fields has shown that HSPs appear to positively influence many aspects of ischemic cell death. We previously showed that overexpression of HSP70 or its pharmacological induction protects by inhibiting inflammation and upregulating the anti-apoptotic protein, Bcl-2. Others have shown the HSP70 blocks apoptosis by preventing cytochrome c release from the mitochondria or inhibiting caspase activation. Through collaborative work with Dr. Jong Eun Lee (Yonsei University, S. Korea), we identified dynamin as one protein substantially suppressed by HSP70 overexpression. Dynamin is a GTPase involved in receptor- mediated endocytosis through detaching clathrin-coated vesciles from the plasma membrane. Its role in ischemic brain cell death is completely unknown, but has been implicated in facilitating apoptosis by trafficking the death receptor Fas to the cell surface. In this application, we propose to further explore these observations that HSP70 protects the brain against stroke by interfering with dynamin export of Fas, and to address the implications of dynamin as a therapeutic target.
Specific aim 1 : Determine whether dynamin inhibition is protective, and if its suppression is linked to protection by HSP70.
Specific aim 2 : Determine whether there is a link between dynamin, fas and dynamin inhibition by HSP70.
Specific aim 3 : Determine how HSP70 regulates dynamin expression and/or function.
We found that HSP70, a protein that is increased in the brain after stroke, improves outcome in a stroke model. How HSP70 does this is not entirely clear, so we carried out a proteomics analysis in animal brains subjected to stroke to determine which proteins were most changed when HSP70 was overexpressed. This analysis showed that dynamin, a protein involved in cellular uptake of molecules, is increased after stroke, but is suppressed by HSP70. What dynamin is doing during stroke and whether this has anything to do with the therapeutic effect of HSP70 is completely unknown. We propose to explore whether dynamin contributes to stroke injury, and if blocking it is therapeutic. Stroke afflicts many veterans. Thus, work from this proposal could lead to treatments for veterans who suffer stroke.
