Article

HSP70 overexpression sequesters AIF and reduces neonatal hypoxic/ischemic brain injury

Department of Neurological Surgery, University of California at San Francisco 94121, USA.
Journal of Cerebral Blood Flow & Metabolism (Impact Factor: 5.41). 08/2005; 25(7):899-910. DOI: 10.1038/sj.jcbfm.9600080
Source: PubMed

ABSTRACT

Apoptosis is implicated in neonatal hypoxic/ischemic (H/I) brain injury among various forms of cell death. Here we investigate whether overexpression of heat shock protein (Hsp) 70, an antiapoptotic protein, protects the neonatal brain from H/I injury and the pathways involved in the protection. Postnatal day 7 (P7) transgenic mice overexpressing rat Hsp70 (Tg) and their wild-type littermates (Wt) underwent unilateral common carotid artery ligation followed by 30 mins exposure to 8% O(2). Significant neuroprotection was observed in Tg versus Wt mice on both P12 and P21, correlating with a high level of constitutive but not inducible Hsp70 in the Tg. More prominent injury was observed in Wt and Tg mice on P21, suggesting its continuous evolution after P12. Western blot analysis showed that translocation of cytochrome c, but not the second mitochondria-derived activator of caspase (Smac)/DIABLO and apoptosis-inducing factor (AIF), from mitochondria into cytosol was significantly reduced in Tg 24 h after H/I compared with Wt mice. Coimmunoprecipitation detected more Hsp70 bound to AIF in Tg than Wt mice 24 h after H/I, inversely correlating with the amount of nuclear, but not cytosolic, AIF translocation. Our results suggest that interaction between Hsp70 and AIF might have reduced downstream events leading to cell death, including the reduction of nuclear AIF translocation in the neonatal brains of Hsp70 Tg mice after H/I.

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Available from: R. Ann Sheldon, Apr 17, 2014
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    • "It has been shown that hsp70 inhibits the translocation of cytosolic AIF into the nucleus thereby preventing or delaying AIF-mediated cytotoxicity (Lui & Kong, 2007). Previous studies suggest that hsp70 interacts with AIF to favor its retention in the cytosol and inhibit its translocation into the nucleus (Gurbuxani et al., 2003; Lui & Kong, 2007; Matsumori et al., 2005; Ruchalski et al., 2006) whereas knockdown of hsp70 increases AIF-mediated apoptosis (Choudhury et al., 2011). These data taken together with the fact that mReg2 induces hsp70 expression that supports the notion that it may promote cytosolic retention of AIF in MIN6-mReg2 cells. "

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    • "It has been shown that hsp70 inhibits the translocation of cytosolic AIF into the nucleus thereby preventing or delaying AIF-mediated cytotoxicity (Lui & Kong, 2007). Previous studies suggest that hsp70 interacts with AIF to favor its retention in the cytosol and inhibit its translocation into the nucleus (Gurbuxani et al., 2003; Lui & Kong, 2007; Matsumori et al., 2005; Ruchalski et al., 2006) whereas knockdown of hsp70 increases AIF-mediated apoptosis (Choudhury et al., 2011). These data taken together with the fact that mReg2 induces hsp70 expression that supports the notion that it may promote cytosolic retention of AIF in MIN6-mReg2 cells. "
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    ABSTRACT: We have reported earlier that murine-regenerating gene mReg2 protects MIN6 mouse insulinoma cells from ER stress and caspase-mediated apoptosis. In apoptotic cells, DNA damage is induced by the nuclear translocation of mitochondrial apoptosis-inducing factor (AIF). Here we tested the hypothesis that mReg2 may regulate Scythe and/or hsp70 which influence the nuclear import of AIF. Treatment with thapsigargin (Tg) or doxorubicin induced an increase in nuclear AIF in MIN6 cells carrying the empty transfection vector (MIN6-VC) but not in cells overexpressing mReg2 (MIN6-mReg2). On one hand, nuclear Scythe was higher in the nucleus of MIN6-mReg2 compared with that in MIN6-VC cells. mReg2 did not alter the expression of AIF or Scythe. On the other hand, mReg2 induced the expression of hsp70 which is known to promote cytosolic retention of AIF. We conclude that mReg2 inhibits AIF-mediated apoptosis by promoting the nuclear presence of Scythe and inducing hsp70.
    Full-text · Article · Nov 2014 · Growth factors (Chur, Switzerland)
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    • "Cortical tissues were harvested at 0 h, 24 h, 72 h, and 7 d after I-R insult or sham operation. Whole-cell protein (WC) and the mitochondrial fraction (FM) were extracteds and Western blot analyses were performed as previously described [27], [28], [29]. Briefly, for detection of whole-cell protein, after homogenization, the cortical tissues were lysed in 300 μl RIPA buffer (50 mmol/L Tris-HCl [pH 7.4], 150 mmol/L NaCl, 1 mmol/L PMSF, 1 mmol/L EDTA, 1% Triton X-100, 0.5% sodium deoxycholate, and 0.1% SDS). "
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