Article

Humanin Binds and Nullifies Bid Activity by Blocking Its Activation of Bax and Bak

Burnham Institute, La Jolla, California 92037, USA.
Journal of Biological Chemistry (Impact Factor: 4.57). 05/2005; 280(16):15815-24. DOI: 10.1074/jbc.M411902200
Source: PubMed

ABSTRACT Recently, we discovered that Humanin (HN), a small endogenous peptide of 24 amino acids, binds to and inhibits the proapoptotic protein Bax. We show here that HN also interacts with the BH3-only Bcl-2/Bax family protein, Bid, as well as a truncated form of Bid (tBid) associated with protease-mediated activation of this proapoptotic protein. Synthetic HN peptide binds purified Bid and tBid in vitro and blocks tBid-induced release of cytochrome c and SMAC from isolated mitochondria, whereas mutant peptides that fail to bind Bid or tBid lack this activity. Moreover, HN peptide also retained protective activity on bax-/-mitochondria, indicating that HN can block tBid-induced release of apoptogenic proteins from these organelles in a Bax-independent manner. HN peptide inhibits tBid-induced oligomerization of Bax and Bak in mitochondrial membranes, as shown by experiments with chemical cross-linkers or gel filtration. Gene transfection experiments showed that HN (but not an inactive mutant of HN) also protects intact cells from apoptosis induced by overexpression of tBid. We conclude that Bid represents an additional cellular target of HN, and we propose that HN-mediated suppression of Bid contributes to the antiapoptotic activity of this endogenous peptide.

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    • "Recently, alternative mechanisms of action for transfected HN showed that it binds to Bax, BimEL, or tBid, and prevents translocation of these proteins from cytoplasm to mitochondria, thereby protecting cells from apoptosis-inducing insults that trigger the mitochondrial pathway for cell death [18] [19] [20]. However, the therapeutic application of HN in the treatment of neurodegenerative diseases is limited due to its rapid degradation in vivo and poor ability to cross the blood–brain barrier (BBB) and enter the cytoplasm of neuronal cells where cell death occurs. "
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    ABSTRACT: Inhibition of the early intracellular event that triggers neurodegenerative cascades and reversal of neuronal cell death are essential for effective treatment of Alzheimer's disease (AD). In this study, a novel therapeutic for AD, a transducible humanin with an extended caspase-3 cleavage sequence (tHN-C3), was developed and showed multiple mechanisms of therapeutic action. These included targeted delivery of anti-apoptotic protein humanin through the blood-brain barrier (BBB) to neuronal cells, specific inhibition of caspase-3 activation to inhibit the early triggering of AD progression, and delivery of humanin into the cytoplasm of neuronal cells undergoing apoptosis where it exerts its anti-apoptotic functions effectively. The tHN-C3 prevented neuronal cell death induced by H(2)O(2), or soluble Aβ(42), via Bax binding. In animal models of AD induced by amyloid beta, in Tg2576 mice, and in the rat middle cerebral artery occlusion model of stroke, tHN-C3 effectively prevented neuronal cell death, inflammatory cell infiltration into the brain, and improved cognitive memory. The therapeutic effectiveness of tHN-C3 was comparable to that of Aricept, a clinically approved drug for AD treatment. Therefore, tHN-C3 may be a new remedy with multiple therapeutic functions targeting the early and late stages of neurodegeneration in AD and other brain injuries.
    Journal of Controlled Release 01/2013; 166(3). DOI:10.1016/j.jconrel.2012.12.022 · 7.26 Impact Factor
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    • "Recently, alternative mechanisms of action for transfected HN showed that it binds to Bax, BimEL, or tBid, and prevents translocation of these proteins from cytoplasm to mitochondria, thereby protecting cells from apoptosis-inducing insults that trigger the mitochondrial pathway for cell death [18] [19] [20]. However, the therapeutic application of HN in the treatment of neurodegenerative diseases is limited due to its rapid degradation in vivo and poor ability to cross the blood–brain barrier (BBB) and enter the cytoplasm of neuronal cells where cell death occurs. "
    Journal of Controlled Release 01/2013; 166:307-315. · 7.26 Impact Factor
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    • "irradiation (Guo et al. 2003). Using co-immunoprecipitation experiments, humanin specifically bound to BAX, tBID, and BimEL (BCL2L11), but not other BCL2 family proteins such as BCL2 and BCL-B (BCL2L10) (Luciano et al. 2005, Zhai et al. 2005). Furthermore, the anti-apoptotic effect of humanin was specific to BAX-dependent apoptosis, as apoptosis by a BAX-independent stimulus, such as the use of tumor necrosis factor, was not suppressed. "
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    ABSTRACT: The discovery of humanin, a novel, mitochondria-derived peptide, has created a potentially new category of biologically active peptide. As more research unravels the endogenous role of humanin as well as its potential pharmacological use, its role in stress resistance has become clearer. Humanin protects cells from oxidative stress, serum starvation, hypoxia, and other insults in vitro and also improves cardiovascular disease as well as Alzheimer's disease in vivo. In this review we discuss the emerging role of humanin in stress resistance and its proposed mechanism of action.
    Journal of Molecular Endocrinology 12/2012; 50(1). DOI:10.1530/JME-12-0203 · 3.62 Impact Factor
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