CHIP and HSPs interact with -APP in a proteasome-dependent manner and influence A metabolism

Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California, United States
Human Molecular Genetics (Impact Factor: 6.39). 05/2007; 16(7):848-64. DOI: 10.1093/hmg/ddm030
Source: PubMed


The C-terminus Hsp70 interacting protein (CHIP) has dual function as both co-chaperone and ubiquitin ligase. CHIP is increasingly implicated in the biology of polyglutamine expansion disorders, Parkinson's disease and tau protein in Alzheimer's disease. We investigated the involvement of CHIP in the metabolism of the beta-amyloid precursor protein and its derivative beta-amyloid (Abeta). Using immunoprecipitation, fluorescence localization and crosslinking methods, endogenous CHIP and betaAPP interact in brain and cultured skeletal myotubes as well as when they are expressed in stable HEK cell lines. Their interaction is confined to Golgi and ER compartments. In the presence of the proteasome inhibitor with MG132, endogenous and expressed betaAPP levels are significantly increased and accordingly, the interaction with CHIP enhanced. Concurrently, levels of Hsp70 were most consistently induced by proteasome inhibition among the various heat shock proteins (HSPs) tested. Thus, complexes of CHIP, Hsp70 and holo-betaAPP (as well as C-terminal fragments) were stabilized by the action of MG132. Moreover, CHIP itself is shown to both increase cellular holo-betaAPP levels and protect it from oxidative stress and degradation. Interestingly, CHIP also promotes the association of ubiquitin with betaAPP, implying that a smaller pool of betaAPP is destined for proteasomal processing. In neuronal cultures, CHIP and Hsp70/90 expression reduce steady-state cellular Abeta levels and hasten its degradation in pulse-chase experiments. The functional significance of CHIP and HSP interactions, especially with Hsp70, was tested using siRNA and in neuronal cells where protection from Abeta-induced toxicity is shown. We conclude that CHIP, as a bimolecular switch, interacts with HSP to stabilize normal holo-betaAPP on the one hand while also assisting in the ubiquitination of a subpopulation of betaAPP molecules that are destined for proteasome degradation. CHIP also hastens the clearance of Abeta in a manner consistent with its known neuroprotective properties.

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    • "In this study, we have shown that BACE1 is a new substrate of CHIP which binds to CHIP's U-box domain and CHIP promotes BACE1 destabilization through UPS by promoting its ubiquitination (Fig. 6). CHIP and HSPs were earlier shown to interact with b- APP in a proteasome-dependent manner and influence Ab metabolism (Kumar et al., 2007). We have also demonstrated the functional consequence of BACE1 regulation by CHIP on APP processing in both neurons and HEK-APP stable cells in which overexpression of CHIP reduced BACE1 activity through decreased b-cleavage product (CTFb- 99) and Ab generation. "
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    ABSTRACT: In patient with Alzheimer's disease (AD), deposition of amyloid-beta Aβ, a proteolytic cleavage of amyloid precursor protein (APP) by β-secretase/BACE1, forms senile plaque in the brain. BACE1 activation is caused due to oxidative stresses and dysfunction of ubiquitin-proteasome system (UPS), which is linked to p53 inactivation. As partial suppression of BACE1 attenuates Aβ generation and AD-related pathology, it might be an ideal target for AD treatment. We have shown that both in neurons and in HEK-APP cells, BACE1 is a new substrate of E3-ligase CHIP and an inverse relation exists between CHIP and BACE1 level. CHIP inhibits ectopic BACE1 level by promoting its ubiquitination and proteasomal degradation, thus reducing APP processing; it stabilizes APP in neurons, thus reducing Aβ. CHIP(U) (box) domain physically interacts with BACE1; however, both U-box and TPR domain are essential for ubiquitination and degradation of BACE1. Further, BACE1 is a downstream target of p53 and overexpression of p53 decreases BACE1 level. In HEK-APP cells, CHIP is shown to negatively regulate BACE1 promoter through stabilization of p53's DNA-binding conformation and its binding upon 5' UTR element (+127 to +150). We have thus discovered that CHIP regulates p53-mediated trans-repression of BACE1 at both transcriptional and post-translational level. We propose that a CHIP-BACE1-p53 feedback loop might control APP stabilization, which could further be utilized for new therapeutic intervention in AD. © 2015 The Authors. Aging Cell published by the Anatomical Society and John Wiley & Sons Ltd.
    Full-text · Article · Mar 2015 · Aging Cell
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    • "If these increases in heat shock proteins serve to defend against proteotoxic stress, heat shock proteins should also be protective in experimental models of injury. Consistent with this hypothesis, Hsp70 has been shown to be protective in many experimental disease models, including the MPTP model of Parkinson's disease and the β-amyloid model of Alzheimer's disease (Dong et al. 2005; Jung et al. 2008; Kalia et al. 2010; Kumar et al. 2007; Magrane et al. 2004; Muchowski and Wacker 2005; Nagel et al. 2008; Sherman and Goldberg 2001). Furthermore, Hsp70 has been shown to enhance α-synuclein refolding or degradation, thereby decreasing α-synuclein fibrillization and toxicity (Klucken et al. 2004; Luk et al. 2008). "
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    ABSTRACT: Many members of the heat shock protein family act in unison to refold or degrade misfolded proteins. Some heat shock proteins also directly interfere with apoptosis. These homeostatic functions are especially important in proteinopathic neurodegenerative diseases, in which specific proteins misfold, aggregate, and kill cells through proteotoxic stress. Heat shock protein levels may be increased or decreased in these disorders, with the direction of the response depending on the individual heat shock protein, the disease, cell type, and brain region. Aging is also associated with an accrual of proteotoxic stress and modulates expression of several heat shock proteins. We speculate that the increase in some heat shock proteins in neurodegenerative conditions may be partly responsible for the slow progression of these disorders, whereas the increase in some heat shock proteins with aging may help delay senescence. The protective nature of many heat shock proteins in experimental models of neurodegeneration supports these hypotheses. Furthermore, some heat shock proteins appear to be expressed at higher levels in longer-lived species. However, increases in heat shock proteins may be insufficient to override overwhelming proteotoxic stress or reverse the course of these conditions, because the expression of several other heat shock proteins and endogenous defense systems is lowered. In this review we describe a number of stress-induced changes in heat shock proteins as a function of age and neurodegenerative pathology, with an emphasis on the heat shock protein 70 (Hsp70) family and the two most common proteinopathic disorders of the brain, Alzheimer's and Parkinson's disease.
    Full-text · Article · Sep 2014 · Journal of Cell Communication and Signaling
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    • "HSP70 recognized Aβ oligomers and decrease the level of Aβ self-assembly, resulting in the suppression of the production of toxic Aβ [77, 87, 88]. HSP70 also stimulated the degradation of Aβ by enzyme mediated degradation, phagocytosis by microglia, and astrocytes [89]. HSP70 promote the stimulation of Aβ clearance through upregulation of expression of insulin degrading enzyme (IDE) and TGF-β1. "
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    ABSTRACT: Heat shock proteins 70 and heat shock proteins 90 (Hsp70/90) have been implicated in many crucial steps of carcinogenesis: stabilizing oncogenic proteins, inhibiting programmed cell death and replicative senescence, induction of tumor angiogenesis, and activation of the invasion and metastasis. Plenty of cancer related proteins have the ability of regulating the expression of Hsp70/90 through heat shock factor 1. Cancer and Alzheimer's disease (AD) have plenty of overlapping regions in molecular genetics and cell biology associated with Hsp70/90. The Hsp70, as a protein stabilizer, has a cellular protection against neurodegeneration of the central nervous system, while Hsp90 promote neurodegenerative disorders indirectly through regulating the expression of Hsp70 and other chaperones. All these make existing anticancer drugs target Hsp70/90 which might be used in AD therapy.
    Full-text · Article · Jul 2014 · BioMed Research International
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