Association of Bcl-2 with Misfolded Prion Protein Is Linked to the Toxic Potential of Cytosolic PrP

Rambold, Angelika S.; Miesbauer, Margit; Rapaport, Doron; Bartke, Till; Baier, Michael; Winklhofer, Konstanze F.; Tatzelt, Jörg

doi:10.1091/mbc.e06-01-0083

Cited by 89 publications

(104 citation statements)

References 44 publications

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“…Regarding the role of Cyt PrP, most knowledge has been provided by models consisting of mutant polypeptide chains that are inappropriately expressed and folded in the cytosol. These PrP(23-230) chains exhibit a widespread intracellular distribution (19 -21) and an alleged role that varies from cytotoxic (14,20) to innocuous or even protective (19,22,23). These contradictions call into question the fidelity with which such models can describe Cyt PrP.…”

Section: Cytmentioning

confidence: 99%

Biosynthesis of Prion Protein Nucleocytoplasmic Isoforms by Alternative Initiation of Translation

Juanes

Elvira

García-Grande

et al. 2009

Journal of Biological Chemistry

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The cellular prion protein PrP C is synthesized as a family of four distinct forms. Of these, Cyt PrP is a minor member that segregates outside of the secretory route and can generate cytotoxic forms. Using signal sequence mutants, we found that Cyt PrP is translated from a downstream AUG (coding for Met-8 in human PrP or Met-15 in Syrian hamster PrP). Shortening of the signal sequence dictated the spillage of this isoform into the cytosol, from where it accessed the nucleus or formed insoluble cytosolic aggregates if the proteasome is inhibited. The PrP isoform isolated from the nuclear fractions of cell and brain homogenates was partially SUMO-1-conjugated. Expression of HaPrP(M15) in cells caused an antiproliferative phenotype due to a cell cycle arrest at the G 0 /G 1 phase. The identification of this PrP isoform and its properties provides novel insight into PrP C physiological and pathological functions.The cellular prion protein (PrP C ) 2 underlies a group of fatal neurodegenerative diseases through its conversion into selfperpetuating and neurotoxic forms (1-4). Despite a large amount of evidence supporting a role in survival/death and growth/differentiation cell decisions, the physiological function of PrP C and its involvement in disease remain elusive (5-8). A crucial limiting factor for PrP C functional determination is its molecular diversity. Although PrP C is mainly thought of as a glycoprotein attached to the cell surface by a glycosylphosphatidylinositol anchor, PrP C is actually synthesized as a family of four members: the membrane anchored glycoprotein ( Sec PrP), two transmembrane forms with opposite topologies ( Ntm PrP and Ctm PrP), and a soluble form ( Cyt PrP) (3, 9 -12).Of these different members, Cyt PrP, accounts for a minor intracellular subset of PrP C that has attracted much attention because its accumulation sensitizes cells to death (13-15). Initially, CytPrP was thought to be formed by misfolded chains that retrotranslocated through the endoplasmic reticulum-associated protein degradation-proteasome pathway (16,17). However, it was later shown that Cyt PrP is constitutively populated by nascent chains that spill into the cytosol due to inefficient N-terminal signaling (15,18). Regarding the role of Cyt PrP, most knowledge has been provided by models consisting of mutant polypeptide chains that are inappropriately expressed and folded in the cytosol. These PrP(23-230) chains exhibit a widespread intracellular distribution (19 -21) and an alleged role that varies from cytotoxic (14, 20) to innocuous or even protective (19,22,23). These contradictions call into question the fidelity with which such models can describe Cyt PrP. The finding that information for Cyt PrP synthesis is contained in its N-terminal signal sequence (15) prompted us to decipher this code and use it as a tool to isolate its synthesis from that of the major forms and inspect its function. We have found that Cyt PrP is indeed a novel PrP isoform that accesses the nucleus and interferes with cell growth. These r...

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Section: Cytmentioning

confidence: 99%

Biosynthesis of Prion Protein Nucleocytoplasmic Isoforms by Alternative Initiation of Translation

Juanes

Elvira

García-Grande

et al. 2009

Journal of Biological Chemistry

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“…Activation of caspase-3 was determined as described previously. 37 Briefly, SH-SY5Y cells or skin fibroblasts were grown on glass coverslips. Twenty four hours after transfection (for parkin knockdown 3 days later), cells were incubated with TG, TM and/or epoxomycin as Figure 9 Interplay between ER stress, mitochondrial stress and parkin.…”

Section: Discussionmentioning

confidence: 99%

Parkin is transcriptionally regulated by ATF4: evidence for an interconnection between mitochondrial stress and ER stress

et al. 2010

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Loss of parkin function is responsible for the majority of autosomal recessive parkinsonism. Here, we show that parkin is not only a stress-protective, but also a stress-inducible protein. Both mitochondrial and endoplasmic reticulum (ER) stress induce an increase in parkin-specific mRNA and protein levels. The stress-induced upregulation of parkin is mediated by ATF4, a transcription factor of the unfolded protein response (UPR) that binds to a specific CREB/ATF site within the parkin promoter. Interestingly, c-Jun can bind to the same site, but acts as a transcriptional repressor of parkin gene expression. We also present evidence that mitochondrial damage can induce ER stress, leading to the activation of the UPR, and thereby to an upregulation of parkin expression. Vice versa, ER stress results in mitochondrial damage, which can be prevented by parkin. Notably, the activity of parkin to protect cells from stress-induced cell death is independent of the proteasome, indicating that proteasomal degradation of parkin substrates cannot explain the cytoprotective activity of parkin. Our study supports the notion that parkin has a role in the interorganellar crosstalk between the ER and mitochondria to promote cell survival under stress, suggesting that both ER and mitochondrial stress can contribute to the pathogenesis of Parkinson's disease.

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“…Apoptosis Assay-Activation of caspase-3 was determined as described previously (23). Briefly, SH-SY5Y cells were grown on glass coverslips.…”

Section: Methodsmentioning

confidence: 99%

Aberrant Folding of Pathogenic Parkin Mutants

Schlehe

Lutz

Pilsl

et al. 2008

Journal of Biological Chemistry

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Parkinson disease (PD)2 is the second most common neurodegenerative disease after Alzheimer disease. Although most PD cases occur sporadically, familial variants share important features with sporadic PD, most notably the demise of dopaminergic neurons in the substantia nigra pars compacta. Consequently, insight into the function of PD-associated genes might promote our understanding of pathogenic mechanisms not only in familial, but also in sporadic PD. Five genes have unambiguously been linked to PD over the past decade, the genes encoding ␣-synuclein and LRRK2 for autosomal dominant PD, and those encoding Parkin, PINK1, and DJ-1 for autosomal recessive PD (reviewed in Refs. 1-3). So far, over a hundred different pathogenic mutations in the parkin gene have been identified, which account for the majority of autosomal recessive PD cases. Parkin is a member of the RBR (ring between ring fingers) protein family, characterized by the presence of two RING domains (really interesting new gene), which flank a cysteine-rich in-between RINGs (IBR) domain. Similarly to other RBR proteins, Parkin has an E3 ubiquitin ligase activity, mediating the attachment of ubiquitin to substrate proteins (4 -6). Parkin can obviously mediate different modes of ubiquitylation, including monoubiquitylation, multiple monoubiquitylation, and polyubiquitylation both via lysine 48 and lysine 63, depending on the experimental conditions and the putative Parkin substrate analyzed (reviewed in Refs. 7 and 8). Importantly, the neuroprotective activity of Parkin seems to be associated with its ability to promote degradation-independent ubiquitylation (9, 10).Different lines of evidence indicate that pathogenic parkin mutations result in a loss of Parkin function. Our initial studies revealed that misfolding and aggregation is characteristic for C-terminal deletion mutants of Parkin based on the following biochemical features specific for mutant Parkin: 1) insolubility in non-ionic and ionic detergents; 2) sedimentation in a sucrose step gradient; 3) resistance to a limited proteolytic digestion; 4) loss of membrane association; and 5) formation of scattered aggregates in cells determined by immunocytochemistry (11,12). Alterations in the detergent solubility of Parkin and formation of Parkin aggregates/inclusion bodies have also been reported for various Parkin missense mutants (13-18). We also observed that even wild-type Parkin is prone to misfolding under severe oxidative stress (12). Remarkably, insoluble, catechol-modified Parkin could be detected in the substantia nigra of patients suffering from sporadic PD, suggesting a more general role of Parkin in the pathogenesis of PD (19). In support of this concept, the E3 ligase activity of Parkin has been shown to be impaired by nitrosative stress, and there is indeed evidence for the presence of S-nitrosylated Parkin in the brains of PD patients (20,21).Based on our finding that the deletion of C-terminal amino acids results in misfolding and aggregation of Parkin, we performed a comparative an...

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Association of Bcl-2 with Misfolded Prion Protein Is Linked to the Toxic Potential of Cytosolic PrP

Cited by 89 publications

References 44 publications

Biosynthesis of Prion Protein Nucleocytoplasmic Isoforms by Alternative Initiation of Translation

Biosynthesis of Prion Protein Nucleocytoplasmic Isoforms by Alternative Initiation of Translation

Parkin is transcriptionally regulated by ATF4: evidence for an interconnection between mitochondrial stress and ER stress

Aberrant Folding of Pathogenic Parkin Mutants

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