Faculty Opinions recommendation of Signal sequence insufficiency contributes to neurodegeneration caused by transmembrane prion protein.

2010 ◽  
Author(s):  
Joachim Seemann
Keyword(s):  
Prion Protein ◽  
Signal Sequence

scholarly journals Signal sequence insufficiency contributes to neurodegeneration caused by transmembrane prion protein

2010 ◽  
Vol 188 (4) ◽  
pp. 515-526 ◽  
Author(s):  
Neena S. Rane ◽  
Oishee Chakrabarti ◽  
Lionel Feigenbaum ◽  
Ramanujan S. Hegde
Keyword(s):  
Prion Protein ◽  
Protein Translocation ◽  
Signal Sequence ◽  
Signal Sequences ◽  
Hydrophobic Domain ◽  
Sequence Variations ◽  
Sufficient Magnitude ◽  
The Impact

Protein translocation into the endoplasmic reticulum is mediated by signal sequences that vary widely in primary structure. In vitro studies suggest that such signal sequence variations may correspond to subtly different functional properties. Whether comparable functional differences exist in vivo and are of sufficient magnitude to impact organism physiology is unknown. Here, we investigate this issue by analyzing in transgenic mice the impact of signal sequence efficiency for mammalian prion protein (PrP). We find that replacement of the average efficiency signal sequence of PrP with more efficient signals rescues mice from neurodegeneration caused by otherwise pathogenic PrP mutants in a downstream hydrophobic domain (HD). This effect is explained by the demonstration that efficient signal sequence function precludes generation of a cytosolically exposed, disease-causing transmembrane form of PrP mediated by the HD mutants. Thus, signal sequences are functionally nonequivalent in vivo, with intrinsic inefficiency of the native PrP signal being required for pathogenesis of a subset of disease-causing PrP mutations.

scholarly journals Prion Protein Folding Mechanism Revealed by Pulling Force Studies

2020 ◽  
Author(s):  
Theresa Kriegler ◽  
Sven Lang ◽  
Luigi Notari ◽  
Tara Hessa
Keyword(s):  
Prion Protein ◽  
Signal Sequence ◽  
Specific Sequence ◽  
Intrinsically Disordered ◽  
Sequence Of Events ◽  
Complex Protein ◽  
Nascent Chain ◽  
Mature Domain ◽  
Pulling Force ◽  
A Minor

AbstractThe mammalian prion protein (PrP) engages with the ribosome-Sec61 translocation channel complex to generate different topological variants that are either physiological, or involved in neurodegenerative diseases. Here, we describe cotranslational folding and translocation mechanisms of PrP coupled to a Xbp1-based arrest peptide (AP) as folding sensor, to measure forces acting on PrP nascent chain. Our data reveal two main pulling events followed by a minor third one exerted on the nascent chains during their translocation.Using those force landscapes, we show that a specific sequence within an intrinsically disordered region, containing a polybasic and glycine-proline rich residues, modulates the second pulling event by interacting with TRAP complex. This work also delineates the sequence of events involved in generation of PrP toxic transmembrane topologies during its synthesis. Our results shed new insight into the folding of such topological complex protein, where marginal pulling by the signal sequence, together with the downstream sequence in the mature domain, primarily drives an overall inefficient translocation resulting in the nascent chain to adopt other topologies.

scholarly journals Cotranslational Partitioning of Nascent Prion Protein into Multiple Populations at the Translocation Channel

2002 ◽  
Vol 13 (11) ◽  
pp. 3775-3786 ◽  
Author(s):  
Soo Jung Kim ◽  
Ramanujan S. Hegde
Keyword(s):  
Endoplasmic Reticulum ◽  
Prion Protein ◽  
Mechanism Of Action ◽  
Transmembrane Domain ◽  
Signal Sequence ◽  
Multiple Populations ◽  
Sequence Of Events ◽  
N Terminus ◽  
Complete Reversal ◽  
Single Polypeptide

The decisive events that direct a single polypeptide such as the prion protein (PrP) to be synthesized at the endoplasmic reticulum in both fully translocated and transmembrane forms are poorly understood. In this study, we demonstrate that the topological heterogeneity of PrP is determined cotranslationally, while at the translocation channel. By evaluating sequential intermediates during PrP topogenesis, we find that signal sequence-mediated initiation of translocation results in an interaction between nascent PrP and endoplasmic reticulum chaperones, committing the N terminus to the lumen. Synthesis of the transmembrane domain before completion of this step allows it to direct the generation of CtmPrP, a transmembrane form with its N terminus in the cytosol. Thus, segregation of nascent PrP into different topological configurations is critically dependent on the precise timing of signal-mediated initiation of N-terminus translocation. Consequently, this step could be experimentally tuned to modify PrP topogenesis, including complete reversal of the elevatedCtmPrP caused by disease-associated mutations in the transmembrane domain. These results delineate the sequence of events involved in PrP biogenesis, explain the mechanism of action ofCtmPrP-favoring mutations associated with neurodegenerative disease, and more generally, reveal that translocation substrates can be cotranslationally partitioned into multiple populations at the translocon.

scholarly journals Inhibition of the FKBP family of peptidyl prolyl isomerases induces abortive translocation and degradation of the cellular prion protein

2016 ◽  
Vol 27 (5) ◽  
pp. 757-767 ◽  
Author(s):  
Pawel Stocki ◽  
Maxime Sawicki ◽  
Charles E. Mays ◽  
Seo Jung Hong ◽  
Daniel C. Chapman ◽  
...  
Keyword(s):  
Prion Protein ◽  
Therapeutic Strategy ◽  
Signal Sequence ◽  
Prion Diseases ◽  
Cellular Prion Protein ◽  
Potential Therapeutic Target ◽  
Subsequent Degradation ◽  
Mouse Cells ◽  
Peptidyl Prolyl Isomerases ◽  
Calcineurin Inhibition

Prion diseases are fatal neurodegenerative disorders for which there is no effective treatment. Because the cellular prion protein (PrPC) is required for propagation of the infectious scrapie form of the protein, one therapeutic strategy is to reduce PrPCexpression. Recently FK506, an inhibitor of the FKBP family of peptidyl prolyl isomerases, was shown to increase survival in animal models of prion disease, with proposed mechanisms including calcineurin inhibition, induction of autophagy, and reduced PrPCexpression. We show that FK506 treatment results in a profound reduction in PrPCexpression due to a defect in the translocation of PrPCinto the endoplasmic reticulum with subsequent degradation by the proteasome. These phenotypes could be bypassed by replacing the PrPCsignal sequence with that of prolactin or osteopontin. In mouse cells, depletion of ER luminal FKBP10 was almost as potent as FK506 in attenuating expression of PrPC. However, this occurred at a later stage, after translocation of PrPCinto the ER. Both FK506 treatment and FKBP10 depletion were effective in reducing PrPScpropagation in cell models. These findings show the involvement of FKBP proteins at different stages of PrPCbiogenesis and identify FKBP10 as a potential therapeutic target for the treatment of prion diseases.

scholarly journals Distance of sequons to the C-terminus influences the cellular N-glycosylation of the prion protein

2003 ◽  
Vol 370 (1) ◽  
pp. 351-355 ◽  
Author(s):  
Adrian R. WALMSLEY ◽  
Nigel M. HOOPER
Keyword(s):  
Prion Protein ◽  
Signal Sequence ◽  
Prion Diseases ◽  
The Novel ◽  
Gpi Anchor ◽  
Glycosyl Phosphatidylinositol ◽  
Novel Approach ◽  
C Terminus ◽  
Human Neuronal Cells ◽  
Translational Process

Cell-specific differences in the utilization of the two N-glycosylation sequons (Asn180-Ile-Thr and Asn196-Phe-Thr) of the prion protein (PrP) have been proposed to influence the aetiology of the neurodegenerative prion diseases. As the N-glycosylation of PrP is ablated by deletion of the C-terminal glycosyl-phosphatidylinositol (GPI) anchor signal sequence, we have investigated the determinants for PrP sequon utilization in human neuronal cells using the novel approach of restoring N-glycosylation to secreted forms of PrP lacking a GPI anchor. N-glycosylation was restored to an efficiency comparable with that of GPI anchored PrP when the distance of the sequon to the C-terminus was increased so that it was sufficient to reach the active site of oligosaccharyltransferase before chain termination. Our findings indicate that sequon utilization in PrP is a co-translational process that precedes GPI anchor addition and, as such, will be greatly influenced by the dynamics of the translocon—oligosaccharyltransferase complex.

scholarly journals PrP Knockout Cells Expressing Transmembrane PrP Resist Prion Infection

2016 ◽  
Vol 91 (2) ◽  
Author(s):  
Karen E. Marshall ◽  
Andrew Hughson ◽  
Sarah Vascellari ◽  
Suzette A. Priola ◽  
Akikazu Sakudo ◽  
...  
Keyword(s):  
Prion Protein ◽  
Signal Sequence ◽  
Transmissible Spongiform Encephalopathy ◽  
Spongiform Encephalopathy ◽  
Wild Type ◽  
Gpi Anchor ◽  
Prion Infection ◽  
Endogenous Expression ◽  
Prion Propagation ◽  
Transmembrane Sequence

ABSTRACT Glycosylphosphatidylinositol (GPI) anchoring of the prion protein (PrPC) influences PrPC misfolding into the disease-associated isoform, PrPres, as well as prion propagation and infectivity. GPI proteins are found in cholesterol- and sphingolipid-rich membrane regions called rafts. Exchanging the GPI anchor for a nonraft transmembrane sequence redirects PrPC away from rafts. Previous studies showed that nonraft transmembrane PrPC variants resist conversion to PrPres when transfected into scrapie-infected N2a neuroblastoma cells, likely due to segregation of transmembrane PrPC and GPI-anchored PrPres in distinct membrane environments. Thus, it remained unclear whether transmembrane PrPC might convert to PrPres if seeded by an exogenous source of PrPres not associated with host cell rafts and without the potential influence of endogenous expression of GPI-anchored PrPC. To further explore these questions, constructs containing either a C-terminal wild-type GPI anchor signal sequence or a nonraft transmembrane sequence containing a flexible linker were expressed in a cell line derived from PrP knockout hippocampal neurons, NpL2. NpL2 cells have physiological similarities to primary neurons, representing a novel and advantageous model for studying transmissible spongiform encephalopathy (TSE) infection. Cells were infected with inocula from multiple prion strains and in different biochemical states (i.e., membrane bound as in brain microsomes from wild-type mice or purified GPI-anchorless amyloid fibrils). Only GPI-anchored PrPC supported persistent PrPres propagation. Our data provide strong evidence that in cell culture GPI anchor-directed membrane association of PrPC is required for persistent PrPres propagation, implicating raft microdomains as a location for conversion. IMPORTANCE Mechanisms of prion propagation, and what makes them transmissible, are poorly understood. Glycosylphosphatidylinositol (GPI) membrane anchoring of the prion protein (PrPC) directs it to specific regions of cell membranes called rafts. In order to test the importance of the raft environment on prion propagation, we developed a novel model for prion infection where cells expressing either GPI-anchored PrPC or transmembrane-anchored PrPC, which partitions it to a different location, were treated with infectious, misfolded forms of the prion protein, PrPres. We show that only GPI-anchored PrPC was able to convert to PrPres and able to serially propagate. The results strongly suggest that GPI anchoring and the localization of PrPC to rafts are crucial to the ability of PrPC to propagate as a prion.

Metallic prions

2004 ◽  
Vol 71 ◽  
pp. 193-202 ◽  
Author(s):  
David R Brown
Keyword(s):  
Prion Protein ◽  
Binding Capacity ◽  
Normal Function ◽  
Transmissible Spongiform Encephalopathies ◽  
Published Data ◽  
Normal Brain ◽  
Copper Binding ◽  
Loss Of Function ◽  
Spongiform Encephalopathies ◽  
The Brain

Prion diseases, also referred to as transmissible spongiform encephalopathies, are characterized by the deposition of an abnormal isoform of the prion protein in the brain. However, this aggregated, fibrillar, amyloid protein, termed PrPSc, is an altered conformer of a normal brain glycoprotein, PrPc. Understanding the nature of the normal cellular isoform of the prion protein is considered essential to understanding the conversion process that generates PrPSc. To this end much work has focused on elucidation of the normal function and activity of PrPc. Substantial evidence supports the notion that PrPc is a copper-binding protein. In conversion to the abnormal isoform, this Cu-binding activity is lost. Instead, there are some suggestions that the protein might bind other metals such as Mn or Zn. PrPc functions currently under investigation include the possibility that the protein is involved in signal transduction, cell adhesion, Cu transport and resistance to oxidative stress. Of these possibilities, only a role in Cu transport and its action as an antioxidant take into consideration PrPc's Cu-binding capacity. There are also more published data supporting these two functions. There is strong evidence that during the course of prion disease, there is a loss of function of the prion protein. This manifests as a change in metal balance in the brain and other organs and substantial oxidative damage throughout the brain. Thus prions and metals have become tightly linked in the quest to understand the nature of transmissible spongiform encephalopathies.

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