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Membrane Domain Localization and Interaction of the Prion-Family Proteins, Prion and Shadoo with Calnexin. MEMBRANES 2021; 11:membranes11120978. [PMID: 34940479 PMCID: PMC8704586 DOI: 10.3390/membranes11120978] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 12/06/2021] [Accepted: 12/07/2021] [Indexed: 11/30/2022]
Abstract
The cellular prion protein (PrPC) is renowned for its infectious conformational isoform PrPSc, capable of templating subsequent conversions of healthy PrPCs and thus triggering the group of incurable diseases known as transmissible spongiform encephalopathies. Besides this mechanism not being fully uncovered, the protein’s physiological role is also elusive. PrPC and its newest, less understood paralog Shadoo are glycosylphosphatidylinositol-anchored proteins highly expressed in the central nervous system. While they share some attributes and neuroprotective actions, opposing roles have also been reported for the two; however, the amount of data about their exact functions is lacking. Protein–protein interactions and membrane microdomain localizations are key determinants of protein function. Accurate identification of these functions for a membrane protein, however, can become biased due to interactions occurring during sample processing. To avoid such artifacts, we apply a non-detergent-based membrane-fractionation approach to study the prion protein and Shadoo. We show that the two proteins occupy similarly raft and non-raft membrane fractions when expressed in N2a cells and that both proteins pull down the chaperone calnexin in both rafts and non-rafts. These indicate their possible binding to calnexin in both types of membrane domains, which might be a necessary requisite to aid the inherently unstable native conformation during their lifetime.
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Proteasomal Inhibition Redirects the PrP-Like Shadoo Protein to the Nucleus. Mol Neurobiol 2019; 56:7888-7904. [PMID: 31129810 PMCID: PMC6815274 DOI: 10.1007/s12035-019-1623-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Accepted: 04/24/2019] [Indexed: 01/08/2023]
Abstract
The Shadoo protein (Sho) exhibits homology to the hydrophobic region of the cellular isoform of prion protein (PrPC). As prion-infected brains gradually accumulate infectivity-associated isoforms of prion protein (PrPSc), levels of mature endogenous Sho become reduced. To study the regulatory effect of the proteostatic network on Sho expression, we investigated the action of lactacystin, MG132, NH4Cl, and 3-methyladenine (3-MA) in two cell culture models. In primary mixed neuronal and glial cell cultures (MNGCs) from transgenic mice expressing wild-type Sho from the PrP gene promoter (Tg.Sprn mice), lactacystin- and MG132-mediated inhibition of proteasomal activity shifted the repertoire of Sho species towards unglycosylated forms appearing in the nuclei; conversely, the autophagic modulators NH4Cl and 3-MA did not affect Sho or PrPC glycosylation patterns. Mouse N2a neuroblastoma cells expressing Sho under control of a housekeeping gene promoter treated with MG132 or lactacystin also showed increased nuclear localization of unglycosylated Sho. As two proteasomal inhibitors tested in two cell paradigms caused redirection of Sho to nuclei at the expense of processing through the secretory pathway, our findings define a balanced shift in subcellular localization that thereby differs from the decreases in net Sho species seen in prion-infected brains. Our data are indicative of a physiological pathway to access Sho functions in the nucleus under conditions of impaired proteasomal activity. We also infer that these conditions would comprise a context wherein Sho’s N-terminal nucleic acid–binding RGG repeat region is brought into play.
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Yang X, Zhang Y, Zhang L, He T, Zhang J, Li C. Prion protein and cancers. Acta Biochim Biophys Sin (Shanghai) 2014; 46:431-40. [PMID: 24681883 DOI: 10.1093/abbs/gmu019] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The normal cellular prion protein, PrP(C) is a highly conserved and widely expressed cell surface glycoprotein in all mammals. The expression of PrP is pivotal in the pathogenesis of prion diseases; however, the normal physiological functions of PrP(C) remain incompletely understood. Based on the studies in cell models, a plethora of functions have been attributed to PrP(C). In this paper, we reviewed the potential roles that PrP(C) plays in cell physiology and focused on its contribution to tumorigenesis.
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Affiliation(s)
- Xiaowen Yang
- Department of the First Abdominal Surgery, Jiangxi Tumor Hospital, Nanchang 330029, China
| | - Yan Zhang
- Department of Molecular Endocrinology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China
| | - Lihua Zhang
- Department of Pathology, Zhongda Hospital, Southeast University, Nanjing 210009, China
| | - Tianlin He
- Department of General Surgery, Changhai Hospital of Second Military Medical University, Shanghai 200433, China
| | - Jie Zhang
- Department of Stomatology, The First Affiliated Hospital of Shihezi University Medical College, Shihezi 832000, China
| | - Chaoyang Li
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China
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Wang S, Zhao H, Zhang Y. Advances in research on Shadoo, shadow of prion protein. CHINESE SCIENCE BULLETIN-CHINESE 2014. [DOI: 10.1007/s11434-014-0129-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Mays CE, Kim C, Haldiman T, van der Merwe J, Lau A, Yang J, Grams J, Di Bari MA, Nonno R, Telling GC, Kong Q, Langeveld J, McKenzie D, Westaway D, Safar JG. Prion disease tempo determined by host-dependent substrate reduction. J Clin Invest 2014; 124:847-58. [PMID: 24430187 DOI: 10.1172/jci72241] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Accepted: 11/07/2013] [Indexed: 01/01/2023] Open
Abstract
The symptoms of prion infection can take years or decades to manifest following the initial exposure. Molecular markers of prion disease include accumulation of the misfolded prion protein (PrPSc), which is derived from its cellular precursor (PrPC), as well as downregulation of the PrP-like Shadoo (Sho) glycoprotein. Given the overlapping cellular environments for PrPC and Sho, we inferred that PrPC levels might also be altered as part of a host response during prion infection. Using rodent models, we found that, in addition to changes in PrPC glycosylation and proteolytic processing, net reductions in PrPC occur in a wide range of prion diseases, including sheep scrapie, human Creutzfeldt-Jakob disease, and cervid chronic wasting disease. The reduction in PrPC results in decreased prion replication, as measured by the protein misfolding cyclic amplification technique for generating PrPSc in vitro. While PrPC downregulation is not discernible in animals with unusually short incubation periods and high PrPC expression, slowly evolving prion infections exhibit downregulation of the PrPC substrate required for new PrPSc synthesis and as a receptor for pathogenic signaling. Our data reveal PrPC downregulation as a previously unappreciated element of disease pathogenesis that defines the extensive, presymptomatic period for many prion strains.
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Mays CE, Coomaraswamy J, Watts JC, Yang J, Ko KW, Strome B, Mercer RC, Wohlgemuth SL, Schmitt-Ulms G, Westaway D. Endoproteolytic processing of the mammalian prion glycoprotein family. FEBS J 2013; 281:862-76. [DOI: 10.1111/febs.12654] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2013] [Revised: 10/25/2013] [Accepted: 11/19/2013] [Indexed: 11/28/2022]
Affiliation(s)
- Charles E. Mays
- Centre for Prions and Protein Folding Diseases; University of Alberta; Edmonton Canada
| | | | - Joel C. Watts
- Department of Biochemistry and Tanz Centre for Research in Neurodegenerative Diseases; University of Toronto; ON Canada
| | - Jing Yang
- Centre for Prions and Protein Folding Diseases; University of Alberta; Edmonton Canada
| | - Kerry W.S. Ko
- Centre for Prions and Protein Folding Diseases; University of Alberta; Edmonton Canada
| | - Bob Strome
- Department of Biochemistry and Tanz Centre for Research in Neurodegenerative Diseases; University of Toronto; ON Canada
| | - Robert C.C. Mercer
- Centre for Prions and Protein Folding Diseases; University of Alberta; Edmonton Canada
| | - Serene L. Wohlgemuth
- Centre for Prions and Protein Folding Diseases; University of Alberta; Edmonton Canada
| | - Gerold Schmitt-Ulms
- Department of Biochemistry and Tanz Centre for Research in Neurodegenerative Diseases; University of Toronto; ON Canada
| | - David Westaway
- Centre for Prions and Protein Folding Diseases; University of Alberta; Edmonton Canada
- Division of Neurology; Department of Biochemistry; University of Alberta; Edmonton Canada
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Abstract
Shadoo (Sho) is a brain glycoprotein with similarities to the unstructured region of PrPC. Frameshift alleles of the Sho gene, Sprn, are reported in variant Creutzfeldt-Jakob disease (vCJD) patients while Sprn mRNA knockdown in PrP-null (Prnp0/0) embryos produces lethality, advancing Sho as the hypothetical PrP-like “pi” protein. Also, Sho levels are reduced as misfolded PrP accumulates during prion infections. To penetrate these issues we created Sprn null alleles (Daude et al., Proc. Natl. Acad. Sci USA 2012; 109(23): 9035–40). Results from the challenge of Sprn null and TgSprn transgenic mice with rodent-adapted prions coalesce to define downregulation of Sho as a “tracer” for the formation of misfolded PrP. However, classical BSE and rodent-adapted BSE isolates may behave differently, as they do for other facets of the pathogenic process, and this intriguing variation warrants closer scrutiny. With regards to physiological function, double knockout mice (Sprn0/0/Prnp0/0) mice survived to over 600 d of age. This suggests that Sho is not pi, or, given the accumulating data for many activities for PrPC, that the pi hypothesis invoking a discrete signaling pathway to maintain neuronal viability is no longer tenable.
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Affiliation(s)
- Nathalie Daude
- Centre for Prions and Protein Folding Diseases, University of Alberta Edmonton, AB, Canada
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Knockout of the prion protein (PrP)-like Sprn gene does not produce embryonic lethality in combination with PrP(C)-deficiency. Proc Natl Acad Sci U S A 2012; 109:9035-40. [PMID: 22619325 DOI: 10.1073/pnas.1202130109] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Sprn gene encodes Shadoo (Sho), a glycoprotein with biochemical properties similar to the unstructured region of cellular prion protein (PrP(C)). Sho has been considered a candidate for the hypothetical π protein that supplies a PrP(C)-like function to maintain the viability of Prnp(0/0) mice lacking the PrP(C) protein. To understand these relationships more clearly we probed the cell biology of Sho and created knockout mice. Besides full-length and a "C1" C-terminal fragment, we describe a 6-kDa N-terminal Sho neuropeptide, "N1," which is present in membrane-enriched subcellular fractions of wild-type mice. Sprn null alleles were produced that delete all protein coding sequences yet spare the Mtg1 gene transcription unit that overlaps the Sprn 3' UTR; the resulting mice bred to homozygosity were viable and fertile, although Sprn(0/0) mice maintained in two genetic backgrounds weighed less than wild-type mice. Lack of Sho protein did not affect prion incubation time. Contrasting with lethality reported for knockdown of expression in Prnp(0/0) embryos using lentiviruses targeted against the Sprn 3' UTR, we established that double-knockout mice deficient in both Sho and PrP(C) are fertile and viable up to 690 d of age. Our data reduce the impetus for equating Sho with the notional π protein and are not readily reconciled with hypotheses wherein expression of PrP(C) and Sho are both required for completion of embryogenesis. Alternatively, and in accord with some reports for PrP(C), we infer that Sho's activity will prove germane to the maintenance of neuronal viability in postnatal life.
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Westaway D, Genovesi S, Daude N, Brown R, Lau A, Lee I, Mays CE, Coomaraswamy J, Canine B, Pitstick R, Herbst A, Yang J, Ko KWS, Schmitt-Ulms G, Dearmond SJ, McKenzie D, Hood L, Carlson GA. Down-regulation of Shadoo in prion infections traces a pre-clinical event inversely related to PrP(Sc) accumulation. PLoS Pathog 2011; 7:e1002391. [PMID: 22114562 PMCID: PMC3219720 DOI: 10.1371/journal.ppat.1002391] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Accepted: 10/07/2011] [Indexed: 11/18/2022] Open
Abstract
During prion infections of the central nervous system (CNS) the cellular prion protein, PrP(C), is templated to a conformationally distinct form, PrP(Sc). Recent studies have demonstrated that the Sprn gene encodes a GPI-linked glycoprotein Shadoo (Sho), which localizes to a similar membrane environment as PrP(C) and is reduced in the brains of rodents with terminal prion disease. Here, analyses of prion-infected mice revealed that down-regulation of Sho protein was not related to Sprn mRNA abundance at any stage in prion infection. Down-regulation was robust upon propagation of a variety of prion strains in Prnp(a) and Prnp(b) mice, with the exception of the mouse-adapted BSE strain 301 V. In addition, Sho encoded by a TgSprn transgene was down-regulated to the same extent as endogenous Sho. Reduced Sho levels were not seen in a tauopathy, in chemically induced spongiform degeneration or in transgenic mice expressing the extracellular ADan amyloid peptide of familial Danish dementia. Insofar as prion-infected Prnp hemizygous mice exhibited accumulation of PrP(Sc) and down-regulation of Sho hundreds of days prior to onset of neurologic symptoms, Sho depletion can be excluded as an important trigger for clinical disease or as a simple consequence of neuronal damage. These studies instead define a disease-specific effect, and we hypothesize that membrane-associated Sho comprises a bystander substrate for processes degrading PrP(Sc). Thus, while protease-resistant PrP detected by in vitro digestion allows post mortem diagnosis, decreased levels of endogenous Sho may trace an early response to PrP(Sc) accumulation that operates in the CNS in vivo. This cellular response may offer new insights into the homeostatic mechanisms involved in detection and clearance of the misfolded proteins that drive prion disease pathogenesis.
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Affiliation(s)
- David Westaway
- Centre for Prions and Protein Folding Diseases, University of Alberta, Edmonton, Alberta, Canada
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Watts JC, Stöhr J, Bhardwaj S, Wille H, Oehler A, DeArmond SJ, Giles K, Prusiner SB. Protease-resistant prions selectively decrease Shadoo protein. PLoS Pathog 2011; 7:e1002382. [PMID: 22163178 PMCID: PMC3219722 DOI: 10.1371/journal.ppat.1002382] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Accepted: 10/04/2011] [Indexed: 11/30/2022] Open
Abstract
The central event in prion diseases is the conformational conversion of the cellular prion protein (PrPC) into PrPSc, a partially protease-resistant and infectious conformer. However, the mechanism by which PrPSc causes neuronal dysfunction remains poorly understood. Levels of Shadoo (Sho), a protein that resembles the flexibly disordered N-terminal domain of PrPC, were found to be reduced in the brains of mice infected with the RML strain of prions [1], implying that Sho levels may reflect the presence of PrPSc in the brain. To test this hypothesis, we examined levels of Sho during prion infection using a variety of experimental systems. Sho protein levels were decreased in the brains of mice, hamsters, voles, and sheep infected with different natural and experimental prion strains. Furthermore, Sho levels were decreased in the brains of prion-infected, transgenic mice overexpressing Sho and in infected neuroblastoma cells. Time-course experiments revealed that Sho levels were inversely proportional to levels of protease-resistant PrPSc. Membrane anchoring and the N-terminal domain of PrP both influenced the inverse relationship between Sho and PrPSc. Although increased Sho levels had no discernible effect on prion replication in mice, we conclude that Sho is the first non-PrP marker specific for prion disease. Additional studies using this paradigm may provide insight into the cellular pathways and systems subverted by PrPSc during prion disease. Shadoo is a protein that resembles the prion protein, which causes prion diseases such as Creutzfeldt-Jakob disease in humans and “mad cow” disease. In this paper, we demonstrate that during prion disease in animals, levels of Shadoo were reduced in the brain and correlated with levels of infectious prions. This phenomenon occurred following infection with 14 different prion strains but was not observed following the accumulation of other aggregated proteins, including those that cause Alzheimer's disease and Parkinson's disease. Thus, Shadoo levels in the brain are a specific indicator of prion disease status, and it may be possible to exploit this observation for diagnostic purposes. Although we show that Shadoo itself is unlikely to influence prion disease, using Shadoo as a tool to probe the biology of prions may be a useful strategy for deciphering how prions damage the brain.
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Affiliation(s)
- Joel C. Watts
- Institute for Neurodegenerative Diseases, University of California, San Francisco, San Francisco, California, United States of America
| | - Jan Stöhr
- Institute for Neurodegenerative Diseases, University of California, San Francisco, San Francisco, California, United States of America
| | - Sumita Bhardwaj
- Institute for Neurodegenerative Diseases, University of California, San Francisco, San Francisco, California, United States of America
| | - Holger Wille
- Institute for Neurodegenerative Diseases, University of California, San Francisco, San Francisco, California, United States of America
- Department of Neurology, University of California, San Francisco, San Francisco, California, United States of America
| | - Abby Oehler
- Department of Pathology, University of California, San Francisco, San Francisco, California, United States of America
| | - Stephen J. DeArmond
- Institute for Neurodegenerative Diseases, University of California, San Francisco, San Francisco, California, United States of America
- Department of Pathology, University of California, San Francisco, San Francisco, California, United States of America
| | - Kurt Giles
- Institute for Neurodegenerative Diseases, University of California, San Francisco, San Francisco, California, United States of America
- Department of Neurology, University of California, San Francisco, San Francisco, California, United States of America
| | - Stanley B. Prusiner
- Institute for Neurodegenerative Diseases, University of California, San Francisco, San Francisco, California, United States of America
- Department of Neurology, University of California, San Francisco, San Francisco, California, United States of America
- * E-mail:
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Miyazawa K, Emmerling K, Manuelidis L. Replication and spread of CJD, kuru and scrapie agents in vivo and in cell culture. Virulence 2011; 2:188-99. [PMID: 21527829 DOI: 10.4161/viru.2.3.15880] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Transmissible Spongiform Encephalopathy (TSE) agents are defined by their virulence for particular species, their spread in the population, their incubation time to cause disease, and their neuropathological sequelae. Murine adapted human agents, including sporadic CJD (sCJD), New Guinea kuru, and Japanese CJD agents, display particularly distinct incubation times and maximal infectious brain titers. They also induce agent-specific patterns of neurodegeneration. When these TSE agents are transmitted to cultured hypothalamic GT1 cells they maintain their unique identities. Nevertheless, the human kuru (kCJD) and Japanese FU-CJD agents, as well as the sheep 22L and 263K scrapie agents display doubling times that are 8x to 33x faster in cells than in brain, indicating release from complex innate immune responses. These data are most consistent with a foreign viral structure, rather than an infectious form of host prion protein (PrP-res). Profound agent-specific inhibitory effects are also apparent in GT1 cells, and maximal titer plateau in kCJD and FU-CJD differed by 1,000-fold in a cell-based assay. Remarkably, the lower titer kCJD agent rapidly induced de novo PrP-res in GT1 cells, whereas the high titer FU-CJD agent replicated silently for multiple passages. Although PrP-res is often considered to be toxic, PrP-res instead may be part of a primal defense and/or clearance mechanism against TSE environmental agents. Limited spread of particular TSE agents through nanotubes and cell-to-cell contacts probably underlies the long peripheral phase of human CJD.
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Affiliation(s)
- Kohtaro Miyazawa
- Yale Medical School, Section of Neuropathology, New Haven, CT, USA
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Wang H, Wan J, Wang W, Wang D, Li S, Liao P, Hao Z, Wu S, Xu J, Li N, Ouyang H, Gao H. Overexpression of Shadoo protein in transgenic mice does not impact the pathogenesis of scrapie. Neurosci Lett 2011; 496:1-4. [PMID: 21458534 DOI: 10.1016/j.neulet.2011.03.073] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2011] [Revised: 03/24/2011] [Accepted: 03/24/2011] [Indexed: 11/19/2022]
Abstract
Shadoo is a glycoprotein expressed in the adult brain that is an interacting protein of prion protein; however, its function remains to be determined. To elucidate its role in prion pathogenesis, we generated transgenic mice overexpressing wild-type (wt) Shadoo driven by the murine PrP promoter. Expression of the murine Sprn transgene significantly increased brain Shadoo protein levels in all three mouse lines generated. Following infection with mouse-adapted scrapie strain 22L, all transgenic mice tested exhibited characteristics of scrapie disease. Importantly, there was no correlation between the expression level or incubation time of Shadoo with disease phenotype. We therefore conclude that Shadoo has little or no influence on the outcome of transmissible spongiform encephalopathy (TSE) disease in transgenic mice.
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Affiliation(s)
- Haiying Wang
- Department of Animal Biotechnology, College of Animal Science and Veterinary Medicine, Jilin University, Changchun 130062, China
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Westaway D, Daude N, Wohlgemuth S, Harrison P. The PrP-Like Proteins Shadoo and Doppel. Top Curr Chem (Cham) 2011; 305:225-56. [DOI: 10.1007/128_2011_190] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/08/2022]
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