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S J DeArmond

Publications and source records attributed to S J DeArmond.

At least 19 recordsLinked to original sources
PubMed2001

Inherited prion disease caused by the V210I mutation: transmission to transgenic mice.

OBJECTIVE: To describe the clinical and neuropathologic profile and determine the strain characteristics of familial Creutzfeldt-Jakob disease (fCJD) caused by a point mutation of the PRNP gene at codon 210 that results in a valine-to-isoleucine substitution in the prion protein (PrP). METHODS: The clinicopathologic features of four individuals from the United States who died of fCJD(V210I) were compared. Transgenic (Tg) mice expressing a chimeric human-mouse PrP transgene were inoculated with brain extracts from three fCJD(V210I) cases, sporadic CJD (sCJD), fCJD(E200K), and fatal familial insomnia (FFI), to compare prion strain characteristics. RESULTS: The clinicopathologic profile of fCJD(V210I) was variable among cases but shared similarities with sCJD. The pattern of PrP(Sc) deposition in the brains of Tg mice was similar to that caused by sCJD but different from that associated with fCJD(E200K) or FFI. CONCLUSIONS: Each of these prion diseases is characterized by a rapidly progressive dementia with myoclonus, periodic complexes on EEG, and spongiform change without PrP plaque deposition in the brain. The occurrence of a different PrP(Sc) phenotype with each PRNP mutation argues that each respective amino acid sequence substitution produces a different prion strain.

Animals↗
PubMed2001

Binding of neural cell adhesion molecules (N-CAMs) to the cellular prion protein.

To identify molecular interaction partners of the cellular prion protein (PrP(C)), we sought to apply an in situ crosslinking method that maintains the microenvironment of PrP(C). Mild formaldehyde crosslinking of mouse neuroblastoma cells (N2a) that are susceptible to prion infection revealed the presence of PrP(C) in high molecular mass (HMM) protein complexes of 200 to 225 kDa. LC/MS/MS analysis identified three murine splice-variants of the neural cell adhesion molecule (N-CAM) in the complexes, which isolate with caveolae-like domains (CLDs). Enzymatic removal of N-linked sugar moieties did not disrupt the complexes, arguing that the interaction of PrP with N-CAM occurs through amino acid side-chains. Additionally, similar levels of PrP/N-CAM complexes were found in N2a and prion-infected N2a (ScN2a) cells. With the use of an N-CAM-specific peptide library, the PrP-binding site was determined to comprise beta-strands C and C' within the two consecutive fibronectin type III (FNIII) modules found in proximity of the membrane-attachment site of N-CAM. As revealed by in situ crosslinking of PrP deletion mutants, the PrP face of the binding site is formed by the N terminus, helix A (residues 144-154) and the adjacent loop region of PrP. N-CAM-deficient (N-CAM(-/-)) mice that were intracerebrally challenged with scrapie prions succumbed to disease with a mean incubation period of 122 (+/-4.1, SEM) days, arguing that N-CAM is not involved in PrP(Sc) replication. Our findings raise the possibility that N-CAM may join with PrP(C) in carrying out some as yet unidentified physiologic cellular function.

Alternative Splicing↗
PubMed2001

Doppel-induced cerebellar degeneration in transgenic mice.

Doppel (Dpl) is a paralog of the mammalian prion protein (PrP); it is abundant in testes but expressed at low levels in the adult central nervous system. In two Prnp-deficient (Prnp(0/0)) mouse lines (Ngsk and Rcm0), Dpl overexpression correlated with ataxia and death of cerebellar neurons. To determine whether Dpl overexpression, rather than the dysregulation of genes neighboring the Prn gene complex, was responsible for the ataxic syndrome, we placed the mouse Dpl coding sequence under the control of the Prnp promoter and produced transgenic (Tg) mice on the Prnp(0/0)-ZrchI background (hereafter referred to as ZrchI). ZrchI mice exhibit neither Dpl overexpression nor cerebellar degeneration. In contrast, Tg(Dpl)ZrchI mice showed cerebellar granule and Purkinje cell loss; the age of onset of ataxia was inversely proportional to the levels of Dpl protein. Crosses of Tg mice overexpressing wild-type PrP with two lines of Tg(Dpl)ZrchI mice resulted in a phenotypic rescue of the ataxic syndrome, while Dpl overexpression was unchanged. Restoration of PrP expression also rendered the Tg(Dpl) mice susceptible to prion infection, with incubation times indistinguishable from non-Tg controls. Whereas the rescue of Dpl-induced neurotoxicity by coexpression of PrP argues for an interaction between the PrP and Dpl proteins in vivo, the unaltered incubation times in Tg mice overexpressing Dpl in the central nervous system suggest that Dpl is unlikely to be involved in prion formation.

Animals↗
PubMed2001

Mapping the early steps in the pH-induced conformational conversion of the prion protein.

Under certain conditions, the prion protein (PrP) undergoes a conformational change from the normal cellular isoform, PrP(C), to PrP(Sc), an infectious isoform capable of causing neurodegenerative diseases in many mammals. Conversion can be triggered by low pH, and in vivo this appears to take place in an endocytic pathway and/or caveolae-like domains. It has thus far been impossible to characterize the conformational change at high resolution by experimental methods. Therefore, to investigate the effect of acidic pH on PrP conformation, we have performed 10-ns molecular dynamics simulations of PrP(C) in water at neutral and low pH. The core of the protein is well maintained at neutral pH. At low pH, however, the protein is more dynamic, and the sheet-like structure increases both by lengthening of the native beta-sheet and by addition of a portion of the N terminus to widen the sheet by another two strands. The side chain of Met-129, a polymorphic codon in humans associated with variant Creutzfeldt-Jakob disease, pulls the N terminus into the sheet. Neutralization of Asp-178 at low pH removes interactions that inhibit conversion, which is consistent with the Asp-178-Asn mutation causing human prion diseases.

Animals↗
PubMed2001

Decreased MK-801 binding in discrete hippocampal regions of prion-infected mice.

The neurochemical alterations associated with neurodegeneration in prion diseases are not well defined. It is therefore of interest to study the influence of prion infection on messenger molecules and their receptors. In the present study we have analyzed the possible involvement of NMDA receptors in prion-infected mice using ligand binding autoradiography and iodinated MK-801, a noncompetitive NMDA antagonist. The results show a reduced binding of MK-801 in discrete regions of hippocampus at 110 days after infection, that is before the appearance of behavioral symptoms. In addition, early transient increases in MK-801 binding were observed in several layers. The exact neuroanatomical correlate of these changes in MK-801 binding, as well as its functional significance in relation to prion symptomatology, remain to be analyzed.

Animals↗
PubMed2001

Identification of two prion protein regions that modify scrapie incubation time.

A series of prion transmission experiments was performed in transgenic (Tg) mice expressing either wild-type, chimeric, or truncated prion protein (PrP) molecules. Following inoculation with Rocky Mountain Laboratory (RML) murine prions, scrapie incubation times for Tg(MoPrP)4053, Tg(MHM2)294/Prnp(0/0), and Tg(MoPrP, Delta23-88)9949/Prnp(0/0) mice were approximately 50, 120, and 160 days, respectively. Similar scrapie incubation times were obtained after inoculation of these lines of Tg mice with either MHM2(MHM2(RML)) or MoPrP(Delta23-88)(RML) prions, excluding the possibility that sequence-dependent transmission barriers could account for the observed differences. Tg(MHM2)294/Prnp(0/0) mice displayed prolonged scrapie incubation times with four different strains of murine prions. These data provide evidence that the N terminus of MoPrP and the chimeric region of MHM2 PrP (residues 108 through 111) both influence the inherent efficiency of prion propagation.

Animals↗
PubMed2001

A protease-resistant 61-residue prion peptide causes neurodegeneration in transgenic mice.

An abridged prion protein (PrP) molecule of 106 amino acids, designated PrP106, is capable of forming infectious miniprions in transgenic mice (S. Supattapone, P. Bosque, T. Muramoto, H. Wille, C. Aagaard, D. Peretz, H.-O. B. Nguyen, C. Heinrich, M. Torchia, J. Safar, F. E. Cohen, S. J. DeArmond, S. B. Prusiner, and M. Scott, Cell 96:869-878, 1999). We removed additional sequences from PrP106 and identified a 61-residue peptide, designated PrP61, that spontaneously adopted a protease-resistant conformation in neuroblastoma cells. Synthetic PrP61 bearing a carboxy-terminal lipid moiety polymerized into protease-resistant, beta-sheet-enriched amyloid fibrils at a physiological salt concentration. Transgenic mice expressing low levels of PrP61 died spontaneously with ataxia. Neuropathological examination revealed accumulation of protease-resistant PrP61 within neuronal dendrites and cell bodies, apparently causing apoptosis. PrP61 may be a useful model for deciphering the mechanism by which PrP molecules acquire protease resistance and become neurotoxic.

Animals↗
PubMed2000

Quantitative trait loci affecting prion incubation time in mice.

Although the gene encoding prion protein (PrP) is the major determinant of susceptibility to prion disease, other genes also affect prion incubation time in mice and may be involved in prion replication. Scrapie incubation time was analyzed as a quantitative trait using crosses between SJL/J and CAST/Ei mice; these mouse strains encode identical PrP molecules but have different incubation periods. Our analysis revealed loci on Chromosomes 9 and 11 that affect prion susceptibility.

Animals↗
PubMed2000

Selective neuronal vulnerability during experimental scrapie infection: insights from an ultrastructural investigation.

The goal was to test whether all neurons are equally susceptible to degeneration in response to PrP(Sc) scrapie infection. We tested this by immunogold GABA labeling. Our ultrastructural results indicates that GABAergic neurons are less vulnerable than other neuronal populations. This conclusion is supported by our findings: (1) reversal of the normal ratio of non-GABAergic to GABAergic neurons in the terminal stages, which implies that non-GABAergic neurons degenerated earlier, and (2) that the degeneration of GABAergic neurons occurs late in the disease after reactive astrogliosis, a response to nerve cell death.

Animals↗
PubMed2000

A synthetic peptide initiates Gerstmann-Sträussler-Scheinker (GSS) disease in transgenic mice.

The molecular basis of the infectious, inherited and sporadic forms of prion diseases is best explained by a conformationally dimorphic protein that can exist in distinct normal and disease-causing isoforms. We identified a 55-residue peptide of a mutant prion protein that can be refolded into at least two distinct conformations. When inoculated intracerebrally into the appropriate transgenic mouse host, 20 of 20 mice receiving the beta-form of this peptide developed signs of central nervous system dysfunction at approximately 360 days, with neurohistologic changes that are pathognomonic of Gerstmann-Sträussler-Scheinker disease. By contrast, eight of eight mice receiving a non-beta-form of the peptide failed to develop any neuropathologic changes more than 600 days after the peptide injections. We conclude that a chemically synthesized peptide refolded into the appropriate conformation can accelerate or possibly initiate prion disease.

Amino Acid Sequence↗
PubMed2000

Transgenic models of prion disease.

There is growing concern that bovine spongiform encephalopathy (BSE) may have passed from cattle to humans, resulting in approximately 70 cases of an atypical, variant CJD (vCJD) in teenagers and young adults. We report here that transgenic (Tg) mice expressing full-length bovine (Bo) PrP serially propagate BSE prions and that there is no species barrier for transmission from cattle to Tg(BoPrP) mice. Surprisingly, these same mice were also highly susceptible to vCJD and natural sheep scrapie. The incubation times (approximately 250 d), neuropathology, and PrP(Sc) isoforms in Tg(BoPrP) mice inoculated with vCJD and BSE brain extracts were indistinguishable and differed dramatically from those seen in these mice injected with natural scrapie. In efforts to identify PrP sequences required for prion formation, we found that a redacted prion protein of only 106 amino acids (PrP106) containing two large deletions supported prion propagation. In Tg(PrP106) mice, an artificial transmission barrier for the passage of full-length mouse prions was diminished by the coexpression of full-length wt MoPrP(C), suggesting that wt MoPrP acts in trans to accelerate the replication of "miniprions" containing PrP(Sc)106. Following a single passage (approximately 300 d) in Tg(PrP106) mice, the miniprions efficiently transmitted disease to Tg(PrP106) mice after only approximately 66 days. Our findings with Tg(BoPrP) mice provide compelling evidence that prions from cattle with BSE have infected humans and caused fatal neurodegeneration, the unique features of miniprions offer new insights into the mechanism of prion replication, and the trans-acting effects of full-length PrP coexpression suggest a new approach to the development of even more efficient animal models for prion diseases.

Animals↗
PubMed2000

Affinity-tagged miniprion derivatives spontaneously adopt protease-resistant conformations.

An abridged PrP molecule of 106 amino acids designated PrP106 can form infectious miniprions in transgenic (Tg) mice (29). Addition of six-histidine (His(6)) affinity tags to selective sites within PrP106 resulted unexpectedly in new PrP proteins that spontaneously adopted protease-resistant conformations when expressed in neuroblastoma cells and Tg mice. Acquisition of protease resistance depended on the length, charge, and placement of the affinity tag. Introduction of the disease-linked mutation E200K into the sequence of PrP106(140/6His) increased the recovery of protease-resistant PrP fivefold, whereas introduction of the mutations C213A and Delta214-220 did not affect the recovery of protease-resistant PrP. Treatment of cultured cells expressing affinity-tagged PrP106 mutants with polypropyleneimine dendrimer rendered these proteins sensitive to protease digestion in a manner similar to wild-type PrP(Sc). We conclude that certain affinity-tagged PrP106 proteins spontaneously fold into conformations partially resembling, yet distinct from, wild-type PrP(Sc). These proteins might be useful tools in the identification of new disease-causing mutations as well as for screening compounds for therapeutic efficacy.

Animals↗
PubMed1999

Compelling transgenetic evidence for transmission of bovine spongiform encephalopathy prions to humans.

There is growing concern that bovine spongiform encephalopathy (BSE) may have passed from cattle to humans. We report here that transgenic (Tg) mice expressing bovine (Bo) prion protein (PrP) serially propagate BSE prions and that there is no species barrier for transmission from cattle to Tg(BoPrP) mice. These same mice were also highly susceptible to a new variant of Creutzfeldt-Jakob disease (nvCJD) and natural sheep scrapie. The incubation times (approximately 250 days), neuropathology, and disease-causing PrP isoforms in Tg(BoPrP)Prnp(0/0) mice inoculated with nvCJD and BSE brain extracts were indistinguishable and differed dramatically from those seen in these mice injected with natural scrapie prions. Our findings provide the most compelling evidence to date that prions from cattle with BSE have infected humans and caused fatal neurodegeneration.

Animals↗
PubMed1999

Nerve growth factor signaling in caveolae-like domains at the plasma membrane.

Nerve growth factor (NGF) binding to its receptors TrkA and p75(NTR) enhances the survival, differentiation, and maintenance of neurons. Recent studies have suggested that NGF receptor activation may occur in caveolae or caveolae-like membranes (CLM). This is an intriguing possibility because caveolae have been shown to contain many of the signaling intermediates in the TrkA signaling cascade. To examine the membrane localization of TrkA and p75(NTR), we isolated caveolae from 3T3-TrkA-p75 cells and CLM from PC12 cells. Immunoblot analysis showed that TrkA and p75(NTR) were enriched about 13- and 25-fold, respectively, in caveolae and CLM. Binding and cross-linking studies demonstrated that the NGF binding to both TrkA and p75(NTR) was considerably enriched in CLM and that about 90% of high affinity binding to TrkA was present in CLM. When PC12 cells were treated with NGF, virtually all activated (i.e. tyrosine phosphorylated) TrkA was found in the CLM. Remarkably, in NGF-treated cells, it was only in CLM that activated TrkA was coimmunoprecipitated with phosphorylated Shc and PLCgamma. These results document a signaling role for TrkA in CLM and suggest that both TrkA and p75(NTR) signaling are initiated from these membranes.

Animals↗
PubMed1999

Transmissible and genetic prion diseases share a common pathway of neurodegeneration.

Prion diseases can be infectious, sporadic and genetic. The infectious forms of these diseases, including bovine spongiform encephalopathy and Creutzfeldt-Jakob disease, are usually characterized by the accumulation in the brain of the transmissible pathogen, an abnormally folded isoform of the prion protein (PrP) termed PrPSc. However, certain inherited PrP mutations appear to cause neurodegeneration in the absence of PrPSc, working instead by favoured synthesis of CtmPrP, a transmembrane form of PrP. The relationship between the neurodegeneration seen in transmissible prion diseases involving PrPSc and that associated with ctmPrP has remained unclear. Here we find that the effectiveness of accumulated PrPSc in causing neurodegenerative disease depends upon the predilection of host-encoded PrP to be made in the ctmPrP form. Furthermore, the time course of PrPSc accumulation in transmissible prion disease is followed closely by increased generation of CtmPrP. Thus, the accumulation of PrPSc appears to modulate in trans the events involved in generating or metabolising CtmPrP. Together, these data suggest that the events of CtmPrP-mediated neurodegeneration may represent a common step in the pathogenesis of genetic and infectious prion diseases.

Animals↗
PubMed1999

Prion protein of 106 residues creates an artifical transmission barrier for prion replication in transgenic mice.

A redacted prion protein (PrP) of 106 amino acids with two large deletions was expressed in transgenic (Tg) mice deficient for wild-type (wt) PrP (Prnp0/0) and supported prion propagation. RML prions containing full-length PrP(Sc)produced disease in Tg(PrP106)Prnp0/0 mice after approximately 300 days, while transmission of RML106 prions containing PrP(Sc)106 created disease in Tg(PrP106) Prnp0/0 mice after only approximately 66 days on repeated passage. This artificial transmission barrier for the passage of RML prions was diminished by the coexpression of wt MoPrPc in Tg(PrP106)Prnp+/0 mice that developed scrapie in approximately 165 days, suggesting that wt MoPrP acts in trans to accelerate replication of RML106 prions. Purified PrP(Sc)106 was protease resistant, formed filaments, and was insoluble in nondenaturing detergents. The unique features of RML106 prions offer insights into the mechanism of prion replication, and the small size of PrP(Sc)106 should facilitate structural analysis.

Amino Acid Sequence↗