nervous system. But as in all biological matters, the facts are multifactorial: genetic factors, hormonal factors, etc. intervene as do factors which are extrinsic to the organ- ism, and specifically, in this case, the role of PrPC which has not yet been studied. For this reason, this study is pioneering, as it shows differences with regard to the level of cellularprionprotein in the two sexes in rodents.
acts as the cell-surface receptor for the cellularprionprotein (Gauczynski et al., 2001b). Direct and heparan sulfate proteoglycan (HSPG)-dependent interaction sites mediating the binding of cellular PrP to its receptor have been identified (Hundt et al., 2001). Cell culture experiments demonstrated the 37-kDa/67-kDa LR dependent binding and internalization of recombinant GST::human PrP generated in insect cells and glycosylated human PrP synthesized in BHK cells transfected with recombinant SFV-RNA (Gauczynski et al., 2001b). High-level expression and purification of recombinant, glycosylated prion proteins in mammalian cells is essential for a better understanding of the physiological function of PrPc and biochemical processes responsible for familial prion diseases. The synthesis and study of wild-type as well as mutant PrP in cell culture systems allows a better insight into the biology of these proteins due to the presence of important organelles, membranes and other cellular cofactors which are necessary for the correct processing, trafficking and localization of the protein. Therefore, we used the Semliki Forest virus (SFV) system to express high amounts of glycosylated wild-type and mutant disease-associated prionprotein in cultured mammalian cells. The SFV system supplies a multitude of advantages for the expression of recombinant proteins in mammalian cells: (i) a large-scale production for up to 72 hours post-transfection, (ii) a broad host range, (iii) modifications such as glycosylation in a correct and sufficient way and (iv) the easy and fast transfection procedure with in vitro-transcribed RNA. The Semliki Forest virus is an insect-borne alphavirus and belongs to the family of Togaviridae (Schlesinger, 1986). Its viral genome consists of capped and polyadenylated single-stranded RNA of positive polarity and encodes its own RNA polymerase. SFV expression vectors are based on a cDNA copy of the viral genome. Here, viral structural genes are deleted and replaced by the gene of interest. Due to the remaining viral replicase which leads to an efficient production of recombinant RNA within the cell, a high-level synthesis of the foreign protein proceeds (Liljestrom and Garoff, 1991).
In addition to its presence in the insoluble fibrillar pla- ques, which characterize AD, β-amyloid exists in the brain in the form of soluble Aβ oligomers . While early AD research focused on Aβ plaques as the neuro- toxic species , recent evidence suggests that plaques may actually be a physiological ‘end point’ of limited harmfulness, while soluble oligomeric Aβ isoforms, in particular the Aβ42 fragment, are the primary source of neurotoxicity [21,22]. The accumulation of Aβ oligomers predominantly occurs in brain regions associated with learning and memory, including the hippocampus, and binds to sites that are located at neuronal synapses to cause the disruption to neuronal signaling and ultimately neuronal cell death [23,24]. A number of Aβ oligomer binding sites have been proposed, encompassing, but not limited to, glutamate receptors (both ionotropic and metabotropic), insulin receptors, acetylcholine receptors (both muscarinic and nicotinic), as well as cellularprionprotein (PrP c ) which may function as a co-receptor for Aβ [9,25-28]. Although the precise binding site remains controversial, Aβ oligomers presumably act via multiple receptors at synapse, thereby contributing to the range of issues that characterize AD.
N-Methyl-D-aspartate receptors (NMDARs) and α -amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) are two major types of ionotropic glutamate receptors involved in synaptic transmission. However, excessive activity of these receptors can be cytotoxic and thus their function must be precisely controlled. We have previously reported that NMDA receptor activity is dysregulated following genetic knockout of cellularprionprotein (PrP C ), and that PrP C regulation of NMDA receptors is copper-dependent. Here, we employed electrophysiological methods to study NMDAR and AMPAR currents of cultured hippocampal neurons from PrP C overexpresser mice. We show that NMDA receptor current amplitude and kinetics are differentially modulated by overexpression of human or mouse PrP C . By contrast, AMPA receptor activity was unaffected. Nonetheless, AMPA receptor activity was modulated by copper ions in a manner similar to what we previously reported for NMDA receptors. Taken together, our findings reveal that AMPA and NMDA receptors are differentially regulated by PrP C , but share common
HCl, pH 7.2, 100 m M NaCl, 10 m M EDTA at 10 6 cells/ml. Cell debris was removed from by centrifugation (1000 ⫻ g for 5 min), and the supernatant was incubated with a mAb to PrP (4F2) for 30 min at 4 °C on rollers. Magnetic microbeads con- taining protein G (Miltenyi Biotech) were added (10 l/ml) for 30 min, and protein G-bound antibody complexes were isolated using a MACS magnetic system (Miltenyi Biotech) at 4 °C. The amounts of sialylated gangliosides in precipitates were determined by diluting precipitates from 10 6 cells in 1 ml of carbonate buffer and plating in Maxisorb immunoplates over- night. The plates were blocked with 5% milk powder in PBS- Tween, and sialylated gangliosides were detected by the addition of biotinylated S. nigra lectin followed by extravidin- alkaline phosphatase and 1 mg/ml 4-nitrophenyl phosphate. Absorbance was measured on a microplate reader at 405 nm. Gangliosides within immunoprecipitates were separated by
The tooth organ is a unique system containing neural crest de- rived mesenchyme and ectoderm derived epithelia that differentiate through reciprocal signaling interactions to form the mineralized dentin and enamel tissues. Dentin, formed by the mesenchymally derived odontoblasts is a collagenous mineralized tissue with many of the similar characteristics as bone. Enamel is the only mineral- ized epithelial-derived tissue in the human body, and is initially formed as a protein matrix. Enamel matrix proteins immediately attract minerals to initiate mineralization. Enamel proteins are then removed through the actions of proteinases and the overly- ing ameloblasts, which commit apoptosis as teeth erupt. A hard acellular mineral enamel structure is formed to protect dentin and pulp complex. As described in this study, we used the tooth organ to identify the effects of PrP C on epithelially and mesenchymally
including insolubility and a relative resistance to proteinase K (PK) (21, 27). It has also been reported that misfolded PrP in the ER is subjected to ER quality control, leading to its ret- rotranslocation and accumulation within the cytosol, as evi- denced under conditions of proteasome inhibition (23), al- though whether it is poor translocation into the ER rather than active retrotranslocation is currently under debate (13, 31, 34). The accumulation of PrP within the cytosol is proposed to either initiate prion disease or act as a toxic element of disease. Both concepts are supported by the transgenic (Tg) 2D1 and 1D4 mouse lines, which express cyPrP and develop focal cer- ebellar atrophy and a unique phenotype (23). However, these mice lack spongiform change and PK-resistant PrP in the brain. The latter feature does not exclude this as a prion disease, as there are clear examples of human forms of prion disease that do not develop obvious PK-resistant PrP (e.g., Gerstmann-Stra ¨ussler-Scheinker disease) and others that dis- play little to no spongiform change (e.g., fatal insomnia). As such, the role of cyPrP in prion disease requires further study. We asked two specific questions regarding the nature of cyPrP: (i) is the toxicity associated with its expression dependent on the coexpression of PrP C , and (ii) does it participate directly in
Even after more than 12 generations of backcrossing, a small part of the chromosome around the Prnp locus still stems from the 129 strain, raising the question whether any observed phenotypes were actually due to polymorphisms in genes flanking Prnp . Indeed, we found that SIRPα, a polymorphic Prnp -flanking gene, is actu- ally responsible for an alleged Prnp -/- phenotype: the in- hibition of macrophage phagocytosis of apoptotic cells that was observed in PrP C -deficient mice with mixed genetic background but not in co-isogenic Prnp -/- mice . Recently, a new PrP C -deficient mouse strain, Prnp ZH3/ZH3 , was produced in our lab using TALEN- mediated genome editing in fertilized mouse oocytes and maintained in a pure C57BL/6 J genetic background . These strictly co-isogenic C57BL/6 J- Prnp ZH3/ZH3 mice differ from wild-type mice only by eight deleted nucleotides in the Prnp reading frame. In an effort to improve the quality of studies on the function of the cel- lular prionprotein, we are distributing Prnp ZH3/ZH3 mice without requesting any kind of Material Transfer Agree- ment, hence enabling better-controlled future studies. In view of the broad availability of Prnp ZH3/ZH3 mice, we contend that the use of mixed-background PrP C -defi- cient mice is obsolete and liable to artifacts.
protein) mRNA in cell lines and human breast cancer samples, using publicly available data sets (8). Con- sistent with previous findings in breast tumor samples, triple-negative (TN) and basal-like breast cancer subtypes expressed the highest PRNP mRNA levels (Figure 1A and Supplemental Figure 1A). Within these groups, the highest PRNP expression was associated with claudin-low and mesenchymal signatures characteristic of mesenchymal-like TNBCs (Figure 1A). It has been suggested that tissue homogenates from mesenchymal-like TNBCs are enriched with stromal cells, but there was only a weak correlation between tumor purity and PRNP in TNBCs (r = 0.19; Supplemental Figure 1B), suggesting that the val- ues largely reflect cancer cell expression. Indeed, PRNP expression was also high in claudin-low/basal-B compared with luminal-like cell lines (Supplemental Figure 1, C–F). There was no association between gene copy number and mRNA expression in TCGA data sets (Figure 1B), but expression was weakly and inversely correlated with methylation of the PRNP genomic locus in TN cancer sample subtypes (Figure 1C) and cell lines (Supplemental Figure 1G), suggesting that epigenetic programming is a determinant of expression to some degree. In cell lines in which PrP C was readily detectable, protein expression was
Alzheimer ’ s disease (AD) is a devastating neurodegenerative disorder, afflicting more than one-third of people over the age of 85. While many therapies for AD are in late-stage clinical testing, rational drug design based on distinct signaling pathways in this disorder is only now emerging. Here we review the putative signaling pathway of amyloid-beta (A β ), by which the tyrosine kinase Fyn is activated via cell surface binding of A β oligomers to cellularprionprotein. Several lines of evidence implicate Fyn in the pathogenesis of AD, and its interaction with both A β and Tau renders Fyn a unique therapeutic target that addresses both of the major pathologic hallmarks of AD. We are currently enrolling patients in a phase Ib study of saracatinib (AZD0530), a small molecule inhibitor with high potency for Src and Fyn, for the treatment of AD. The results of this trial and a planned phase IIa multisite study will provide important data regarding the potential for this therapeutic strategy in AD.
The natural graphite powder (320 mesh) was purchased from Tianjin Guangfu Chemical Agent Co., Ltd. (Tianjin, China). KCl, KH 2 PO 4 , MgCl 2 , MgSO 4 , CaCl 2 , NaNO 3 , KMnO 4 , magnesium powder, and ammonium persulfate (APS) were purchased from Guoyao Co., Ltd (Shanghai, China). 1,1,1,3,3,3-Hexafluoro-2-propanol (HFIP), sodium borohy- dride (NaBH 4 ), H 2 SO 4 , HCl, nitric acid, hydrazine hydrate, ethanol, NaHCO 3 , NaOH, NaH 2 PO 4 , NaCl, and Na 2 HPO 4 were obtained from Xilong Chemical (Guangzhou, China). Chloroauric acid (HAuC1 4 ) and glucose were purchased from Sigma-Aldrich Co. (St Louis, MO, USA). Protein marker, glycine, Tris (hydroxymethyl) aminomethane, 2 × Native Loading buffer, and Coomassie brilliant blue stain were purchased from Sangon Biotech. Co. Ltd (Shanghai, China). Tetramethylethylenediamine (TEMED), 30% acrylamide (Acr-Bis), 4 × Tris HCl (pH 6.8), and 4 × Tris HCl (pH 8.8) were from Beyotime Biotechnology (Shanghai, China). The cellularprionprotein (PrP C ) peptide probe was synthesized
opportunity to control and characterize the biophysical state of aggregation-prone Aβ preparations prior to use. Since pioneering in vivo studies found that injection of synthetic Aβ-related peptides of undefined assembly can impair learning [22,23] and reduce synaptic transmission in the hippocampus of the rat brain , this approach has been exploited in order to examine the role of differ- ent Aβ assemblies. By comparing the relative activity of different soluble preparations of Aβ in these acute models it is hoped that it will be possible to determine the nature and actions of synaptic and memory disrupting assem- blies. These assemblies vary in primary sequence, size and putative generic conformation. They include monomers, low-n oligomers, larger oligomers such as Aβ derived dif- fusible ligands (ADDLs) [25,26] and globulomers , and protofibrils which are usually shorter and thinner than in- soluble amyloid fibrils  (Figure 1). Currently there is little agreement as to which, if any, of these assemblies is most culpable in causing synaptic plasticity and memory disruption. The present review examines recent evidence, including the actions of other amyloidogenic peptides and the possible involvement of cellularprionprotein (PrP C ) as a selective target of certain oligomers.
affects the dorsal motor nucleus of the glossopharyngeal vagus nerve, and the olfactory bulb and anterior olfactory nucleus, whereas stage II PD affects the medulla and the tegmentum of the pons, both of which are related to RBD. Consistent with our finding, other studies have identified an increased incidence of neurodegenerative diseases in RBD patients with disease progression. For example, the risk of developing into neurodegenerative diseases in idiopathic RBD patients is approximately 18% within 5 years and approximately 41% within 10 years, and most of those patients will develop PD or dementia with Lewy bodies (Doty et al., 1988; Hughes et al., 1992; Braak et al., 2003; Tolosa et al., 2009; Berg et al., 2012). Therefore, the occurrence of primary RBD in aged people may be related to synuclein disease. In this study, by examining CSF samples we found that the mRNA and protein levels of PrP were increased in the CSF of PD patients, suggesting a certain correlation between elevated PrP expression and PD, especially in PD patients with RBD. This study did have certain limitations. PrP expression in CSF should be detected in a larger number of PD patients, and the impact on the PD model of overexpression of PrP or deletion of PrP also requires further investigation. Exciting results have illustrated the effect of PrP on PD in a rat model via siRNA silencing of cellularprionprotein (Wang et al., 2016). Further studies could utilize similar gene-editing tools to elucidate the potential of CSF PrP in the clinical diagnosis of PD and PD with RBD.
In a recent report, results obtained in mice have led to the theory that administration of cytidyl-guanyl oligodeoxynucleotides (CpG- ODNs), which stimulate the innate immune system via toll-like receptor 9 (TLR9) signaling receptors on a variety of immune cells, may represent an applicable treatment regimen to delay prion dis- ease in humans (76). Here it was shown that the incubation period of prion disease was extended in mice multidose treated with CpG- ODNs for twenty days. It was concluded that stimulation of innate immunity accounts for this apparent anti-prion effect, possibly through induction of anti-PrP antibodies. However, this is diffi- cult to reconcile with several studies indicating that immune defi- ciencies of various sorts inhibit prion pathogenesis (24, 25, 30, 77). In addition, prion pathogenesis is unhampered in MyD88 –/– mice,
12. Chernoff YO, Derkach IL, Inge-Vechtomov SG. Multicopy SUP35 gene induces de-novo appearance of psi-like factors in the yeast Saccharomyces cerevisiae. Curr Genet. 1993 Sep;24(3):268-70. 13. Westaway D, DeArmond SJ, Cayetano-Canlas J, Groth D, Foster D, Yang SL, Torchia M, Carlson GA, Prusiner SB. Degeneration of skeletal muscle, peripheral nerves, and the central nervous system in transgenic mice overexpressing wild-type prion proteins. Cell. 1994 Jan 14;76(1):117- 29.
dependent signalling pathway. Spontaneous neurodegeneration in transgenic mice express- ing a PrP mutant without the N-terminal endoplasmic reticulum (ER)-targeting sequence indicated a toxic potential of PrP when located in cytosolic compartment (cytoPrP) (Ma et al., 2002). Toxicity of cytoPrP seems to be dependent on its association with cellular membranes (Wang et al., 2006) and its binding to Bcl-2, an antiapoptotic protein present at the cytosolic side of ER and mitochondrial membranes (Rambold et al., 2006). Might the toxic potential of misfolded PrP in the cytosol be relevant to the pathogenesis of prion dis- eases? Most recent information revealed an impairment of the ubiquitin-proteasome system (UPS) in prion-infected mice. In conjunction with in vitro and cell culture approaches, it was proposed that prion neurotoxicity is linked to PrP Sc oligomers, which translocate to the
The likelihood that refolding of PrP-sen occurs during conversion has lead to suggestions that chaparone proteins might be involved (67-70) as been documented for yeast prion phenomena (71). As noted above, the PrP conversion reaction is much more efficient if the PrP-res seed is pretreated with a mild denaturant that partially and reversibly unfolds the polypeptide chain. Recent experiments have shown that certain chaparone proteins can substitute for this partial denaturation step to promote the PrP-res-induced conversion reaction (22). On the other hand, none of the chaperone proteins tested induced the conversion of PrP-sen to PrP-res in the absence of a PrP- res seed. These results emphasize the importance of seeding by PrP-res and are consistent with the idea that PrP-sen is refolded during the conversion process. The stimulatory activity of certain chaparone proteins in vitro suggests that chaperones may be cofactors in the PrP conversion process in vivo.