[Show abstract][Hide abstract] ABSTRACT: Because amyloidogenic proteins, such as prion protein, β-amyloid peptide and α-synuclein, are associated with a variety of diseases, methods for their detection are important. Recombinant prion protein (rPrP) can selectively induce aggregation of dihydrolipoic acid capped gold nanoparticles (DHLA-AuNPs), which reduces the absorbance of the DHLA-AuNPs and changes their color from red to blue. These changes were used for label-free qualitative and quantitative detection of amyloidogenic protein. The addition of NaCl improved the detection sensitivity considerably, and the detection limit was as low as 33 pmol/L.
[Show abstract][Hide abstract] ABSTRACT: Prion diseases are infectious fatal neurodegenerative diseases including Creutzfeldt-Jakob disease in humans and bovine spongiform encephalopathy in cattle. The misfolding and conversion of cellular PrP in such mammals into pathogenic PrP is believed to be the key procedure. Rabbits are among the few mammalian species that exhibit resistance to prion diseases, but little is known about the molecular mechanism underlying such resistance. Here, we report that the crowding agents Ficoll 70 and dextran 70 have different effects on fibrillization of the recombinant full-length PrPs from different species: although these agents dramatically promote fibril formation of the proteins from human and cow, they significantly inhibit fibrillization of the rabbit protein by stabilizing its native state. We also find that fibrils formed by the rabbit protein contain less β-sheet structure and more α-helix structure than those formed by the proteins from human and cow. In addition, amyloid fibrils formed by the rabbit protein do not generate a proteinase K-resistant fragment of 15-16-kDa, but those formed by the proteins from human and cow generate such proteinase K-resistant fragments. Together, these results suggest that the strong inhibition of fibrillization of the rabbit PrP by the crowded physiological environment and the absence of such a protease-resistant fragment for the rabbit protein could be two of the reasons why rabbits are resistant to prion diseases.
[Show abstract][Hide abstract] ABSTRACT: A strategy has been put forward to fabricate PEG-interspersed nitrilotriacetic acid (NTA)-functionalized QDs by one-step self-assembly using a mixture of self-synthesized NTA-terminated amphiphilic polymer and 1,2-Distearoyl-sn-Glycero-3-Phosphoethanolamine-N-[Carboxy(Polyethylene Glycol)2000] (DSPE-PEG-COOH). The process was highly reproducible for facile functionalization of QDs via simultaneous self-assembly of biocompatible PEG molecules onto their surface. An optimized molar ratio of NTA-terminated amphiphilic polymer to DSPE-PEG-COOH was used to obtain NTA-functionalized QDs for site-specific labeling of prion proteins (PrP(C)) expressed on cell surfaces. Fabricated NTA-functionalized QDs can be a good candidate used for real-time visualization of PrP(C) in single live cells so as to clarify the nosogenesis of pathogenic scrapie prion protein (PrP(Sc)).
[Show abstract][Hide abstract] ABSTRACT: To understand the role of a crowded physiological environment in the pathogenesis of neurodegenerative diseases, we report the following. 1) The formation of fibrous aggregates of the human Tau fragment Tau-(244-441), when hyperphosphorylated by glycogen synthase kinase-3beta, is dramatically facilitated by the addition of crowding agents. 2) Fibril formation of nonphosphorylated Tau-(244-441) is only promoted moderately by macromolecular crowding. 3) Macromolecular crowding dramatically accelerates amyloid formation by human prion protein. A sigmoidal equation has been used to fit these kinetic data, including published data of human alpha-synuclein, yielding lag times and apparent rate constants for the growth of fibrils for these amyloidogenic proteins. These biochemical data indicate that crowded cell-like environments significantly accelerate the nucleation step of fibril formation of human Tau fragment/human prion protein/human alpha-synuclein (a significant decrease in the lag time). These results can in principle be predicted based on some known data concerning protein concentration effects on fibril formation both in vitro and in vivo. Furthermore, macromolecular crowding causes human prion protein to form short fibrils and nonfibrillar particles with lower conformational stability and higher protease resistance activity, compared with those formed in dilute solutions. Our data demonstrate that a crowded physiological environment could play an important role in the pathogenesis of neurodegenerative diseases by accelerating amyloidogenic protein misfolding and inducing human prion fibril fragmentation, which is considered to be an essential step in prion replication.
[Show abstract][Hide abstract] ABSTRACT: The two common polymorphisms (385A > G: M129V and 655G > A: E219 K) in the human prion gene (PRNP) play important roles in the pathogenesis of Creutzfeldt-Jakob diseases. We screened a total of 626 individuals, who represent three ethnic populations of China, Han, Hui, and Uyghur, for the two polymorphisms. The frequencies of M/M homozygote at residue 129 in these three groups differ significantly. The Han has a much higher frequency (98%) than Hui (85%) and Uyghur (60%). On the other hand, the frequencies of the E/E at residue 219 are higher in Uyghur (98%) and Hui (96%) than in Han (90%). We also investigated two other less common variants of PRNP, a silent substitution at residue 117 (351A > G: A117A), and one octapeptide-repeat deletion (1-OPRD) in the octapeptide-coding region. We found three Uyghur individuals with silent substitution at residue 117. Four Hui (2.0%) and one Han (0.5%) donors were found to be heterozygous for 1-OPRD. A novel three extra-repeat (72 bp) insertion within the octapeptide-coding region was identified in one healthy 11-years-old Hui. Identical mutation was also found in her mother but not her father.
Full-text · Article · Nov 2004 · European Journal of HumanGenetics
[Show abstract][Hide abstract] ABSTRACT: Nitric oxide (NO) is a short-lived pleiotropic molecule involved in many physiological and pathological processes in the organism. As an important biologic mediator, nitric oxide has been focused in tumor study and therapy for its function in the process of tumor genesis, progression,and death. It is documented that nitric oxide plays a dual role:induction or suppression of tumorigenesis, which is dependent on different conditions, such as the concentration, time,and position of NO products. Tumor growth can be promoted by continuous low NO concentration, while cytotoxicity and apoptosis to tumor cells can be induced by quite high NO concentration. Currently, the concentration-dependent principle is the theoretical basis of tumor therapy mediated by NO. These tumor therapies can be classified into several types: firstly, drug treatments including chemotherapy, nitric oxide synthase inducer and inhibitor, together with related research from Chinese traditional medicine; secondly, radiotherapy and photodynamic therapy; thirdly, genic level therapy; and so on. Thus, the paper states the relationship and mechanism between NO and tumor, and summarizes research advances on tumor therapy via nitric oxide.
No preview · Article · May 2004 · Ai zheng = Aizheng = Chinese journal of cancer