Autologous stem cell transplantation led to significant improvement in cardiac function in patients undergoing off-pump coronary artery bypass grafting for ischemic cardiomyopathy. Further investigation is required to quantify the optimal timing and specific cellular effects of the therapy.

Aims: Several neurodegenerative disorders show alterations in glutamatergic synapses and increased susceptibility to excitotoxicity. Mounting evidence suggests a central role for the cellular prion protein (PrPC) in neuroprotection. Therefore, the loss of PrPC function occurring in prion disorders may contribute to the disease progression and neurodegeneration. Indeed, PrPC modulates N-methyl-d-aspartate receptors (NMDAR), thus preventing cell death. In this study, we show that PrPC and copper cooperatively inhibit NMDAR through S-nitrosylation, a post-translational modification resulting from the chemical reaction of nitric oxide (NO) with cysteines. Results: Comparing wild-type Prnp (Prnp+/+) and PrPC knockout (Prnp0/0) mouse hippocampi, we found that GluN1 and GluN2A S-nitrosylation decrease in Prnp0/0. Using organotypic hippocampal cultures, we found that copper chelation decreases NMDAR S-nitrosylation in Prnp+/+ but not in Prnp0/0. This suggests that PrPC requires copper to support the chemical reaction between NO and thiols. We explored PrPC-Cu neuroprotective role by evaluating neuron susceptibility to excitotoxicity in Prnp+/+ and Prnp0/0 cultures. We found that (i) PrPC-Cu modulates GluN2A-containing NMDAR, those inhibited by S-nitrosylation; (ii) PrPC and copper are interdependent to protect neurons from insults; (iii) neuronal NO synthase inhibition affects susceptibility in wild-type but not in Prnp0/0, while (iv) the addition of a NO donor enhances Prnp0/0 neurons survival. Innovation and Conclusions: Our results show that PrPC and copper support NMDAR S-nitrosylation and cooperatively exert neuroprotection. In addition to NMDAR, PrPC may also favor the S-nitrosylation of other proteins. Therefore, this mechanism may be investigated in the context of the different cellular processes in which PrPC is involved. Antioxid. Redox Signal. 22, 772–784.

Prion diseases are fatal neurodegenerative disorders caused by an aberrant accumulation of the misfolded cellular prion protein (PrPC) conformer, denoted as infectious scrapie isoform or PrPSc. In inherited human prion diseases, mutations in the open reading frame of the PrP gene (PRNP) are hypothesized to favor spontaneous generation of PrPSc in specific brain regions leading to neuronal cell degeneration and death. Here, we describe the NMR solution structure of the truncated recombinant human PrP from residue 90 to 231 carrying the Q212P mutation, which is believed to cause Gerstmann-Sträussler-Scheinker (GSS) syndrome, a familial prion disease. The secondary structure of the Q212P mutant consists of a flexible disordered tail (residues 90–124) and a globular domain (residues 125–231). The substitution of a glutamine by a proline at the position 212 introduces novel structural differences in comparison to the known wild-type PrP structures. The most remarkable differences involve the C-terminal end of the protein and the β2–α2 loop region. This structure might provide new insights into the early events of conformational transition of PrPC into PrPSc. Indeed, the spontaneous formation of prions in familial cases might be due to the disruptions of the hydrophobic core consisting of β2–α2 loop and α3 helix.

The intrinsically disordered protein α-synuclein aggregates into amyloid fibrils, a process known to be implicated in several neurodegenerative states. Partially folded forms of the protein are thought to trigger the aggregation process. Here, α-synuclein conformers are characterized by analysis of the charge-state distributions observed in electrospray-ionization mass spectrometry under negative-ion mode. It is found that, even at neutral pH, a small fraction of the molecular population is in a compact conformation. Several distinct partially folded forms are then identified under conditions that promote α-synuclein aggregation, such as solutions of simple and fluorinated alcohols. Specific intermediates accumulate at increasing concentrations of ethanol, hexafluoro-2-propanol, and trifluoroethanol. Finally, extensive folding induced by Cu(2+) binding is revealed by titrations in the presence of Cu(2+)-glycine. The data confirm the existence of a single, high-affinity binding site for Cu(2+). Because accumulation of this partially folded form correlates with enhancement of fibrillation kinetics, it is likely to represent an amyloidogenic intermediate in α-synuclein conformational transitions.