The prion protein and neuronal zinc homeostasis

Altered behavioural response to acute stress in mice lacking cellular prion protein

Although many studies have investigated the function of cellular prion protein (PrPc), its physiologic role remains elusive. PrPc null mice have been reported to develop normally and to show normal performance in most behavioural tests. In the present study we investigated whether this also holds true after episodes of acute stress. PrPc gene ablated (Prnp0/0) and wild-type mice were subjected to restraint stress, electric foot shock, or swimming and compared with non-stressed animals. Immediately after the stressful situation, the anxiety levels and locomotion of the animals were measured using plus-maze and open-field tests. Among non-stressed animals, there was no significant difference in performance between Prnp0/0 and wild type animals in either test. However, after acute stress provoked by a foot shock or a swimming trial, Prnp0/0 animals showed a significant decrease in anxiety levels when compared with control animals. Moreover, after the swimming test, knockout mice presented decreased locomotion when compared to wild-type mice. Because of this observation, we also assessed both types of mice in a forced swimming test with the objective of better evaluating muscle function and found that Prnp0/0 animals presented reduced forced swimming capacity when compared to controls. As far as we know, this is the first report suggesting that cellular prion protein is involved in modulation of anxiety or muscular activity after acute psychic or physical stress.

Amyloid accomplices and enforcers

Amyloid-related diseases are often ascribed to protein "misfolding." Yet in the absence of high-resolution structures for mature fibrils or intermediates, the connection between the mechanism of amyloid formation and protein folding remains tenuous. The simplistic view of amyloid fibrillogenesis as a homogeneous self-assembly process is being increasingly challenged by observations that amyloids interact with a variety of cofactors including metals, glycosaminoglycans, glycoproteins such as serum amyloid P and apolipo-protein E, and constituents of basement membranes such as perlecan, laminin, and agrin. These "pathological chaperones" have effects that range from mediating the rate of amyloid fibril formation to increasing the stability of amyloid deposits, and may contribute to amyloid toxicity. An increasing appreciation of the role of accessory molecules in amyloid etiology has paved the way to novel diagnostics and therapeutic strategies.

Polymorphisms of the PRNP gene in Chinese populations and the identification of a novel insertion mutation

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.