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Recent evidence supports involvement of amylin and the amylin receptor in the pathogenesis of Alzheimer's disease (AD). We have previously shown that amylin receptor antagonist, AC253, improves spatial memory in AD mouse models. Herein, we generated and screened a peptide library and identified two short sequence amylin peptides (12-14 aa) that are proteolytically stable, brain penetrant when administered intraperitoneally, neuroprotective against Aβ toxicity and restore diminished levels of hippocampal long term potentiation in AD mice. Systemic administration of the peptides for five weeks in aged 5XFAD mice improved spatial memory, reduced amyloid plaque burden, and neuroinflammation. The common residue SQELHRLQTY within the peptides is an essential sequence for preservation of the beneficial effects of the fragments that we report here and constitutes a new pharmacological target. These findings suggest that the amylin receptor antagonism may represent a novel therapy for AD.

The functional impact of amyloid peptides (Aβs) on the vascular system is less understood despite these pathologic peptides are substantially deposited in the brain vasculature of Alzheimer's patients. Here we show substantial accumulation of Aβs 40 and 42 in the brain arterioles of Alzheimer's patients and of transgenic Alzheimer's mice. Purified Aβs 1-40 and 1-42 exhibited vascular regression activity in the in vivo animal models and vessel density was reversely correlated with numbers and sizes of amyloid plaques in human patients. A significant high number of vascular cells underwent cellular apoptosis in the brain vasculature of Alzheimer's patients. VEGF significantly prevented Aβ-induced endothelial apoptosis in vitro. Neuronal expression of VEGF in transgenic mice restored memory behavior of Alzheimer's. These findings provide conceptual implication of improvement of vascular functions as a novel therapeutic approach for the treatment of Alzheimer's disease.

The cellular prion protein, PrP(C), is neuroprotective in a number of settings and in particular prevents cerebellar degeneration mediated by CNS-expressed Doppel or internally deleted PrP ('DeltaPrP'). This paradigm has facilitated mapping of activity determinants in PrP(C) and implicated a cryptic PrP(C)-like protein, 'pi'. Shadoo (Sho) is a hypothetical GPI-anchored protein encoded by the Sprn gene, exhibiting homology and domain organization similar to the N-terminus of PrP. Here we demonstrate Sprn expression and Sho protein in the adult CNS. Sho expression overlaps PrP(C), but is low in cerebellar granular neurons (CGNs) containing PrP(C) and high in PrP(C)-deficient dendritic processes. In Prnp(0/0) CGNs, Sho transgenes were PrP(C)-like in their ability to counteract neurotoxic effects of either Doppel or DeltaPrP. Additionally, prion-infected mice exhibit a dramatic reduction in endogenous Sho protein. Sho is a candidate for pi, and since it engenders a PrP(C)-like neuroprotective activity, compromised neuroprotective activity resulting from reduced levels may exacerbate damage in prion infections. Sho may prove useful in deciphering several unresolved facets of prion biology.

The presenilin proteins (PS1 and PS2) and their interacting partners nicastrin, aph-1 (refs 4, 5) and pen-2 (ref. 5) form a series of high-molecular-mass, membrane-bound protein complexes that are necessary for gamma-secretase and epsilon-secretase cleavage of selected type 1 transmembrane proteins, including the amyloid precursor protein, Notch and cadherins. Modest cleavage activity can be generated by reconstituting these four proteins in yeast and Spodoptera frugiperda (sf9) cells. However, a critical but unanswered question about the biology of the presenilin complexes is how their activity is modulated in terms of substrate specificity and/or relative activities at the gamma and epsilon sites. A corollary to this question is whether additional proteins in the presenilin complexes might subsume these putative regulatory functions. The hypothesis that additional proteins might exist in the presenilin complexes is supported by the fact that enzymatically active complexes have a mass that is much greater than predicted for a 1:1:1:1 stoichiometric complex (at least 650 kDa observed, compared with about 220 kDa predicted). To address these questions we undertook a search for presenilin-interacting proteins that differentially affected gamma- and epsilon-site cleavage events. Here we report that TMP21, a member of the p24 cargo protein family, is a component of presenilin complexes and differentially regulates gamma-secretase cleavage without affecting epsilon-secretase activity.

Much evidence indicates that abnormal processing and extracellular deposition of amyloid-beta peptide (A beta), a proteolytic derivative of the beta-amyloid precursor protein (betaAPP), is central to the pathogenesis of Alzheimer's disease (reviewed in ref. 1). In the PDAPP transgenic mouse model of Alzheimer's disease, immunization with A beta causes a marked reduction in burden of the brain amyloid. Evidence that A beta immunization also reduces cognitive dysfunction in murine models of Alzheimer's disease would support the hypothesis that abnormal A beta processing is essential to the pathogenesis of Alzheimer's disease, and would encourage the development of other strategies directed at the 'amyloid cascade'. Here we show that A beta immunization reduces both deposition of cerebral fibrillar A beta and cognitive dysfunction in the TgCRND8 murine model of Alzheimer's disease without, however, altering total levels of A beta in the brain. This implies that either a approximately 50% reduction in dense-cored A beta plaques is sufficient to affect cognition, or that vaccination may modulate the activity/abundance of a small subpopulation of especially toxic A beta species.

The normal cellular form of prion protein (PrPC) is a precursor to the pathogenic protease-resistant forms (PrPSc) believed to cause scrapie, bovine spongiform encephalopathy (BSE) and Creutzfeldt-Jakob disease. Its amino terminus contains the octapeptide PHGGGWGQ, which is repeated four times and is among the best-preserved regions of mammalian PrPC. Here we show that the amino-terminal domain of PrPC exhibits five to six sites that bind copper (Cu(II)) presented as a glycine chelate. At neutral pH, binding occurs with positive cooperativity, with binding affinity compatible with estimates for extracellular, labile copper. Two lines of independently derived PrPC gene-ablated (Prnp0/0) mice exhibit severe reductions in the copper content of membrane-enriched brain extracts and similar reductions in synaptosomal and endosome-enriched subcellular fractions. Prnp0/0 mice also have altered cellular phenotypes, including a reduction in the activity of copper/zinc superoxide dismutase and altered electrophysiological responses in the presence of excess copper. These findings indicate that PrPC can exist in a Cu-metalloprotein form in vivo.

Gerstmann-Sträussler syndrome is a rare familial neurodegenerative condition that is vertically transmitted, in an apparently autosomal dominant way. It can also be horizontally transmitted to non-human primates and rodents through intracerebral inoculation of brain homogenates from patients with the disease. The exact incidence of the syndrome is unknown but is estimated to be between one and ten per hundred million. Patients initially suffer from ataxia or dementia and deteriorate until they die, in one to ten years. Protease-resistant prion protein (PrP) and PrP-immunoreactive amyloid plaques with characteristic morphology accumulate in the brains of these patients. Current diagnostic criteria for Gerstmann-Sträussler syndrome incorporate clinical and neuropathological features, as animal transmission studies can be unreliable. PrP is implicated in the pathogenesis and transmission of the condition and in scrapie, an equivalent animal disease. It was discovered by enriching scrapie-infected hamster brain fractions for infectivity. Because there is compelling evidence that the scrapie isoform of PrP is a necessary component of the infectious particle, it seemed possible that the PrP gene on the short arm of human chromosome 20 in Gerstmann-Sträussler syndrome might be abnormal. We show here that PrP codon 102 is linked to the putative gene for the syndrome in two pedigrees, providing the best evidence to date that this familial condition is inherited despite also being infectious, and that substitution of leucine for proline at PrP codon 102 may lead to the development of Gerstmann-Sträussler syndrome.

Retrovirus without oncogenes often exert their neoplastic potential as insertional mutagens of cellular proto-oncogenes. This may be associated with the production of chimaeric viral-host transcripts; in these cases; activated cellular genes can be identified by obtaining cDNA clones of bipartite RNAs. This approach was used in the analysis of chicken nephroblastomas induced by myeloblastosis-associated virus (MAV). One tumor contained a novel mRNA species initiated within a MAV LTR. cDNA cloning revealed that this mRNA encodes a protein of 189 amino acids, identical to that of normal human Ha-ras-1 at 185 positions, including positions implicated in oncogenic activation of ras proto-oncogenes; there are no differences between the coding sequences of presumably normal Ha-ras cDNA clones from chicken lymphoma RNA and the tumor-derived cDNAs. The chimaeric mRNA in the nephroblastoma is at least 25-fold more abundant than c-Ha-ras mRNA in normal kidney tissue, and a 21-kd ras-related protein is present in relatively large amounts in the tumor. We conclude that a quantitative change in c-Ha-ras gene expression results from an upstream insertion mutation and presumably contributes to tumorigenesis in this single case. Little or no increase in c-Ha-ras RNA or protein was observed in other nephroblastomas.

Human globin cDNA-derived recombinants with plasmid pCR1 have been prepared for use as specific hybridisation probes and for the partial sequencing of alpha-, beta- and gamma-globin genes.