Patrick Horne

Aβ peptide immunization reduces behavioural impairment and plaquesin a model of Alzheimer's disease

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

Therapeutically effective antibodies against amyloid-β peptide target amyloid-β residues 4−10 and inhibit cytotoxicity and fibrillogenesis

Immunization of transgenic mouse models of Alzheimer disease using amyloid-β peptide (Aβ) reduces both the Alzheimer disease–like neuropathology and the spatial memory impairments of these mice. However, a therapeutic trial of immunization with Aβ42 in humans was discontinued because a few patients developed significant meningo-encephalitic cellular inflammatory reactions. Here we show that beneficial effects in mice arise from antibodies selectively directed against residues 4–10 of Aβ42, and that these antibodies inhibit both Aβ fibrillogenesis and cytotoxicity without eliciting an inflammatory response. These findings provide the basis for improved immunization antigens as well as attempts to design small-molecule mimics as alternative therapies.

In vivo reduction of amyloid-β by a mutant copper transporter

Cu ions have been suggested to enhance the assembly and pathogenic potential of the Alzheimers disease amyloid-β (Aβ) peptide. To explore this relationship in vivo, toxic-milk (txJ) mice with a mutant ATPase7b transporter favoring elevated Cu levels were analyzed in combination with the transgenic (Tg) CRND8 amyloid precursor protein mice exhibiting robust Aβ deposition. Unexpectedly, TgCRND8 mice homozygous for the recessive txJ mutation examined at 6 months of age exhibited a reduced number of amyloid plaques and diminished plasma Aβ levels. In addition, homozygosity for txJ increased survival of young TgCRND8 mice and lowered endogenous CNS Aβ at times before detectable increases in Cu in the CNS. These data suggest that the beneficial effect of the txJ mutation on CNS Aβ burden may proceed by a previously undescribed mechanism, likely involving increased clearance of peripheral pools of Aβ peptide.

An immunological epitope selective for pathological monomer-misfolded SOD1 in ALS

Misfolding of Cu/Zn-superoxide dismutase (SOD1) is emerging as a mechanism underlying motor neuron degeneration in individuals with amyotrophic lateral sclerosis (ALS) who carry a mutant SOD1 gene (SOD1 ALS). Here we describe a structure-guided approach to developing an antibody that specifically recognizes monomer-misfolded forms of SOD1. We raised this antibody to an epitope that is normally buried in the SOD1 native homodimer interface. The SOD1 exposed dimer interface (SEDI) antibody recognizes only those SOD1 conformations in which the native dimer is disrupted or misfolded and thereby exposes the hydrophobic dimer interface. Using the SEDI antibody, we established the presence of monomer-misfolded SOD1 in three ALS mouse models, with G37R, G85R and G93A SOD1 mutations, and in a human individual with an A4V SOD1 mutation. Despite ubiquitous expression, misfolded SOD1 was found primarily within degenerating motor neurons. Misfolded SOD1 appeared before the onset of symptoms and decreased at the end stage of the disease, concomitant with motor neuron loss.

The CNS glycoprotein Shadoo has PrPC-like protective properties and displays reduced levels in prion infections

The cellular prion protein, PrPC, is neuroprotective in a number of settings and in particular prevents cerebellar degeneration mediated by CNS‐expressed Doppel or internally deleted PrP (‘ΔPrP’). This paradigm has facilitated mapping of activity determinants in PrPC and implicated a cryptic PrPC‐like protein, ‘π’. 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 PrPC, but is low in cerebellar granular neurons (CGNs) containing PrPC and high in PrPC‐deficient dendritic processes. In Prnp0/0 CGNs, Sho transgenes were PrPC‐like in their ability to counteract neurotoxic effects of either Doppel or ΔPrP. Additionally, prion‐infected mice exhibit a dramatic reduction in endogenous Sho protein. Sho is a candidate for π, and since it engenders a PrPC‐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 in Vivo Brain Interactome of the Amyloid Precursor Protein

Despite intense research efforts, the physiological function and molecular environment of the amyloid precursor protein has remained enigmatic. Here we describe the application of time-controlled transcardiac perfusion cross-linking, a method for the in vivo mapping of protein interactions in intact tissue, to study the interactome of the amyloid precursor protein (APP). To gain insights into the specificity of reported protein interactions the study was extended to the mammalian amyloid precursor-like proteins (APLP1 and APLP2). To rule out sampling bias as an explanation for differences in the individual datasets, a small scale quantitative iTRAQ (isobaric tags for relative and absolute quantitation)-based comparison of APP, APLP1, and APLP2 interactomes was carried out. An interactome map was derived that confirmed eight previously reported interactions of APP and revealed the identity of more than 30 additional proteins that reside in spatial proximity to APP in the brain. Subsequent validation studies confirmed a physiological interaction between APP and leucine-rich repeat and Ig domain-containing protein 1, demonstrated a strong influence of Ig domain-containing protein 1 on the proteolytic processing of APP, and consolidated similarities in the biology of APP and p75.

Lack of TDP-43 abnormalities in mutant SOD1 transgenic mice shows disparity with ALS.

Mislocalization of the TAR-DNA binding protein (TDP-43) from the nucleus to the cytoplasm of diseased motor neurons and association with intraneuronal ubiquitinated inclusions has recently been reported in amyotrophic lateral sclerosis (ALS). Here, we have investigated TDP-43 immunoreactivity in three lines of mutant SOD1 transgenic mice, G93A, G37R and G85R and compared with labeling in one sporadic ALS case and two familial ALS cases carrying mutations in SOD1, A4T and I113T. Our findings show that there is no mislocalization of TDP-43 to the cytoplasm in motor neurons of mutant SOD1 transgenic mice, nor association of TDP-43 with ubiquitinated inclusions. In contrast, mislocalization of TDP-43 to the cytoplasm and association with ubiquitinated inclusions was found in the ALS cases, including those carrying mutations in SOD1. Interestingly, there was no association of TDP-43 with ubiquitinated hyaline conglomerate inclusions, pathology closely associated with ALS cases carrying mutations in SOD1. Our findings indicate that the process of motor neuron degeneration in mutant SOD1 transgenic mice is unlikely to involve the abnormalities of TDP-43 described in the human disease.

Lack of evidence of monomer/misfolded superoxide dismutase-1 in sporadic amyotrophic lateral sclerosis

In familial amyotrophic lateral sclerosis (fALS) harboring superoxide dismutase (SOD1) mutations (fALS1), SOD1 toxicity has been linked to its propensity to misfold and aggregate. It has recently been proposed that misfolded SOD1 may be causative of all types of ALS, including sporadic cases (sALS). In the present study, we have used a specific antibody to test for the presence of monomer/misfolded SOD1 in sALS.

An aggregate-inducing peripherin isoform generated through intron retention is upregulated in amyotrophic lateral sclerosis and associated with disease pathology.

The neuronal intermediate filament protein peripherin is a component of ubiquitinated inclusions and of axonal spheroids in amyotrophic lateral sclerosis (ALS). Overexpression of peripherin causes motor neuron degeneration in transgenic mice and variations within the peripherin gene have been identified in ALS cases. We have shown previously the abnormal expression of a neurotoxic peripherin splice variant in transgenic mice expressing mutant superoxide dismutase-1. These findings indicated that abnormalities of peripherin splicing may occur in ALS. In the current study, peripherin splice variants were identified by reverse transcription-PCR of human neuronal RNA and comparisons in expression made between control and ALS spinal cord using Western blot analysis and immunocytochemistry. Using this approach we have identified a novel peripherin transcript retaining introns 3 and 4 that results in a 28 kDa splice isoform, designated Per 28. Using an antibody specific to Per 28, we show that this isoform is expressed at low stoichiometric levels from the peripherin gene, however causes peripherin aggregation when its expression is upregulated. Importantly we show an upregulation of Per 28 expression in ALS compared with controls, at both the mRNA and protein levels, and that Per 28 is associated with disease pathology, specifically round inclusions. These findings are the first to establish that peripherin splicing abnormalities occur in ALS, generating aggregation-prone splice isoforms.

A review of the evidence of human endoparasitism in the pre-Columbian new world through the study of coprolites

Abstract A review of helminth eggs encountered in precontact, human coprolites and palaeofaecal material from mummified human remains of the New World is presented. Included is a brief description of parasites and their effects on the host from the three phyla represented, Nematoda (roundworms), Platyhelminthes (flatworms) and Acanthocephala (thorny-headed worms).