RESUMO
Proteinaceous inclusions are common hallmarks of many neurodegenerative diseases. TDP-43 proteinopathies, consisting of several neurodegenerative diseases, including frontotemporal lobar dementia (FTLD) and amyotrophic lateral sclerosis (ALS), are characterized by inclusion bodies formed by polyubiquitinated and hyperphosphorylated full-length and truncated TDP-43. The structural properties of TDP-43 aggregates and their relationship to pathogenesis are still ambiguous. Here we demonstrate that the recombinant full-length human TDP-43 forms structurally stable, spherical oligomers that share common epitopes with an anti-amyloid oligomer-specific antibody. The TDP-43 oligomers are stable, have exposed hydrophobic surfaces, exhibit reduced DNA binding capability and are neurotoxic in vitro and in vivo. Moreover, TDP-43 oligomers are capable of cross-seeding Alzheimer's amyloid-ß to form amyloid oligomers, demonstrating interconvertibility between the amyloid species. Such oligomers are present in the forebrain of transgenic TDP-43 mice and FTLD-TDP patients. Our results suggest that aside from filamentous aggregates, TDP-43 oligomers may play a role in TDP-43 pathogenesis.
Assuntos
Amiloide/química , Córtex Cerebral/patologia , Proteínas de Ligação a DNA/química , Demência Frontotemporal/patologia , Agregação Patológica de Proteínas/patologia , Proteinopatias TDP-43/patologia , Sequência de Aminoácidos , Amiloide/imunologia , Animais , Anticorpos Monoclonais/biossíntese , Anticorpos Monoclonais/química , Linhagem Celular Tumoral , Córtex Cerebral/química , Córtex Cerebral/imunologia , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/imunologia , Embrião de Mamíferos , Epitopos/química , Epitopos/imunologia , Escherichia coli/genética , Escherichia coli/metabolismo , Demência Frontotemporal/genética , Demência Frontotemporal/imunologia , Expressão Gênica , Células HEK293 , Humanos , Injeções Intraventriculares , Masculino , Camundongos , Dados de Sequência Molecular , Neurônios/química , Neurônios/imunologia , Neurônios/patologia , Cultura Primária de Células , Agregados Proteicos , Agregação Patológica de Proteínas/genética , Agregação Patológica de Proteínas/imunologia , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/imunologia , Proteinopatias TDP-43/genética , Proteinopatias TDP-43/imunologiaRESUMO
The deposition of amyloid-ß (Aß) peptide, which is generated from amyloid precursor protein (APP), is the pathological hallmark of Alzheimer's disease (AD). Three APP familial AD mutations (D678H, D678N, and H677R) located at the sixth and seventh amino acid of Aß have distinct effect on Aß aggregation, but their influence on the physiological and pathological roles of APP remain unclear. We found that the D678H mutation strongly enhances amyloidogenic cleavage of APP, thus increasing the production of Aß. This enhancement of amyloidogenic cleavage is likely because of the acceleration of APPD678H sorting into the endosomal-lysosomal pathway. In contrast, the APPD678N and APPH677R mutants do not cause the same effects. Therefore, this study indicates a regulatory role of D678H in APP sorting and processing, and provides genetic evidence for the importance of APP sorting in AD pathogenesis. The internalization of amyloid precursor protein (APP) increases its opportunity to be processed by ß-secretase and to produce Amyloid-ß (Aß) that causes Alzheimer's disease (AD). We report a pathogenic APPD678H mutant that enhances APP internalization into the endosomal-lysosomal pathway and thus promotes the ß-secretase cleavage and Aß production. This study provides genetic evidence for the importance of APP sorting in AD pathogenesis.
Assuntos
Doença de Alzheimer/genética , Peptídeos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/genética , Precursor de Proteína beta-Amiloide/metabolismo , Mutação/genética , Cloreto de Amônio/farmacologia , Biotinilação , Células HEK293 , Humanos , Lisossomos/efeitos dos fármacos , Lisossomos/genética , Lisossomos/metabolismo , Fragmentos de Peptídeos/metabolismo , Transporte Proteico/efeitos dos fármacos , Transporte Proteico/genética , TransfecçãoRESUMO
Amyloid precursor protein (APP) mutations associated with familial Alzheimer's disease (AD) usually lead to increases in amyloid ß-protein (Aß) levels or aggregation. Here, we identified a novel APP mutation, located within the Aß sequence (Aß(D7H)), in a Taiwanese family with early onset AD and explored the pathogenicity of this mutation. Cellular and biochemical analysis reveal that this mutation increased Aß production, Aß42/40 ratio and prolonged Aß42 oligomer state with higher neurotoxicity. Because the D7H mutant Aß has an additional metal ion-coordinating residue, histidine, we speculate that this mutation may promote susceptibility of Aß to ion. When co-incubated with Zn(2+) or Cu(2+), Aß(D7H) aggregated into low molecular weight oligomers. Together, the D7H mutation could contribute to AD pathology through a "double punch" effect on elevating both Aß production and oligomerization. Although the pathogenic nature of this mutation needs further confirmation, our findings suggest that the Aß N-terminal region potentially modulates APP processing and Aß aggregation, and further provides a genetic indication of the importance of Zn(2+) and Cu(2+) in the etiology of AD.
