ABSTRACT
An early hallmark of Alzheimer's disease is the accumulation of amyloid-ß (Aß), inspiring numerous therapeutic strategies targeting this peptide. An alternative approach is to destabilize the amyloid beta precursor protein (APP) from which Aß is derived. We interrogated innate pathways governing APP stability using a siRNA screen for modifiers whose own reduction diminished APP in human cell lines and transgenic Drosophila. As proof of principle, we validated PKCß-a known modifier identified by the screen-in an APP transgenic mouse model. PKCß was genetically targeted using a novel adeno-associated virus shuttle vector to deliver microRNA-adapted shRNA via intracranial injection. In vivo reduction of PKCß initially diminished APP and delayed plaque formation. Despite persistent PKCß suppression, the effect on APP and amyloid diminished over time. Our study advances this approach for mining druggable modifiers of disease-associated proteins, while cautioning that prolonged in vivo validation may be needed to reveal emergent limitations on efficacy.
Subject(s)
Alzheimer Disease/metabolism , Amyloid beta-Peptides/metabolism , Amyloid beta-Protein Precursor/metabolism , Amyloidosis/metabolism , Protein Kinase C beta/antagonists & inhibitors , Alzheimer Disease/genetics , Amyloidosis/therapy , Animals , Brain/metabolism , Brain/pathology , Cell Line, Tumor , Disease Models, Animal , Drosophila , Genetic Testing , Genetic Therapy , Humans , Mice , Mice, Transgenic , NIH 3T3 Cells , Phosphorylation , Plaque, Amyloid/pathology , Protein Kinase C beta/genetics , Protein Kinase C beta/metabolism , Protein Kinases/genetics , Protein Kinases/metabolism , RNA Interference , RNA, Small Interfering/genetics , RNA, Small Interfering/metabolismABSTRACT
To gain insight into how mutant huntingtin (mHtt) CAG repeat length modifies Huntington's disease (HD) pathogenesis, we profiled mRNA in over 600 brain and peripheral tissue samples from HD knock-in mice with increasing CAG repeat lengths. We found repeat length-dependent transcriptional signatures to be prominent in the striatum, less so in cortex, and minimal in the liver. Coexpression network analyses revealed 13 striatal and 5 cortical modules that correlated highly with CAG length and age, and that were preserved in HD models and sometimes in patients. Top striatal modules implicated mHtt CAG length and age in graded impairment in the expression of identity genes for striatal medium spiny neurons and in dysregulation of cyclic AMP signaling, cell death and protocadherin genes. We used proteomics to confirm 790 genes and 5 striatal modules with CAG length-dependent dysregulation at the protein level, and validated 22 striatal module genes as modifiers of mHtt toxicities in vivo.
