Cell death cascade and molecular therapy in ADAR2-deficient motor neurons of ALS

• Published in: Neuroscience research Vol. 144; pp. 4 - 13
• Main Authors: Yamashita, Takenari, Kwak, Shin
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier B.V 01-07-2019
• Subjects: Adeno-associated virus (AAV); Adenosine deaminase acting on RNA 2 (ADAR2); Amyotrophic lateral sclerosis (ALS); Ca2+-permeability; Cell death cascade; Nuclear pore complex (NPC); Nucleoporin (Nup); RNA editing; NPC; BBB; Nuclear pore complex (NPC); TCS; ALS; Pol II Ser2; KPN; Adenosine deaminase acting on RNA 2 (ADAR2); C9ORF72; Nucleoporin (Nup); Cell death cascade; Q/R; A-to-I; Ca2+-permeability; CLSM; AAV9; dsRNA; Adeno-associated virus (AAV); AR2; RNA editing; FUS; Amyotrophic lateral sclerosis (ALS); STED; FTLD; Nup; CRM1; ADAR2; SOD1; AMPARs; RanBP1; CAS; TDP-43; AAV; G4C2; VAChT; Ca(2+)-permeability
• ISSN: 0168-0102; 1872-8111
• DOI: 10.1016/j.neures.2018.06.004

[Display omitted]
•Disruption of nuclear pore complex (NPC) plays a pivotal pathogenic role in ALS.•Nucleoporins, the NPC components, are cleaved by Ca2+-dependent protease calpain.•ALS motor neurons exhibit exaggerated Ca2+ influx through abnormal AMPA receptors.•ADAR2 downregulation initiates above death cascade in ALS motor neurons.
TAR DNA-binding protein (TDP-43) pathology in the motor neurons is the most reliable pathological hallmark of amyotrophic lateral sclerosis (ALS), and motor neurons bearing TDP-43 pathology invariably exhibit failure in RNA editing at the GluA2 glutamine/arginine (Q/R) site due to down-regulation of adenosine deaminase acting on RNA 2 (ADAR2). Conditional ADAR2 knockout (AR2) mice display ALS-like phenotype, including progressive motor dysfunction due to loss of motor neurons. Motor neurons devoid of ADAR2 express Q/R site-unedited GluA2, and AMPA receptors with unedited GluA2 in their subunit assembly are abnormally permeable to Ca2+, which results in progressive neuronal death. Moreover, analysis of AR2 mice has demonstrated that exaggerated Ca2+ influx through the abnormal AMPA receptors overactivates calpain, a Ca2+-dependent protease, that cleaves TDP-43 into aggregation-prone fragments, which serve as seeds for TDP-43 pathology. Activated calpain also disrupts nucleo-cytoplasmic transport and gene expression by cleaving molecules involved in nucleocytoplasmic transport, including nucleoporins. These lines of evidence prompted us to develop molecular targeting therapy for ALS by normalization of disrupted intracellular environment due to ADAR2 down-regulation. In this review, we have summarized the work from our group on the cell death cascade in sporadic ALS and discussed a potential therapeutic strategy for ALS.