Profound downregulation of the RNA editing enzyme ADAR2 in ALS spinal motor neurons

• Published in: Neurobiology of disease Vol. 45; no. 3; pp. 1121 - 1128
• Main Authors: Hideyama, Takuto, Yamashita, Takenari, Aizawa, Hitoshi, Tsuji, Shoji, Kakita, Akiyoshi, Takahashi, Hitoshi, Kwak, Shin
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.03.2012; Elsevier
• Subjects: ADAR2 (adenosine deaminase acting on RNA 2); Adenosine Deaminase - genetics; Adenosine Deaminase - metabolism; Adult; Aged; Aged, 80 and over; ALS (amyotrophic lateral sclerosis); AMPA; Amyotrophic Lateral Sclerosis - pathology; Analysis of Variance; Animals; Bulbar Palsy, Progressive - pathology; Case-Control Studies; Down-Regulation - physiology; Female; GluA2; Humans; Male; Middle Aged; Motor Neurons - enzymology; Neurology; Neuronal death; Receptors, AMPA - genetics; Receptors, AMPA - metabolism; RNA editing; RNA-Binding Proteins - genetics; RNA-Binding Proteins - metabolism; Spinal Cord - pathology; Young Adult; CYFIP2; RNA editing; AMPA; ALS (amyotrophic lateral sclerosis); AH; ALS; ADAR2; BLCAP; Q/R; RT-PCR; PH; Neuronal death; GluA2; MSA; ADAR2 (adenosine deaminase acting on RNA 2); PBP; bladder cancer associated protein; posterior horn; glutamine/arginine; amyotrophic lateral sclerosis; AMPA receptor subunit 2; anterior horn; progressive bulbar palsy; L-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid; multiple system atrophy; reverse transcription polymerase chain reaction; cytoplasmic fragile X mental retardation protein interacting protein 2; adenosine deaminase acting on RNA 2
• ISSN: 0969-9961; 1095-953X; 1095-953X
• DOI: 10.1016/j.nbd.2011.12.033

Amyotrophic lateral sclerosis (ALS) is the most common adult-onset fatal motor neuron disease. In spinal motor neurons of patients with sporadic ALS, normal RNA editing of GluA2, a subunit of the L-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor, is inefficient. Adenosine deaminase acting on RNA 2 (ADAR2) specifically mediates RNA editing at the glutamine/arginine (Q/R) site of GluA2 and motor neurons expressing Q/R site-unedited GluA2 undergo slow death in conditional ADAR2 knockout mice. Therefore, investigation into whether inefficient ADAR2-mediated GluA2 Q/R site-editing occurs universally in motor neurons of patients with ALS would provide insight into the pathogenesis of ALS. We analyzed the extents of GluA2 Q/R site-editing in an individual laser-captured motor neuron of 29 ALS patients compared with those of normal and disease control subjects. In addition, we analyzed the enzymatic activity of three members of the ADAR family (ADAR1, ADAR2 and ADAR3) in ALS motor neurons expressing unedited GluA2 mRNA and those expressing only edited GluA2 mRNA. Q/R site-unedited GluA2 mRNA was expressed in a significant proportion of motor neurons from all of the ALS cases examined. Conversely, motor neurons of the normal and disease control subjects expressed only edited GluA2 mRNA. ADAR2, but not ADAR1 or ADAR3, was significantly downregulated in all the motor neurons of ALS patients, more extensively in those expressing Q/R site-unedited GluA2 mRNA than those expressing only Q/R site-edited GluA2 mRNA. These results indicate that ADAR2 downregulation is a profound pathological change relevant to death of motor neurons in ALS. ► Inefficient GluA2 RNA editing is a cause of death of motor neurons. ► The RNA editing enzyme ADAR2 specifically catalyzes the GluA2 RNA editing. ► Motor neurons expressed unedited GluA2 in all the ALS cases examined. ► ADAR2 expression was reduced universally in ALS motor neurons. ► ADAR2 downregulation began preclinically in sporadic ALS.