Profound downregulation of the RNA editing enzyme ADAR2 in ALS spinal motor neurons.
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.
CREST, Japan Science and Technology Agency, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
Takuto
T
Hideyama
Takenari
T
Yamashita
Hitoshi
H
Aizawa
Shoji
S
Tsuji
Akiyoshi
A
Kakita
Hitoshi
H
Takahashi
Shin
S
Kwak
D000243:Adenosine Deaminase / Q000235:genetics / Q000378:metabolism*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000690:Amyotrophic Lateral Sclerosis / Q000473:pathology*; D000704:Analysis of Variance; D000818:Animals; D010244:Bulbar Palsy, Progressive / Q000473:pathology; D016022:Case-Control Studies; D015536:Down-Regulation / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009046:Motor Neurons / Q000201:enzymology*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018091:Receptors, AMPA / Q000235:genetics / Q000378:metabolism; D013116:Spinal Cord / Q000473:pathology*; D055815:Young Adult
D016601:RNA-Binding Proteins; D018091:Receptors, AMPA; C567955:ADARB1 protein, human; D000243:Adenosine Deaminase; C104722:glutamate receptor ionotropic, AMPA 2