An Amyotrophic Lateral Sclerosis-Associated Mutant of C21ORF2 Is Stabilized by NEK1-Mediated Hyperphosphorylation and the Inability to Bind FBXO3
Yasuaki Watanabe,
Tadashi Nakagawa,
Tetsuya Akiyama,
Makiko Nakagawa,
Naoki Suzuki,
Hitoshi Warita,
Masashi Aoki,
Keiko Nakayama
Affiliations
Yasuaki Watanabe
Department of Neurology, Graduate School of Medicine, Tohoku University, Sendai, Miyagi 980-8575, Japan; Division of Cell Proliferation, ART, Graduate School of Medicine, Tohoku University, Sendai, Miyagi 980-8575, Japan
Tadashi Nakagawa
Division of Cell Proliferation, ART, Graduate School of Medicine, Tohoku University, Sendai, Miyagi 980-8575, Japan
Tetsuya Akiyama
Department of Neurology, Graduate School of Medicine, Tohoku University, Sendai, Miyagi 980-8575, Japan
Makiko Nakagawa
Division of Cell Proliferation, ART, Graduate School of Medicine, Tohoku University, Sendai, Miyagi 980-8575, Japan
Naoki Suzuki
Department of Neurology, Graduate School of Medicine, Tohoku University, Sendai, Miyagi 980-8575, Japan
Hitoshi Warita
Department of Neurology, Graduate School of Medicine, Tohoku University, Sendai, Miyagi 980-8575, Japan
Masashi Aoki
Department of Neurology, Graduate School of Medicine, Tohoku University, Sendai, Miyagi 980-8575, Japan
Keiko Nakayama
Division of Cell Proliferation, ART, Graduate School of Medicine, Tohoku University, Sendai, Miyagi 980-8575, Japan; Corresponding author
Summary: C21ORF2 and NEK1 have been identified as amyotrophic lateral sclerosis (ALS)-associated genes. Both genes are also mutated in certain ciliopathies, suggesting that they might contribute to the same signaling pathways. Here we show that FBXO3, the substrate receptor of an SCF ubiquitin ligase complex, binds and ubiquitylates C21ORF2, thereby targeting it for proteasomal degradation. C21ORF2 stabilizes the kinase NEK1, with the result that loss of FBXO3 stabilizes not only C21ORF2 but also NEK1. Conversely, NEK1-mediated phosphorylation stabilizes C21ORF2 by attenuating its interaction with FBXO3. We found that the ALS-associated V58L mutant of C21ORF2 is more susceptible to phosphorylation by NEK1, with the result that it is not ubiquitylated by FBXO3 and therefore accumulates together with NEK1. Expression of C21ORF2(V58L) in motor neurons induced from mouse embryonic stem cells impaired neurite outgrowth. We suggest that inhibition of NEK1 activity is a potential therapeutic approach to ALS associated with C21ORF2 mutation.
