Neddylation E1 Obligatory Subunit Nae1 Is Critical to Neuromuscular Junction Development and Maintenance.

Rapsyn is a scaffold protein that is thought to anchor acetylcholine receptors at the neuromuscular junction (NMJ). We showed that it may be an E3 ligase that regulates NMJ development by neddylation. To obtain genetical evidence, we mutated Nae1 (APP-BP1), an obligatory subunit of the neddylation E1 enzyme specifically in muscle cells. The mutation decreased the stability of acetylcholine receptor (AChR)α, reduced AChR clustering, and impaired NMJ development in Pax7-Cre;Nae1f/f mice (of either sex) and caused neonatal lethality. Moreover, while NMJs were normal in heterozygous mutant mice of Nae1 or rapsyn C366A (a knock-in mutation that eliminates E3 ligase activity), double heterozygous mutant mice (of either sex) displayed NMJ deficits, indicative of a genetic interaction between Nae1 and rapsyn. These results provide genetic evidence for a role of neddylation in NMJ formation and support the notion that rapsyn serves as a neddylation E3 ligase in NMJ formation.