Regulation of purine metabolism connects KCTD13 to a metabolic disorder with autistic features

Summary Genetic variation of the 16p11.2 deletion locus containing the KCTD13 gene and of CUL3 are linked with autism. This genetic connection suggested that substrates of a CUL3-KCTD13 ubiquitin ligase may be involved in disease pathogenesis. Comparison of Kctd13 mutant (Kctd13−/−) and wild-type neuronal ubiquitylomes identified adenylosuccinate synthetase (ADSS), an enzyme that catalyzes the first step in AMP synthesis, as a KCTD13 ligase substrate. In Kctd13−/− neurons there was increased levels of succinyl-adenosine (S-Ado), a metabolite downstream of ADSS. Notably, S-Ado levels are elevated in adenylosuccinate lyase deficiency, a metabolic disorder with autism and epilepsy phenotypes. The increased S-Ado levels in Kctd13−/− neurons were decreased by treatment with an ADSS inhibitor. Lastly, functional analysis of human KCTD13 variants suggests that KCTD13 variation may alter ubiquitination of ADSS. These data suggest that succinyl-AMP metabolites accumulate in Kctd13−/− neurons and this observation may have implications for our understanding of 16p11.2 deletion syndrome.