Novel (nua) Kinase 1 (NUAK1) encodes a serine-threonine protein kinase, mutations in which are associated with neurodevelopmental disorder. Direct phosphorylation targets of NUAK1 have been elusive hindering mechanistic understanding of its role in brain development. Here, we characterize autism-associated NUAK1 variants and shows their differential impact on catalytic activity and subcellular distribution. Next, we employed a chemical-genetic strategy with engineered ATP analog-sensitive kinase to identify over 30 direct phosphorylation targets of NUAK1. We demonstrate that Pleckstrin Homology and Sec7-domain containing protein 3 (PSD3) is a bona fide phosphorylation target of NUAK1. A guanine exchange factor (GEF) for ARF6 GTPase, PSD3 is phosphorylated by NUAK1 at S476. Expression of phosphodeficient PSD3 leads to aberrant activation of ARF6 and generation of PI(4,5)P2 that accumulates in intracellular vesicles. In neurons, phosphomutant PSD3 leads to enhanced spine maturation in an ARF6 dependent fashion. This study reveals direct neuronal substrates of an autism risk gene NUAK1, and delineates a mechanism by which PSD3 phosphorylation regulates ARF6 activation and spine maturation.
Adaptation to free-living drives loss of beneficial endosymbiosis through metabolic trade-offs
Symbioses are widespread (1) and underpin the function of diverse ecosystems (2-6), but their evolutionary stability is challenging to explain (7,8). Fitness trade-offs between con-trasting