Neurodevelopmental disorder associated mutations in TAOK1 reveal its function as a plasma membrane remodeling kinase

Abstract

Mutations in TAOK1, a serine-threonine kinase encoding gene are strongly associated with both autism spectrum disorder (ASD) and neurodevelopmental delay (NDD). However, molecular function of this evolutionarily conserved kinase and the mechanisms through which TAOK1 mutations lead to neuropathology are unknown. Here, we showed that TAOK1 is highly expressed in neurons within the brain, and has a functional role in remodeling the plasma membrane through direct association with phosphoinositides. We characterized four NDD-associated TAOK1 mutations, and demonstrated that these mutations render TAOK1 catalytically dead. Kinase dead TAOK1 mutants were aberrantly trapped in membrane-bound state, which induced exuberant membrane protrusions. Expression of TAOK1 disease mutants in hippocampal neurons led to abnormal growth of the dendritic arbor. The coiled-coil region C-terminal to the kinase domain are predicted to fold into a triple helix. We showed that this triple helix directly bound phospholipids, and was required for both TAOK1 membrane association and induction of aberrant protrusions. Further, TAOK1 mutants were rescued from their membrane-trapped state by exogenous expression of the isolated kinase domain. Utilizing mass-spectrometry, we identified critical residues in the triple helix phosphorylated by TAOK1 that autoregulated its plasma membrane association. These findings define a previously unknown function of TAOK1 as a unique plasma membrane remodeling kinase, and reveal the underlying mechanisms through which TAOK1 dysfunction leads to neurodevelopmental disorders.