Signaling by the cytokine transforming growth factor β (TGF-β) has been implicated in a multitude of biological functions; however, TGF-β signaling, particularly in the CNS, remains largely unexplored. ANK3 variants (encoding ankyrin-G) are associated with bipolar disorder, intellectual disability, and autism spectrum disorder, while mutations in USP9X, which encodes a deubiquitinase, are associated with X-linked intellectual disability and autism in humans. Here, we show that TGF-β signaling promotes Usp9X phosphorylation, which enhances its interaction with ankyrin-G and stabilizes ankyrin-G in spines, leading to spine enlargement. Using in situ proximity ligation combined with structured illumination superresolution microscopy, we characterize the postsynaptic spatial organization of phosphorylation-dependent regulation of Usp9X/ankyrin-G interactions in dendrites and its quantitative relationship with spine morphology and number. These data reveal a cytokine-mediated mechanism regulating protein stability in spines and suggest a role for deubiquitination and TGF-β signaling in neurodevelopmental disorder pathogenesis and treatment.
Keywords: TGF-β; Usp9X; ankyrin-G; proximity ligation assay; structured illumination microscopy.
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