The X-linked intellectual disability gene product and E3 ubiquitin ligase KLHL15 degrades doublecortin proteins to constrain neuronal dendritogenesis

Abstract

Proper brain development and function requires finely controlled mechanisms for protein turnover and disruption of genes involved in proteostasis is a common cause of neurodevelopmental disorders. Kelch-like 15 (KLHL15) is a substrate adaptor for cullin3 (Cul3)-containing E3 ubiquitin ligases and KLHL15 gene mutations were recently described as a cause of severe X-linked intellectual disability. Here, we used a bioinformatics approach to identify a family of neuronal microtubule-associated proteins (MAPs) as KLHL15 substrates, which are themselves critical for early brain development. We biochemically validated doublecortin (DCX), also an X-linked disease gene, and doublecortin-like kinases 1 and 2 (DCLK1/2) as bona fide KLHL15 interactors and mapped KLHL15 interaction regions to their tandem DCX domains. Shared with two previously identified KLHL15 substrates, a FRY tripeptide at the C-terminal edge of the second DCX domain is necessary for KLHL15-mediated ubiquitination of DCX and DCLK1/2 and subsequent proteasomal degradation. Conversely, silencing endogenous KLHL15 markedly stabilizes these DCX domain-containing proteins and prolongs their half-life. Functionally, overexpression of KLHL15 in the presence of wild-type DCX reduces dendritic complexity of cultured hippocampal neurons, whereas neurons expressing FRY-mutant DCX are resistant to KLHL15. Collectively, our findings highlight the critical importance of the E3 ubiquitin ligase adaptor KLHL15 in proteostasis of neuronal MAPs and identify a regulatory network important for development of the mammalian nervous system.

Immunotherapeutic Significance of a Prognostic Alternative Splicing Signature in Bladder Cancer

“…35 Ubiquitin-mediated proteolysis comprises 2 steps: the binding of ubiquitin molecules to protein substrates and the degradation of the polyubiquitin proteins by the 26S proteasome complex, which plays an important role in protein degradation, regulation of the cell cycle, modulation of the immune and inflammatory responses, control of signal transduction pathways, development, and differentiation. [36][37][38] Furthermore, many studies have shown that suppressing the ubiquitin-mediated proteolysis pathway promotes the proliferation and migration of tumor cells. [39][40][41] Thus, AS events in patients with bladder cancer might impact a variety of biological functions via the ubiquitin-mediated proteolysis pathway.…”