Giant ankyrin-G (gAnkG) coordinates assembly of axon initial segments (AISs), which are sites of action potential generation located in proximal axons of most vertebrate neurons. Here, we identify a mechanism required for normal neural development in humans that ensures ordered recruitment of gAnkG and β4-spectrin to the AIS. We identified 3 human neurodevelopmental missense mutations located in the neurospecific domain of gAnkG that prevent recruitment of β4-spectrin, resulting in a lower density and more elongated pattern for gAnkG and its partners than in the mature AIS. We found that these mutations inhibit transition of gAnkG from a closed configuration with close apposition of Nand C-terminal domains to an extended state that is required for binding and recruitment of β4-spectrin, and normally occurs early in development of the AIS. We further found that the neurospecific domain is highly phosphorylated in mouse brain, and that phosphorylation at 2 sites (S1982 and S2619) is required for the conformational change and for recruitment of β4-spectrin. Together, these findings resolve a discrete intermediate stage in formation of the AIS that is regulated through phosphorylation of the neurospecific domain of gAnkG.
|Original language||English (US)|
|Number of pages||10|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - Sep 24 2019|
Bibliographical noteFunding Information:
ACKNOWLEDGMENTS. We thank E. Robinson and J. Hostettler for technical assistance, J. Cheong for data analysis, and Dr. Erik Soderblom and Dr. Greg Waitt at Duke University School of Medicine Proteomics and Metabolomics Shared Resource for providing the MS/MS service. This work was supported by the Howard Hughes Medical Institute and a George Barth Geller endowed professorship (V.B.), and National Institutes of Health grants R21MH115155 (V.B.) and F31NS096848 (K.K.W.-C.).
© 2019 National Academy of Sciences. All rights reserved.
- Axon initial segment
- Giant ankyrin-G
- Neurodevelopmental mutation
- β-4 spectrin