Cooperative Interactions between 480 kDa Ankyrin-G and EB Proteins Assemble the Axon Initial Segment.
The axon initial segment (AIS) is required for generating action potentials and maintaining neuronal polarity. Significant progress has been made in deciphering the basic building blocks composing the AIS, but the underlying mechanisms required for AIS formation remains unclear. The scaffolding protein ankyrin-G is the master-organizer of the AIS. Microtubules and their interactors, particularly end-binding proteins (EBs), have emerged as potential key players in AIS formation. Here, we show that the longest isoform of ankyrin-G (480AnkG) selectively associates with EBs via its specific tail domain and that this interaction is crucial for AIS formation and neuronal polarity in cultured rodent hippocampal neurons. EBs are essential for 480AnkG localization and stabilization at the AIS, whereas 480AnkG is required for the specific accumulation of EBs in the proximal axon. Our findings thus provide a conceptual framework for understanding how the cooperative relationship between 480AnkG and EBs induces the assembly of microtubule-AIS structures in the proximal axon.


CONCLUSIONS
Neuronal polarity is crucial for the proper function of neurons. The assembly of the axon initial segment (AIS), which is the hallmark of early neuronal polarization, relies on the longest 480 kDa ankyrin-G isoform. The microtubule cytoskeleton and its interacting proteins were suggested to be early key players in the process of AIS formation. In this study, we show that the crosstalk between 480 kDa ankyrin-G and the microtubule plus-end tracking proteins, EBs, at the proximal axon is decisive for AIS assembly and neuronal polarity. Our work thus provides insight into the functional mechanisms used by 480 kDa ankyrin-G to drive the AIS formation and thereby to establish neuronal polarity.
Sorbonne Universités, UPMC Université Paris 06, INSERM UMR-S 1130, and CNRS UMR 8246, Neuroscience Paris Seine, F-75005, Paris, France, and Cell Biology, Faculty of Science, Utrecht University, Padualaan 8, CH Utrecht 3584, The Netherlands a.freal@uu.nl c.hoogenraad@uu.nl.
Amélie
A
Fréal
Sorbonne Universités, UPMC Université Paris 06, INSERM UMR-S 1130, and CNRS UMR 8246, Neuroscience Paris Seine, F-75005, Paris, France, and.
Coralie
C
Fassier
Sorbonne Universités, UPMC Université Paris 06, INSERM UMR-S 1130, and CNRS UMR 8246, Neuroscience Paris Seine, F-75005, Paris, France, and.
Barbara
B
Le Bras
Sorbonne Universités, UPMC Université Paris 06, INSERM UMR-S 1130, and CNRS UMR 8246, Neuroscience Paris Seine, F-75005, Paris, France, and.
Erika
E
Bullier
Sorbonne Universités, UPMC Université Paris 06, INSERM UMR-S 1130, and CNRS UMR 8246, Neuroscience Paris Seine, F-75005, Paris, France, and.
Stéphanie
S
De Gois
Sorbonne Universités, UPMC Université Paris 06, INSERM UMR-S 1130, and CNRS UMR 8246, Neuroscience Paris Seine, F-75005, Paris, France, and.
Jamilé
J
Hazan
Cell Biology, Faculty of Science, Utrecht University, Padualaan 8, CH Utrecht 3584, The Netherlands a.freal@uu.nl c.hoogenraad@uu.nl.
Casper C
CC
Hoogenraad
Sorbonne Universités, UPMC Université Paris 06, INSERM UMR-S 1130, and CNRS UMR 8246, Neuroscience Paris Seine, F-75005, Paris, France, and.
François
F
Couraud
D000818:Animals; D017487:Ankyrins / Q000378:metabolism*; D001369:Axons / Q000378:metabolism* / Q000648:ultrastructure; D019556:COS Cells; D016764:Cell Polarity / Q000502:physiology; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D005260:Female; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism / Q000648:ultrastructure; D011485:Protein Binding / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley
C094681:Ank3 protein, mouse; D017487:Ankyrins; C584107:EB1 protein, mouse; D008869:Microtubule-Associated Proteins
ankyrin-G; axon initial segment; end-binding protein; microtubule; neuronal polarity