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bioRxiv · 10.1101/2025.11.17.688911

Structure and mechanism of microtubule stabilization and motor regulation by MAP9

Cetin, B.·Taheri, A.·Golcuk, M.·Monroy, B. Y.·Fernandes, J.·Ori-McKenney, K. M.·Gur, M.·Nogales, E.·Yildiz, A.
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Abstract

Microtubule-associated proteins (MAPs) regulate the organization of microtubules and control intracellular transport, but their individual contributions to microtubule dynamics and motor regulation remain poorly understood. Here, we identify MAP9 as a critical factor that stabilizes microtubules and facilitates neuronal morphogenesis. MAP9 knockdown abolishes the outgrowth of neurites, a phenotype not observed through the loss of other neuronal MAPs. Cryo-electron microscopy revealed that, unlike other MAPs that bind along protofilaments, MAP9 binds around the microtubule as a long alpha helix using five consecutive repeats. This unique binding mode enables MAP9 to staple adjacent protofilaments, thereby preventing microtubule depolymerization. We also showed that MAP9 selectively permits kinesin-3 and dynein motility while hindering kinesin-1 through interactions with a divergent loop-8 of the kinesin motor domain. Our results establish MAP9 as a key MAP required for neuronal growth and uncover how it differentially regulates intracellular transport driven by kinesin motors.

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Cetin, B., Taheri, A., Golcuk, M., Monroy, B. Y., Fernandes, J., Ori-McKenney, K. M., Gur, M., Nogales, E., Yildiz, A.. 2025-11-17. Structure and mechanism of microtubule stabilization and motor regulation by MAP9. https://doi.org/10.1101/2025.11.17.688911

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