Sun Ying, Ramakrishnan Skandha, Lai Xiaona, Wu Ronghua, Dong Zhangji, Qiang Liang, Liu Mei
Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu 226001, China.
Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, United States of America.
Biochim Biophys Acta Mol Cell Res. 2025 Feb;1872(2):119890. doi: 10.1016/j.bbamcr.2024.119890. Epub 2024 Dec 15.
Microtubule-severing enzymes such as spastin, katanin, and fidgetin, characterized by their AAA ATPase domains, are pivotal in modulating microtubule dynamics and behavior across various cellular processes. While spastin and katanin are recognized for their predominant and robust severing of stable microtubules, thereby enhancing microtubule turnover, fidgetin exhibits comparatively weaker severing activity and selectively targets labile microtubules. The interplay among these enzymes and their mutual regulatory mechanisms remains inadequately understood. In this study, we elucidate the functional interaction between spastin and fidgetin, focusing on their roles in microtubule severing and neurite outgrowth. Our findings demonstrate that fidgetin serves as a negative regulator of spastin's severing activity. Co-expression assays revealed that fidgetin significantly attenuates spastin's severing efficiency, as confirmed by fluorescence-based microtubule polymerization assays and quantitative imaging of microtubule dynamics. Co-immunoprecipitation and Förster Resonance Energy Transfer (FRET) analyses further established a direct interaction between fidgetin and spastin, suggesting that fidgetin modulates spastin's activity through direct binding, possibly contributing to forming the hetero-hexmeric ring for their severing activities. Functionally, spastin overexpression in neuronal cells enhances neurite outgrowth, an effect that is suppressed upon co-expression with fidgetin, indicating that fidgetin counterbalances spastin's activity to regulate neurite extension. Therefore, this study uncovers a previously unrecognized mechanism by which fidgetin modulates spastin's function, providing critical insights into the intricate regulation of microtubule severing. These findings have significant implications for therapeutic strategies targeting microtubule-severing activities, particularly in neurodevelopmental and neurodegenerative disorders where microtubule dysregulation is a hallmark.
微管切断酶，如痉挛蛋白、katanin和fidgetin，以其AAA ATP酶结构域为特征，在调节各种细胞过程中的微管动力学和行为方面起着关键作用。虽然痉挛蛋白和katanin因其对稳定微管的主要且强大的切断作用而被认可，从而增强了微管周转，但fidgetin表现出相对较弱的切断活性，并选择性地靶向不稳定微管。这些酶之间的相互作用及其相互调节机制仍未得到充分理解。在本研究中，我们阐明了痉挛蛋白和fidgetin之间的功能相互作用，重点关注它们在微管切断和神经突生长中的作用。我们的研究结果表明，fidgetin作为痉挛蛋白切断活性的负调节因子。共表达分析表明，fidgetin显著降低了痉挛蛋白的切断效率，基于荧光的微管聚合分析和微管动力学的定量成像证实了这一点。免疫共沉淀和荧光共振能量转移（FRET）分析进一步证实了fidgetin和痉挛蛋白之间的直接相互作用，表明fidgetin通过直接结合调节痉挛蛋白的活性，这可能有助于形成它们切断活性所需的异源六聚体环。在功能上，神经元细胞中痉挛蛋白的过表达增强了神经突生长，而与fidgetin共表达时这种效应受到抑制，这表明fidgetin抵消了痉挛蛋白的活性以调节神经突延伸。因此，本研究揭示了一种以前未被认识的fidgetin调节痉挛蛋白功能的机制，为微管切断的复杂调节提供了关键见解。这些发现对针对微管切断活性的治疗策略具有重要意义，特别是在微管失调是标志的神经发育和神经退行性疾病中。
