Microtubule-Associated Protein 1B: A Neuronal Binding Partner for Gigaxonin

• Published in: The Journal of cell biology Vol. 158; no. 3; pp. 427 - 433
• Main Authors: Ding, Jianqing, Liu, Jia-Jia, Kowal, Anthony S., Nardine, Timothy, Bhattacharya, Priyanka, Lee, Arthur, Yang, Yanmin
• Format: Journal Article
• Language: English
• Published: United States Rockefeller University Press 05.08.2002; The Rockefeller University Press
• Subjects: Animals; Antibodies; Binding, Competitive - physiology; Brain; Brain - metabolism; Brain - ultrastructure; Cells, Cultured; Cellular biology; Colchicine - pharmacology; COS cells; Cytoskeletal Proteins - genetics; Cytoskeletal Proteins - metabolism; Cytoskeletal Proteins - ultrastructure; Cytoskeleton; Fluorescent Antibody Technique; Giant axonal neuropathy; Heredodegenerative Disorders, Nervous System - genetics; Heredodegenerative Disorders, Nervous System - metabolism; Heredodegenerative Disorders, Nervous System - physiopathology; Mice; Microscopy, Electron; Microtubule associated proteins; Microtubule-Associated Proteins - genetics; Microtubule-Associated Proteins - metabolism; Microtubule-Associated Proteins - ultrastructure; Microtubules; Microtubules - genetics; Microtubules - metabolism; Microtubules - ultrastructure; Mutation - physiology; Nervous System - metabolism; Nervous System - physiopathology; Nervous System - ultrastructure; Neurodegenerative diseases; Neurological disorders; Neurons; Neurons - metabolism; Neurons - ultrastructure; Protein Binding - physiology; Protein Structure, Tertiary - physiology; Proteins; Transfection; Yeasts
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.200202055

Giant axonal neuropathy (GAN), an autosomal recessive disorder caused by mutations in GAN, is characterized cytopathologically by cytoskeletal abnormality. Based on its sequence, gigaxonin contains an NH2-terminal BTB domain followed by six kelch repeats, which are believed to be important for protein-protein interactions (Adams, J., R. Kelso, and L. Cooley. 2000. Trends Cell Biol. 10:17-24.). Here, we report the identification of a neuronal binding partner of gigaxonin. Results obtained from yeast two-hybrid screening, cotransfections, and coimmunoprecipitations demonstrate that gigaxonin binds directly to microtubule-associated protein (MAP)1B light chain (LC; MAP1B-LC), a protein involved in maintaining the integrity of cytoskeletal structures and promoting neuronal stability. Studies using double immunofluorescent microscopy and ultrastructural analysis revealed physiological colocalization of gigaxonin with MAP1B in neurons. Furthermore, in transfected cells the specific interaction of gigaxonin with MAP1B is shown to enhance the microtubule stability required for axonal transport over long distance. At least two different mutations identified in GAN patients (Bomont, P., L. Cavalier, F. Blondeau, C. Ben Hamida, S. Belal, M. Tazir, E. Demir, H. Topaloglu, R. Korinthenberg, B. Tuysuz, et al. 2000. Nat. Genet. 26:370-374.) lead to loss of gigaxonin-MAP1B-LC interaction. The devastating axonal degeneration and neuronal death found in GAN patients point to the importance of gigaxonin for neuronal survival. Our findings may provide important insights into the pathogenesis of neurodegenerative disorders related to cytoskeletal abnormalities.