Abstract
Giant axonal neuropathy (GAN) is a devastating sensory and motor neuropathy caused by mutations in the GAN gene, which encodes the ubiquitously expressed protein gigaxonin1,2,3,4,5. Cytopathological features of GAN include axonal degeneration, with accumulation and aggregation of cytoskeletal components6,7. Little is currently known about the molecular mechanisms underlying this recessive disorder. Here we show that gigaxonin controls protein degradation, and is essential for neuronal function and survival. We present evidence that gigaxonin binds to the ubiquitin-activating enzyme E1 through its amino-terminal BTB domain, while the carboxy-terminal kelch repeat domain interacts directly with the light chain (LC) of microtubule-associated protein 1B (MAP1B)8. Overexpression of gigaxonin leads to enhanced degradation of MAP1B-LC, which can be antagonized by proteasome inhibitors. Ablation of gigaxonin causes a substantial accumulation of MAP1B-LC in GAN-null neurons. Moreover, we show that overexpression of MAP1B in wild-type cortical neurons leads to cell death characteristic of GAN-null neurons, whereas reducing MAP1B levels significantly improves the survival rate of null neurons. Our results identify gigaxonin as a ubiquitin scaffolding protein that controls MAP1B-LC degradation, and provide insight into the molecular mechanisms underlying human neurodegenerative disorders.
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References
Bomont, P. et al. The gene encoding gigaxonin, a new member of the cytoskeletal BTB/kelch repeat family, is mutated in giant axonal neuropathy. Nature Genet. 26, 370–374 (2000)
Bomont, P. et al. Identification of seven novel mutations in the GAN gene. Hum. Mutat. 21, 446 (2003)
Tazir, M. et al. Genetic heterogeneity in giant axonal neuropathy: an Algerian family not linked to chromosome 16q24.1. Neuromuscul. Disord. 12, 849–852 (2002)
Bruno, C. et al. Clinical and molecular findings in patients with giant axonal neuropathy (GAN). Neurology 62, 13–16 (2004)
Timmerman, V., De Jonghe, P. & Van Broeckhoven, C. Of giant axons and curly hair. Nature Genet. 26, 254–255 (2000)
Tandan, R. et al. Childhood giant axonal neuropathy. Case report and review of the literature. J. Neurol. Sci. 82, 205–228 (1987)
Lampl, Y. et al. Giant axonal neuropathy with predominant central nervous system manifestations. Dev. Med. Child Neurol. 34, 164–169 (1992)
Ding, J. et al. Microtubule-associated protein 1B: a neuronal binding partner for gigaxonin. J. Cell Biol. 158, 427–433 (2002)
Pintard, L. et al. The BTB protein MEL-26 is a substrate-specific adaptor of the CUL-3 ubiquitin-ligase. Nature 425, 311–316 (2003)
van den Heuvel, S. Protein degradation: CUL-3 and BTB–partners in proteolysis. Curr. Biol. 14, R59–R61 (2004)
Geyer, R., Wee, S., Anderson, S., Yates, J. & Wolf, D. A. BTB/POZ domain proteins are putative substrate adaptors for cullin 3 ubiquitin ligases. Mol. Cell 12, 783–790 (2003)
Furukawa, M., He, Y. J., Borchers, C. & Xiong, Y. Targeting of protein ubiquitination by BTB–Cullin 3–Roc1 ubiquitin ligases. Nature Cell Biol. 5, 1001–1007 (2003)
Ehlers, M. D. Deconstructing the axon: Wallerian degeneration and the ubiquitin–proteasome system. Trends Neurosci. 27, 3–6 (2004)
Zhai, Q. et al. Involvement of the ubiquitin-proteasome system in the early stages of wallerian degeneration. Neuron 39, 217–225 (2003)
Watts, R. J., Hoopfer, E. D. & Luo, L. Axon pruning during Drosophila metamorphosis: evidence for local degeneration and requirement of the ubiquitin-proteasome system. Neuron 38, 871–885 (2003)
Mei, X., Sweatt, A. J. & Hammarback, J. A. Regulation of microtubule-associated protein 1B (MAP1B) subunit composition. J. Neurosci. Res. 62, 56–64 (2000)
Edelmann, W. et al. Neuronal abnormalities in microtubule-associated protein 1B mutant mice. Proc. Natl Acad. Sci. USA 93, 1270–1275 (1996)
Tucker, R. P. & Matus, A. I. Developmental regulation of two microtubule-associated proteins (MAP2 and MAP5) in the embryonic avian retina. Development 101, 535–546 (1987)
Lu, R. et al. The fragile X protein controls microtubule-associated protein 1B translation and microtubule stability in brain neuron development. Proc. Natl Acad. Sci. USA 101, 15201–15206 (2004)
Lopez, L. A. & Sheetz, M. P. Steric inhibition of cytoplasmic dynein and kinesin motility by MAP2. Cell Motil. Cytoskeleton 24, 1–16 (1993)
Paschal, B. M., Obar, R. A. & Vallee, R. B. Interaction of brain cytoplasmic dynein and MAP2 with a common sequence at the C terminus of tubulin. Nature 342, 569–572 (1989)
Hagiwara, H., Yorifuji, H., Sato-Yoshitake, R. & Hirokawa, N. Competition between motor molecules (kinesin and cytoplasmic dynein) and fibrous microtubule-associated proteins in binding to microtubules. J. Biol. Chem. 269, 3581–3589 (1994)
von Massow, A., Mandelkow, E. M. & Mandelkow, E. Interaction between kinesin, microtubules, and microtubule-associated protein 2. Cell Motil. Cytoskeleton 14, 562–571 (1989)
Vicario-Abejón, C. in Current Protocols in Neuroscience (eds Crawley, J. N. et al.) Ch. 3, 2.1–2.13 (John Wiley & Sons, Somerset, New Jersey, 2004)
Togel, M., Wiche, G. & Propst, F. Novel features of the light chain of microtubule-associated protein MAP1B: microtubule stabilization, self interaction, actin filament binding, and regulation by the heavy chain. J. Cell Biol. 143, 695–707 (1998)
Acknowledgements
We thank F. Propst and L. Binder for their gifts of rabbit polyclonal MAP1B-LC (ref. 25) and mouse monoclonal MAP1B-HC antibodies, respectively. The pZ-OFF EGFP vector was a gift from C. Garner and P. Zamorano. We also thank C. Wu for helpful discussions. This work was supported by a Muscular Dystrophy Association Research Grant and NIH grants to Y.Y. Author Contributions E.A. and J.D. contributed equally to this work. E.A. conceived and carried out most of the experiments, with assistance from S.P., J.C. and V.Y. J.D. conceived and carried out yeast two-hybrid screening, performed quantitative PCR and some biochemical assays, and conducted statistical and pathological analyses. W.W. and J.D. established and maintained cortical neuron cultures. All authors discussed the results. Y.Y. designed and directed the project. E.A. and Y.Y. co-wrote the paper.
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Supplementary information
Supplementary Figure 1
Gigaxonin overexpression downregulates endogenous MAP1B-LC levels. Flag-tagged gigaxonin or GFP was transfected into PC12 cells in six independent experiments and harvested at the indicated time points to test endogenous MAP1B-LC downregulation. (PDF 52 kb)
Supplementary Figure 2
MAP1B-LC expression in gigaxonin WT and KO littermates. Six sets of data were compiled from brain extracts to test endogenous MAP1B-LC levels. (PDF 37 kb)
Supplementary Figure 3
Neuronal death in WT and KO cultured cortical neurons. Coverslips from four sets of cultured WT and KO neurons at from four different pairs of matched littermates were stained for Dapi and α-tubulin. Each field was scored for positive Dapi staining and the existence of a robust tubulin network, and neurons with both were scored as positive. (PDF 218 kb)
Supplementary Figure 4
MAP1B-LC siRNA partially rescues neuronal death in gigaxonin null neurons. Cultured WT and KO cortical neurons from two sets of matched littermates were transfected with MAP1B or scrambled siRNA, harvested, and stained with rabbit anti-γ-tubulin and mouse anti-GFP. Neuronal size and morphology was recorded and neurons scored as having long or short neurites, or dying. (PDF 55 kb)
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Allen, E., Ding, J., Wang, W. et al. Gigaxonin-controlled degradation of MAP1B light chain is critical to neuronal survival. Nature 438, 224–228 (2005). https://doi.org/10.1038/nature04256
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DOI: https://doi.org/10.1038/nature04256
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