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Mechanism suppressing glycogen synthesis in neurons and its demise in progressive myoclonus epilepsy


Glycogen synthesis is normally absent in neurons. However, inclusion bodies resembling abnormal glycogen accumulate in several neurological diseases, particularly in progressive myoclonus epilepsy or Lafora disease. We show here that mouse neurons have the enzymatic machinery for synthesizing glycogen, but that it is suppressed by retention of muscle glycogen synthase (MGS) in the phosphorylated, inactive state. This suppression was further ensured by a complex of laforin and malin, which are the two proteins whose mutations cause Lafora disease. The laforin-malin complex caused proteasome-dependent degradation both of the adaptor protein targeting to glycogen, PTG, which brings protein phosphatase 1 to MGS for activation, and of MGS itself. Enforced expression of PTG led to glycogen deposition in neurons and caused apoptosis. Therefore, the malin-laforin complex ensures a blockade of neuronal glycogen synthesis even under intense glycogenic conditions. Here we explain the formation of polyglucosan inclusions in Lafora disease by demonstrating a crucial role for laforin and malin in glycogen synthesis.

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Figure 1: Neurons express MGS, but do not accumulate glycogen.
Figure 2: Effects of increased intracellular levels of G6P or overexpression of MGS.
Figure 3: PTG expression activates neuronal MGS and results in glycogen accumulation.
Figure 4: Accumulation of glycogen promotes apoptosis in primary cultured neurons.
Figure 5: Blockade of glycogen synthesis by laforin and malin.
Figure 6: The significance of the interaction between laforin and malin in glycogen metabolism.


  1. 1

    Brown, A.M. Brain glycogen re-awakened. J. Neurochem. 89, 537–552 (2004).

    CAS  PubMed  Google Scholar 

  2. 2

    Cavanagh, J.B. Corpora-amylacea and the family of polyglucosan diseases. Brain Res. Brain Res. Rev. 29, 265–295 (1999).

    CAS  PubMed  Google Scholar 

  3. 3

    Berkovic, S.F., Andermann, F., Carpenter, S. & Wolfe, L.S. Progressive myoclonus epilepsies: specific causes and diagnosis. N. Engl. J. Med. 315, 296–305 (1986).

    CAS  PubMed  Google Scholar 

  4. 4

    Lafora, G.R. Über das corkommen amyloider körperchen im innern der ganglienzellen; zugliech ein zum studium der amyloiden substanz im nervensystem. Virchows Arch. Pathol. Anat. 205, 294–303 (1911).

    Google Scholar 

  5. 5

    Lafora, G.R. & Glueck, B. Beitrag zur histogpathologie der myoklonischen epilepsie. Z. Gesamte Neurol. Psychiatr. 6, 1–14 (1911).

    Google Scholar 

  6. 6

    Collins, G.H., Cowden, R.R. & Nevis, A.H. Myoclonus epilepsy with Lafora bodies. An ultrastructural and cytochemical study. Arch. Pathol. 86, 239–254 (1968).

    CAS  PubMed  Google Scholar 

  7. 7

    Sakai, M., Austin, J., Witmer, F. & Trueb, L. Studies in myoclonus epilepsy (Lafora body form). II. Polyglucosans in the systemic deposits of myoclonus epilepsy and in corpora amylacea. Neurology 20, 160–176 (1970).

    CAS  PubMed  Google Scholar 

  8. 8

    Acharya, J.N., Satishchandra, P. & Shankar, S.K. Familial progressive myoclonus epilepsy: clinical and electrophysiologic observations. Epilepsia 36, 429–434 (1995).

    CAS  PubMed  Google Scholar 

  9. 9

    Berkovic, S.F., Cochius, J., Andermann, E. & Andermann, F. Progressive myoclonus epilepsies: clinical and genetic aspects. Epilepsia 34 (Suppl 3): S19–S30 (1993).

    PubMed  Google Scholar 

  10. 10

    Kobayashi, K., Iyoda, K., Ohtsuka, Y., Ohtahara, S. & Yamada, M. Longitudinal clinicoelectrophysiologic study of a case of Lafora disease proven by skin biopsy. Epilepsia 31, 194–201 (1990).

    CAS  PubMed  Google Scholar 

  11. 11

    Minassian, B.A. Lafora's disease: towards a clinical, pathologic and molecular synthesis. Pediatr. Neurol. 25, 21–29 (2001).

    CAS  PubMed  Google Scholar 

  12. 12

    Shahwan, A., Farrell, M. & Delanty, N. Progressive myoclonic epilepsies: a review of genetic and therapeutic aspects. Lancet Neurol. 4, 239–248 (2005).

    CAS  PubMed  Google Scholar 

  13. 13

    Van Heycop Ten Ham, M.W. Lafora disease, a form of progressive myoclonues epilepsy. Handb. Clin. Neurol. 15, 382–422 (1974).

    Google Scholar 

  14. 14

    Minassian, B.A. et al. Mutations in a gene encoding a novel protein tyrosine phosphatase cause progressive myoclonus epilepsy. Nat. Genet. 20, 171–174 (1998).

    CAS  PubMed  Google Scholar 

  15. 15

    Minassian, B.A. et al. Mutation spectrum and predicted function of laforin in Lafora's progressive myoclonus epilepsy. Neurology 55, 341–346 (2000).

    CAS  PubMed  Google Scholar 

  16. 16

    Serratosa, J.M. et al. A novel protein tyrosine phosphatase gene is mutated in progressive myoclonus epilepsy of the Lafora type (EPM2). Hum. Mol. Genet. 8, 345–352 (1999).

    CAS  PubMed  Google Scholar 

  17. 17

    Wang, J., Stuckey, J.A., Wishart, M.J. & Dixon, J.E. A unique carbohydrate binding domain targets the lafora disease phosphatase to glycogen. J. Biol. Chem. 277, 2377–2380 (2002).

    CAS  PubMed  Google Scholar 

  18. 18

    Ganesh, S., Puri, R., Singh, S., Mittal, S. & Dubey, D. Recent advances in the molecular basis of Lafora's progressive myoclonus epilepsy. J. Hum. Genet. 51, 1–8 (2006).

    CAS  PubMed  Google Scholar 

  19. 19

    Chan, E.M. et al. Mutations in NHLRC1 cause progressive myoclonus epilepsy. Nat. Genet. 35, 125–127 (2003).

    CAS  PubMed  Google Scholar 

  20. 20

    Gentry, M.S., Worby, C.A. & Dixon, J.E. Insights into Lafora disease: malin is an E3 ubiquitin ligase that ubiquitinates and promotes the degradation of laforin. Proc. Natl. Acad. Sci. USA 102, 8501–8506 (2005).

    CAS  PubMed  Google Scholar 

  21. 21

    Ferrer, J.C. et al. Control of glycogen deposition. FEBS Lett. 546, 127–132 (2003).

    CAS  PubMed  Google Scholar 

  22. 22

    Gomis, R.R., Cid, E., Garcia-Rocha, M., Ferrer, J.C. & Guinovart, J.J. Liver glycogen synthase but not the muscle isoform differentiates between glucose 6-phosphate produced by glucokinase or hexokinase. J. Biol. Chem. 277, 23246–23252 (2002).

    CAS  PubMed  Google Scholar 

  23. 23

    Skurat, A.V., Dietrich, A.D. & Roach, P.J. Glycogen synthase sensitivity to insulin and glucose-6-phosphate is mediated by both NH2- and COOH-terminal phosphorylation sites. Diabetes 49, 1096–1100 (2000).

    CAS  PubMed  Google Scholar 

  24. 24

    Ferrer, J.C., Baque, S. & Guinovart, J.J. Muscle glycogen synthase translocates from the cell nucleus to the cystosol in response to glucose. FEBS Lett. 415, 249–252 (1997).

    CAS  PubMed  Google Scholar 

  25. 25

    Cid, E., Cifuentes, D., Baque, S., Ferrer, J.C. & Guinovart, J.J. Determinants of the nucleocytoplasmic shuttling of muscle glycogen synthase. FEBS J. 272, 3197–3213 (2005).

    CAS  PubMed  Google Scholar 

  26. 26

    Skurat, A.V., Wang, Y. & Roach, P.J. Rabbit skeletal muscle glycogen synthase expressed in COS cells. Identification of regulatory phosphorylation sites. J. Biol. Chem. 269, 25534–25542 (1994).

    CAS  PubMed  Google Scholar 

  27. 27

    MacAulay, K. et al. Use of lithium and SB-415286 to explore the role of glycogen synthase kinase-3 in the regulation of glucose transport and glycogen synthase. Eur. J. Biochem. 270, 3829–3838 (2003).

    CAS  PubMed  Google Scholar 

  28. 28

    Printen, J.A., Brady, M.J. & Saltiel, A.R. PTG, a protein phosphatase 1–binding protein with a role in glycogen metabolism. Science 275, 1475–1478 (1997).

    CAS  PubMed  Google Scholar 

  29. 29

    Fong, N.M. et al. Identification of binding sites on protein targeting to glycogen for enzymes of glycogen metabolism. J. Biol. Chem. 275, 35034–35039 (2000).

    CAS  PubMed  Google Scholar 

  30. 30

    Berman, H.K., O'Doherty, R.M., Anderson, P. & Newgard, C.B. Overexpression of protein targeting to glycogen (PTG) in rat hepatocytes causes profound activation of glycogen synthesis independent of normal hormone- and substrate-mediated regulatory mechanisms. J. Biol. Chem. 273, 26421–26425 (1998).

    CAS  PubMed  Google Scholar 

  31. 31

    Fernandez-Sanchez, M.E. et al. Laforin, the dual-phosphatase responsible for Lafora disease, interacts with R5 (PTG), a regulatory subunit of protein phosphatase 1 that enhances glycogen accumulation. Hum. Mol. Genet. 12, 3161–3171 (2003).

    CAS  PubMed  Google Scholar 

  32. 32

    Allaman, I., Pellerin, L. & Magistretti, P.J. Protein targeting to glycogen mRNA expression is stimulated by noradrenaline in mouse cortical astrocytes. Glia 30, 382–391 (2000).

    CAS  PubMed  Google Scholar 

  33. 33

    Schlamowitz, M. On the nature of rabbit liver glycogen. II. Iodine absorption spectrum. J. Biol. Chem. 190, 519–527 (1951).

    CAS  PubMed  Google Scholar 

  34. 34

    Lee, D.H. & Goldberg, A.L. Proteasome inhibitors: valuable new tools for cell biologists. Trends Cell Biol. 8, 397–403 (1998).

    CAS  PubMed  Google Scholar 

  35. 35

    Villar-Palasi, C. & Guinovart, J.J. The role of glucose-6-phosphate in the control of glycogen synthase. FASEB J. 11, 544–558 (1997).

    CAS  PubMed  Google Scholar 

  36. 36

    Simo, S. et al. Reelin induces the detachment of postnatal subventricular zone cells and the expression of the Egr-1 through Erk1/2 activation. Cereb. Cortex 17, 294–303 (2007).

    PubMed  Google Scholar 

  37. 37

    Seoane, J. et al. Glucose-6-phosphate produced by glucokinase, but not hexokinase I, promotes the activation of hepatic glycogen synthase. J. Biol. Chem. 271, 23756–23760 (1996).

    CAS  PubMed  Google Scholar 

  38. 38

    Becker, T.C. et al. Use of recombinant adenovirus for metabolic engineering of mammalian cells. Methods Cell Biol. 43 (Pt A): 161–189 (1994).

    CAS  PubMed  Google Scholar 

  39. 39

    McGrory, W.J., Bautista, D.S. & Graham, F.L. A simple technique for the rescue of early region I mutations into infectious human adenovirus type 5. Virology 163, 614–617 (1988).

    CAS  PubMed  Google Scholar 

  40. 40

    Hojlund, K. et al. Increased phosphorylation of skeletal muscle glycogen synthase at NH2-terminal sites during physiological hyperinsulinemia in type 2 diabetes. Diabetes 52, 1393–1402 (2003).

    CAS  PubMed  Google Scholar 

  41. 41

    Baba, O. [Production of monoclonal antibody that recognizes glycogen and its application for immunohistochemistry.]. Kokubyo Gakkai Zasshi. 60, 264–287 (1993).

    CAS  PubMed  Google Scholar 

  42. 42

    Chan, T.M. & Exton, J.H. A rapid method for the determination of glycogen content and radioactivity in small quantities of tissue or isolated hepatocytes. Anal. Biochem. 71, 96–105 (1976).

    CAS  PubMed  Google Scholar 

  43. 43

    Lang, G. & Michal, G. d-glucose-6-phosphate and d-Fructose-6-phosphate. in Methods of Enzymatic Analysis (ed. Bergmeyer, H. U.) 1238–1242 (Academic Press, New York, 1974).

    Google Scholar 

  44. 44

    Bradford, M.M. A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Anal. Biochem. 72, 248–254 (1976).

    CAS  PubMed  Google Scholar 

  45. 45

    Thomas, J.A., Schlender, K.K. & Larner, J. A rapid filter paper assay for UDPglucose-glycogen glucosyltransferase, including an improved biosynthesis of UDP-14C-glucose. Anal. Biochem. 25, 486–499 (1968).

    CAS  PubMed  Google Scholar 

  46. 46

    Guinovart, J.J. et al. Glycogen synthase: a new activity ratio assay expressing a high sensitivity to the phosphorylation state. FEBS Lett. 106, 284–288 (1979).

    CAS  PubMed  Google Scholar 

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We thank J. Massagué for providing a critical review of the manuscript, P. Sanz and J.M. Serratosa for their advice, A. Adrover and E. Veza for their technical support, and T. Yates for correcting the manuscript. We also thank R.R. Gomis for the AdCMV-PTG virus, O. Baba for the monoclonal antibody to glycogen and D.G. Hardy for the gift of the PGSser7/10 antibody. This study was supported by grants from the Fundació La Caixa, Fundació La Marató de TV3, Fundación Marcelino Botín, the Spanish Ministry of Education and Science (SAF2005-00913; BFU2005-02253) and the Instituto de Salud Carlos III (CIBER-ER; RD06/0015/0030).

Author information




D.V. conducted most of the experiments, data analysis and interpretation. S.R. generated the AdCMV-laf, AdCMV-malin and AdCMV-malinD146N recombinant adenoviruses. D.C. carried out the RT-PCR experiments. L.P. contributed to the primary neuron cultures and the apoptosis assays. J.V. carried out the analysis of glycogen branching. S.R., D.C. and J.V. also contributed to other experiments. B.G.-F., O.C.-G., E.F.-S. and I.M.-F. generated the monoclonal laforin antibody, pCINeo-Laforin vector and pcDNA3-Malin-HA vector. J.D. supervised several experiments and the data analysis, and contributed to writing the manuscript. M.G.-R. supervised the western blot and immunofluorescence experiments. E.S. contributed with his knowledge of the nervous system. S.R.d.C. and J.J.G. planned and supervised the project, co-wrote the manuscript and contributed to every aspect of the project.

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Correspondence to Santiago Rodríguez de Córdoba or Joan J Guinovart.

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Vilchez, D., Ros, S., Cifuentes, D. et al. Mechanism suppressing glycogen synthesis in neurons and its demise in progressive myoclonus epilepsy. Nat Neurosci 10, 1407–1413 (2007).

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