The carbohydrate-binding domain of Lafora disease protein targets Lafora polyglucosan bodies

• Published in: Biochemical and biophysical research communications 2004-01, Vol.313 (4), p.1101-1109
• Main Authors: Ganesh, Subramaniam, Tsurutani, Naomi, Suzuki, Toshimitsu, Hoshii, Yoshinobu, Ishihara, Tokuhiro, Delgado-Escueta, Antonio V, Yamakawa, Kazuhiro
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Binding Sites; Carbohydrate binding; Carbohydrate Metabolism; Carpora amylacea; Chickens; Conserved Sequence; Dual-Specificity Phosphatases; Epilepsy; Glucans - metabolism; Humans; In Vitro Techniques; Inclusion Bodies - metabolism; Inclusion Bodies - pathology; Lafora Disease - genetics; Lafora Disease - metabolism; Lafora Disease - pathology; Mice; Mice, Knockout; Molecular Sequence Data; Mutation; Neurodegeneration; Phosphatase; Polyglucosan inclusion; Protein Structure, Tertiary; Protein Tyrosine Phosphatases - chemistry; Protein Tyrosine Phosphatases - genetics; Protein Tyrosine Phosphatases - metabolism; Protein Tyrosine Phosphatases, Non-Receptor; Recombinant Fusion Proteins - chemistry; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; Sequence Homology, Amino Acid
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2003.12.043

Lafora’s disease (LD) is an autosomal recessive and fatal form of epilepsy with onset in late childhood or adolescence. One of the characteristic features of LD pathology is the presence of periodic acid–Schiff (PAS) positive Lafora inclusion bodies. Lafora bodies are present primarily in neurons, but they have also been found in other organs. Histochemical and biochemical studies have indicated that Lafora bodies are composed mainly of polysaccharides. The LD gene, EPM2A, encodes a 331 amino acid long protein named laforin that contains an N-terminal carbohydrate-binding domain (CBD) and a C-terminal dual-specificity phosphatase domain (DSPD). Here we demonstrate that the CBD of laforin targets the protein to Lafora inclusion bodies and this property could be evolutionarily conserved. We also tested in vitro the effects of five LD missense mutations on laforin’s affinity to Lafora body. While the missense mutant W32G failed to bind to purified Lafora body, four other mutants (S25P, E28L, F88L, and R108C) did not show any effect on the binding affinity. Based on these observations we propose the existence of a laforin-mediated glycogen metabolic pathway regulating the disposal of pathogenic polyglucosan inclusions. This is the first report demonstrating a direct association between the LD gene product and the disease-defining storage product, the Lafora bodies.