title: Laforin, a dual specificity phosphatase involved in Lafora disease, is present mainly as monomeric form with full phosphatase activity.
abstract: Lafora Disease (LD) is a fatal neurodegenerative epileptic disorder that presents as a neurological deterioration with the accumulation of insoluble, intracellular, hyperphosphorylated carbohydrates called Lafora bodies (LBs). LD is caused by mutations in either the gene encoding laforin or malin. Laforin contains a dual specificity phosphatase domain and a carbohydrate-binding module, and is a member of the recently described family of glucan phosphatases. In the current study, we investigated the functional and physiological relevance of laforin dimerization. We purified recombinant human laforin and subjected the monomer and dimer fractions to denaturing gel electrophoresis, mass spectrometry, phosphatase assays, protein-protein interaction assays, and glucan binding assays. Our results demonstrate that laforin prevalently exists as a monomer with a small dimer fraction both in vitro and in vivo. Of mechanistic importance, laforin monomer and dimer possess equal phosphatase activity, and they both associate with malin and bind glucans to a similar extent. However, we found differences between the two states' ability to interact simultaneously with malin and carbohydrates. Furthermore, we tested other members of the glucan phosphatase family. Cumulatively, our data suggest that laforin monomer is the dominant form of the protein and that it contains phosphatase activity.
authors: Department of Molecular and Cellular Biochemistry and Center for Structural Biology, College of Medicine, University of Kentucky, Lexington, Kentucky, United States of America.
authors: Vikas V
authors: VV
authors: Dukhande
authors: Devin M
authors: DM
authors: Rogers
authors: Carlos
authors: C
authors: Romá-Mateo
authors: Jordi
authors: J
authors: Donderis
authors: Alberto
authors: A
authors: Marina
authors: Adam O
authors: AO
authors: Taylor
authors: Pascual
authors: P
authors: Sanz
authors: Matthew S
authors: MS
authors: Gentry
mesh_terms: D002241:Carbohydrates; D002352:Carrier Proteins / Q000378:metabolism; D054637:Dual-Specificity Phosphatases / Q000032:analysis* / Q000378:metabolism; D006801:Humans; D020192:Lafora Disease / Q000201:enzymology*; D011485:Protein Binding; D055503:Protein Multimerization; D054558:Protein Tyrosine Phosphatases, Non-Receptor / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases
chemical_list: D002241:Carbohydrates; D002352:Carrier Proteins; C478960:NHLRC1 protein, human; D044767:Ubiquitin-Protein Ligases; D054637:Dual-Specificity Phosphatases; D054558:Protein Tyrosine Phosphatases, Non-Receptor; C114990:EPM2A protein, human