EPM2A-interacting protein 1 interacts with laforin, the product of the EPM2A gene, which is mutated in an autosomal recessive form of adolescent progressive myoclonus epilepsy [].
Proteins containing this domain include vertebrate dual specificity protein phosphatase Laforin and plant starch excess4 (SEX4). Laforin (encoded by the EPM2A gene) is a dual-specificity phosphatase that dephosphorylates complex carbohydrates. Mutations in the EPM2A gene cause Lafora disease (LD), a fatal autosomal recessive neurodegenerative disorder characterised by the presence of progressive neurological deterioration, myoclonus, and epilepsy []. Pathologically, LD is characterised by distinctive polyglucosans, which are formations of abnormal glycogen []. Laforin prevents LD by at least two mechanisms: by preventing hyperphosphorylation of glycogen by dephosphorylating it, allowing proper glycogen formation, and by promoting the ubiquitination of proteins involved in glycogen metabolism via its interaction with malin. Laforin contains an N-terminal CBM20 (carbohydrate-binding module, family 20) domain and a C-terminal catalytic dual specificity phosphatase (DSP) domain [].Plant SEX4 (also known as DSP4) regulates starch metabolism by selectively dephosphorylating glucose moieties within starch glucan chains. It contains an N-terminal catalytic DSP domain and a C-terminal Early (E) set domain [].
Laforin (encoded by the EPM2A gene) is a protein phosphatase and one of the two proteins (the other one is malin, a E3-ubiquitin ligase) that is defective in Lafora disease (LD), a progressive form of inherited epilepsy associated with widespread neurodegeneration and the formation of polyglucosan bodies in the neurons []. Laforin and malin form a functional complex, in which laforin could recognize and recruit putative substrates to be ubiquitinated by malin for degradation. The Laforin-malin complex regulates glycogen synthesis through targeting R5/PTG (Protein Targeting to Glycogen) for inactivation, most probably by proteolysis. Moreover, the Laforin-Malin complex is also involved in different pathways, such as intracellular protein degradation, oxidative stress, and the endoplasmic reticulum unfolded protein response []. It contains a carbohydrate binding module (CBM) at the N terminus and a dual specificity phosphatase domain (DSP) at the C terminus. The structure of Laforin has been revealed [].
Laforin, encoded by the EPM2A gene, is a dual-specificity phosphatase that dephosphorylates complex carbohydrates. Mutations in the gene encoding laforin result in Lafora disease, a fatal autosomal recessive neurodegenerative disorder characterised by the presence of intracellular deposits of insoluble, abnormally branched, glycogen-like polymers, known as Lafora bodies, in neurons, muscle, liver, and other tissues. The molecular basis for the formation of these Lafora bodies is unknown. Laforin is one of the only phosphatases that contains a carbohydrate-binding module [].Laforin is a protein containing a dual-specificity protein phosphatase catalytic domain in the C terminus and a carbohydrate-binding domain in the N terminus [].The CBM20 domain is found in a large number of starch degrading enzymes including alpha-amylase, beta-amylase, glucoamylase, and CGTase (cyclodextrin glucanotransferase). CBM20 is also present in proteins that have a regulatory role in starch metabolism in plants (e.g. alpha-amylase) or glycogen metabolism in mammals (e.g. laforin). CBM20 folds as an antiparallel β-barrel structure with two starch binding sites. These two sites are thought to differ functionally with site 1 acting as the initial starch recognition site and site 2 involved in the specific recognition of appropriate regions of starch [].
