title: Secretion-Positive LGI1 Mutations Linked to Lateral Temporal Epilepsy Impair Binding to ADAM22 and ADAM23 Receptors.
abstract: Autosomal dominant lateral temporal epilepsy (ADTLE) is a focal epilepsy syndrome caused by mutations in the LGI1 gene, which encodes a secreted protein. Most ADLTE-causing mutations inhibit LGI1 protein secretion, and only a few secretion-positive missense mutations have been reported. Here we describe the effects of four disease-causing nonsynonymous LGI1 mutations, T380A, R407C, S473L, and R474Q, on protein secretion and extracellular interactions. Expression of LGI1 mutant proteins in cultured cells shows that these mutations do not inhibit protein secretion. This finding likely results from the lack of effects of these mutations on LGI1 protein folding, as suggested by 3D protein modelling. In addition, immunofluorescence and co-immunoprecipitation experiments reveal that all four mutations significantly impair interaction of LGI1 with the ADAM22 and ADAM23 receptors on the cell surface. These results support the existence of a second mechanism, alternative to inhibition of protein secretion, by which ADLTE-causing LGI1 mutations exert their loss-of-function effect extracellularly, and suggest that interactions of LGI1 with both ADAM22 and ADAM23 play an important role in the molecular mechanisms leading to ADLTE.
authors.affiliation: CNR-Neuroscience Institute, Section of Padua, Padova, Italy.
authors.forename: Emanuela
authors.initials: E
authors.lastname: Dazzo
authors.affiliation: Department of Woman and Child's Health, University of Padua, Padova, Italy.
authors.forename: Emanuela
authors.identifier: http://orcid.org/0000-0001-8486-8461
authors.initials: E
authors.lastname: Leonardi
authors.affiliation: Department of Biology, University of Padua, Padova, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Belluzzi
authors.affiliation: Department of Biomedical Sciences, University of Padua, Padova, Italy.
authors.forename: Sandro
authors.initials: S
authors.lastname: Malacrida
authors.affiliation: Department of Biology, University of Padua, Padova, Italy.
authors.forename: Libero
authors.initials: L
authors.lastname: Vitiello
authors.affiliation: Department of Biology, University of Padua, Padova, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Greggio
authors.affiliation: CNR-Neuroscience Institute, Section of Padua, Padova, Italy.|Department of Biomedical Sciences, University of Padua, Padova, Italy.
authors.forename: Silvio C E
authors.initials: SC
authors.lastname: Tosatto
authors.affiliation: CNR-Neuroscience Institute, Section of Padua, Padova, Italy.|Department of Biomedical Sciences, University of Padua, Padova, Italy.
authors.forename: Carlo
authors.identifier: http://orcid.org/0000-0002-0634-2218
authors.initials: C
authors.lastname: Nobile
mesh_terms: D051722:ADAM Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D019943:Amino Acid Substitution / Q000235:genetics; D000818:Animals; D019556:COS Cells; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism; D002522:Chlorocebus aethiops; D017034:Epilepsy, Frontal Lobe / Q000235:genetics* / Q000473:pathology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D020125:Mutation, Missense; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D011487:Protein Conformation; D017510:Protein Folding; D060066:Protein Interaction Maps / Q000235:genetics*; D011506:Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D012893:Sleep Wake Disorders / Q000235:genetics* / Q000473:pathology
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; C116499:LGI1 protein, human; D009419:Nerve Tissue Proteins; D011506:Proteins; D051722:ADAM Proteins; C498474:ADAM22 protein, human; C114633:ADAM23 protein, human