title: Identification of a novel human LAP1 isoform that is regulated by protein phosphorylation.
abstract: Lamina associated polypeptide 1 (LAP1) is an integral protein of the inner nuclear membrane that is ubiquitously expressed. LAP1 binds to lamins and chromatin, probably contributing to the maintenance of the nuclear envelope architecture. Moreover, LAP1 also interacts with torsinA and emerin, proteins involved in DYT1 dystonia and X-linked Emery-Dreifuss muscular dystrophy disorder, respectively. Given its relevance to human pathological conditions, it is important to better understand the functional diversity of LAP1 proteins. In rat, the LAP1 gene (TOR1AIP1) undergoes alternative splicing to originate three LAP1 isoforms (LAP1A, B and C). However, it remains unclear if the same occurs with the human TOR1AIP1 gene, since only the LAP1B isoform had thus far been identified in human cells. In silico analysis suggested that, across different species, potential new LAP1 isoforms could be generated by alternative splicing. Using shRNA to induce LAP1 knockdown and HPLC-mass spectrometry analysis the presence of two isoforms in human cells was described and validated: LAP1B and LAP1C; the latter is putatively N-terminal truncated. LAP1B and LAP1C expression profiles appear to be dependent on the specific tissues analyzed and in cultured cells LAP1C was the major isoform detected. Moreover, LAP1B and LAP1C expression increased during neuronal maturation, suggesting that LAP1 is relevant in this process. Both isoforms were found to be post-translationally modified by phosphorylation and methionine oxidation and two LAP1B/LAP1C residues were shown to be dephosphorylated by PP1. This study permitted the identification of the novel human LAP1C isoform and partially unraveled the molecular basis of LAP1 regulation.
authors.affiliation: Laboratório de Neurociências e Sinalização, Centro de Biologia Celular, SACS, Universidade de Aveiro, Aveiro, Portugal.
authors.forename: Mariana
authors.initials: M
authors.lastname: Santos
authors.affiliation: Laboratório de Neurociências e Sinalização, Centro de Biologia Celular, SACS, Universidade de Aveiro, Aveiro, Portugal.
authors.forename: Sara C
authors.initials: SC
authors.lastname: Domingues
authors.affiliation: Laboratório de Neurociências e Sinalização, Centro de Biologia Celular, SACS, Universidade de Aveiro, Aveiro, Portugal.
authors.forename: Patrícia
authors.initials: P
authors.lastname: Costa
authors.affiliation: Department of Functional Proteomics, Medical Proteome Center, Ruhr University Bochum, Bochum, Germany.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Muller
authors.affiliation: Department of Functional Proteomics, Medical Proteome Center, Ruhr University Bochum, Bochum, Germany.
authors.forename: Sara
authors.initials: S
authors.lastname: Galozzi
authors.affiliation: Department of Functional Proteomics, Medical Proteome Center, Ruhr University Bochum, Bochum, Germany.
authors.forename: Katrin
authors.initials: K
authors.lastname: Marcus
authors.affiliation: Laboratório de Neurociências e Sinalização, Centro de Biologia Celular, SACS, Universidade de Aveiro, Aveiro, Portugal.
authors.forename: Edgar F
authors.initials: EF
authors.lastname: da Cruz e Silva
authors.affiliation: Laboratório de Neurociências e Sinalização, Centro de Biologia Celular, SACS, Universidade de Aveiro, Aveiro, Portugal.
authors.forename: Odete A
authors.initials: OA
authors.lastname: da Cruz e Silva
authors.affiliation: Laboratório de Neurociências e Sinalização, Centro de Biologia Celular, SACS, Universidade de Aveiro, Aveiro, Portugal.
authors.forename: Sandra
authors.initials: S
authors.lastname: Rebelo
mesh_terms: D017398:Alternative Splicing / Q000235:genetics; D000818:Animals; D004422:Dystonia Musculorum Deformans / Q000235:genetics* / Q000473:pathology; D005786:Gene Expression Regulation; D023281:Genomics; D050883:HSC70 Heat-Shock Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000302:isolation & purification; D006801:Humans; D008715:Methionine / Q000235:genetics; D020389:Muscular Dystrophy, Emery-Dreifuss / Q000235:genetics* / Q000473:pathology; D010766:Phosphorylation / Q000235:genetics; D020033:Protein Isoforms / Q000235:genetics* / Q000302:isolation & purification; D011499:Protein Processing, Post-Translational / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D016415:Sequence Alignment
chemical_list: D050883:HSC70 Heat-Shock Proteins; C494371:HSPA8 protein, human; D020033:Protein Isoforms; D012333:RNA, Messenger; D008715:Methionine