title: Lamina-associated polypeptide 2beta (LAP2beta) is contained in a protein complex together with A- and B-type lamins.
abstract: Lamina-associated polypeptide 2beta (LAP2beta) of vertebrates is an integral membrane protein of the inner nuclear membrane that is generated by alternative splicing from the LAP2 gene. In the majority of Xenopus somatic cells including cultured kidney epithelial cells (A6 cells) there is only one major LAP2 isoform expressed that has the highest similarities with the mammalian LAP2beta whereas isoforms corresponding in size to the mammalian LAP2gamma and alpha are not detectable. We selected A6 cells and A6 cells stably expressing GFP fusion proteins of Xenopus LAP2beta (XLAP2Pbeta) as a model system to study interactions between LAP2beta and lamins. In vitro binding experiments with GST-XLAP2beta fusion proteins and immunoprecipitations with antibodies to GFP revealed that XLAP2beta is part of a complex that contains A- and B-type lamins. For the targeting to the nuclear envelope and the in vivo formation of this complex, GFP fusion proteins were sufficient comprising only the carboxyterminal 135 amino acids of XLAP2beta or the comparable region of zebrafish LAP2beta. A highly conserved 36 amino acids long sequence is located in this region of LAP2beta that is part of the lamina-binding domain previously identified in rat LAP2beta. GFP-LAP2beta fusion proteins of Xenopus, zebrafish, and rat that contained this sequence do compete with endogenous LAP2 in transfected cells for the same binding sites in the lamina. Our data indicate that the lamina-binding site of LAP2beta has been highly conserved during vertebrate evolution and suggests that this region of LAP2beta mediates the interactions between polymers of A- and B-type lamins.
authors.affiliation: Division of Electron Microscopy, Biocenter of the University of Würzburg, Würzburg/Germany.
authors.forename: Carmen
authors.initials: C
authors.lastname: Lang
authors.forename: Georg
authors.initials: G
authors.lastname: Krohne
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000918:Antibody Specificity; D001665:Binding Sites / Q000235:genetics; D019556:COS Cells; D002457:Cell Extracts / Q000737:chemistry; D002460:Cell Line; D017124:Conserved Sequence / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D049452:Green Fluorescent Proteins; D034904:Lamin Type A / Q000235:genetics / Q000378:metabolism*; D034921:Lamin Type B / Q000235:genetics / Q000378:metabolism*; D008164:Luminescent Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D011233:Precipitin Tests; D011485:Protein Binding; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014981:Xenopus
chemical_list: D002457:Cell Extracts; D004268:DNA-Binding Proteins; D034904:Lamin Type A; D034921:Lamin Type B; D008164:Luminescent Proteins; D046911:Macromolecular Substances; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; C093413:lamina-associated polypeptide 2; D049452:Green Fluorescent Proteins; D005982:Glutathione Transferase