title: The inner nuclear membrane protein LAP1 forms a native complex with B-type lamins and partitions with spindle-associated mitotic vesicles.
abstract: We have examined the in situ organization and nearest neighbours of the 'lamina-associated polypeptide-1' (LAP1), a type II membrane protein and a major constituent of the mammalian nuclear envelope. We show here that, during interphase, LAP1 forms multimeric assemblies which are suspended in the inner nuclear membrane and are specifically associated with B-type lamins. The LAP1-lamin B complex is distinct from analogous complexes formed by the 'lamina-associated polypeptide-2' (LAP2), another inner nuclear membrane protein, and includes a protein kinase. Upon nuclear envelope breakdown, LAP1 partitions with mitotic vesicles which carry nuclear lamin B. The LAP1 vesicles can be distinguished from fragments of the nuclear envelope containing LAP2 and exhibit a striking co-alignment with spindle microtubules. These observations suggest that the inner nuclear membrane comprises discrete territories which accommodate specific integral membrane proteins and are differentially disassembled during mitosis.
authors.affiliation: Department of Basic Sciences, The University of Crete School of Medicine, Heraklion, Greece.
authors.forename: C
authors.initials: C
authors.lastname: Maison
authors.forename: A
authors.initials: A
authors.lastname: Pyrpasopoulou
authors.forename: P A
authors.initials: PA
authors.lastname: Theodoropoulos
authors.forename: S D
authors.initials: SD
authors.lastname: Georgatos
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D002460:Cell Line; D004268:DNA-Binding Proteins; D004591:Electrophoresis, Polyacrylamide Gel; D007150:Immunohistochemistry; D007399:Interphase; D034921:Lamin Type B; D034882:Lamins; D008565:Membrane Proteins / Q000276:immunology / Q000378:metabolism*; D008938:Mitosis; D008969:Molecular Sequence Data; D009685:Nuclear Envelope / Q000737:chemistry*; D009687:Nuclear Proteins / Q000276:immunology / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry; D010748:Phosphopeptides / Q000378:metabolism; D011494:Protein Kinases / Q000737:chemistry; D051381:Rats; D017421:Sequence Analysis; D008941:Spindle Apparatus / Q000737:chemistry / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; D004268:DNA-Binding Proteins; D034921:Lamin Type B; D034882:Lamins; D008565:Membrane Proteins; D009687:Nuclear Proteins; D010446:Peptide Fragments; D010748:Phosphopeptides; C093127:TOR1AIP1 protein, rat; C093413:lamina-associated polypeptide 2; D011494:Protein Kinases