The MAN antigens are non-lamin constituents of the nuclear lamina in vertebrate cells

Abstract

The characterization of the human antiserum designated MAN has led to the identification of a subset of non-lamin proteins that are exclusively located at the nuclear periphery in all vertebrate cell types examined, from human to fish. Immunoreactive protein species were shown to comprise three major polypeptides of Mr 78000, 58000 and 40000. These antigens co-partitioned with the nuclear lamina during in situ isolation of nuclear matrices from lamin A/C-positive and -negative mammalian cells. Using double immunofluorescence, the spatial relationship of MAN antigens to type-A and type-B lamins was further examined throughout the cell cycle of lamin A/C-positive mammalian cells. In interphase HeLa and 3T3 cells, MAN antigens colocalized with both types of lamins at the periphery of the nucleus, but were absent from intranuclear foci of lamin B. As HeLa cells proceeded into mitosis, MAN antigens were seen to segregate from lamins A/C and coredistribute with lamin B. Lamins A/C disassembled during late prophase/early prometaphase and reassociated with chromatin in telophase/cytokinesis. In contrast, MAN antigens and lamin B dispersed late during prometaphase and reassembled on chromosomes in anaphase. Altogether, our data suggest that MAN antigens may play key functions in the maintenance of the structural integrity of the nuclear compartment in vertebrate cells.

MAN1, an Inner Nuclear Membrane Protein That Shares the LEM Domain with Lamina-associated Polypeptide 2 and Emerin

“…The size-fractionated cDNA was ligated into bacteriophage gt22, which was digested with NotI and SalI, and packaged using the Life Technologies, Inc. Lambda Packaging System (Life Technologies). Standard methods (35) were used for screening the expression library with human serum (1:20,000 dilution) that contained the MAN autoantibodies (32). This screening led to the isolation of one clone.…”

“…Some patients with rheumatic and autoimmune liver diseases have autoantibodies that recognize nuclear envelope antigens, and these antibodies can potentially be useful tools in the identification of novel nuclear membrane proteins (30,31). Recently, autoantibodies were described in a patient with an ill-defined collagen vascular disease that recognize three polypeptides called "MAN antigens" that are localized exclusively to the nuclear envelope and cofractionate biochemically with nuclear lamins (32). The three MAN antigens have apparent molecular masses of approximately 80, 58, and 40 kDa.…”

Man1, an inner nuclear membrane protein, regulates left–right axis formation by controlling nodal signaling in a node‐independent manner

“…Several INM proteins share a conserved structural motif of approximately 40 amino acid residues, termed the LEM domain, which was first identified in lamina-associated polypeptide (LAP)␤, emerin, and MAN1 (Lin et al, 2000). MAN1, was identified as one of the antigens recognized by autoantibodies from a patient with a collagen vascular disease (Paulin-Levasseur et al, 1996;Lin et al, 2000). In addition to the LEM domain at the N-terminus, MAN1 has two putative transmembrane domains followed by an evolutionally conserved C-terminal domain.…”

Inner nuclear membrane and signal transduction

“…The ''MAN antigens'' were originally identified using serum (''MAN antiserum'') from a subject with a collagen vascular disease that labeled the nuclear envelope when used in indirect immunofluorescence microscopy [Paulin-Levasseur et al, 1996]. The antibodies in this serum recognized three predominant antigens that co-isolated with nuclear lamins in cell fractionation experiments.…”