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Binding of nucleosomes to a cell surface receptor: redistribution and endocytosis in the presence of lupus antibodies.

Abstract：

:In the present study, we sought evidence for a surface nucleosome receptor in the fibroblastic cell line CV-1, and questioned whether anti-double-stranded (ds) DNA and/or anti-histone autoantibodies could recognize and influence the fate of cell surface-bound nucleosomes. 125I-labeled mononucleosomes were shown to bind to the cell layer in a specific, concentration-dependent and a saturable manner. Scatchard analysis revealed the presence of two binding sites: a high-affinity site with a Kd of approximately 7nM and a low-affinity site (Kd approximately 400 nM) with a high capacity of 9 x 10(7) sites. Visualization of bound mononucleosomes by fluorescence revealed staining on both the cell surface and the extracellular matrix (ECM). Purified mononucleosome-derived ds DNA (180-200 bp) was found to complete for binding of 125I-mononucleosomes on the low-affinity site, to stain exclusively the ECM in immunofluorescence, and to precipitate three specific proteins of 43, 180 and 240 kDa from 125-I-labeled cell lysates. Nucleosomes were found to precipitate not only the 180-kDa ds DNA-reactive component, but also a unique protein of 50 kDa, suggesting that this protein is a cell surface receptor for nucleosomes on these fibroblasts. Once bound on the cell surface, mononucleosomes were recognized and secondarily complexed by lupus anti-ds DNA or anti-histone antibodies (i.e. anti-nucleosome antibodies), thus forming immune complexes in situ. The presence of these complexing auto-antibodies was found dramatically to enhance the kinetics of mononucleosome internalization. Following the internalization of the nucleosome-anti-nucleosome complexes by immunofluorescence, we observed the formation of vesicles at the edge of the cells by 5-10 min which moved toward the perinuclear region by 20-30 min. By means of double-fluorescence labeling and proteolytic treatment, these fluorescent vesicles were shown to be in the cytoplasm, suggesting true endocytosis of nucleosome-anti-nucleosome immune complexes. As shown by confocal microscopy, at no stage of this endocytic process was there any indication that coated pits or coated vesicles participated. Co-distribution of the endocytic vesicles with regions rich in actin filaments and inhibition of endocytosis of nucleosome-anti-nucleosome complexes by disruption of the microfilament network with cytochalasin D suggest a mechanism mediated by the cytoskeleton. Taken together, our data provide evidence for the presence of a surface nucleosome receptor. We also show that anti-ds DNA and anti-histone antibodies can form nucleosome-anti-nucleosome immune complexes in situ at the cell surface, and thus dramatically enhance the kinetics of nucleosome endocytosis.

journal_name

Eur J Immunol

journal_title

European journal of immunology

authors

Koutouzov S,Cabrespines A,Amoura Z,Chabre H,Lotton C,Bach JF

doi

10.1002/eji.1830260230

subject

Has Abstract

pub_date

1996-02-01 00:00:00

pages

472-86

issue

eissn

0014-2980

issn

1521-4141

journal_volume

pub_type

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Binding of nucleosomes to a cell surface receptor: redistribution and endocytosis in the presence of lupus antibodies.