Selective cleavage of nucleolar autoantigen B23 by granzyme B in differentiated vascular smooth muscle cells: insights into the association of specific autoantibodies with distinct disease phenotypes.

Abstract

OBJECTIVE:

To investigate the association of specific autoantibodies with distinct disease phenotypes. The association of autoantibodies to nucleophosmin/B23 with pulmonary hypertension in scleroderma, and the susceptibility of autoantigens to cleavage by granzyme B (GB), provided a focus for these studies.

METHODS:

Intact cells were subjected to cytotoxic lymphocyte granule-induced death, and the susceptibility of autoantigens to cleavage by GB was addressed by immunoblotting and/or by a novel immunofluorescence assay.

RESULTS:

B23 was cleaved efficiently by GB in vitro, but was highly resistant to cleavage by GB during cytotoxic lymphocyte granule-mediated death of many intact cell types. In contrast, this molecule was highly susceptible to GB-mediated proteolysis exclusively in differentiated vascular smooth muscle cells. Topoisomerase I and several other GB substrates did not show this striking change in cleavage susceptibility in different cell types.

CONCLUSION:

These data demonstrate that the cleavage of B23 by GB in intact cells is dependent upon both cell type and phenotype. The susceptibility of this autoantigen (which is associated with a distinct pulmonary vascular phenotype in scleroderma) to GB-mediated proteolysis selectively in vascular smooth muscle cells suggests that the GB-cleavable conformation of autoantigens may occur selectively in the target tissue, and may play a role in shaping the phenotype-specific autoimmune response.

• Authors: Danielle B Ulanet, Nicholas A Flavahan, Livia Casciola-Rosen, Antony Rosen
• Journal: Arthritis and rheumatism (Arthritis Rheum) Vol. 50 Issue 1 Pg. 233-41 (Jan 2004) ISSN: 0004-3591 [Print] United States
• PMID: 14730621 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Autoantigens
• NPM1 protein, human
• Nuclear Proteins
• Nucleophosmin
• GZMB protein, human
• Granzymes
• Serine Endopeptidases
• DNA Topoisomerases, Type I

Topics

• Autoantigens (genetics, immunology, metabolism)
• Cell Death
• Cell Differentiation
• Cell Nucleolus (immunology)
• Cytoplasmic Granules (immunology)
• DNA Topoisomerases, Type I (metabolism)
• Granzymes
• HeLa Cells
• Humans
• K562 Cells
• Muscle, Smooth, Vascular (cytology, immunology)
• Mutagenesis, Site-Directed
• Nuclear Proteins (genetics, immunology, metabolism)
• Nucleophosmin
• Phenotype
• Serine Endopeptidases (metabolism, pharmacology)
• T-Lymphocytes, Cytotoxic (metabolism)