Intracellular trafficking and surface expression of SS-A (Ro), SS-B (La), poly(ADP-ribose) polymerase and alpha-fodrin autoantigens during apoptosis in human salivary gland cells induced by tumour necrosis factor-alpha.
Autoantibodies directed against nucleic acid and protein complexes present in cell nuclei characterize autoimmune diseases and are employed in diagnosis. The mechanisms by which these autoantigens escape immunological tolerance are largely unknown, but a number of recent observations suggest that modified self-protein generated during apoptosis my play an important part in the development of autoimmunity. To investigate the possibility that autoantibodies in patients with Sjögren's syndrome are induced by apoptosis and presented on the surface of the cell, the internal distribution of autoantigens in apoptotic human salivary gland cells was studied in vitro. Salivary gland cells were treated with tumour necrosis factor-alpha, an apoptosis inducer. At increasing times after induction, cells were homogenized and cytoplasmic, cell surface membrane and nuclear compartments were fractionated using a sucrose density-gradient system. Autoantigens alpha-fodrin, SS-A (Ro), SS-B (La), and the enzyme poly(ADP-ribose) polymerase, were detected by conventional immunofluorescence and confirmed by Western immunoblotting. At increasing times after apoptosis, nuclear proteins SS-A (Ro) and SS-B (La), but not poly(ADP-ribose) polymerase were relocated from the cell nucleus to the cell surface membrane. Fodrin, a cytoplasmic protein, was also translocated to the cell membrane after cleavage of alpha-fodrin. These results show that autoantigens fodrin, SS-A (Ro) and SS-B (La) in human salivary gland cells undergo a striking redistribution during apoptosis and relocate to the cell membrane of apoptotic cells. The appearance of autoantigens on the surface of induced cells could form the basis of a mechanism for autoantigen presentation, processing and autoantibody induction.
McArthur
Carole
C
Pathology Department, Truman Medical Center, 2301 Holmes Road, Kansas City, MO 64108, USA. mcarthurc@umkc.edu
Wang
Yan
Y
Veno
Patricia
P
Zhang
Jianghong
J
Fiorella
Russell
R
D000917:Antibody Formation / Q000276:immunology; D017951:Antigen Presentation / Q000276:immunology; D000954:Antigens, Surface / Q000032:analysis / Q000276:immunology*; D017209:Apoptosis / Q000187:drug effects*; D001323:Autoantibodies / Q000276:immunology; D001324:Autoantigens / Q000032:analysis / Q000276:immunology*; D015153:Blotting, Western; D002352:Carrier Proteins / Q000032:analysis / Q000276:immunology*; D002462:Cell Membrane / Q000276:immunology; D002467:Cell Nucleus / Q000276:immunology; D003593:Cytoplasm / Q000276:immunology; D004591:Electrophoresis, Polyacrylamide Gel; D005455:Fluorescent Antibody Technique; D006801:Humans; D008565:Membrane Proteins / Q000032:analysis / Q000276:immunology*; D008840:Microfilament Proteins / Q000032:analysis / Q000276:immunology*; D009687:Nuclear Proteins / Q000276:immunology; D011065:Poly(ADP-ribose) Polymerases / Q000032:analysis*; D021381:Protein Transport; D020733:RNA, Small Cytoplasmic; D012261:Ribonucleoproteins / Q000032:analysis / Q000276:immunology*; D012469:Salivary Glands / Q000166:cytology / Q000187:drug effects*; D012859:Sjogren's Syndrome / Q000276:immunology; D014157:Transcription Factors / Q000032:analysis / Q000276:immunology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D000097585:SS-B Antigen; D013049:Spectrin; D000099207:SS-A Antigen
D000954:Antigens, Surface; D001323:Autoantibodies; D001324:Autoantigens; D002352:Carrier Proteins; D008565:Membrane Proteins; D008840:Microfilament Proteins; D009687:Nuclear Proteins; D011065:Poly(ADP-ribose) Polymerases; D020733:RNA, Small Cytoplasmic; D012261:Ribonucleoproteins; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D000097585:SS-B Antigen; D013049:Spectrin; D000099207:SS-A Antigen; C116006:RO60 protein, human