Cell-penetrating autoantibody induces caspase-mediated apoptosis through catalytic hydrolysis of DNA.
In the present study, we investigated the substrate specificity of catalytic activity of a cytotoxic anti-DNA monoclonal autoantibody, G1-5, which was obtained from an MRL-lpr/lpr mouse by hybridoma technology. The antibody catalyzed hydrolysis of single- and double-stranded DNA with a higher substrate specificity for thymine than adenine by either beta-glycosidic or phosphodiester bond cleavage. The hydrolysis rate (kcat) showed maximum at acidic pH conditions, suggesting that the catalytic site of the antibody contains essential carboxylic group(s). Treatment of cells with the antibody promoted cell death and induced the activation of caspases. The cell death induced by the antibody was inhibited by the pan-caspase inhibitor. Furthermore, the antibody binds to cell membrane and penetrates into the cells. Our results suggest that the cell death is initiated by antibodies penetrating to cells and nucleus, hydrolyzing considerable amount of DNA, and mediating the caspase-dependent apoptotic pathway.
Lee
Eun-Jung
EJ
Laboratory of Immunology, Institute for Medical Science and BK 21 Program, Ajou University, School of Medicine, Suwon 443-721, Republic of Korea.
Jang
Eun-Jung
EJ
Lee
Eunhae
E
Yu
Jaehoon
J
Chung
Hee Yong
HY
Jang
Young-Ju
YJ
D000595:Amino Acid Sequence; D001323:Autoantibodies / Q000737:chemistry / Q000378:metabolism*; D020169:Caspases / Q000378:metabolism*; D002384:Catalysis; D004247:DNA / Q000378:metabolism*; D018922:HL-60 Cells; D006801:Humans; D006868:Hydrolysis; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid
D001323:Autoantibodies; D004247:DNA; D020169:Caspases