Expression of a Fas-like proapoptotic molecule on the lymphocytes of Xenopus laevis.
Ligation of the externally expressed Fas (APO1/CD95) molecule will initiate programmed cell death (apoptosis), in many mammalian developing and adult cells. Fas-induced apoptosis has not been demonstrated with the cells of any non-mammalian vertebrate. We immunostained suspensions of splenocytes from adult Xenopus laevis, the South African clawed toad, with a polyclonal rabbit anti-human Fas antibody raised against the amino acid residues 321-335 of human Fas. The binding was specific, as it was dramatically reduced by preincubation of the antibody with the Fas peptide used to make it, but not with a Fas-ligand (FasL) peptide. The binding was enhanced after in vitro exposure of the splenocytes to phytahemagglutinin (PHA), a T cell mitogen and apoptogen in this species. Sections of developing Xenopus larval tissue were also immunostained with the polyclonal rabbit anti-human Fas antibody. Consistent binding of thymocytes and splenocytes was not observed until early metamorphosis in these immunological sites. A monoclonal mouse anti-human Fas antibody, previously used to stimulate apoptosis in mammalian cells, induced significant levels of apoptosis in adult Xenopus splenocytes and additionally, bound specifically to a splenocyte extract, as assayed by ELISA. Thus, a molecule on Xenopus splenocytes shares both structural and functional homologies with human Fas, indicating the evolutionary conservation within vertebrates of this means of initiating apoptosis.
Mangurian
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Institute for Health Policy Studies, University of California, San Francisco, 94109, USA.
Johnson
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McMahan
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Clothier
R H
RH
Ruben
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LN
D000818:Animals; D000906:Antibodies; D000911:Antibodies, Monoclonal / Q000276:immunology; D000918:Antibody Specificity; D017209:Apoptosis / Q000187:drug effects; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000276:immunology; D019143:Evolution, Molecular; D053222:Fas Ligand Protein; D007150:Immunohistochemistry; D007814:Larva; D008214:Lymphocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000276:immunology; D016017:Odds Ratio; D010835:Phytohemagglutinins / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D013154:Spleen / Q000166:cytology / Q000196:embryology; D013950:Thymus Gland / Q000196:embryology; D014982:Xenopus laevis / Q000196:embryology / Q000276:immunology / Q000378:metabolism*; D019014:fas Receptor / Q000276:immunology / Q000378:metabolism*
D000906:Antibodies; D000911:Antibodies, Monoclonal; D000939:Epitopes; C505661:FASLG protein, human; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D008562:Membrane Glycoproteins; D010835:Phytohemagglutinins; D019014:fas Receptor