Fas-mediated apoptosis of proliferating, transiently growth-arrested, and senescent normal human fibroblasts.
Previous studies suggest that apoptotic signaling may require proteins that are critical to cellular proliferation and cell cycle regulation. To further examine this question, proliferating, transiently growth-arrested, and senescent normal human fibroblasts were induced to undergo apoptosis in response to two distinct mediators of apoptosis-Fas (APO-1/CD95) death receptor and staurosporine. Ligation of the Fas receptor in the presence of cycloheximide or actinomycin D resulted in apoptosis of proliferating cells, cells transiently growth arrested by gamma-irradiation or serum starvation (i.e., G(0) arrest), and permanently growth-arrested senescent fibroblasts. Proliferating and G(0)-arrested cells were also susceptible to staurosporine-mediated apoptosis. Surprisingly, gamma-irradiated cells did not undergo staurosporine-mediated apoptosis, and remained viable for a prolonged time. Fas-mediated apoptosis of senescent fibroblasts was evidenced by chromosome condensation and by activation of caspase-8 and -3, proteases crucial for the execution of the Fas apoptosis pathway. In addition, ligation of the Fas receptor in G(0)-arrested cells did not result in the activation of p34(cdc2) kinase, arguing that activation of this kinase is not essential in this apoptotic process. From these studies we conclude that proliferating, transiently growth-arrested, and senescent normal human fibroblasts are susceptible to apoptotic signals and that apoptosis is not necessarily dependent upon cell cycle or proliferative state of the cell.
Tepper
C G
CG
Rowe Program in Genetics, Department of Microbiology and Immunology, University of California, School of Medicine, Tupper Hall, Davis, California 95616, USA.
Seldin
M F
MF
Mudryj
M
M
D017209:Apoptosis / Q000187:drug effects / Q000276:immunology*; D016203:CDC2 Protein Kinase / Q000378:metabolism; D002455:Cell Division; D002460:Cell Line; D016922:Cellular Senescence; D004789:Enzyme Activation; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000276:immunology; D006801:Humans; D016192:Resting Phase, Cell Cycle; D015398:Signal Transduction; D019311:Staurosporine / Q000494:pharmacology; D019014:fas Receptor / Q000502:physiology*
D019014:fas Receptor; D016203:CDC2 Protein Kinase; D019311:Staurosporine