Dying enterocytes downregulate signaling pathways converging on Ras: rescue by protease inhibition.
Organ and cell cultures of the small intestine serve as excellent in vitro models for programmed cell death (PCD). Cells cultured in serum-free, minimal medium rapidly died, as evidenced by histological changes, internucleosomal DNA cleavage, and TdT-mediated dUTP nick end labeling. Cell death was pervasive, although nonepithelial cells within the fibrovascular villus core were spared. PCD did not require a functional p53 gene. Serine and cysteine protease inhibitors, but not FCS, suppressed it. Relative to structural and functional proteins, dying enterocytes rapidly downregulated Ras-convergent proteins, including epidermal growth factor receptor, Erb-B2, and the son of sevenless guanine nucleotide exchangers. Reductions in the steady-state levels of both protein and mRNA were observed. These reductions were prevented by a combination of death-defying serine and caspase inhibitors, indicating a requirement for the initiation of death. Thus, during catastrophic PCD, intestinal epithelial cells delete cell surface signaling pathways responsible for Ras activation.
Scheving
L A
LA
Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
Jin
W H
WH
Chong
K M
KM
Gardner
W
W
Cope
F O
FO
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D005821:Genetic Techniques; D006133:Growth Substances / Q000097:blood / Q000502:physiology; D006651:Histocytochemistry; D007421:Intestine, Small / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D009924:Organ Culture Techniques; D011480:Protease Inhibitors / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology*; D016159:Tumor Suppressor Protein p53 / Q000502:physiology; D018631:ras Proteins / Q000502:physiology*
D006133:Growth Substances; D011480:Protease Inhibitors; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D004247:DNA; D018631:ras Proteins