title: Involvement of p38 in apoptosis-associated membrane blebbing and nuclear condensation.
abstract: The stress-activated protein kinase p38 is often induced by cytotoxic agents, but its contribution to cell death is ill defined. In Rat-1 cells, we found a strong correlation between activation of p38 and induction of c-Myc-dependent apoptosis. In cells with deregulated c-Myc expression but not in control cells, cis-diamminedichloroplatinum induced p38 activity and typical features of apoptosis, including internucleosomal DNA degradation, induction of caspase activities, and both nuclear (nuclear condensation and fragmentation) and extranuclear (cell blebbing) morphological alterations. The pan-caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone did not block p38 activation and the p38 inhibitor SB203580 had no detectable effect on the activation of caspases or the in vivo cleavage of several caspase substrates, suggesting that p38 and caspase activation can contribute distinct features of apoptosis. Accordingly, we found that cell blebbing was independent of caspase activity and, rather, depended on p38-sensitive changes in microfilament dynamics likely mediated by heat shock protein 27 phosphorylation. Furthermore, p38 activity contributed to both caspase-dependent and caspase-independent nuclear condensation and fragmentation, suggesting a role in an early event triggering both mechanisms of apoptosis or sensitizing the cells to the action of both types of apoptosis executioners. Inhibiting p38 also resulted in a significant enhancement in cell survival estimated by colony formation. This capacity to modulate the sensitivity to apoptosis in cells with deregulated c-Myc expression suggests an important role for p38 in tumor cell killing by chemotherapeutic agents.
authors.affiliation: Centre de recherche en cancérologie de l'Université Laval, L'Hôtel-Dieu de Québec, Centre hospitalier universitaire de Québec, 9 rue McMahon, Québec, Canada G1R 2J6.
authors.forename: R G
authors.initials: RG
authors.lastname: Deschesnes
authors.forename: J
authors.initials: J
authors.lastname: Huot
authors.forename: K
authors.initials: K
authors.lastname: Valerie
authors.forename: J
authors.initials: J
authors.lastname: Landry
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism*; D002470:Cell Survival; D002945:Cisplatin / Q000494:pharmacology; D053938:DNA Fragmentation; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation; D055551:HSP27 Heat-Shock Proteins; D006367:HeLa Cells; D006360:Heat-Shock Proteins; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D018832:Molecular Chaperones; D009363:Neoplasm Proteins / Q000494:pharmacology; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D013997:Time Factors; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases; D000099190:MAP-Kinase-Activated Kinase 2
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D000970:Antineoplastic Agents; D020169:Caspases; D002945:Cisplatin; D004791:Enzyme Inhibitors; D055551:HSP27 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D006861:Hydrogen Peroxide; D007093:Imidazoles; D047908:Intracellular Signaling Peptides and Proteins; D020928:Mitogen-Activated Protein Kinases; D018832:Molecular Chaperones; D009363:Neoplasm Proteins; D017346:Protein Serine-Threonine Kinases; D016271:Proto-Oncogene Proteins c-myc; D011725:Pyridines; D048051:p38 Mitogen-Activated Protein Kinases; D000099190:MAP-Kinase-Activated Kinase 2; C057725:HSPB1 protein, human; C486114:Hspb1 protein, rat; C426824:benzyloxycarbonyl-valyl-alanyl-(methyl)aspartic acid fluoromethyl ketone; C093642:SB 203580