title: Pivotal role of the cyclin-dependent kinase inhibitor p21WAF1/CIP1 in apoptosis and autophagy.
abstract: Programmed cell death (PCD) is involved in a variety of biologic events. Based on the morphologic appearance of the cells, there are two types of PCD as follows: apoptotic (type I) and autophagic (type II). However, the molecular machinery that determines the type of PCD is poorly defined. The purpose of this study was to show whether the presence of the cyclin-dependent kinase (CDK) inhibitor p21(WAF1/CIP1), a modulator of apoptosis, determines which type of PCD the cell undergoes. Treatment with C(2)-ceramide was associated with both the cleavage of caspase-3 and poly(ADP-ribose) polymerase and the degradation of autophagy-related Beclin 1 and Atg5 proteins, without a change in the cyclin-CDK activity, which culminated in apoptosis in p21(+/+) mouse embryonic fibroblasts (MEFs). On the other hand, C(2)-ceramide did not cleave caspase-3 or poly(ADP-ribose) polymerase and kept Beclin 1 and Atg5 proteins stable in p21(-/-) MEFs, events that this time culminated in autophagy. When expression of the p21 protein was inhibited by small interfering RNA or when the overexpression of Beclin 1 or Atg5 was induced, autophagy rather than apoptosis was initiated in the p21(+/+) MEFs treated with C(2)-ceramide. In contrast, the exogenous expression of p21 or the silencing of Beclin 1 and Atg5 with small interfering RNA increased the number of apoptotic cells and decreased the number of autophagic cells among C(2)-ceramide-treated p21(-/-) MEFs. gamma-Irradiation, which endogenously generates ceramide, induced a similar tendency in these MEFs. These results suggest that p21 plays an essential role in determining the type of cell death, positively for apoptosis and negatively for autophagy.
authors.affiliation: Department of Neurosurgery, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, the.
authors.forename: Keishi
authors.initials: K
authors.lastname: Fujiwara
authors.affiliation: Department of Neurosurgery, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, the.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Daido
authors.affiliation: Department of Cell Biology and Bioscience, The Nagahama Institute of Bioscience and Technology, Nagahama, Shiga 526-0829, Japan, the.
authors.forename: Akitsugu
authors.initials: A
authors.lastname: Yamamoto
authors.affiliation: Department of Molecular Pathology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, the.
authors.forename: Ryuji
authors.initials: R
authors.lastname: Kobayashi
authors.affiliation: Department of Neurosurgery, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, the.
authors.forename: Tomohisa
authors.initials: T
authors.lastname: Yokoyama
authors.affiliation: Department of Neurosurgery, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, the.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Aoki
authors.affiliation: Department of Neurosurgery, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, the.
authors.forename: Eiji
authors.initials: E
authors.lastname: Iwado
authors.affiliation: Department of Neurosurgery, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, the.
authors.forename: Naoki
authors.initials: N
authors.lastname: Shinojima
authors.affiliation: Department of Neurosurgery, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, the.
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Kondo
authors.affiliation: Department of Neurosurgery, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, the; University of Texas Graduate School of Biomedical Sciences, Houston, Texas 77030, and the; Department of Neurosurgery, Baylor College of Medicine, Houston, Texas 77030. Electronic address: seikondo@mdanderson.org.
authors.forename: Seiji
authors.initials: S
authors.lastname: Kondo
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D051017:Apoptosis Regulatory Proteins; D001343:Autophagy / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D000071187:Autophagy-Related Protein 5; D000071186:Beclin-1; D015153:Blotting, Western; D053148:Caspase 3 / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D002518:Ceramides / Q000494:pharmacology; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism / Q000648:ultrastructure; D005434:Flow Cytometry; D005720:Gamma Rays; D015870:Gene Expression / Q000187:drug effects / Q000528:radiation effects; D020868:Gene Silencing; D047468:Immunoprecipitation; D051379:Mice; D046529:Microscopy, Electron, Transmission; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D051017:Apoptosis Regulatory Proteins; C495773:Atg5 protein, mouse; D000071187:Autophagy-Related Protein 5; D000071186:Beclin-1; C115010:Becn1 protein, mouse; D002518:Ceramides; D050759:Cyclin-Dependent Kinase Inhibitor p21; D008869:Microtubule-Associated Proteins; D011506:Proteins; D034741:RNA, Small Interfering; D011065:Poly(ADP-ribose) Polymerases; D053148:Caspase 3