title: The involvement of MAPK signaling pathways in determining the cellular response to p53 activation: cell cycle arrest or apoptosis.
abstract: The effect of ERK, p38, and JNK signaling on p53-dependent apoptosis and cell cycle arrest was investigated using a Friend murine erythroleukemia virus (FVP)-transformed cell line that expresses a temperature-sensitive p53 allele, DP16.1/p53ts. In response to p53 activation at 32 degrees C, DP16.1/p53ts cells undergo p53-dependent G(1) cell cycle arrest and apoptosis. As a result of viral transformation, these cells express the spleen focus forming env-related glycoprotein gp55, which can bind to the erythropoietin receptor (EPO-R) and mimics many aspects of EPO-induced EPO-R signaling. We demonstrate that ERK, p38 and JNK mitogen-activated protein kinases (MAPKs) are constitutively active in DP16.1/p53ts cells. Constitutive MEK activity contributes to p53-dependent apoptosis and phosphorylation of p53 on serine residue 15. The pro-apoptotic effect of this MAPK kinase signal likely reflects an aberrant Ras proliferative signal arising from FVP-induced viral transformation. Inhibition of MEK alters the p53-dependent cellular response of DP16.1/p53ts from apoptosis to G(1) cell cycle arrest, with a concomitant increase in p21(WAF1), suggesting that the Ras/MEK pathway may influence the cellular response to p53 activation. p38 and JNK activity in DP16.1/p53ts cells is anti-apoptotic and capable of limiting p53-dependent apoptosis at 32 degrees C. Moreover, JNK facilitates p53 protein turnover, which could account for the enhanced apoptotic effects of inhibiting this MAPK pathway in DP16.1/p53ts cells. Overall, these data show that intrinsic MAPK signaling pathways, active in transformed cells, can both positively and negatively influence p53-dependent apoptosis, and illustrate their potential to affect cancer therapies aimed at reconstituting or activating p53 function.
authors.affiliation: Ontario Cancer Institute and Department of Medical Biophysics, University of Toronto, Canada.
authors.forename: Lauren
authors.initials: L
authors.lastname: Brown
authors.forename: Samuel
authors.initials: S
authors.lastname: Benchimol
mesh_terms: D000818:Animals; D017209:Apoptosis; D002453:Cell Cycle; D045744:Cell Line, Tumor; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000502:physiology; D048031:JNK Mitogen-Activated Protein Kinases / Q000502:physiology; D020935:MAP Kinase Signaling System / Q000502:physiology*; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000502:physiology; D010766:Phosphorylation; D016159:Tumor Suppressor Protein p53 / Q000032:analysis / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000502:physiology
chemical_list: C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016159:Tumor Suppressor Protein p53; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases