Cdk5 phosphorylates non-genotoxically overexpressed p53 following inhibition of PP2A to induce cell cycle arrest/apoptosis and inhibits tumor progression

Molecular Cancer

Research

Amrendra K Ajay¹  Ratna Kumari¹  Maleppillil V Vijayakumar¹  Ramanamurthy Boppana¹  Manoj K Bhat¹  Vimal Pandey¹  Sandeep Singh²  Ankur K Upadhyay³ 

[1] National Centre for Cell Science, NCCS Complex, 411007, Ganeshkhind, Pune, India;National Centre for Cell Science, NCCS Complex, 411007, Ganeshkhind, Pune, India;Current Address: H. Lee Moffitt Cancer Center, Tampa, Florida, USA;National Centre for Cell Science, NCCS Complex, 411007, Ganeshkhind, Pune, India;Current Address: Ranbaxy Research Laboratory, Gurgaon, Haryana, India;

关键词: HeLa Cell;    Cell Cycle Arrest;    Electrophoretic Mobility Shift Assay;    Okadaic Acid;    Chloramphenicol Acetyl Transferase;   

DOI  :  10.1186/1476-4598-9-204

 received in 2010-03-11, accepted in 2010-07-31,  发布年份 2010

来源: Springer

【 摘 要 】

Backgroundp53 is the most studied tumor suppressor and its overexpression may or may not cause cell death depending upon the genetic background of the cells. p53 is degraded by human papillomavirus (HPV) E6 protein in cervical carcinoma. Several stress activated kinases are known to phosphorylate p53 and, among them cyclin dependent kinase 5 (Cdk5) is one of the kinase studied in neuronal cell system. Recently, the involvement of Cdk5 in phosphorylating p53 has been shown in certain cancer types. Phosphorylation at specific serine residues in p53 is essential for it to cause cell growth inhibition. Activation of p53 under non stress conditions is poorly understood. Therefore, the activation of p53 and detection of upstream kinases that phosphorylate non-genotoxically overexpressed p53 will be of therapeutic importance for cancer treatment.ResultsTo determine the non-genotoxic effect of p53; Tet-On system was utilized and p53 inducible HPV-positive HeLa cells were developed. p53 overexpression in HPV-positive cells did not induce cell cycle arrest or apoptosis. However, we demonstrate that overexpressed p53 can be activated to upregulate p21 and Bax which causes G2 arrest and apoptosis, by inhibiting protein phosphatase 2A. Additionally, we report that the upstream kinase cyclin dependent kinase 5 interacts with p53 to phosphorylate it at Serine20 and Serine46 residues thereby promoting its recruitment on p21 and bax promoters. Upregulation and translocation of Bax causes apoptosis through intrinsic mitochondrial pathway. Interestingly, overexpressed activated p53 specifically inhibits cell-growth and causes regression in vivo tumor growth as well.ConclusionPresent study details the mechanism of activation of p53 and puts forth the possibility of p53 gene therapy to work in HPV positive cervical carcinoma.

【 授权许可】

Unknown   
© Ajay et al; licensee BioMed Central Ltd. 2010. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.