SHP-2 tyrosine phosphatase inhibits p73-dependent apoptosis and expression of a subset of p53 target genes induced by EGCG.
Green tea polyphenol, epigallocatechin-3-gallate (EGCG) differentially regulates the cellular growth of cancer cells in a p53-dependent manner through apoptosis and/or cell cycle arrest. In an effort to further elucidate the mechanism of differential growth regulation by EGCG, we have investigated the role of the tyrosine phosphatase, SHP-2. Comparing the responses of mouse embryonic fibroblasts (MEFs), expressing either WT or functionally inactive/truncated SHP-2, we find that inactivation of SHP-2 remarkably sensitizes cells to EGCG-mediated killing. MEFs lacking functional SHP-2 undergo massive apoptosis upon treatment with EGCG. By comparing gene expression profiles, we have identified a set of transcriptional targets of p53 that are differentially modulated in cells undergoing apoptosis. Western blot and real-time PCR analyses of a select group of genes further confirm that the expression is SHP-2-dependent. Similar observations were made in MEFs lacking p53, confirming that the expression of these "p53 target genes" is p53-independent. In addition, EGCG treatment induced the expression of p73 mRNA and protein in both cell types, but not p63. Inactivation of p73 in cells expressing nonfunctional SHP-2 markedly inhibited apoptosis and p53 target gene expression. Although phosphorylation of JNK is differentially regulated by SHP2, it was found to be dispensable for EGCG-induced apoptosis and p53 target gene expression. Our results have identified SHP-2 as a negative regulator of EGCG-induced-apoptosis and have identified a subset of p53 target genes whose expression is paradoxically not mediated by p53 but by one of its family members, p73.
Amin
A R M Ruhul
AR
Department of Genetics, Case Western Reserve University, Cleveland, OH 44106, USA.
Thakur
Vijay S
VS
Paul
Rajib K
RK
Feng
Gen Sheng
GS
Qu
Cheng-Kui
CK
Mukhtar
Hasan
H
Agarwal
Munna L
ML
D000818:Animals; D017209:Apoptosis; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D015971:Gene Expression Regulation, Enzymologic; D020287:In Situ Nick-End Labeling; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry* / Q000378:metabolism; D020935:MAP Kinase Signaling System; D051379:Mice; D009687:Nuclear Proteins / Q000378:metabolism*; D018384:Oxidative Stress; D010766:Phosphorylation; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry* / Q000378:metabolism; D013662:Tea; D015533:Transcriptional Activation; D000072160:Tumor Protein p73; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
D004268:DNA-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; D013662:Tea; C000606368:Trp73 protein, mouse; D000072160:Tumor Protein p73; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D002392:Catechin; C045651:epigallocatechin gallate; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D017027:Protein Tyrosine Phosphatases; C516725:Ptpn11 protein, mouse