The physical interaction of p53 and plakoglobin is necessary for their synergistic inhibition of migration and invasion

Abstract

Plakoglobin (PG) is a paralog of β-catenin with similar adhesive, but contrasting signalling functions. Although β-catenin has well-known oncogenic function, PG generally acts as a tumor/metastasis suppressor by mechanisms that are just beginning to be deciphered. Previously, we showed that PG interacted with wild type (WT) and a number of mutant p53s, and that its tumor/metastasis suppressor activity may be mediated, at least partially, by this interaction. Here, carcinoma cell lines deficient in both p53 and PG (H1299), or expressing mutant p53 in the absence of PG (SCC9), were transfected with expression constructs encoding WT and different fragments and deletions of p53 and PG, individually or in pairs. Transfectants were characterized for their in vitro growth, migratory and invasive properties and for mapping the interacting domain of p53 and PG. We showed that when coexpressed, p53-WT and PG-WT cooperated to decrease growth, and acted synergistically to significantly reduce cell migration and invasion. The DNA-binding domain of p53 and C-terminal domain of PG mediated p53/PG interaction, and furthermore, the C-terminus of PG played a central role in the inhibition of invasion in association with p53.

Plakoglobin restores tumor suppressor activity of p53R175H mutant by sequestering the oncogenic potential of β‐catenin

“…Previously, we have shown that plakoglobin interacted with p53 and several mp53 proteins using different carcinoma cell lines . To verify plakoglobin interaction with p53 R175H , we processed H1299 transfectants coexpressing plakoglobin and p53 R175H for reciprocal coimmunoprecipitation (Co‐IP) and immunoblotting (IB) with plakoglobin and p53 antibodies (Figure B).…”

“…Hemagglutinin (HA)-tagged p53 has been described previously. 18,46 The pcDNA3.1/hygro-plakoglobin construct was generated using the previously described FLAG-tagged plakoglobin as a template. 29 The p53 R175H expression construct was a gift from Dr Giovanni Blandino.…”

“…p53 functions are regulated by post‐translational modifications and protein‐protein interactions . We have identified plakoglobin (γ‐catenin) as an endogenous interacting partner of wild type as well as a number of most frequent mutant p53 (mp53) in various carcinoma cell lines of different origins and have shown that its interaction with mp53 restores mp53 tumor suppressor activities in vitro . Plakoglobin is an armadillo protein family member and is a paralog of β‐catenin with similar dual cell‐cell adhesion and signaling activities .…”

“…15 We have identified plakoglobin (c-catenin) as an endogenous interacting partner of wild type as well as a number of most frequent mutant p53 (mp53) in various carcinoma cell lines of different origins and have shown that its interaction with mp53 restores mp53 tumor suppressor activities in vitro. [16][17][18][19] Plakoglobin is an armadillo protein family member and is a paralog of b-catenin with similar dual cell-cell adhesion and signaling activities. 20,21 However, unlike b-catenin that acts as an oncogene through its interaction with the transcription factors T-cell factor/ lymphoid enhancer-binding factor (TCF/LEF), and activation of Wnt signaling pathway, 22,23 plakoglobin generally acts as a tumor/metastasis suppressor.…”

“…20,21 However, unlike b-catenin that acts as an oncogene through its interaction with the transcription factors T-cell factor/ lymphoid enhancer-binding factor (TCF/LEF), and activation of Wnt signaling pathway, 22,23 plakoglobin generally acts as a tumor/metastasis suppressor. 20,21,[24][25][26][27] We have shown that plakoglobin can act as a tumor/metastasis suppressor by at least 3 mechanisms: regulation of stability and subcellular localization of growth regulating molecules, 19,25,28 interaction with transcription factors involved in the regulation of cell growth and metastasis [16][17][18][19]25 and sequestration of b-catenin oncogenic activities; 29 see also. [30][31][32][33][34] p53 GOF mutations can induce aberrant accumulation and increased transcriptional activation of b-catenin in cancer cells.…”