Paxillin mediates extranuclear and intranuclear signaling in prostate cancer proliferation
Aritro Sen, … , Randall Rossi, Stephen R. Hammes
Aritro Sen, … , Randall Rossi, Stephen R. Hammes
Published June 11, 2012
Citation Information: J Clin Invest. 2012;122(7):2469-2481. https://doi.org/10.1172/JCI62044.
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Research Article Oncology

Paxillin mediates extranuclear and intranuclear signaling in prostate cancer proliferation

Abstract

In prostate cancer, the signals that drive cell proliferation change as tumors progress from castration-sensitive (androgen-dominant) to castration-resistant states. While the mechanisms underlying this change remain uncertain, characterization of common signaling components that regulate both stages of prostate cancer proliferation is important for developing effective treatment strategies. Here, we demonstrate that paxillin, a known cytoplasmic adaptor protein, regulates both androgen- and EGF-induced nuclear signaling. We show that androgen and EGF promoted MAPK-dependent phosphorylation of paxillin, resulting in nuclear translocation of paxillin. We found nuclear paxillin could then associate with androgen-stimulated androgen receptor (AR). This complex bound AR-sensitive promoters, retaining AR within the nucleus and regulating AR-mediated transcription. Nuclear paxillin also complexed with ERK and ELK1, mediating c-FOS and cyclin D1 expression; this was followed by proliferation. Thus, paxillin is a liaison between extranuclear MAPK signaling and nuclear transcription in response to androgens and growth factors, making it a potential regulator of both castration-sensitive and castration-resistant prostate cancer. Accordingly, paxillin was required for normal growth of human prostate cancer cell xenografts, and its expression was elevated in human prostate cancer tissue microarrays. Paxillin is therefore a potential biomarker for prostate cancer proliferation and a possible therapeutic target for prostate cancer treatment.

Authors

Aritro Sen, Ismary De Castro, Donald B. DeFranco, Fang-Ming Deng, Jonathan Melamed, Payel Kapur, Ganesh V. Raj, Randall Rossi, Stephen R. Hammes

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Figure 6

PS-PXN regulates c-FOS mRNA expression in the nucleus by complexing with ERK and ELK1 to allow ERK-mediated activation of ELK1.

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PS-PXN regulates c-FOS mRNA expression in the nucleus by complexing with...
(A and B) PS-PXN is essential for EGF-induced phosphorylation of ELK1 and c-FOS mRNA expression. Immunoblot (A) and qPCR (B) analysis in PC3 cells (treated with Nsp or PXN-specific siRNA) showing EGF-induced (20 ng/ml; 30 minutes) (A) phosphorylation of ELK1 and (B) c-FOS mRNA expression. PXN-knockdown cells were also transfected with plasmids expressing WT PXN or PXN lacking the MAPK-targeted serines (S→A). Data are represented as mean ± SEM (n = 3). *P ≤ 0.005 relative to medium. (C) PS-PXN forms a complex with ERK and ELK1 in the nucleus. IP assays were performed in nuclear extracts of LNCaP cells treated with EGF (20 ng/ml, 24 hours) (n = 3 experiments with identical results). Either PXN, PS-PXN, ERK, p-ERK, or p-ELK1 were precipitated, followed by immunoblotting as indicated. (D) ERK and ELK1, but not PXN, bind to the c-FOS promoter in EGF-stimulated PC3 cells. PC3 cells were serum starved overnight, followed by treatment with medium or EGF (20 ng/ml) for 24 hours, before chromatin IP. The occupancy of ERK, p-ELK1, and PXN on c-FOS promoter was examined. Values are presented as percentage input (mean ± SEM, n = 3). *P ≤ 0.005 with respect to medium. Representative immunoblot shows equal amounts of ERK, p-ELK1, and PXN were IP from medium (M) and EGF-treated samples.