Zyxin Is a Critical Regulator of the Apoptotic HIPK2-p53 Signaling Axis

Abstract

HIPK2 activates the apoptotic arm of the DNA damage response by phosphorylating tumor suppressor p53 at serine 46. Unstressed cells keep HIPK2 levels low through targeted polyubiquitination and subsequent proteasomal degradation. Here we identify the LIM domain protein Zyxin as a novel regulator of the HIPK2-p53 signaling axis in response to DNA damage. Remarkably, depletion of endogenous Zyxin, which colocalizes with HIPK2 at the cytoskeleton and in the cell nucleus, stimulates proteasome-dependent HIPK2 degradation. In contrast, ectopic expression of Zyxin stabilizes HIPK2, even upon enforced expression of its ubiquitin ligase Siah-1. Consistently, Zyxin physically interacts with Siah-1, and knock-down of Siah-1 rescues HIPK2 expression in Zyxin-depleted cancer cells. Mechanistically, our data suggest that Zyxin regulates Siah-1 activity through interference with Siah-1 dimerization. Furthermore, we show that endogenous Zyxin coaccumulates with HIPK2 in response to DNA damage in cancer cells, and that depletion of endogenous Zyxin results in reduced HIPK2 protein levels and compromises DNA damage-induced p53 Ser46 phosphorylation and caspase activation. These findings suggest an unforeseen role for Zyxin in DNA damage-induced cell fate control through modulating the HIPK2-p53 signaling axis. Cancer Res; 71(6); 2350-9. Ó2011 AACR.

The Prolactin Receptor Transactivation Domain Is Associated with Steroid Hormone Receptor Expression and Malignant Progression of Breast Cancer

“…These novel PRL-induced target genes are significant for the following reasons: i) RASD1 functions as a tumor suppressor gene by inhibiting cell growth, 66 ii) MYADM is important for the organization of lamellipodium extension and cell motility, 67 and iii) reports suggest that ZYX is a critical regulator of DNA damageeinduced cell death induction. 68 The role of such genes in normal and malignant processes within the mammary gland requires further characterization, but it will ultimately contribute to the overall knowledge of the complex PRL/PRLr signaling network.…”

Src kinase modulates the apoptotic p53 pathway by altering HIPK2 localization

“…13,14,21 When we coexpressed kinase-activated Src with constant amounts of a HIPK2 expression construct, we recognized an increase in HIPK2 protein levels (Fig. 3A).…”

“…21 U2OS cells were seeded on coverslips in 24-well plates, approximately 2 × 10 5 cells per well. Cells were transfected on the next day, and 24 h later, cells were fixed in fresh 4% paraformaldehyde in PBS buffer for 20 min.…”

“…13,16,21 HIPK2 Y354F mutant was generated using sitedirected mutagenesis and standard PCR techniques. Src kinasedead (K297M) and kinase-active (Y527F) mutants were kindly provided by Dr Nina Reuven.…”

“…[18][19][20] It has been previously described that HIPK2 is not exclusively distributed to the cell nucleus but can also localize to the cytoplasm. [21][22][23] However, little is known about the cellular pathways and mechanisms that modulate HIPK2 localization.…”