Peptidyl Prolyl Isomerase PIN1 Directly Binds to and Stabilizes Hypoxia-Inducible Factor-1α.

Hyeong-Jun Han,Hyewon Youn,Young-Joon Surh,Hoang Kieu Chi Ngo,Sang-Hyun Min,June-Key Chung,Kyung Oh Jung,Do-Hee Kim,Juan-Yu Piao,Young-Nam Cha,Nayoung Kwon,Su-Jung Kim,Bu Young Choi,Min-A Choi

doi:10.1371/journal.pone.0147038

Abstract

Peptidyl prolyl isomerase (PIN1) regulates the functional activity of a subset of phosphoproteins through binding to phosphorylated Ser/Thr-Pro motifs and subsequently isomerization of the phosphorylated bonds. Interestingly, PIN1 is overexpressed in many types of malignancies including breast, prostate, lung and colon cancers. However, its oncogenic functions have not been fully elucidated. Here, we report that PIN1 directly interacts with hypoxia-inducible factor (HIF)-1α in human colon cancer (HCT116) cells. PIN1 binding to HIF-1α occurred in a phosphorylation-dependent manner. We also found that PIN1 interacted with HIF-1α at both exogenous and endogenous levels. Notably, PIN1 binding stabilized the HIF-1α protein, given that their levels were significantly increased under hypoxic conditions. The stabilization of HIF-1α resulted in increased transcriptional activity, consequently upregulating expression of vascular endothelial growth factor, a major contributor to angiogenesis. Silencing of PIN1 or pharmacologic inhibition of its activity abrogated the angiogenesis. By utilizing a bioluminescence imaging technique, we were able to demonstrate that PIN1 inhibition dramatically reduced the tumor volume in a subcutaneous mouse xenograft model and angiogenesis as well as hypoxia-induced transcriptional activity of HIF-1α. These results suggest that PIN1 interacting with HIF-1α is a potential cancer chemopreventive and therapeutic target.

Highlights

Hypoxia, which results from an imbalance between the supply and use of oxygen in tumor microenvironment, contributes to tumor propagation, malignant progression, and resistance to anticancer therapy [1]
glutathione S-transferase (GST)-PIN1 fusion protein, but not GST protein, pulled down a substantial amount of hypoxia-inducible factor (HIF)-1α from lysates of HCT116 cells subjected to hypoxia, indicative of a direct interaction between PIN1 and HIF-1α (Fig 1A)
HEK293T cells were co-transfected with expression vectors encoding Flag epitope-tagged HIF-1α and HA-tagged PIN1, and whole-cell lysates were immunoprecipitated with anti-Flag antibody

Summary

Introduction

Hypoxia, which results from an imbalance between the supply and use of oxygen in tumor microenvironment, contributes to tumor propagation, malignant progression, and resistance to anticancer therapy [1]. Transcription of many hypoxic-inducible genes is mainly controlled by hypoxia-inducible factor (HIF)-1 These include those genes encoding angiogenic cytokines, such as vascular endothelial growth factor (VEGF) and its receptors VEGFR1 and VEGFR2 [2]. HIF-1α undergoes hydroxylation by prolyl hydroxylase, and subsequently interacts with the von Hippel Lindau (pVHL) protein. This facilitates the HIF-1α degradation through the ubiquitin-proteasome pathway [6]. Cyclin-dependent kinase promotes stabilization of HIF-1α through phosphorylation of HIF-1α on Ser668 under both normoxic and hypoxic conditions [12]. It remains poorly understood how phosphorylation of HIF-1α influences the stability of HIF-1α

Methods

Results

Conclusion