Annexin A2 is a novel Cellular Redox Regulatory Protein involved in Tumorigenesis

Patricia Alexandra Madureira,Victoria Ann Miller,Patrick Wing Kwong Lee,Richard Hill,David Morton Waisman,Carman Giacomantonio

doi:10.18632/oncotarget.375

Abstract

Annexins are a structurally related family of calcium and phospholipid-binding proteins that are involved in the regulation of a wide range of molecular and cellular processes. Annexin A2 is unique among the annexins in that it possesses redox sensitive cysteine(s). The ubiquitous and abundant expression of ANXA2 in cells and its reactivity with hydrogen peroxide led us to hypothesize that this protein could play a role in cellular redox regulation. Here we show that ANXA2 protein levels are induced by hydrogen peroxide. Furthermore, depletion of ANXA2 resulted in the elevation of cellular reactive oxygen species (ROS) upon oxidative stress, increased activation of the ROS-induced pro-apoptotic kinases, JNK, p38 and Akt and elevated sensitivity to ROS-mediated cellular damage/death. ANXA2-null mice showed significantly elevated protein oxidation in the liver and lung tissues compared to WT mice. ANXA2 depleted cancer cells showed enhanced cellular protein oxidation concomitant with decreased tumor growth compared to control cancer cells and both the protein oxidation and tumor growth deficit were reversed by the antioxidant N-acetyl cysteine, indicating that ANXA2 redox regulatory function plays a major role in tumorigenesis. Ex-vivo human cancer studies showed that up-regulation of the reduced form of ANXA2 is associated with protection of the tumor proteins from oxidation. In summary, our results indicate that ANXA2 redox regulatory function plays an important role protecting cells from oxidative stress, particularly during tumorigenesis.

Highlights

Reactive oxygen species (ROS) are oxygencontaining reactive chemical species which include such biologically important molecules as superoxide, nitric oxide, hydroxyl radical and hydrogen peroxide (H2O2)
In order to test if Annexin A2 (ANXA2) plays a role in cellular redox regulation we investigated if this protein is sensitive to H2O2-induced oxidative stress
TIME cells were incubated with epidermal growth factor (EGF) and cellular extracts were either analyzed by SDS-PAGE followed by western blotting for ANXA2 or incubated with Biotin-conjugated iodoacetamide (BIAM) and the labeled/ biotinylated proteins purified by incubation with streptavidin beads, followed by SDSPAGE and western blotting for ANXA2

Summary

Introduction

Reactive oxygen species (ROS) are oxygencontaining reactive chemical species which include such biologically important molecules as superoxide, nitric oxide, hydroxyl radical and hydrogen peroxide (H2O2). Endogenous H2O2 is a by-product of mitochondrial respiration [1]. Various signaling molecules, including growth factors, cytokines, hormones and neurotransmitters induce increases in intracellular H2O2 through the activation of NADPH oxidases (Nox). The production of a cytotoxic molecule has obvious potential risks to the cells as H2O2 is a major contributor to DNA damage, protein oxidation and lipid peroxidation [5, 6]. Cells show a biphasic response to increased H2O2 levels; this is due to its role as a second messenger in intracellular signaling cascades (proliferative effect) and at high concentrations as an oxidant of proteins, lipids and nucleic acids (apoptotic and/or necrotic effect)

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