Temporal Phosphoproteome Dynamics Induced by an ATP Synthase Inhibitor Citreoviridin*

Chia-Wei Hu,Chia-Lang Hsu,Yu-Chao Wang,Yasushi Ishihama,Wei-Chi Ku,Hsuan-Cheng Huang,Hsueh-Fen Juan

doi:10.1074/mcp.m115.051383

Abstract

Citreoviridin, one of toxic mycotoxins derived from fungal species, can suppress lung cancer cell growth by inhibiting the activity of ectopic ATP synthase, but has limited effect on normal cells. However, the mechanism of citreoviridin triggering dynamic molecular responses in cancer cells remains unclear. Here, we performed temporal phosphoproteomics to elucidate the dynamic changes after citreoviridin treatment in cells and xenograft model. We identified a total of 829 phosphoproteins and demonstrated that citreoviridin treatment affects protein folding, cell cycle, and cytoskeleton function. Furthermore, response network constructed by mathematical modeling shows the relationship between the phosphorylated heat shock protein 90 β and mitogen-activated protein kinase signaling pathway. This work describes that citreoviridin suppresses cancer cell growth and mitogen-activated protein kinase/extracellular signal-regulated kinase signaling by site-specific dephosphorylation of HSP90AB1 on Serine 255 and provides perspectives in cancer therapeutic strategies.

Highlights

Citreoviridin is a toxic secondary metabolite produced by Penicillium citreoviride species and contains ␣-pyrone, a sixmembered cyclic unsaturated ester that binds to the ATP synthase ␤ subunit and causes toxicity to bacteria [1, 2]
Quantitative Analysis of Dynamic Phosphorylation Profiles of Lung Cancer Cells with Citreoviridin Treatment—To characterize the temporal phosphorylation dynamics in response to citreoviridin treatment in lung cancer cells, a quantitative phosphoproteomic approach was applied in this study
The Phosphosite Ser255 of HSP90AB1 is Crucial for mitogen-activated protein kinases (MAPKs)/ ERK1 Signaling—In this study, we found that citreoviridin treatment affected phosphorylation instead of protein levels in HSP90AB1 (Fig. 5B and 5C), implying the regulatory importance of site-specific phosphorylation of HSP90AB1

Summary

Introduction

Citreoviridin is a toxic secondary metabolite produced by Penicillium citreoviride species and contains ␣-pyrone, a sixmembered cyclic unsaturated ester that binds to the ATP synthase ␤ subunit and causes toxicity to bacteria [1, 2]. Recent studies have revealed that ATP synthase is expressed on the cell surface of keratinocyte, hepatocyte, and adipocytes, as well as endothelial, neuronal, and cancer cells (10 –19). After citreoviridin treatment on cells with ectopically expressed ATP synthase, there was no change in the mitochondrial membrane potential, suggesting that citreoviridin inhibited the activity of ectopic, but not mitochondrial ATP synthase [10]. The inhibition of ecto-ATP synthase by citreoviridin stimulates the unfoldedprotein response and elevates levels of ROS in lung cancer cells [10]. Quantitative proteomic analysis of human lung tumor xenografts showed that citreoviridin induces alternations in the expression of glucose metabolism-related enzymes and suggested that citreoviridin may reduce the glycolytic intermediates for macromolecule synthesis and inhibit cell proliferation [20]. Recent advances in quantitative phosphoproteomic profiling allows researchers to study the aberrant regulation of signaling pathways and assists in the discovery of appropriate therapeutic targets for various diseases [23, 25,26,27]

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Conclusion