Increase of the Intracellular Zinc Concentration Leads to an Activation and Internalisation of the Epidermal Growth Factor Receptor in A549 Cells.

Lisa-Marie Barth,Lothar Rink,Inga Wessels

doi:10.3390/ijms22010326

Abstract

(1) Background: Zinc is suggested to play a major role in epidermal growth factor (EGF)-induced cell regeneration and proliferation. To deepen the knowledge on the underlying mechanisms zinc’s effects on the epidermal growth factor receptor (EGFR) activation and its endocytosis was investigated in the alveolar carcinoma cell line A549. (2) Methods: An increase of intracellular zinc was generated by adding zinc extracellularly compared to the intracellular release of zinc from zinc-binding proteins by stimulation with a nitric oxide donor. Zinc-initiated EGFR phosphorylation was checked by Western blotting and receptor endocytosis assays were performed by using flow cytometry. (3) Results: Besides a dose-dependent EGFR phosphorylation, a dose- and time dependent significant receptor internalisation was initiated by both types of zinc increases. In addition, both increased intracellular zinc levels further promoted EGF-induced EGFR phosphorylation and internalisation. (4) Conclusion: This report confirms a transactivating effect of zinc on the EGFR for A549 cells and is the first describing an influence of zinc on the EGFR endocytosis. The transferability of the fine-tuning of EGFR-induced signalling by zinc needs to be verified in vivo, but the presented data underline that zinc might be helpful during treatment of disturbed regeneration and tissue repair.

Highlights

By supporting cell growth and wound healing processes, zinc is an essential trace element involved in the maintenance of cellular systems
(4) Conclusion: This report confirms a transactivating effect of zinc on the epidermal growth factor receptor (EGFR) for A549 cells and is the first describing an influence of zinc on the EGFR endocytosis
In addition to specific importers and exporters, the free intracellular zinc content is regulated by zinc binding proteins, from which a zinc release is mediated through the oxidation of zinc/thiolate-clusters [14]

Summary

Introduction

By supporting cell growth and wound healing processes, zinc is an essential trace element involved in the maintenance of cellular systems. Zinc exemplarily prevents apoptosis by protecting cells against oxidative stress and is further involved in proliferation and reepithelization by promoting the activation of growth factor receptors [1,2]. Previous studies paid particular attention to the epidermal growth factor receptor (EGFR/ErbB-1), which belongs to a family of receptor tyrosine kinases and is physiologically involved in the regulation of cell migration, proliferation, differentiation and apoptosis. Augmented EGFR signalling, due to receptor mutation, overexpression and transactivation, is though known to be associated with progression, invasion and metastasis of several cancer types [3]. Former studies indicate that zinc transactivates the EGFR; the mechanisms of receptor activation and the induced signalling effects by zinc vary strongly between different experimental settings and cell types [6,7,8,9,10,11]. Since the EGFR gained great importance in recent decades and the influence of zinc on its function has not yet been fully understood, examination continues to be reasonable and is of especial interest regarding pulmonal cells

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