Phospholipase C-ϵ Augments Epidermal Growth Factor-dependent Cell Growth by Inhibiting Epidermal Growth Factor Receptor Down-regulation

Sanguk Yun,Suhn-Kee Chae,Jang Hyun Choi,Pann-Ghill Suh,Kye Sook Yi,Sung Ho Ryu,Won-Pyo Hong

doi:10.1074/jbc.m704180200

Abstract

The down-regulation of the epidermal growth factor (EGF) receptor is critical for the termination of EGF-dependent signaling, and the dysregulation of this process can lead to oncogenesis. In the present study, we suggest a novel mechanism for the regulation of EGF receptor down-regulation by phospholipase C-epsilon. The overexpression of PLC-epsilon led to an increase in receptor recycling and decreased the down-regulation of the EGF receptor in COS-7 cells. Adaptor protein complex 2 (AP2) was identified as a novel binding protein that associates with the PLC-epsilon RA2 domain independently of Ras. The interaction of PLC-epsilon with AP2 was responsible for the suppression of EGF receptor down-regulation, since a perturbation in this interaction abolished this effect. Enhanced EGF receptor stability by PLC-epsilon led to the potentiation of EGF-dependent growth in COS-7 cells. Finally, the knockdown of PLC-epsilon in mouse embryo fibroblast cells elicited a severe defect in EGF-dependent growth. Our results indicated that PLC-epsilon could promote EGF-dependent cell growth by suppressing receptor down-regulation.

Highlights

Receptor tyrosine kinase signaling to avoid aberrant cellular stimulation
The Phospholipase C (PLC)-⑀-dependent up-regulation of the epidermal growth factor (EGF) receptor led to an increase in EGF-induced cell growth, which provided evidence that the novel mechanism was an involvement in the mitogenic role of PLC-⑀
The Interaction between PLC-⑀ and Adaptor protein complex 2 (AP2) Is Responsible for the Decreased EGF Receptor Down-regulation—We investigated whether the PLC-⑀-dependent suppression of EGF receptor down-regulation was the result of the binding between AP2 and PLC-⑀ (Fig. 5)

Summary

Introduction

Receptor tyrosine kinase signaling to avoid aberrant cellular stimulation. Ligand-induced activation of receptors leads to the recruitment of the endocytic machinery and subsequently to endosomal sorting, which can result in lysosomal degradation of the receptor or in the recycling of the receptor back to the cell surface [2]. AP2 plays an important role in the ligand-mediated downregulation of various receptors. It is a heterotetrameric complex (␣, ␤2, ␮2, and ␦2), and each subunit mediates various interactions. Phospholipase C (PLC) is activated by various growth factors or G protein-coupled receptor ligands and hydrolyzes phosphatidyl 4,5-bisphosphate into inositol 1,4,5-trisphosphate and diacylglycerol, which are implicated in calcium mobilization and protein kinase C activation, respectively [14]. PLC-⑀ contains a CDC25 homology domain at its amino terminus and a pair of RA domains at the carboxyl terminus (16 –18) These structural features suggest that PLC-⑀ is involved in the signaling promoted by the Ras superfamily GTPases. The PLC-⑀-dependent up-regulation of the EGF receptor led to an increase in EGF-induced cell growth, which provided evidence that the novel mechanism was an involvement in the mitogenic role of PLC-⑀

Methods

Results

Conclusion