A novel GTP-binding protein–adaptor protein complex responsible for export of Vangl2 from the trans Golgi network

Yusong Guo,Giulia Zanetti,Randy Schekman

doi:10.7554/elife.00160

Abstract

Planar cell polarity (PCP) requires the asymmetric sorting of distinct signaling receptors to distal and proximal surfaces of polarized epithelial cells. We have examined the transport of one PCP signaling protein, Vangl2, from the trans Golgi network (TGN) in mammalian cells. Using siRNA knockdown experiments, we find that the GTP-binding protein, Arfrp1, and the clathrin adaptor complex 1 (AP-1) are required for Vangl2 transport from the TGN. In contrast, TGN export of Frizzled 6, which localizes to the opposing epithelial surface from Vangl2, does not depend on Arfrp1 or AP-1. Mutagenesis studies identified a YYXXF sorting signal in the C-terminal cytosolic domain of Vangl2 that is required for Vangl2 traffic and interaction with the μ subunit of AP-1. We propose that Arfrp1 exposes a binding site on AP-1 that recognizes the Vangl2 sorting motif for capture into a transport vesicle destined for the proximal surface of a polarized epithelial cell.DOI:http://dx.doi.org/10.7554/eLife.00160.001.

Highlights

Planar cell polarity (PCP) governs the organization of epithelial cells along a plane parallel to the surface of the epithelium
These results suggest that Arfrp1 regulates the export of Vangl2 from the trans Golgi network (TGN)
GST-Arfrp1 and GST-μ1 bound HA-Vangl2 but not GFP-Frizzled-6 or GFP-Celsr1 in cell lysates from COS7 cells co-transfected with HA-Vangl2 and GFP-Celsr1 (Figure 7J) or co-transfected with HA-Vangl2 and GFP-Frizzled 6 (Figure 7K). These results suggest that sorting of Frizzled 6 and Celsr1 at the TGN is independent of the Arfrp1/adaptor complex 1 (AP-1) machinery

Summary

Introduction

Planar cell polarity (PCP) governs the organization of epithelial cells along a plane parallel to the surface of the epithelium. This long range order orchestrates proper development and organ function. A key feature of these signaling receptors is that they are asymmetrically localized on the cell boundaries during PCP signaling (Klein and Mlodzik, 2005). One hypothesis is that interactions between PCP signaling molecules across cell junctions could stabilize their polarized localization to opposing cell boundaries (Klein and Mlodzik, 2005; Chen et al, 2008). Additional evidence suggests that intracellular trafficking may contribute to the asymmetric localization of PCP signaling receptors (Shimada et al, 2006; Strutt and Strutt, 2008)

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