PALS1 Specifies the Localization of Ezrin to the Apical Membrane of Gastric Parietal Cells

Xinwang Cao,Xia Ding,Zhen Guo,Rihong Zhou,Fengsong Wang,Fei Long,Fang Wu,Feng Bi,Qichen Wang,Daiming Fan,John G Forte,Maikun Teng,Xuebiao Yao

doi:10.1074/jbc.m411941200

Abstract

The ERM (ezrin/radixin/moesin) proteins provide a regulated linkage between membrane proteins and the cortical cytoskeleton and also participate in signal transduction pathways. Ezrin is localized to the apical membrane of parietal cells and couples the protein kinase A activation cascade to regulated HCl secretion in gastric parietal cells. Here, we show that the integrity of ezrin is essential for parietal cell activation and provide the first evidence that ezrin interacts with PALS1, an evolutionarily conserved PDZ and SH3 domain-containing protein. Our biochemical study verifies that ezrin binds to PALS1 via its N terminus and is co-localized with PALS1 to the apical membrane of gastric parietal cells. Furthermore, our study shows that PALS1 is essential for the apical localization of ezrin, as either suppression of PALS1 protein accumulation or deletion of the PALS1-binding domain of ezrin eliminated the apical localization of ezrin. Finally, our study demonstrates the essential role of ezrin-PALS1 interaction in the apical membrane remodeling associated with parietal cell secretion. Taken together, these results define a novel molecular mechanism linking ezrin to the conserved apical polarity complexes and their roles in polarized epithelial secretion of gastric parietal cells.

Highlights

The ERM proteins provide a regulated linkage between membrane proteins and the cortical cytoskeleton and participate in signal transduction pathways
Our study shows that PALS1 is essential for the apical localization of ezrin, as either suppression of PALS1 protein accumulation or deletion of the PALS1-binding domain of ezrin eliminated the apical localization of ezrin
Ezrin binds to PALS1 via its N-terminal 50 amino acids and is co-localized with PALS1 to the apical membrane of gastric parietal cells

Summary

Introduction

The ERM (ezrin/radixin/moesin) proteins provide a regulated linkage between membrane proteins and the cortical cytoskeleton and participate in signal transduction pathways. We show that the integrity of ezrin is essential for parietal cell activation and provide the first evidence that ezrin interacts with PALS1, an evolutionarily conserved PDZ and SH3 domain-containing protein. Our study demonstrates the essential role of ezrin-PALS1 interaction in the apical membrane remodeling associated with parietal cell secretion. Taken together, these results define a novel molecular mechanism linking ezrin to the conserved apical polarity complexes and their roles in polarized epithelial secretion of gastric parietal cells. To delineate the membrane-cytoskeleton linking role of ezrin, several groups have tried to identify ERM-binding proteins using pull-down assays These include identification of hyaluronate receptor CD44 [11], ICAM (intercellular adhesion molecule-1) [12], and EBP50 [13].

Methods

Results

Conclusion