Epithelial-mesenchymal transition, IP3 receptors and ER-PM junctions: translocation of Ca2+ signalling complexes and regulation of migration.

Emmanuel Okeke,Muhammad Awais,Robert Sutton,Svetlana Voronina,Jordi Molgó,Matthew Concannon,Alex E Knight,Alexei V Tepikin,Lee Haynes,Tony Parker,Malcolm Begg,Daniel Metcalf,Hayley Dingsdale

doi:10.1042/bj20150364

Abstract

Disconnection of a cell from its epithelial neighbours and the formation of a mesenchymal phenotype are associated with profound changes in the distribution of cellular components and the formation of new cellular polarity. We observed a dramatic redistribution of inositol trisphosphate receptors (IP3Rs) and stromal interaction molecule 1 (STIM1)-competent endoplasmic reticulum-plasma membrane junctions (ER-PM junctions) when pancreatic ductal adenocarcinoma (PDAC) cells disconnect from their neighbours and undergo individual migration. In cellular monolayers IP3Rs are juxtaposed with tight junctions. When individual cells migrate away from their neighbours IP3Rs preferentially accumulate at the leading edge where they surround focal adhesions. Uncaging of inositol trisphosphate (IP3) resulted in prominent accumulation of paxillin in focal adhesions, highlighting important functional implications of the observed novel structural relationships. ER-PM junctions and STIM1 proteins also migrate to the leading edge and position closely behind the IP3Rs, creating a stratified distribution of Ca(2+) signalling complexes in this region. Importantly, migration of PDAC cells was strongly suppressed by selective inhibition of IP3Rs and store-operated Ca(2+) entry (SOCE), indicating that these mechanisms are functionally required for migration.

Highlights

Pancreatic ductal adenocarcinoma (PDAC) is a leading cause of cancer-related death [1]
store-operated Ca2+ entry (SOCE) is a Ca2+ influx mechanism triggered by Ca2+ store depletion, which involves the oligomerization of stromal interaction molecule 1 (STIM1, an EF-hand-containing protein that serves as the endoplasmic reticulum (ER) Ca2+ sensor), translocation of STIM1 oligomers to ER–plasma membrane (PM) junctions and opening of PM Ca2+
inositol trisphosphate receptor (IP3R) translocate from cell–cell contacts in cellular clusters to the leading edge of individual migrating cancer cells

Summary

INTRODUCTION

Pancreatic ductal adenocarcinoma (PDAC) is a leading cause of cancer-related death [1]. Understanding the fundamental contributions that Ca2+ signalling makes to cell migration is an important research avenue of potential clinical relevance [5,6,7] It is relevant for identifying putative therapeutic targets that could delay or prevent the formation of metastases (reviewed in [8]). SOCE is a Ca2+ influx mechanism triggered by Ca2+ store depletion, which involves the oligomerization of stromal interaction molecule 1 (STIM1, an EF-hand-containing protein that serves as the ER Ca2+ sensor), translocation of STIM1 oligomers to ER–PM junctions and opening of PM Ca2+. Following [Ca2+ ]ER depletion, Orai proteins translocate to the PM component of the ER–PM junctions where they interact with STIM and form Ca2+ -selective channels.

Okeke and others

MATERIALS AND METHODS

RESULTS AND DISCUSSION