Ligand-Occupied Integrin Internalization Links Nutrient Signaling to Invasive Migration

Elena Rainero,Jonathan D Howe,Patrick T Caswell,Nigel B Jamieson,Kurt Anderson,David R Critchley,Laura Machesky,Jim C Norman

doi:10.1016/j.celrep.2014.12.037

Abstract

Integrin trafficking is key to cell migration, but little is known about the spatiotemporal organization of integrin endocytosis. Here, we show that α5β1 integrin undergoes tensin-dependent centripetal movement from the cell periphery to populate adhesions located under the nucleus. From here, ligand-engaged α5β1 integrins are internalized under control of the Arf subfamily GTPase, Arf4, and are trafficked to nearby late endosomes/lysosomes. Suppression of centripetal movement or Arf4-dependent endocytosis disrupts flow of ligand-bound integrins to late endosomes/lysosomes and their degradation within this compartment. Arf4-dependent integrin internalization is required for proper lysosome positioning and for recruitment and activation of mTOR at this cellular subcompartment. Furthermore, nutrient depletion promotes subnuclear accumulation and endocytosis of ligand-engaged α5β1 integrins via inhibition of mTORC1. This two-way regulatory interaction between mTORC1 and integrin trafficking in combination with data describing a role for tensin in invasive cell migration indicate interesting links between nutrient signaling and metastasis.

Highlights

The cell’s major fibronectin-binding integrin (a5b1) promotes survival and migration of tumor cells (Caswell et al, 2008; Lee and Juliano, 2000), making this an important molecule for cell biologists interested in cancer progression. a5b1 integrin is continuously internalized, trafficked to recycling endosomes and returned, or recycled, to the plasma membrane via both Rab11- and Arf6-dependent pathways (Caswell and Norman, 2006; Pellinen and Ivaska, 2006)
Expression of mutant p53s promote association of Rab-coupling protein (RCP) with a5b1, which associates with receptor tyrosine kinases (RTKs) to promote invasion (Caswell et al, 2008; Muller et al, 2009, 2012)
Activated Integrins Are Endocytosed at Centrally Located Adhesions in Rab25-Expressing Cells We measured a5b1 endocytosis using capture-ELISA (Roberts et al, 2001) in the presence of the receptor recycling inhibitor, primaquine, to ensure that estimates of integrin endocytosis were not affected by recycling. a5b1 was rapidly internalized by A2780 ovarian cancer cells, and this was modestly enhanced by Rab25 expression, whereas endocytosis of transferrin receptor (TfnR) was unaffected (Figure 1A)

Summary

Introduction

The cell’s major fibronectin-binding integrin (a5b1) promotes survival and migration of tumor cells (Caswell et al, 2008; Lee and Juliano, 2000), making this an important molecule for cell biologists interested in cancer progression. a5b1 integrin is continuously internalized, trafficked to recycling endosomes and returned, or recycled, to the plasma membrane via both Rab11- and Arf6-dependent pathways (Caswell and Norman, 2006; Pellinen and Ivaska, 2006). A5b1 integrin is continuously internalized, trafficked to recycling endosomes and returned, or recycled, to the plasma membrane via both Rab11- and Arf6-dependent pathways (Caswell and Norman, 2006; Pellinen and Ivaska, 2006). A5b1 integrins that are ligand-engaged do not reach recycling endosomes but are sent to lysosomes under control of Rab (Dozynkiewicz et al, 2012; Lobert et al, 2010; Rainero and Norman, 2013). Rab expression is associated with upregulation of a lysosomal protein called CLIC3, which prevents degradation of a5b1 and allows recycling from this compartment to the plasma membrane (Dozynkiewicz et al, 2012). When a5b1 is trafficked to late endosomes and lysosomes, this is associated with invasion and metastasis, but via activation of c-Src (Dozynkiewicz et al, 2012; Lobert and Stenmark, 2012)

Results

Discussion

Conclusion