Integrin \u03b111 cytoplasmic tail is required for FAK activation to initiate 3D cell invasion and ERK-mediated cell proliferation

Pugazendhi Erusappan,Jahedul Alam,Cédric Zeltz,Donald Gullberg,Ning Lu

doi:10.1038/s41598-019-51689-6

Abstract

Integrin α11β1 is a collagen-binding integrin, which is receiving increasing attention in the context of wound healing and fibrosis. Although α11β1 integrin displays similar collagen specificity to α2β1 integrin, both integrins have distinct in vivo functions. In this context, the contribution of α11 subunit cytoplasmic tail interactions to diverse molecular signals and biological functions is largely unknown. In the current study, we have deleted the α11 cytoplasmic tail and studied the effect of this deletion on α11 integrin function. Compared to wild-type cells, C2C12 cells expressing tail-less α11 attached normally to collagen I, but formed fewer focal contacts. α11-tail-less cells furthermore displayed a reduced capacity to invade and reorganize a 3D collagen matrix and to proliferate. Analysis of cell signaling showed that FAK and ERK phosphorylation was reduced in cells expressing tail-less α11. Inhibition of ERK and FAK activation decreased α11-mediated cell proliferation, whereas α11-mediated cell invasion was FAK-dependent and occurred independently of ERK signaling. In summary, our data demonstrate that the integrin α11 cytoplasmic tail plays a central role in α11 integrin-specific functions, including FAK-dependent ERK activation to promote cell proliferation.

Highlights

Integrins are heterodimeric cell surface receptors composed of non-covalently associated α and β subunits, which act as cell surface links to the extracellular matrix (ECM) and to other cells in dynamic cell-cell linkages[1]
In order to identify the role of the α11 cytoplasmic tail, a mutant variant (Huα11-1171) with a deletion of the terminal 17 amino acids in the cytoplasmic tail of human integrin α11 (Huα11) was generated
Horwitz et al pioneered this strategy for integrin α5 and the resultant tagged α5 integrin was characterized in detail without any evidence of artifacts due to the enhanced green fluorescence protein (EGFP) tag[27]

Summary

Introduction

Integrins are heterodimeric cell surface receptors composed of non-covalently associated α and β subunits, which act as cell surface links to the extracellular matrix (ECM) and to other cells in dynamic cell-cell linkages[1]. The NPXY motifs located in the β subunits are important binding sites for talins and kindlins, both taking part in integrin inside-out signaling[8,9] These important interactions in turn are regulated through binding of other proteins such as Dok[1] and ICAP-1, to the same integrin β chain. In chimeric experiments where again the α2 cytoplasmic tail was replaced with the tail of other integrins, it was demonstrated that chimeric α2 integrins with α5-tail (Xα2 Cα5) could mediate collagen gel contraction, whereas chimeric Xα2 Cα4 failed to mediate contraction, but instead promoted cell migration[24] Already at this time it was speculated that “α subunit cytoplasmic domains, probably acting in concert with their associated β subunit, have important but distinct roles and perhaps eventually will be shown to interact with distinct set of intracellular proteins”[24]. Our data show that the integrin α11 cytoplasmic tail is dispensable for cell attachment but is essential for focal adhesion formation, ERK-dependent cell proliferation, cell migration and reorganization of 3D collagen matrices

Methods

Results

Conclusion