Gamma secretase dependent release of the CD44 cytoplasmic tail upregulates IFI16 in cd44-/- tumor cells, MEFs and macrophages.

Kristin Schultz,Peter Herrlich,Kerstin Minnich,Marcus Gereke,Christina Grieger (Lindner),Antonio Sechi,Yong Li,Anne Ruschel,Dunja Bruder,Pavel Urbánek

doi:10.1371/journal.pone.0207358

Abstract

The adhesion molecule and co-receptor of receptor tyrosine kinases, CD44, is expressed in all cells of the immune system, but also in numerous non-immune cells. CD44 plays roles in the cellular response to different pathogens. The molecular actions of CD44 during these processes are by and large still unknown. The CD44 molecule undergoes a sequential proteolytic cleavage which leads to the release of a soluble intracellular domain (CD44-ICD). Previous reports had shown that the CD44-ICD is taken up into the nucleus where it enhances transcription of specific target genes. By RNA profiling we identified a CD44-dependent transcriptional increase of interferon-responsive genes, among them IFI16. IFI16 is important in the innate immune response. It senses and binds pathogenic DNA and, together with cGAS, activates the cGAS-cGAMP-STING pathway and induces the expression of genes relevant for the response, e.g. IFN-β. Our results show that the enhancement of IFI16 expression depended on CD44 cleavage. A CD44-negative tumor cell line, embryonic fibroblasts and bone marrow-derived macrophages from cd44-/- mice were reduced in their response to IFN-γ, to viral DNA fragments and to Listeria monocytogenes infection. We could rescue the deficiency of CD44 negative RPM-MC cells and cd44-/- MEFs by expressing only the soluble CD44-ICD in the absence of any other CD44 domain. Expression of the CD44-ICD carrying a mutation that prevented the uptake into the nucleus, could not rescue the absence of CD44. This molecular aspect of regulation by CD44 may explain part of the immune phenotypes of mice with cd44 gene disruption.

Highlights

The transmembrane glycoprotein isoforms designated CD44 are encoded by a single gene whose transcript is subject to alternative splicing
A CD44-negative tumor cell line, embryonic fibroblasts and bone marrow-derived macrophages from cd44-/- mice were reduced in their response to IFN-γ, to viral DNA fragments and to Listeria monocytogenes infection
The diversity of the organismic reactions to infection is likely due to molecular CD44 actions specific for cell type, to different immune cells and other cell types involved in the responses, and to the interactions between different and multiple cell types during an immune response

Summary

Introduction

The transmembrane glycoprotein isoforms designated CD44 (cluster of differentiation 44) are encoded by a single gene whose transcript is subject to alternative splicing. Like many other membrane proteins CD44 is subjected to regulated ectodomain shedding by a metalloprotease (in case of CD44 by ADAM10; [1,2,3,4]) and subsequent release of the intracellular domain (CD44-ICD) by γ-secretase [4,5,6] (see Fig 1). The diversity of the organismic reactions to infection is likely due to molecular CD44 actions specific for cell type (and perhaps different CD44 isoforms), to different immune cells and other cell types involved in the responses, and to the interactions between different and multiple cell types (all possibly affected by deletion of CD44) during an immune response

Methods

Results

Conclusion