Endocytic function is critical for influenza A virus infection via DC-SIGN and L-SIGN.

Leah Gillespie,Sarah L Londrigan,Andrew G Brooks,Wy Ching Ng,Patrick C Reading,Paula Roosendahl

doi:10.1038/srep19428

Abstract

The ubiquitous presence of cell-surface sialic acid (SIA) has complicated efforts to identify specific transmembrane glycoproteins that function as bone fide entry receptors for influenza A virus (IAV) infection. The C-type lectin receptors (CLRs) DC-SIGN (CD209) and L-SIGN (CD209L) enhance IAV infection however it is not known if they act as attachment factors, passing virions to other unknown receptors for virus entry, or as authentic entry receptors for CLR-mediated virus uptake and infection. Sialic acid-deficient Lec2 Chinese Hamster Ovary (CHO) cell lines were resistant to IAV infection whereas expression of DC-SIGN/L-SIGN restored susceptibility of Lec2 cells to pH- and dynamin-dependent infection. Moreover, Lec2 cells expressing endocytosis-defective DC-SIGN/L-SIGN retained capacity to bind IAV but showed reduced susceptibility to infection. These studies confirm that DC-SIGN and L-SIGN are authentic endocytic receptors for IAV entry and infection.

Highlights

While little is known regarding the specific entry receptors for influenza A virus (IAV) expressed by epithelial cells, significant progress has been made towards identifying receptors that play a role in infectious entry of IAV into macrophages (MΦ ) and dendritic cells (DC)
It is well established that DC-SIGN and L-SIGN are mannose-specific C-type lectin receptors (CLRs) that act as attachment factors and promote infection by a range of different viruses, including Ebola and Marburg viruses, dengue virus (DV), human immunodeficiency virus (HIV), hepatitis C virus (HCV) and phleboviruses
Cells expressing endocytosis-defective (LL) mutants of DC-SIGN were resistant to pH-dependent infection via arthropod-borne phleboviruses[24], confirming that DC-SIGN can act as an authentic receptor for viral attachment and endocytosis, leading to infectious entry

Summary

Introduction

While little is known regarding the specific entry receptors for IAV expressed by epithelial cells, significant progress has been made towards identifying receptors that play a role in infectious entry of IAV into macrophages (MΦ ) and dendritic cells (DC). DC-SIGN and L-SIGN are tetrameric type II transmembrane CLRs expressing Ca2+-dependent (C-type) carbohydrate recognition domains (CRD) which bind preferentially to mannose-rich oligosaccharides (reviewed in[10]). Recognition of IAV by DC-SIGN/L-SIGN may trigger direct receptor-mediated internalization, demonstrating their ability to act as bone fide entry receptors for IAV infection. We demonstrate that Lec[2] cells expressing DC-SIGN or L-SIGN with mutations (in which the dileucine motif (LL) was replaced by dialanine (AA)) or deletions (33 and 41 amino acids for DC-SIGN and L-SIGN, respectively) within the cytoplasmic tail bound IAV efficiently, but showed major defects in their ability to internalize monoclonal antibody (mAb) and virus, and in their susceptibility to IAV infection. Our studies confirm that both DC-SIGN and L-SIGN function as authentic receptors for IAV uptake and infection

Objectives

Methods

Results

Conclusion