LSECtin interacts with filovirus glycoproteins and the spike protein of SARS coronavirus

Abstract

Cellular attachment factors like the C-type lectins DC-SIGN and DC-SIGNR (collectively referred to as DC-SIGN/R) can augment viral infection and might promote viral dissemination in and between hosts. The lectin LSECtin is encoded in the same chromosomal locus as DC-SIGN/R and is coexpressed with DC-SIGNR on sinusoidal endothelial cells in liver and lymphnodes. Here, we show that LSECtin enhances infection driven by filovirus glycoproteins (GP) and the S protein of SARS coronavirus, but does not interact with human immunodeficiency virus type-1 and hepatitis C virus envelope proteins. Ligand binding to LSECtin was inhibited by EGTA but not by mannan, suggesting that LSECtin unlike DC-SIGN/R does not recognize high-mannose glycans on viral GPs. Finally, we demonstrate that LSECtin is N-linked glycosylated and that glycosylation is required for cell surface expression. In summary, we identified LSECtin as an attachment factor that in conjunction with DC-SIGNR might concentrate viral pathogens in liver and lymph nodes.

The pathogen receptor liver and lymph node sinusoidal endotelial cell C-type lectin is expressed in human Kupffer cells and regulated by PU.1

“…Monocytes were purified from peripheral blood mononuclear cells via magnetic cell sorting using CD14 microbeads (Miltenyi Biotech, Bergisch Gladbach, Germany), and monocyte-derived dendritic cells (MDDCs) were generated as described. 5,6 The K562 (chronic myelogenous leukemia) and THP-1 (monocytic leukemia) cell lines were cultured in Roswell Park Memorial Institute 1640 medium supplemented with 10% fetal bovine serum, 25 mM 4-(2-hydroxyethyl)-1-piperazine ethanesulfonic acid, and 2 mM glutamine (complete medium), at 37°C in a humidified atmosphere with 5% CO 2 . MUTZ-3 cells [23][24][25] were maintained in complete medium supplemented with granulocyte-macrophage colony-stimulating factor (10 ng/mL) and their dendritic differentiation was induced in the presence of 1,000 U/mL interleukin-4 (IL-4) for 5 days.…”

“…EnVisionTM G/2 Doublestain System (Dako) was used for the simultaneous detection of CD68 and LSECtin, following the manufacturer's recommendations with a mouse monoclonal antibody against CD68 (PG-M1; Dako) and the LSECtin-specific polyclonal antisera ADS1 (against the stalk domain) and ADS4 (against the whole extracellular region). 5,6 Blockade of endogenous peroxidase and alkaline phosphatase activities was accomplished with 0.5% H 2 O 2 and enzymatic inhibitors (Dako). After addition of the anti-CD68 antibody (1/100 dilution) for 30 minutes, tissue was incubated with dextran polymerconjugated horseradish peroxidase-labeled antisera against murine and rabbit immunoglobulins, and CD68-specific staining detected with 3,3'-diaminobenzidine.…”

“…DC-SIGN, L-SIGN, and LSECtin function as endocytic receptors and mediate binding and internalization of clinically relevant viral, bacterial, and fungal pathogens. 5,6 CD23 is expressed on myeloid cells and activated B lymphocytes, where it functions as a low affinity receptor for immunoglobulin E and plays a role in limiting the extent of immunoglobulin E-mediated pathologies. 7,8 DC-SIGN is expressed on myeloid dendritic cells (DCs), 1,9 alternatively activated in vitro macrophages, 10 interstitial DCs, 11 a subset of CD14ϩ peripheral blood DCs, 12 and macrophages from various tissues, [13][14][15] whereas L-SIGN is exclusively expressed on endothelial cells of the liver, lymph nodes, and placenta.…”

Conserved Receptor-binding Domains of Lake Victoria Marburgvirus and Zaire Ebolavirus Bind a Common Receptor

“…However, the C-type lectin asialoglycoprotein receptor (27,28), DC-SIGN (29,30), hMGL (31), L-SIGN (29,30), and LSECtin (32), as well as other molecules, including folate receptor-␣ (33) and ␤1 integrins (15), have been shown or suggested to enhance filovirus cell entry. Subtle differences between marburgvirus and ebolavirus infection efficiencies in different cell lines or following glycosidase or protease treatment have led to the suggestion that these viruses utilize distinct receptors or entry mechanisms (5).…”

Significant Redox Insensitivity of the Functions of the SARS-CoV Spike Glycoprotein

“…It is made up of S1 and S2 subdomains (2,3). The S1 region interacts with angiotensin-converting enzyme 2 (ACE2), the primary cellular receptor (9 -12), L-SIGN (13), and L-SECtin (14), whereas S2 mediates membrane fusion (2,3). Here, we investigated the functional role of the 20 conserved cysteine residues of mature S1.…”