Dataset Information

Endocytosis by macrophages: Interplay of macrophage scavenger receptor-1 and LDL receptor-related protein-1

ABSTRACT: Multiple receptors may mediate the cellular uptake of a single protein and thereby affect the plasma level of the involved protein. In case of Von Willebrand Factor (VWF) these receptors include LDL receptor-related protein-1 (LRP-1), Macrophage scavenger receptor-1 (MSR-1, SR-AI or CD204), the Macrophage Galactose-type lectin (CLEC10A, MGL or CD301), Siglec-5 and the Asialoglycoprotein receptor (ASGPR).1 In the present study, we aimed to gain insight into the interplay of multiple receptors to the cellular internalization of a single ligand like VWF. The macrophages in the liver and spleen have been reported to contribute considerably to the cellular uptake of VWF. Previously, we have shown that also human monocyte-derived macrophages (MDMs) internalize VWF via a mechanism that depends on LRP-1.5 We now analyzed the cell surface proteome of MDMs using mass spectrometry analysis to identify putative other VWF clearance receptors on MDMs. We found that MDMs contain LRP-1 and MSR-1, and we identified 1 peptide that is shared by Siglec-5 and Siglec-14. The estimated copy numbers of these receptors revealed a markedly higher expression of LRP-1 and MSR-1 compared to Siglec-5/14. We therefore focused our study on the possible dual mechanism by which LRP-1 and MSR-1 may cooperate in the cellular uptake of VWF by MDMs and conducted a range of functional studies. Based on the data presented in this study, we propose the following model to explain the relationship between the two abundant VWF receptors on MDMs. Both LRP-1 and MSR-1 associate with regions in the D’D3A1 region of VWF, thereby initiating two endocytic pathways that are both regulated by LRP-1. The first pathway follows a direct association of the VWF A1 domain to LRP-1. In the second pathway, VWF interacts to MSR-1 via regions in the D’D3 assembly, which subsequently associates to LRP-1 for endocytosis.

INSTRUMENT(S): Orbitrap Fusion ETD

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Cell Culture, Endothelial Cell

SUBMITTER: Eelke Béguin

LAB HEAD: Alexander Benjamin Meijer

PROVIDER: PXD011490 | Pride | 2019-07-08

REPOSITORIES: Pride

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Publications

Endocytosis by macrophages: interplay of macrophage scavenger receptor-1 and LDL receptor-related protein-1.

Béguin Eelke P EP Przeradzka Małgorzata A MA Janssen Esmée F J EFJ Meems Henriët H Sedek Magdalena M van der Zwaan Carmen C Mertens Koen K van den Biggelaar Maartje M Meijer Alexander B AB Mourik Marjon J MJ

Haematologica 20190627 3

PMID: 31248969

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Project description:Siglec-E is a murine CD33-related siglec that functions as an inhibitory receptor and is expressed mainly on neutrophils and macrophage populations. Recent studies have suggested that siglec-E is an important negative regulator of LPS-TLR4 signalling and one report (Wu et al 2016) claimed that siglec-E is required for TLR4 endocytosis following uptake of Escherichia coli by macrophages and dendritic cells (DCs). Our attempts to reproduce these observations using cells from wildtype (WT) and siglec E deficient mice were unsuccessful. We used a variety of assays to determine if siglec-E expressed by different macrophage populations can regulate TLR-4 signalling in response to LPS, but found no consistent differences in cytokine secretion in vitro and in vivo, comparing 3 different strains of siglec-E-deficient mice with matched WT controls. No evidence was found that the siglec-E deficiency was compensated by expression of siglecs-F and –G, the other murine inhibitory CD33-related siglecs. Quantitative proteomics was used as an unbiased approach and provided additional evidence that siglec-E does not suppress inflammatory TLR4 signaling. Interestingly, proteomics revealed a siglec E dependent alteration in macrophage phenotype that could be relevant to functional responses in host defence. In support of this, siglec-E-deficient mice exhibited enhanced growth of Salmonella enterica serovar Typhimurium in the liver following intravenous infection, but macrophages lacking siglec-E did not show altered uptake or killing of bacteria in vitro. Using various cell types including bone marrow derived DCs (BMDC), splenic DCs and macrophages from WT and siglec-E-deficient mice, we showed that siglec-E is not required for TLR4 endocytosis following E.coli uptake or LPS challenge. We failed to see expression of siglec-E by BMDC even after LPS-induced maturation, but confirmed previous studies that splenic DCs express low levels of siglec-E. Taken together, our findings do not support a major role of siglec-E in regulation of TLR4 signalling functions or TLR4 endocytosis in macrophages or DCs. Instead, they reveal that induction of siglec-E by LPS can modulate the phenotype of macrophages, the functional significance of which is currently unclear.

Dataset Information

Endocytosis by macrophages: Interplay of macrophage scavenger receptor-1 and LDL receptor-related protein-1

Publications

Endocytosis by macrophages: interplay of macrophage scavenger receptor-1 and LDL receptor-related protein-1.

Similar Datasets

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