Heparan sulfate proteoglycans (HSPGs) and chondroitin sulfate proteoglycans (CSPGs) function as endocytic receptors for an internalizing anti-nucleic acid antibody

Abstract

A subset of monoclonal anti-DNA autoantibodies enters a variety of living cells. Here, we aimed to identify the endocytic receptors recognized by an internalizing anti-nucleic acid autoantibody, the 3D8 single-chain variable fragment (scFv). We found that cell surface binding and internalization of 3D8 scFv were inhibited markedly in soluble heparan sulfate (HS)/chondroitin sulfate (CS)-deficient or -removed cells and in the presence of soluble HS and CS. 3D8 scFv colocalized intracellularly with either HS proteoglycans (HSPGs) or CSPGs in HeLa cells. 3D8 scFv was co-endocytosed and co-precipitated with representative individual HSPG and CSPG molecules: syndecan-2 (a transmembrane HSPG), glypican-3 (a glycosylphosphatidylinositol (GPI)-anchored HSPG); CD44 (a transmembrane CSPG); and brevican (a GPI-anchored CSPG). Collected data indicate that 3D8 scFv binds to the negatively charged sugar chains of both HSPGs and CSPGs and is then internalized along with these molecules, irrespective of how these proteoglycans are associated with the cell membrane. This is the first study to show that anti-DNA antibodies enter cells via both HSPGs and CSPGs simultaneously. The data may aid understanding of endocytic receptors that bind anti-DNA autoantibodies. The study also provides insight into potential cell membrane targets for macromolecular delivery.

Targeting of Mammalian Glycans Enhances Phage Predation in the Gastrointestinal Tract

“…Considering that heparanase III cleaves at the same regions where K5 lyase would bind and degrades suggests ES17-TFP is utilizing the same receptor. Indeed, the addition of heparanse III, from the soil bacteria Flavobacterium heparinum, which specifically cleaves unmodified (unsulfated) NAc domains (GlcNAc-GlcUA) and NA/NS domains (GlcNS (N-Sulfo-D-Glucosamine) and GlcNAc) of HS, leads to abrogated phage ES17 binding to cells, meaning ES17 was highly specific for this type of glycan (Murphy et al, 2004;Park et al, 2017). Structurally similar mucins to heparan sulfate (Class III type, a-linked GlcNAc) suggest that this protein may also target these intestinal mucins (Ota et al, 1998;Fujita et al, 2011).…”

An E. coli-produced single-chain variable fragment (scFv) targeting hepatitis B virus surface protein potently inhibited virion secretion

“…Many scFvs have been reported to be able to penetrate into tissues and cells (Ha et al, 2014;Monnier et al, 2013;Park et al, 2017;Rudnick and Adams, 2009;Safdari et al, 2016). For subsequent studies on a potential intracellular antiviral activity of G12-scFv, we first investigated internalization of G12-scFv and VRC01-scFv in the stably HBV producing hepatoma cell line 2.2.15 by LCM.…”

Phagocyte Transcriptomic Analysis Reveals Focal Adhesion Kinase (FAK) and Heparan Sulfate Proteoglycans (HSPGs) as Major Regulators in Anti-bacterial Defense of Crassostrea hongkongensis

“…Heparan sulfate proteoglycans are a family of typical proteoglycans with one or more covalently attached heparan sulfate (HS) chains (66,67). Substantial studies show that HSPGs can act as versatile regulators in diverse signaling pathways, including Wnt, Hedgehog, and transforming growth factor β, thus impacting cell functions in development, cell migration, and autophagy (68)(69)(70). Moreover, HSPGs have been found to operate as cell surface receptors to mediate endocytosis…”