Compositional and topological determinants of a physiological Ashwell-Morell receptor ligand

• 成果类型: Article
• 署名作者: Hintze, John; Fraumeni, Robert; de Haan, Noortje; Miller, Rebecca L.; Saraswat, Mayank; Yang, Zhang; Clausen, Henrik; Marth, Jamey D.
• 署名单位: Sanford Burnham Prebys Medical Discovery Institute; University of Copenhagen; Leiden University; Leiden University Medical Center (LUMC); Leiden University - Excl LUMC
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-10135
• DOI: 10.1073/pnas.2427129122
• 发表日期: 2025-04-10
• 关键词: liver asialoglycoprotein receptor; intestinal alkaline-phosphatase; sialic-acid; binding-protein; mice lacking; glycoproteins; clearance; lectin; oligosaccharides; biantennary

摘要

The hepatocyte Ashwell-Morell receptor (AMR) is the prototypical mammalian lectin and the first cell receptor isolated. This recycling endocytic receptor of the plasma membrane determines the concentrations of hundreds of circulating glycoproteins the blood and plays important roles in host responses to and outcomes of infection. The compositional and topological determinants of a physiological AMR ligand have remained unclear with contradictory findings reported. Previous studies established that the AMR binds multivalent galactose on desialylated triantennary or higher-branched N-glycans with little to no binding to galactose on biantennary forms. However, the vast majority of circulating blood glycoproteins are modified by biantennary N-glycans, rendering them unlikely to be ligands bound and eliminated by the AMR. Separately, other studies reported that AMR ligands include sialylated N-glycans, and specifically c2-6, but not c2-3, sialic acid linkages. Herein, we investigated the composition and topology of AMR ligands using a known physiological AMR ligand, intestinal alkaline phosphatase (IAP). Recombinant active IAP was produced in glycoengineered cells with either biantennary or higher valency triantennary and tetra-antennary N-glycan structures, and further with and without either c2-6 or c2-3 sialic acid linkages. These closely homogenous IAP monomer glycoforms assemble as dimers with similar enzymatic activity and were compared in AMR binding and clearance assays. Our results indicate that the AMR does not significantly bind IAP when its N-glycans are predominantly sialylated with either c2-6 or c2-3 sialic acid linkages. Multivalent desialylated AMR ligands may, however, appear when IAP monomers dimerize, resulting in the close proximation of biantennary N-glycans.