Calorimetric Analysis of the Interplay between Synthetic Tn Antigen-Presenting MUC1 Glycopeptides and Human Macrophage Galactose-Type Lectin

Biochemistry. 2021 Feb 23;60(7):547-558. doi: 10.1021/acs.biochem.0c00942. Epub 2021 Feb 9.

Abstract

Human macrophage galactose-type lectin (hMGL, HML, CD301, CLEC10A), a C-type lectin expressed by dendritic cells and macrophages, is a receptor for N-acetylgalactosamine α-linked to serine/threonine residues (Tn antigen, CD175) and its α2,6-sialylated derivative (sTn, CD175s). Because these two epitopes are among malignant cell glycan displays, particularly when presented by mucin-1 (MUC1), assessing the influence of the site and frequency of glycosylation on lectin recognition will identify determinants governing this interplay. Thus, chemical synthesis of the tandem-repeat O-glycan acceptor region of MUC1 and site-specific threonine glycosylation in all permutations were carried out. Isothermal titration calorimetry (ITC) analysis of the binding of hMGL to this library of MUC1 glycopeptides revealed an enthalpy-driven process and an affinity enhancement of an order of magnitude with an increasing glycan count from 6-8 μM for monoglycosylated peptides to 0.6 μM for triglycosylated peptide. ITC measurements performed in D2O permitted further exploration of the solvation dynamics during binding. A shift in enthalpy-entropy compensation and contact position-specific effects with the likely involvement of the peptide surroundings were detected. KinITC analysis revealed a prolonged lifetime of the lectin-glycan complex with increasing glycan valency and with a change in the solvent to D2O.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Antigens, Tumor-Associated, Carbohydrate / chemistry
  • Antigens, Tumor-Associated, Carbohydrate / metabolism
  • Calorimetry / methods
  • Epitopes / metabolism
  • Galactose
  • Glycopeptides / chemistry
  • Glycopeptides / metabolism
  • Glycosylation
  • Humans
  • Lectins, C-Type / chemistry*
  • Lectins, C-Type / metabolism
  • Macrophages / metabolism
  • Mucin-1 / chemistry*
  • Mucin-1 / metabolism
  • Protein Binding

Substances

  • Antigens, Tumor-Associated, Carbohydrate
  • Epitopes
  • Glycopeptides
  • Lectins, C-Type
  • MGL lectin, human
  • MUC1 protein, human
  • Mucin-1
  • Tn antigen
  • sialosyl-Tn antigen
  • Galactose