Interactions between the breast cancer-associated MUC1 mucins and C-type lectin characterized by optical tweezers

Abstract

Carbohydrate–protein interactions govern many crucial processes in biological systems including cell recognition events. We have used the sensitive force probe optical tweezers to quantify the interactions occurring between MGL lectins and MUC1 carrying the cancer-associated glycan antigens mucins Tn and STn. Unbinding forces of 7.6±1.1 pN and 7.1±1.1 pN were determined for the MUC1(Tn)—MGL and MUC1(STn)—MGL interactions, at a force loading rate of ~40 pN/s. The interaction strength increased with increasing force loading rate, to 27.1±4.4 and 36.9±3.6 pN at a force loading rate of ~ 310 pN/s. No interactions were detected between MGL and MUC1(ST), a glycoform of MUC1 also expressed by breast carcinoma cells. Interestingly, this glycan (ST) can be found on proteins expressed by normal cells, although in this case not on MUC1. Additionally, GalNAc decorated polyethylene glycol displayed similar rupture forces as observed for MUC1(Tn) and MUC1(STn) when forced to unbind from MGL, indicating that GalNAc is an essential group in these interactions. Since the STn glycan decoration is more frequently found on the surface of carcinomas than the Tn glycan, the binding of MUC1 carrying STn to MGL may be more physiologically relevant and may be in part responsible for some of the characteristics of STn expressing tumours.

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

“…In this context, upon examination of a member of another class of C-type lectins, association rate constants in the range of 10 5 –10 6 M –1 s –1 have been reported for selectin binding to in vivo ligands, i.e., L-selectin to P-selectin glycoprotein ligand-1 (PSGL-1, CD162) . Also of interest for comparison, the dissociation rate k off of 0.060 s –1 for the MUC1-Thr16 glycopeptide–hMGL complex is similar to k off values obtained for binding using optical tweezers and indicates a longer lifetime (τ = 1.67 s) in comparison to those of Gal N Ac and the two other monoglycosylated peptides. In our experimental series, the triglycosylated MUC1 peptide ( 13 ) exhibited the lowest dissociation rate ( k off = 0.019 s –1 ) and the longest lifetime of all complexes (τ = 52.63 s) (Table ).…”

Lectin nanoparticle assays for detecting breast cancer-associated glycovariants of cancer antigen 15-3 (CA15-3) in human plasma

“…Those lectins were WGA and recombinant human MGL. WGA and MGL recognize the GlcNAc and GalNAc -containing epitopes respectively, frequently expressed on the surface of cancer cells [36–38]. Using CA15-3 WGA and CA15-3 MGL assays, in the plasma of metastatic BC patients are likely to serve as more cancer-specific than the conventional assay.…”

The applications of the optical tweezer and atomic force microscope at the molecular level

“…Optical tweezers can determine forces that are in range 0.5 to 100 pN and are able to act as probes to quantify such molecules as carbohydrate-protein and carbohydrate-carbohydrate, which have lower strengths of these interactions [8] , thus characterizing the mucins that carry cancer antigens in order to determine the carbohydrate component of these interaction mechanisms in a manner that allows for the analysis and diagnosis of cancer [9] .…”