title: Single molecule study of heterotypic interactions between mucins possessing the Tn cancer antigen.
abstract: Mucins are linear, heavily O-glycosylated proteins with physiological roles that include cell signaling, cell adhesion, inflammation, immune response and tumorgenesis. Cancer-associated mucins often differ from normal mucins by presenting truncated carbohydrate chains. Characterization of the binding properties of mucins with truncated carbohydrate side chains could thus prove relevant for understanding their role in cancer mechanisms such as metastasis and recognition by the immune system. In this work, heterotypic interactions of model mucins that possess the Tn (GalNAcαThr/Ser) and T (Galβ1-3GalNAcαThr/Ser) cancer antigens derived from porcine submaxillary mucin (PSM) were studied using atomic force microscopy. PSM possessing only the Tn antigen (Tn-PSM) was found to bind to PSM analogs possessing a combination of T, Tn and STn antigens as well as biosynthetic analogs of the core 1 blood group A tetrasaccharide (GalNAcα1-3[Fucα1-2] Galβ1-3GalNAcαSer/Thr). The rupture forces for the heterotypic interactions ranged from 18- to 31 pN at a force-loading rate of ∼0.5 nN/s. The thermally averaged distance from the bound complex to the transition state (xβ) was estimated to be in the range 0.37-0.87 nm for the first barrier of the Bell Evans analysis and within 0.34-0.64 nm based on a lifetime analysis. These findings reveal that the binding strength and energy landscape for heterotypic interactions of Tn-PSM with the above mucins, resemble homotypic interactions of Tn-PSM. This suggests common carbohydrate epitope interactions for the Tn cancer antigen with the above mucin analogs, a finding that may be important to the role of the Tn antigen in cancer cells.
authors.affiliation: Department of Physics, Biophysics and Medical Technology, The Norwegian University of Science and Technology, Trondheim NO-7491, Norway.
authors.forename: Kristin E
authors.initials: KE
authors.lastname: Haugstad
authors.affiliation: Department of Physics, Biophysics and Medical Technology, The Norwegian University of Science and Technology, Trondheim NO-7491, Norway.
authors.forename: Bjørn T
authors.initials: BT
authors.lastname: Stokke
authors.affiliation: Department of Molecular Pharmacology Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
authors.forename: C Fred
authors.initials: CF
authors.lastname: Brewer
authors.affiliation: W.A. Bernbaum Center for Cystic Fibrosis Research, Departments of Pediatrics, Biochemistry and Chemistry, Case Western Reserve University School of Medicine, Cleveland, OH 44106-4948, USA.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Gerken
authors.affiliation: Department of Physics, Biophysics and Medical Technology, The Norwegian University of Science and Technology, Trondheim NO-7491, Norway marit.sletmoen@ntnu.no.
authors.forename: Marit
authors.initials: M
authors.lastname: Sletmoen
mesh_terms: D000818:Animals; D015295:Antigens, Tumor-Associated, Carbohydrate / Q000737:chemistry / Q000378:metabolism*; D009077:Mucins / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D013552:Swine
chemical_list: D015295:Antigens, Tumor-Associated, Carbohydrate; D009077:Mucins; C040286:Tn antigen
keywords: AFM; STn-antigen; Tn-antigen; carbohydrate; dynamic force spectroscopy; glycan; interactions