Search

Paucimannosidic glycans are restricted to the core structure [Man1–3GlcNAc2Fuc0–1] of N -glycans and are rarely found in mammalian tissues. Yet, especially [Man2-3GlcNAc2Fuc1] have been found significantly upregulated in tumors, including in colorectal and liver cancer. Mannitou IgM is a murine monoclonal antibody that was previously shown to recognize Man3GlcNAc2 with an almost exclusive selectivity. Here, we have sought the definition of the minimal glycan epitope of Mannitou IgM, initiated by screening on a newly designed paucimannosidic glycan microarray; among the best binders were Man3GlcNAc2 and its α1,6 core-fucosylated variant, Man3GlcNAc2Fuc1. Unexpectedly and in contrast to earlier findings, Man5GlcNAc2-type structures bind equally well and a large tolerance was observed for substitutions on the α1,6 arm. It was confirmed that any substitution on the single α1,3-linked mannose completely abolishes binding. Surface plasmon resonance for kinetic measurements of Mannitou IgM binding, either directly on the glycans or as presented on omega-1 and kappa-5 soluble egg antigens from the helminth parasite Schistosoma mansoni , showed submicromolar affinities. To characterize the epitope in greater and atomic detail, saturation transfer difference nuclear magnetic resonance spectroscopy was performed with the Mannitou antigen-binding fragment. The STD-NMR data demonstrated the strongest interactions with the aliphatic protons H1 and H2 of the α1–3-linked mannose and weaker imprints on its H3, H4 and H5 protons. In conclusion, Mannitou IgM binding requires a nonsubstituted α1,3-linked mannose branch of paucimannose also on proteins, making it a highly specific tool for the distinction of concurrent human tumor-associated carbohydrate antigens. [ABSTRACT FROM AUTHOR]

Protein glycosylation has received much attention due to its multiple functional roles in physiological and pathophysiological conditions. Paucimannose is a common mannosidic N-glycoepitope in invertebrates and plants but has only recently been detected in vertebrates. Herein, we demonstrate the presence of paucimannosidic epitopes specifically in early postnatal neural progenitor cells (NPCs) between postnatal day 0 and 7 in mouse brain suggesting a possible role in the development of NPCs. Paucimannosidic epitopes were also detected in human glioblastoma cells and human macrophages by immunofluorescence and mass spectrometric analysis. Its expression was significantly increased after proliferation arrest indicating its importance in the regulation of cell proliferation. This hypothesis was further strengthened by reduced cell proliferation after the application of paucimannose-reactive Mannitou antibody into culture medium of growing cells. Most interestingly, this reduction in cell proliferation upon the administration of Mannitou antibody could also be observed in vivo in the subventricular zone of early postnatal mouse brain. Taken together, these observations demonstrate that paucimannosylation directly influences cell proliferation in various vertebrate cell types including early postnatal neural stem cells. [ABSTRACT FROM AUTHOR]