This
brief survey focuses on the comparison of sialylated N-glycans of embryonic
stem cells (ESCs), induced pluripotent stem cells (iPSCs), mesenchymal stem
cells (MSCs) and of differentiated cells. In addition, the impact of sialic
acid (Sia) deficiency on cell surfaces during development is summarized. The
most common Sia is N-acetylneuraminic acid (Neu5Ac). The branched structures of
complex- and hybrid- type N-glycans are the carrier for Sia. Transmembrane
adhesive proteins, voltage-gated ion channels and many ligand-activated
receptors are some examples of heavily sialylated N-glycan bearing membrane
proteins. Their oligosaccharide extensions provide an important contribution to
glycocalyx glycans. ESCs and iPSCs are characterized with high mannose-type and
biantennary complex-type core structures. Two branches terminate with α2,6-
linked Sia. MSCs contain high mannose, hybrid- and complex- type N-glycans.
Linear poly-N-acetyllactosamine (poly-Galβ1-4GlcNAc, poly-LacNAc) chains are
the characteristic structures. Both α2,3- and α2,6- linked Sias are seen in a
species-specific manner in MSCs. α2,6- linked Sia is probably a marker
associated with the multipotency of human MSCs. Differentiated healthy cells
contain the most abundant 2-branched complex structures. The bisecting branch
on the core structure appears as a differentiation marker. poly-LacNAc chains
are terminated with α2,3- and α2,6- linked Sia, with the former being higher.
poly-LacNAc sequences have a high affinity for β-galactoside recognizing lectin
and galectin. Galectin forms a lattice structure with the N-glycans of
glycoproteins anchored to the plasma membrane. The impact of N-glycan-galectin
complexes in cell biology is summarized. Finally, the effect of reduced Sia on
clearance of aged cells is explained. Experimental evidence for the masking
role of Sia in the regulation of histolysis in aged cells is revealed.
Sialic acid sialylated N-glycan carriers embryonic stem cell mesenchymal stem cell differentiated cell sia deficiency galectin lattice
Journal Section | Review |
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Authors | |
Publication Date | December 27, 2017 |
Submission Date | January 13, 2018 |
Published in Issue | Year 2017 |