Abstract
Keratan sulfate (KS) is a carbohydrate side chain covalently attached to extracellular proteoglycans. KS is composed of disaccharide units of 6-sulfated N-acetylglucosamine (GlcNAc) and galactose. We have previously shown that GlcNAc-6-O-sulfotransferase (GlcNAc6ST) 1 encoded by Chst2 is an enzyme necessary for the synthesis of GlcNAc-6-sulfated KS chains that are required for neuronal plasticity in the visual cortex of the mouse brain during the critical period, but not in adulthood. Here, we show that GlcNAc-6-sulfated KS recognized by the R-10G anti-KS antibody, of which the minimum epitope structure is Galß1-4GlcNAc(6S)ß1-3Galß1-4GlcNAc(6S), distributes diffusely in neuropils and presents densely in close proximity to the perineuronal region of the perineuronal net (PNN)-positive neurons in the adult visual cortex. Surprisingly, GlcNAc6ST3, which was discovered as an intestinal GlcNAc6ST encoded by Chst5, is a major brain KS sulfotransferase expressed in oligodendrocytes in adulthood. Moreover, we identified an isoform of the protein-tyrosine phosphatase PTPRZ as a R-10G-reactive KS proteoglycan. These results indicate that GlcNAc6ST3 may play a role in synthesis of a component of PNN in the adult brain, and that the KS-modified isoform of PTPRZ encoded by Ptprz1 could be an extracellular molecule associated with PNNs.
Highlights
Extracellular matrix molecules, such as chondroitin sulfate proteoglycans (CSPGs) and tenascins, interact with each other to fill the extracellular spaces and interpose among neurons and glia in the brain[1,2,3,4]
We found that disruption of GlcNAc6ST3, an intestinal enzyme, eliminated almost all GlcNAc-6-sulfated Keratan sulfate (KS) recognized by the R-10G anti-KS antibody in the adult brain, and that GlcNAc6ST3 was selectively expressed in oligodendrocyte precursor cells (OPCs) and the newly formed oligodendrocytes in the adult brain
The R-10G-positive KS-modified phosphacan/ phosphatase receptor type Z (PTPRZ) exists diffusely within neuropils and densely in close proximity to perineuronal regions of a subset of perineuronal net (PNN)-positive neurons in the adult brain cerebral cortex. These results indicate that GlcNAc6ST3 in oligodendrocytes is a major KS enzyme in the adult brain, and that GlcNAc6ST3 may play a role in synthesis of a PNN component, and the KS-modified isoform of PTPRZ could be associated with PNNs
Summary
The R-10G-reactive GlcNAc-6-sulfate KS is born on a CSPG in the adult mouse brain. We previously showed that no or minimal expression of KS epitopes recognized by the 5D4 antibody was observed in the adult mouse brain[23], while GlcNAc-6-monosulfated KS, which is recognized by the R-10G antibody, was expressed at the level comparable to that in the critical period brain[12]. Confocal microscopy analysis showed that some of the pericellular R-10G signals exist densely in close proximity to perineuronal regions (Figs 2c and S2) These results strongly indicate that R-10G reactive KS/CSPGs are accumulated in a subset of inhibitory intercortical neurons in the adult brain cortex with the preferential localization in the visual cortex. Expression of the GlcNAc6ST4 gene, Chst[7], was observed in astrocytes, OPCs, microglia, and endothelial cells in the brain (Fig. 3c) These results indicate that the major source of the R-10G-reactive KS/CSPG in neuropils and in the vicinity of the subsets of PV-positive and WFA-positive neurons is oligodendrocytes in the adult brain. Possible involvement of the oligodendrocyte-derived GlcNAc6ST3, R-10G-positive KS phosphacan and the ectodomain of PTPRZ-FL in neuronal plasticity in the adult brain can be a subject of further study employing cell-type specific deletions of Ptprz[1] in GlcNAc6ST3-KO mice. To the formation of PNNs and differentiation of PV-positive neurons through secretion of the R-10G-positive KS phosphacan and the ectopic domain of PTPRZ-FL will be investigated in the future
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
