Keratan sulfate-containing proteoglycans in sheep brain with particular reference to phosphacan and synaptic vesicle proteoglycan isoforms.

Proteoglycans (PGs) are widely expressed in all areas of the brain. In this study, the keratan sulfate-containing PGs (KS-PGs) from cerebrum (CB), cerebellum (CL) and brainstem (BS) of young sheep brain were isolated, purified and characterized. The amount of KS-PGs in CL was significantly lower than that in CB and BS. KS-PGs were characterized by increased extent of glycosylation and heterogeneity of KS chains in CL. Western blot analyses demonstrated the presence of the KS-PGs phosphacan, SV2A and SV2B isoforms of synaptic vesicle proteoglycan in all three areas of the young sheep brain. Phosphacan predominated in BS and CB, showing significant molecular heterogeneity. SV2A and SV2B were found in two forms of high and low molecular sizes according to their extent of glycosylation in sheep brain. SV2A predominated in CL, where forms with very high molecular sizes were detected. Immunohistochemical examination revealed that SV2A was localized in the extracellular matrix of both gray and white matter. In contrast, phosphacan and SV2B were mainly localized in the white matter in all brain regions. The results of the present study demonstrated that KS-PGs are present in the three areas of the sheep brain, showing significant variations in their content, structure and localization among the distinct areas. These differences may be important for the physiology of the brain.