Axonal transport of proteoglycans to the goldfish optic tectum

Abstract

The study addressed the question of whether 35SO4 labeled molecules that have been delivered to the goldfish optic nerve terminals by rapid axonal transport include soluble proteoglycans. For analysis, tectal homogenates were subfractionated into a soluble fraction (soluble after centrifugation at 105,000 g), a lysis fraction (soluble after treatment with hypotonic buffer followed by centrifugation at 105,000 g) and a final 105,000 g pellet fraction. The soluble fraction contained 25.7% of incorporated radioactivity and upon DEAE chromatography was resolved into a fraction of sulfated glycoproteins eluting at 0-0.32 M NaCl and containing 39.5% of total soluble label and a fraction eluting at 0.32-0.60 M NaCl containing 53.9% of soluble label. This latter fraction was included on columns of Sepharose CL-6B with or without 4 M guanidine and after pronase digestion was found to have 51% of its radioactivity contained in the glycosaminoglycans (GAGs) heparan sulfate and chondroitin (4 or 6) sulfate in the ratio of 70% to 30%. Mobility of both intact proteoglycans and constituent GAGs on Sepharose CL-6B indicated a size distribution that is smaller than has been observed for proteoglycans and GAGs from cultured neuronal cell lines. Similar analysis of lysis fraction, containing 11.5% of incorporated 35SO4, showed a mixture of heparan sulfate and chondroitin sulfate containing proteoglycans, apparent free heparan sulfate and few, if any, sulfated glycoproteins. Overall, the results support the hypothesis that soluble proteoglycans are among the molecules axonally transported in the visual system.

Expression of chondroitin sulfate and keratan sulfate proteoglycans in the path of growing retinal axons in the developing chick

“…Intracellular immunostaining for chondroitin sulfate proteoglycan was observed in ganglion cells in the adult rat retina (Aquino et al, 1984a). Also, axonal transport of radiolabeled glycosaminoglycans from the retina to the central visual nuclei was reported in goldfish (Ripellino and Elam, 1988) and rat (Gammon et a]., 1985). Although retinal ganglion cells produce proteoglycans, it is likely that other cell types along the visual pathway make proteoglycans as well.…”

The principal neuronal gD-type 3-O-sulfotransferases and their products in central and peripheral nervous system tissues☆

“…On one hand, these data suggest that region specific expression of these isoforms may lead to region specific accumulation of 3-OST-2/4-type products. On the other hand, HSPGs generated by neurons can undergo axonal transport (Dow et al, 1994;Ripellino et al, 1988). Thus, 3-OST-2/4-type products generated in neuronal cell bodies may also be transported to their distant nerve endings.…”