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Chondroitin sulfate proteoglycan specific to retinal horizontal neurons
Author(s) -
Williams C.,
Villegas M.,
Atkinson R.,
Miller C.A.
Publication year - 1998
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/(sici)1096-9861(19980112)390:2<268::aid-cne9>3.0.co;2-#
Subject(s) - biology , outer plexiform layer , inner plexiform layer , retina , retinal , microbiology and biotechnology , chondroitin sulfate , ribbon synapse , proteoglycan , immunocytochemistry , synapse , neurite , inner nuclear layer , biophysics , extracellular matrix , anatomy , biochemistry , glycosaminoglycan , neuroscience , synaptic vesicle , vesicle , membrane , endocrinology , in vitro
Proteoglycans (PGs) are a diverse group of highly glycosylated macromolecules that are implicated in the development and maintenance of neuronal circuitry. With its highly ordered, layered structure, the retina ideally serves to define the synthesis, processing, and distribution of these molecules within a specific cellular subpopulation. In retinal sections, monoclonal antibody (MAb) 6A2 immunostained a horizontal cell‐specific antigen. Antigen 6A2 was expressed within abundant processes in the outer plexiform layer and in rare neurites that extend across the inner nuclear layer to the inner plexiform layer. Ultrastructurally, the antigen was localized to cisternae within horizontal cell somata, along tubulovesicular structures in dendrites, and in the perisynaptic space encircling presynaptic terminals of the cone photoreceptor triad. These findings suggest that this PG is synthesized within the horizontal cells, transported to the terminals, and released into the extracellular spaces just proximal to the synapse. Based on the focal stain in the adjacent photoreceptor cell, it is possible that antigen is pinocytosed by this cell and is concentrated at the ribbon synapse. In Western immunoblots of retinal homogenates, MAb 6A2 recognized a heterogeneous chondroitin sulfate (CS) PG (CSPG) of approximately 400–500 kDa. After sequential enzymatic removal of CS glycosaminoglycans, a major broad band of 300–500 kDa was identified by MAb 1B5, which detects CSPGs that bear uronic acid linked to unsulfated N‐acetylgalactosamine as the initial disaccharide in the CS chain. Localization of this PG around presynaptic terminals of the horizontal neuron and at the ribbon synapse suggests that it may play a modulatory and sustaining role at the synapse. J. Comp. Neurol. 390:268–277, 1998. © 1998 Wiley‐Liss, Inc.