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Microscopic and biochemical characterization of lectin binding sites in the cephalopod retina
Author(s) -
Taba Ali,
Quezada Beatrice H.,
Robles Laura J.
Publication year - 1989
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/cne.902830409
Subject(s) - biology , cytochemistry , lectin , peanut agglutinin , griffonia simplicifolia , wheat germ agglutinin , biochemistry , soybean agglutinin , retina , microbiology and biotechnology , photopigment , retinal , biophysics , enzyme , neuroscience
Using light and electron microscope cytochemistry and lectin blotting techniques, we have shown that the lectins concanavalin A (Con A), Ricinus communis agglutinin (RCA), and peanut agglutinin (PNA) bind to specific glycoconjugants in the adult cephalopod retina. For light microscope lectin cytochemistry, aldehyde‐fixed, frozen, or Araldite‐embedded, etched sections of cephalopod retinas were incubated with FITC‐ or TRITC‐conjugated lectins and examined by using epifluorescence microscopy. Con A labeled structures in the entire retina including the inner limiting membrane (ILM), rhabdomeric membranes, interphotoreceptor matrix (IPM), and structures in the photoreceptor inner segments. RCA labeling was similar to that of Con A except that there was a decrease in the staining of the rhabdom tips near the ILM. PNA labeled only the interphotoreceptor matrix between apposing rhabdomeres. The intensity of staining of the IPM by PNA also decreased or was absent toward the rhabdom tips. None of the lectins labeled the myeloid bodies located in the photoreceptor inner segments. Electron microscope (EM) lectin cytochemistry was performed on aldehyde‐fixed, LR White–embedded tissue or on Araldite‐embedded, periodate‐etched sections by using gold‐conjugated lectins. EM results confirmed the observations made by light microscopy. Lectin blots with a retinal extract or light‐sensitive membrane fraction revealed a variety of protein bands labeled by all three lectins. Con A and RCA labeled opsin and its aggregates whereas PNA did not. None of the lectins labeled retinochrome. The labeling of the cephalopod IPM by PNA suggests a structural similarity between the IPM of vertebrates and invertebrates. In other studies, we have demonstrated the presence of a retinoid binding protein in the IPM of cephalopods. Thus, cephalopods may serve as a model for further investigations on the structure and function of the IPM and its role in the vitamin A cycle of the retina.