title: Cone outer segment extracellular matrix as binding domain for interphotoreceptor retinoid-binding protein.
abstract: Cones are critically dependent on interphotoreceptor retinoid-binding protein (IRBP) for retinoid delivery in the visual cycle. Cone-dominant vertebrates offer an opportunity to uncover the molecular basis of IRBP's role in this process. Here, we explore the association of IRBP with the interphotoreceptor matrix (IPM) of cones vs. rods in cone dominant retinas from chicken (Gallus domesticus), turkey (Meleagris gallopavo), and pig (Sus scrofa). Retinas were detached and fixed directly or washed in saline prior to fixation. Disassociated photoreceptors with adherent matrix were also prepared. Under 2 mM CaCl(2) , insoluble matrix was delaminated from saline washed retinas. The distribution of IRBP, as well as glycans binding peanut agglutinin (cone matrix) and wheat germ agglutinin (rod/cone matrix), was defined by confocal microscopy. Retina flat mounts showed IRBP diffusely distributed in an interconnecting, lattice-like pattern throughout the entire matrix. Saline wash replaced this pattern with fluorescent annuli surrounding individual cone outer segments. In isolated cones and matrix sheets, IRBP colocalized with the peanut agglutinin binding matrix glycans. Our results reveal a wash-resistant association of IRBP with a matrix domain immediately surrounding cone outer segments. The cone matrix sheath may be responsible for IRBP-mediated cone targeting of 11-cis retinoids.
authors.affiliation: Graduate Program in Neuroscience, School of Medicine and Biomedical Sciences, State University of New York, Buffalo, New York 14209, USA.
authors.forename: Mary Alice
authors.initials: MA
authors.lastname: Garlipp
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Nowak
authors.forename: Federico
authors.initials: F
authors.lastname: Gonzalez-Fernandez
mesh_terms: D000818:Animals; D002645:Chickens; D005109:Extracellular Matrix / Q000378:metabolism*; D005136:Eye Proteins / Q000378:metabolism*; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D007091:Image Processing, Computer-Assisted; D037102:Lectins / Q000378:metabolism; D008297:Male; D018613:Microscopy, Confocal; D011485:Protein Binding; D012160:Retina / Q000378:metabolism; D017949:Retinal Cone Photoreceptor Cells / Q000378:metabolism*; D012177:Retinol-Binding Proteins / Q000378:metabolism*; D013552:Swine; D016707:Tissue Fixation; D014422:Turkeys; D000099214:Retinol-Binding Proteins, Interstitial
chemical_list: D005136:Eye Proteins; D037102:Lectins; D012177:Retinol-Binding Proteins; D000099214:Retinol-Binding Proteins, Interstitial