title: Cellular retinaldehyde-binding protein is expressed by oligodendrocytes in optic nerve and brain.
abstract: Cellular retinaldehyde-binding protein (CRALBP) is abundant in the retinal pigment epithelium and Müller glial cells of the retina, where it forms complexes with endogenous 11-cis-retinoids. We examined the distribution of CRALBP in extraretinal tissues using polyclonal antibodies (pAb) and monoclonal antibodies (mAb). A protein was detected by immunoblot analysis in extracts of bovine and rat brain and optic nerve but not in several other tissues. This protein had electrophoretic, chromatographic, and retinoid-binding properties identical to those of CRALBP from bovine retina. Comparison of the masses of tryptic peptides and of partial amino acid sequences derived from brain and retinal CRALBP indicated that the two proteins are probably identical. Immunoperoxidase cytochemistry and double labeling immunofluorescence revealed CRALBP(+) cells in brain that resembled oligondendrocytes and not astrocytes, microglial cells, or pinealocytes. In 11-day-old rat brain, approximately 11% of the CRALBP(+) cells were labeled with the Rip antibody, a marker for oligodendroglia. In developing rat optic nerve, the temporal appearance of CRALBP(+) cells corresponded to that of oligodendrocytes and not that of astrocytes. In adult rat and mouse optic nerves, the CRALBP(+) somata showed the same distribution as oligodendrocytes. No endogenous retinoids were associated with CRALBP isolated from dark-dissected adult bovine brain. The results suggest that CRALBP has functions in addition to retinoid metabolism and visual pigment regeneration.
authors.affiliation: Department of Ophthalmology, School of Medicine, University of Washington, Seattle 98195-6485, USA. jsaari@u.washington.edu
authors.forename: J C
authors.initials: JC
authors.lastname: Saari
authors.forename: J
authors.initials: J
authors.lastname: Huang
authors.forename: D E
authors.initials: DE
authors.lastname: Possin
authors.forename: R N
authors.initials: RN
authors.lastname: Fariss
authors.forename: J
authors.initials: J
authors.lastname: Leonard
authors.forename: G G
authors.initials: GG
authors.lastname: Garwin
authors.forename: J W
authors.initials: JW
authors.lastname: Crabb
authors.forename: A H
authors.initials: AH
authors.lastname: Milam
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies / Q000276:immunology; D001921:Brain / Q000166:cytology / Q000378:metabolism*; D002352:Carrier Proteins / Q000096:biosynthesis*; D002417:Cattle; D007124:Immunoenzyme Techniques; D008969:Molecular Sequence Data; D009836:Oligodendroglia / Q000378:metabolism*; D009900:Optic Nerve / Q000166:cytology / Q000196:embryology / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D012160:Retina / Q000378:metabolism
chemical_list: C020932:11-cis-retinal-binding protein; D000906:Antibodies; D002352:Carrier Proteins