Endocytosis and degradation of interstitial retinol-binding protein: Differential capabilities of cells that border the interphotoreceptor matrix

Joe G. Hollyfield, Hugh H. Varner, Mary E. Rayborn, Gregory I. Liou, C. David Bridges

Research output: Contribution to journalArticle

30 Scopus citations


Between the pigment epithelium and the outer limiting membrane of the retina is an extracellular compartment filled with the interphotoreceptor matrix (IPM). A prominent component of the IPM is a glycoprotein known as interstitial retinol-binding protein (IRBP). Using in vitro techniques, we compared the ability of the cells that border this compartment to internalize colloidal gold (CG) coated with either IRBP or ovalbumin, a glycoprotein not found in the IPM. Neither IRBP-CG nor ovalbumin-CG was internalized by the Muller’s cells. Both rod and cone photoreceptors take up IRBP-CG, which is observed in small vesicles and multivesicular bodies. Neither photoreceptor type takes up ovalbumin-CG. Acid phosphatase cytochemistry indicates that acid phosphatase reaction product in the multivesicular bodies co-localizes with IRBP-CG, which suggests that this molecule is degraded by rod and cone photoreceptors and is not recycled. The pigment epithelium internalizes IRBP-CG and ovalbumin-CG, both of which remain in small cytoplasmic vesicles near the apical plasma membrane. There is no indication that vesicles that contain either IRBP-CG or ovalbumin-CG fuse with the lysosomal system in the pigment epithelial cells during the incubation.

Original languageEnglish (US)
Pages (from-to)1676-1681
Number of pages6
JournalJournal of Cell Biology
Issue number5
Publication statusPublished - May 1 1985


ASJC Scopus subject areas

  • Cell Biology

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