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Real-time Analyses of Retinol Transport by the Membrane Receptor of Plasma Retinol Binding Protein
Published on: January 28, 2013
Interstitial retinol-binding protein (IRBP) in retinoblastoma
C D Bridges1, S L Fong, R A Landers
1Cullen Eye Institute, Department of Ophthalmology, Baylor College of Medicine, Houston, TX 77030, U.S.A.
Neurochemistry International
|May 25, 2010
Summary
Interstitial retinol-binding protein (IRBP), an extracellular glycoprotein, was detected in retinoblastomas. This suggests potential defects in IRBP gene regulation in these malignant tumors and highlights the role of retinoid-binding proteins in cancer.
Area of Science:
- Ophthalmology
- Oncology
- Biochemistry
Background:
- Interstitial retinol-binding protein (IRBP) is an extracellular glycoprotein normally synthesized by retinal photoreceptors.
- IRBP facilitates retinoid transport between the retina and pigment epithelium.
- Its presence is typically associated with photoreceptor differentiation.
Purpose of the Study:
- To investigate the presence and characteristics of IRBP in retinoblastoma tissues.
- To explore the potential role of IRBP in retinoblastoma pathogenesis.
- To examine the synthesis and secretion of IRBP by retinoblastoma cells.
Main Methods:
- Immunochemical analysis of IRBP in retinoblastoma tissue samples.
- Quantification of IRBP levels in tumor extracts and normal retinas.
- Cell culture of retinoblastoma cells with [(3)H]leucine incorporation.
- Characterization of secreted IRBP using immunoreactivity and lectin binding (concanavalin A).
Main Results:
- IRBP of normal human molecular weight (135,000) was detected in three retinoblastomas, regardless of differentiation.
- IRBP levels varied, with higher concentrations in poorly differentiated tumors compared to differentiated tumors and normal retinas.
- Retinoblastoma cells (Tumor 3) secreted newly synthesized, glycosylated, and immunoreactive IRBP into the culture medium.
Conclusions:
- The presence of IRBP in retinoblastomas suggests a potential defect in the regulation of its gene, which is normally associated with photoreceptor differentiation.
- These findings indicate that retinoblastomas can synthesize and secrete IRBP, an extracellular retinoid-binding protein.
- This study establishes the presence of an extracellular retinoid-binding protein in tumor tissue, relevant to understanding retinoid roles in neoplastic cells.
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