methodology-for-studying-interactions-vitamin-membrane-receptors

Methodology for Studying Interactions of Vitamin A Membrane Receptors and Opsin Protein with their Ligands in Generating the Retinylidene Protein

Distribution of dietary vitamin A/all-trans retinol (ROL) throughout the body is critical for maintaining retinoid function in peripheral tissues and ...

quantitative-analysis-dietary-vitamin-metabolites-murine-ocular-non

Quantitative Analysis of Dietary Vitamin A Metabolites in Murine Ocular and Non-Ocular Tissues Using High-Performance Liquid Chromatography

G protein-coupled receptors (GPCRs) are a superfamily of transmembrane proteins that initiate signaling cascades through activation of its G protein upon ...

University of Minnesota

In this review, we outline our current understanding of the mechanisms involved in the absorption, storage, and transport of dietary vitamin A to the eye, and the trafficking of rhodopsin protein to the photoreceptor outer segments, which encompasses the logistical backbone required for photoreceptor cell function. Two key mechanisms of this process are emphasized in this manuscript: ocular and systemic vitamin A membrane transporters, and rhodopsin transporters. Understanding the complementary mechanisms responsible for the generation and proper transport of the retinylidene protein to the photoreceptor outer segment will eventually shed light on the importance of genes encoded by these proteins, and their relationship on normal visual function and in the pathophysiology of retinal degenerative diseases.

The Logistical Backbone of Photoreceptor Cell Function: Complementary Mechanisms of Dietary Vitamin A Receptors and Rhodopsin Transporters.

The distribution of dietary vitamin A/all- retinol (ROL) throughout the body is critical for maintaining retinoid function in peripheral tissues and for generating visual pigments for photoreceptor cell function. ROL circulates in the blood bound to the retinol binding protein 4 (RBP4) as RBP4-ROL. Two membrane receptors, RBPR2 in the liver and STRA6 in the eye are proposed to bind circulatory RBP4 and this mechanism is critical for internalizing ROL into cells. Here, we present a longitudinal investigation towards the importance of RBPR2 and influence of the diet on systemic retinoid homeostasis for visual function. Age matched -KO (  ) and wild-type (WT) mice were fed either a vitamin A sufficient (VAS) or a vitamin A deficient (VAD) diet. At 3- and 6-months, we performed retinoid quantification of ocular and non-ocular tissues using HPLC analysis and complemented the data with visual physiology, rhodopsin quantification by spectrophotometry, and biochemical analysis. At 3-months and compared to WT mice,   mice fed either vitamin A diets displayed lower scotopic and photopic electroretinogram (ERG) responses, which correlated with HPLC analysis that revealed   mice had significantly lower hepatic and ocular retinoid content. Interestingly, with the exception of the liver, long-term feeding of   mice with a VAS diet promoted all- retinol accumulation in most peripheral tissues. However, even under VAS dietary conditions significant amounts of unliganded opsins in rods, together with decreased visual responses were evident in aged mice lacking RBPR2, when compared to WT mice. Together, our analyses characterize the molecular events underlying nutritional blindness in a novel mouse model and indicate that loss of the liver specific RBP4-ROL receptor, RBPR2, influences systemic retinoid homeostasis and rhodopsin synthesis, which causes profound visual function defects under severe vitamin A deficiency conditions.

Anjelynt Lor

Department of Ophthalmology and Visual Neurosciences

University of Minnesota

Methodology for Studying Interactions of Vitamin A Membrane Receptors and Opsin Protein with their Ligands in Generating the Retinylidene Protein

Quantitative Analysis of Dietary Vitamin A Metabolites in Murine Ocular and Non-Ocular Tissues Using High-Performance Liquid Chromatography

Anjelynt Lor

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Ophthalmology and Visual Neurosciences

University of Minnesota

Methodology for Studying Interactions of Vitamin A Membrane Receptors and Opsin Protein with their Ligands in Generating the Retinylidene Protein

Quantitative Analysis of Dietary Vitamin A Metabolites in Murine Ocular and Non-Ocular Tissues Using High-Performance Liquid Chromatography

Department of Ophthalmology and Visual Neurosciences