Characterization of retinol binding protein receptor 2, a putative retinol transporter and serum retinol binding protein receptor

Vitamin A (retinol) is essential for life; however, little is known about how it is transported into cells. Ninety-five percent of retinol found in blood is bound to Serum Retinol Binding Protein (RBP4), suggesting that RBP4 is important for transport of retinol. Importantly, RBP4 levels are linked to metabolic disorders such as metabolic syndrome and type 2 diabetes. A better understanding of vitamin A transport could provide potential targets for the treatment of these disorders. Our lab recently identified a potential RBP4 receptor protein, Retinol Binding Protein Receptor 2 (RBPR2), also known as Liver Stra6 Homologue (LSH). Cell culture models have revealed that LSH binds RBP4 with high affinity. We hypothesized that mice with a whole body deletion of LSH will show a reduction in retinol and retinyl esters in serum, hepatic tissue and fat.;Our experimental model consisted of transgenic mice with total body deletion of LSH and wild type litter mates, as control. Mice were sacrificed at 7 weeks and tissues stored at -80ºC. Total body deletion of the LSH gene was confirmed by Taqman quantitative PCR. Retinol and retinyl ester levels in liver, fat and serum were assessed using High Performance Liquid Chromatography.;Though no statistically significant differences were found between the retinol or retinyl ester levels in the livers or fat pads of mice with a total body deletion of LSH and wild type mice, there was a significant difference in serum retinol and retinyl ester levels between female knock out mice and female wild type. No significant differences between the two genotypes were observed in the serum of male mice. Results of this study suggest that LSH is not solely responsible for retinoid transport into cells, or whole body retinol levels, though it may play a subtler role in retinol homeostasis.