Characterization of scavenger receptor class B, type I in Atlantic salmon ( Salmo salar L.)

• Published in: Lipids
• Main Authors: Kleveland, E. J., Syvertsen, B. L., Ruyter, B., Vegusdal, A., Jørgensen, S. M., Gjøen, T.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2006
• Subjects: Atlantic salmon; Salmo salar
• Online Access: http://dx.doi.org/10.1007/s11745-006-5052-3; https://onlinelibrary.wiley.com/doi/full/10.1007/s11745-006-5052-3

Abstract The scavenger receptor class B, type I (SR‐BI) is an important player in regulation of mammalian lipid homeostasis. We therefore wanted to study this receptor in Atlantic salmon ( Salmo salar L.), which requires a diet with particular high lipid content. We have for the first time cloned and characterized SR‐BI from a salmonid fish. The predicted 494 amino acid protein contained two transmembrane domains, several putative N‐glycosylation sites, and showed 72% sequence identity with the predicted homolog from zebrafish. SR‐BI expression was analyzed by reverse transcription Real‐Time PCR in several tissues, and a high relative expression in salmon midgut was detected, which may suggest that SR‐BI has a role in uptake of lipids from the diet. We also expressed a construct of salmon myc ‐tagged SR‐BI in salmon TO cells and HeLa cells, which gave a protein of approximately 80 kDa on reducing SDS‐PAGE using an antibody against the myc ‐epitope. Immunofluorescence microscopy analyses of the salmon SR‐BI protein in transiently transfected HeLa cells revealed staining in the cell periphery and in some intracellular membranes, but not in the nucleus, which indicated that the salmon protein may be a functional membrane protein. We also observed a high degree of co‐localization using an anti‐peptide SR‐BI antiserum. We found that 20 μg mL −1 insulin up‐regulated the SR‐BI mRNA levels in primary cultures of salmon hepatocytes relative to untreated cells. Oleic acid, EPA, DHA, or dexamethasone did not affect the relative expression of SR‐BI in this liver model system. In conclusion, the salmon SR‐BI cDNA encoded a protein with several features common to those of mammalian species. SR‐BI gene expression was high in the intestine, which leads us to propose that SR‐BI may contribute to the uptake of lipids from the diet.