Characterization of scavenger receptor class B, type I in Atlantic salmon (Salmo salar L.).
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 microg 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.
Kleveland
E J
EJ
Department of Pharmaceutical Biosciences, School of Pharmacy, University of Oslo, Oslo, Norway.
Syvertsen
B L
BL
Ruyter
B
B
Vegusdal
A
A
Jørgensen
S M
SM
Gjøen
T
T
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000032:analysis; D005786:Gene Expression Regulation; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D051381:Rats; D020317:Salmo salar; D051122:Scavenger Receptors, Class B / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D017422:Sequence Analysis, DNA; D013552:Swine
D018076:DNA, Complementary; D051122:Scavenger Receptors, Class B