A novel role for scavenger receptor B1 as a contributor to the capture of specific volatile odorants in the nasal cavity

Satoshi TSUZUKI, Yusaku KIMOTO, Shinhye LEE, Tatsuya SUGAWARA, Yuki MANABE, Kazuo INOUE
2018 Biomedical research  
Class B scavenger receptors, scavenger receptor B1 (SR-B1) and cluster of differentiation 36 (CD36), are broadly expressed cell-surface proteins and are believed to serve as multifaceted players in lipid and lipoprotein metabolism in mammals. Because of its ability to recognise distinct odour-active volatile compounds and its presence in murine olfactory epithelium, CD36 has recently emerged as a participant in the detection of odorants within the nasal cavity. However, there have been no
more » ... have been no attempts to assess whether SR-B1 has such a role. In this study, we performed a cell-free in-vitro assay utilising a peptide mimic of the receptor, and demonstrated that SR-B1 could recognise aliphatic aldehydes (e.g., tetradecanal), a distinct class of volatile odorants, as potential ligands. By reverse transcription-polymerase chain reaction and western immunoblot analyses, we detected the expression of SR-B1 mRNA and protein, respectively, in mouse olfactory tissue. Finally, we immunohistochemically mapped the distribution of SR-B1 in the surface layer of olfactory epithelium in vivo, which is the first line of odorant detection. These findings uncover a novel role for SR-B1 as a contributor to the capture of specific odorants in the nasal cavity of mammals. Class B scavenger receptors are cell-surface proteins, characterised by two predicted transmembrane spans, broad expression patterns and the ability to recognise diverse ligands (13). Of these, scavenger receptor B1 (SR-B1) was initially identified as comprising 509 amino-acid residues (5). An earlier study has showed that SR-B1 is expressed in several tissues including the liver and adipose tissues, and can serve as a receptor for low-density lipoprotein (LDL), acetylated LDL, oxidised LDL (oxLDL) and maley-lated bovine serum albumin (BSA) (2). Later, SR-B1 was found to recognise several other substances such as high-density lipoprotein (HDL) (1) and anionic phospholipids (15). These findings suggested that SR-B1 primarily participates in lipid and lipoprotein metabolism in internal organs (36). As studied extensively, it functions as a physiologically relevant HDL receptor to mediate the selective delivery of HDL-cholesterol (i.e., HDL-cholesteryl ester) to the liver and steroidogenic tissues (1, 13, 20) . Another member of class B scavenger receptors, cluster of differentiation 36 (CD36), which comprises 472 amino-acid residues, is also a multifaceted and multifunctional player in lipid and lipoprotein metabolism (13, 27, 28) . CD36 is known to share with SR-B1 the ability to recognise distinct ligands,
doi:10.2220/biomedres.39.117 pmid:29899187 fatcat:56gr7y2i4fdeflba474kz3gcua