Fam57b (Family with Sequence Similarity 57, Member B), a Novel Peroxisome Proliferator-activated Receptor γ Target Gene That Regulates Adipogenesis through Ceramide Synthesis

• Published in: The Journal of biological chemistry Vol. 288; no. 7; pp. 4522 - 4537
• Main Authors: Yamashita-Sugahara, Yzumi, Tokuzawa, Yoshimi, Nakachi, Yutaka, Kanesaki-Yatsuka, Yukiko, Matsumoto, Masahito, Mizuno, Yosuke, Okazaki, Yasushi
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15.02.2013; American Society for Biochemistry and Molecular Biology
• Subjects: 3T3 Cells; Adipocytes - cytology; Adipogenesis; Animals; Base Sequence; Cell Biology; Cell Differentiation; Ceramide; Ceramides - metabolism; Diet, High-Fat; Disease Models, Animal; Gene Expression Regulation; Membrane Proteins - metabolism; Metabolic Syndrome - genetics; Mice; Molecular Sequence Data; Obesity; Obesity - genetics; Obesity - metabolism; Oligonucleotide Array Sequence Analysis; Peroxisome Proliferator-activated Receptor (PPAR); PPAR gamma - metabolism; RNA, Small Interfering - metabolism; Sequence Homology, Nucleic Acid; Signal Transduction; Sphingolipid; Sphingolipids - metabolism; Sphingosine N-Acyltransferase - biosynthesis; Sphingosine N-Acyltransferase - genetics; Stromal Cells - cytology; Ceramide; Sphingolipid; Obesity; Peroxisome Proliferator-activated Receptor (PPAR); Adipogenesis
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M112.440792

This report identifies a novel gene encoding Fam57b (family with sequence similarity 57, member B) as a novel peroxisome proliferator-activated receptor γ (PPARγ)-responsive transmembrane gene that is related to obesity. The gene was identified based on an integrated bioinformatics analysis of the following three expression profiling data sets: adipocyte differentiation of mouse stromal cells (ST2 cells), adipose tissues from obesity mice, and siRNA-mediated knockdown of Pparγ using ST2 cells. Fam57b consists of three variants expressed from different promoters and contains a Tram-Lag1-CLN8 domain that is related to ceramide synthase. Reporter and ChIP assays showed that Fam57b variant 2 is a bona fide PPARγ target gene in ST2 cells. Fam57b was up-regulated during adipocyte differentiation, suggesting that FAM57B is involved in this process. Surprisingly, FAM57B overexpression inhibited adipogenesis, and siRNA-mediated knockdown promoted adipocyte differentiation. Analysis of the ceramide content by lipid assay found that ceramides were in fact augmented in FAM57B-overexpressing ST2 cells. We also confirmed that ceramide inhibits adipogenesis. Therefore, the aforementioned results of FAM57B overexpression and siRNA experiments are reconciled by ceramide synthesis. In summary, we present in vitro evidence showing that PPARγ regulates Fam57b transcription during the adipogenesis of ST2 cells. In addition, our results suggest that PPARγ activation contributes to the regulation of ceramide metabolism during adipogenesis via FAM57B. Background:Fam57b was identified as a putative novel PPARγ target up-regulated in adipocytes and adipose tissue. Results:Fam57b was confirmed as a novel target of PPARγ by reporter and ChIP assays. FAM57B synthesizes ceramides and inhibits adipogenesis in mouse stromal ST2 cells. Conclusion: FAM57B regulates adipogenesis through ceramide synthesis. Significance: This study reveals one of the pleiotropic actions of PPARγ related to ceramide metabolism.