fam134b, a Novel Golgi Protein, Influences Adipogenesis By Regulating Golgi Vesicular Transport in Porcine Adipocytes

The global epidemic of obesity is associated with high risks of metabolic diseases. The domestic pig is considered as an important laboratory animal model for human diseases including obesity. Of particular interests, the Chinese Jinhua pigs are known for their rich subcutaneous and intramuscular fat content, making them an ideal model to study fat deposition. We have recently reported that compared to the Landrace pigs, Jinhua pigs expressed higher levels of the gene Family with Sequence Similarity 134, Member B (FAM134B) in their subcutaneous fat (SAT), indicating that FAM134B might play a crucial role in regulating fat deposition and lipid metabolism in animals. In this study, we found that the expression of FAM134B increases during porcine adipocytes differentiation. Transfection of preadipocytes with FAM134B resulted in accelerated differentiation and increased triglyceride accumulation after hormonal stimulation. The mRNA expression of adipogenesis related genes C/EBPα, C/EBPβ and FAS were upregulated (p<0.05) whereas the key lipolysis gene ATGL was downregulated (p<0.05) by FAM134B overexpression .Immunofluorescence staining demonstrates that FAM134B is directly targeted to cis-Golgi membrane, potentially functioning to affect transport of vesicle and lipid-related proteins in adipocytes. In addition, overexpression of FAM134B upregulated Golgi-protein ARFRP1, and knockdown of ARFRP1 abolished the effect of FAM135B overexpression on lipid accumulation. the ARF-like GTPases (ARLs) and the family of PAT genes. The expression of ARF1, ARF6, ARFRP1, PLIN and ADRP were upregulated (p<0.05) by FAM134B overexpression (Fig. 2M) and were downregulated (p<0.05) byFAM134B knockdown in porcine adipocytes (Fig. 2O). GTPase’s enzyme activity, the key factor of vesicle transport in porcine adipocytes, was also increased (p<0.05).These results indicate that FAM134B positively regulates the lipid accumulation and adipogenic differentiation by targeting vesicle transport in the Golgi apparatus.