Osteosarcoma amplified 9 is highly expressed in mouse adipocytes and controls lipid storage

Adipocytes are among the most important cells for energy storage, metabolism and balance in mammals. Dysfunctional adipocytes are closely associated with type 2 diabetes and obesity, and thus with insulin resistance and inflammation. Recent studies show that endoplasmic reticulum (ER) stress may be responsible for obesity-induced insulin resistance. In this study, we investigated an ER-associated degradation-related protein in adipocytes, namely osteosarcoma amplified 9 (OS-9), a protein that is reported to have lectin activity and to be involved in ER quality control. We found that OS-9 is expressed at high levels in both types of fat tissues - brown and white adipose tissues - and we examined the subcellular localization of OS-9 in 3T3-L1 adipocytes. Furthermore, we observed that the expression levels of the OS-9 protein gradually increased as 3T3-L1 adipocytes differentiated. Most notably, we found that the depletion of this protein influences adipocyte differentiation and lipid storage, although the mechanism behind this is unclear.