Acts as a CEBPB coactivator in mammary epithelial cells to control the expression of a subset of CEBPB downstream target genes, including ID2, IGF1, PRLR, SOCS1, SOCS3, XDH, but not casein. By interacting with CEBPB, strengthens the association of CEBPB with the XDH promoter, increases histone acetylation and dissociates HDAC1 from the promoter (By similarity). Binds to lipid droplets and regulates their enlargement, thereby restricting lipolysis and favoring storage. At focal contact sites between lipid droplets, promotes directional net neutral lipid transfer from the smaller to larger lipid droplets. The transfer direction may be driven by the internal pressure difference between the contacting lipid droplet pair and occurs at a lower rate than that promoted by CIDEC. When overexpressed, induces apoptosis. The physiological significance of its role in apoptosis is unclear. Directly interacts with CEBPB (By similarity). Interacts with CIDEC. Enriched at lipid droplet contact sites. Has been shown to localize to mitochondria, where it could interact with UCP1 and hence inhibit UCP1 uncoupling activity (By similarity). These data could not be confirmed (PubMed:18509062). Expressed in omental and subcutaneous adipose tissue (at protein level). In omental and subcutaneous adipose tissue of obese patients matched for BMI, expression levels correlate with insulin sensitivity. Expression is increased 5-6 fold in the group of patients with high insulin sensitivity, compared to the insulin-resistant group. This observation is consistent with the idea that triglyceride storage in adipocytes plays an important role in sequestering triglycerides and fatty acids away from the circulation and peripheral tissues, thus enhancing insulin sensitivity in liver and muscle.