Structural component of lipid droplets, which is required for the formation and maintenance of lipid storage droplets (PubMed:34077757). Required for the transport of mannose 6-phosphate receptors (MPR) from endosomes to the trans-Golgi network (PubMed:9590177). Homooligomer (PubMed:9590177). Interacts with M6PR (via the cytoplasmic domain) (PubMed:9590177). Interacts with IGF2R (via the cytoplasmic domain) (PubMed:9590177). May exist as a homodimer. Membrane associated on endosomes (PubMed:15545278). Detected in the envelope and the core of lipid bodies and in lipid sails (PubMed:15545278). Phosphorylation at Tyr-251 by isoform 1 of CHKA (CHKalpha2) promotes dissociation from lipid droplets: dissociation is followed by recruitment of autophagosome machinery to lipid droplets and subsequent lipid droplet lipolysis. Belongs to the perilipin family.