Structural component of lipid droplets, which is required for the formation and maintenance of lipid storage droplets. Required for the transport of mannose 6-phosphate receptors (MPR) from endosomes to the trans-Golgi network. Homooligomer. Interacts with M6PR (via the cytoplasmic domain). Interacts with IGF2R (via the cytoplasmic domain). Membrane associated on endosomes. Detected in the envelope and the core of lipid bodies and in lipid sails. 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.