May play a role in lipid exchange and transport throughout the body. May participate in reverse cholesterol transport from peripheral cells to the liver. In plasma, interacts with APOA1 and mainly associated with large high density lipoprotein particles. Plasma. Found on APOA-I-containing high density lipoprotein (HDL3). Expressed in pancreas, lung, prostate, liver, placenta and spleen. Phosphorylated by FAM20C in the extracellular medium. The disease is caused by variants affecting the gene represented in this entry. Major isoform. Belongs to the apolipoprotein L family.