Mediates the transport of lipoprotein lipase LPL from the basolateral to the apical surface of endothelial cells in capillaries (By similarity). Anchors LPL on the surface of endothelial cells in the lumen of blood capillaries (By similarity). Protects LPL against loss of activity, and against ANGPTL4-mediated unfolding (PubMed:27929370, PubMed:29899144). Thereby, plays an important role in lipolytic processing of chylomicrons by LPL, triglyceride metabolism and lipid homeostasis (PubMed:19304573, PubMed:21314738). Binds chylomicrons and phospholipid particles that contain APOA5 (PubMed:17997385, PubMed:19304573). Binds high-density lipoprotein (HDL) and plays a role in the uptake of lipids from HDL (By similarity).