Soluble low-density lipoprotein receptor-related protein.

Soluble forms of receptors can influence the activity of their membrane-bound counterparts by affecting their interactions with ligands. Low density lipoprotein (LDL) receptor-related protein (LRP), a member of the LDL receptor family, binds multiple classes of ligands and has been implicated in a broad range of normal and disease processes involving lipid metabolism, protease clearance, and cell migration. We recently identified a soluble form of LRP (sLRP) in human plasma and showed that it retains LRP-ligand binding ability. These findings open potentially important additional aspects in the biology of this multifunctional receptor. This review summarizes characteristics of soluble LRP and relates these to the membrane-bound form of the receptor.