Human LRP-1 Cluster III Antibody

LDL receptor-related protein 1 (LRP-1), also known as CD91 and the alpha2-macroglobulin receptor, is a type I membrane protein in the LDL receptor superfamily. It is expressed on neurons, hepatocytes, adipocytes, vascular smooth muscle cells, fibroblasts, keratinocytes, macrophages, and megakaryocytes. LRP-1 is important for the clearance of a large number of circulating molecules involved in fatty acid metabolism and complexes of serine proteases with their inhibitors (1-4). LRP-1 also associates directly or through intracellular scaffold proteins with other membrane associated proteins on the same cell. This allows LRP-1 to modulate the activity or internalization of PDGF R beta, NMDA receptor subunits, TGF-beta receptors, Frizzled‑1, various integrins, and the prion protein PrP^C (1, 5‑10). Human LRP-1 is an N‑glycosylated and sialylated molecule that is cleaved in the Golgi to produce an 85 kDa transmembrane  beta chain and a 515 kDa  alpha chain that associates noncovalently with the  beta chain but does not itself cross the membrane (11, 12). The alpha chain of LRP-1 contains 31 LDLR class A repeats, 34 LDLR class B repeats, and 22 EGF‑like repeats (13). The LDLR domains are clustered in four regions throughout the protein (13). LRP-1 Cluster III (aa 2522‑2941) contains ten LDLR-A cysteine-rich domains (14). Within this region, human LRP-1 shares 97% aa sequence identity with mouse and rat LRP-1. A soluble form of LRP-1 is shed into the serum and cerebrospinal fluid and retains ligand binding properties (15, 16). LRP-1 Cluster III contains binding sites for LRPAP/RAP (14).