The role of the low-density lipoprotein receptor-related protein (LRP1) in Alzheimer's A beta generation: development of a cell-based model system.
The clearance and degradation of extracellular A beta is critical for regulating beta-amyloid deposition, a major hallmark of brains of patients with A beta in Alzheimer's Disease. The low-density lipoprotein receptor-related protein, LRP1, is a large endocytic receptor that significantly contributes to the balance between degradation and production of A beta. An extracellular portion of the LRP, known as the cluster II region can bind to the secreted form of APP (sAPP-KPI). We show here that a GST fusion protein containing the cluster II region of LRP can be used as a 'mini-receptor' that specifically binds to sAPP-KPI from conditioned cultured medium. The binding between the GST-LRP-cluster II fusion protein and sAPP-KPI can be inhibited with the strong binding ligand of LRP1, called receptor-associated protein (RAP). Furthermore, a cell-based in vitro assay system has been developed to monitor the production of total A beta and A beta(1-42) in the presence and absence of RAP in Chinese hamster ovary (CHO) cell lines both deficient in LRP and expressing LRP. A 3-day treatment of the L2 (CHO cells deficient in LRP and overexpressing APP751) and L3 (CHO cells expressing LRP and overexpressing APP751) cell lines with RAP showed a decrease in total A beta and, interestingly, also a decrease in the ratio of A beta42/A beta(total). This cell-based model system and LRP-cluster II mini-receptor will be very useful for screening novel compounds that can reduce A beta accumulation by inhibiting binding of APP-KPI to LRP1.
Goto
Joy J
JJ
Genetics and Aging Research Unit, Center for Aging, Genetics and Neurodegeneration, Boston, MA 02129, USA.
Tanzi
Rudolph E
RE
D000544:Alzheimer Disease / Q000378:metabolism*; D016229:Amyloid beta-Peptides / Q000096:biosynthesis* / Q000378:metabolism; D000818:Animals; D016466:CHO Cells; D002478:Cells, Cultured; D006224:Cricetinae; D004797:Enzyme-Linked Immunosorbent Assay; D005110:Extracellular Space; D006801:Humans; D026503:Low Density Lipoprotein Receptor-Related Protein-1 / Q000378:metabolism*
D016229:Amyloid beta-Peptides; D026503:Low Density Lipoprotein Receptor-Related Protein-1