cDNA cloning of a novel secreted isoform of the human receptor for advanced glycation end products and characterization of cells co-expressing cell-surface scavenger receptors and Swedish mutant amyloid precursor protein

The receptor for advanced glycation end products (RAGE) has been proposed as a cell surface receptor that binds amyloid-beta protein (A beta), thereby triggering its cytotoxic effects [S.D. Yan, X. Chen, J. Fu, M. Chen, H. Zhu, A. Roher, T. Slattery, L. Zhao, M. Nagashima, J. Morser, A. Migheli, P. Nawroth, D. Stem, A.M. Schmidt, RAGE and amyloid-P peptide neurotoxicity in Alzheimer's disease, Nature 382 (1996) 685-691.]. A cDNA library of human lung was screened for RAGE with an appropriate hybridization probe. In addition to cell surface RAGE, one clone was found which encodes a new version of RAGE, termed hRAGEsec, which lacks the 19 amino acids of the membrane-spanning region and is therefore secreted. Comparison with the genomic sequence revealed that the synthesis of the secreted isoform requires alternative splicing. The deduced protein sequence of the mature hRAGEsec consists of 321 amino acids with a predicted molecular mass of 35.66 kDa. The pattern of expression of hRAGEsec in human brain was analyzed by in situ hybridization histochemistry. The most intense expression of the gene in contrast to cell surface RAGE was detected in hippocampal CA3 pyramidal cells, dentate gyms granule cells, cortical neurons as well, as glial cells in white matter. To investigate the interaction between A beta and RAGE and another scavenger receptor, SRA, under physiological conditions, they were co-expressed with human beta APP(695)-SFAD in a human cell and the level of A beta in the condition medium was assessed by immunoprecipitation and enzyme-linked immunosorbent assay (ELISA) analysis. A nearly 100% reduction of A beta from the conditioned medium of hRAGE cells and similar to 40% reduction from the SRA-cells implied that hRAGE could be a prominent cell surface receptor interacting with AP. (C) 1999 Elsevier Science B.V. All rights reserved.