SUBCELLULAR-LOCALIZATION OF THE LOW-DENSITY-LIPOPROTEIN RECEPTOR-RELATED PROTEIN (ALPHA(2)-MACROGLOBULIN RECEPTOR) IN HUMAN BRAIN

The subcellular localization of the alpha(2)-macroglobulin receptor, a lso known as the low density lipoprotein receptor-related protein (LRP ), was studied in postmortem human brain tissue by light and electron microscopic immunocytochemistry. A specific monoclonal antibody (A2MR2 ) against the extracellular alpha-chain of the molecule was utilized. Light microscopically, LRP was detected strongly in neurons, weakly in some glial cells and discontinuously along capillary membranes. At th e electron microscopic level, positive reaction products were found to be associated with plasma membranes, ribosomes, lysosomes and lipofus cin granules of neurons, glial cells and pericytes. The results sugges t that LRP may have a function, particularly in neurons, of receptor-m ediated endocytosis with subsequent lysosomal uptake and degradation o f ligands such as alpha(2)-macroglobulin proteinase complexes and apol ipoprotein E.