EXPRESSION OF ALPHA(2)-MACROGLOBULIN RECEPTOR LOW-DENSITY-LIPOPROTEINRECEPTOR-RELATED PROTEIN IS INCREASED IN REACTIVE AND NEOPLASTIC GLIAL-CELLS

alpha(2)-Macroglobulin receptor/low density lipoprotein receptor-relat ed protein (alpha(2)M-R/LRP) is a multi-functional cell-surface recept or that has been implicated in diverse physiologic processes. In norma l human brain, alpha(2)M-R/LRP is expressed principally by pyramidal n eurons with localization to cell bodies and proximal processes. By con trast, alpha(2)M-R/LRP is not present in either the cell bodies or pro cesses of most normal macroglia (including astrocytes). In this invest igation, we studied the expression of alpha(2)M-R/LRP in the brain, fo llowing tissue injury or neoplastic transformation, by immunohistochem istry. Significantly increased alpha(2)M-RILRP immunoreactivity was id entified in reactive astrocytes, indicating that expression of this re ceptor is regulated in vivo in response to brain injury. alpha(2)M-R/L RP immunoreactivity was also detected in glial cell tumors; this findi ng is novel since malignant transformation is typically thought to tur n off expression of this receptor.