EXPRESSION OF AN N-METHYL-D-ASPARTATE-TYPE RECEPTOR BY HUMAN AND RAT OSTEOBLASTS AND OSTEOCLASTS SUGGESTS A NOVEL GLUTAMATE SIGNALING PATHWAY IN BONE

Signaling between the various types of cells found in bone is responsi ble for controlling the activity of osteoblasts and osteoclasts, and t herefore the regulation of bone mass. Our identification of a neuronal glutamate transporter in osteoblasts and osteocytes suggests the poss ibility that bone cells may use the excitatory amino acid glutamate as a signaling molecule. In these studies we report the expression of di fferent subtypes of glutamate receptors in osteoblasts and osteoclasts in vitro and in vivo. We have identified expression in human and rat bone cells of N-methyl-D-aspartate receptor-1 (NMDAR-1) and to subunit s and PSD-95, the NR IDA receptor clustering protein associated with s ignaling in the central nervous system. In situ hybridization and immu nohistochemistry localized NMDAR-1 expression to osteoblasts and osteo clasts in human tissue sections, These findings strengthen the suggest ion that glutamate is involved in signaling between bone cells. (C) 19 98 by Elsevier Science Inc. All rights reserved.