BIGLYCAN GENE PROMOTER ACTIVITY IN OSTEOSARCOMA CELLS IS REGULATED BYCYCLIC-AMP

The pericellular proteoglycan biglycan is among the major secretory pr oducts of osteoblasts and articular chondrocytes but the regulatory ag ents and signal transduction pathways that ultimately lead to alterati ons in biglycan gene expression are poorly defined. We report here on the transcriptional up-regulation of biglycan in MG-63 osteosarcoma ce lls by agents that increase intracellular cAMP levels. Transfection of these cells with biglycan promoter luciferase reporter fusion genes a nd subsequent treatment with forskolin or the cAMP analog 8-Bromo-cAMP resulted in an up to 3.8-fold stimulation of biglycan promoter activi ty. This effect could be prevented with the compound KT5720, a specifi c inhibitor of the cAMP-dependent protein kinase. Up-regulation of tra nscription is also reflected at the level of mRNA expression, since bi glycan mRNA steady state levels in MG-63 cells increased similar to 2- fold after 24 hours of forskolin treatment. These data suggest that el evated levels of intracellular cAMP increase transcription from the bi glycan promoter in bone cells and implicate for the first time the cAM P/protein kinase A signal transduction pathway in the regulation of bi glycan gene expression. (C) 1997 Academic Press.