The
McCune-Albright syndrome (MAS) is characterized by
polyostotic fibrous dysplasia, café-au-lait spots, and multiple endocrine hyperfunction. An activating missense mutation of the alpha subunit of the Gs
protein (Gs alpha) was found in several affected tissues, resulting in prolonged stimulation of
adenylate cyclase. Our recent study has indicated that the cells derived from the fibrous
bone dysplasia tissues in MAS patients produced increased levels of
interleukin-6 (IL-6), which may be responsible for the increased
bone resorption in this disease. In the present investigation, to analyze the molecular mechanism of the increased
IL-6 production by activating mutant Gs alpha in bone cells, we established mouse osteoblastic MC3T3-E1 cells stably transfected with the activating mutant Gs alpha expression vector. These cells showed a significant increase of intracellular cAMP levels and produced a higher amount of
IL-6 than the cells transfected with control vector or wild-type Gs alpha expression vector. Analysis of the
IL-6 promoter revealed that any of the
AP-1, nuclear factor (NF)-IL-6, and
NF-kappa B binding elements are important for the activating mutant Gs alpha-induced gene expression. Electrophoretic mobility-shift assays using nuclear extracts of the mutant Gs alpha-expressing cells showed that phospho(Ser133)-cAMP-responsive
element binding protein (CREB),
AP-1,
NF-IL6, and
NF-kappa B were increased, compared with the control cells or the wild-type Gs alpha-expressing cells. These results indicate that activating mutant Gs alpha increases the transcriptional factors binding to CRE,
AP-1,
NF-IL6, and
NF-kappa B elements to induce
IL-6 gene expression in the osteoblastic cells.