Serum induction of the collagen X promoter requires the Raf/MEK/ERK and p38 pathways

The collagen X gene is expressed exclusively by differentiated, hypertrophi c chondrocytes. The mechanisms controlling collagen X expression remain lar gely unknown. Here we show that collagen X promoter activity can be induced by serum stimulation of chondrogenic MCT cells. The serum response is conf erred by a 462 nucleotide promoter fragment. Both the c-Raf/MEK/ERK and p38 MAP kinase pathways are required for this effect, whereas phosphatidylinos itol-3-kinase and protein kinase A repress promoter activation. These data are the first to demonstrate serum inducibility of the collagen X promoter and to identify signal transduction pathways involved. (C) 1999 Academic Pr ess.