Identification of avian sarcoplasmic reticulum Ca2+-ATPase (SERCA3) as a novel 1,25(OH)(2)D-3 target gene in the monocytic lineage

Osteoclasts are postmitotic, multinucleated giant cells generated by the fu sion of hematopoietic mononuclear precursors from the monocyte-macrophage l ineage. In culture, adherent macrophages from blood-derived monocytes grow, gather, and fuse together to form multinucleated osteoclast-like cells. Th ese events are controlled by 1,25(OH)(2)D-3. To sort out new 1,25(OH)(2)D-3 target genes involved in osteoclast differentiation, we have performed an RT-PCR differential display using mRNA from macrophages induced for 10 h by 1,25(OH)(2)D-3 compared to nontreated cells. We have identified a new targ et gene, a chick ATP-dependent Ca2+ pump, ChkSERCA3. Although the level of the corresponding transcript increases during the differentiation process f rom macrophages to osteoclastlike cells, its steady-state level is downregu lated by hormone treatment. The action of 1,25(OH)(2)D-3 on the Ca2+-ATPase gene expression is independent of de novo protein synthesis and is hormone dose dependent. This expression in adult chick was restricted to the hemat opoietic cell lineage, spleen, lung, intestine, and brain, whereas no expre ssion was detected in embryos. The function of the protein can be predicted from its high homology with the other members of the SR ATP-dependent Ca2 pump family, i.e., storage and control of cytosolic Ca2+ directly regulate d by 1,25(OH)(2)D-3, further supporting the critical role for intracellular calcium in highly specialized cells such as osteoclasts. (C) 1999 Academic Press.