Mitochondrial pathway of apoptosis is ancestral in metazoans.

The mitochondrial pathway of apoptosis is the major mechanism of physiological cell death in vertebrates. In this pathway, proapoptotic members of the Bcl-2 family cause mitochondrial outer membrane permeabilization (MOMP), allowing the release of cytochrome c, which interacts with Apaf-1 to trigger caspase activation and apoptosis. Despite conservation of Bcl-2, Apaf-1, and caspases in invertebrate phyla, the existence of the mitochondrial pathway in any invertebrate is, at best, controversial. Here we show that apoptosis in a lophotrochozoan, planaria (phylum Platyhelminthes), is associated with MOMP and that cytochrome c triggers caspase activation in cytosolic extracts from these animals. Further, planarian Bcl-2 family proteins can induce and/or regulate cell death in yeast and can replace Bcl-2 proteins in mammalian cells to regulate MOMP. These results suggest that the mitochondrial pathway of apoptosis in animals predates the emergence of the vertebrates but was lost in some lineages (e.g., nematodes). In further support of this hypothesis, we surveyed the ability of cytochrome c to trigger caspase activation in cytosolic extracts from a variety of organisms and found this effect in cytosolic extracts from invertebrate deuterostomes (phylum Echinodermata).

A novel AP-1 site is critical for maximal induction of the follicle-stimulating hormone beta gene by gonadotropin-releasing hormone.

Regulation of follicle-stimulating hormone (FSH) synthesis is a central point of convergence for signals controlling reproduction. The FSHbeta subunit is primarily regulated by gonadotropin-releasing hormone (GnRH), gonadal steroids, and activin. Here, we identify elements in the mouse FSHbeta promoter responsible for GnRH-mediated induction utilizing the LbetaT2 cell line that endogenously expresses FSH. The proximal 398 bp of the mouse FSHbeta promoter is sufficient for response to GnRH. This response localizes primarily to an AP-1 half-site (-72/-69) juxtaposed to a CCAAT box, which binds nuclear factor-Y. Both elements are required for AP-1 binding, creating a novel AP-1 site. Multimers of this site confer GnRH induction, and mutation or internal deletion of this site reduces GnRH induction by 35%. The same reduction was achieved using a dominant negative Fos protein. This is the only functional AP-1 site identified in the proximal 398 bp, since its mutation eliminates FSHbeta induction by c-Fos and c-Jun. GnRH regulation of the FSHbeta gene occurs through induction of multiple Fos and Jun isoforms, forming at least four different AP-1 molecules, all of which bind to this site. Mitogen-activated protein kinase activity is required for induction of FSHbeta and JunB protein. Finally, AP-1 interacts with nuclear factor-Y, which occupies its overlapping site in vivo.