FIGURE 6.

Furin action in pituitary gonadotrope cells. Activin and furin participate in a positive feedback loop. Activin stimulation of pituitary gonadotrope cells stimulates the production of both activin B and inhibin B dimers. A differential induction of activin B (bold arrows) over inhibin B (thin arrow) is observed with activin A treatment. Only activin can stimulate the endogenous expression of furin mRNA through a Smad-dependent pathway. The increased levels of furin lead to an increase in both inhibin α- and β_B-subunit protein maturation and secretion.