Role of cAMP-dependent protein kinase during growth and early development of Dictyostelium discoideum

cAMP-dependent protein kinase (PKA) is an essential regulator of gene expre ssion and cell differentiation during multicellular development of Dictyost elium discoideum. Here we show that PKA activity also regulates gene expres sion during the growth phase and at the transition from growth to developme nt. Overexpression of PKA leads to overexpression of the discoidinl gamma p romoter, while expression of the discoidinl gamma promoter is reduced when PKA activity is reduced, either by expression of a dominant negative mutant of the regulatory subunit or by disruption of the gene for the catalytic s ubunit (PKA-C). The discoidin phenotype of PKA-C null cells is cell autonom ous. In particular, normal secretion of discoidin-inducing factors was demo nstrated. In addition, PKA-C null cells are able to respond to media condit ioned by PSF and CMF. We conclude that PKA is a major activator of discoidi n expression. However, it is not required for production or transduction of the inducing extracellular signals. Therefore, PKA-dependent and PKA-indep endent pathways regulate the expression of the discoidin genes. (C) 2000 Ac ademic Press.