Differentiation of F9 teratocarcinoma stem cells to primitive endoderm is regulated by the G(iα2)/G(sα) axis via phospholipase C and not adenylylcyclase

Morphogen-induced decline in G(1α) triggers F9 teratocarcinoma stem cells to progress to primitive endoderm via activation of protein kinase C and mitogen-activated protein kinase (Gao, P., and Malbon, C. C. (1996) J. Biol. Chem. 271, 9002-9008). Constitutive expression of G(iα2) blocks, whereas expression of G(sα) provokes, progression to primitive endoderm, permitting identification of the effectors of the response-utilizing chimera created between G(iα2) and G(sα). N-terminal substitution of G(sα) with G(iα2) sequence to create chimera G(iα2 (1-54))/G(sα) produced a chimera that activated adenylylcyclase but abolished progression to primitive endoderm and activation of phospholipase C. C-terminal substitution of G(sα) with G(iα2) sequence to G(sα)/G(iα2 (200-355)) enhanced the ability of G(sα) to promote progression. The Q205L-activated mutant of G(iα2) suppresses, whereas the G225T-activated mutant of G(sα) strongly activates phospholipase C and progression in these cells. The N-terminal region of G(sα) (residues 62-86) appears to act as a dominant switch for the G(sα)- (activation) versus G(iα2)- (suppression) mediated control of phospholipase C and progression to primitive endoderm.