DIFFERENTIATION OF F9 TERATOCARCINOMA STEM-CELLS TO PRIMITIVE ENDODERM IS REGULATED BY THE G(I-ALPHA-2) G(S-ALPHA) AXIS VIA PHOSPHOLIPASE-CAND NOT ADENYLYLCYCLASE/

Morphogen-induced decline in G(i alpha) triggers F9 teratocarcinoma st em cells to progress to primitive endoderm via activation of protein k inase C and mitogen-activated protein kinase (Gao, P., and Malbon, C. C, (1996) J. Biol. Chem. 271, 9002-9008). Constitutive expression of G (i alpha 2) blocks, whereas expression of G(s alpha) provokes, progres sion to primitive endoderm, permitting identification of the effectors of the response-utilizing chimera created between G(i alpha 2) and G( s alpha). N-terminal substitution of G(s alpha) with G(i alpha 2) sequ ence to create chimera G(i alpha 2 (1-54))/G(s alpha) produced a chime ra that activated adenylylcyclase but abolished progression to primiti ve endoderm and activation of phospholipase C, C-terminal substitution of G(s alpha) with G(i alpha 2) sequence to G(s alpha)/G(i alpha 2 (3 20-355)) enhanced the ability of G(i alpha 2) to promote progression, The Q205L-activated mutant of G(i alpha 2) suppresses, whereas the G22 5T-activated mutant of G(s alpha) strongly activates phospholipase C a nd progression in these cells, The N-terminal region of G(s alpha) (re sidues 62-86) appears to act as a dominant switch for the G(s alpha)- (activation) versus G(i alpha 2)- (suppression) mediated control of ph ospholipase C and progression to primitive endoderm.