So-Yeon Kim,1 Ik-Soon Jang,1

cyclase inhibitory G protein; Gs, adenylyl cyclase stimulatory G protein; Gs, subunit of Gs; G, subunit of G protein To investigate the interaction of stimulatory GTP binding protein (Gs) pathways with others, we overexpressed wild type alpha subunit of Gs (Gs), constitutively activated R201E Gs, and dominant negative G226A Gs in COS-1 cells by transfection with DEAE-dextran, respectively. The expression of various G proteins in the transfected cells was analyzed after 72 h by quantitative Western blots, and cAMP production by stimulation with isoproterenol and forskolin was quantitated using cAMP binding proteins. The expression of Gs increased about 5-fold in the transfected cells, with concomitant increase in the small forms. However, there was no significant alteration the in the level of the alpha subunit of inhibitory G protein (Gi) and Gq, and the beta subunits of G proteins. The cAMP level without stimulation increased in the cells transfected with Gs r e g a r d l e s s to the type of mutation. Treatment with either isopro-terenol or forskolin resulted in comparable increase of the cAMP level in all the transfected cells, though the ratio to its respective basal level was smaller in the Gs-transfected cells. From this experiment, we found that the expression of the other G proteins and the signaling pathway producing cAMP did not change significantly by transiently expressing wild type, constitutively activated type, and dominant negative type of Gs. Analysis of the effects of long-term expression of Gs would contribute to better understanding on how the Gs signaling system interacts with other signaling pathways and how it adapts to the changed environments. Keywords