INCREASED EXPRESSION OF G(S)ALPHA ENHANCES ACTIVATION OF THE ADENYLYL-CYCLASE SIGNAL-TRANSDUCTION CASCADE

Expression of the stimulatory G protein, G(s) alpha, can vary over a 3 -fold range in human tissues and in rodent central nervous system, In fact, the offspring of alcoholics have higher levels of G(s) alpha exp ression in certain tissues compared with the offspring of nonalcoholic s, The aim of this research was to test the hypothesis that a causal r elationship exists between the level of expression of G(s) alpha and i nduction of the adenylyl cyclase (AC) cascade. The methodology employe d transient transfection of HEK 293 cells with a cDNA for the 52-kDa f orm of G(s) alpha under regulation by inducible metallothionein promot ers, Transfectants were exposed to varying concentrations (0-125 mu M) of zinc sulfate that produced a 3-fold range of membrane G(s) alpha e xpression, The range of G(s) alpha expression produced was found to mi mic a physiologically relevant spectrum of G(s) alpha expression in me mbranes derived from human tissues and rat brain, It was observed that induction of G(s) alpha expression increased constitutive as well as stimulated cAMP accumulation, Moreover, induction of G(s) alpha expres sion increased events distal to the accumulation of cAMP including the phosphorylation of the transcription factor, cAMP response element bi nding protein and transcriptional activation of cAMP-dependent reporte r genes, In summary, these studies show that the amount of G(s) alpha expression has a marked impact on the level of activity of the AC casc ade from the membrane through to the nucleus. It is hypothesized that individuals who differ in G(s) alpha expression may also differ in the expression of certain cAMP-dependent genes.