REPRESSION OF ADIPOGENESIS BY ADENYLYL-CYCLASE STIMULATORY G-PROTEIN ALPHA-SUBUNIT IS EXPRESSED WITHIN REGION-146-220

The heterotrimeric G-protein alpha subunit stimulatory with respect to adenylyl cyclase (G(s alpha)) represses adipogenesis of 3T3-L1 mouse embryonic fibroblasts. Derepression occurs in response to inducers, to oligodeoxynucleotides antisense to G(s alpha), and to overexpression of heterotrimeric G-protein alpha subunit 2, inhibitory with respect t o adenylyl cyclase (G(i alpha 2)). Constitutive expression of G(s alph a) blocks adipogenesis and was exploited as an assay, in which chimera s of G(i alpha 2) and G(s alpha) were expressed stably in 3T3-L1 cells to define the region controlling adipogenesis. N-terminal analysis re vealed region 146-220 of G(s alpha) as a repressor of adipogenesis; su bstitution of G(i alpha 2) abolished the ability of the chimera to rep ress adipogenesis in response to inducers. Expression of a chimera in which the 146-235 region of G(s alpha) was embedded in G(i alpha 2) fu lly repressed adipogenesis in response to the inducers. C-terminal ana lysis revealed no loss of function for truncated G(s alpha), lacking t he terminal 38 residues. The repressor domain for adipogenesis maps to a region that includes switch domains I and II and is spatially disti nct from the regions mapped for control of adenylyl cyclase.