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 (Gsalpha) represses adipogenesis of 3T3-L1 mouse embryonic fibroblasts. Derepression occurs in response to inducers, to oligodeoxynucleotides antisense to Gsalpha, and to overexpression of heterotrimeric G-protein alpha subunit 2, inhibitory with respect to adenylyl cyclase (Gialpha2). Constitutive expression of Gsalpha blocks adipogenesis and was exploited as an assay, in which chimeras of Gialpha2 and Gsalpha were expressed stably in 3T3-L1 cells to define the region controlling adipogenesis. N-terminal analysis revealed region 146-220 of Gsalpha as a repressor of adipogenesis; substitution of Gialpha2 abolished the ability of the chimera to repress adipogenesis in response to inducers. Expression of a chimera in which the 146-235 region of Gsalpha was embedded in Gialpha2 fully repressed adipogenesis in response to the inducers. C-terminal analysis revealed no loss of function for truncated Gsalpha, lacking the terminal 38 residues. The repressor domain for adipogenesis maps to a region that includes switch domains I and II and is spatially distinct from the regions mapped for control of adenylyl cyclase.