Relationship between Gs alpha messenger ribonucleic acid splice variants and the molecular forms of Gs alpha protein in rat brown adipose tissue.

Recent work indicates that multiple molecular forms of Gs alpha can be produced by alternative splicing of a primary Gs alpha transcript. This study examined the pattern of expression of messenger RNAs (mRNAs) encoding the large (Gs alpha-L) and small (Gs alpha-S) molecular forms of Gs alpha in several rat tissues, including brown adipose tissue. In all tissues examined, Gs alpha-L mRNA was most abundant. This was most pronounced for brain tissue (95% of total), and least for brown adipose tissue (57%). The pattern of Gs alpha isoform expression of a given tissue was strongly correlated with the Gs alpha mRNA splicing pattern in that tissue. Cold exposure and surgical denervation are treatments that have been shown to, respectively, increase or decrease total Gs alpha mRNA in rat brown adipose tissue. Despite producing up to 4-fold differences in total Gs alpha mRNA, these treatments did not affect the proportions of Gs alpha mRNA splice variants in brown fat. In contrast, perinatal stimulation of brown fat was associated with changes in the splicing pattern of Gs alpha mRNA, and these changes were reflected in Gs alpha protein expression. Specifically, during the perinatal period Gs alpha-L mRNA increased significantly but Gs alpha-L protein levels did not change, whereas Gs alpha-S mRNA did not change and Gs alpha-S protein levels significantly declined. These data provide further evidence that the increased Gs alpha mRNA levels that occur in interscapular brown adipose tissue during periods of stimulation serve to maintain membrane levels of Gs alpha protein.