G protein βγ dimer expression in cardiomyocytes: Developmental acquisition of Gβ3

Heterotrimeric G proteins are comprised of a guanine nucleotide binding Gα subunit and the Gβγ dimers that link G protein-coupled receptors (GPCRs) to effectors. This study focuses on the expression and localization patterns for certain Gβ and Gγ subunits in neonatal and adult cardiomyocytes. We identify developmental downregulation of Gβ1, Gβ2, and Gγ2, and a switch in the molecular form of Gγ3, in cardiomyocytes. Gβ1 is highly localized to caveolae membranes, whereas Gβ2 is identified in caveolae and other membrane fractions. Gβ3 is not detected in neonatal cardiomyocytes, but rather Gβ3 is upregulated in adult cardiomyocytes and detected in the caveolae and soluble fractions. The observation that cardiomyocytes co-express multiple Gβ and Gγ subunits in a developmentally regulated manner, and that these Gβ and Gγ subunits assume distinct subcellular localization patterns, provides for a high level of signaling specificity in the heart.