Abstract 3575: Interaction of Nucleoside Diphosphate Kinase B With Gβγ Dimers Controls Heterotrimeric G Protein Function
Heterotrimeric G proteins in heart function and heart disease have been extensively studied so far. However, little is known about mechanisms regulating the cellular content and compartmentalization of G proteins. Here, we show that the interaction of nucleoside diphosphate kinase B (NDPK B) with the G protein βγ-dimer (Gβγ) is required for G protein function in vivo. In zebrafish embryos, morpholino-mediated knockdown (KD) of zebrafish NDPK B, but not NDPK A, results in a severe decrease in cardiac contractility (ventricular fractional shortening of control vs. KD fish: 25±3% vs. 5±3%). The depletion of NDPK B is associated with a drastic reduction in Gβ1γ2 dimer expression and the basal cAMP content of zebrafish hearts (cAMP of control vs. KD heart: 1,5±0,2 fmol/fish vs. 0,5±0,2 fmol/fish). Moreover, the protein levels of the adenylyl cyclase (AC)-regulating Gαs and Gαi subunits as well as the caveolae scaffold proteins caveolin-1 and −3 are strongly reduced. In addition, the knockdown of the zebrafish Gβ1 orthologs, Gβ1 and Gβ1like, causes a cardiac phenotype very similar to that of NDPK B morphants. The loss of Gβ1/Gβ1like is associated with a down-regulation in caveolins, AC-regulating Gα-subunits, and most importantly, NDPK B. A comparison of embryonic fibroblasts from wild-type and NDPK A/B knockout (KO) mice demonstrate a similar reduction of G protein, caveolin-1 and basal cAMP content (cAMP of wild-type vs. KO: 71±4 pmol/mg vs. 28±5 pmol/mg) in mammalian cells that can be rescued by expression of human NDPK B. Thus, our results define a novel role for the interaction of NDPK B with Gβγ-dimers and caveolins in regulating membranous G protein content and maintaining normal cardiac G protein function in vivo.