Through scaffolding and catalytic actions nucleoside diphosphate kinase B differentially regulates basal and β-adrenoceptor-stimulated cAMP synthesis

beta-adrenoceptors (beta AR) play a central role in the regulation of cAMP synthesis and cardiac contractility. Nucleoside diphosphate kinase B (NDPK B) regulates cAMP signalling by complex formation with G beta gamma dimers thereby activating and stabilizing heterotrimeric G(s) proteins, key transducer of beta AR signals into the cell. Here, we explored the requirement of NDPK B for basal and beta AR-stimulated cAMP synthesis and analysed the underlying mechanisms by comparing wild-type NDPK B (WT) and its catalytically inactive H118N mutant. Stable overexpression of both WT- and H118N-NDPK B in cardiomyocyte derived H10 cells increased the plasma membrane content of G(s) and caveolin-1 and thus enhanced the isoproterenol (ISO)-stimulated cAMP-synthesis by about 2-fold. Conversely, the loss of NDPK B in embryonic fibroblasts from NDPK A/B-depleted mice was associated with a severe reduction in membranous G(s) protein and carveolin-1 content causing a marked decrease in basal and ISO-induced CAMP formation. Re-expression of NDPK B, but not of NDPK A. was able to rescue this phenotype. Both, re-expression of WT- and H118N-NDPK B induced the re-appearance of G(s) and caveolin-1 at the plasma membrane to a similar extent. Accordingly. WT- and H118N-NDPK B similarly enhanced ISO-induced cAMP formation. In contrast, the catalytically inactive H118N-NDPK B was less potent and less effective in rescuing basal CAMP production. Identical results were obtained in neonatal rat cardiac myocytes after siRNA-induced knockdown and adenoviral re-expression of NDPK B. Our data reveal that NDPK B regulates G(s) function by two different mechanisms. The complex formation of NDPK B with G(s) is required for the stabilization of the G protein content at the plasma membrane. In addition, the NDPK B-dependent phosphotransfer reaction, which requires the catalytic activity, specifically allows a receptor-independent, basal G(s) activation. (C) 2010 Elsevier Inc. All rights reserved.