M J Lohse

..This real-time imaging method allows investigation of the dynamic organization and integration of multiple levels of signal processing in single living cells...

..In this issue of Molecular Cell, Mo et al. (2008) show that beta-arrestin1 also switches off signaling through the STAT1 transcription factor, thereby inhibiting interferon-induced antiviral responses...

..Taken together, our kinetic measurements demonstrate that the rate of G(S) activation limits initiation of G(S)-coupled receptor signaling...

..Our results show that a RhoA GEF can specifically interact with a GPCR and modulate its G protein signaling specificity...

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..We review here the FRET and BRET technologies that have been developed for G-protein-coupled receptors and their signaling proteins (G-proteins, effectors) and the concepts that result from such experiments...

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..Newer experimental therapeutic strategies aim at the receptor desensitization machinery and at downstream signaling steps...

..Thus, optical recording of the agonist-induced conformational change in a G-protein-coupled receptor allows the direct analysis of the intrinsic efficacies of agonists...

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..Using these methods, we show that receptor activation by agonists and signalling to G-proteins occur on the subsecond time scale, whereas receptor desensitization is limited by receptor phosphorylation and proceeds more slowly...

..Here, we review the latter approach as a tool to study receptor activation and the levels of the second messengers cAMP and cGMP in intact cells...

..This review summarizes recent findings illustrating the speed and the complexity of this signalling system...

..They are also raising controversial issues, such as whether or not receptors and G proteins are pre-coupled and whether G proteins dissociate during activation...

..However, dimerization may serve to affect receptor mobility at the cell surface and in intracellular trafficking, and may be involved in and affect their signaling functions...

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..Furthermore, PTHR sequestration does not appear to require G protein activation...

..Determinants in the receptor's core (Asn-289 and Lys-382) appear to regulate internalization of the receptor/beta-arrestin complex toward early endocytic endosomes during the initial step of endocytosis...

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..The discovery of subtype-selective mechanisms of G protein activation illustrates that G protein subfamilies have specific mechanisms of activation that may provide a previously unknown basis for G protein signaling specificity...

..We conclude that thrombin causes the synthesis of prostacyclin in endothelial cells and that the subsequent stimulation of Gs-coupled prostacyclin receptors then results in an increase in [cAMP]...

..Together, these findings show that phosducin is a previously unrecognized target of SUMO modification and that SUMOylation controls phosducin stability in cells as well as its functional properties...

..Taken together, these results implicate a Ca(2+)-mediated inhibition of AC5 and 6 as an important mechanism of purinergic receptor-induced decline of cAMP and show a direct cross talk of these signaling pathways in VSMCs...

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..Thus, we conclude that P2Y(1)-receptor desensitization and internalization are mediated by different phosphorylation sites and kinases...

..Our data reveal that in adult cardiac myocytes, beta(1)ARs induce far-reaching cAMP signals, whereas beta(2)AR-induced cAMP remains locally confined...

..These specific mixtures of agonism, antagonism, and inverse agonism at different subtypes may have important implications for the therapeutic use of the respective compounds...

..This fast agonist-controlled association and dissociation of beta-arrestins from prephosphorylated receptors should permit rapid control of receptor sensitivity in repeatedly stimulated cells such as neurons...

..We propose that this FRAP method can be widely applied to study di- or oligomerization of cell-surface proteins...

..This technique can be widely used to assess the contribution of various pituitary receptors, including individual G(i) protein-coupled somatostatin receptors, to the regulation of cAMP levels under physiologically relevant settings...

..Our experiments show that the C terminus distal to residue 381 does not affect the initial interaction between receptor and beta-arrestin, but its last eight amino acids facilitate receptor internalization in concert with beta-arrestin2...

..Thus, FRET from CFP to FlAsH reports GPCR activation in living cells without disturbing receptor function and shows that the small size of the tetracysteine-biarsenical tag can be decisively advantageous...

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..We therefore conclude that the strong inhibitory action of PhLP(S) on Gbetagamma signaling is the result of a previously unrecognized mechanism of Gbetagamma-regulation, inhibition of Gbetagamma-folding by interference with TCP-1alpha...

..We investigated whether autoantibodies against the human beta-adrenergic receptor (beta-AR) might be involved in cardiomyopathies secondary to valvular heart disease (VHD) or hypertensive heart disease (HHD)...

..Instead the knock down of the predominant subtype AC6 in HUVECs provided the first direct evidence that the Ca(2+)-mediated inhibition of AC6 accounts for the thrombin-induced decrease in cAMP levels...

..Our study attempted to gain further understanding of the allosteric effects of human autoantibodies on beta1-adrenergic receptor (beta1-AR) function...

..This may be interpreted as an adaptive mechanism making energy transduction via CK more efficient at times of increased metabolic demand...

..In this review we will summarize recent progress in biophysical approaches that have led to the current understanding of conformational changes that occur during GPCR activation...

..This study shows that MRI can demonstrate loss of inotropic and lusitropic response in mice with MI and can unmask diastolic dysfunction as an early sign of cardiac dysfunction in a transgenic mouse model of heart failure...

..This article reviews current knowledge and recent experimental and clinical findings focusing on the role of the beta(1)-adrenergic receptor as a self-antigen in the pathogenesis of DCM...

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..In this review, we describe and compare these techniques in terms of their robustness, sensitivity and spatio-temporal resolution...

..This suggests that the two different agonists induce distinct active states of this receptor that show differential interactions with beta-arrestins...

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..This switch couples inverse agonist binding to the suppression of activity in the receptor...

..This study sought to develop a rapid method for the detection of activating autoantibodies directed against the beta1-adrenoceptor (anti-beta1-Abs) in patients with heart failure...

..Taken together, our data indicate that FRET-based assays of G-protein activation can serve to determine the abilities of compounds to activate G-protein signaling directly and in living cells...

..It revealed that beta(1)-AR variants dramatically differ in their responses to diverse beta blockers, with possible consequences for their clinical use...

..We propose that specific phosphorylation events on ERK1/2 integrate differing upstream signals (Raf1-MEK1/2 or G protein-coupled receptor-G(q)) to induce cardiac hypertrophy...

..We investigated whether genetic modification of calcium handling through deletion of phospholamban in mice would affect the development of heart failure in mice with transgenic overexpression of the beta1-adrenergic receptor...

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..A processed form of the PTHR was also detected in human kidney. These findings suggest a new model of PTHR processing and regulation of its stability...

..This short review will discuss new mechanistic insights into ERK1/2-dependent development of cardiac hypertrophy and the prospect to translate this knowledge into future therapeutic strategies...

..Although carried out in an experimental animal model, our findings should further encourage the development of therapeutic strategies that combat harmful anti-beta(1)-EC(II) in receptor Ab-positive DCM patients...

..In addition to the known reduction in receptor number (down-regulation) as underlying mechanism, uncoupling of the receptor from the stimulatory G protein G(s) was identified...

..Elimination by (extracorporeal) immunoadsorption or direct neutralization of the harmful receptor autoantibodies in the circulating blood represent promising strategies to protect the heart from beta1-(auto)antibody-induced damage...

..We propose that current models of GPCR signaling should be revised to accommodate the ability of receptors to change their signaling properties depending on their subcellular localization...

..Based on these findings, we propose a revision of the current model of the GPCR-cAMP signaling pathway to accommodate receptor signaling at endosomes...

..Here, we investigated whether PLN exhibits cardiotoxic effects via mechanisms other than chronic inhibition of SERCA2a by studying a PLN mutant, PLN(R9C), that triggers cardiac failure in humans and mice...

..This finding will be of particular interest for unraveling Gbetagamma-induced signaling pathways...

..Thus, the paradoxical block of PTH release under magnesium deficiency seems to be mediated through a novel mechanism involving an increase in the activity of G alpha subunits of heterotrimeric G-proteins...

..These data suggest that classical paradigms of GPCR signaling may need revision, as they indicate that cAMP signaling by GPCRs may occur both at the cell surface and from intracellular sites, but with different consequences for the cell...

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..The following article will summarize the so far available evidence for an implication of a confined number of harmful autoantibodies directed against specific cardiac antigens in the pathogenesis of DCM...

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..The temporal and spatial resolution attained with the new sensors is superior to that of existing techniques, and permits direct recording and imaging of rapid cGMP-signaling events...

..These data suggest that the conformational change that switches the receptor into its active state proceeds in a sequential manner, with the first rapid binding step event preceding receptor activation by PTH(1-34)...

..A major role for PKC and beta-arrestins in preferential regulation of PTHR-mediated G(q) signaling by independent mechanisms at the receptor level was established...

..This approach allows the comparison of agonist and partial agonist intrinsic activities at the receptor level and provides evidence for millisecond activation times of GPCRs...

..Short-loop feedback inhibition of epinephrine release from the adrenal gland may represent a novel therapeutic target for diseases that arise from enhanced adrenergic stimulation...

..Our data suggest that alpha(2A)-adrenergic receptors and G proteins interact by rapid collision coupling and indicate that there is no significant precoupling between these receptors and G proteins...

..Thus, the amino-terminal domain of GRK2 is a previously unrecognized Gbetagamma binding site that regulates GRK2-mediated receptor phosphorylation and inhibits Gbetagamma-stimulated signaling...

..This inhibition was almost completely abolished in vitro when GRK2 was phosphorylated by PKC. These data suggest that calmodulin may be an inhibitor of GRK2 whose effects can be abolished with PKC-mediated phosphorylation of GRK2...

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..We propose that this method may be widely applied to label intracellular proteins and to study their interactions in intact cells with minimal disturbance of their function...

..These findings suggest a model in which NHERF1 may serve as an adaptor, bringing β-arrestin2 into close proximity to the PTHR, thereby facilitating β-arrestin2 recruitment after receptor activation...

..These findings demonstrate that specific peptides can inhibit GRKs in the submicromolar range and suggest that a further decrease in size is possible without losing the inhibitory potency...

..These findings implicate the Nab1-Egr1 axis as a crucial regulator of pathological cardiac growth...

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..A physiological role for this mechanism is shown in cardiomyocytes in which the downregulation of RKIP restrains beta-adrenergic signalling and contractile activity...

..It allows to sense cAMP gradients around particular PDE molecules and to study the pharmacological effects of selective inhibitors on localized cAMP signalling...

..Furthermore, they indicate that Asn293 is a key residue in transferring conformational information from the agonist-binding site to the intracellular surface...

..We conclude that overexpression of beta1-adrenergic receptors in the heart may lead to a short-lived improvement of cardiac function, but that increased beta1-adrenergic receptor signalling is ultimately detrimental...

..The data provide a new key characteristic underlying the mechanism of partial agonism at G-protein-coupled receptors...

..These results suggest that the depressed molecular function in cardiac myosin may initiate the events that cause the heart to remodel and become pathologically dilated...

..They have produced a number of unexpected results: fast receptor activation kinetics in the millisecond range, similarly fast kinetics for receptor-G protein interactions, but much slower activation kinetics for G protein activation...

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..Our findings support a functional role for caspase-1-mediated myocardial apoptosis contributing to the progression of heart failure...

..Taken together, we suggest a mechanism whereby syntaxin and G protein betagamma subunits interact concomitantly with a Kv channel to regulate its inactivation...

..The results demonstrate that Ena-VASP proteins may play an important role in intercalated disk function at the interface between cardiac myocytes...

..This allows receptor stimulation to regulate cAMP activity over concentration ranges appropriate for modulating both higher (e.g., PKA) and lower affinity (e.g., Epac) effectors...

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..PDE3 and PDE4 localize to distinct compartments and this may underpin their different functional roles. Our findings indicate the importance of distinctly localized PDE isoenzymes in determining compartmentalized cAMP signaling...

..Specifically, it experimentally confirms the longstanding hypothesis that PDF is a direct modulator of most neurons in the Drosophila clock network...

..Moreover, triadin 1 appears to anchor calsequestrin to the ryanodine receptor...