76
|
Lampert KP, Schmidt C, Fischer P, Volff JN, Hoffmann C, Muck J, Lohse MJ, Ryan MJ, Schartl M. Determination of onset of sexual maturation and mating behavior by melanocortin receptor 4 polymorphisms. Curr Biol 2010; 20:1729-34. [PMID: 20869245 DOI: 10.1016/j.cub.2010.08.029] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2010] [Revised: 07/16/2010] [Accepted: 08/13/2010] [Indexed: 11/30/2022]
Abstract
Polymorphisms in reproductive strategies are among the most extreme and complex in nature. A prominent example is male body size and the correlated reproductive strategies in some species of platyfish and swordtails of the genus Xiphophorus. This polymorphism is controlled by a single Mendelian locus (P) that determines the onset of sexual maturity of males. Because males cease growth after reaching puberty, this results in a marked size polymorphism. The different male size classes show pronounced behavioral differences (e.g., courtship versus sneak mating), and females prefer large over small males. We show that sequence polymorphisms of the melanocortin receptor 4 gene (mc4r) comprise both functional and non-signal-transducing versions and that variation in copy number of mc4r genes on the Y chromosome underlies the P locus polymorphism. Nonfunctional Y-linked mc4r copies in larger males act as dominant-negative mutations and delay the onset of puberty. Copy number variation, as a regulating mechanism, endows this system with extreme genetic flexibility that generates extreme variation in phenotype. Because Mc4r is critically involved in regulation of body weight and appetite, a novel link between the physiological system controlling energy balance and the regulation of reproduction becomes apparent.
Collapse
|
77
|
Reiner S, Ambrosio M, Hoffmann C, Lohse MJ. Differential signaling of the endogenous agonists at the beta2-adrenergic receptor. J Biol Chem 2010; 285:36188-98. [PMID: 20837485 DOI: 10.1074/jbc.m110.175604] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The concept of "functional selectivity" or "biased signaling" suggests that a ligand can have distinct efficacies with regard to different signaling pathways. We have investigated the question of whether biased signaling may be related to distinct agonist-induced conformational changes in receptors using the β(2)-adrenergic receptor (β(2)AR) and its two endogenous ligands epinephrine and norepinephrine as a model system. Agonist-induced conformational changes were determined in a fluorescently tagged β(2)AR FRET sensor. In this β(2)AR sensor, norepinephrine caused signals that amounted to only ≈50% of those induced by epinephrine and the standard "full" agonist isoproterenol. Furthermore, norepinephrine-induced changes in the β(2)AR FRET sensor were slower than those induced by epinephrine (rate constants, 47 versus 128 ms). A similar partial β(2)AR activation signal was revealed for the synthetic agonists fenoterol and terbutaline. However, norepinephrine was almost as efficient as epinephrine (and isoproterenol) in causing activation of G(s) and adenylyl cyclase. In contrast, fenoterol was quite efficient in triggering β-arrestin2 recruitment to the cell surface and its interaction with β(2)AR, as well as internalization of the receptors, whereas norepinephrine caused partial and slow changes in these assays. We conclude that partial agonism of norepinephrine at the β(2)AR is related to the induction of a different active conformation and that this conformation is efficient in signaling to G(s) and less efficient in signaling to β-arrestin2. These observations extend the concept of biased signaling to the endogenous agonists of the β(2)AR and link it to distinct conformational changes in the receptor.
Collapse
|
78
|
Jacobs S, Calebiro D, Nikolaev VO, Lohse MJ, Schulz S. Real-time monitoring of somatostatin receptor-cAMP signaling in live pituitary. Endocrinology 2010; 151:4560-5. [PMID: 20610560 DOI: 10.1210/en.2010-0341] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Fluorescence resonance energy transfer using genetically encoded biosensors has proven to be a powerful technique to monitor the spatiotemporal dynamics of cAMP signals stimulated by G(s)-coupled receptors in living cells. In contrast, real-time imaging of G(i)-mediated cAMP signals under native conditions remains challenging. Here, we describe the use of transgenic mice for cAMP imaging in living pituitary slices and primary pituitary cells. 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.
Collapse
|
79
|
Ambrosio M, Zürn A, Lohse MJ. Sensing G protein-coupled receptor activation. Neuropharmacology 2010; 60:45-51. [PMID: 20727363 DOI: 10.1016/j.neuropharm.2010.08.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Accepted: 08/07/2010] [Indexed: 11/25/2022]
Abstract
G protein-coupled receptors (GPCRs) are the key elements of a highly regulated transduction machinery that generates different signaling outcomes to hormones and neurotransmitters. Until recently, it was assumed that diverse ligands of a given GPCR differ only in their ability to alter the balance between the OFF and the ON state of the receptor. However, it has now become evident that their activation mechanisms are more complex and that receptors presumably display distinguishable active conformational states, which are induced by different agonists and correlate to specific signaling outputs. The use of different labeling strategies to insert fluorescent labels into purified, reconstituted receptors, or into receptors in intact cells, has made it possible to sense receptor activation via changes in their fluorescence. Here, we summarize recent progress in the analysis of agonist-dependent activation mechanisms of GPCRs acquired using modern spectroscopic and crystallographic techniques.
Collapse
|
80
|
|
81
|
Klenk C, Vetter T, Zürn A, Vilardaga JP, Friedman PA, Wang B, Lohse MJ. Formation of a ternary complex among NHERF1, beta-arrestin, and parathyroid hormone receptor. J Biol Chem 2010; 285:30355-62. [PMID: 20656684 DOI: 10.1074/jbc.m110.114900] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
β-Arrestins are crucial regulators of G-protein coupled receptor (GPCR) signaling, desensitization, and internalization. Despite the long-standing paradigm that agonist-promoted receptor phosphorylation is required for β-arrestin2 recruitment, emerging evidence suggests that phosphorylation-independent mechanisms play a role in β-arrestin2 recruitment by GPCRs. Several PDZ proteins are known to interact with GPCRs and serve as cytosolic adaptors to modulate receptor signaling and trafficking. Na(+)/H(+) exchange regulatory factors (NHERFs) exert a major role in GPCR signaling. By combining imaging and biochemical and biophysical methods we investigated the interplay among NHERF1, β-arrestin2, and the parathyroid hormone receptor type 1 (PTHR). We show that NHERF1 and β-arrestin2 can independently bind to the PTHR and form a ternary complex in cultured human embryonic kidney cells and Chinese hamster ovary cells. Although NHERF1 interacts constitutively with the PTHR, β-arrestin2 binding is promoted by receptor activation. NHERF1 interacts directly with β-arrestin2 without using the PTHR as an interface. Fluorescence resonance energy transfer studies revealed that the kinetics of PTHR and β-arrestin2 interactions were modulated by NHERF1. 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.
Collapse
|
82
|
Calebiro D, Nikolaev VO, Lohse MJ. Imaging of persistent cAMP signaling by internalized G protein-coupled receptors. J Mol Endocrinol 2010; 45:1-8. [PMID: 20378719 DOI: 10.1677/jme-10-0014] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
G protein-coupled receptors (GPCRs) are the largest family of plasma membrane receptors. They mediate the effects of several endogenous cues and serve as important pharmacological targets. Although many biochemical events involved in GPCR signaling have been characterized in great detail, little is known about their spatiotemporal dynamics in living cells. The recent advent of optical methods based on fluorescent resonance energy transfer allows, for the first time, to directly monitor GPCR signaling in living cells. Utilizing these methods, it has been recently possible to show that the receptors for two protein/peptide hormones, the TSH and the parathyroid hormone, continue signaling to cAMP after their internalization into endosomes. This type of intracellular signaling is persistent and apparently triggers specific cellular outcomes. Here, we review these recent data and explain the optical methods used for such studies. Based on these findings, we propose a revision of the current model of the GPCR-cAMP signaling pathway to accommodate receptor signaling at endosomes.
Collapse
|
83
|
Wachten S, Masada N, Ayling LJ, Ciruela A, Nikolaev VO, Lohse MJ, Cooper DMF. Distinct pools of cAMP centre on different isoforms of adenylyl cyclase in pituitary-derived GH3B6 cells. J Cell Sci 2010; 123:95-106. [PMID: 20016070 DOI: 10.1242/jcs.058594] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Microdomains have been proposed to explain specificity in the myriad of possible cellular targets of cAMP. Local differences in cAMP levels can be generated by phosphodiesterases, which control the diffusion of cAMP. Here, we address the possibility that adenylyl cyclases, the source of cAMP, can be primary architects of such microdomains. Distinctly regulated adenylyl cyclases often contribute to total cAMP levels in endogenous cellular settings, making it virtually impossible to determine the contribution of a specific isoform. To investigate cAMP dynamics with high precision at the single-isoform level, we developed a targeted version of Epac2-camps, a cAMP sensor, in which the sensor was tagged to a catalytically inactive version of the Ca(2+)-stimulable adenylyl cyclase 8 (AC8). This sensor, and less stringently targeted versions of Epac2-camps, revealed opposite regulation of cAMP synthesis in response to Ca(2+) in GH(3)B(6) pituitary cells. Ca(2+) release triggered by thyrotropin-releasing hormone stimulated the minor endogenous AC8 species. cAMP levels were decreased by inhibition of AC5 and AC6, and simultaneous activation of phosphodiesterases, in different compartments of the same cell. These findings demonstrate the existence of distinct adenylyl-cyclase-centered cAMP microdomains in live cells and open the door to their molecular micro-dissection.
Collapse
|
84
|
Khelashvili G, Dorff K, Shan J, Camacho-Artacho M, Skrabanek L, Vroling B, Bouvier M, Devi LA, George SR, Javitch JA, Lohse MJ, Milligan G, Neubig RR, Palczewski K, Parmentier M, Pin JP, Vriend G, Campagne F, Filizola M. GPCR-OKB: the G Protein Coupled Receptor Oligomer Knowledge Base. ACTA ACUST UNITED AC 2010; 26:1804-5. [PMID: 20501551 DOI: 10.1093/bioinformatics/btq264] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
SUMMARY Rapid expansion of available data about G Protein Coupled Receptor (GPCR) dimers/oligomers over the past few years requires an effective system to organize this information electronically. Based on an ontology derived from a community dialog involving colleagues using experimental and computational methodologies, we developed the GPCR-Oligomerization Knowledge Base (GPCR-OKB). GPCR-OKB is a system that supports browsing and searching for GPCR oligomer data. Such data were manually derived from the literature. While focused on GPCR oligomers, GPCR-OKB is seamlessly connected to GPCRDB, facilitating the correlation of information about GPCR protomers and oligomers. AVAILABILITY AND IMPLEMENTATION The GPCR-OKB web application is freely available at http://www.gpcr-okb.org
Collapse
|
85
|
Deubner N, Berliner D, Schlipp A, Gelbrich G, Caforio ALP, Felix SB, Fu M, Katus H, Angermann CE, Lohse MJ, Ertl G, Störk S, Jahns R. Cardiac beta1-adrenoceptor autoantibodies in human heart disease: rationale and design of the Etiology, Titre-Course, and Survival (ETiCS) Study. Eur J Heart Fail 2010; 12:753-62. [PMID: 20494925 DOI: 10.1093/eurjhf/hfq072] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
AIMS Evidence for a pathophysiologic relevance of autoimmunity in human heart disease has substantially increased over the past years. Conformational autoantibodies stimulating the cardiac beta1-adrenoceptor (beta1-aabs) are considered of importance in heart failure development and clinical pilot studies have shown their prognostic significance in human 'idiopathic' cardiomyopathy. METHODS We recently developed a novel highly sensitive fluorescence-based functional assay to detect stimulating beta1-aabs. We will use this method to assess Etiology, Titre-Course, and effect on Survival (ETiCS) of beta1-aabs in a prospective multicentre study with serial follow-up of patients after a first acute myocarditis or myocardial infarction. Several European core laboratories will jointly study the hypothesis that both disorders may trigger autoimmune reactions leading to the generation of beta1-aabs and/or other heart-directed aabs. Further, sera from healthy controls and well-characterized patient cohorts with dilated, ischaemic, or hypertensive cardiomyopathy will be analysed retrospectively for beta1-aab prevalence, incidence, persistence, and/or clearance. CONCLUSION ETiCS is so far the largest clinical diagnostic study projected to address cardiac autoimmunity. It attempts to unravel the pathophysiology of cardiac autoantibody formation and persistence/clearance. ETiCS will enhance current knowledge on autoimmunity in human heart disease and promote endeavours to develop novel therapies targeting cardiac aabs.
Collapse
|
86
|
Zürn A, Klenk C, Zabel U, Reiner S, Lohse MJ, Hoffmann C. Site-Specific, Orthogonal Labeling of Proteins in Intact Cells with Two Small Biarsenical Fluorophores. Bioconjug Chem 2010; 21:853-9. [DOI: 10.1021/bc900394j] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
87
|
Volpe S, Thelen S, Pertel T, Lohse MJ, Thelen M. Polarization of migrating monocytic cells is independent of PI 3-kinase activity. PLoS One 2010; 5:e10159. [PMID: 20419163 PMCID: PMC2855346 DOI: 10.1371/journal.pone.0010159] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2009] [Accepted: 03/23/2010] [Indexed: 11/20/2022] Open
Abstract
Background Migration of mammalian cells is a complex cell type and environment specific process. Migrating hematopoietic cells assume a rapid amoeboid like movement when exposed to gradients of chemoattractants. The underlying signaling mechanisms remain controversial with respect to localization and distribution of chemotactic receptors within the plasma membrane and the role of PI 3-kinase activity in cell polarization. Methodology/Principal Findings We present a novel model for the investigation of human leukocyte migration. Monocytic THP-1 cells transfected with the α2A-adrenoceptor (α2AAR) display comparable signal transduction responses, such as calcium mobilization, MAP-kinase activation and chemotaxis, to the noradrenaline homlogue UK 14'304 as when stimulated with CCL2, which binds to the endogenous chemokine receptor CCR2. Time-lapse video microcopy reveals that chemotactic receptors remain evenly distributed over the plasma membrane and that their internalization is not required for migration. Measurements of intramolecular fluorescence resonance energy transfer (FRET) of α2AAR-YFP/CFP suggest a uniform activation of the receptors over the entire plasma membrane. Nevertheless, PI 3-kinse activation is confined to the leading edge. When reverting the gradient of chemoattractant by moving the dispensing micropipette, polarized monocytes – in contrast to neutrophils – rapidly flip their polarization axis by developing a new leading edge at the previous posterior side. Flipping of the polarization axis is accompanied by re-localization of PI-3-kinase activity to the new leading edge. However, reversal of the polarization axis occurs in the absence of PI 3-kinase activation. Conclusions/Significance Accumulation and internalization of chemotactic receptors at the leading edge is dispensable for cell migration. Furthermore, uniformly distributed receptors allow the cells to rapidly reorient and adapt to changes in the attractant cue. Polarized monocytes, which display typical amoeboid like motility, can rapidly develop a new leading edge facing the highest chemoattractant concentration at any site of the plasma membrane, including the uropod. The process appears to be independent of PI 3-kinase activity.
Collapse
|
88
|
Calebiro D, Nikolaev VO, Persani L, Lohse MJ. Signaling by internalized G-protein-coupled receptors. Trends Pharmacol Sci 2010; 31:221-8. [PMID: 20303186 DOI: 10.1016/j.tips.2010.02.002] [Citation(s) in RCA: 194] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2009] [Revised: 02/01/2010] [Accepted: 02/11/2010] [Indexed: 01/27/2023]
Abstract
G-protein-coupled receptors (GPCRs) are cell surface receptors and are generally assumed to signal to second messengers such as cyclic AMP (cAMP) exclusively from the plasma membrane. However, recent studies indicate that GPCRs can continue signaling to cAMP after internalization together with their agonists. Signaling from inside the cell is persistent and appears to trigger specific downstream effects. Here, we will review these recent data, which form the basis for a novel concept of intracellular GPCR signaling and suggest new and intriguing scenarios for the functions of GPCRs in the endocytic compartment. 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.
Collapse
|
89
|
Nikolaev VO, Moshkov A, Lyon AR, Miragoli M, Novak P, Paur H, Lohse MJ, Korchev YE, Harding SE, Gorelik J. Beta2-adrenergic receptor redistribution in heart failure changes cAMP compartmentation. Science 2010; 327:1653-7. [PMID: 20185685 DOI: 10.1126/science.1185988] [Citation(s) in RCA: 420] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The beta1- and beta2-adrenergic receptors (betaARs) on the surface of cardiomyocytes mediate distinct effects on cardiac function and the development of heart failure by regulating production of the second messenger cyclic adenosine monophosphate (cAMP). The spatial localization in cardiomyocytes of these betaARs, which are coupled to heterotrimeric guanine nucleotide-binding proteins (G proteins), and the functional implications of their localization have been unclear. We combined nanoscale live-cell scanning ion conductance and fluorescence resonance energy transfer microscopy techniques and found that, in cardiomyocytes from healthy adult rats and mice, spatially confined beta2AR-induced cAMP signals are localized exclusively to the deep transverse tubules, whereas functional beta1ARs are distributed across the entire cell surface. In cardiomyocytes derived from a rat model of chronic heart failure, beta2ARs were redistributed from the transverse tubules to the cell crest, which led to diffuse receptor-mediated cAMP signaling. Thus, the redistribution of beta(2)ARs in heart failure changes compartmentation of cAMP and might contribute to the failing myocardial phenotype.
Collapse
|
90
|
Lohse MJ. Dimerization in GPCR mobility and signaling. Curr Opin Pharmacol 2010; 10:53-8. [DOI: 10.1016/j.coph.2009.10.007] [Citation(s) in RCA: 130] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2009] [Revised: 10/06/2009] [Accepted: 10/07/2009] [Indexed: 11/28/2022]
|
91
|
Lompré AM, Hajjar RJ, Harding SE, Kranias EG, Lohse MJ, Marks AR. Ca2+ cycling and new therapeutic approaches for heart failure. Circulation 2010; 121:822-30. [PMID: 20124124 DOI: 10.1161/circulationaha.109.890954] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
92
|
Maier-Peuschel M, Frölich N, Dees C, Hommers LG, Hoffmann C, Nikolaev VO, Lohse MJ. A fluorescence resonance energy transfer-based M2 muscarinic receptor sensor reveals rapid kinetics of allosteric modulation. J Biol Chem 2010; 285:8793-800. [PMID: 20083608 DOI: 10.1074/jbc.m109.098517] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Allosteric modulators have been identified for several G protein-coupled receptors, most notably muscarinic receptors. To study their mechanism of action, we made use of a recently developed technique to generate fluorescence resonance energy transfer (FRET)-based sensors to monitor G protein-coupled receptor activation. Cyan fluorescent protein was fused to the C terminus of the M(2) muscarinic receptor, and a specific binding sequence for the small fluorescent compound fluorescein arsenical hairpin binder, FlAsH, was inserted into the third intracellular loop; the latter site was labeled in intact cells by incubation with FlAsH. We then measured FRET between the donor cyan fluorescent protein and the acceptor FlAsH in intact cells and monitored its changes in real time. Agonists such as acetylcholine and carbachol induced rapid changes in FRET, indicative of agonist-induced conformational changes. Removal of the agonists or addition of an antagonist caused a reversal of this signal with rate constants between 400 and 1100 ms. The allosteric ligands gallamine and dimethyl-W84 caused no changes in FRET when given alone, but increased FRET when given in the presence of an agonist, compatible with an inactivation of the receptors. The kinetics of these effects were very rapid, with rate constants of 80-100 ms and approximately 200 ms for saturating concentrations of gallamine and dimethyl-W84, respectively. Because these speeds are significantly faster than the responses to antagonists, these data indicate that gallamine and dimethyl-W84 are allosteric ligands and actively induce a conformation of the M(2) receptor with a reduced affinity for its agonists.
Collapse
|
93
|
Klenk C, Schulz S, Calebiro D, Lohse MJ. Agonist-regulated cleavage of the extracellular domain of parathyroid hormone receptor type 1. J Biol Chem 2010; 285:8665-74. [PMID: 20080964 DOI: 10.1074/jbc.m109.058685] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The receptor for parathyroid hormone (PTHR) is a main regulator of calcium homeostasis and bone maintenance. As a member of class B of G protein-coupled receptors, it harbors a large extracellular domain, which is required for ligand binding. Here, we demonstrate that the PTHR extracellular domain is cleaved by a protease belonging to the family of extracellular metalloproteinases. We show that the cleavage takes place in a region of the extracellular domain that belongs to an unstructured loop connecting the ligand-binding parts and that the N-terminal 10-kDa fragment is connected to the receptor core by a disulfide bond. Cleaved receptor revealed reduced protein stability compared with noncleaved receptor, suggesting degradation of the whole receptor. In the presence of the agonistic peptides PTH(1-34), PTH(1-14), or PTH(1-31), the processing of the PTHR extracellular domain was inhibited, and receptor protein levels were stabilized. 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.
Collapse
|
94
|
Beetz N, Harrison MD, Brede M, Zong X, Urbanski MJ, Sietmann A, Kaufling J, Lorkowski S, Barrot M, Seeliger MW, Vieira-Coelho MA, Hamet P, Gaudet D, Seda O, Tremblay J, Kotchen TA, Kaldunski M, Nüsing R, Szabo B, Jacob HJ, Cowley AW, Biel M, Stoll M, Lohse MJ, Broeckel U, Hein L. Phosducin influences sympathetic activity and prevents stress-induced hypertension in humans and mice. J Clin Invest 2010; 119:3597-3612. [PMID: 19959875 DOI: 10.1172/jci38433] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2009] [Accepted: 09/30/2009] [Indexed: 12/13/2022] Open
Abstract
Hypertension and its complications represent leading causes of morbidity and mortality. Although the cause of hypertension is unknown in most patients, genetic factors are recognized as contributing significantly to an individual's lifetime risk of developing the condition. Here, we investigated the role of the G protein regulator phosducin (Pdc) in hypertension. Mice with a targeted deletion of the gene encoding Pdc (Pdc-/- mice) had increased blood pressure despite normal cardiac function and vascular reactivity, and displayed elevated catecholamine turnover in the peripheral sympathetic system. Isolated postganglionic sympathetic neurons from Pdc-/- mice showed prolonged action potential firing after stimulation with acetylcholine and increased firing frequencies during membrane depolarization. Furthermore, Pdc-/- mice displayed exaggerated increases in blood pressure in response to post-operative stress. Candidate gene-based association studies in 2 different human populations revealed several SNPs in the PDC gene to be associated with stress-dependent blood pressure phenotypes. Individuals homozygous for the G allele of an intronic PDC SNP (rs12402521) had 12-15 mmHg higher blood pressure than those carrying the A allele. These findings demonstrate that PDC is an important modulator of sympathetic activity and blood pressure and may thus represent a promising target for treatment of stress-dependent hypertension.
Collapse
|
95
|
Zürn A, Klenk C, Zabel U, Lohse MJ, Hoffmann C. Site-Specific, Orthogonal Two Color Labeling of Different Proteins with Flash and Reash in Living Cells. Biophys J 2010. [DOI: 10.1016/j.bpj.2009.12.2122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
|
96
|
von Hayn K, Werthmann RC, Nikolaev VO, Hommers LG, Lohse MJ, Bünemann M. Gq-mediated Ca2+ signals inhibit adenylyl cyclases 5/6 in vascular smooth muscle cells. Am J Physiol Cell Physiol 2009; 298:C324-32. [PMID: 19889965 DOI: 10.1152/ajpcell.00197.2009] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
cAMP and Ca(2+) are antagonistic intracellular messengers for the regulation of vascular smooth muscle tone; rising levels of Ca(2+) lead to vasoconstriction, whereas an increase of cAMP induces vasodilatation. Here we investigated whether Ca(2+) interferes with cAMP signaling by regulation of phophodiesterases (PDEs) or adenylyl cyclases (ACs). We studied regulation of cAMP concentrations by Ca(2+) signals evoked by endogenous purinergic receptors in vascular smooth muscle cells (VSMCs). The fluorescence resonance energy transfer (FRET)-based cAMP sensor Epac1-camps allowed the measurement of cAMP levels in single-living VSMCs with subsecond temporal resolution. Moreover, in vitro calibration of Epac1-camps enabled us to estimate the absolute cytosolic cAMP concentrations. Stimulation of purinergic receptors decreased cAMP levels in the presence of the beta-adrenergic agonist isoproterenol. Simultaneous imaging of cAMP with Epac1-camps and of Ca(2+) with Fura 2 revealed a rise of intracellular Ca(2+) in response to purinergic stimulation followed by a decline of cAMP. Chelation of intracellular Ca(2+) and overexpression of Ca(2+)-independent AC4 antagonized this decline of cAMP, whereas pharmacological inhibition of Ca(2+)-activated PDE1 had no effect. AC assays with VSMC membranes revealed a significant attenuation of isoproterenol-stimulated cAMP production by the presence of 2 muM Ca(2+). Furthermore, small interfering RNA (siRNA) knockdown of AC5 and AC6 (the two ACs known to be inhibited by Ca(2+)), significantly reduced the decrease of cAMP upon purinergic stimulation of isoproterenol-prestimulated VSMCs. 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.
Collapse
|
97
|
Reiner S, Ziegler N, Leon C, Lorenz K, von Hayn K, Gachet C, Lohse MJ, Hoffmann C. beta-Arrestin-2 interaction and internalization of the human P2Y1 receptor are dependent on C-terminal phosphorylation sites. Mol Pharmacol 2009; 76:1162-71. [PMID: 19741005 DOI: 10.1124/mol.109.060467] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The nucleotide receptor P2Y(1) regulates a variety of physiological processes and is involved in platelet aggregation. Using human P2Y(1)-receptors C-terminally fused with a fluorescent protein, we studied the role of potential receptor phosphorylation sites in receptor internalization and beta-arrestin-2 translocation by means of confocal microscopy. Three receptor constructs were generated that lacked potential phosphorylation sites in the third intracellular loop, the proximal C terminus, or the distal C terminus. The corresponding receptor constructs were expressed in human embryonic kidney (HEK)-293 cells and stimulated with 100 muM ADP. Rapid receptor internalization was observed for the wild-type receptor and from those constructs mutated in the third intracellular loop and the proximal C terminus. However, the construct lacking phosphorylation sites at the distal C terminus did not show receptor internalization upon stimulation. The microscopic data were validated by HA-tagged receptor constructs using a cell surface enzyme-linked immunosorbent assay. P2Y(1)-receptor stimulated beta-arrestin-2-yellow fluorescent protein (YFP) translocation followed the same pattern as receptor internalization. Hence, no beta-arrestin-2-YFP translocation was observed when the distal C-terminal phosphorylation sites were mutated. Individual mutations indicate that residues Ser352 and Thr358 are essential for receptor internalization and beta-arrestin-2-YFP translocation. In contrast, protein kinase C (PKC)-mediated receptor desensitization was not affected by mutation of potential phosphorylation sites in the distal C terminus but was prevented by mutation of potential phosphorylation sites in the proximal C terminus. P2Y(1)-receptor internalization in HEK-293 cells was not blocked by inhibitors of PKC and calmodulin-dependent protein kinase. Thus, we conclude that P2Y(1)-receptor desensitization and internalization are mediated by different phosphorylation sites and kinases.
Collapse
|
98
|
Calebiro D, Nikolaev VO, Gagliani MC, de Filippis T, Dees C, Tacchetti C, Persani L, Lohse MJ. Persistent cAMP-signals triggered by internalized G-protein-coupled receptors. PLoS Biol 2009; 7:e1000172. [PMID: 19688034 PMCID: PMC2718703 DOI: 10.1371/journal.pbio.1000172] [Citation(s) in RCA: 416] [Impact Index Per Article: 27.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2009] [Accepted: 07/07/2009] [Indexed: 01/19/2023] Open
Abstract
Real-time monitoring of G-protein-coupled receptor (GPCR) signaling in native cells suggests that the receptor for thyroid stimulating hormone remains active after internalization, challenging the current model for GPCR signaling. G-protein–coupled receptors (GPCRs) are generally thought to signal to second messengers like cyclic AMP (cAMP) from the cell surface and to become internalized upon repeated or prolonged stimulation. Once internalized, they are supposed to stop signaling to second messengers but may trigger nonclassical signals such as mitogen-activated protein kinase (MAPK) activation. Here, we show that a GPCR continues to stimulate cAMP production in a sustained manner after internalization. We generated transgenic mice with ubiquitous expression of a fluorescent sensor for cAMP and studied cAMP responses to thyroid-stimulating hormone (TSH) in native, 3-D thyroid follicles isolated from these mice. TSH stimulation caused internalization of the TSH receptors into a pre-Golgi compartment in close association with G-protein αs-subunits and adenylyl cyclase III. Receptors internalized together with TSH and produced downstream cellular responses that were distinct from those triggered by cell surface receptors. 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. Cells respond to many environmental cues through the activity of cell surface receptor proteins, which sense these cues and convey that information to signaling molecules inside the cell. G-protein–coupled receptors (GPCRs) form the largest eukaryotic family of plasma membrane receptors. They convert the information provided by extracellular stimuli into intracellular second messengers, like cyclic AMP (cAMP). After prolonged stimulation, they are internalized inside cells, an event that to date has been thought to terminate the production of second messengers. Though many of the key steps of GPCR signaling are known in detail, precisely how signaling and termination actually occur in time and space (i.e., in subcellular compartments or microdomains) is still largely unexplored. To observe GPCR signaling in living cells, we generated mice expressing a fluorescent sensor that allows monitoring the intracellular levels of cAMP with a microscope. We utilized this system to study, directly in native thyroid follicles, the signal sent by the receptor for thyroid-stimulating hormone (TSH). Our findings indicate that TSH receptors are internalized rapidly after activation but continue to stimulate cAMP production inside cells and that this sustained, cAMP production is apparently required for localized activation of downstream components. These data challenge the current model of the GPCR-cAMP pathway by suggesting the existence of previously unrecognized intracellular site(s) for cAMP generation and of differential signaling outcomes as a result of intracellular GPCR signaling. Such intracellular site(s) may provide specialized signaling platforms, thus contributing to the spatiotemporal regulation of cAMP production and to signaling specificity within the GPCR family.
Collapse
|
99
|
Adachi E, Kazoe Y, Sato Y, Suzuki Y, Urano T, Ueyama T, Saito N, Nikolaev VO, Lohse MJ, Tominaga M, Mogami H. A technique for monitoring multiple signals with a combination of prism-based total internal reflection fluorescence microscopy and epifluorescence microscopy. Pflugers Arch 2009; 459:227-34. [PMID: 19680684 DOI: 10.1007/s00424-009-0705-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2009] [Revised: 07/08/2009] [Accepted: 07/21/2009] [Indexed: 10/20/2022]
Abstract
Physiological phenomena are regulated by multiple signal pathways upon receptor stimulation. Here, we have introduced a new technique with a combination of prism-based total internal reflection fluorescence microscopy (PBTIRFM) and epifluorescence microscopy (EPI) to simultaneously monitor multiple signal pathways. This instrumentation allows us to visualize three signal pathways, Ca2+, cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA), and diacylglycerol (DAG)/protein kinase C (PKC) signals in living cells. Three fluorescent indicators were employed for this purpose: (1) Fura-2 AM as a calcium sensor; (2) Epac1-camp, a cyan fluorescent protein-yellow fluorescent protein fluorescence resonance energy transfer-based cAMP indicator, as a cAMP sensor; and (3) C1-tagged monomeric red fluorescent protein, a tandem DAG-binding domain of PKC gamma, as a DAG sensor or myristoylated alanine-rich C kinase substrate-tagged DsRed for the PKC activation pathway. The DAG signal was monitored by PBTIRFM, whereas the Ca2+ and cAMP signals were monitored by EPI. Adenosine trisphosphate resulted in generation of all three second messengers in triple probe-loaded Cos-7 cells. The spectral overlap between these signal probes was evaluated by means of linear unmixing. Forskolin also evoked Ca2+, cAMP/PKA, and DAG/PKC signals whereas acetylcholine activated Ca2+ and DAG/PKC signals as well as inhibiting cAMP generation in triple probe-loaded insulin-secreting cells. Thus, the optical observation system combining PBTIRFM and EPI offers a great advance in analyzing interplay of multiple signaling pathways, such as these second messengers, upon G-protein-coupled receptor stimulation in living cells.
Collapse
|
100
|
Lorenz K, Schmitt JP, Vidal M, Lohse MJ. Cardiac hypertrophy: targeting Raf/MEK/ERK1/2-signaling. Int J Biochem Cell Biol 2009; 41:2351-5. [PMID: 19666137 DOI: 10.1016/j.biocel.2009.08.002] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2009] [Revised: 07/26/2009] [Accepted: 08/04/2009] [Indexed: 10/20/2022]
Abstract
Over the past two decades, basic research has revealed a complex network of regulatory mechanisms that control the ERK1/2-signaling cascade. ERK1/2 mediate cardiac hypertrophy, a major risk factor for the development of arrhythmias, heart failure and sudden death, but also beneficial effects, e.g. protection of the heart from cell death and ischemic injury. Selective targeting of these ambiguous ERK functions could provide a powerful tool in the treatment of cardiac disease. 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.
Collapse
|