Stefan Offermanns

Publications of Stefan Offermanns

• ErbB-2 signals through Plexin-B1 to promote breast cancer metastasis.

  Authors: Thomas Worzfeld, Jakub M Swiercz, Mario Looso, Beate K Straub, Kishor K Sivaraj, Stefan Offermanns

  The Journal of clinical investigation. 03/2012; 122(4):1296-305.

  Diagnosis of metastatic breast cancer is associated with a very poor prognosis. New therapeutic targets are urgently needed, but their development is hampered by a lack of understanding of theDiagnosis of metastatic breast cancer is associated with a very poor prognosis. New therapeutic targets are urgently needed, but their development is hampered by a lack of understanding of the mechanisms leading to tumor metastasis. Exemplifying this is the fact that the approximately 30% of all breast cancers overexpressing the receptor tyrosine kinase ErbB-2 are characterized by high metastatic potential and poor prognosis, but the signaling events downstream of ErbB-2 that drive cancer cell invasion and metastasis remain incompletely understood. Here we show that overexpression of ErbB-2 in human breast cancer cell lines leads to phosphorylation and activation of the semaphorin receptor Plexin-B1. This was required for ErbB-2-dependent activation of the pro-metastatic small GTPases RhoA and RhoC and promoted invasive behavior of human breast cancer cells. In a mouse model of ErbB-2-overexpressing breast cancer, ablation of the gene encoding Plexin-B1 strongly reduced the occurrence of metastases. Moreover, in human patients with ErbB-2-overexpressing breast cancer, low levels of Plexin-B1 expression correlated with good prognosis. Our data suggest that Plexin-B1 represents a new candidate therapeutic target for treating patients with ErbB-2-positive breast cancer.

• Gα(q/11) signaling tonically modulates nociceptor function and contributes to activity-dependent sensitization.

  Authors: Anke Tappe-Theodor, Cristina E Constantin, Irmgard Tegeder, Stefan G Lechner, Michiel Langeslag, Peter Lepcynzsky, Richard I Wirotanseng, Martina Kurejova, Nitin Agarwal, Gergely Nagy, Andrew Todd, Nina Wettschureck, Stefan Offermanns, Michaela Kress, Gary R Lewin, Rohini Kuner

  Pain. 11/2011; 153(1):184-96.

  Peripheral injury or inflammation leads to a release of mediators capable of binding to a variety of ion channels and receptors. Among these are the 7-transmembrane receptors (G protein-coupledPeripheral injury or inflammation leads to a release of mediators capable of binding to a variety of ion channels and receptors. Among these are the 7-transmembrane receptors (G protein-coupled receptors) coupling to G(s), G(i/o), G₁₂/₁₃, or G(q/11) G proteins. Each of the G protein-coupled receptor pathways is involved in nociceptive modulation and pain processing, but the relative contribution of individual signaling pathways in vivo has not yet been worked out. The G(q)/G₁₁ signaling branch is of particular interest because it leads to the activation of phospholipase C-β, protein kinase C, the release of calcium from intracellular stores, and it modulates extracellular regulated kinases. To investigate the contribution of the entire G(q/11)-signaling pathway in nociceptors towards regulation of pain, we generated double-deficient mice lacking G(q/11) selectively in nociceptors using a conditional gene-targeting approach. We observed that nociceptor-specific loss of G(q) and G₁₁ results in reduced pain hypersensitivity following paw inflammation or spared nerve injury. Surprisingly, our behavioral and electrophysiological experiments also indicated defects in basal mechanical sensitivity in G(q/11) mutant mice, suggesting a novel function for G(q/11) in tonic modulation of acute nociception. Patch-clamp recordings revealed changes in voltage-dependent tetrodotoxin-resistant and tetrodotoxin-sensitive sodium channels in nociceptors upon a loss of G(q/11), whereas potassium currents remained unchanged. Our results indicate that the functional role of the G(q)/G₁₁ branch of G-protein signaling in nociceptors in vivo not only spans sensitization mechanisms in pathological pain states, but is also operational in tonic modulation of basal nociception and acute pain.

• Megakaryocyte-specific RhoA deficiency causes macrothrombocytopenia and defective platelet activation in hemostasis and thrombosis.

  Authors: Irina Pleines, Ina Hagedorn, Shuchi Gupta, Frauke May, Lidija Chakarova, Jolanda van Hengel, Stefan Offermanns, Georg Krohne, Christoph Kleinschnitz, Cord Brakebusch, Bernhard Nieswandt

  Blood. 11/2011; 119(4):1054-63.

  Vascular injury initiates rapid platelet activation that is critical for hemostasis, but it also may cause thrombotic diseases, such as myocardial infarction or ischemic stroke. Reorganizations ofVascular injury initiates rapid platelet activation that is critical for hemostasis, but it also may cause thrombotic diseases, such as myocardial infarction or ischemic stroke. Reorganizations of the platelet cytoskeleton are crucial for platelet shape change and secretion and are thought to involve activation of the small GTPase RhoA. In this study, we analyzed the in vitro and in vivo consequences of megakaryocyte- and platelet-specific RhoA gene deletion in mice. We found a pronounced macrothrombocytopenia in RhoA-deficient mice, with platelet counts of approximately half that of wild-type controls. The mutant cells displayed an altered shape but only a moderately reduced life span. Shape change of RhoA-deficient platelets in response to G(13)-coupled agonists was abolished, and it was impaired in response to G(q) stimulation. Similarly, RhoA was required for efficient secretion of α and dense granules downstream of G(13) and G(q). Furthermore, RhoA was essential for integrin-mediated clot retraction but not for actomyosin rearrangements and spreading of activated platelets on fibrinogen. In vivo, RhoA deficiency resulted in markedly prolonged tail bleeding times but also significant protection in different models of arterial thrombosis and in a model of ischemic stroke. Together, these results establish RhoA as an important regulator of platelet function in thrombosis and hemostasis.

• Nicotinic acid (niacin): new lipid-independent mechanisms of action and therapeutic potentials.

  Authors: Martina Lukasova, Julien Hanson, Sorin Tunaru, Stefan Offermanns

  Trends in pharmacological sciences. 09/2011; 32(12):700-7.

  Nicotinic acid (niacin) has been used for decades to prevent and treat atherosclerosis. The well-documented antiatherogenic activity is believed to result from its antidyslipidemic effects, which areNicotinic acid (niacin) has been used for decades to prevent and treat atherosclerosis. The well-documented antiatherogenic activity is believed to result from its antidyslipidemic effects, which are accompanied by unwanted effects, especially a flush. There has been renewed interest in nicotinic acid owing to the need for improved prevention of atherosclerosis in patients already taking statins. In addition, the identification of a nicotinic acid receptor expressed in adipocytes and immune cells has helped to elucidate the mechanisms underlying the antiatherosclerotic as well as the unwanted effects of this drug. Nicotinic acid exerts its antiatherosclerotic effects at least in part independently of its antidyslipidemic effects through mechanisms involving its receptor on immune cells as well as through direct and indirect effects on the vascular endothelium. Here, we review recent data on the pharmacological effects of nicotinic acid and discuss how they might be harnessed to treat other inflammatory diseases such as multiple sclerosis or psoriasis.

• Nicotinic acid inhibits progression of atherosclerosis in mice through its receptor GPR109A expressed by immune cells.

  Authors: Martina Lukasova, Camille Malaval, Andreas Gille, Jukka Kero, Stefan Offermanns

  The Journal of clinical investigation. 03/2011; 121(3):1163-73.

  Nicotinic acid (niacin) is a drug used to reduce the progression of atherosclerosis. Its antiatherosclerotic activity is believed to result from lipid-modifying effects, including its ability toNicotinic acid (niacin) is a drug used to reduce the progression of atherosclerosis. Its antiatherosclerotic activity is believed to result from lipid-modifying effects, including its ability to decrease LDL cholesterol and increase HDL cholesterol levels in plasma. Here, we report that in a mouse model of atherosclerosis, we found that nicotinic acid inhibited disease progression under conditions that left total cholesterol and HDL cholesterol plasma levels unaffected. The antiatherosclerotic effect was not seen in mice lacking the receptor for nicotinic acid GPR109A. Surprisingly, transplantation of bone marrow from GPR109A-deficient mice into atherosclerosis-prone animals also abrogated the beneficial effect of nicotinic acid. We detected expression of GPR109A in macrophages in atherosclerotic plaques. In macrophages from WT mice, but not from GPR109A-deficient animals, nicotinic acid induced expression of the cholesterol transporter ABCG1 and promoted cholesterol efflux. Furthermore, activation of GPR109A by nicotinic acid inhibited MCP-1-induced recruitment of macrophages into the peritoneal cavity and impaired macrophage recruitment to atherosclerotic plaques. In contrast with current models, our data show that nicotinic acid can reduce the progression of atherosclerosis independently of its lipid-modifying effects through the activation of GPR109A on immune cells. We conclude therefore that GPR109A mediates antiinflammatory effects, which may be useful for treating atherosclerosis and other diseases.

• G alpha(q) signal in osteoblasts is inhibitory to the osteoanabolic action of parathyroid hormone.

  Authors: Naoshi Ogata, Yusuke Shinoda, Nina Wettschureck, Stefan Offermanns, Shu Takeda, Kozo Nakamura, Gino V Segre, Ung-il Chung, Hiroshi Kawaguchi

  The Journal of biological chemistry. 02/2011; 286(15):13733-40.

  This study examined the role of the Gα(q) signal constituted by Gα(q) and Gα(11) (encoded by Gnα(q) and Gnα(11), respectively), a major intracellular pathway of parathyroid hormone (PTH), in the PTHThis study examined the role of the Gα(q) signal constituted by Gα(q) and Gα(11) (encoded by Gnα(q) and Gnα(11), respectively), a major intracellular pathway of parathyroid hormone (PTH), in the PTH osteoanabolic action by the gain- and loss-of-function analyses. Transgenic mice with osteoblast-specific overexpression of the constitutively active Gnα(q) gene under the control of 2.3-kb type I collagen α1 chain (Col1a1) promoter exhibited osteopenia with decreased bone formation parameters and did not respond to the daily PTH treatment. We then established osteoblast-specific Gnα(q) and Gnα(11) double-knock-out (cDKO) mice by crossing the 2.3-kb Col1a1 promoter-Cre recombinase transgenic mice and those with Gnα(q) gene flanked with loxP and global ablation of Gnα(11) (Col1a1-Cre(+/-);Gna(q)(fl/fl);Gna(11)(-/-)) and found that the cDKO and single knock-out littermates of Gnα(q) or Gnα(11) exhibited normal bone volume and turnover under physiological conditions. With a daily injection of PTH, however, the cDKO mice, but not the single knock-out mice, showed higher bone volume and turnover than the wild-type littermates. Cultures of primary osteoblasts derived from cDKO and wild-type littermates confirmed enhancement of the PTH osteoanabolic action by the Gα(q) signal deficiency in a cell-autonomous mechanism, in association with the membrane translocation of protein kinase Cδ. This enhancement was reproduced by overexpression of regulator of G protein signaling-2, a Gα(q) signal inhibitor, in osteoblastic MC3T3-E1 cells. Hence, the Gα(q) signal plays an inhibitory role in the PTH osteoanabolic action, suggesting that its suppression may lead to a novel treatment in combination with PTH against osteoporosis.

• Biological and pharmacological roles of HCA receptors.

  Authors: Clara C Blad, Kashan Ahmed, Ad P IJzerman, Stefan Offermanns

  Advances in pharmacology (San Diego, Calif.). 01/2011; 62:219-50.

  The hydroxy-carboxylic acid (HCA) receptors HCA(1), HCA(2), and HCA(3) were previously known as GPR81, GPR109A, and GPR109B, respectively, or as the nicotinic acid receptor family. They form aThe hydroxy-carboxylic acid (HCA) receptors HCA(1), HCA(2), and HCA(3) were previously known as GPR81, GPR109A, and GPR109B, respectively, or as the nicotinic acid receptor family. They form a cluster of G protein-coupled receptors with high sequence homology. Recently, intermediates of energy metabolism, all HCAs, have been reported as endogenous ligands for each of these receptors. The HCA receptors are predominantly expressed on adipocytes and mediate the inhibition of lipolysis by coupling to G(i)-type proteins. HCA(1) is activated by lactate, HCA(2) by the ketone body 3-hydroxy-butyrate, and HCA(3) by hydroxylated β-oxidation intermediates, especially 3-hydroxy-octanoic acid. Both HCA(2) and HCA(3) are part of a negative feedback loop which keeps the release of fat stores in check under starvation conditions, whereas HCA(1) plays a role in the antilipolytic (fat-conserving) effect of insulin. HCA(2) was first discovered as the molecular target of the antidyslipidemic drug nicotinic acid (or niacin). Many synthetic agonists have since been designed for HCA(2) and HCA(3), but the development of a new, improved HCA-targeted drug has not been successful so far, despite a number of clinical studies. Recently, it has been shown that the major side effect of nicotinic acid, skin flushing, is mediated by HCA(2) receptors on keratinocytes, as well as on Langerhans cells in the skin. In this chapter, we summarize the latest developments in the field of HCA receptor research, with emphasis on (patho)physiology, receptor pharmacology, major ligand classes, and the therapeutic potential of HCA ligands.

• Tamoxifen-inducible Cre-mediated recombination in adipocytes.

  Authors: Antonia Sassmann, Stefan Offermanns, Nina Wettschureck

  Genesis (New York, N.Y. : 2000). 10/2010; 48(10):618-25.

  To generate a mouse line which allows inducible, Cre/loxP-dependent recombination in adipocytes, we used RedE/RedT-mediated recombineering to insert the CreER(T)²-transgene, which encodes a fusionTo generate a mouse line which allows inducible, Cre/loxP-dependent recombination in adipocytes, we used RedE/RedT-mediated recombineering to insert the CreER(T)²-transgene, which encodes a fusion protein of Cre and a mutated tamoxifen-responsive estrogen receptor, into the start codon of the adipocyte-specific Adipoq gene. Adipoq encodes adiponectin, an adipokine specifically expressed in differentiated adipocytes. Tamoxifen treatment induced almost complete recombination in white adipose tissue of the AdipoqCreER(T)² mouse line (97%-99%), while no recombination was seen in vehicle-treated animals. Recombination in brown adipose tissue was about 15%, whereas other organs and tissues did not undergo recombination. In addition, mice expressing CreER(T)² in adipocytes did not show any alterations of metabolic functions like glucose tolerance, lipolysis, or energy expenditure compared to control mice. Therefore the AdipoqCreER(T)² mouse line will be a valuable tool for studying the consequences of a temporally controlled deletion of floxed genes in white adipose tissue.

• A systematic expression analysis implicates Plexin-B2 and its ligand Sema4C in the regulation of the vascular and endocrine system.

  Authors: Matthias Zielonka, Jingjing Xia, Roland H Friedel, Stefan Offermanns, Thomas Worzfeld

  Experimental cell research. 09/2010; 316(15):2477-86.

  Plexins serve as receptors for semaphorins and play important roles in the developing nervous system. Plexin-B2 controls decisive developmental programs in the neural tube and cerebellum. However,Plexins serve as receptors for semaphorins and play important roles in the developing nervous system. Plexin-B2 controls decisive developmental programs in the neural tube and cerebellum. However, whether Plexin-B2 also regulates biological functions in adult nonneuronal tissues is unknown. Here we show by two methodologically independent approaches that Plexin-B2 is expressed in discrete cell types of several nonneuronal tissues in the adult mouse. In the vasculature, Plexin-B2 is selectively expressed in functionally specialized endothelial cells. In endocrine organs, Plexin-B2 localizes to the pancreatic islets of Langerhans and to both cortex and medulla of the adrenal gland. Plexin-B2 expression is also detected in certain types of immune and epithelial cells. In addition, we report on a systematic comparison of the expression patterns of Plexin-B2 and its ligand Sema4C, which show complementarity or overlap in some but not all tissues. Furthermore, we demonstrate that Plexin-B2 and its family member Plexin-B1 display largely nonredundant expression patterns. This work establishes Plexin-B2 and Sema4C as potential regulators of the vascular and endocrine system and provides an anatomical basis to understand the biological functions of this ligand-receptor pair.

• Nicotinic acid- and monomethyl fumarate-induced flushing involves GPR109A expressed by keratinocytes and COX-2-dependent prostanoid formation in mice.

  Authors: Julien Hanson, Andreas Gille, Sabrina Zwykiel, Martina Lukasova, Björn E Clausen, Kashan Ahmed, Sorin Tunaru, Angela Wirth, Stefan Offermanns

  The Journal of clinical investigation. 08/2010; 120(8):2910-9.

  The antidyslipidemic drug nicotinic acid and the antipsoriatic drug monomethyl fumarate induce cutaneous flushing through activation of G protein-coupled receptor 109A (GPR109A). Flushing is aThe antidyslipidemic drug nicotinic acid and the antipsoriatic drug monomethyl fumarate induce cutaneous flushing through activation of G protein-coupled receptor 109A (GPR109A). Flushing is a troublesome side effect of nicotinic acid, but may be a direct reflection of the wanted effects of monomethyl fumarate. Here we analyzed the mechanisms underlying GPR109A-mediated flushing and show that both Langerhans cells and keratinocytes express GPR109A in mice. Using cell ablation approaches and transgenic cell type-specific GPR109A expression in Gpr109a-/- mice, we have provided evidence that the early phase of flushing depends on GPR109A expressed on Langerhans cells, whereas the late phase is mediated by GPR109A expressed on keratinocytes. Interestingly, the first phase of flushing was blocked by a selective cyclooxygenase-1 (COX-1) inhibitor, and the late phase was sensitive to a selective COX-2 inhibitor. Both monomethyl fumarate and nicotinic acid induced PGE2 formation in isolated keratinocytes through activation of GPR109A and COX-2. Thus, the early and late phases of the GPR109A-mediated cutaneous flushing reaction involve different epidermal cell types and prostanoid-forming enzymes. These data will help to guide new efficient approaches to mitigate nicotinic acid-induced flushing and may help to exploit the potential antipsoriatic effects of GPR109A agonists in the skin.

• The Gq/G11-mediated signaling pathway is critical for autocrine potentiation of insulin secretion in mice.

  Authors: Antonia Sassmann, Belinda Gier, Hermann-Josef Gröne, Gisela Drews, Stefan Offermanns, Nina Wettschureck

  The Journal of clinical investigation. 06/2010; 120(6):2184-93.

  A variety of neurotransmitters, gastrointestinal hormones, and metabolic signals are known to potentiate insulin secretion through GPCRs. We show here that beta cell-specific inactivation of theA variety of neurotransmitters, gastrointestinal hormones, and metabolic signals are known to potentiate insulin secretion through GPCRs. We show here that beta cell-specific inactivation of the genes encoding the G protein alpha-subunits Galphaq and Galpha11 resulted in impaired glucose tolerance and insulin secretion in mice. Interestingly, the defects observed in Galphaq/Galpha11-deficient beta cells were not restricted to loss of muscarinic or metabolic potentiation of insulin release; the response to glucose per se was also diminished. Electrophysiological recordings revealed that glucose-induced depolarization of isolated beta cells was impaired in the absence of Galphaq/Galpha11, and closure of KATP channels was inhibited. We provide evidence that this reduced excitability was due to a loss of beta cell-autonomous potentiation of insulin secretion through factors cosecreted with insulin. We identified as autocrine mediators involved in this process extracellular nucleotides such as uridine diphosphate acting through the Gq/G11-coupled P2Y6 receptor and extracellular calcium acting through the calcium-sensing receptor. Thus, the Gq/G11-mediated signaling pathway potentiates insulin secretion in response to glucose by integrating systemic as well as autocrine/paracrine mediators.

• Diabetes-related defects in sarcoplasmic Ca2+ release are prevented by inactivation of G(alpha)11 and G(alpha)q in murine cardiomyocytes.

  Authors: Dieter Paul Hoyer, Sabine Grönke, Konrad F Frank, Klaus Addicks, Nina Wettschureck, Stefan Offermanns, Erland Erdmann, Hannes Reuter

  Molecular and cellular biochemistry. 04/2010; 341(1-2):235-44.

  Neurohumoral stimulation of Gq-coupled receptors has been proposed as a central mechanism in the pathogenesis of diabetic heart disease. The resulting contractile dysfunction is closely related toNeurohumoral stimulation of Gq-coupled receptors has been proposed as a central mechanism in the pathogenesis of diabetic heart disease. The resulting contractile dysfunction is closely related to abnormal intracellular Ca(2+) handling with functional defects of the sarcoplasmic reticulum (SR). The present study was therefore designed to determine the role of G(q)-protein signaling via G(alpha)(11) and G(alpha)(q) in diabetes for the induction of functional and structural changes in the Ca(2+) release complex of the SR. An experimental type 1-diabetes was induced in wild type, G(alpha)(11) knockout, and G(alpha)(11/q)-knockout mice by injection of streptozotocin. Cardiac morphology and function was assessed in vivo by echocardiography. SR Ca(2+) leak was tested in vitro based on a (45)Ca(2+) assay and protein densities as well as gene expression of ryanodine receptor (RyR2), FKBP12.6, sorcin, and annexin A7 were analyzed by immunoblot and RT-PCR. In wild type animals 8 weeks of diabetes resulted in cardiac hypertrophy and SR Ca(2+) leak was increased. In addition, diabetic wild type animals showed reduced protein levels of FKBP12.6 and annexin A7. In G(alpha)(11)- and G(alpha)(11/q)-knockout animals, however, SR Ca(2+) release and cardiac phenotype remained unchanged upon induction of diabetes. Densities of the proteins that we presently analyzed were also unaltered in G(alpha)(11)-knockout mice. G(alpha)(11/q)-knockout animals even showed increased expression of sorcin and annexin A7. Thus, based on the present study we suggest a signaling pathway via the G(q)-proteins, G(alpha)(11) and G(alpha)(q), that could link increased neurohumoral stimulation in diabetes with defective RyR2 channel function by regulating protein expression of FKBP12.6, annexin A7, and sorcin.

• An autocrine lactate loop mediates insulin-dependent inhibition of lipolysis through GPR81.

  Authors: Kashan Ahmed, Sorin Tunaru, Cong Tang, Michaela Müller, Andreas Gille, Antonia Sassmann, Julien Hanson, Stefan Offermanns

  Cell metabolism. 04/2010; 11(4):311-9.

  Lactate is an important metabolic intermediate released by skeletal muscle and other organs including the adipose tissue, which converts glucose into lactate under the influence of insulin. Here weLactate is an important metabolic intermediate released by skeletal muscle and other organs including the adipose tissue, which converts glucose into lactate under the influence of insulin. Here we show that lactate activates the G protein-coupled receptor GPR81, which is expressed in adipocytes and mediates antilipolytic effects through G(i)-dependent inhibition of adenylyl cyclase. Using GPR81-deficient mice, we demonstrate that the receptor is not involved in the regulation of lipolysis during intensive exercise. However, insulin-induced inhibition of lipolysis and insulin-induced decrease in adipocyte cAMP levels were strongly reduced in mice lacking GPR81, although insulin-dependent release of lactate by adipocytes was comparable between wild-type and GPR81-deficient mice. Thus, lactate and its receptor GPR81 unexpectedly function in an autocrine and paracrine loop to mediate insulin-induced antilipolytic effects. These data show that lactate can directly modulate metabolic processes in a hormone-like manner, and they reveal a new mechanism underlying the antilipolytic effects of insulin.

• Differential expression of protein kinase C isoforms in coronary arteries of diabetic mice lacking the G-protein Gα11.

  Authors: Dieter Paul Hoyer, Yüksel Korkmaz, Sabine Grönke, Klaus Addicks, Nina Wettschureck, Stefan Offermanns, Hannes Reuter

  Cardiovascular diabetology. 01/2010; 9:93.

  Diabetes mellitus counts as a major risk factor for developing atherosclerosis. The activation of protein kinase C (PKC) is commonly known to take a pivotal part in the pathogenesis ofDiabetes mellitus counts as a major risk factor for developing atherosclerosis. The activation of protein kinase C (PKC) is commonly known to take a pivotal part in the pathogenesis of atherosclerosis, though the influence of specific PKC isozymes remains unclear. There is evidence from large clinical trials suggesting excessive neurohumoral stimulation, amongst other pathways leading to PKC activation, as a central mechanism in the pathogenesis of diabetic heart disease. The present study was therefore designed to determine the role of Gq-protein signalling via Gα11 in diabetes for the expression of PKC isozymes in the coronary vessels. The role of Gα11 in diabetes was examined in knockout mice with global deletion of Gα11 compared to wildtype controls. An experimental type 1-diabetes was induced in both groups by injection of streptozotocin. Expression and localization of the PKC isozymes α, βII, δ, ε, and ζ was examined by quantitative immunohistochemistry. 8 weeks after induction of diabetes a diminished expression of PKC ε was observed in wildtype animals. This alteration was not seen in Gα11 knockout animals, however, these mice showed a diminished expression of PKCζ. Direct comparison of wildtype and knockout control animals revealed a diminished expression of PKC δ and ε in Gα11 knockout animals. The present study shows that expression of the nPKCs δ and ε in coronary vessels is under control of the g-protein Gα11. The reduced expression of PKC ζ that we observed in coronary arteries from Gα11-knockout mice compared to wildtype controls upon induction of diabetes could reduce apoptosis and promote plaque stability. These findings suggest a mechanism that may in part underlie the therapeutic benefit of RAS inhibition on cardiovascular endpoints in diabetic patients.

• Activity Modes in Thalamocortical Relay Neurons are Modulated by G(q)/G(11) Family G-proteins - Serotonergic and Glutamatergic Signaling.

  Authors: Philippe Coulon, Tatyana Kanyshkova, Tilman Broicher, Thomas Munsch, Nina Wettschureck, Thomas Seidenbecher, Sven G Meuth, Stefan Offermanns, Hans-Christian Pape, Thomas Budde

  Frontiers in cellular neuroscience. 01/2010; 4:132.

  In thalamocortical relay (TC) neurons, G-protein-coupled receptors play an important part in the control of activity modes. A conditional Gα(q) knockout on the background of a constitutive Gα(11)In thalamocortical relay (TC) neurons, G-protein-coupled receptors play an important part in the control of activity modes. A conditional Gα(q) knockout on the background of a constitutive Gα(11) knockout (Gα(q)/Gα(11) (-/-)) was used to determine the contribution of Gq/G11 family G-proteins to metabotropic serotonin (5-HT) and glutamate (Glu) function in the dorsal part of the lateral geniculate nucleus (dLGN). In control mice, current clamp recordings showed that α-m-5-HT induced a depolarization of V(rest) which was sufficient to suppress burst firing. This depolarization was concentration-dependent (100 μM: +6 ± 1 mV, n = 10; 200 μM: +10 ± 1 mV, n = 7) and had a conditioning effect on the activation of other Gα(q)-mediated pathways. The depolarization was significantly reduced in Gα(q)/Gα(11) (-/-) (100 μM: 3 ± 1 mV, n = 11; 200 μM: 5 ± 1 mV, n = 6) and was apparently insufficient to suppress burst firing. Activating Gα(q)-coupled muscarinic receptors affected the magnitude of α-m-5-HT-induced effects in a reciprocal manner. Furthermore, the depolarizing effect of mGluR1 agonists was significantly reduced in Gα(q)/Gα(11) (-/-) mice. Immunohistochemical stainings revealed binding of 5-HT(2C)R- and mGluR1α-, but not of 5-HT(2A)R-specific antibodies in the dLGN of Gα(q)/Gα(11) (-/-) mice. In conclusion, these findings demonstrate that transmitters of ascending brainstem fibers and corticofugal fibers both signal via a central element in the form of Gq/G11-mediated pathways to control activity modes in the TC system.

• GPR109A, GPR109B and GPR81, a family of hydroxy-carboxylic acid receptors.

  Authors: Kashan Ahmed, Sorin Tunaru, Stefan Offermanns

  Trends in pharmacological sciences. 11/2009; 30(11):557-62.

  G-protein-coupled receptors (GPCRs) are the most versatile receptor family as they have the ability to respond to chemically diverse ligands. Despite intensive efforts during the past two decades,G-protein-coupled receptors (GPCRs) are the most versatile receptor family as they have the ability to respond to chemically diverse ligands. Despite intensive efforts during the past two decades, there are still more than 100 orphan GPCRs for which endogenous ligands are unknown. Recently, GPR109A, GPR109B and GPR81, which form a GPCR subfamily, have been deorphanized. The physiological ligands of these receptors are the ketone body 3-hydroxy-butyrate, the metabolite 2-hydroxy-propanoate (lactate) as well as the beta-oxidation intermediate 3-hydroxy-octanoate. Thus, this receptor subfamily is activated by hydroxy-carboxylic acid ligands which are intermediates of energy metabolism. All three receptors are predominantly expressed in adipocytes and mediate antilipolytic effects. In this article, we propose that the hydroxy-carboxylic acid structure of their endogenous ligands is the defining property of this receptor subfamily and that hydroxy-carboxylic acid receptors function as metabolic sensors which fine-tune the regulation of metabolic pathways.

• The semaphorin 4D-plexin-B signalLing complex regulates dendritic and axonal complexity in developing neurons via diverse pathways.

  Authors: Peter Vodrazka, Alexander Korostylev, Alexandra Hirschberg, Jakub M Swiercz, Thomas Worzfeld, Suhua Deng, Pietro Fazzari, Luca Tamagnone, Stefan Offermanns, Rohini Kuner

  The European journal of neuroscience. 10/2009; 30(7):1193-208.

  Semaphorins and their receptors, plexins, have emerged as key regulators of various aspects of neuronal development. In contrast to the Plexin-A family, the cellular functions of Plexin-B familySemaphorins and their receptors, plexins, have emerged as key regulators of various aspects of neuronal development. In contrast to the Plexin-A family, the cellular functions of Plexin-B family proteins in developing neurons are only poorly understood. An activation of Plexin-B1 via its ligand, semaphorin 4D (Sema4D), produces an acute collapse of axonal growth cones in hippocampal and retinal neurons over the early stages of neurite outgrowth. However, the functional role of Sema4D-Plexin-B interactions over subsequent stages of neurite development, differentiation and maturation has not been characterized. Here we addressed this question using morphogenetic assays and time-lapse imaging on developing rat hippocampal neurons as a model system. Interestingly, Sema4D treatment over several hours was observed to promote branching and complexity in hippocampal neurons via the activation of Plexin-B1. The activation of receptor tyrosine kinases and the Rho kinase following Sema4D treatment was found to control dendritic and axonal morphogenesis by differentially regulating branching and extension. Phosphoinositide-3-kinase, but not extracellular signal-regulated kinase 1/2, was observed to be important for the stimulatory effects of Sema4D on dendritic branching. Furthermore, we observed that the mammalian target of rapamycin is activated downstream of Plexin-B1 and contributes to Sema4D-induced effects on dendritic branching. In contrast, glycogen synthase kinase-3 beta, another effector of phosphoinositide-3-kinase signalling, was not involved. Thus, our results show that Sema4D-Plexin-B interactions modulate dendritic and axonal arborizations of developing neurons by co-ordinated and concerted activation of diverse signalling pathways.

• Mice lacking Plexin-B3 display normal CNS morphology and behaviour.

  Authors: Thomas Worzfeld, Philipp Rauch, Khalad Karram, Jacqueline Trotter, Rohini Kuner, Stefan Offermanns

  Molecular and cellular neurosciences. 09/2009;

  Semaphorins and their receptors, plexins, have emerged as important regulators of a multitude of biological processes. Plexin-B3 has been shown to be selectively expressed in postnatalSemaphorins and their receptors, plexins, have emerged as important regulators of a multitude of biological processes. Plexin-B3 has been shown to be selectively expressed in postnatal oligodendrocytes. In contrast to the well-characterized Plexin-A family and the Plexin-B family members Plexin-B1 and -B2, no data are available on the functional role of Plexin-B3 in the central nervous system in vivo. Here we have elucidated the functional significance of Plexin-B3 by generating and analyzing constitutive knock-out mice. Plexin-B3-deficient mice were found to be viable and fertile. A systematic histological analysis revealed no morphological defects in the brain or spinal cord of mutant animals. In detailed behavioural analyses of locomotor activity, motor coordination, motor learning and anxiety levels Plexin-B3-deficient mice were indistinguishable from wild-type controls. Thus we conclude that under physiological conditions Plexin-B3 is not essential for the development and function of the central nervous system.

• Deorphanisation of GPR109B as a receptor for the beta-Oxidation intermediate 3-OH-octanoic acid and its role in the regulation of lipolysis.

  Authors: Kashan Ahmed, Sorin Tunaru, Claus-Dieter Langhans, Julien Hanson, Christoph W. Michalski, Stefan Koelker, Patricia M. Jones, Juergen G Okun, Stefan Offermanns

  The Journal of biological chemistry. 07/2009;

  The orphan G-protein coupled receptor GPR109B is the result of a recent gene duplication of the nicotinic acid and ketone body receptor GPR109A being found in humans but not in rodents. Like GPR109A,The orphan G-protein coupled receptor GPR109B is the result of a recent gene duplication of the nicotinic acid and ketone body receptor GPR109A being found in humans but not in rodents. Like GPR109A, GPR109B is predominantly expressed in adipocytes and is supposed to mediate antilipolytic effects. Here we show that GPR109B serves as a receptor for the the b-oxidation intermediate 3-OH-octanoic acid which has antilipolytic activity on human but not on murine adipocytes. GPR109B is coupled to Gi-type G-proteins and is activated by 2- and 3-OH-octanoic acid and with EC50 values of about 4 and 8 microM, respectively. Interestingly, 3-OH-octanoic acid plasma concentrations reach micromolar concentrations under conditions of increased b-oxidation rates like in diabetic ketoacidosis or under a ketogenic diet. These data suggest that the ligand receptor pair 3-OH-octanoic acid / GPR109B mediates in humans a negative feedback regulation of adipocyte lipolysis in order to counteract prolipolytic influences under conditions of physiological or pathological increases in b-oxidation rates.

• Guanine Nucleotide-Binding Proteins of the G(12) Family Shape Immune Functions by Controlling CD4(+) T Cell Adhesiveness and Motility.

  Authors: Susanne Herroeder, Peter Reichardt, Antonia Sassmann, Barbara Zimmermann, Dagmar Jaeneke, Jana Hoeckner, Markus W Hollmann, Klaus-Dieter Fischer, Stephan Vogt, Robert Grosse, Nancy Hogg, Matthias Gunzer, Stefan Offermanns, Nina Wettschureck

  Immunity. 05/2009;

  Integrin-mediated adhesion plays a central role in T cell trafficking and activation. Genetic inactivation of the guanine nucleotide-binding (G) protein alpha-subunits Galpha(12) and Galpha(13)Integrin-mediated adhesion plays a central role in T cell trafficking and activation. Genetic inactivation of the guanine nucleotide-binding (G) protein alpha-subunits Galpha(12) and Galpha(13) resulted in an increased activity of integrin leukocyte-function-antigen-1 in murine CD4(+) T cells. The interaction with allogeneic dendritic cells was enhanced, leading to an abnormal proliferative response in vitro. In vivo, T cell-specific inactivation of Galpha(12) and Galpha(13) caused lymphadenopathy due to increased lymph node entry and enhanced T cell proliferation, and the susceptibility toward T cell-mediated diseases was enhanced. Mechanistically, we show that in the absence of Galpha(12) and Galpha(13) the activity of the small GTPases Rac1 and Rap1 was increased, whereas signaling of the small GTPase RhoA was strongly reduced. Our data indicate that locally produced mediators signal through Galpha(12)- and Galpha(13)-coupled receptors to negatively regulate cell polarization and adhesiveness, thereby fine-tuning T cell trafficking, proliferation, and susceptibility toward T cell-mediated diseases.