scholarly journals Kiss1/Gpr54 Prevents Bone Loss through Src Dephosphorylation by Dusp18 in Osteoclasts

2021 ◽  
Author(s):  
Zhenxi Li ◽  
Xinghai Yang ◽  
Jian Jiao ◽  
Zhipeng Wu ◽  
Zhixiang Wu ◽  
...  
Keyword(s):  
Bone Loss ◽  
Therapeutic Strategy ◽  
Natural Ligand ◽  
C Terminus ◽  
Functional Defect ◽  
Approved Drugs ◽  
G Protein Coupled ◽  
Deficient Mice ◽  
Arginine Rich Motif

Abstract Osteoclasts were over-activated as we age, which leads to bone loss. Src-deficient mice lead to only one phenotype -severe osteopetrosis due to functional defect in osteoclasts, indicating that Src function is essential in osteoclasts. G-protein-coupled receptors (GPCR) have been targets for ∼35% of approved drugs. However, how Src kinase activity is negatively regulated by GPCRs remains largely elusive. Herein we report that Src is dephosphorylated at Tyr 416 by Dusp18 upon GPR54 activation by its natural ligand Kp-10. Mechanically, both active Src and the Dusp18 phosphatase are recruited by GPR54 through the proline/arginine-rich motif (PR motif) in the C terminus, which is dependent on the Gαq signal pathway. As such, Kiss1, Gpr54, Dusp18 knockout mice all exhibit osteoclast hyperactivation and bone loss. Accordingly, Kp-10 abrogated bone loss by suppressing osteoclasts activity in vivo. Therefore, Kiss1/Gpr54 is a promising therapeutic strategy governing bone resorption through Src dephosphorylation by Dusp18.

scholarly journals 12(S)-hydroxyheptadeca-5Z, 8E, 10E–trienoic acid is a natural ligand for leukotriene B4 receptor 2

2008 ◽  
Vol 205 (4) ◽  
pp. 759-766 ◽  
Author(s):  
Toshiaki Okuno ◽  
Yoshiko Iizuka ◽  
Hiroshi Okazaki ◽  
Takehiko Yokomizo ◽  
Ryo Taguchi ◽  
...  
Keyword(s):  
Mast Cells ◽  
Intracellular Signaling ◽  
Mammalian Cells ◽  
High Performance ◽  
Blood Platelets ◽  
Leukotriene B4 ◽  
Trienoic Acid ◽  
Natural Ligand ◽  
Deficient Mice

Activated blood platelets and macrophages metabolize prostaglandin H2 into thromboxane A2 and 12(S)-hydroxyheptadeca-5Z, 8E, 10E–trienoic acid (12-HHT) in an equimolar ratio through the action of thromboxane synthase. Although it has been shown that 12-HHT is abundant in tissues and bodily fluids, this compound has long been viewed as a by-product lacking any specific function. We show that 12-HHT is a natural ligand for leukotriene B4 (LTB4) receptor-2 (BLT2), a G protein–coupled receptor that was originally identified as a low-affinity receptor for LTB4. BLT2 agonistic activity in lipid fractions from rat small intestine was identified as 12-HHT using high-performance liquid chromatography and mass spectrometry. Exogenously expressed BLT2 in mammalian cells was activated by synthetic 12-HHT, as assessed by guanosine 5′-O-(3-thio) triphosphate binding, the activation of intracellular signaling pathways, and chemotaxis assay. Displacement analysis using [3H]LTB4 showed that 12-HHT binds to BLT2 with a higher affinity than LTB4. Lipid extracts from cyclooxygenase 1–deficient mice failed to activate BLT2. Bone marrow–derived mast cells (BMMCs) isolated from wild-type mice migrated toward a low concentration of 12-HHT, whereas BMMCs from BLT2-deficient mice did not. We conclude that 12-HHT is a natural lipid agonist of BLT2 in vivo and induces chemotaxis of mast cells.

scholarly journals Autotaxin, a Secreted Lysophospholipase D, Is Essential for Blood Vessel Formation during Development

2006 ◽  
Vol 26 (13) ◽  
pp. 5015-5022 ◽  
Author(s):  
Laurens A. van Meeteren ◽  
Paula Ruurs ◽  
Catelijne Stortelers ◽  
Peter Bouwman ◽  
Marga A. van Rooijen ◽  
...  
Keyword(s):  
Lysophosphatidic Acid ◽  
Critical Role ◽  
G Protein Coupled Receptors ◽  
Blood Vessel Formation ◽  
Lysophospholipase D ◽  
Motility Factor ◽  
Nucleotide Pyrophosphatase ◽  
G Protein Coupled ◽  
Deficient Mice

ABSTRACT Autotaxin (ATX), or nucleotide pyrophosphatase-phosphodiesterase 2, is a secreted lysophospholipase D that promotes cell migration, metastasis, and angiogenesis. ATX generates lysophosphatidic acid (LPA), a lipid mitogen and motility factor that acts on several G protein-coupled receptors. Here we report that ATX-deficient mice die at embryonic day 9.5 (E9.5) with profound vascular defects in yolk sac and embryo resembling the Gα13 knockout phenotype. Furthermore, at E8.5, ATX-deficient embryos showed allantois malformation, neural tube defects, and asymmetric headfolds. The onset of these abnormalities coincided with increased expression of ATX and LPA receptors in normal embryos. ATX heterozygous mice appear healthy but show half-normal ATX activity and plasma LPA levels. Our results reveal a critical role for ATX in vascular development, indicate that ATX is the major LPA-producing enzyme in vivo, and suggest that the vascular defects in ATX-deficient embryos may be explained by loss of LPA signaling through Gα13.

scholarly journals G protein-coupled estrogen receptor GPR30 exerts vasoprotective effects in apolipoprotein E-deficient mice

2021 ◽  
Author(s):  
Julian Jehle ◽  
Ulrich Becher ◽  
Moritz Nöthel ◽  
Sandra Adler ◽  
Katharina Groll ◽  
...  
Keyword(s):  
Atherosclerotic Plaque ◽  
At1 Receptor ◽  
Antioxidant Effect ◽  
Plaque Burden ◽  
Ros Production ◽  
Vascular Oxidative Stress ◽  
G Protein Coupled ◽  
Deficient Mice

IntroductionGPR30 is an intracellular transmembrane G protein-coupled receptor that mediates non-genomic estrogen signaling. The GPR30 agonist G-1 modulates glucose homeostasis and vascular function. However, its impact on vascular inflammation and atherogenesis has not yet been investigated in the atherosclerotic apolipoprotein E-deficient(ApoE-/-) mouse model.Material and methodsApoE-/- mice were fed a high-cholesterol diet for 7 weeks while being treated with the selective GPR30 agonist G-1 (n=6-7). After the treatment period, vascular relaxation capacity, vascular oxidative stress, and atherosclerotic plaque burden were assessed. In vitro, reactive oxygen species, expression levels of the angiotensin II type1(AT1) receptor, and proliferation rate were quantified in human coronary artery smooth muscle cells(HCASMC).ResultsG-1 significantly improved glucose tolerance in vivo (142.2±8.1mg/dl vs. 204.6±13.3mg/dl), G-1 reduced vascular oxidative stress (221±88RLU/s/mg vs.1,983±885RLU/s/mg) and improved endothelium-dependent vasodilation (relaxation to 35.1±4.5% vs.63.0±4.6%). Furthermore, treatment with G-1 significantly reduced the atherosclerotic plaque burden of female ApoE-/- mice (56.5±3.7% vs.75.5±2.9%). In vitro, G-1 provoked a significant downregulation of the AT1 receptor in HCASMC (0.67±0.09-fold). Furthermore, G-1 blunted angiotensin II-induced ROS production by HCASMC (817±7RLU/s/mg vs.1,625±105 RLU/s/mg) and diminished HCASMC proliferation (-26.8±2.7% vs.+50.4±1.7%).ConclusionsSelective GPR30 activation improves glucose tolerance in vivo and decreases vascular ROS production in vitro and in vivo. In vitro, the antioxidant effect might be mediated by downregulation of the AT1 receptor. In vivo, the antioxidant effect of G-1 is associated with an improved endothelial function and a reduced atherosclerotic plaque burden in ApoE-deficient mice, indicating beneficial vascular effects of GPR30 activation. GPR30 agonism might thus be a compelling treatment strategy against atherosclerosis.

Reduced thrombus stability in mice lacking the α2A-adrenergic receptor

Blood ◽  
2006 ◽  
Vol 108 (2) ◽  
pp. 510-514 ◽  
Author(s):  
Miroslava Požgajová ◽  
Ulrich J. H. Sachs ◽  
Lutz Hein ◽  
Bernhard Nieswandt
Keyword(s):  
Blood Flow ◽  
Adrenergic Receptor ◽  
Thrombus Formation ◽  
Fold Increase ◽  
Wild Type ◽  
Perfusion Studies ◽  
G Protein Coupled ◽  
Deficient Mice

Platelet activation plays a central role in hemostasis and thrombosis. Many platelet agonists function through G-protein–coupled receptors. Epinephrine activates the α2A-adrenergic receptor (α2A) that couples to Gz in platelets. Although α2A was originally cloned from platelets, its role in thrombosis and hemostasis is still unclear. Through analysis of α2A-deficient mice, variable tail bleeding times were observed. In vitro, epinephrine potentiated activation/aggregation responses of wild-type but not α2A-deficient platelets as determined by flow cytometry and aggregometry, whereas perfusion studies showed no differences in platelet adhesion and thrombus formation on collagen. To test the in vivo relevance of α2A deficiency, mice were subjected to 3 different thrombosis models. As expected, α2A-deficient mice were largely protected from lethal pulmonary thromboembolism induced by the infusion of collagen/epinephrine. In a model of FeCl3-induced injury in mesenteric arterioles, α2A–/– mice displayed a 2-fold increase in embolus formation, suggesting thrombus instability. In a third model, the aorta was mechanically injured, and blood flow was measured with an ultrasonic flow probe. In wild-type mice, all vessels occluded irreversibly, whereas in 24% of α2A-deficient mice, the initially formed thrombi embolized and blood flow was reestablished. These results demonstrate that α2A plays a significant role in thrombus stabilization.

IL-6 is not required for parathyroid hormone stimulation of RANKL expression, osteoclast formation, and bone loss in mice

2005 ◽  
Vol 289 (5) ◽  
pp. E784-E793 ◽  
Author(s):  
Charles A. O'Brien ◽  
Robert L. Jilka ◽  
Qiang Fu ◽  
Scott Stewart ◽  
Robert S. Weinstein ◽  
...  
Keyword(s):  
Parathyroid Hormone ◽  
Bone Loss ◽  
Secondary Hyperparathyroidism ◽  
Osteoclast Formation ◽  
Luciferase Reporter ◽  
Wild Type ◽  
Deficient Diet ◽  
Rankl Mrna ◽  
Deficient Mice

Continuous elevation of parathyroid hormone (PTH) increases osteoclast precursors, the number of osteoclasts on cancellous bone, and bone turnover. The essential molecular mediators of these effects are controversial, however, and both increased receptor activator of NF-κB ligand (RANKL) and IL-6 have been implicated. The goal of these studies was to determine whether continuous elevation of endogenous PTH alters IL-6 gene expression in vivo and whether IL-6 is required for PTH-induced bone loss. To accomplish this, we generated transgenic mice harboring a luciferase reporter gene under the control of IL-6 gene regulatory regions to allow accurate quantification of IL-6 gene activity in vivo. In these mice, induction of secondary hyperparathyroidism using a calcium-deficient diet did not alter IL-6-luciferase transgene expression, whereas RANKL mRNA expression was elevated in bone tissue. Moreover, secondary hyperparathyroidism induced an equivalent amount of bone loss in wild-type and IL-6-deficient mice, and PTH elevated RANKL mRNA and osteoclast formation to the same extent in bone marrow cultures derived from wild-type and IL-6-deficient mice. These results demonstrate that IL-6 is not required for the osteoclast formation and bone loss that accompanies continuous elevation of PTH.

scholarly journals Interaction of Neurochondrin with the Melanin-concentrating Hormone Receptor 1 Interferes with G Protein-coupled Signal Transduction but Not Agonist-mediated Internalization

2006 ◽  
Vol 281 (43) ◽  
pp. 32496-32507 ◽  
Author(s):  
Felix Francke ◽  
Richard J. Ward ◽  
Laura Jenkins ◽  
Elaine Kellett ◽  
Dietmar Richter ◽  
...  
Keyword(s):  
Signal Transduction ◽  
G Protein ◽  
Hormone Receptor ◽  
Mammalian Cells ◽  
Deletion Mapping ◽  
Related Factor ◽  
C Terminus ◽  
Melanin Concentrating Hormone ◽  
G Protein Coupled

Screening of a human brain cDNA library using the C-terminal tail of the melanin-concentrating hormone receptor 1 (MCHR1) as bait in a yeast two-hybrid assay resulted in the identification of the neurite-outgrowth related factor, neurochondrin. This interaction was verified in overlay, pulldown, and co-immunoprecipitation assays. Deletion mapping confined the binding to the C terminus of neurochondrin and to the proximal C terminus of MCHR1, a region known to be involved in G protein binding and signal transduction. This region of the MCHR1 is also able to interact with the actin- and intermediate filament-binding protein, periplakin. Interactions of MCHR1 with neurochondrin and periplakin were competitive, indicating that these two proteins bind to overlapping regions of MCHR1. Although neurochondrin did not interfere with melanin-concentrating hormone-mediated internalization of the receptor, it did inhibit G protein-coupled signal transduction via both Gαi/o and Gαq/11 family G proteins as measured by each of melanin-concentrating hormone-induced G protein-activated inwardly rectifying K+ channel activity of voltage-clamped amphibian oocytes, by calcium mobilization in transfected mammalian cells, and by reduction in the capacity of melanin-concentrating hormone to promote binding of [35S]guanosine 5′-3-O-(thio)triphosphate to both Gαo1 and Gα11. Immunohistochemistry revealed co-expression of neurochondrin and MCHR1 within the rodent brain, suggesting that neurochondrin may be involved in the regulation of MCHR1 signaling and play a role in modulating melanin-concentrating hormone-mediated functions in vivo.

scholarly journals Disruption of claudin-18 diminishes ovariectomy-induced bone loss in mice

2013 ◽  
Vol 304 (5) ◽  
pp. E531-E537 ◽  
Author(s):  
Ha-Young Kim ◽  
Catrina Alarcon ◽  
Sheila Pourteymour ◽  
Jon E. Wergedal ◽  
Subburaman Mohan
Keyword(s):  
Bone Loss ◽  
Osteoclast Differentiation ◽  
Negative Regulator ◽  
Skeletal Phenotype ◽  
Estrogen Effects ◽  
Total Body ◽  
Deficient Mice

Claudin-18 (Cldn-18), a member of the tight junction family of proteins, is a negative regulator of RANKL-induced osteoclast differentiation and bone resorption (BR) in vivo. Since estrogen deficiency decreases bone mass in part by a RANKL-mediated increase in BR, we evaluated whether estrogen regulates Cldn-18 expression in bone. We found that Cldn-18 expression was reduced in the bones of estrogen deficient mice, whereas it was increased by estrogen treatment in osteoblasts and osteoclasts in vitro. We next evaluated the role of Cldn-18 in mediating estrogen-induced bone loss. Cldn-18 knockout (KO) and littermate wild-type (WT) mice were ovariectomized (OVX) or sham operated at 6 wk of age, and the skeletal phenotype was evaluated at 14 wk of age. PIXImus revealed that total body, femur, and lumbar BMD were reduced 8–13% ( P < 0.05) after 8 wk of OVX compared with sham in WT mice. As expected, total body, femur, and lumbar BMD were reduced 14–21% ( P < 0.05) in Cldn-18 KO sham mice compared with sham WT mice. However, ovariectomy failed to induce significant changes in BMD of total body, femur, or vertebra in the Cldn-18 KO mice. μCT analysis of the distal femur revealed that trabecular (Tb) bone volume was decreased 50% in the OVX WT mice compared with sham that was caused by a 26% decrease in Tb number and a 30% increase in Tb separation (all P < 0.05). By contrast, none of the Tb parameters were significantly different in OVX Cldn-18 KO mice compared with sham KO mice. Histomorphometric analyses at the Tb site revealed that neither osteoclast surface nor osteoclast perimeter was increased significantly as a consequence of OVX in either genotype at the time point examined. Based on our findings, we conclude that the estrogen effects on osteoclasts may in part be mediated via regulation of Cldn-18 signaling.

scholarly journals CDK2 inhibitors as candidate therapeutics for cisplatin- and noise-induced hearing loss

2018 ◽  
Vol 215 (4) ◽  
pp. 1187-1203 ◽  
Author(s):  
Tal Teitz ◽  
Jie Fang ◽  
Asli N. Goktug ◽  
Justine D. Bonga ◽  
Shiyong Diao ◽  
...  
Keyword(s):  
Hearing Loss ◽  
Small Molecules ◽  
Kinase Activity ◽  
Noise Induced Hearing Loss ◽  
Cyclin Dependent Kinase ◽  
Adult Mice ◽  
Enhanced Resistance ◽  
Approved Drugs ◽  
Deficient Mice

Hearing loss caused by aging, noise, cisplatin toxicity, or other insults affects 360 million people worldwide, but there are no Food and Drug Administration–approved drugs to prevent or treat it. We screened 4,385 small molecules in a cochlear cell line and identified 10 compounds that protected against cisplatin toxicity in mouse cochlear explants. Among them, kenpaullone, an inhibitor of multiple kinases, including cyclin-dependent kinase 2 (CDK2), protected zebrafish lateral-line neuromasts from cisplatin toxicity and, when delivered locally, protected adult mice and rats against cisplatin- and noise-induced hearing loss. CDK2-deficient mice displayed enhanced resistance to cisplatin toxicity in cochlear explants and to cisplatin- and noise-induced hearing loss in vivo. Mechanistically, we showed that kenpaullone directly inhibits CDK2 kinase activity and reduces cisplatin-induced mitochondrial production of reactive oxygen species, thereby enhancing cell survival. Our experiments have revealed the proapoptotic function of CDK2 in postmitotic cochlear cells and have identified promising therapeutics for preventing hearing loss.

scholarly journals Activation of the Cholinergic Anti-Inflammatory Pathway as a Novel Therapeutic Strategy for COVID-19

2021 ◽  
Vol 11 ◽  
Author(s):  
Zhen Qin ◽  
Kefa Xiang ◽  
Ding-Feng Su ◽  
Yang Sun ◽  
Xia Liu
Keyword(s):  
Vagus Nerve ◽  
Therapeutic Strategy ◽  
Inflammatory Pathway ◽  
Non Invasive ◽  
Anti Inflammatory ◽  
Approved Drugs ◽  
And Control ◽  
Anti Inflammation

The outbreak of coronavirus disease 2019 (COVID-19) underlined the urgent need for alleviating cytokine storm. We propose here that activating the cholinergic anti-inflammatory pathway (CAP) is a potential therapeutic strategy. However, there is currently no approved drugs targeting the regulatory pathway. It is evident that nicotine, anisodamine and some herb medicine, activate the CAP and exert anti-inflammation action in vitro and in vivo. As the vagus nerve affects both inflammation and specific immune response, we propose that vagus nerve stimulation by invasive or non-invasive devices and acupuncture at ST36, PC6, or GV20, are also feasible approaches to activate the CAP and control COVID-19. It is worth to investigate the efficacy and safety of the strategy in patients with COVID-19.

scholarly journals The RFamide receptor DMSR-1 regulates stress-induced sleep in C. elegans

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Michael J Iannacone ◽  
Isabel Beets ◽  
Lindsey E Lopes ◽  
Matthew A Churgin ◽  
Christopher Fang-Yen ◽  
...  
Keyword(s):  
Cell Culture ◽  
G Protein ◽  
Behavioral Response ◽  
Genetic Screen ◽  
Sleep Behavior ◽  
C Elegans ◽  
Cytokine Activation ◽  
C Terminus ◽  
G Protein Coupled

In response to environments that cause cellular stress, animals engage in sleep behavior that facilitates recovery from the stress. In Caenorhabditis elegans, stress-induced sleep(SIS) is regulated by cytokine activation of the ALA neuron, which releases FLP-13 neuropeptides characterized by an amidated arginine-phenylalanine (RFamide) C-terminus motif. By performing an unbiased genetic screen for mutants that impair the somnogenic effects of FLP-13 neuropeptides, we identified the gene dmsr-1, which encodes a G-protein coupled receptor similar to an insect RFamide receptor. DMSR-1 is activated by FLP-13 peptides in cell culture, is required for SIS in vivo, is expressed non-synaptically in several wake-promoting neurons, and likely couples to a Gi/o heterotrimeric G-protein. Our data expand our understanding of how a single neuroendocrine cell coordinates an organism-wide behavioral response, and suggest that similar signaling principles may function in other organisms to regulate sleep during sickness.

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