Dynamics of adenylate cyclase regulation via heterotrimeric G-proteins

2014 ◽  
Vol 42 (2) ◽  
pp. 239-243 ◽  
Author(s):  
Markus Milde ◽  
Ruth C. Werthmann ◽  
Kathrin von Hayn ◽  
Moritz Bünemann
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Umbilical Vein ◽  
Underlying Mechanism ◽  
Protein Activity ◽  
Gi Protein ◽  
Continuous Presence ◽  
Umbilical Vein Endothelial Cells ◽  
Camp Levels ◽  
Gi Proteins

A wide variety of G-protein-coupled receptors either activate or inhibit ACs (adenylate cyclases), thereby regulating cellular cAMP levels and consequently inducing proper physiological responses. Stimulatory and inhibitory G-proteins interact directly with ACs, whereas Gq-coupled receptors exert their effects primarily via Ca2+. Using the FRET-based cAMP sensor Epac1 (exchange protein directly activated by cAMP 1)–cAMPS (adenosine 3′,5′-cyclic monophosphorothioate), we studied cAMP levels in single living VSMCs (vascular smooth muscle cells) or HUVECs (human umbilical vein endothelial cells) with subsecond temporal resolution. Stimulation of purinergic (VSMCs) or thrombin (HUVECs) receptors rapidly decreased cAMP levels in the presence of the β-adrenergic agonist isoprenaline via a rise in Ca2+ and subsequent inhibition of AC5 and AC6. Specifically in HUVECs, we observed that, in the continuous presence of thrombin, cAMP levels climbed slowly after the initial decline with a delay of a little less than 1 min. The underlying mechanism includes phospholipase A2 activity and cyclo-oxygenase-mediated synthesis of prostaglandins. We studied further the dynamics of the inhibition of ACs via Gi-proteins utilizing FRET imaging to resolve interactions between fluorescently labelled Gi-proteins and AC5. FRET between Gαi1 and AC5 developed at much lower concentration of agonist compared with the overall Gi-protein activity. We found the dissociation of Gαi1 subunits and AC5 to occur slower than the Gi-protein deactivation. This led us to the conclusion that AC5, by binding active Gαi1, interferes with G-protein deactivation and reassembly and thereby might sensitize its own regulation.

scholarly journals Optogenetic activation of heterotrimeric Gi proteins by LOV2GIVe— a rationally engineered modular protein

2020 ◽  
Author(s):  
Mikel Garcia-Marcos ◽  
Kshitij Parag-Sharma ◽  
Arthur Marivin ◽  
Marcin Maziarz ◽  
Alex Luebbers ◽  
...  
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Protein Domain ◽  
Protein Activity ◽  
Signal Transducers ◽  
Non Invasive ◽  
Experimental Systems ◽  
Graphical Summary ◽  
Extracellular Stimuli ◽  
Gi Proteins

ABSTRACTHeterotrimeric G-proteins are signal transducers that mediate the action of many natural extracellular stimuli as well as of many therapeutic agents. Non-invasive approaches to manipulate the activity of G-proteins with high precision are crucial to understand their regulation in space and time. Here, we engineered LOV2GIVe, a modular protein that allows the activation of Gi proteins with blue light. This optogenetic construct relies on a versatile design that differs from tools previously developed for similar purposes, i.e. metazoan opsins, which are light-activated GPCRs. To make LOV2GIVe, we fused a peptide derived from a non-GPCR protein that activates Gαi (but not Gαs, Gαq, or Gα12) to a small plant protein domain, such that light uncages the G-protein activating module. Targeting LOV2GIVe to cell membranes allowed for light-dependent activation of Gi proteins in different experimental systems. In summary, LOV2GIVe expands the armamentarium and versatility of tools available to manipulate heterotrimeric G-protein activity.GRAPHICAL SUMMARY

scholarly journals G Proteins and GPCRs in C. elegans Development: A Story of Mutual Infidelity

2018 ◽  
Vol 6 (4) ◽  
pp. 28 ◽  
Author(s):  
Daniel Matúš ◽  
Simone Prömel
Keyword(s):  
Signaling Pathways ◽  
G Protein ◽  
G Proteins ◽  
Cell Polarity ◽  
Protein Activity ◽  
Independent Manner ◽  
C Elegans ◽  
Downstream Effectors ◽  
Complex Signaling ◽  
G Protein Coupled

Many vital processes during C. elegans development, especially the establishment and maintenance of cell polarity in embryogenesis, are controlled by complex signaling pathways. G protein-coupled receptors (GPCRs), such as the four Frizzled family Wnt receptors, are linchpins in regulating and orchestrating several of these mechanisms. However, despite being GPCRs, which usually couple to G proteins, these receptors do not seem to activate classical heterotrimeric G protein-mediated signaling cascades. The view on signaling during embryogenesis is further complicated by the fact that heterotrimeric G proteins do play essential roles in cell polarity during embryogenesis, but their activity is modulated in a predominantly GPCR-independent manner via G protein regulators such as GEFs GAPs and GDIs. Further, the triggered downstream effectors are not typical. Only very few GPCR-dependent and G protein-mediated signaling pathways have been unambiguously defined in this context. This unusual and highly intriguing concept of separating GPCR function and G-protein activity, which is not restricted to embryogenesis in C. elegans but can also be found in other organisms, allows for essential and multi-faceted ways of regulating cellular communication and response. Although its relevance cannot be debated, its impact is still poorly discussed, and C. elegans is an ideal model to understand the underlying principles.

scholarly journals Dihydromyricetin Attenuates TNF-α-Induced Endothelial Dysfunction through miR-21-Mediated DDAH1/ADMA/NO Signal Pathway

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Dafeng Yang ◽  
Shenglan Tan ◽  
Zhousheng Yang ◽  
Pei Jiang ◽  
Caie Qin ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Endothelial Dysfunction ◽  
Umbilical Vein ◽  
Underlying Mechanism ◽  
Tube Formation ◽  
Signal Pathway ◽  
Dependent Manner ◽  
Necrosis Factor Alpha ◽  
Atherosclerotic Process ◽  
Umbilical Vein Endothelial Cells

Accumulating studies demonstrate that dihydromyricetin (DMY), a compound extracted from Chinese traditional herb, Ampelopsis grossedentata, attenuates atherosclerotic process by improvement of endothelial dysfunction. However, the underlying mechanism remains poorly understood. Thus, the aim of this study is to investigate the potential mechanism behind the attenuating effects of DMY on tumor necrosis factor alpha- (TNF-α-) induced endothelial dysfunction. In response to TNF-α, microRNA-21 (miR-21) expression was significantly increased in human umbilical vein endothelial cells (HUVECs), in line with impaired endothelial dysfunction as evidenced by decreased tube formation and migration, endothelial nitric oxide synthase (eNOS) (ser1177) phosphorylation, dimethylarginine dimethylaminohydrolases 1 (DDAH1) expression and metabolic activity, and nitric oxide (NO) concentration as well as increased asymmetric dimethylarginine (ADMA) levels. In contrast, DMY or blockade of miR-21 expression ameliorated endothelial dysfunction in HUVECs treated with TNF-α through downregulation of miR-21 expression, whereas these effects were abolished by overexpression of miR-21. In addition, using a nonspecific NOS inhibitor, L-NAME, also abrogated the attenuating effects of DMY on endothelial dysfunction. Taken together, these data demonstrated that miR-21-mediated DDAH1/ADMA/NO signal pathway plays an important role in TNF-α-induced endothelial dysfunction, and DMY attenuated endothelial dysfunction induced by TNF-α in a miR-21-dependent manner.

Thrombin receptor-activating peptide sensitizes the human endothelial thrombin receptor

1995 ◽  
Vol 268 (1) ◽  
pp. C36-C44 ◽  
Author(s):  
H. J. Kruse ◽  
C. Mayerhofer ◽  
W. Siess ◽  
P. C. Weber
Keyword(s):  
Endothelial Cells ◽  
Ligand Binding ◽  
Umbilical Vein ◽  
Thrombin Receptor ◽  
Receptor Desensitization ◽  
Short Term ◽  
Tethered Ligand ◽  
Continuous Presence ◽  
Sensitizing Effect ◽  
Umbilical Vein Endothelial Cells

Receptor-operated effects of alpha-thrombin and of the thrombin receptor-activating peptide TRAP14 on cytoplasmic Ca2+ concentration ([Ca2+]i) were examined in fura 2-loaded endothelial cells. Experiments with hirudin showed that alpha-thrombin-induced Ca2+ influx requires the continuous presence of active alpha-thrombin. YFLLRNP, known to antagonize alpha-thrombin- and TRAP7-induced [Ca2+]i transients in platelets, did not antagonize [Ca2+]i transients in response to alpha-thrombin and TRAP14 in human umbilical vein endothelial cells (HUVEC). Repetitive short-term stimulations with alpha-thrombin desensitized [Ca2+]i transients to subsequent stimulations with either alpha-thrombin or TRAP14. In contrast, repeated short-term stimulations with TRAP14 sensitized [Ca2+]i transients to subsequent stimulations with either agonist. Blockade of Ca2+ influx by SKF-96365 abolished the sensitizing effect of TRAP14. The results indicate distinct characteristics of platelet and endothelial thrombin receptors and suggest that alpha-thrombin and TRAP14 activate the receptor differently. It appears that receptor desensitization occurs independently of TRAP14 binding and, hence, tethered ligand binding to and activation of the receptor. Persistent receptor desensitization after alpha-thrombin seems to depend on both alpha-thrombin binding to the hirudin-like receptor domain and the irreversible proteolytic cleavage of the receptor. It does not involve the TRAP14/tethered ligand binding site of the receptor. TRAP14 primes the receptor by a mechanism mediated by Ca2+ influx.

scholarly journals Yeast G-proteins mediate directional sensing and polarization behaviors in response to changes in pheromone gradient direction

2013 ◽  
Vol 24 (4) ◽  
pp. 521-534 ◽  
Author(s):  
Travis I. Moore ◽  
Hiromasa Tanaka ◽  
Hyung Joon Kim ◽  
Noo Li Jeon ◽  
Tau-Mu Yi
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Cell Polarity ◽  
Yeast Cells ◽  
Dependent Manner ◽  
Protein Activity ◽  
Gradient Sensing ◽  
Heterotrimeric G Protein ◽  
Low Concentrations ◽  
High Concentrations

Yeast cells polarize by projecting up mating pheromone gradients, a classic cell polarity behavior. However, these chemical gradients may shift direction. We examine how yeast cells sense and respond to a 180o switch in the direction of microfluidically generated pheromone gradients. We identify two behaviors: at low concentrations of α-factor, the initial projection grows by bending, whereas at high concentrations, cells form a second projection toward the new source. Mutations that increase heterotrimeric G-protein activity expand the bending-growth morphology to high concentrations; mutations that increase Cdc42 activity result in second projections at low concentrations. Gradient-sensing projection bending requires interaction between Gβγ and Cdc24, whereas gradient-nonsensing projection extension is stimulated by Bem1 and hyperactivated Cdc42. Of interest, a mutation in Gα affects both bending and extension. Finally, we find a genetic perturbation that exhibits both behaviors. Overexpression of the formin Bni1, a component of the polarisome, makes both bending-growth projections and second projections at low and high α-factor concentrations, suggesting a role for Bni1 downstream of the heterotrimeric G-protein and Cdc42 during gradient sensing and response. Thus we demonstrate that G-proteins modulate in a ligand-dependent manner two fundamental cell-polarity behaviors in response to gradient directional change.

scholarly journals High-glucose incubation of human umbilical-vein endothelial cells does not alter expression and function either of G-protein α-subunits or of endothelial NO synthase

1996 ◽  
Vol 315 (1) ◽  
pp. 281-287 ◽  
Author(s):  
Gudrun MANCUSI ◽  
Caroline HUTTER ◽  
Sabina BAUMGARTNER-PARZER ◽  
Kurt SCHMIDT ◽  
Wolfgang SCHÜTZ ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
G Protein ◽  
High Glucose ◽  
Umbilical Vein ◽  
No Synthase ◽  
Functional Changes ◽  
Endothelial No Synthase ◽  
Umbilical Vein Endothelial Cells ◽  
And Function ◽  
Cells Cultured

Alterations in G-protein-controlled signalling pathways (primarily pathways controlled by Gs and Gi) have been reported to occur in animal models of diabetes mellitus. We have therefore studied the effect of a long-term exposure of human umbilical vein endothelial cells to elevated concentrations of glucose on expression and function of G-protein subunits and endothelial NO synthase. Long-term incubation in high glucose (30 mM for 15 days) did not affect the levels of Giα-2, Gqα, the splice variants (long and short form) of Gsα, and the G-protein β-subunits or adenylate cyclase activity: basal, as well as isoprenaline-, forskolin- and guanosine 5´-[γ-thio]triphosphate-stimulated enzyme activities were comparable in high- and low-glucose-treated cells, thus ruling out any functional changes in the stimulatory pathway. Pretreatment of endothelial cells with pertussis toxin blocked a substantial fraction (50%) of the mitogenic response to serum factor(s) which depend(s) on functional Gi2. The sensitivity of cells cultured in high glucose was comparable with that of the paired controls maintained in normal glucose (EC50 = 3.1±0.5 and 3.3±0.4 ng/ml respectively). Similarly, we failed to detect any differences in endothelial NO synthase expression, or intracellular distribution and basal activity of the enzyme in endothelial cells cultured in high glucose. Stimulation of NO synthase in intact cells revealed a comparable response to the calcium ionophore (A23187). In contrast, stimulation with histamine (which acts via H1-receptors predominantly coupled to Gq) resulted in a significantly increased response in the cells maintained in high glucose. These data are suggestive of an altered H1-histamine receptor–Gq–phospholipase C pathway in endothelial cells cultured in high glucose concentrations, but rule out any glucose-induced functional changes in Gs- and Gi-controlled signalling pathways.

scholarly journals AKT/FOXO1 axis links cross-talking of endothelial cell and pericyte in TIE2-mutated venous malformations

2020 ◽  
Author(s):  
Hongbing Jiang ◽  
Yameng Si ◽  
Jiadong Huang ◽  
Xiang Li ◽  
Yu Fu ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Umbilical Vein ◽  
Underlying Mechanism ◽  
Tube Formation ◽  
Tyrosine Kinase Receptor ◽  
Venous Malformations ◽  
Activating Mutations ◽  
Mechanism Of Interaction ◽  
Umbilical Vein Endothelial Cells

Abstract Background: Venous malformations (VMs), most of which associated with activating mutations in the endothelial cells (ECs) tyrosine kinase receptor TIE2, are characterized by dilated and immature veins with scarce smooth muscle cells (SMCs) coverage. However, the underlying mechanism of interaction between ECs and SMCs responsible for VMs has not been fully understood. Methods : Here, we screened 5 patients with TIE2-L914F mutation who were diagnosed with VMs by SNP sequencing, and we compared the expression of platelet-derived growth factor beta (PDGFB) and α-SMA in TIE2 mutant veins and normal veins by immunohistochemistry. In vitro, we generated TIE2-L914F-expressing human umbilical vein endothelial cells (HUVECs) and performed BrdU, CCK-8, transwell and tube formation experiments on none-transfected and transfected ECs. Then we investigated the effects of rapamycin (RAPA) on cellular characteristics. Next we established a co-culture system and investigated the role of AKT/FOXO1/PDGFB in regulating cross-talking of mutant ECs and SMCs. Results: VMs with TIE2-L914F mutation showed lower expression of PDGFB and α-SMA than normal veins. TIE2 mutant ECs revealed enhanced cell viability and motility, and decreased tube formation, whereas these phenotypes could be reversed by rapamycin. Mechanistically, RAPA ameliorated the physiological function of mutant ECs by inhibiting AKT-mTOR pathway, but also facilitated the nuclear location of FOXO1 and the expression of PDGFB in mutant ECs, and then improved paracrine interactions between ECs and SMCs. Moreover, TIE2 mutant ECs strongly accelerated the transition of SMCs from contractile phenotype to synthetic phenotype, whereas RAPA could prevent the phenotype transition of SMCs. Conclusions: Our data demonstrate a previously unknown mechanistic linkage of AKT-mTOR/FOXO1 pathway between mutant ECs and SMCs in modulating venous dysmorphogenesis, and AKT/FOXO1 axis might be a potential therapeutic target for the recovery of TIE2-mutation causing VMs.

scholarly journals A predictive computational model reveals that GIV/girdin serves as a tunable valve for EGFR-stimulated cyclic AMP signals

2019 ◽  
Vol 30 (13) ◽  
pp. 1621-1633 ◽  
Author(s):  
Michael Getz ◽  
Lee Swanson ◽  
Debashish Sahoo ◽  
Pradipta Ghosh ◽  
Padmini Rangamani
Keyword(s):  
Growth Factor ◽  
G Protein ◽  
G Proteins ◽  
Cross Talk ◽  
Tyrosine Kinases ◽  
Control Valve ◽  
Camp Signaling ◽  
Nucleotide Exchange ◽  
Camp Concentration ◽  
Camp Levels

Cellular levels of the versatile second messenger cyclic (c)AMP are regulated by the antagonistic actions of the canonical G protein → adenylyl cyclase pathway that is initiated by G-protein–coupled receptors (GPCRs) and attenuated by phosphodiesterases (PDEs). Dysregulated cAMP signaling drives many diseases; for example, its low levels facilitate numerous sinister properties of cancer cells. Recently, an alternative paradigm for cAMP signaling has emerged in which growth factor–receptor tyrosine kinases (RTKs; e.g., EGFR) access and modulate G proteins via a cytosolic guanine-nucleotide exchange modulator (GEM), GIV/girdin; dysregulation of this pathway is frequently encountered in cancers. In this study, we present a network-based compartmental model for the paradigm of GEM-facilitated cross-talk between RTKs and G proteins and how that impacts cellular cAMP. Our model predicts that cross-talk between GIV, G αs, and G αi proteins dampens ligand-stimulated cAMP dynamics. This prediction was experimentally verified by measuring cAMP levels in cells under different conditions. We further predict that the direct proportionality of cAMP concentration as a function of receptor number and the inverse proportionality of cAMP concentration as a function of PDE concentration are both altered by GIV levels. Taking these results together, our model reveals that GIV acts as a tunable control valve that regulates cAMP flux after growth factor stimulation. For a given stimulus, when GIV levels are high, cAMP levels are low, and vice versa. In doing so, GIV modulates cAMP via mechanisms distinct from the two most often targeted classes of cAMP modulators, GPCRs and PDEs.

scholarly journals Dexmedetomidine Attenuates Monocyte-Endothelial Adherence via Inhibiting Connexin43 on Vascular Endothelial Cells

2020 ◽  
Vol 2020 ◽  
pp. 1-10 ◽  
Author(s):  
Yunfei Chai ◽  
Runying Yu ◽  
Yong Liu ◽  
Sheng Wang ◽  
Dongdong Yuan ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Vascular Endothelial Cells ◽  
Umbilical Vein ◽  
Underlying Mechanism ◽  
Mapk Signaling ◽  
Vascular Endothelial ◽  
Cx43 Expression ◽  
Multiple Organs ◽  
Key Factor ◽  
Umbilical Vein Endothelial Cells

Current studies have identified the multifaceted protective functions of dexmedetomidine on multiple organs. For the first time, we clarify effects of dexmedetomidine on monocyte-endothelial adherence and whether its underlying mechanism is relative to connexin43 (Cx43), a key factor regulating monocyte-endothelial adherence. U937 monocytes and human umbilical vein endothelial cells (HUVECs) were used to explore monocyte-endothelial adherence. Two special siRNAs were designed to knock down Cx43 expression on HUVECs. U937-HUVEC adhesion, adhesion-related molecules, and the activation of the MAPK (p-ERK1/2, p-p38, and p-JNK1/2) signaling pathway were detected. Dexmedetomidine, at its clinically relevant concentrations (0.1 nM and 1 nM), was given as pretreatments to HUVECs. Its effects on Cx43 and U937-HUVEC adhesion were also investigated. The results show that inhibiting Cx43 on HUVECs could attenuate the contents of MCP-1, soluble ICAM-1 (sICAM-1), soluble VCAM-1 (sVCAM-1), and the nonprocessed variants of the adhesion molecules ICAM-1 and VCAM-1 and ultimately result in U937-HUVEC adhesion decrease. Meanwhile, the activation of MAPKs was also inhibited. U0126 (inhibiting p-ERK1/2) and SB202190 (inhibiting p38) decreased the contents of MCP-1, sICAM-1, and sVCAM-1, but SP600125 (inhibiting p-JNK1/2) had none of these effects. ICAM-1 and VCAM-1 could be regulated in a similar way. Dexmedetomidine pretreatment inhibited Cx43 on HUVECs, the activation of MAPKs, and U937-HUVEC adhesion. Therefore, we conclude that dexmedetomidine attenuates U937-HUVEC adhesion via inhibiting Cx43 on HUVECs modulating the activation of MAPK signaling pathways.

Two types of G proteins involved in regulation of phosphoinositide turnover in pulmonary endothelial cells

1991 ◽  
Vol 261 (4) ◽  
pp. 118-122 ◽  
Author(s):  
V. A. Tkachuk ◽  
T. A. Voyno-Yasenetskaya
Keyword(s):  
Endothelial Cells ◽  
Phospholipase C ◽  
G Proteins ◽  
Hormonal Regulation ◽  
Umbilical Vein ◽  
Dependent Manner ◽  
Hormone Regulation ◽  
Pi Turnover ◽  
Umbilical Vein Endothelial Cells ◽  
Stimulation Of

The involvement of G proteins in hormonal regulation of phospholipase C in bovine pulmonary arterial endothelial cells and human umbilical vein endothelial cells has been investigated. Histamine and bradykinin stimulated phosphoinositol (PI) turnover in a dose-dependent manner, and phorbol-myristate-acetate inhibited hormone-dependent activation of PI turnover, indicating a feedback control of this process. Activation of PI turnover by histamine and bradykinin is guanine nucleotide-dependent. Stimulation of the endothelial cell G proteins by guanosine 5'-0-(3-thiotriphosphate) leads to the potentiation of hormone-induced activation of PI turnover, whereas guanosine 5'-0-(2-thiodiphosphate), which inactivates G proteins, blocks the hormone-dependent PI turnover. Pertussis toxin blocked the histamine-dependent stimulation but did not affect the bradykinin-dependent stimulation of phospholipase C. By contrast, botulinurn toxin (C2 + C3 components) blocked the bradykinin-dependent stimulation of phospholipase C but did not affect the histamine-dependent stimulation of this enzyme. These data suggest that at least two different G proteins are involved in hormone-dependent stimulation of phospholipase C in endothelial cells. bacterial toxins; hormone regulation; phospholipase C

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