scholarly journals Roles of Gβγ in membrane recruitment and activation of p110γ/p101 phosphoinositide 3-kinase γ

2002 ◽  
Vol 160 (1) ◽  
pp. 89-99 ◽  
Author(s):  
Carsten Brock ◽  
Michael Schaefer ◽  
H. Peter Reusch ◽  
Cornelia Czupalla ◽  
Manuela Michalke ◽  
...  
Keyword(s):  
G Protein ◽  
Living Cells ◽  
Membrane Lipid ◽  
Cellular Functions ◽  
Direct Stimulation ◽  
Membrane Recruitment ◽  
Ph Domains ◽  
Phosphoinositide 3 Kinase ◽  
Stimulation Of

Receptor-regulated class I phosphoinositide 3-kinases (PI3K) phosphorylate the membrane lipid phosphatidylinositol (PtdIns)-4,5-P2 to PtdIns-3,4,5-P3. This, in turn, recruits and activates cytosolic effectors with PtdIns-3,4,5-P3–binding pleckstrin homology (PH) domains, thereby controlling important cellular functions such as proliferation, survival, or chemotaxis. The class IB p110γ/p101 PI3Kγ is activated by Gβγ on stimulation of G protein–coupled receptors. It is currently unknown whether in living cells Gβγ acts as a membrane anchor or an allosteric activator of PI3Kγ, and which role its noncatalytic p101 subunit plays in its activation by Gβγ. Using GFP-tagged PI3Kγ subunits expressed in HEK cells, we show that Gβγ recruits the enzyme from the cytosol to the membrane by interaction with its p101 subunit. Accordingly, p101 was found to be required for G protein–mediated activation of PI3Kγ in living cells, as assessed by use of GFP-tagged PtdIns-3,4,5-P3–binding PH domains. Furthermore, membrane-targeted p110γ displayed basal enzymatic activity, but was further stimulated by Gβγ, even in the absence of p101. Therefore, we conclude that in vivo, Gβγ activates PI3Kγ by a mechanism assigning specific roles for both PI3Kγ subunits, i.e., membrane recruitment is mediated via the noncatalytic p101 subunit, and direct stimulation of Gβγ with p110γ contributes to activation of PI3Kγ.

Increased fluid absorption and cell volume in isolated rabbit proximal straight tubules after in vivo DOCA administration

1981 ◽  
Vol 241 (5) ◽  
pp. F502-F508 ◽  
Author(s):  
M. A. Knepper ◽  
M. B. Burg
Keyword(s):  
Proximal Tubule ◽  
Cell Volume ◽  
Fluid Transport ◽  
Sodium Intake ◽  
Plasma Concentrations ◽  
Dietary Sodium ◽  
Fluid Absorption ◽  
Direct Stimulation ◽  
Stimulation Of

To investigate whether mineralocorticoids affect the intrinsic capacity of the proximal tubule to absorb sodium and fluid, rabbits were chronically treated a number of ways to systematically vary plasma concentrations of mineralocorticoid hormones. The rate of fluid absorption and tubule dimensions were measured in superficial S2 segments from these rabbits. Chronic administration of deoxycorticosterone acetate (DOCA) was associated with a 67% increase in fluid absorption and a 29% increase in cell volume per unit tubule length. However, neither adrenalectomy nor low sodium diet significantly affected either fluid absorption or cell volume. Furthermore, marked dietary sodium restriction prevented the response to DOCA. We conclude that the DOCA-induced increases in fluid absorption and cell volume do not result from a direct stimulation of the proximal tubular cells by the steroid but more likely are responses to systemic effects of DOCA administration that are dependent on the level of sodium intake. Thus, we find no evidence for a direct mineralocorticoid stimulation of sodium and fluid transport by the S2 portion of the proximal tubule.

scholarly journals Direct Stimulation of Adult Neural Stem Cells In Vitro and Neurogenesis In Vivo by Vascular Endothelial Growth Factor

2006 ◽  
Vol 14 (3) ◽  
pp. 237-248 ◽  
Author(s):  
Anne Schänzer ◽  
Frank-Peter Wachs ◽  
Daniel Wilhelm ◽  
Till Acker ◽  
Christiana Cooper-Kuhn ◽  
...  
Keyword(s):  
Stem Cells ◽  
Vascular Endothelial Growth Factor ◽  
Growth Factor ◽  
Neural Stem Cells ◽  
Vascular Endothelial ◽  
Direct Stimulation ◽  
Endothelial Growth Factor ◽  
Stimulation Of

scholarly journals Impaired noradrenaline-induced lipolysis in white fat of aP2-Ucp1 transgenic mice is associated with changes in G-protein levels

2002 ◽  
Vol 364 (2) ◽  
pp. 369-376 ◽  
Author(s):  
Pavel FLACHS ◽  
JiŘí NOVOTNÝ ◽  
Filip BAUMRUK ◽  
Kristina BARDOVÁ ◽  
Lenka BOUŘOVÁ ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Transgenic Mice ◽  
G Protein ◽  
Energy Status ◽  
Α Subunit ◽  
Fat Depots ◽  
Ucp1 Expression ◽  
White Fat ◽  
Stimulation Of

In vitro experiments suggest that stimulation of lipolysis by catecholamines in adipocytes depends on the energy status of these cells. We tested whether mitochondrial uncoupling proteins (UCPs) that control the efficiency of ATP production could affect lipolysis and noradrenaline signalling in white fat in vivo. The lipolytic effect of noradrenaline was lowered by ectopic UCP1 in white adipocytes of aP2-Ucp1 transgenic mice, overexpressing the UCP1 gene from the aP2 gene promoter, reflecting the magnitude of UCP1 expression, the impaired stimulation of cAMP levels by noradrenaline and the reduction of the ATP/ADP ratio in different fat depots. Thus only subcutaneous but not epididymal fat was affected. UCP1 also down-regulated the expression of hormone-sensitive lipase and lowered its activity, and altered the expression of trimeric G-proteins in adipocytes. The adipose tissue content of the stimulatory G-protein α subunit was increased while that of the inhibitory G-protein α subunits decreased in response to UCP1 expression. Our results support the idea that the energy status of cells, and the ATP/ADP ratio in particular, modulates the lipolytic effects of noradrenaline in adipose tissue in vivo. They also demonstrate changes at the G-protein level that tend to overcome the reduction of lipolysis when ATP level in adipocytes is low. Therefore, respiratory uncoupling may exert a broad effect on hormonal signalling in adipocytes.

scholarly journals Direct stimulation of beta 2-adrenergic receptors in rat anterior pituitary induces the release of adrenocorticotropin in vivo.

1983 ◽  
Vol 80 (21) ◽  
pp. 6728-6731 ◽  
Author(s):  
E. Mezey ◽  
T. D. Reisine ◽  
M. Palkovits ◽  
M. J. Brownstein ◽  
J. Axelrod
Keyword(s):  
Adrenergic Receptors ◽  
Anterior Pituitary ◽  
Direct Stimulation ◽  
Beta 2 ◽  
Stimulation Of

A Novel Role for Thrombin in Hematopoietic Stem/Progenitor Cell Homing.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 3374-3374
Author(s):  
Neeta Shirvaikar ◽  
Ali Jalili ◽  
Mariusz Z. Ratajczak ◽  
Anna Janowska-Wieczorek
Keyword(s):  
Protein Expression ◽  
Lipid Rafts ◽  
Leading Edge ◽  
Membrane Lipid ◽  
Hematopoietic Stem ◽  
Cd34 Cells ◽  
And Migration ◽  
Stimulation Of

Abstract Thrombin, an important serine protease, not only plays a pivotal role in platelet aggregation and coagulation, but also through activation of its receptor, seven transmembrane, G-protein-coupled receptor PAR-1, elicits numerous cellular responses in platelets and endothelial cells such as induction of adhesion molecules, production of chemokines, activation of matrix metalloproteinase (MMP)-2, cytoskeletal reorganization and migration. Thrombin is also one of the inflammatory molecules elevated during G-CSF mobilization of hematopoietic stem/progenitor cells (HSPC) and their collection by leukapheresis. We recently reported that components of leukapheresis products including thrombin enhance in vitro chemotaxis of CD34+ cells towards an SDF-1 gradient and in vivo homing to bone marrow (BM) niches in a murine model (Blood2005; 105:40). In this study we investigated whether thrombin enhances the homing-related responses of human HSPC (CD34+ cells) through MMPs, especially membrane-type (MT)1-MMP which is known to be localized on the leading edge of migrating cells and both activates latent proMMPs (MMP-2, -9) and itself has strong pericellular proteolytic activity. We found that stimulation of CD34+ cells with thrombin upregulates mRNA for MT1-MMP and MMP-9 as well as MT1-MMP protein expression (Western blot, flow cytometry) and proMMP-2 and proMMP-9 secretion (zymography). Thrombin was also found to (i) prime trans-Matrigel chemoinvasion of CD34+ cells towards a low SDF-1 gradient (20 ng/mL), which was inhibited by epigallocatechin-3-gallate, a potent inhibitor of MT1-MMP, and (ii) activate MMP-2 in of co-cultures of CD34+ cells with stromal cells (BM fibroblasts and HUVEC) which secrete proMMP-2. We also found that SDF-1 upregulates mRNA and protein expression of MT1-MMP. Moreover, using confocal microscopy we demonstrate for the first time that in CD34+ cells, PAR-1, like CXCR4, is localized in the GM1 fraction of lipid rafts and stimulation of these cells with thrombin as well as SDF-1 increases incorporation of MT1-MMP into membrane lipid rafts. Furthermore, disruption of lipid raft formation by the cholesterol-depleting agent methyl-b-cyclodextrin inhibits MT1-MMP incorporation into membrane lipid rafts and also trans-Matrigel chemoinvasion of CD34+ cells towards SDF-1. Thus we conclude that thrombin, through PAR-1 signalling and the SDF-1-CXCR4 axis, upregulates the incorporation of MT1-MMP into membrane lipid rafts and the interaction of these axes enhances the homing-related responses of HSPC towards SDF-1.

A key role for Toll-like receptor-3 in disrupting the hemostasis balance on endothelial cells

Blood ◽  
2009 ◽  
Vol 113 (3) ◽  
pp. 714-722 ◽  
Author(s):  
Aya Shibamiya ◽  
Karin Hersemeyer ◽  
Thomas Schmidt Wöll ◽  
Daniel Sedding ◽  
Jan-Marcus Daniel ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Tissue Factor ◽  
Hemorrhagic Fever ◽  
Poly I:C ◽  
Toll Like Receptor ◽  
Virus Infections ◽  
Direct Stimulation ◽  
Viral Dsrna ◽  
Stimulation Of

AbstractVarious virus infections cause dysfunctional hemostasis and in some instances lead to the development of viral hemorrhagic fever syndrome. How do diverse viruses induce the expression of tissue factor on vascular cells? We hypothesize that a direct stimulation of pattern recognition receptors (PRR) by viral nucleic acids may be the key. Double-stranded RNA (dsRNA) is produced by many viruses and is recognized by various PRR, including Toll-like receptor-3 (TLR3). We have investigated whether poly I:C, a model for viral dsRNA, can influence cellular hemostasis. Poly I:C could up-regulate tissue factor and down-regulate thrombomodulin expression on endothelial cells but not on monocytes. The response to poly I:C was diminished upon small interfering RNA (siRNA)–mediated inhibition of TLR3, but not other PRR. In vivo, application of poly I:C induced similar changes in the aortic endothelium of mice as determined by enface microscopy. D-dimer, a circulating marker for enhanced coagulation and fibrinolysis, and tissue fibrin deposition was elevated. All the hemostasis-related responses to poly I:C, but not cytokine secretion, were blunted in TLR3−/− mice. Hence, the activation of TLR3 can induce the procoagulant state in the endothelium, and this could be relevant for understanding the mechanisms of viral stimulation of hemostasis.

scholarly journals Ethanol raises prostacyclin in vivo and in vitro

Blood ◽  
1984 ◽  
Vol 64 (3) ◽  
pp. 679-682
Author(s):  
R Landolfi ◽  
M Steiner
Keyword(s):  
Endothelial Cells ◽  
Significant Rise ◽  
Blood Alcohol ◽  
Elevated Plasma ◽  
Direct Stimulation ◽  
Baseline Values ◽  
Induced Changes ◽  
Stimulation Of

Moderate doses of ethanol were shown to induce a significant rise in prostacyclin (PGI2) concentration in cultures of endothelial cells derived from umbilical veins. Administration of 32 g of ethanol to six volunteers elevated plasma levels of PGI2 in parallel with those of blood alcohol. Although not specific for ethanol, this alcohol induced the largest change in PGI2. Withdrawal of the stimulant alcohol caused prompt reduction of the elevated prostacyclin to baseline values. The activity of ethanol appears to be due to a direct stimulation of cyclooxygenase. The release of [14C]arachidonic acid from prelabeled endothelial cells was decreased by ethanol. PGE2 production was also enhanced by exposure of endothelial cells to ethanol. The physiologic significance of these alcohol-induced changes in PGI2 levels remains to be established.

scholarly journals Identification of ILK as a new partner of the ADAM12 disintegrin and metalloprotease in cell adhesion and survival

2012 ◽  
Vol 23 (17) ◽  
pp. 3461-3472 ◽  
Author(s):  
Anthony Leyme ◽  
Katia Bourd-Boittin ◽  
Dominique Bonnier ◽  
Anaïs Falconer ◽  
Yannick Arlot-Bonnemains ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Focal Adhesions ◽  
Interaction Network ◽  
Integrative Approach ◽  
Β1 Integrin ◽  
Cellular Functions ◽  
Survival Pathway ◽  
Integrin Linked Kinase ◽  
Phosphoinositide 3 Kinase ◽  
Stimulation Of

Based on its shedding and binding activities, the disintegrin and metalloprotease 12 (ADAM12) has been implicated in cell signaling. Here we investigate the intracellular protein interaction network of the transmembrane ADAM12L variant using an integrative approach. We identify the integrin-linked kinase (ILK) as a new partner for ADAM12L cellular functions. We demonstrate that ADAM12L coimmunoprecipitates with ILK in cells and that its cytoplasmic tail is required for this interaction. In human cultured hepatic stellate cells (HSCs), which express high levels of endogenous ADAM12L and ILK, the two proteins are redistributed to focal adhesions upon stimulation of a β1 integrin–dependent pathway. We show that down-regulation of ADAM12L in HSCs leads to cytoskeletal disorganization and loss of adhesion. Conversely, up-regulation of ADAM12L induces the Akt Ser-473 phosphorylation-dependent survival pathway via stimulation of β1 integrins and activation of phosphoinositide 3-kinase (PI3K). Depletion of ILK inhibits this effect, which is independent of ADAM12L proteolytic activity and involves its cytoplasmic domain. We further demonstrate that overexpression of ADAM12L promotes kinase activity from ILK immunoprecipitates. Our data suggest a new role for ADAM12L in mediating the functional association of ILK with β1 integrin to regulate cell adhesion/survival through a PI3K/Akt signaling pathway.

scholarly journals Direct Stimulation of the λpaQPromoter by the Transcription Effector Guanosine-3′,5′-(bis)pyrophosphate in a Definedin VitroSystem

2004 ◽  
Vol 279 (19) ◽  
pp. 19860-19866 ◽  
Author(s):  
Katarzyna Potrykus ◽  
Grzegorz Wegrzyn ◽  
V. James Hernandez
Keyword(s):  
Rna Polymerase ◽  
Passive Control ◽  
Stringent Response ◽  
Translation System ◽  
Trna Genes ◽  
Direct Stimulation ◽  
Nutritional Deprivation ◽  
Stimulation Of

The bacterial response to nutritional deprivation, called the stringent response, results in the introduction of the specific nucleotide guanosine-3′,5′-(bis) pyrophosphate (ppGpp). This nucleotide interacts with RNA polymerase and alters its action so that transcription from certain promoters is inhibited, whereas transcription from others seems to be activated. The exact mechanism of transcriptional stimulation by ppGppin vivoremains unknown. A passive control model has been proposed according to which transcription inhibition during the stringent response at several very active promoters, like those for rRNA and tRNA genes, makes more free RNA polymerase (RNAP) molecules available for transcription at promoters with weak binding affinities for RNAP, thus leading to their passive activation. Among promoters whose transcription is activated by ppGppin vivois the histidine operon promoter (hisGp). However,in vitroit is only possible to demonstrate this effect in a coupled transcription-translation system. Here we demonstrate, using anotherin vivoppGpp-stimulated promoter, the phage λpaQpromoter, that activation by ppGpp in a definedin vitrosystem is direct. A systematic study of ppGpp effects on the stimulation ofpaQrevealed that, as in the case of promoters inhibited by this nucleotide, ppGpp decreases the half-life ofpaQopen complexes. Our results also indicate that the equilibrium binding affinity of RNA polymerase topaQseems not to be affected in the presence of ppGpp. Our data indicate that the mechanism underlying ppGpp stimulation ofpaQis due to an increased rate of productive open complex formation.

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