scholarly journals Co-operative Cdc42 and Rho signalling mediates ephrinB-triggered endothelial cell retraction

2007 ◽  
Vol 404 (1) ◽  
pp. 23-29 ◽  
Author(s):  
Gillian Groeger ◽  
Catherine D. Nobes
Keyword(s):  
Rho Kinase ◽  
Receptor Activation ◽  
Atpase Inhibitor ◽  
Complex Interplay ◽  
Eph Receptor ◽  
Actomyosin Contractility ◽  
Endothelial Cell Retraction ◽  
Rock Inhibition ◽  
Cell Retraction ◽  
Stimulation Of

Cell repulsion responses to Eph receptor activation are linked to rapid actin cytoskeletal reorganizations, which in turn are partially mediated by Rho–ROCK (Rho kinase) signalling, driving actomyosin contractility. In the present study, we show that Rho alone is not sufficient for this repulsion response. Rather, Cdc42 (cell division cycle 42) and its effector MRCK (myotonic dystrophy kinase-related Cdc42-binding kinase) are also critical for ephrinB-induced cell retraction. Stimulation of endothelial cells with ephrinB2 triggers rapid, but transient, cell retraction. We show that, although membrane retraction is fully blocked by blebbistatin (a myosin-II ATPase inhibitor), it is only partially blocked by inhibiting Rho–ROCK signalling, suggesting that there is ROCK-independent signalling to actomyosin contractility downstream of EphBs. We find that a combination of either Cdc42 or MRCK inhibition with ROCK inhibition completely abolishes the repulsion response. Additionally, endocytosis of ephrin–Eph complexes is not required for initial cell retraction, but is essential for subsequent Rac-mediated re-spreading of cells. Our data reveal a complex interplay of Rho, Rac and Cdc42 in the process of EphB-mediated cell retraction–recovery responses.

Dichotomous Regulation of Myosin Phosphorylation and Shape Change by Rho-Kinase and Calcium in Intact Human Platelets

Blood ◽  
1999 ◽  
Vol 94 (5) ◽  
pp. 1665-1672 ◽  
Author(s):  
Markus Bauer ◽  
Michaela Retzer ◽  
Jonathan I. Wilde ◽  
Petra Maschberger ◽  
Markus Essler ◽  
...  
Keyword(s):  
Kinase Inhibitor ◽  
Shape Change ◽  
Rho Kinase ◽  
Adenosine Diphosphate ◽  
Receptor Activation ◽  
Human Platelets ◽  
Peptide Ligand ◽  
Thromboxane Receptor ◽  
Mlc Phosphorylation ◽  
Stimulation Of

Both Rho-kinase and the Ca2+/calmodulin-dependent myosin light chain (MLC) kinase increase the phosphorylation of MLC. We show that upon thrombin receptor stimulation by low-dose thrombin or the peptide ligand YFLLRNP, or upon thromboxane receptor activation by U46619, shape change and MLC phosphorylation in human platelets proceed through a pathway that does not involve an increase in cytosolic Ca2+. Under these conditions, Y-27632, a specific Rho-kinase inhibitor, prevented shape change and reduced the stimulation of MLC-phosphorylation. In contrast, Y-27632 barely affected shape change and MLC-phosphorylation by adenosine diphosphate (ADP), collagen-related peptide, and ionomycin that were associated with an increase in cytosolic Ca2+ and inhibited by BAPTA-AM/EGTA treatment. Furthermore, C3 exoenzyme, which inactivates Rho, inhibited preferentially the shape change induced by YFLLRNP compared with ADP and ionomycin. The results indicate that the Rho/Rho-kinase pathway is pivotal in mediating the MLC phosphorylation and platelet shape change by low concentrations of certain G protein–coupled platelet receptors, independent of an increase in cytosolic Ca2+. Our study defines 2 alternate pathways, Rho/Rho-kinase and Ca2+/calmodulin-regulated MLC-kinase, that lead independently of each other through stimulation of MLC-phosphorylation to the same physiological response in human platelets (ie, shape change).

Dichotomous Regulation of Myosin Phosphorylation and Shape Change by Rho-Kinase and Calcium in Intact Human Platelets

Blood ◽  
1999 ◽  
Vol 94 (5) ◽  
pp. 1665-1672 ◽  
Author(s):  
Markus Bauer ◽  
Michaela Retzer ◽  
Jonathan I. Wilde ◽  
Petra Maschberger ◽  
Markus Essler ◽  
...  
Keyword(s):  
Kinase Inhibitor ◽  
Shape Change ◽  
Rho Kinase ◽  
Adenosine Diphosphate ◽  
Receptor Activation ◽  
Human Platelets ◽  
Peptide Ligand ◽  
Thromboxane Receptor ◽  
Mlc Phosphorylation ◽  
Stimulation Of

Abstract Both Rho-kinase and the Ca2+/calmodulin-dependent myosin light chain (MLC) kinase increase the phosphorylation of MLC. We show that upon thrombin receptor stimulation by low-dose thrombin or the peptide ligand YFLLRNP, or upon thromboxane receptor activation by U46619, shape change and MLC phosphorylation in human platelets proceed through a pathway that does not involve an increase in cytosolic Ca2+. Under these conditions, Y-27632, a specific Rho-kinase inhibitor, prevented shape change and reduced the stimulation of MLC-phosphorylation. In contrast, Y-27632 barely affected shape change and MLC-phosphorylation by adenosine diphosphate (ADP), collagen-related peptide, and ionomycin that were associated with an increase in cytosolic Ca2+ and inhibited by BAPTA-AM/EGTA treatment. Furthermore, C3 exoenzyme, which inactivates Rho, inhibited preferentially the shape change induced by YFLLRNP compared with ADP and ionomycin. The results indicate that the Rho/Rho-kinase pathway is pivotal in mediating the MLC phosphorylation and platelet shape change by low concentrations of certain G protein–coupled platelet receptors, independent of an increase in cytosolic Ca2+. Our study defines 2 alternate pathways, Rho/Rho-kinase and Ca2+/calmodulin-regulated MLC-kinase, that lead independently of each other through stimulation of MLC-phosphorylation to the same physiological response in human platelets (ie, shape change).

scholarly journals Down-regulation of Rap1 activity is involved in ephrinB1-induced cell contraction

2005 ◽  
Vol 389 (2) ◽  
pp. 465-469 ◽  
Author(s):  
Jurgen A. Riedl ◽  
Dominique T. Brandt ◽  
Eduard Batlle ◽  
Leo S. Price ◽  
Hans Clevers ◽  
...  
Keyword(s):  
Tyrosine Kinases ◽  
Small Gtpases ◽  
Receptor Interaction ◽  
Down Regulation ◽  
Colon Cells ◽  
Eph Receptor ◽  
Colon Cell ◽  
Colon Cell Line ◽  
Cell Retraction ◽  
Stimulation Of

Ephrins are cell surface ligands that activate Eph receptor tyrosine kinases. This ligand–receptor interaction plays a central role in the sorting of cells. We have previously shown that the ephrinB–EphB signalling pathway is also involved in the migration of intestinal precursor cells along the crypts. Using the colon cell line DLD1 expressing the EphB2 receptor, we showed that stimulation of these cells with soluble ephrinB1 results in a rapid retraction of cell extensions and a detachment of cells. On ephrinB1 stimulation, the small GTPases Rho and Ras are activated and Rap1 is inactivated. Importantly, when a constitutively active Rap1 mutant was introduced into these cells, ephrinB1-induced retraction was inhibited. From these results, we conclude that down-regulation of Rap1 is a prerequisite for ephrin-induced cell retraction in colon cells.

scholarly journals Receptor-operated Ca2+ channels in gastric parietal cells: gastrin and carbachol induce Ca2+ influx in depleting intracellular Ca2+ stores

1993 ◽  
Vol 289 (1) ◽  
pp. 117-124 ◽  
Author(s):  
S Roche ◽  
J P Bali ◽  
R Magous
Keyword(s):  
Steady State ◽  
Receptor Activation ◽  
Parietal Cells ◽  
The Other ◽  
Bivalent Cation ◽  
Gtp Binding ◽  
Gastric Parietal Cells ◽  
Type Receptor ◽  
Ca2 Channels ◽  
Stimulation Of

The mechanism whereby gastrin-type receptor and muscarinic M3-type receptor regulate free intracellular Ca2+ concentration ([Ca2+]i) was studied in rabbit gastric parietal cells stimulated by either gastrin or carbachol. Both agonists induced a biphasic [Ca2+]i response: a transient [Ca2+]i rise, followed by a sustained steady state depending on extracellular Ca2+. Gastrin and carbachol also caused a rapid and transient increase in Mn2+ influx (a tracer for bivalent-cation entry). Pre-stimulation of cells with one agonist drastically decreased both [Ca2+]i increase and Mn2+ influx induced by the other. Neither diltiazem nor pertussistoxin treatment had any effect on agonist-stimulated Mn2+ entry. Thapsigargin, a Ca(2+)-pump inhibitor, induced a biphasic [Ca2+]i increase, and enhanced the rate of Mn2+ entry. Preincubation of cells with thapsigargin inhibits the [Ca2+]i increase as well as Mn2+ entry stimulated by gastrin or by carbachol. Thapsigargin induced a weak but significant increase in Ins(1,4,5)P3 content, but this agent had no effect on the agonist-evoked Ins(1,4,5)P3 response. In permeabilized parietal cells, Ins(1,4,5)P3 and caffeine caused an immediate Ca2+ release from intracellular pools, followed by a reloading of Ca2+ pools which can be prevented in the presence of thapsigargin. We conclude that (i) gastrin and carbachol mobilize common Ca2+ intracellular stores, (ii) Ca2+ permeability secondary to receptor activation involves neither a voltage-sensitive Ca2+ channel nor a GTP-binding protein from the G1 family, and (iii) agonists regulate common Ca2+ channels in depleting intracellular Ca2+ stores.

Enhanced Endothelial Cell Retraction Mediated by 12(S)-HETE: A Proposed Mechanism for the Role of Platelets in Tumor Cell Metastasis

1994 ◽  
Vol 210 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Kenneth V. Honn ◽  
Dean G. Tang ◽  
Irma M. Grossi ◽  
Colette Renaud ◽  
Zofia M. Duniec ◽  
...  
Keyword(s):  
Endothelial Cell ◽  
Tumor Cell ◽  
Cell Metastasis ◽  
Tumor Cell Metastasis ◽  
Endothelial Cell Retraction ◽  
Cell Retraction

Inhibition of TASK-1 potassium channel by phospholipase C

2001 ◽  
Vol 281 (2) ◽  
pp. C700-C708 ◽  
Author(s):  
Gábor Czirják ◽  
Gábor L. Petheő ◽  
András Spät ◽  
Péter Enyedi
Keyword(s):  
Phospholipase C ◽  
Lysophosphatidic Acid ◽  
Protein S ◽  
Receptor Activation ◽  
Xenopus Laevis Oocytes ◽  
Ang Ii ◽  
Inositol 1,4,5 Trisphosphate ◽  
Glomerulosa Cells ◽  
Pore Domain ◽  
Stimulation Of

The two-pore-domain K+ channel, TASK-1, was recently shown to be a target of receptor-mediated regulation in neurons and in adrenal glomerulosa cells. Here, we demonstrate that TASK-1 expressed in Xenopus laevis oocytes is inhibited by different Ca2+-mobilizing agonists. Lysophosphatidic acid, via its endogenous receptor, and ANG II and carbachol, via their heterologously expressed ANG II type 1a and M1 muscarinic receptors, respectively, inhibit TASK-1. This effect can be mimicked by guanosine 5′- O-(3-thiotriphosphate), indicating the involvement of GTP-binding protein(s). The phospholipase C inhibitor U-73122 reduced the receptor-mediated inhibition of TASK-1. Downstream signals of phospholipase C action (inositol 1,4,5-trisphosphate, cytoplasmic Ca2+ concentration, and diacylglycerol) do not mediate the inhibition. Unlike the Gq-coupled receptors, stimulation of the Gi-activating M2 muscarinic receptor coexpressed with TASK-1 results in an only minimal decrease of the TASK-1 current. However, additional coexpression of phospholipase C-β2 (which is responsive also to Giβγ-subunits) renders M2 receptor activation effective. This indicates the significance of phospholipase C activity in the receptor-mediated inhibition of TASK-1.

ANG II AT2 receptor modulates AT1receptor-mediated descending vasa recta endothelial Ca2+ signaling

2003 ◽  
Vol 284 (3) ◽  
pp. H779-H789 ◽  
Author(s):  
Kristie Rhinehart ◽  
Corey A. Handelsman ◽  
Erik P. Silldorff ◽  
Thomas L. Pallone
Keyword(s):  
Receptor Agonist ◽  
Calcium Concentration ◽  
Cyclopiazonic Acid ◽  
Receptor Activation ◽  
Receptor Subtype ◽  
Ang Ii ◽  
Receptor Stimulation ◽  
Vasa Recta ◽  
Stimulation Of

We tested whether the respective angiotensin type 1 (AT1) and 2 (AT2) receptor subtype antagonists losartan and PD-123319 could block the descending vasa recta (DVR) endothelial intracellular calcium concentration ([Ca2+]i) suppression induced by ANG II. ANG II partially reversed the increase in [Ca2+]igenerated by cyclopiazonic acid (CPA; 10−5 M), acetylcholine (ACh; 10−5 M), or bradykinin (BK; 10−7 M). Losartan (10−5 M) blocked that effect. When vessels were treated with ANG II before stimulation with BK and ACh, concomitant AT2 receptor blockade with PD-123319 (10−8 M) augmented the suppression of endothelial [Ca2+]i responses. Similarly, preactivation with the AT2 receptor agonist CGP-42112A (10−8 M) prevented AT1 receptor stimulation with ANG II + PD-123319 from suppressing endothelial [Ca2+]i. In contrast to endothelial [Ca2+]i suppression by ANG II, pericyte [Ca2+]i exhibited typical peak and plateau [Ca2+]i responses that were blocked by losartan but not PD-123319. DVR vasoconstriction by ANG II was augmented when AT2 receptors were blocked with PD-123319. Similarly, AT2 receptor stimulation with CGP-42112A delayed the onset of ANG II-induced constriction. PD-123319 alone (10−5 M) showed no AT1-like action to constrict microperfused DVR or increase pericyte [Ca2+]i. We conclude that ANG II suppression of endothelial [Ca2+]i and stimulation of pericyte [Ca2+]i is mediated by AT1 or AT1-like receptors. Furthermore, AT2 receptor activation opposes ANG II-induced endothelial [Ca2+]i suppression and abrogates ANG II-induced DVR vasoconstriction.

scholarly journals Stimulation of bone formation and prevention of bone loss by prostaglandin E EP4 receptor activation

2002 ◽  
Vol 99 (7) ◽  
pp. 4580-4585 ◽  
Author(s):  
K. Yoshida ◽  
H. Oida ◽  
T. Kobayashi ◽  
T. Maruyama ◽  
M. Tanaka ◽  
...  
Keyword(s):  
Bone Loss ◽  
Bone Formation ◽  
Receptor Activation ◽  
Prostaglandin E ◽  
Ep4 Receptor ◽  
Prevention Of Bone Loss ◽  
Stimulation Of

scholarly journals Activation of G protein-coupled bile acid receptor, TGR5, induces smooth muscle relaxation via both Epac- and PKA-mediated inhibition of RhoA/Rho kinase pathway

2013 ◽  
Vol 304 (5) ◽  
pp. G527-G535 ◽  
Author(s):  
Senthilkumar Rajagopal ◽  
Divya P. Kumar ◽  
Sunila Mahavadi ◽  
Sayak Bhattacharya ◽  
Ruizhe Zhou ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Kinase Activity ◽  
Muscle Relaxation ◽  
Rho Kinase ◽  
Muscle Cells ◽  
Receptor Activation ◽  
Gastric Smooth Muscle ◽  
Selective Ligand ◽  
Gastric Muscle ◽  
Kinase Pathway

The present study characterized the TGR5 expression and the signaling pathways coupled to this receptor that mediates the relaxation of gastric smooth muscle. TGR5 was detected in gastric muscle cells by RT-PCR and Western blotting. Treatment of cells with the TGR5-selective ligand oleanolic acid (OA) activated Gαs, but not Gαq, Gαi1, Gαi2, or Gαi3, and increased cAMP levels. OA did not elicit contraction, but caused relaxation of carbachol-induced contraction of gastric muscle cells from wild-type mice, but not tgr5−/− mice. OA, but not a selective exchange protein activated by cAMP (Epac) ligand (8-pCPT-2′-O-Me-cAMP), caused phosphorylation of RhoA and the phosphorylation was blocked by the PKA inhibitor, myristoylated PKI, and by the expression of phosphorylation-deficient mutant RhoA (S188A). Both OA and Epac ligand stimulated Ras-related protein 1 (Rap1) and inhibited carbachol (CCh)-induced Rho kinase activity. Expression of RhoA (S188A) or PKI partly reversed the inhibition of Rho kinase activity by OA but had no effect on inhibition by Epac ligand. However, suppression of Rap1 with siRNA blocked the inhibition of Rho kinase by Epac ligand, and partly reversed the inhibition by OA; the residual inhibition was blocked by PKI. Muscle relaxation in response to OA, but not Epac ligand, was partly reversed by PKI. We conclude that activation of TGR5 causes relaxation of gastric smooth muscle and the relaxation is mediated through inhibition of RhoA/Rho kinase pathway via both cAMP/Epac-dependent stimulation of Rap1 and cAMP/PKA-dependent phosphorylation of RhoA at Ser188. TGR5 receptor activation on smooth muscle reveals a novel mechanism for the regulation of gut motility by bile acids.

scholarly journals Importance and prospects for design of selective muscarinic agonists

2008 ◽  
pp. S39-S47
Author(s):  
J Jakubík ◽  
P Michal ◽  
E Machová ◽  
V Doležal
Keyword(s):  
Binding Sites ◽  
Natural Aging ◽  
Receptor Activation ◽  
Receptor Subtypes ◽  
Muscarinic Agonists ◽  
Amyloidogenic Processing ◽  
M1 Receptor ◽  
The Central Nervous System ◽  
M1 Agonist ◽  
Stimulation Of

There are five subtypes of muscarinic receptors that serve various important physiological functions in the central nervous system and the periphery. Mental functions like attention, learning, and memory are attributed to the muscarinic M1 subtype. These functions decline during natural aging and an early deficit is typical for Alzheimer s disease. In addition, stimulation of the M1 receptor increases non-amyloidogenic processing of the amyloid precursor protein and thus prevents accumulation of noxious beta-amyloid fragments. The selectivity of classical muscarinic agonists among receptor subtypes is very low due to the highly conserved nature of the orthosteric binding site among receptor subtypes. Herein we summarize some recent studies with the functionally-selective M1 agonist xanomeline that indicate complex pharmacological profile of this drug that includes interactions with and activation of receptor from both orthosteric and ectopic binding sites, and the time-dependent changes of ligand binding and receptor activation. These findings point to potential profitability of exploitation of ectopic ligands in the search for truly selective muscarinic receptor agonists.

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