Urea signaling to ERK phosphorylation in renal medullary cells requires extracellular calcium but not calcium entry

2001 ◽  
Vol 280 (1) ◽  
pp. F162-F171 ◽  
Author(s):  
Xiao-Yan Yang ◽  
Hongyu Zhao ◽  
Zheng Zhang ◽  
Karin D. Rodland ◽  
Jean-Baptiste Roullet ◽  
...  
Keyword(s):  
Intracellular Calcium ◽  
Calcium Release ◽  
Calcium Entry ◽  
Extracellular Calcium ◽  
Urea Treatment ◽  
Erk Activation ◽  
Calcium Dependent ◽  
Erk Phosphorylation ◽  
Extracellular Signal ◽  
A Cell

The renal cell line mIMCD3 exhibits markedly upregulated phosphorylation of the extracellular signal-regulated kinase (ERK) 1 and 2 in response to urea treatment (200 mM for 5 min). Previous data have suggested the involvement of a classical protein kinase C (cPKC)-dependent pathway in downstream events related to urea signaling. We now show that urea-inducible ERK activation requires extracellular calcium; unexpectedly, it occurs independently of activation of cPKC isoforms. Pharmacological inhibitors of known intracellular calcium release pathways and extracellular calcium entry pathways fail to inhibit ERK activation by urea. Fura 2 ratiometry was used to assess the effect of urea treatment on intracellular calcium mobilization. In single-cell analyses using subconfluent monolayers and in population-wide analyses using both confluent monolayers and cells in suspension, urea failed to increase intracellular calcium concentration. Taken together, these data indicate that urea-inducible ERK activation requires calcium action but not calcium entry. Although direct evidence is lacking, one possible explanation could include involvement of a calcium-dependent extracellular moiety of a cell surface-associated protein.

Mechanism of Activation and Role of Extracellular Signal Regulated Kinase in ADP-Induced Thromboxane A2 Generation in Platelets.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 3567-3567
Author(s):  
Analia Garcia ◽  
Haripriya Shankar ◽  
Satya P. Kunapuli
Keyword(s):  
Thromboxane A2 ◽  
P2y Receptors ◽  
Extracellular Calcium ◽  
Negative Regulation ◽  
Erk Activation ◽  
Erk Phosphorylation ◽  
Extracellular Signal ◽  
Upstream Kinase ◽  
Erk2 Activation ◽  
Induced Aggregation

Abstract We have previously shown that ADP-induced thromboxane A2 generation in platelets requires co-ordinated signaling events from the Gq-coupled P2Y1 receptor and the Gi-coupled P2Y12 receptor in addition to outside-in signaling. It is also known that ADP-induced thromboxane A2 generation is completely abolished in the presence of extracellular calcium, but the mechanism of this negative regulation is not known. In this study we sought to identify the important signaling molecules in ADP-induced thromboxane A2 generation in platelets and characterize the regulation of these molecules by extracellular calcium. Erk2 activation occurred when outside-in signaling was blocked, indicating that it is a downstream event from the P2Y receptors. However, blockade of either P2Y1 or the P2Y12 receptors with corresponding antagonists completely abolished Erk phosphorylation, indicating that both P2Y receptors are required for ADP-induced Erk activation. However, blockade of Erk upstream kinase MEK had not effect on ADP-induced aggregation in aspirin-treated platelets, but dramatically inhibited aggregation as well as secretion in non-aspirinated platelets, suggesting that Erk might be important for thromboxane A2 generation. Finally, PP1 and PP2, inhibitors of Src family kinases, but not PP3, an inactive analog, abolished ADP-induced Erk phosphorylation and thromboxane A2 generation. Interestingly, ADP-induced Erk phosphorylation was completely inhibited in the presence of extracellular calcium, indicating that Erk is a key signaling molecule regulated by extracellular calcium in the negative regulation of thromboxane A2 generation. We conclude that Erk2 is activated downstream of P2Y receptors through a complex mechanism involving Src kinases and plays an important role in ADP-induced thromboxane A2 generation. We also conclude that extracellular calcium blocks ADP-induced thromboxane A2 generation through the inhibition of Erk activation.

scholarly journals Measurement of shear stress-mediated intracellular calcium dynamics in human dermal lymphatic endothelial cells

2015 ◽  
Vol 308 (7) ◽  
pp. H697-H706 ◽  
Author(s):  
M. Jafarnejad ◽  
W. E. Cromer ◽  
R. R. Kaunas ◽  
S. L. Zhang ◽  
D. C. Zawieja ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Shear Stress ◽  
Intracellular Calcium ◽  
Calcium Release ◽  
Calcium Entry ◽  
Extracellular Calcium ◽  
Calcium Signal ◽  
Lymphatic Endothelial Cells ◽  
Crac Channels ◽  
Custom Made

The shear stress applied to lymphatic endothelial cells (LEC) by lymph flow changes dramatically under normal conditions as well as in response to disease conditions and immune reactions. In general, LEC are known to regulate the contraction frequency and strength of lymphatic pumping in response to shear stress. Intracellular calcium concentration ([Ca2+]i) is an important factor that regulates lymphatic contraction characteristics. In this study, we measured changes in the [Ca2+]i under different shear stress levels and determined the source of this calcium signal. Briefly, human dermal LEC were cultured in custom-made microchannels for 3 days before loading with 2 µM fura-2 AM, a ratiometric calcium dye to measure [Ca2+]i. Step changes in shear stress resulted in a rapid increase in [Ca2+]i followed by a gradual return to the basal level and sometimes below the initial baseline (45.2 ± 2.2 nM). The [Ca2+]i reached a peak at 126.2 ± 5.6 nM for 10 dyn/cm2 stimulus, whereas the peak was only 71.8 ± 5.4 nM for 1 dyn/cm2 stimulus, indicating that the calcium signal depends on the magnitude of shear stress. Removal of the extracellular calcium from the buffer or pharmocological blockade of calcium release-activated calcium (CRAC) channels significantly reduced the peak [Ca2+]i, demonstrating a role of extracellular calcium entry. Inhibition of endoplasmic reticulum (ER) calcium pumps showed the importance of intracellular calcium stores in the initiation of this signal. In conclusion, we demonstrated that the shear-mediated calcium signal is dependent on the magnitude of the shear and involves ER store calcium release and extracellular calcium entry.

scholarly journals Copper-induced activation of TRPs and VDCCs triggers a calcium signature response regulating gene expression in Ectocarpus siliculosus

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e4556 ◽  
Author(s):  
Alberto González ◽  
Claudio A. Sáez ◽  
Alejandra Moenne
Keyword(s):  
Calcium Channels ◽  
Intracellular Calcium ◽  
Protein Kinases ◽  
Calcium Release ◽  
Trp Channels ◽  
Calcium Entry ◽  
Extracellular Calcium ◽  
Green Macroalgae ◽  
Ectocarpus Siliculosus ◽  
Intracellular Calcium Release

In certain multicellular photoautotrophs, such as plants and green macroalgae, it has been demonstrated that calcium signaling importantly mediates tolerance to copper excess. However, there is no information in brown macroalgae, which are phylogenetically distant from green algae and plants. We have previously shown that chronic copper levels (2.5 μM) activate transient receptor potential (TRP) channels in the model brown macroalga Ectocarpus siliculosus, allowing extracellular calcium entry at 13, 29, 39 and 51 min. Here, we showed that intracellular calcium increases also occurred at 3 and 5 h of exposure; these increases were inhibited by antagonists of voltage-dependent calcium channels (VDCCs); a chelating agent of extracellular calcium; an antagonist of endoplasmic reticulum (ER) ATPase; and antagonists of cADPR-, NAADP- and IP3-dependent calcium channels. Thus, copper activates VDCCs allowing extracellular calcium entry and intracellular calcium release from the ER via cADPR-, IP3- and NAADP-dependent channels. Furthermore, the level of transcripts encoding a phytochelatin synthase (PS) and a metallothionein (MT) were analyzed in the alga exposed to 2.5 μM copper from 3 to 24 h. The level of ps and mt transcripts increased until 24 h and these increases were inhibited by antagonists of calmodulins (CaMs), calcineurin B-like proteins (CBLs) and calcium-dependent protein kinases (CDPKs). Finally, activation of VDCC was inhibited by a mixture of TRP antagonists and by inhibitors of protein kinases. Thus, copper-mediated activation of TRPs triggers VDCCs via protein kinases, allowing extracellular calcium entry and intracellular calcium release from ER that, in turn, activate CaMs, CBLs and CDPKs increasing expression of PS and MT encoding genes in E. siliculosus.

A SIMPLE MODEL FOR INTERACTION OF VOLTAGE AND CALCIUM DYNAMICS IN VIRTUAL VENTRICULAR TISSUE

2003 ◽  
Vol 13 (12) ◽  
pp. 3873-3886
Author(s):  
O. V. ASLANIDI ◽  
A. V. HOLDEN
Keyword(s):  
Intracellular Calcium ◽  
Calcium Release ◽  
Cell Model ◽  
Excitation Threshold ◽  
Calcium Dynamics ◽  
Variable Model ◽  
Ventricular Cell ◽  
Calcium Dependent ◽  
Intracellular Ca ◽  
A Site

A simple two-variable model is used to replace the formulation of calcium dynamics in the Luo–Rudy ventricular cell model. Virtual ventricular cell and tissue are developed and validated to reproduce restitution properties and calcium-dependent voltage patterns present in the original model. Basic interactions between the membrane potential and Ca 2+ dynamics in the virtual cell and a strand of the virtual tissue are studied. Intracellular calcium waves can be linked to both action potentials (APs) and delayed afterdepolarizations (DADs). An intracellular calcium wave propagating from the cell interior can induce an AP upon reaching the cell membrane. The voltage and the intracellular Ca 2+ patterns within the same cell can be highly desynchronized. In a one-dimensional strand of the virtual tissue calcium motion is driven by the AP propagation. However, calcium release can be induced upon certain conditions (e.g. Na + overload of the cells), which results in DADs propagating in the wake of AP. Such propagating DADs can reach the excitation threshold, generating a pair of extrasystolic APs. Collision of a propagating AP with a site of elevated intracellular Ca 2+ concentration does not affect the propagation under the normal conditions. Under Na + overload local elevation of the intracellular Ca 2+ leads to generation of an extrasystolic AP, which destroys the original propagating AP.

scholarly journals Oxytocin antagonism prevents pregnancy-associated aortic dissection in a mouse model of Marfan syndrome

2019 ◽  
Vol 11 (490) ◽  
pp. eaat4822 ◽  
Author(s):  
Jennifer Pardo Habashi ◽  
Elena Gallo MacFarlane ◽  
Rustam Bagirzadeh ◽  
Caitlin Bowen ◽  
Nicholas Huso ◽  
...  
Keyword(s):  
Aortic Dissection ◽  
Mouse Model ◽  
Marfan Syndrome ◽  
Uterine Contraction ◽  
Aortic Wall ◽  
Erk Activation ◽  
Extracellular Signal Regulated Kinase ◽  
Erk Phosphorylation ◽  
Extracellular Signal ◽  
Erk Kinase

Women with Marfan syndrome (MFS) are at high risk for pregnancy-associated aortic dissection. Pathogenic models that singularly invoke hemodynamic stress are difficult to reconcile with predominant postnatal occurrence of aortic tear, often occurring weeks to months after delivery. In consideration of events that peak at term, are sustained after delivery, and might synergize with previously defined signaling pathways implicated in aneurysm progression, we examined the hormone oxytocin, which initiates uterine contraction and milk letdown for the duration of lactation through phosphorylation of extracellular signal–regulated kinase (ERK). In a mouse model of MFS that shows highly penetrant postnatal aortic dissection, risk was strongly attenuated by preventing lactation or use of an oxytocin receptor antagonist. Survival correlated inversely with the extent of ERK activation in the aortic wall, and strong protection was observed upon attenuation of ERK phosphorylation using an inhibitor of ERK kinase (MEK) or the U.S. Food and Drug Administration–approved medication hydralazine, offering potential therapeutic strategies for pregnancy-associated vascular catastrophe in the setting of MFS.

Regulation of MEK/ERK pathway output by subcellular localization of B-Raf

2012 ◽  
Vol 40 (1) ◽  
pp. 67-72 ◽  
Author(s):  
Catherine Andreadi ◽  
Catherine Noble ◽  
Bipin Patel ◽  
Hong Jin ◽  
Maria M. Aguilar Hernandez ◽  
...  
Keyword(s):  
Growth Factor ◽  
Subcellular Localization ◽  
Signalling Pathway ◽  
Erk Activation ◽  
Extracellular Signal Regulated Kinase ◽  
Intracellular Signalling Pathway ◽  
Pathway Activation ◽  
Extracellular Signal ◽  
A Cell ◽  
Phase Entry

The strength and duration of intracellular signalling pathway activation is a key determinant of the biological outcome of cells in response to extracellular cues. This has been particularly elucidated for the Ras/Raf/MEK [mitogen-activated growth factor/ERK (extracellular-signal-regulated kinase) kinase]/ERK signalling pathway with a number of studies in fibroblasts showing that sustained ERK signalling is a requirement for S-phase entry, whereas transient ERK signalling does not have this capability. A major unanswered question, however, is how a cell can sustain ERK activation, particularly when ERK-specific phosphatases are transcriptionally up-regulated by the pathway itself. A major point of ERK regulation is at the level of Raf, and, to sustain ERK activation in the presence of ERK phosphatases, sustained Raf activation is a requirement. Three Raf proteins exist in mammals, and the activity of all three is induced following growth factor stimulation of cells, but only B-Raf activity is maintained at later time points. This observation points to B-Raf as a regulator of sustained ERK activation. In the present review, we consider evidence for a link between B-Raf and sustained ERK activation, focusing on a potential role for the subcellular localization of B-Raf in this key physiological event.

Spontaneous oscillations in cytoplasmic calcium concentration in vascular smooth muscle

1989 ◽  
Vol 256 (5) ◽  
pp. C951-C957 ◽  
Author(s):  
P. L. Weissberg ◽  
P. J. Little ◽  
A. Bobik
Keyword(s):  
Smooth Muscle ◽  
Sarcoplasmic Reticulum ◽  
Calcium Channel ◽  
Intracellular Calcium ◽  
Calcium Concentration ◽  
Calcium Release ◽  
Extracellular Calcium ◽  
Fluorescence Measurement ◽  
Cytoplasmic Calcium ◽  
Spontaneous Oscillations

Fluorescence measurement of fura-2 and quin2 signals from confluent primary cultures of serum-deprived rat aortic smooth muscle cells have revealed spontaneous oscillations in intracellular calcium concentration ([Ca2+]i). The transients consist of a rapid increase in [Ca2+]i that averages 60 nM and lasts approximately 30 s. They are caused by intracellular calcium release and an influx of extracellular calcium. Exposure of cells to the calcium-channel antagonists verapamil and diltiazem or incubation in nominally calcium-free medium reduced both the duration and amplitude of the transients; in contrast, the calcium-channel agonist (-)BAY K 8644 increased their duration. The transients were abolished by caffeine and 8-(N,N-diethylamino)octyl 3,4,5-trimethoxybenzoate, agents that interfere with calcium release from the sarcoplasmic reticulum. These findings demonstrate that the sarcoplasmic reticulum is a primary source for the spontaneous oscillations in cytoplasmic calcium and is closely associated with the influx of extracellular calcium. Although the function of these transients is unclear, they may be involved in the spontaneous contractions observed in some vessels and in the regulation of vascular resistance.

Sign in / Sign up

Export Citation Format

Share Document