scholarly journals Modulation of calcium fluxes in Jurkat T cells by myristic acid. Inhibition is independent of membrane potential and intracellular pH

1992 ◽  
Vol 283 (1) ◽  
pp. 113-118 ◽  
Author(s):  
T Nordström ◽  
T Mustelin ◽  
T Pessa-Morikawa ◽  
L C Andersson
Keyword(s):  
T Cells ◽  
Membrane Potential ◽  
T Cell ◽  
Cell Membrane ◽  
Intracellular Ph ◽  
Myristic Acid ◽  
Blocking Effect ◽  
Cell Membrane Potential ◽  
Jurkat Cells ◽  
Jurkat T Cells

Treatment of T lymphocytes with mitogenic antibodies against the T-cell receptor/CD3 complex induces within seconds a rise in the concentration of intracellular free Ca2+. We recently reported that free myristic acid, but not its methyl ester, inhibits both the anti-CD3-induced Ca2+ influx across the cell membrane and the Ca2+ release from intracellular stores in Jurkat T cells. Here we show that myristic acid induced a rapid hyperpolarization of the cell membrane potential and a decrease in intracellular pH in Jurkat cells. Lauric acid and palmitic acid caused minor hyperpolarization, whereas other saturated non-esterified fatty acids tested were without effect. Hyperpolarization of the membrane potential in Jurkat cells with valinomycin did not, however, inhibit the anti-CD3-induced Ca2+ signal, and the blocking effect on the Ca2+ signal in myristic acid-treated Jurkat cells was not reversed after normalization of the cell membrane potential by treatment with gramicidin. The inhibitory effect of myristic acid on the Ca2+ fluxes thus cannot be explained by changes in membrane potential. We also present evidence that the blocking effect of myristic acid on the receptor-operated Ca2+ flux is not due to the myristic acid-induced decrease in intracellular pH. Moreover, we demonstrate that myristic acid does not prevent the release of Ca2+ triggered by inositol 1,4,5-trisphosphate from intracellular pools in permeabilized cells. Our findings indicate that myristic acid blocks anti-CD3-induced Ca2+ traffic in Jurkat cells by interfering with the regulation of Ca2+ mobilization, apparently by blocking an early step in signal transduction from the T-cell-antigen receptor/CD3 complex.

scholarly journals Titanium Ions Promote Exogenous Calcium-Dependent Calcium Influx in Activated Jurkat T Cells: A Possible Mechanism to Explain Its Immunostimulatory Properties

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Jing Chen ◽  
Qiuying Li ◽  
Zhenhua Pang ◽  
Ming Gong ◽  
Li Tang
Keyword(s):  
T Cells ◽  
T Cell ◽  
Intracellular Calcium ◽  
T Cell Activation ◽  
Calcium Influx ◽  
Biological Activities ◽  
Jurkat Cells ◽  
Dependent Manner ◽  
Jurkat T Cells ◽  
Exogenous Calcium

Titanium and its alloys have been widely used in dental and orthopedic implants. Owing to the biotribocorrosion behavior of implants in simulated oral environment, Ti(IV) ions could be released into surrounding tissues. Current studies have found that Ti(IV) ions could affect the biological activities of immune cells in adjacent tissues and subsequently jeopardize the long-term performance of implant prostheses. However, the potential mechanism underlying its immunomodulatory properties remains unclear. Calcium signaling has been confirmed to be involved in regulation of lymphocyte immune function. Therefore, we hypothesize that Ti(IV) ions modulated T cell function through the change of intracellular calcium concentrations. This study is aimed at exploring the role of intracellular calcium responses in the modulatory effect of Ti(IV) ions on unactivated and phytohemagglutinin-activated Jurkat T cells. Here, we confirmed that Ti(IV) ions within a certain concentration range induced CD69 expression on both unactivated and activated T cells in our study. Additionally, the combined stimulation with Ti(IV) ions and PHA increased expression of IL-1β, TNF-α, and RANKL. Furthermore, we found that treatment with Ti(IV) induced a transitory increase in the levels of [Ca2+]i in activated Jurkat cells, dependent on the presence of exogenous calcium. Treatment with different doses of Ti(IV) for 24 h significantly increased the levels of [Ca2+]i in the activated Jurkat cells in a dose-dependent manner, but had little effect in the unactivated cells. Treatment with Ti(IV) did not significantly affect the PLCγ1 activation and inositol-1,4,5-trisphosphate (IP3) secretion in Jurkat cells. Taken together, these data indicated that Ti(IV) enhanced calcium influx during the T cell activation, independent of IP3-mediated intracellular calcium release. Our work provides insights into the mechanism involved in the regulation of lymphocyte behaviors under the effect of Ti(IV) ions, which may help to develop therapeutic strategies for dental implant failures.

scholarly journals ZAP-70-Independent Ca2+ Mobilization and Erk Activation in Jurkat T Cells in Response to T-Cell Antigen Receptor Ligation

2001 ◽  
Vol 21 (21) ◽  
pp. 7137-7149 ◽  
Author(s):  
Xiaochuan Shan ◽  
Richard Balakir ◽  
Gabriel Criado ◽  
Jason S. Wood ◽  
Maria-Cristina Seminario ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Tyrosine Phosphorylation ◽  
Antigen Receptor ◽  
Jurkat Cells ◽  
Jurkat T Cells ◽  
T Cell Antigen Receptor ◽  
Erk Activation ◽  
Cell Antigen Receptor ◽  
Cell Antigen

ABSTRACT The tyrosine kinase ZAP-70 has been implicated as a critical intermediary between T-cell antigen receptor (TCR) stimulation and Erk activation on the basis of the ability of dominant negative ZAP-70 to inhibit TCR-stimulated Erk activation, and the reported inability of anti-CD3 antibodies to activate Erk in ZAP-70-negative Jurkat cells. However, Erk is activated in T cells receiving a partial agonist signal, despite failing to activate ZAP-70. This discrepancy led us to reanalyze the ZAP-70-negative Jurkat T-cell line P116 for its ability to support Erk activation in response to TCR/CD3 stimulation. Erk was activated by CD3 cross-linking in P116 cells. However, this response required a higher concentration of anti-CD3 antibody and was delayed and transient compared to that in Jurkat T cells. Activation of Raf-1 and MEK-1 was coincident with Erk activation. Remarkably, the time course of Ras activation was comparable in the two cell lines, despite proceeding in the absence of LAT tyrosine phosphorylation in the P116 cells. CD3 stimulation of P116 cells also induced tyrosine phosphorylation of phospholipase C-γ1 (PLCγ1) and increased the intracellular Ca2+ concentration. Protein kinase C (PKC) inhibitors blocked CD3-stimulated Erk activation in P116 cells, while parental Jurkat cells were refractory to PKC inhibition. The physiologic relevance of these signaling events is further supported by the finding of PLCγ1 tyrosine phosphorylation, Erk activation, and CD69 upregulation in P116 cells on stimulation with superantigen and antigen-presenting cells. These results demonstrate the existence of two pathways leading to TCR-stimulated Erk activation in Jurkat T cells: a ZAP-70-independent pathway requiring PKC and a ZAP-70-dependent pathway that is PKC independent.

scholarly journals Intracellular pH regulation in freshly isolated suspensions of rabbit inner medullary collecting duct cells: role of Na+:H+ antiporter and H(+)-ATPase.

1990 ◽  
Vol 1 (6) ◽  
pp. 890-901
Author(s):  
D Kikeri ◽  
M L Zeidel
Keyword(s):  
Membrane Potential ◽  
Cell Membrane ◽  
Intracellular Ph ◽  
Recovery Rate ◽  
Collecting Duct ◽  
Atp Depletion ◽  
Cell Membrane Potential ◽  
Inner Medullary Collecting Duct ◽  
Medullary Collecting Duct ◽  
In Cells

To define proton transport mechanisms involved in the regulation of intracellular pH (pHi) in cells of the inner medullary collecting duct (IMCD), pHi and cell membrane potential were estimated by using the fluorescent dyes 2,7-biscarboxyethyl-5(6)-carboxyfluorescein and 3,3'-dipropylthiadicarbocyanine iodide, respectively, in suspensions of freshly isolated rabbit IMCD cells. The resting pHi of IMCD cells in nonbicarbonate Ringer's solution (pH 7.4) was 7.21 +/- 0.03 (mean +/- SE). When cells were acidified by ammonium withdrawal, the initial pHi recovery rate was 0.33 +/- 0.02 pH unit/min; replacement of extracellular Na+ (130 mM) with N-methyl-D-glucamine+ reduced the pHi recovery rate to 0.08 +/- 0.02 pH unit/min, while addition of 0.1 mM amiloride in the presence of extracellular Na+ reduced the rate of pHi recovery to 0.02 +/- 0.02 pH unit/min. Similar results were obtained in cells acid loaded with HCl. Cells recovering from acidification exhibited 22Na+ uptake rates threefold higher than did nonacidified cells. The rate of Na(+)-dependent pHi recovery was independent of the cell membrane potential. In the absence of extracellular Na+, depolarizing cell membrane potential in a stepwise manner by increasing extracellular K+ concentrations from 1 to 130 mM resulted in graded increments in the rate of pHi recovery. In the presence of 130 mM K+, the pHi recovery rate in acidified cells was dependent on cellular ATP levels, sensitive to 1 mM N-ethylmaleimide, and insensitive to 0.01 mM oligomycin in the presence of glucose (control, 0.24 +/- 0.01; ATP-depleted, 0.13 +/- 0.02; addition of N-ethylmaleimide, 0.16 +/- 0.01; addition of oligomycin, 0.27 +/- 0.02 pH unit/min). ATP depletion markedly inhibited H+ extrusion from IMCD cells measured by using a pH stat. These results provide direct evidence in freshly isolated IMCD cells that both a Na+:H+ antiporter and a rheogenic H(+)-ATPase participate in pHi regulation.

RIAM Regulates Actin Reorganization at the Immunological Synapse and Calcium Mobilization during T Cell Activation.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1722-1722
Author(s):  
Esther M. Lafuente ◽  
Mathew Salanga ◽  
Yoshiko Iwamoto ◽  
Lequn Li ◽  
Vassiliki A. Boussiotis
Keyword(s):  
T Cells ◽  
T Cell ◽  
B Cells ◽  
T Cell Activation ◽  
Cell Activation ◽  
Immunological Synapse ◽  
Jurkat Cells ◽  
Jurkat T Cells ◽  
Actin Reorganization ◽  
Cytoskeletal Dynamics

Abstract Engagement of immune recognition subunits on lymphocytes results in cytoskeletal reorganization, polarization of polymerized actin, conjugate formation between T cells and APC, stabilization of the immunological synapse (IS), and initiation of signaling cascades leading to T cell activation. Actin remodeling is essential for these events and is mandatory for T cell activation. We have identified RIAM, a novel adaptor molecule that interacts specifically with active GTP-bound Rap1 and with regulators of the actin cytoskeleton Evl, VASP and Profilin. Profilin associates with G-actin and promotes actin polymerization by adding actin monomers to the barbed ends of F-actin. Ena/VASP family proteins are cytoskeletal proteins and regulate actin dynamics. Via these interactions, RIAM functions as a regulator of the actin cytoskeleton. RIAM also has a mandatory role in regulating activation of integrins downstream of Rap1. The ability of a T cell to recognize and conjugate with an APC is dependent on cytoskeletal dynamics and “inside out” signaling leading to integrin-mediated adhesion. Activation of the b2 integrin LFA-1 leads to high avidity binding to ICAM proteins, which is crucial for stable T cell-APC conjugation. Because RIAM is involved both in cytoskeletal dynamics and integrin activation, we examined whether RIAM had a role in this process. Stable GFP-transfected Jurkat T cells were incubated with Raji B cells as APC, in the presence or absence of SEE. T cell:APC conjugates and formation of IS were examined by confocal microscopy. Synapse formation between GFP-Jurkat cells and Raji B cells was detected only in the presence of SEE. Under these conditions, polymerized (F) actin was highly recruited at the IS, as determined by phalloidin staining. Staining with RIAM-specific antibody indicated that in the absence of antigen, RIAM was diffusely expressed in the cytoplasm and at the plasma membrane. Impressively, upon incubation with SEE loaded Raji cells, RIAM was redistributed at the IS where it co-localized with polymerized (F) actin and ZAP-70. Knockdown of RIAM in Jurkat T cells resulted in significant defects in conjugate formation with SEE loaded B cells. Thus RIAM is involved in actin reorganization in the IS and in the formation of T cell:APC conjugates. Because appropriate actin reorganization is required for T cell activation we next explored whether RIAM knockdown leads to defects in TCR-mediated signaling events. RIAM-knockdown Jurkat T cells displayed significantly impaired IL-2 production in response to SEE loaded Raji and in decreased IL-2 promoter driven transcriptional activity. Surprisingly, despite the significant decrease in IL-2 transcription, RIAM-knockdown Jurkat cells did not show altered TCR-induced phosphorylation of PLCg1, or activation of MAP kinases including MEK, Erk1/2 and JNK, compared to control cells. Moreover, AP-1 and NF-kB-mediated gene transcription induced by CD3-plus-CD28 was unaffected. In contrast, NFAT-driven transcription was significantly impaired. Assessment of intracellular calcium by flow cytometry indicated that RIAM-knockdown cells had significantly reduced TCR-mediated intracellular calcium signal. These results indicate that RIAM is an important component of a signaling pathway that regulates calcium mobilization and NFAT mediated gene transcription in T lymphocytes.

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