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Annexin V counteracts apoptosis while inducing Ca(2+) influx in human lymphocytic T cells
C Gidon-Jeangirard1, E Solito, A Hofmann
1Institut d'Hématologie et d'Immunologie, Faculté de Médecine, Université Louis Pasteur, Strasbourg, 67085, France.
Abstract:
We have previously shown that when annexin V is present during the execution of a cell death program, apoptosis is delayed. This is reflected by the inhibition of DNA cleavage and of the release of apoptotic membrane particles, and by reduction of the proteolytic processing of caspase-3. Here, we have studied the mechanism(s) through which annexin V counteracts apoptosis in the human CEM T cell line. The degree of apoptosis inhibition was associated with an increase of intracellular Ca(2+) concentration ([Ca(2+)](i)). Reduction of the extracellular Ca(2+) concentration by EGTA abolished the anti-apoptotic effect, suggesting that annexin V favors Ca(2+) influx and that Ca(2+) acts as an inhibitor rather than an activator of apoptosis in CEM T cells. The effects on apoptosis and [Ca(2+)](i) of several modified annexins with different electrophysiological properties indicate that the N-terminal domain of annexin V is necessary for the Ca(2+)-dependent anti-apoptotic action of annexin V. These results suggest that annexin V regulates membrane Ca(2+) permeability and is protective against apoptosis by increasing [Ca(2+)](i) in CEM T cells.
Insights
Annexin V delays apoptosis by increasing intracellular calcium (Ca2+) in T cells. This mechanism involves regulating membrane permeability and requires the N-terminal domain of annexin V for its protective effect.
Area of Science:
- Cell Biology
- Immunology
- Biochemistry
Background:
- Annexin V has been previously shown to delay apoptosis.
- Apoptosis involves DNA cleavage, release of membrane particles, and caspase-3 processing.
Purpose of the Study:
- To investigate the mechanism by which annexin V counteracts apoptosis in human CEM T cells.
- To determine the role of intracellular calcium (Ca2+) in annexin V-mediated apoptosis inhibition.
Main Methods:
- Measuring intracellular Ca2+ concentration ([Ca2+]i) in CEM T cells treated with annexin V.
- Utilizing EGTA to reduce extracellular Ca2+ concentration.
- Employing modified annexins with altered electrophysiological properties.
Main Results:
- Annexin V's anti-apoptotic effect correlated with increased [Ca2+]i.
- Reduced extracellular Ca2+ abolished annexin V's protective effect.
- The N-terminal domain of annexin V was essential for its Ca2+-dependent anti-apoptotic action.
Conclusions:
- Annexin V promotes Ca2+ influx, leading to increased [Ca2+]i.
- Calcium acts as an inhibitor of apoptosis in CEM T cells.
- Annexin V protects against apoptosis by modulating membrane Ca2+ permeability and elevating [Ca2+]i.