Extracellular ATP Induces Phosphatidylserine Externalization Earlier than Nuclear Apoptotic Events in Thymocytes

Courageot, Marie‐Pierre; Lépine, Sandrine; Giraud, Françoise; Sulpice, Jean‐Claude

doi:10.1111/j.1749-6632.2002.tb04630.x

Cited by 6 publications

(3 citation statements)

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“…In the present study, we found that ATPe triggers PS externalization in plasma membrane of thymocytes from BALB/c mice within 15 min. BzATP also triggers a rapid PS flip in HEK 293 cells expressing the P2X7R, in THP-1 monocytes (46) and in mouse thymocytes (47). However, because translocation of PS induced by P2X7R can be dissociated from apoptosis (46), we analyzed the effect of ATPe on DNA fragmentation, a late event in the apoptotic process.…”

Section: Discussionmentioning

confidence: 99%

The Pro-451 to Leu Polymorphism within the C-terminal Tail of P2X7 Receptor Impairs Cell Death but Not Phospholipase D Activation in Murine Thymocytes

Stunff

Auger

Kanellopoulos

et al. 2004

Journal of Biological Chemistry

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The P2X family of ATP receptors (P2XR) are ligandgated channels that have been proposed to regulate cell death of immature thymocytes. However, the nature of the P2XR subtype involved has been controversial until recently. In agreement with previous studies, we found that extracellular ATP (ATPe) induces a caspasedependent apoptosis of BALB/c thymocytes, as observed by DNA fragmentation. Additionally, ATPe induces a predominant caspase-independent thymocytes lysis characterized by plasma membrane disruption. Both responses to ATPe can be induced by a potent P2X7R agonist, benzoylbenzoyl-ATP, whereas P2X7R antagonists, oxidized ATP and pyridoxalphosphate-6-azophenyl-2,4-disulfonic acid, inhibited the effect of ATPe. These results are further supported by observations where disruption of the P2X7R gene (P2X7R ؊/؊ mice) completely abolishes thymocytes death induced by ATPe. Interestingly, the natural P451L mutation in the C-terminal tail of P2X7R present in C57BL/6 mice, which impairs ATPe-dependent pore formation in T lymphocytes, significantly reduces thymocytes death triggered by ATPe. Furthermore, we found that P2X7R from BW5147 thymoma cells also harbors this point mutation, accounting for their insensitivity to ATPe-induced cell death. Concentrations of ATPe effective in inducing cell death also increase phosphatidylcholine-hydrolyzing phospholipase D (PC-PLD) activity in BALB/c thymocytes through the stimulation of P2X7R. However, in contrast to ATPe-induced cell death, PC-PLD activation is totally Ca 2؉ -dependent. Moreover, the stimulation of PC-PLD by ATPe is not affected by the P451L mutation present in C57BL/6 thymocytes and BW5147 cells, suggesting that cell death and PC-PLD activity are regulated through distinct domains of the P2X7R. Finally, the inhibition of ATPe-induced PC-PLD stimulation does not affect thymocytes death. Altogether, these data suggest that P2X7R-induced thymocytes death is independent of the stimulation of PC-PLD activity.

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Section: Discussionmentioning

confidence: 99%

The Pro-451 to Leu Polymorphism within the C-terminal Tail of P2X7 Receptor Impairs Cell Death but Not Phospholipase D Activation in Murine Thymocytes

Stunff

Auger

Kanellopoulos

et al. 2004

Journal of Biological Chemistry

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“…At physiological external concentrations, Na ϩ was more potent than Ca 2ϩ to induce PS exposure. Portions of this work have appeared in a preliminary report (31).…”

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confidence: 99%

Involvement of Sodium in Early Phosphatidylserine Exposure and Phospholipid Scrambling Induced by P2X7 Purinoceptor Activation in Thymocytes

Courageot

Lépine

Hours

et al. 2004

Journal of Biological Chemistry

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Extracellular ATP (ATP ec ), a possible effector in thymocyte selection, induces thymocyte death via purinoceptor activation. We show that ATP ec induced cell death by apoptosis, rather than lysis, and early phosphatidylserine (PS) exposure and phospholipid scrambling in a limited thymocyte population (35-40%). PS externalization resulted from the activation of the cationic channel P2X7 (formerly P2Z) receptor and was triggered in all thymocyte subsets although to different proportions in each one. Phospholipid movement was dependent on ATP ec -induced Ca 2؉ and/or Na ؉ influx. At physiological external Na ؉ concentration, without external Ca 2؉ , PS was exposed in all ATP ec -responsive cells. In contrast, without external Na ؉ , physiological external Ca 2؉ concentration promoted a submaximal response. Altogether these data show that Na ؉ influx plays a major role in the rapid PS exposure induced by P2X7 receptor activation in thymocytes. Extracellular ATP (ATP ec )1 induces thymocyte apoptosis and may play a role in thymocyte maturation (1-4). A major change of cell membrane during apoptosis, slightly preceding nuclear condensation (5), is the exposure on the exoplasmic cell surface of phosphatidylserine (PS) (6 -9), a phospholipid normally maintained on the inner membrane leaflet by the aminophospholipid translocase (APLT) (10). This process is associated with a general loss of the asymmetric distribution (scrambling) of all the other major phospholipids (6,7,9). The presence of specific PS receptors on macrophages potentially allows a rapid elimination of apoptotic cells by phagocytosis before their lysis (11). Rapid PS exposure and scrambling are generally observed after platelet activation or treatment of cells with a Ca 2ϩ ionophore, both conditions promoting a drastic and rapid rise in cytosolic Ca 2ϩ concentration ([Ca 2ϩ ] i ) (7). An involvement of Ca 2ϩ has been also reported in PS exposure during apoptosis (6,7,12). Ca 2ϩ acts by inhibiting APLT and by targeting scramblase (6, 7, 13) or other molecular complexes, which could contain phosphoinositides (14,15). Recent studies show that the rapid Ca 2ϩ -induced PS exposure is correlated with scramblase expression (16), in contrast to the delayed PS exposure associated with apoptosis (17, 18), in agreement with the involvement of other phospholipid transporters in apoptotic pathways.ATP ec is able to evoke physiological responses in a wide variety of cells and tissues. ATP is concentrated in cell cytosol and in exocytic vesicles, reaching 2-4 and 100 mM, respectively (19), and can be merely released from damaged cells, transported through carriers or channels, or secreted (19 -21). In the extracellular medium, its lifetime is very short due to its rapid degradation by ectonucleotidases and ecto-ATPases (19). ATP ec binds to distinct types of purinergic receptors classified into two subfamilies: metabotropic P2Y receptors coupled to Gprotein (P2Y1-6 and P2Y11) and ligand-gated ion channel P2X receptors (P2X1-7) (22). P2X7 receptor, previously designat...

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“…6 A third category, P2Z, which caused ATP-dependent cell lysis by the formation of membrane pores permeable to large molecules, was found to have P2X function as well and has been reclassified as P2X7. 7 Since Burnstock's discovery of ATP receptors in the nervous system, the subtypes of the P2X and P2Y receptor families have been found in diverse cell types throughout the body, including the cardiovascular, [8][9][10][11][12] respiratory, [13][14][15][16] gastrointestinal, 17-20 urogenital, 21-27 musculoskeletal, 28-32 and endocrine 33-37 systems, and play particularly prominent roles in the development 38 and function 39 of the immune system. Extracellular ATP has been implicated in some stage of progression of pathologic processes ranging from atherosclerosis 40,41 to stroke 42 to arthritis 43 to gastric ulcers.…”

Section: Sommairementioning

confidence: 99%

Role of Extracellular Adenosine Triphosphate in Human Skin

Holzer

Granstein

2004

JCMS

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Extracellular ATP Induces Phosphatidylserine Externalization Earlier than Nuclear Apoptotic Events in Thymocytes

Abstract: The present study shows for the first time that ATP(ec) induces a very early PS exposure in thymocytes and that this process can be induced in the absence of Ca(2+) influx and caspase activation.

Cited by 6 publications

References 6 publications

The Pro-451 to Leu Polymorphism within the C-terminal Tail of P2X7 Receptor Impairs Cell Death but Not Phospholipase D Activation in Murine Thymocytes

The Pro-451 to Leu Polymorphism within the C-terminal Tail of P2X7 Receptor Impairs Cell Death but Not Phospholipase D Activation in Murine Thymocytes

Involvement of Sodium in Early Phosphatidylserine Exposure and Phospholipid Scrambling Induced by P2X7 Purinoceptor Activation in Thymocytes

Role of Extracellular Adenosine Triphosphate in Human Skin

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