Extracellular ATP causes lysis of mouse thymocytes and activates a plasma membrane ion channel

Abstract

Extracellular ATP (ATP.) caused a concentration-dependent lysis of mouse thymocytes. Lysis, as judged by release of the cytosolic enzyme lactate dehydrogenase, was preceded by depolarization of the plasma membrane and by Ca2+ influx.Both Na+ uptake (which sustained plasma membrane depolarization) and Ca2+ influx showed (1) the same dependence on the ATPo concentration; (2) the same nucleotide specificity; and (3) the same Hill coefficient. However, whereas the rise in the cytosolic free Ca2+ concentration ([Ca2+]1) was fully inhibited by the known Ca2+ blocker verapamil, plasma membrane depolarization was enhanced under these conditions. Plasma membrane depolarization was greater and was shifted to lower ATPO concentrations in the absence of extracellular Ca2+ (Ca2+0), whereas the rise in [Ca2+]1 was greater in Na+-free media. Plasma membrane depolarization also occurred in Na+-free choline-or methylglucamine-containing media, and was potentiated by chelation of free divalent ions with EDTA, supporting previous reports pointing to ATP4-as the active species. Among a number of purine and pyrimidine nucleotides, only adenosine 5'-[y-thio]triphosphate and ADP were partially effective. Furthermore, ethidium bromide (Mr 380), Lucifer Yellow (Mr 463) and Eosin Yellowish (Mr 692) did not permeate through the ATPO-activated channel. These findings suggest that lytic effects of ATPO in mouse thymocytes depend on the activation of a membrane channel with low selectivity for cations and an Mr cut-off of 200.

The P2Z‐purinoceptor of human lymphocytes: actions of nucleotide agonists and irreversible inhibition by oxidized ATP

“…phocytes is the inhibition of ion fluxes which is observed at high extracellular Na' concentrations ( Figure la). A similar inhibitory action of extracellular Na' on ATPinduced Ca21 transients has been reported for mouse thymocytes (Pizzo et al, 1991) and human lymphocytes but is not observed with Ca2" transients produced by agonists such as anti human immunoglobulin antibody (Wiley et al, 1992), an observation which excludes some generalized effect of extracellular Na' on Ca2' homeostasis, e.g. by Ca2+-Na' countertransport.…”

“…Many features of this P2Y-receptor are functionally similar to the endothelial P2U-receptor except that UTP is the preferred agonist for the latter. ATP also induces the formation of ion-conducting channels (pores) in mouse and human lymphocytes (Wiley & Dubyak, 1989;Wiley et al, 1990;El-Moatassim et al, 1990;Pizzo et al, 1991), rat peritoneal mast cells (Tatham & Lindau, 1990), rat parotid acinar cells (Soltoff et al, 1992) and mouse macrophages (Greenberg et al, 1988). A subclass of purinoceptors termed P2z was first proposed for the receptor associated with this channel based on a specificity for the fully ionized ATP4-and need for relatively high (ca.…”

“…Several general features characterize the ionic fluxes associated with opening of the P2z-associated ion channel of lymphocytes (El-Moatassim et al, 1990;Wiley et al, 1990;Pizzo et al, 1991 (Wiley & Dubyak, 1989 (Dubyak & De Young, 1985) with excitation at 340 nm…”

Cytolytic P2X purinoceptors

“…All these observations suggested that susceptibility to ATP-mediated cytotoxicity was conferred by expression of a plasma membrane ATP-gated channel, and refractorines depended on the absence of such channel. Following studies demonstrated that ATP was cytotoxic not only to cells that express the typical`permeabilizing' P2Z receptor, such as macrophages, but also to those cells in which this nucleotide activates a cation-selective channel, with no evidence of permeabilization to larger hydrophylic solutes (Pizzo et al, 1991;Ferrari et al, 1994). This lead us to suggest that plasma membrane ATP-gated channels may form a new family of ion channels with different permeability and ion selectivity, but linked by the common property of causing cell death under conditions of sustained stimulation (Murgia et al, 1992b).…”

Transendothelial migration of lymphocytes in chronic lymphocytic leukaemia is impaired and involved down-regulation of both L-selectin and CD23

“…Human lymphocytes express receptors for extracellular ATP of the P2Z subtype which are predominantly found in cells of haemopoietic origin (Wiley & Dubyak, 1989;elMoatassim et al, 1989;Pizzo et al, 1991). Recently the gene for the human P2Z receptor has been cloned and on the basis of extensive homology to the six described members of the P2X family of receptors it is proposed that P2Z be termed P2X7 (Rassendren et al, 1997).…”