Signaling through P2X7 Receptor in Human T Cells Involves p56 , MAP Kinases, and Transcription Factors AP-1 and NF-κB

Abstract

ATP-gated ion channel P2X receptors are expressed on the surface of most immune cells and can trigger multiple cellular responses, such as membrane permeabilization, cytokine production, and cell proliferation or apoptosis. Despite broad distribution and pleiotropic activities, signaling pathways downstream of these ionotropic receptors are still poorly understood. Here, we describe intracellular signaling events in Jurkat cells treated with millimolar concentrations of extracellular ATP. Within minutes, ATP treatment resulted in the phosphorylation and activation of p56 lck kinase, extracellular signalregulated kinase (ERK), and c-Jun N-terminal kinase but not p38 kinase. These effects were wholly dependent upon the presence of extracellular Ca 2؉ ions in the culture medium. Nevertheless, calmodulin antagonist calmidazolium and CaM kinase inhibitor KN-93 both had no effect on the activation of p56 lck and ERK, whereas a pretreatment of Jurkat cells with MAP kinase kinase inhibitor P098059 was able to abrogate phosphorylation of ERK. Extracellular ATP and other nucleotides act through specific cell surface receptors and can regulate a variety of cellular responses in many cell types and tissues (1-7). Among them are such different phenomena as platelet aggregation, smooth muscle contractility, excitatory transmitter function, mitogenic stimulation, or induction of cell death (reviewed in Refs. 1 and 8). The biological effects of extracellular nucleotides are mediated via stimulation of two primary classes of purinergic receptors, P1 and P2. The P1 receptors are responsive to adenosine, whereas the P2 receptors respond to a variety of nucleotides, including ATP (7, 9). The P2 receptors are subdivided in two mechanistically distinct subclasses, the metabotropic G protein-coupled P2Y receptors (P2Y1, P2Y2, P2Y4, P2Y6, and P2Y11-13) and the ionotropic ligand-gated channel P2X receptors (P2X1-7) (9 -12). Activation of the P2Y receptors generally induces downstream signaling through the G protein-coupled activation of phospholipase C, followed by Ca 2ϩ mobilization from intracellular stores (13,14). The P2Y11 also activates adenylyl cyclase, whereas the P2Y12 inhibits it (15). The seven subunits of the ionotrophic ATP-gated P2X receptor family comprise a different subclass, ranging from 379 to 595 amino acids in length and regulating the intracellular level of Ca 2ϩ by ligand-stimulated increase in cell membrane permeability for extracellular Ca 2ϩ ions (7,16,17). The P2X7 receptor is a 595-amino acid polypeptide and has a structure similar to that of other P2X receptors with two membrane-spanning domains, a large extracellular loop, and intracellular N-and C-terminal domains (18,19). In contrast to other P2X receptors, the P2X7 C-terminal intracellular chain is about 200 amino acids longer (20,21). The P2X7 has a pharmacological profile similar to the receptor previously designated as P2Z, with prominent expression in many immune cells (lymphocytes, monocytes/macrophages, dendritic, mesangial, and microglial cells) (...

P2 receptor-mediated signaling in mast cell biology

“…In addition, we have demonstrated that stimulation with extracellular ATP mediates activation of p56 lck , ERK1/2, and JNK in Jurkat T cells [77].…”

Cell signaling via the P2X7 nucleotide receptor: linkage to ROS production, gene transcription, and receptor trafficking

“…Stimulation of Jurkat T cells with P2X 7 agonists induces the activation of the lymphoidspecific cytoplasmic protein tyrosine kinase p56 lck [84]. Although the activation of cFos and c-Jun by P2X 7 ligands occurs in Jurkat T cells, it is absent in a p56…”

“…Furthermore, co-treatment of human fetal astrocytes with IL-1β and ATP was seen to induce an activation of AP-1 that is more robust than that observed with IL-1β alone [93], and treatment with P2 receptor antagonists inhibits cytokine-induced AP-1 activation [93,94]. It has been suggested that stimulation of Jurkat T cells induces AP-1 DNA-binding activity that results from increased c-Jun and cFos expression [84]. Conversely, in the present report, we show that stimulation of human PBMCs with P2X 7 agonists does not appear to enhance cFos expression (Fig.…”

“…Activation of P2X 7 has been linked not only to apoptosis, but also to lymphocyte cell proliferation [25,84] and transcriptional activation in immune cells [85]. As noted Fig.…”

“…lck -deficient JCaM1T cell line [84], suggesting that this kinase may play a role in P2X 7 -induced AP-1 activation in T cells. A role for MAPKs in P2X 7 -dependent AP-1 activation in monocytic cells has also been supported.…”