The P2X 7 receptor is a ligand-gated cation-selective channel that mediates ATP-induced apoptosis of cells of the immune system. We and others have shown that P2X 7 is nonfunctional both in lymphocytes and monocytes from some subjects. To study a possible genetic basis we sequenced DNA coding for the carboxyl-terminal tail of P2X 7 . In 9 of 45 normal subjects a heterozygous nucleotide substitution (1513A3 C) was found, whereas 1 subject carried the homozygous substitution that codes for glutamic acid to alanine at amino acid position 496. Surface expression of P2X 7 on lymphocytes was not affected by this E496A polymorphism, demonstrated both by confocal microscopy and immunofluorescent staining. Monocytes and lymphocytes from the E496A homozygote subject expressed nonfunctional receptor, whereas heterozygotes showed P2X 7 function that was half that of germline P2X 7 . Results of transfection experiments showed that the mutant P2X 7 receptor was nonfunctional when expressed at low receptor density but regained function at a high receptor density. This density dependence of mutant P2X 7 function was also seen on differentiation of fresh monocytes to macrophages with interferon-␥, which up-regulated mutant P2X 7 and partially restored its function. P2X 7 -mediated apoptosis of lymphocytes was impaired in homozygous mutant P2X 7 compared with germline (8.6 versus 35.2%). The data suggest that the glutamic acid at position 496 is required for optimal assembly of the P2X 7 receptor.Purinergic P2X 7 receptors are ligand-gated cation channels, present on cells of the immune and hemopoietic system, that have been shown to mediate the ATP-induced apoptotic death of monocytes (1), macrophages (2), and lymphocytes (3, 4). The P2X 7 receptor family has two transmembrane domains with intracellular amino and carboxyl termini and an oligomeric structure in the plasma membrane based on trimeric or larger complexes of identical subunits (5). Moreover, the P2X7 receptor does not appear to form heteropolymers with other P2X subtypes (6). The genes for both the rat and human P2X 7 receptors have now been cloned and show extensive homology (30 -40%) with the other members of the P2X receptor family, although P2X 7 differs in having a long carboxyl terminus of 240 amino acids from the inner membrane face (7). The genomic structure of P2X 7 consists of 13 exons, with exon 12 and exon 13 coding for the C-terminal tail of this molecule. There is strong evidence that this long carboxyl terminus is necessary for the permeability properties of the P2X 7 receptor, because truncation of this tail abolishes ATP-induced uptake of the fluorescent dye YoPro-1 (8). Studies of P2X 7 of macrophages or lymphocytes as well as of human embryonic kidney cells (HEK-293) expressing the cDNA for P2X 7 have shown features that are most unusual for a channel. These include the slow further dilatation following channel opening (9) and the activation of various proteases including membrane metalloproteases (10) and intracellular caspases (2, 11). The fully ...

To identify multiple sclerosis (MS) susceptibility loci, we conducted a genome-wide association study (GWAS) in 1,618 cases and used shared data for 3,413 controls. We performed replication in an independent set of 2,256 cases and 2,310 controls, for a total of 3,874 cases and 5,723 controls. We identified risk-associated SNPs on chromosome 12q13-14 (rs703842, P = 5.4 x 10(-11); rs10876994, P = 2.7 x 10(-10); rs12368653, P = 1.0 x 10(-7)) and upstream of CD40 on chromosome 20q13 (rs6074022, P = 1.3 x 10(-7); rs1569723, P = 2.9 x 10(-7)). Both loci are also associated with other autoimmune diseases. We also replicated several known MS associations (HLA-DR15, P = 7.0 x 10(-184); CD58, P = 9.6 x 10(-8); EVI5-RPL5, P = 2.5 x 10(-6); IL2RA, P = 7.4 x 10(-6); CLEC16A, P = 1.1 x 10(-4); IL7R, P = 1.3 x 10(-3); TYK2, P = 3.5 x 10(-3)) and observed a statistical interaction between SNPs in EVI5-RPL5 and HLA-DR15 (P = 0.001).

The P2X(7) receptor is an ATP-gated cation channel expressed in immune cells and plays a role in proinflammatory cytokine release from monocytes and macrophages. This study investigated the coinheritance of 12 functionally relevant single nucleotide polymorphisms (SNPs) in the human P2X(7) gene (P2RX7), and the functional effect of each singly and in combination was assessed by measurements of ATP-induced currents and ethidium(+) uptake. Genotyping of 3430 Caucasian subjects identified 4 common haplotypes in addition to the common (wild-type) P2X(7)-1. Two haplotypes (denoted P2X(7)-2 and P2X(7)-4) contained various combinations of gain-of-function SNPs. P2X(7)-4 was identified uniquely by the Gln-460 to Arg polymorphism (rs2230912). When expressed in HEK-293 cells, recombinant P2X(7)-2, and P2X(7)-4 haplotypes displayed a 3-fold and 5-fold increase, respectively, in receptor function compared to the wild-type P2X(7)-1. Both P2X(7) haplotypes contained the Ala-348>Thr polymorphism (rs1718119), and this mutation was critical for the gain-of-function effect. Peripheral blood monocytes and erythrocytes from subjects homozygous for gain-of-function P2X(7) haplotypes exhibited increased ATP-induced ethidium(+) uptake and (86)Rb(+) efflux, respectively, and this correlated with increased IL-1beta secretion from LPS-primed monocytes. Inheritance of these P2X(7) haplotypes predisposing to increased proinflammatory cytokine secretion may be important in genetic association studies of inflammatory, infectious, and psychiatric disorders.

The importance of the cytosolic C-terminal region of the P2X7 receptor (P2X7R) is unquestioned, yet little is known about the functional domains of this region and how they may contribute to the numerous properties ascribed to this receptor. A structure-function analysis of truncated and single-residue-mutated P2X7 receptors was performed in HEK-293 cells and Xenopus oocytes. Cells expressing receptors truncated at residue 581 (of 595) have negligible ethidium ion uptake, whereas those expressing the P2X7R truncated at position 582 give wild type ethidium ion uptake suggesting that pore formation requires over 95% of the C-terminal tail. Channel function was evident even in receptors that were truncated at position 380 indicating that only a small portion of the cytosolic region is required for channel activity. Surprisingly, truncations in the region between residues 551 and 581 resulted in non-functional receptors with no detectable cell surface expression in HEK-293 cells. A more detailed analysis revealed that mutations of single residues within this region could also abolish receptor function and cell surface expression, suggesting that this region may participate in regulating the surface expression of the pore-forming P2X7R.

1 Extracellular adenosine 5'-triphosphate (ATP) is an agonist for a P2Z receptor on human lymphocytes which mediates opening of a cation-selective ion channel, activation of phospholipase D and shedding of the adhesion molecule, L-selectin, from the cell surface. The isoquinolinesulphonamides, , a selective antagonist of Ca 2+ /calmodulin-dependent protein kinase II (CaMKII), and -(5 isoquinoline sulphonyl)benzyl]-2-(4 phenylpiperazine)ethyl]-5-isoquinolinesulphonamide) an inactive analogue, were used to investigate the possible role of CaMKII in these diverse e ects of extracellular ATP. 2 KN-62 potently antagonized ATP-stimulated Ba 2+ in¯ux into fura-2 loaded human lymphocytes with an IC 50 of 12.7+1.5 nM (n=3) and complete inhibition of the¯ux at a concentration of 500 nM. Similarly, KN-62 inhibited ATP-stimulated ethidium + uptake, measured by time resolved¯ow cytometry, with an IC 50 of 13.1+2.6 nM (n=4) and complete inhibition of the¯ux at 500 nM. 3 KN-04 antagonized ATP-stimulated Ba 2+ in¯ux with an IC 50 of 17.3+2.7 nM (n=3). Similarly, KN-04 inhibited ATP-stimulated ethidium + uptake with an IC 50 of 37.2+8.9 nM (n=4). Both¯uxes were completely inhibited at 500 nM KN-04. 4 ATP-stimulated phospholipase D activity, measured in [ 3 H]-oleic acid-labelled lymphocytes by the transphosphatidylation reaction, was antagonized by KN-62 and KN-04, with 50% inhibition at 5.9+1.2 and 9.7+2.8 nM (n=3), respectively. Both KN-62 and KN-04 inhibited ATP-stimulated shedding of L-selectin, measured by¯ow cytometric analysis of cell surface L-selectin, with IC 50 values of 31.5+4.5 and 78.7+10.8 nM (n=3), respectively. Neither of the isoquinolinesulphonamides (500 nM) inhibited phorbol ester-or ionomycin-stimulated phospholipase D activity or phorbol ester-induced shedding of L-selectin. 5 The inhibitory e ect of KN-62 or KN-04 on P2Z-mediated responses was slow in onset (5 min) and only partially reversed by washing the cells. 6 Both KN-62 and KN-04 (at 500 nM) had no e ect on uridine 5'-triphosphate (UTP)-stimulated Ca 2+ transients in fura-2 loaded human neutrophils, a response which is mediated by the P2Y 2 receptor. 7 Thus, KN-62 and KN-04 are potent antagonists of the P2Z receptor and at nanomolar concentrations inhibit all known responses mediated by the P2Z receptor of human lymphocytes. In contrast, KN-62 and KN-04 had no e ect on responses mediated by the P2Y 2 receptor of neutrophils. Moreover, since KN-62 and KN-04 are almost equipotent, the P2Z-mediated responses do not involve CaMKII, but indicate that the isoquinolinesulphonamides are potent and direct inhibitors of the P2Z-receptor.

We recently reported that Swedish V H 3-21-using chronic lymphocytic leukemia (CLL) patients showed restricted immunoglobulin gene features and poor prognosis despite V H mutation status. To investigate this further, we analyzed the V H and V L gene rearrangements in 90 V H 3-21 ؉ patients from Sweden, Germany, Italy, United States, Finland, and Australia and correlated these data with survival and other prognostic markers. Sixty-three percent exhibited mutated V H genes and 37% unmutated V H genes. Fifty (56%) patients displayed a short and homologous heavy-

The P2X 7 receptor is a ligand-gated channel that is highly expressed on mononuclear cells and that mediates ATP-induced apoptosis of these cells. Wide variations in the function of the P2X 7 receptor have been observed, in part because of a loss-of-function polymorphism that changes Glu-496 to Ala without affecting the surface expression of the receptor on lymphocytes. In this study a second polymorphism (Ile-568 to Asn) has been found in heterozygous dosage in three of 85 normal subjects and in three of 45 patients with chronic lymphocytic leukemia. P2X 7 function was measured by ATPinduced fluxes of Rb ؉ , Ba 2؉ , and ethidium ؉ into various lymphocyte subsets and was decreased to values of ϳ25% of normal. The expression of the P2X 7 receptor on lymphocytes was approximately half that of normal values as measured by the binding of fluorescein-conjugated monoclonal antibody. Transfection experiments showed that P2X 7 carrying the Ile-568 to Asn mutation was non-functional because of the failure of cell surface expression. The differentiation of monocytes to macrophages with interferon-␥ up-regulated P2X 7 function in cells heterozygous for the Ile-568 to Asn mutation to a value around 50% of normal. These data identify a second loss-of-function polymorphism within the P2X 7 receptor and show that Ile-568 is critical to the trafficking domain, which we have shown to lie between residues 551 and 581.The purinergic P2X 7 receptor is a ligand-gated channel, selective for cationic permeants, which has a wide distribution including cells of the immune and hemopoietic system (1, 2). Activation of this receptor by brief exposure to extracellular ATP opens a channel that allows Ca 2ϩ and Na ϩ influx and K ϩ efflux and that initiates a cascade of intracellular downstream events. These include the stimulation of phospholipase D (3, 4), the activation of membrane metalloproteases (5-7), and the stimulation of intracellular caspases, which eventually lead to the apoptotic death of the target cell (8, 9). P2X 7 activation also leads to extensive membrane blebbing (10), which is a typical morphological feature of the apoptotic process. P2X 7 receptors have two transmembrane domains with intracellular amino and carboxyl termini, and the P2X 7 receptor differs from other members of the P2X receptor family in having a long carboxyl terminus of 240 amino acids from the inner membrane face (11). This long carboxyl terminus is necessary for the permeability properties of the P2X 7 receptor because truncation of this tail abolishes ATP-induced uptake of the fluorescent dye Yo-Pro-1 (12). P2X 7 has an oligomeric structure in the membrane based on trimeric or larger complexes of identical subunits (13,14), and there is evidence that P2X 7 interacts with a number of structural and adhesion proteins in a complex at the cell surface (15). Phosphorylation of a tyrosine at amino acid 343 of the P2X 7 primary structure has been proposed as being important for maintaining the full activity of the P2X 7 channel (15). A number of regulatory d...

The 1513C allele increases susceptibility to extrapulmonary TB, and this defect is associated with the reduction in the capacity of macrophages to kill M. tuberculosis.