Synergistic regulation of endogenous TRPM2 channels by adenine dinucleotides in primary human neutrophils

Abstract

SummaryThe Ca 2+ -permeable TRPM2 channel is a dual function protein that is activated by intracellular ADPR through its enzymatic pyrophosphatase domain with Ca 2+ acting as a co-factor. Other TRPM2 regulators include cADPR, NAADP and H 2 O 2 , which synergize with ADPR to potentiate TRPM2 activation. Although TRPM2 has been thoroughly characterized in overexpression or cell-line systems, little is known about the features of TRPM2 in primary cells. We here characterize the regulation of TRPM2 activation in human neutrophils and report that ADPR activates TRPM2 with an effective half-maximal concentration (EC 50 ) of 1 μM. Potentiation by Ca 2+ is dose-dependent with an EC 50 of 300 nM. Both cADPR and NAADP activate TRPM2, albeit with lower efficacy than in the presence of subthreshold levels of ADPR (100 nM), which significantly shifts the EC 50 for cADPR from 44 μM to 3 μM and for NAADP from 95 μM to 1 μM. TRPM2 activation by ADPR can be suppressed by AMP with an IC 50 of 10 μM and cADPR-induced activation can be blocked by 8-Bromo-cADPR. We further show that 100 μM H 2 O 2 enables subthreshold concentrations of ADPR (100 nM) to activate TRPM2. We conclude that agonistic and antagonistic characteristics of TRPM2 as seen in overexpression systems are largely compatible with the functional properties of TRPM2 currents measured in human neutrophils, but the potencies of agonists in primary cells are significantly higher.

Generation of Cyclic ADP-ribose and Nicotinic Acid Adenine Dinucleotide Phosphate by CD38 for Ca2+ Signaling in Interleukin-8-treated Lymphokine-activated Killer Cells

“…Furthermore, it is of interest to observe that the location of NAADP production by CD38 appears to be distinct from that of cADPR synthesis; cADPR production is predominantly in early endosomes (45), whereas NAADP is produced mainly in lysosome-related acidic organelles (Ref. 38 and Fig. 4).…”

“…However, we could not find any significant signals with high concentration of the nucleotides (data not shown). It was reported that NAADP-mediated Ca 2ϩ influx is triggered from the TRPM2 channel (38). To determine the role of TRPM2 on IL-8-induced Ca 2ϩ signaling, we measured the change in [Ca 2ϩ ] i in the presence of ACA, a specific TRPM2 channel blocker.…”

Redox signal-mediated sensitization of transient receptor potential melastatin 2 (TRPM2) to temperature affects macrophage functions

“…Transient receptor potential melastatin 2 (TRPM2) is a thermosensitive, Ca 2+ -permeable cation channel expressed by a wide range of immunocytes, including macrophages, whose function is gradually being clarified (3)(4)(5)(6)(7)(8)(9). We previously reported that heat stimulation activates TRPM2 in the presence of low concentrations of agonists, such as adenosine diphosphate ribose (ADPR) and related molecules (10).…”

“…Of note, TRPM2 is expressed by lymphocytes, neutrophils, and monocytes/macrophages (3)(4)(5)(6)(7)(8), whose activities have a strong relationship with body temperature (2,41). This suggests that TRPM2 might have a broader role in the temperature sensitivity of the immune system.…”

Role of the Neutrophil NADPH Oxidase and S100A8/A9 in the Pathophysiology of Chronic Inflammation

“…Accumulating evidence show that members of TRPC could be activated by diacylglycerol (Bréchard et al, 2008;. In addition, cyclic adenosine diphosphoribose, via its hydrolysis product (adenosine diphosphoribose), could support Ca 2+ entry through the activation of TRPM2, a member of transient receptor potential family (Heiner et al, 2006;Howard et al, 1993;Lange et al, 2008).…”