Dataset Information

Identification of direct and indirect effectors of the transient receptor potential melastatin 2 (TRPM2) cation channel.

ABSTRACT: Transient receptor potential melastatin 2 (TRPM2) is a Ca(2+)-permeable cation channel involved in physiological and pathophysiological processes linked to oxidative stress. TRPM2 channels are co-activated by intracellular Ca(2+) and ADP-ribose (ADPR) but also modulated in intact cells by several additional factors. Superfusion of TRPM2-expressing cells with H(2)O(2) or intracellular dialysis of cyclic ADPR (cADPR) or nicotinic acid adenine dinucleotide phosphate (NAADP) activates, whereas dialysis of AMP inhibits, TRPM2 whole-cell currents. Additionally, H(2)O(2), cADPR, and NAADP enhance ADPR sensitivity of TRPM2 currents in intact cells. Because in whole-cell recordings the entire cellular machinery for nucleotide and Ca(2+) homeostasis is intact, modulators might affect TRPM2 activity either directly, by binding to TRPM2, or indirectly, by altering the local concentrations of the primary ligands ADPR and Ca(2+). To identify direct modulators of TRPM2, we have studied the effects of H(2)O(2), AMP, cADPR, NAADP, and nicotinic acid adenine dinucleotide in inside-out patches from Xenopus oocytes expressing human TRPM2, by directly exposing the cytosolic faces of the patches to these compounds. H(2)O(2) (1 mM) and enzymatically purified cADPR (10 ?M) failed to activate, whereas AMP (200 ?M) failed to inhibit TRPM2 currents. NAADP was a partial agonist (maximal efficacy, ?50%), and nicotinic acid adenine dinucleotide was a full agonist, but both had very low affinities (K(0.5) = 104 and 35 ?M). H(2)O(2), cADPR, and NAADP did not enhance activation by ADPR. Considering intracellular concentrations of these compounds, none of them are likely to directly affect the TRPM2 channel protein in a physiological context.

SUBMITTER: Toth B

PROVIDER: S-EPMC2943302 | biostudies-literature | 2010 Sep

REPOSITORIES: biostudies-literature

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Identification of direct and indirect effectors of the transient receptor potential melastatin 2 (TRPM2) cation channel.

Tóth Balázs B Csanády László L

The Journal of biological chemistry 20100722 39

Transient receptor potential melastatin 2 (TRPM2) is a Ca(2+)-permeable cation channel involved in physiological and pathophysiological processes linked to oxidative stress. TRPM2 channels are co-activated by intracellular Ca(2+) and ADP-ribose (ADPR) but also modulated in intact cells by several additional factors. Superfusion of TRPM2-expressing cells with H(2)O(2) or intracellular dialysis of cyclic ADPR (cADPR) or nicotinic acid adenine dinucleotide phosphate (NAADP) activates, whereas dialy ...[more]

PMID: 20650899

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Project description:Transient receptor potential melastatin 7 (TRPM7) is a bifunctional protein comprising a magnesium (Mg(2+))/cation channel and a kinase domain. We previously demonstrated that vasoactive agents regulate vascular TRPM7. Whether TRPM7 plays a role in the pathophysiology of hypertension and associated cardiovascular dysfunction is unknown. We studied TRPM7 kinase-deficient mice (TRPM7?kinase; heterozygous for TRPM7 kinase) and wild-type (WT) mice infused with angiotensin II (Ang II; 400 ng/kg per minute, 4 weeks). TRPM7 kinase expression was lower in heart and aorta from TRPM7?kinase versus WT mice, effects that were further reduced by Ang II infusion. Plasma Mg(2+) was lower in TRPM7?kinase versus WT mice in basal and stimulated conditions. Ang II increased blood pressure in both strains with exaggerated responses in TRPM7?kinase versus WT groups (P<0.05). Acetylcholine-induced vasorelaxation was reduced in Ang II-infused TRPM7?kinase mice, an effect associated with Akt and endothelial nitric oxide synthase downregulation. Vascular cell adhesion molecule-1 expression was increased in Ang II-infused TRPM7 kinase-deficient mice. TRPM7 kinase targets, calpain, and annexin-1, were activated by Ang II in WT but not in TRPM7?kinase mice. Echocardiographic and histopathologic analysis demonstrated cardiac hypertrophy and left ventricular dysfunction in Ang II-treated groups. In TRPM7 kinase-deficient mice, Ang II-induced cardiac functional and structural effects were amplified compared with WT counterparts. Our data demonstrate that in TRPM7?kinase mice, Ang II-induced hypertension is exaggerated, cardiac remodeling and left ventricular dysfunction are amplified, and endothelial function is impaired. These processes are associated with hypomagnesemia, blunted TRPM7 kinase expression/signaling, endothelial nitric oxide synthase downregulation, and proinflammatory vascular responses. Our findings identify TRPM7 kinase as a novel player in Ang II-induced hypertension and associated vascular and target organ damage.

Project description:Oxidants generated by activated endothelial cells are known to induce apoptosis, a pathogenic feature of vascular injury and inflammation from multiple pathogeneses. The melastatin-family transient receptor potential 2 (TRPM2) channel is an oxidant-sensitive Ca2+ permeable channel implicated in mediating apoptosis; however, the mechanisms of gating of the supranormal Ca2+ influx required for initiating of apoptosis are not understood.Here, we addressed the role of TRPM2 and its interaction with the short splice variant TRPM2 short variant (TRPM2-S) in mediating the Ca2+ entry burst required for induction of endothelial cell apoptosis.We observed that TRPM2-S was basally associated with TRPM2 in the endothelial plasmalemma, and this interaction functioned to suppress TRPM2-dependent Ca2+ gating constitutively. Reactive oxygen species production in endothelial cells or directly applying reactive oxygen species induced protein kinase C-? activation and phosphorylation of TRPM2 at Ser 39. This in turn stimulated a large entry of Ca2+ and activated the apoptosis pathway. A similar TRPM2-dependent endothelial apoptosis mechanism was seen in intact vessels. The protein kinase C-?-activated phosphoswitch opened the TRPM2 channel to allow large Ca2+ influx by releasing TRPM2-S inhibition of TRPM2, which in turn activated caspase-3 and cleaved the caspase substrate poly(ADP-ribose) polymerase.Here, we describe a fundamental mechanism by which activation of the trp superfamily TRPM2 channel induces apoptosis of endothelial cells. The signaling mechanism involves reactive oxygen species-induced protein kinase C-? activation resulting in phosphorylation of TRPM2-S that allows enhanced TRPM2-mediated gating of Ca2+ and activation of the apoptosis program. Strategies aimed at preventing the uncoupling of TRPM2-S from TRPM2 and subsequent Ca2+ gating during oxidative stress may mitigate endothelial apoptosis and its consequences in mediating vascular injury and inflammation.

Dataset Information

Identification of direct and indirect effectors of the transient receptor potential melastatin 2 (TRPM2) cation channel.

Publications

Identification of direct and indirect effectors of the transient receptor potential melastatin 2 (TRPM2) cation channel.

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