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In summary, studies continue to accumulate the evidence supporting a vital role of an alteration in the expression and/or activity of ion channels in both cancer cells and cancer-contacting cells in determining cancer hallmarks. Ion channels, cancer, cell death, proliferation, migration, metastasis, resistance to treatment Keywords: ion channels; cancer; cell death; proliferation; migration; metastasis; resistance to treatment EN ion channels cancer cell death proliferation migration metastasis resistance to treatment 1 3 3 06/08/21 20210603 NES 210603 Mammalian cells express a large number of structurally distinct ion channels on the cell surface and also in the membranes of intracellular organelles. [Extracted from the article]

Transient receptor potential melastatin 2 (TRPM2) channel activation by reactive oxygen species (ROS) plays a critical role in delayed neuronal cell death, responsible for postischemia brain damage via altering intracellular Zn2+ homeostasis, but a mechanistic understanding is still lacking. Here, we showed that H2O2 induced neuroblastoma SH‐SY5Y cell death with a significant delay, dependently of the TRPM2 channel and increased [Zn2+]i, and therefore used this cell model to investigate the mechanisms underlying ROS‐induced TRPM2‐mediated delayed cell death. H2O2 increased concentration‐dependently the [Zn2+]i and caused lysosomal dysfunction and Zn2+ loss and, furthermore, mitochondrial Zn2+ accumulation, fragmentation, and ROS generation. Such effects were suppressed by preventing poly(adenosine diphosphate ribose, ADPR) polymerase‐1‐dependent TRPM2 channel activation with PJ34 and 3,3′,5,5′‐tetra‐tert‐butyldiphenoquinone, inhibiting the TRPM2 channel with 2‐aminoethoxydiphenyl borate (2‐APB) and N‐(p‐amylcinnamoyl)anthranilic acid, or chelating Zn2+ with N,N,N,N‐tetrakis(2‐pyridylmethyl)‐ethylenediamine (TPEN). Bafilomycin‐induced lysosomal dysfunction also resulted in mitochondrial Zn2+ accumulation, fragmentation, and ROS generation that were inhibited by PJ34 or 2‐APB, suggesting that these mitochondrial events are TRPM2 dependent and sequela of lysosomal dysfunction. Mitochondrial TRPM2 expression was detected and exposure to ADPR‐induced Zn2+ uptake in isolated mitochondria, which was prevented by TPEN. H2O2‐induced delayed cell death was inhibited by apocynin and diphenyleneiodonium, nicotinamide adenine dinucleotide phosphate hydrogen (NADPH) oxidase (NOX) inhibitors, GKT137831, an NOX1/4‐specific inhibitor, or Gö6983, a protein kinase C (PKC) inhibitor. Moreover, inhibition of PKC/NOX prevented H2O2‐induced ROS generation, lysosomal dysfunction and Zn2+ release, and mitochondrial Zn2+ accumulation, fragmentation and ROS generation. Collectively, these results support a critical role for the TRPM2 channel in coupling PKC/NOX‐mediated ROS generation, lysosomal Zn2+ release, and mitochondrial Zn2+ accumulation, and ROS generation to form a vicious positive feedback signaling mechanism for ROS‐induced delayed cell death. Transient receptor potential melastatin 2 (TRPM2) channel activation by reactive oxygen species (ROS) is critically responsible for delayed neuronal cell death, responsible for postischemia brain damage via altering intracellular Zn2+ homeostasis. In this study, we provide evidence to support that the TRPM2 channel plays a critical role in forming a vicious positive feedback signaling mechanism for ROS‐induced delayed cell death. [ABSTRACT FROM AUTHOR]

Cu2+ is an essential metal ion that plays a critical role in the regulation of a number of ion channels and receptors in addition to acting as a cofactor in a variety of enzymes. Here, we showed that human melastatin transient receptor potential 2 (hTRPM2) channel is sensitive to inhibition by extracellular Cu2+. Cu2+ at concentrations as low as 3 µM inhibited the hTRPM2 channel completely and irreversibly upon washing or using Cu2+ chelators, suggesting channel inactivation. The Cu2+-induced inactivation was similar when the channels conducted inward or outward currents, indicating the permeating ions had little effect on Cu2+-induced inactivation. Furthermore, Cu2+ had no effect on singe channel conductance. Alanine substitution by site-directed mutagenesis of His995 in the pore-forming region strongly attenuated Cu2+-induced channel inactivation, and mutation of several other pore residues to alanine altered the kinetics of channel inactivation by Cu2+. In addition, while introduction of the P1018L mutation is known to result in channel inactivation, exposure to Cu2+ accelerated the inactivation of this mutant channel. In contrast with the hTRPM2, the mouse TRPM2 (mTRPM2) channel, which contains glutamine at the position equivalent to His995, was insensitive to Cu2+. Replacement of His995 with glutamine in the hTRPM2 conferred loss of Cu2+-induced channel inactivation. Taken together, these results suggest that Cu2+ inactivates the hTRPM2 channel by interacting with the outer pore region. Our results also indicate that the amino acid residue difference in this region gives rise to species-dependent effect by Cu2+ on the human and mouse TRPM2 channels. [ABSTRACT FROM AUTHOR]

idic pH is an important parameter regulating ion channel activity and its biological function. This study investigated inhibition of the hTRPM2 channels by extracellular acidic pH and compared the sensitivity of human (h) and mouse (m) TRPM2 channel to such an inhibition. The initial inhibition of hTRPM2 channel currents was substantially reversible, but the reversibility progressively diminished as the exposure to acidic pH was prolonged and it was essentially lost in the steady state, suggesting that extracellular acidic pH induces initial reversible inhibition and subsequent irreversible inactivation. Like the hTRPM2 channel, the mTRPM2 channel was sensitive to inhibition by pH 4.0-5.5, but the kinetics was significantly slower. Moreover, in contrast to the complete inhibition of the hTRPM2 channel, the mTRPM2 channel was insensitive to pH 6.0. Replacement of residue Gln in the outer pore with the equivalent residue His in the hTRPM2 channel resulted in a mutant mTRPM2 channel with the pH sensitivity and kinetics of inhibition of the wild-type hTRPM2 channel. Conversely, the reciprocal mutation H995Q in the hTRPM2 channel dramatically slowed down the kinetics of inhibition. Swapping other residues in the pore region failed to produce such opposing effects. Taken together, our results suggest a crucial role of residue His/Gln in the outer pore of TRPM2 channels in determining species-dependent effects of extracellular acidic pH. [ABSTRACT FROM AUTHOR]

Transient receptor potential melastatin 2 (TRPM2) proteins form multiple-subunit complexes, most likely homotetramers, which operate as Ca2+-permeable, nonselective cation channels activated by intracellular ADP-ribose (ADPR) and oxidative stress. Each TRPM2 channel subunit is predicted to contain two coiled-coil (CC) domains, one in the N-terminus and the other in the C-terminus. Our recent study has shown that the C-terminal CC domain plays an important, but not exclusive, role in the TRPM2 channel assembly. This study aimed to examine the potential role of the N-terminal CC domain. Domain deletion dramatically reduced protein expression and abolished ADPR-evoked currents but did not alter the subunit interaction. Deletion of both CC domains strongly attenuated the subunit interaction, confirming that the C-terminal CC domain is critical in the subunit interaction. Glutamine substitutions into individual hydrophobic residues at positions a and d in the heptad repeats to disrupt the CC formation had no effect on protein expression, subunit interaction, or ADPR-evoked currents. Mutation of Ile(658) to glutamine, which did not perturb the CC formation, decreased ADPR-evoked currents without affecting protein expression, subunit interaction, or membrane trafficking. These results collectively suggest the requirement for the N-terminal CC domain for protein expression and function, but not subunit interaction, of the TRPM2 channel. [ABSTRACT FROM AUTHOR]

Mammalian homologues of Drosophila melanogaster transient receptor potential (TRP) are a large family of multimeric cation channels that act, or putatively act, as sensors of one or more chemical factor. Major research objectives are the identification of endogenous activators and the determination of cellular and tissue functions of these channels. Here we show the activation of TRPC5 (canonical TRP 5) homomultimeric and TRPC5–TRPC1 heteromultimeric channels by extracellular reduced thioredoxin, which acts by breaking a disulphide bridge in the predicted extracellular loop adjacent to the ion-selectivity filter of TRPC5. Thioredoxin is an endogenous redox protein with established intracellular functions, but it is also secreted and its extracellular targets are largely unknown. Particularly high extracellular concentrations of thioredoxin are apparent in rheumatoid arthritis, an inflammatory joint disease that disables millions of people worldwide. We show that TRPC5 and TRPC1 are expressed in secretory fibroblast-like synoviocytes from patients with rheumatoid arthritis, that endogenous TRPC5–TRPC1 channels of the cells are activated by reduced thioredoxin, and that blockade of the channels enhances secretory activity and prevents the suppression of secretion by thioredoxin. The data indicate the presence of a previously unrecognized ion-channel activation mechanism that couples extracellular thioredoxin to cell function. [ABSTRACT FROM AUTHOR]

Aims: Dysfunction of neurovascular pericytes underlies breakdown of the blood-brain barrier, but the molecular mechanisms are largely unknown. In this study, we evaluated the role of the transient receptor potential melastatin-related 2 (TRPM2) channel and autophagy during brain pericyte injury both in vitro and in vivo. Results: A rapid induction in autophagy in human brain vascular pericytes, in the zinc oxide nanoparticles (ZnO-NP)-induced cell stress model, was paralleled with an increase in the expression of the TRPM2-S truncated isoform, which was abolished by treatment with a nitric oxide synthase inhibitor and a peroxynitrite scavenger. Furthermore, Y1485 in the C-terminus of the TRPM2 protein was identified as the tyrosine nitration substrate by mass spectrometry. Overexpression of the Y1485S TRPM2 mutant reduced LC3-II accumulation and pericyte injury induced by ZnO-NP. Consistently, LC3-II accumulation was reduced and pericytes were better preserved in intact brain microvessels of the TRPM2 knockout mice after ZnO-NP-induced vascular injury. Innovation and Conclusions: Our present study has revealed a novel mechanism of autophagy disturbance secondary to nitrosative stress-induced tyrosine nitration of TRPM2 during pericyte injury. Antioxid. Redox Signal. 27, 1297-1316. [ABSTRACT FROM AUTHOR]