title: TRPM2 is an ion channel that modulates hematopoietic cell death through activation of caspases and PARP cleavage.
abstract: TRPM2 is a Ca(2+)-permeable channel activated by oxidative stress or TNF-alpha, and TRPM2 activation confers susceptibility to cell death. The mechanisms were examined here in human monocytic U937-ecoR cells. This cell line expresses full-length TRPM2 (TRPM2-L) and several isoforms including a short splice variant lacking the Ca(2+)-permeable pore region (TRPM2-S), which functions as a dominant negative. Treatment with H(2)O(2), a model of oxidative stress, or TNF-alpha results in reduced cell viability. Expression of TRPM2-L and TRPM2-S was modulated by retroviral infection. U937-ecoR cells expressing increased levels of TRPM2-L were treated with H(2)O(2) or TNF-alpha, and these cells exhibited significantly increased intracellular calcium concentration ([Ca(2+)](i)), decreased viability, and increased apoptosis. A dramatic increase in cleavage of caspases-8, -9, -3, and -7 and poly(ADP-ribose)polymerase (PARP) was observed, demonstrating a downstream mechanism through which cell death is mediated. Bcl-2 levels were unchanged. Inhibition of the [Ca(2+)](i) rise with the intracellular Ca(2+) chelator BAPTA blocked caspase/PARP cleavage and cell death induced after activation of TRPM2-L, demonstrating the critical role of [Ca(2+)](i) in mediating these effects. Downregulation of endogenous TRPM2 by RNA interference or increased expression of TRPM2-S inhibited the rise in [Ca(2+)](i), enhanced cell viability, and reduced numbers of apoptotic cells after exposure to oxidative stress or TNF-alpha, demonstrating the physiological importance of TRPM2. Our data show that one mechanism through which oxidative stress or TNF-alpha mediates cell death is activation of TRPM2, resulting in increased [Ca(2+)](i), followed by caspase activation and PARP cleavage. Inhibition of TRPM2-L function by reduction in TRPM2 levels, interaction with TRPM2-S, or Ca(2+) chelation antagonizes this important cell death pathway.
authors.affiliation: Department of Pediatrics, The Pennsylvania State University College of Medicine, Hershey, USA
authors.forename: Wenyi
authors.initials: W
authors.lastname: Zhang
authors.forename: Iwona
authors.initials: I
authors.lastname: Hirschler-Laszkiewicz
authors.forename: Qin
authors.initials: Q
authors.lastname: Tong
authors.forename: Kathleen
authors.initials: K
authors.lastname: Conrad
authors.forename: Shao-Cong
authors.initials: SC
authors.lastname: Sun
authors.forename: Linda
authors.initials: L
authors.lastname: Penn
authors.forename: Dwayne L
authors.initials: DL
authors.lastname: Barber
authors.forename: Richard
authors.initials: R
authors.lastname: Stahl
authors.forename: David J
authors.initials: DJ
authors.lastname: Carey
authors.forename: Joseph Y
authors.initials: JY
authors.lastname: Cheung
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Miller
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020169:Caspases / Q000378:metabolism*; D016923:Cell Death / Q000502:physiology*; D002460:Cell Line; D024161:Collagen Type XI / Q000378:metabolism*; D004789:Enzyme Activation; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000502:physiology*; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D016877:Oxidants / Q000378:metabolism; D018384:Oxidative Stress; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D011498:Protein Precursors / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D050053:TRPM Cation Channels / Q000235:genetics / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: C499319:COL11A2 protein, human; D024161:Collagen Type XI; D016877:Oxidants; D020033:Protein Isoforms; D011498:Protein Precursors; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D050053:TRPM Cation Channels; C121934:TRPM2 protein, human; D014409:Tumor Necrosis Factor-alpha; D006861:Hydrogen Peroxide; D020169:Caspases; D002118:Calcium