title: Identification of a novel transport-independent function of PiT1/SLC20A1 in the regulation of TNF-induced apoptosis.
abstract: PiT1/SLC20A1 is a sodium-dependent P(i) transporter expressed by most mammalian cells. Interestingly, PiT1 transcription has been shown to be up-regulated by the tumor necrosis factor α (TNF), and we have now investigated the possible involvement of PiT1 in TNF-induced apoptosis. We show that PiT1-depleted cells are more sensitive to the proapoptotic activity of TNF (i.e. when the antiapoptotic NFκB pathway is inactivated). These observations were made in the human HeLa cancer cell line either transiently or stably depleted in PiT1 by RNA interference and in immortalized mouse embryonic fibroblasts isolated from PiT1 knock-out embryos. Depletion of the closely related family member PiT2 had no effect on TNF-induced apoptosis, showing that this effect was specific to PiT1. The increased sensitivity of PiT1-depleted cells was evident regardless of the presence or absence of extracellular P(i), suggesting that a defect in P(i) uptake was not involved in the observed phenotype. Importantly, we show that the re-expression of a P(i) uptake mutant of PiT1 in PiT1(-/-) mouse embryonic fibroblasts delays apoptosis as efficiently as the WT protein, showing that this function of PiT1 is unrelated to its transport activity. Caspase-8 is more activated in PiT1-depleted cells, and our data reveal that the sustained activation of the MAPK JNK is up-regulated in response to TNF. JNK activity is actually involved in PiT1-depleted cell death because specific JNK inhibitors delay apoptosis.
authors.affiliation: Growth and Signaling Research Center, INSERM U845, F-75015 Paris, France. christine.salaun@inserm.fr
authors.forename: Christine
authors.initials: C
authors.lastname: Salaün
authors.forename: Christine
authors.initials: C
authors.lastname: Leroy
authors.forename: Alice
authors.initials: A
authors.lastname: Rousseau
authors.forename: Valérie
authors.initials: V
authors.lastname: Boitez
authors.forename: Laurent
authors.initials: L
authors.lastname: Beck
authors.forename: Gérard
authors.initials: G
authors.lastname: Friedlander
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D053181:Caspase 8 / Q000235:genetics / Q000378:metabolism; D002461:Cell Line, Transformed; D004622:Embryo, Mammalian / Q000166:cytology / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D048670:MAP Kinase Kinase 4 / Q000235:genetics / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D034622:RNA Interference; D050611:Sodium-Phosphate Cotransporter Proteins, Type III / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects*
chemical_list: D047428:Protein Kinase Inhibitors; C493586:SLC20A1 protein, human; C493587:Slc20a1 protein, mouse; D050611:Sodium-Phosphate Cotransporter Proteins, Type III; D014409:Tumor Necrosis Factor-alpha; D048670:MAP Kinase Kinase 4; C505530:CASP8 protein, human; C505526:Casp8 protein, mouse; D053181:Caspase 8
references.citation: Eur J Neurosci. 2010 Jun;31(12):2142-55
references.pmid: 20529123
references.citation: Neuron. 2007 Dec 20;56(6):1019-33
references.pmid: 18093524
references.citation: J Virol. 2002 Jul;76(13):6442-52
references.pmid: 12050356
references.citation: Cell. 2006 Feb 10;124(3):601-13
references.pmid: 16469705
references.citation: Development. 2007 Mar;134(5):867-79
references.pmid: 17251264
references.citation: Cell Growth Differ. 1990 Mar;1(3):119-27
references.pmid: 2078500
references.citation: Genesis. 2009 Dec;47(12):858-63
references.pmid: 19882669
references.citation: Proc Natl Acad Sci U S A. 1991 Apr 1;88(7):2830-4
references.pmid: 1849278
references.citation: Cell Death Differ. 2004 Mar;11(3):301-13
references.pmid: 14685158
references.citation: J Biol Chem. 2007 Apr 6;282(14):10585-93
references.pmid: 17296611
references.citation: Eur J Biochem. 2002 May;269(10):2434-9
references.pmid: 12027880
references.citation: Diabetes. 2001 Jan;50(1):77-82
references.pmid: 11147798
references.citation: Mol Biol Cell. 2006 Jan;17(1):317-26
references.pmid: 16267270
references.citation: Science. 1996 Nov 1;274(5288):782-4
references.pmid: 8864118
references.citation: Proc Natl Acad Sci U S A. 2008 Nov 11;105(45):17532-7
references.pmid: 18988732
references.citation: Curr Opin Cell Biol. 2002 Apr;14(2):214-20
references.pmid: 11891121
references.citation: Nature. 2001 Nov 15;414(6861):313-7
references.pmid: 11713531
references.citation: Cell Death Differ. 2003 Jan;10(1):45-65
references.pmid: 12655295
references.citation: Diabetes. 2002 May;51(5):1319-36
references.pmid: 11978627
references.citation: Mol Cell Biol. 2004 Dec;24(24):10844-56
references.pmid: 15572687
references.citation: Circ Res. 2007 Feb 16;100(3):328-41
references.pmid: 17307971
references.citation: Cell. 2003 Oct 3;115(1):61-70
references.pmid: 14532003
references.citation: Mol Cell. 2003 Jun;11(6):1479-89
references.pmid: 12820962
references.citation: Development. 2007 Jan;134(1):147-55
references.pmid: 17164420
references.citation: Science. 2002 May 31;296(5573):1634-5
references.pmid: 12040173
references.citation: J Biol Chem. 2009 Nov 6;284(45):31363-74
references.pmid: 19726692
references.citation: Microbiol Mol Biol Rev. 2008 Mar;72(1):157-96, table of contents
references.pmid: 18322038
references.citation: Nat Immunol. 2009 Apr;10(4):348-55
references.pmid: 19295631
references.citation: Proc Natl Acad Sci U S A. 1994 Jul 19;91(15):7071-5
references.pmid: 8041748
references.citation: J Virol. 2003 Oct;77(19):10414-22
references.pmid: 12970426
references.citation: Proc Natl Acad Sci U S A. 2008 Oct 28;105(43):16809-13
references.pmid: 18922779
references.citation: Proc Natl Acad Sci U S A. 1994 Jan 4;91(1):78-82
references.pmid: 8278411
references.citation: Trends Cell Biol. 1998 Mar;8(3):107-11
references.pmid: 9695819
references.citation: Nat Rev Immunol. 2005 Oct;5(10):749-59
references.pmid: 16175180
references.citation: Proc Natl Acad Sci U S A. 2001 Nov 20;98(24):13681-6
references.pmid: 11717429
references.citation: EMBO J. 2006 Nov 29;25(23):5549-59
references.pmid: 17110930
references.citation: Cell Res. 2005 Jan;15(1):36-42
references.pmid: 15686625
references.citation: Genes Dev. 1999 Oct 1;13(19):2514-26
references.pmid: 10521396
references.citation: Cell. 2008 May 16;133(4):693-703
references.pmid: 18485876
references.citation: J Virol. 2002 May;76(9):4304-11
references.pmid: 11932396
references.citation: Dev Biol. 1991 Dec;148(2):517-28
references.pmid: 1660419
references.citation: Nat Immunol. 2002 Mar;3(3):221-7
references.pmid: 11875461
references.citation: Pflugers Arch. 2004 Feb;447(5):647-52
references.pmid: 12759754
references.citation: Cell. 2003 Jul 25;114(2):181-90
references.pmid: 12887920
references.citation: PLoS One. 2010 Feb 10;5(2):e9148
references.pmid: 20161774
references.citation: Dev Cell. 2006 Mar;10(3):277-8
references.pmid: 16516830
references.citation: Nature. 2001 Nov 15;414(6861):308-13
references.pmid: 11713530
references.citation: Science. 2000 Mar 10;287(5459):1828-30
references.pmid: 10710311
references.citation: J Physiol. 2009 Feb 1;587(3):521-9
references.pmid: 19047208
references.citation: Proc Natl Acad Sci U S A. 2010 Feb 16;107(7):2890-5
references.pmid: 20133652
references.citation: Cell. 2004 Feb 20;116(4):491-7
references.pmid: 14980217
references.citation: Cell. 2005 Mar 11;120(5):649-61
references.pmid: 15766528
references.citation: Mol Cell. 2006 Mar 3;21(5):701-10
references.pmid: 16507367
references.citation: J Mol Biol. 2004 Jun 25;340(1):39-47
references.pmid: 15184021
references.citation: Mol Carcinog. 2007 Aug;46(8):591-8
references.pmid: 17538955
references.citation: Nature. 2006 May 25;441(7092):431-6
references.pmid: 16724054
references.citation: Mol Cell. 2007 Oct 12;28(1):15-27
references.pmid: 17936701
references.citation: Mol Cell. 2001 Nov;8(5):1005-16
references.pmid: 11741536
references.citation: J Biol Chem. 2006 Jul 14;281(28):19709-19
references.pmid: 16698801
references.citation: Hum Gene Ther. 1998 Nov 20;9(17):2619-27
references.pmid: 9853528
references.citation: Bioessays. 2003 Jan;25(1):17-24
references.pmid: 12508278
references.citation: Am J Physiol Cell Physiol. 2003 Jun;284(6):C1633-44
references.pmid: 12606316
references.citation: Microbiol Mol Biol Rev. 2000 Jun;64(2):354-411
references.pmid: 10839820
references.citation: Blood Cells Mol Dis. 1997 Dec;23(3):422-33
references.pmid: 9454686