title: NAADP mobilizes calcium from acidic organelles through two-pore channels.
abstract: Ca(2+) mobilization from intracellular stores represents an important cell signalling process that is regulated, in mammalian cells, by inositol-1,4,5-trisphosphate (InsP(3)), cyclic ADP ribose and nicotinic acid adenine dinucleotide phosphate (NAADP). InsP(3) and cyclic ADP ribose cause the release of Ca(2+) from sarcoplasmic/endoplasmic reticulum stores by the activation of InsP(3) and ryanodine receptors (InsP(3)Rs and RyRs). In contrast, the nature of the intracellular stores targeted by NAADP and the molecular identity of the NAADP receptors remain controversial, although evidence indicates that NAADP mobilizes Ca(2+) from lysosome-related acidic compartments. Here we show that two-pore channels (TPCs) comprise a family of NAADP receptors, with human TPC1 (also known as TPCN1) and chicken TPC3 (TPCN3) being expressed on endosomal membranes, and human TPC2 (TPCN2) on lysosomal membranes when expressed in HEK293 cells. Membranes enriched with TPC2 show high affinity NAADP binding, and TPC2 underpins NAADP-induced Ca(2+) release from lysosome-related stores that is subsequently amplified by Ca(2+)-induced Ca(2+) release by InsP(3)Rs. Responses to NAADP were abolished by disrupting the lysosomal proton gradient and by ablating TPC2 expression, but were only attenuated by depleting endoplasmic reticulum Ca(2+) stores or by blocking InsP(3)Rs. Thus, TPCs form NAADP receptors that release Ca(2+) from acidic organelles, which can trigger further Ca(2+) signals via sarcoplasmic/endoplasmic reticulum. TPCs therefore provide new insights into the regulation and organization of Ca(2+) signals in animal cells, and will advance our understanding of the physiological role of NAADP.
authors.affiliation: Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, University of Edinburgh, Hugh Robson Building, Edinburgh EH8 9XD, Scotland, UK.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Calcraft
authors.forename: Margarida
authors.initials: M
authors.lastname: Ruas
authors.forename: Zui
authors.initials: Z
authors.lastname: Pan
authors.forename: Xiaotong
authors.initials: X
authors.lastname: Cheng
authors.forename: Abdelilah
authors.initials: A
authors.lastname: Arredouani
authors.forename: Xuemei
authors.initials: X
authors.lastname: Hao
authors.forename: Jisen
authors.initials: J
authors.lastname: Tang
authors.forename: Katja
authors.initials: K
authors.lastname: Rietdorf
authors.forename: Lydia
authors.initials: L
authors.lastname: Teboul
authors.forename: Kai-Ting
authors.initials: KT
authors.lastname: Chuang
authors.forename: Peihui
authors.initials: P
authors.lastname: Lin
authors.forename: Rui
authors.initials: R
authors.lastname: Xiao
authors.forename: Chunbo
authors.initials: C
authors.lastname: Wang
authors.forename: Yingmin
authors.initials: Y
authors.lastname: Zhu
authors.forename: Yakang
authors.initials: Y
authors.lastname: Lin
authors.forename: Christopher N
authors.initials: CN
authors.lastname: Wyatt
authors.forename: John
authors.initials: J
authors.lastname: Parrington
authors.forename: Jianjie
authors.initials: J
authors.lastname: Ma
authors.forename: A Mark
authors.initials: AM
authors.lastname: Evans
authors.forename: Antony
authors.initials: A
authors.lastname: Galione
authors.forename: Michael X
authors.initials: MX
authors.lastname: Zhu
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002460:Cell Line; D002645:Chickens; D006801:Humans; D006863:Hydrogen-Ion Concentration; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D009249:NADP / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D015388:Organelles / Q000187:drug effects / Q000378:metabolism*; D011485:Protein Binding; D000097903:Two-Pore Channels
chemical_list: D002118:Calcium; D015220:Calcium Channels; D009249:NADP; C407357:TPCN1 protein, human; D000097903:Two-Pore Channels; C530224:TPCN2 protein, human; C024376:NAADP