Expression of Ca2+‐permeable two‐pore channels rescues NAADP signalling in TPC‐deficient cells. (14th April 2015)

• Record Type: Journal Article
• Authors: Ruas, Margarida; Davis, Lianne C; Chen, Cheng‐Chang; Morgan, Anthony J; Chuang, Kai‐Ting; Walseth, Timothy F; Grimm, Christian; Garnham, Clive; Powell, Trevor; Platt, Nick; Platt, Frances M; Biel, Martin; Wahl‐Schott, Christian; Parrington, John; Galione, Antony
• Is Part Of: EMBO journal. Volume 34:Number 13(2015)
• Page Start: 1743
• Page End: 1758
• Publication Date: 2015-04-14
• Subjects: Molecular biology -- Periodicals; 572.805
• DOI: 10.15252/embj.201490009
• Languages: English
• ISSNs: 0261-4189

Abstract

<abstract abstract-type="main" id="embj201490009-abs-0001"> <title>Abstract</title> <p>The second messenger NAADP triggers Ca²⁺ release from endo‐lysosomes. Although two‐pore channels (TPCs) have been proposed to be regulated by NAADP, recent studies have challenged this. By generating the first mouse line with demonstrable absence of both <italic>Tpcn1</italic> and <italic>Tpcn2</italic> expression <italic>(Tpcn1/2</italic>^−/−<italic>)</italic>, we show that the loss of endogenous TPCs abolished NAADP‐dependent Ca²⁺ responses as assessed by single‐cell Ca²⁺ imaging or patch‐clamp of single endo‐lysosomes. In contrast, currents stimulated by PI(3, 5)P₂ were only partially dependent on TPCs. In <italic>Tpcn1/2</italic>^−/− cells, NAADP sensitivity was restored by re‐expressing wild‐type TPCs, but not by mutant versions with impaired Ca²⁺‐permeability, nor by TRPML1. Another mouse line formerly reported as TPC‐null likely expresses truncated TPCs, but we now show that these truncated proteins still support NAADP‐induced Ca²⁺ release. High‐affinity [³²P]NAADP binding still occurs in <italic>Tpcn1/2</italic>^−/− tissue, suggesting that NAADP regulation is conferred by an accessory protein. Altogether, our data establish TPCs as Ca²⁺‐permeable channels indispensable for NAADP signalling.</p> </abstract>