HN1L/JPT2: A signaling protein that connects NAADP generation to Ca2+ microdomain formation.

Roggenkamp, Hannes G; Khansahib, Imrankhan; Hernandez C, Lola C; Zhang, Yunpeng; Lodygin, Dmitri; Krüger, Aileen; Gu, Feng; Möckl, Franziska; Löhndorf, Anke; Wolters, Valerie; Woike, Daniel; Rosche, Anette; Bauche, Andreas; Schetelig, Daniel; Werner, René; Schlüter, Hartmut; Failla, Antonio V; Meier, Chris; Fliegert, Ralf; Walseth, Timothy F; Flügel, Alexander; Diercks, Björn-Philipp; Guse, Andreas H

NAADP-evoked Ca2+ release through type 1 ryanodine receptors (RYR1) is a major mechanism underlying the earliest signals in T cell activation, which are the formation of Ca2+ microdomains. In our characterization of the molecular machinery underlying NAADP action, we identified an NAADP-binding protein, called hematological and neurological expressed 1-like protein (HN1L) [also known as Jupiter microtubule-associated homolog 2 (JPT2)]. Gene deletion of Hn1l/Jpt2 in human Jurkat and primary rat T cells resulted in decreased numbers of initial Ca2+ microdomains and delayed the onset and decreased the amplitude of global Ca2+ signaling. Photoaffinity labeling demonstrated direct binding of NAADP to recombinant HN1L/JPT2. T cell receptor/CD3-dependent coprecipitation of HN1L/JPT2 with RYRs and colocalization of these proteins suggest that HN1L/JPT2 connects NAADP formation with the activation of RYR channels within the first seconds of T cell activation. Thus, HN1L/JPT2 enables NAADP to activate Ca2+ release from the endoplasmic reticulum through RYR.