From the Department of Pharmacology, Federal University of São Paulo, São Paulo SP 04044-020, Brazil.
J Biol Chem. 2011 Aug 12;286(32):27875-81. doi: 10.1074/jbc.C110.216580. Epub 2011 May 24.
Nicotinic acid adenine dinucleotide phosphate (NAADP) is a potent Ca(2+)-mobilizing messenger that in many cells releases Ca(2+) from the endolysosomal system. Recent studies have shown that NAADP-induced Ca(2+) mobilization is mediated by the two-pore channels (TPCs). Whether NAADP acts as a messenger in astrocytes is unclear, and downstream functional consequences have yet to be defined. Here, we show that intracellular delivery of NAADP evokes Ca(2+) signals from acidic organelles in rat astrocytes and that these signals are potentiated upon overexpression of TPCs. We also show that NAADP increases acidic vesicular organelle formation and levels of the autophagic markers, LC3II and beclin-1. NAADP-mediated increases in LC3II levels were reduced in cells expressing a dominant-negative TPC2 construct. Our data provide evidence that NAADP-evoked Ca(2+) signals mediated by TPCs regulate autophagy.
烟酰胺腺嘌呤二核苷酸磷酸（NAADP）是一种强效的 Ca(2+)动员信使分子，它可以在许多细胞中从内溶酶体系统中释放 Ca(2+)。最近的研究表明，NAADP 诱导的 Ca(2+)动员是由双孔通道（TPCs）介导的。NAADP 是否在星形胶质细胞中充当信使尚不清楚，其下游功能后果尚未确定。在这里，我们表明，NAADP 的细胞内传递会在大鼠星形胶质细胞的酸性细胞器中引发 Ca(2+)信号，并且在 TPCs 的过表达下，这些信号会增强。我们还表明，NAADP 增加酸性囊泡细胞器的形成和自噬标志物 LC3II 和 beclin-1 的水平。在表达显性负性 TPC2 构建体的细胞中，NAADP 介导的 LC3II 水平增加减少。我们的数据提供了证据表明，TPC 介导的 NAADP 诱导的 Ca(2+)信号调节自噬。
