Free ADP-ribose (ADPR), a product of NAD hydrolysis and a breakdown product of the calcium-release second messenger cyclic ADPR (cADPR), has no defined role as an intracellular signalling molecule in vertebrate systems. Here we show that a 350-amino-acid protein (designated NUDT9) and a homologous domain (NUDT9 homology domain) near the carboxy terminus of the LTRPC2/TrpC7 putative cation channel both function as specific ADPR pyrophosphatases. Whole-cell and single-channel analysis of HEK-293 cells expressing LTRPC2 show that LTRPC2 functions as a calcium-permeable cation channel that is specifically gated by free ADPR. The expression of native LTRPC2 transcripts is detectable in many tissues including the U937 monocyte cell line, in which ADPR induces large cation currents (designated IADPR) that closely match those mediated by recombinant LTRPC2. These results indicate that intracellular ADPR regulates calcium entry into cells that express LTRPC2.
Pubmed ID: 11385575 RIS Download
Mesh terms: Adenosine Diphosphate Ribose | Amino Acid Motifs | Amino Acid Sequence | Animals | Calcium | Calcium Channels | Cell Line | Cloning, Molecular | Escherichia coli | Humans | Ion Channel Gating | Ion Channels | Membrane Proteins | Molecular Sequence Data | Pyrophosphatases | Recombinant Proteins | Sequence Homology, Amino Acid | Sodium | TRPC Cation Channels | TRPM Cation Channels | U937 Cells
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