ADP-ribose gating of the calcium-permeable LTRPC2 channel revealed by Nudix motif homology

Abstract

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.

Involvement of P2X receptors in the NAD+-induced rise in [Ca2+]i in human monocytes

“…cADPR, NAADP, and ADPR are involved in the regulation of cellular Ca 2+ homeostasis. While cADPR and NAADP trigger Ca 2+ -release from intracellular stores [5][6][7], ADPR controls calcium entry through the plasma membrane channel TRPM2 [8,9]. It is difficult to envision how cADPR and NAADP can function inside the cell if they are generated by ectoenzymes.…”

Selective inhibition of TRPM2 channel by two novel synthesized ADPR analogues

“…In HEK293 cells, the expression of TRPM2 channel proteins was detected by Western blot analysis (Figure 4a). It is known that TRPM2 is only activated by intracellular ADPR that binds directly to TRPM2 channel's enzymatic NUDT9‐H domain in the C‐terminal tail 6. We tested whether extracellular administration of individual ADPR analogues had any effect on TRPM2 currents (Table S1).…”

“…It functions as an important Ca 2+ signalling regulator in a variety of cells, contributing to cellular functions including cytokine production, insulin release, cell motility, oxidative stress and cell death 5. TRPM2 is activated by reactive oxygen species (ROS) such as hydrogen peroxide and is considered as a chanzyme containing a unique C‐terminal Nudix hydrolase domain, that is homologous to the ADPR pyrophosphatase nudix hydrolase 9 (NUDT9) 6, 7, 8. The NUDT9‐homology (NUDT9‐H) domain serves a binding site for channel activation by adenosine 5′‐diphosphoribose (ADPR) 6.…”

“…TRPM2 is activated by reactive oxygen species (ROS) such as hydrogen peroxide and is considered as a chanzyme containing a unique C‐terminal Nudix hydrolase domain, that is homologous to the ADPR pyrophosphatase nudix hydrolase 9 (NUDT9) 6, 7, 8. The NUDT9‐homology (NUDT9‐H) domain serves a binding site for channel activation by adenosine 5′‐diphosphoribose (ADPR) 6. Accumulating evidence shows that TRPM2 channel plays a critical role in sensing internal body temperature9, 10, 11 and is also implicated in many pathological processes such as neurodegeneration,12, 13 diabetes14, 15 and ischemic reperfusion injury,16, 17 suggesting TRPM2 as a potential therapeutic target.…”

Do Hv1 proton channels regulate the ionic and redox homeostasis of phagosomes?

“…Human neutrophils have been shown to express a plethora of receptor-mediated, store-operated, and non-store operated calcium channels (Nunes and Demaurex, 2010;Demaurex et al, 1994;Heiner et al, 2003). TRPM2 channels, members of the transient receptor potential melastatin subfamily of ion channels, have been detected both on the plasma membrane (Perraud et al, 2001) and in lysosomes (Lange et al, 2009) of neutrophils and shown to enhance granule fusion and bactericidal activity (Hong et al, 2010). TRPM2 channels can be activated by ROS (Perraud et al, 2005) and play a key role in aggravating inflammatory processes by increasing the sensitivity to cell death (Yamamoto et al, 2008;Hara et al, 2002).…”