Edited by Louis J. Ignarro, University of California School of Medicine, Los Angeles, CA, and approved November 13, 2003 (received for review August 8, 2003)
Defending cellular integrity against disturbances in intracellular concentrations of ATP ([ATP]i) is predicated on coordinating the selection of substrates and their flux through metabolic pathways (metabolic signaling), ATP transfer from sites of production to utilization (energetic signaling), and the regulation of processes consuming energy (cell signaling). Whereas NO and its receptor, soluble guanylyl cyclase (sGC), are emerging as key mediators coordinating ATP supply and demand, mechanisms coupling this pathway with metabolic and energetic signaling remain undefined. Here, we demonstrate that sGC is a nucleotide sensor whose responsiveness to NO is regulated by [ATP]i. Indeed, ATP inhibits purified sGC with a Ki predicting >60% inhibition of NO signaling in cells maintaining physiological [nucleotide]i. ATP inhibits sGC by interacting with a regulatory site that prefers ATP > GTP. Moreover, alterations in [ATP]i, by permeabilization and nucleotide clamping or inhibition of mitochondrial ATP synthase, regulate NO signaling by sGC. Thus, [ATP]i serves as a “gain control” for NO signaling by sGC. At homeostatic [ATP]i, NO activation of sGC is repressed, whereas insults that reduce [ATP]i, derepress sGC and amplify responses to NO. Hence, sGC forms a key synapse integrating metabolic, energetic, and cell signaling, wherein ATP is the transmitter, allosteric inhibition the coupling mechanism, and regulated accumulation of cGMP the response.
↵‡ To whom correspondence should be addressed. E-mail: scott.waldman{at}jefferson.edu.
This paper was submitted directly (Track II) to the PNAS office.
Abbreviations: [ATP]i, intracellular ATP concentration; [Ca2+]i, intracellular Ca2+ concentration; [cGMP]i, intracellular cGMP concentration; MLC, myosin light chain; GC, guanylyl cyclase; sGC, soluble GC; SNP, sodium nitroprusside.
