NADPH analog binding to constitutive nitric oxide activates electron transfer and NO synthesis.
We report here that NADPH analogs such as 2'5'ADP, ATP, and 2'AMP paradoxically activate constitutive calcium/calmodulin regulated nitric oxide synthases (cNOS), including the endothelial isoform (eNOS) and the neuronal isoform (nNOS). These activators compete with NADPH by filling the binding site of the adenine moiety of NADPH, but do not occupy the entire NADPH binding domain. Effects of these analogs on cNOS's include increasing the electron transfer rate to external acceptors, as assessed by cytochrome c reductase activity in the absence of calmodulin. In addition, NO synthase activity in the presence of calmodulin (with or without added calcium) was increased by the addition of NADPH analogs. In contrast, the same NADPH analogs inhibit iNOS, the calcium insensitive inducible isoform, which lacks control elements found in constitutive isoforms. Because ATP and ADP are among the effective activators of cNOS isoforms, these effects may be physiologically relevant.
Jones
Rachel J
RJ
Biology Department, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.
Gao
Ying Tong
YT
Simone
Tessa M
TM
Salerno
John C
JC
Smith
Susan M E
SM
D000244:Adenosine Diphosphate / Q000737:chemistry*; D000249:Adenosine Monophosphate / Q000737:chemistry*; D000255:Adenosine Triphosphate / Q000737:chemistry*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002147:Calmodulin / Q000494:pharmacology; D002417:Cattle; D004579:Electron Transport; D009249:NADP / Q000031:analogs & derivatives*; D009569:Nitric Oxide / Q000096:biosynthesis*; D052248:Nitric Oxide Synthase Type I / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000187:drug effects; D052250:Nitric Oxide Synthase Type III / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000187:drug effects; D017434:Protein Structure, Tertiary; D051381:Rats
D002147:Calmodulin; D009569:Nitric Oxide; D000249:Adenosine Monophosphate; D009249:NADP; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D052248:Nitric Oxide Synthase Type I; D052250:Nitric Oxide Synthase Type III; D002118:Calcium