Because nitric oxide (NO) is a highly reactive signaling molecule, chemical
inactivation by reaction with oxygen, superoxide, and glutathione competes
with specific interactions with target proteins. NO signaling may be enhan
ced by adaptor proteins that couple neuronal NO synthase (nNOS) to specific
target proteins. Here we identify a selective interaction of the nNOS adap
tor protein CAPON with Dexras1, a brain-enriched member of the Pas family o
f small monomeric G proteins. We find that Dexras1 is activated by NO donor
s as well as by NMDA receptor-stimulated NO synthesis in cortical neurons.
The importance of Dexras1 as a physiologic target of nNOS is established by
the selective decrease of Dexras1 activation, but not H-Ras or four other
Pas family members, in the brains of mice harboring a targeted genomic dele
tion of nNOS (nNOS(-/-)). We also find that nNOS, CAPON, and Dexras1 form a
ternary complex that enhances the ability of nNOS to activate Dexras1. The
se findings identity Dexras1 as a novel physiologic NO effector and suggest
that anchoring of nNOS to specific targets is a mechanism by which NO sign
aling is enhanced.