All cellular signaling pathways currently known to elevate cGMP involve the activation of a guanylyl cyclase to synthesize cGMP. Here we describe an exception to this rule. In the vertebrate parietal eye, the photoreceptors depolarize to light under dark-adapted conditions, unlike rods and cones but like most invertebrate photoreceptors. We report that the signaling pathway for this response involves a rise in intracellular cGMP resulting from an inhibition of the phosphodiesterase that hydrolyzes cGMP. Furthermore, this phosphodiesterase is driven by an active G protein in darkness. These results indicate an antagonistic control of the phosphodiesterase by two G proteins, analogous to the GS/Gi control of adenylyl cyclase. Our findings demonstrate an unusual phototrans-duction mechanism and at the same time indicate that signaling involving cyclic nucleotides is more elaborate than previously known.
|Original language||English (US)|
|Number of pages||7|
|State||Published - 1998|
ASJC Scopus subject areas
- Molecular Biology