title: Caged compounds of hydrolysis-resistant analogues of cAMP and cGMP: synthesis and application to cyclic nucleotide-gated channels.
abstract: Photolabile compounds which rapidly release cAMP or cGMP after photolysis are widely used for in situ studies of signaling pathways inside cells. We synthesized two novel caged compounds, 4,5-dimethoxy-2-nitrobenzyl 8-Br-cAMP (caged 8-Br-cAMP) and 4,5-dimethoxy-2-nitrobenzyl 8-Br-cGMP caged 8-BR-cGMP), which respectively release the hydrolysis-resistant analogues 8-Br-cAMP and 8-Br-cGMP. Their usefulness for physiological studies was examined in a mammalian cell line expressing the cyclic nucleotide-gated (CNG) ion channel of bovine olfactory sensory neurons. The synthesis procedure resulted in diastereomeric mixtures which were chromatographically separated into the axial and equatorial isomers of caged 8-BR-cAMP and of caged 8-BR-cGMP. The axial isomers which have a higher solubility and better solvolytic stability than the equatorial forms were used for experiments with CNG channels. Flashes of UV light produced steps in the concentration of 8-Br-cGMP which activated currents through CNG channels. Concentration steps inside the cell could be calibrated precisely using the relation between the ligand concentration and the normalized current. Similar results were obtained with caged 8-Br-cAMP. Control experiments with caged cGMP showed that flash-induced currents decayed within a few minutes because photoreleased cGMP was degraded by endogenous phosphodiesterase activity. The rise time of the 8-Br-cGMP-activated whole-cell current was consistent with a bimolecular reaction between channel and ligand.
authors.affiliation: Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany.
authors.forename: V
authors.initials: V
authors.lastname: Hagen
authors.forename: C
authors.initials: C
authors.lastname: Dzeja
authors.forename: S
authors.initials: S
authors.lastname: Frings
authors.forename: J
authors.initials: J
authors.lastname: Bendig
authors.forename: E
authors.initials: E
authors.lastname: Krause
authors.forename: U B
authors.initials: UB
authors.lastname: Kaupp
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000031:analogs & derivatives / Q000494:pharmacology*; D000818:Animals; D002417:Cattle; D002460:Cell Line; D000242:Cyclic AMP / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D007202:Indicators and Reagents; D015640:Ion Channel Gating; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology; D007668:Kidney; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D009475:Neurons, Afferent / Q000502:physiology*; D009833:Olfactory Pathways / Q000502:physiology; D010782:Photolysis; D015398:Signal Transduction; D013053:Spectrophotometry; D013237:Stereoisomerism; D014466:Ultraviolet Rays
chemical_list: D007202:Indicators and Reagents; D007473:Ion Channels; C099977:4,5-dimethoxy-2-nitrobenzyl-8-bromo-cAMP; C099978:4,5-dimethoxy-2-nitrobenzyl-8-bromo-cGMP; D015124:8-Bromo Cyclic Adenosine Monophosphate; C016276:8-bromocyclic GMP; D000242:Cyclic AMP; D006152:Cyclic GMP; D015056:1-Methyl-3-isobutylxanthine