Modulation by PKA of the hyperpolarization-activated current (Ih) in cultured rat olfactory receptor neurons.
The hyperpolarization-activated Ih channel is modulated by neurotransmitters acting through the cAMP messenger system. In rat olfactory receptor neurons (ORNs), dopamine, by inhibition of adenylyl cyclase, shifts the voltage of half-maximal activation (V1/2) of Ih to more negative potentials and decreases Ih maximal relative conductance. Whether these effects result from a phosphorylation-dependent mechanism is unclear. Therefore, we used whole-cell patch-clamp recording techniques to study cAMP-dependent phosphorylation via PKA on Ih in rat ORNs. General protein kinase inhibition (50 nM K252a) produced a hyperpolarizing shift in Ih V1/2 and decreased Ih maximal conductance. Specific inhibition of PKA with H-89 (500 nM) also shifted the V1/2 of Ih to more negative potentials, and, in some cells, decreased Ih maximal conductance. PKA-mediated phosphorylation (cBIMPS, 50 mM) shifted Ih V1/2 more positive, modulated the kinetics of Ih channel activation and increased Ih peak current amplitude. Internal perfusion of the catalytic subunit of PKA (84 nM) also shifted Ih V1/2 positive and this shift was blocked by co-perfusion with PKI (50 nM). These results show that in rat ORNs, the voltage dependence of Ih activation can be modulated by PKA-dependent phosphorylation. We also show that PKA and other protein kinases may be involved in the regulation of Ih maximal conductance. Our findings suggest that changes in the phosphorylation state of ORNs may affect resting properties as well as modulate odor sensitivity.
Vargas
G
G
Department of Physiology, University of Utah, School of Medicine, 410 Chipeta Way, Salt Lake City, UT 84108-1297, USA.
Lucero
M T
MT
D000818:Animals; D002227:Carbazoles / Q000494:pharmacology; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004004:Dichlororibofuranosylbenzimidazole / Q000031:analogs & derivatives* / Q000494:pharmacology; D004553:Electric Conductivity; D066298:In Vitro Techniques; D026121:Indole Alkaloids; D007473:Ion Channels / Q000187:drug effects; D007546:Isoquinolines / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D018034:Olfactory Receptor Neurons / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D051381:Rats; D012016:Reference Values; D013449:Sulfonamides; D013873:Thionucleotides / Q000494:pharmacology
D002227:Carbazoles; D026121:Indole Alkaloids; D007473:Ion Channels; D007546:Isoquinolines; D013449:Sulfonamides; D013873:Thionucleotides; C071644:5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole-3',5'-monophosphorothioate; D004004:Dichlororibofuranosylbenzimidazole; C049985:staurosporine aglycone; D017868:Cyclic AMP-Dependent Protein Kinases; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide