PKA/AKAP/VR-1 module: A common link of Gs-mediated signaling to thermal hyperalgesia.
Inflammatory mediators not only activate "pain-"sensing neurons, the nociceptors, to trigger acute pain sensations, more important, they increase nociceptor responsiveness to produce inflammatory hyperalgesia. For example, prostaglandins activate G(s)-protein-coupled receptors and initiate cAMP- and protein kinase A (PKA)-mediated processes. We demonstrate for the first time at the cellular level that heat-activated ionic currents were potentiated after exposure to the cAMP activator forskolin in rat nociceptive neurons. The potentiation was prevented in the presence of the selective PKA inhibitor PKI(14-22), suggesting PKA-mediated phosphorylation of the heat transducer protein. PKA regulatory subunits were found in close vicinity to the plasma membrane in these neurons, and PKA catalytic subunits only translocated to the cell periphery when activated. The translocation and the current potentiation were abolished in the presence of an A-kinase anchoring protein (AKAP) inhibitor. Similar current changes after PKA activation were obtained from human embryonic kidney 293t cells transfected with the wild-type heat transducer protein vanilloid receptor 1 (VR-1). The forskolin-induced current potentiation was greatly reduced in cells transfected with VR-1 mutants carrying point mutations at the predicted PKA phosphorylation sites. The heat transducer VR-1 is therefore suggested as the molecular target of PKA phosphorylation, and potentiation of current responses to heat depends on phosphorylation at predicted PKA consensus sites. Thus, the PKA/AKAP/VR-1 module presents as the molecular correlate of G(s)-mediated inflammatory hyperalgesia.
Rathee
Parvinder Kaur
PK
Institute of Physiology, Department of Anaesthesiology, University of Erlangen, D-91054 Erlangen, Germany. ihan@phy.ucsf.edu
Distler
Carsten
C
Obreja
Otilia
O
Neuhuber
Winfried
W
Wang
Ging Kuo
GK
Wang
Sho-Ya
SY
Nau
Carla
C
Kress
Michaela
M
D000818:Animals; D001665:Binding Sites / Q000502:physiology; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000378:metabolism*; D006358:Hot Temperature / Q000009:adverse effects; D006930:Hyperalgesia / Q000378:metabolism*; D017136:Ion Transport / Q000187:drug effects; D007668:Kidney / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009475:Neurons, Afferent / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D011955:Receptors, Drug / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D014162:Transfection
D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D011955:Receptors, Drug; D005576:Colforsin; D017868:Cyclic AMP-Dependent Protein Kinases; D019205:GTP-Binding Protein alpha Subunits, Gs