The small GTP-binding protein RhoA regulates serotonin-induced Na+-current response in the neurons of Aplysia.
Application of serotonin (5-HT) induces a slow inward current response in identified neurons of Aplysia ganglia under voltage clamp. The 5-HT-induced current response was depressed in Na+-free media, but augmented in Ca2+-free media, and unaffected by a change in external K+. The 5-HT-induced response was markedly blocked by intracellular injection of guanosine 5'-O-(2-thiodiphosphate) (GDPbetaS). After the injection of guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS), the responses to 5-HT gradually and significantly increased at the initial period, reached its plateau, and finally decreased. Intracellular injection of Clostridium difficile toxin B, a blocker of small G-protein Rho family members such as Rho (RhoA, RhoB and RhoC), Rac and Cdc42, markedly depressed the 5-HT-induced response. Intracellular injection of Clostridium botulinum C3 exoenzyme, a specific blocker of RhoA, RhoB, RhoC, exhibited a similar depressing effect observed with toxin B. In contrast, intracellular injection of recombinant L63RhoA, a constitutively active form of RhoA, significantly augmented the 5-HT-induced response without affecting the resting membrane. These results suggested that the 5-HT-induced Na+-current response might be facilitated by the activation of Aplysia Rho which is closely homologous to RhoA, RhoB or RhoC in mammalian neuron.
Kawasaki
Satoshi
S
Department of Physiology, School of Medicine, Iwate Medical University, Morioka 020-8505, Japan. skawasak@iwate-med.ac.jp
Kimura
Shingo
S
Fujita
Reiko
R
Sasaki
Kazuhiko
K
D036002:ADP Ribose Transferases / Q000494:pharmacology; D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D001048:Aplysia; D001905:Botulinum Toxins / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D004347:Drug Interactions; D017952:Ganglia, Invertebrate / Q000166:cytology; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects* / Q000502:physiology*; D018408:Patch-Clamp Techniques / Q000379:methods; D012701:Serotonin / Q000494:pharmacology*; D012964:Sodium / Q000378:metabolism*; D013873:Thionucleotides / Q000494:pharmacology; D013997:Time Factors; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology; D020830:rac1 GTP-Binding Protein / Q000494:pharmacology; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
D013873:Thionucleotides; D006153:Guanosine Diphosphate; D012701:Serotonin; D005680:gamma-Aminobutyric Acid; C023427:guanosine 5'-O-(2-thiodiphosphate); D012964:Sodium; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D001905:Botulinum Toxins; D020830:rac1 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein; D000109:Acetylcholine; D002118:Calcium