Summary of Research Project Results Under the JSPS FY2000
"Research for the future Program"



1.Research Institution Osaka University
 
2.Research Area Life Science
 
3.Research Field Cellular Signaling
 
4.Term of Project FY1996〜FY2000
 
5.Project Number 96L00302
 
6.Title of Project The Regulation of K+ Channel Activity by G Protein

7.Projetct Leader
Name Institution,Department Title of Position
Yoshihisa, Kurachi Osaka University, Graduate School of Medicine Professor

8.Core Members

Names Institution,Department Title of Position
Atsushi, Inanobe   Osaka University, Graduate School of Medicine AssistantProfessor
Masayuki, Tanemoto Osaka University, Graduate School of Medicine Assistant Professor

9.Cooperating Researchers

Names Institution,Department Title of Position
Kiyoshi, Inageda Osaka University, Graduate School of Medicine Research Associate
Satoru, Fujita Osaka University, Graduate School of Medicine Research Associate

10.Summary of Research Results

In native cardiac myocytes, there is a time-dependence to the G protein-gated inwardly rectifying K+ (KG) channel current during voltage steps which accelerates as the concentration of acetylcholine is increased. This phenomenon has been called 'relaxation' and is not reproduced in the reconstituted Kir3.1/Kir3.4 channel in Xenopus oocytes. We revealed that RGS4, a regulator of G protein signaling, restores relaxation to the reconstituted Kir3.1/Kir3.4 channel (Fujita et al., J. Physiol., 526.2, 587-592, 2000). We further examined the mechanism of this phenomenon by expressing various combinations of membrane receptors, G proteins, Kir3.0 subunits and mutants of RGS4 in Xenopus oocytes (Inanobe et al., J. Physiol., in press). RGS4 restored relaxation to KG channels activated by the pertussis toxin (PTX)-sensitive G protein-coupled m2-muscarinic receptor but not to those activated by the Gs protein-coupled β2-adrenergic receptor. RGS4 induced relaxation not only in heteromeric KG channels composed of Kir3.1 and Kir3.4 but also in homomeric assemblies of either an active mutant of Kir3.1 (Kir3.1/F137S) or an isoform of Kir3.2 (Kir3.2d). Truncation mutants of RGS4 showed that the RGS domain itself was essential to reproduce the effect of wild-type RGS4 on the KG channel. The mutation of residues in the RGS domain which interact with the α subunit of the G protein (Gα) impaired the effect of RGS4.
These results indicates that interaction between the RGS domain and PTX-sensitive Gα subunits mediates the effect of RGS4 on the agonist concentration-dependent relaxation of KG channels.

11.Key Words

(1)Potassium channel、(2)G protein、(3)RGS protein

12.References

[Reference Articles]
Author Title of Article
Hibino, H., et al. Anchoring proteins confer G protein sensitivity to...
Journal Volume Year Pages Concerned
EMBO Journal 19 2000 78-83

Author Title of Article
Matsuoka, T., et al. C-terminal tails of sulfonylurea receptors control...
Journal Volume Year Pages Concerned
Circulation Research 87 2000 873-880

Author Title of Article
Tanemoto, M., et al. In vivo formation of a proton-sensitive K+ channel by...
Journal Volume Year Pages Concerned
Journal of Physiology 525.3 2000 587-592

Author Title of Article
Fujita, S., et al. A regulator of G protein signalling(RGS)protein...
Journal Volume Year Pages Concerned
Journal of Physiology 526.2 2000 341-347

Author Title of Article
Katayama, Y., et al. Inhibitory effects of vesnarinone on cloned cardiac...
Journal Volume Year Pages Concerned
Journal of Pharmacology and Experimental Therapeutics 294 2000 339-346

Author Title of Article
Fujita, A., and Kurachi, Y. Breakthroughs and views SAP family proteins.
Journal Volume Year Pages Concerned
Biochemical and Biophysical Research Communications 269 2000 1-6

Author Title of Article
Shindo, T., et al. MCC-134, a novel vascular relaxing agent, is an...
Journal Volume Year Pages Concerned
Journal of Pharmacology and Experimental Therapeutics 292 2000 131-135

Author Title of Article
Fujita, A., and Kurachi, Y. Molecular aspects of ATP-sensitive K+ channels in...
Journal Volume Year Pages Concerned
Pharmacology & Therapeuties 85 2000 39-53

Author Title of Article
Inanobe, A., and Kurachi, Y. G protein-gated K+ channels.
Journal Volume Year Pages Concerned
Handbook ofExperimental Pharmacology 147 2000 298-331

Author Title of Article
Yokoyama, M., et al. Tertiapin potently and selectively blocks muscarinic...
Journal Volume Year Pages Concerned
Journal of Pharmacology and Experimental Therapeutics 293 2000 196-205

Author Title of Article
Kusaka, S., et al. Functional Kir7.1 channels localized at the root of...
Journal Volume Year Pages Concerned
Journal of Physiology 531.1 2001 27-36

Author Title of Article
Tanemoto, M., et al. Inwardly-rectifying K+ channels in heart.
Journal Volume Year Pages Concerned
Heart Physiology and Pathophysiology   2001 281-308

Author Title of Article
Inanobe, A., et al. Interaction between the RGS domain of RGS4 with...
Journal Volume Year Pages Concerned
Journal of Physiology   2001 in press


back