Desensitization of GABAB receptor signaling by formation of protein complexes of GABAB2 subunit with GRK4 or GRK5
✍ Scribed by Masato Kanaide; Yasuhito Uezono; Masanori Matsumoto; Minoru Hojo; Yuko Ando; Yuka Sudo; Koji Sumikawa; Kohtaro Taniyama
- Book ID
- 102312131
- Publisher
- John Wiley and Sons
- Year
- 2006
- Tongue
- English
- Weight
- 390 KB
- Volume
- 210
- Category
- Article
- ISSN
- 0021-9541
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✦ Synopsis
Abstract
We investigated the role of G protein coupled‐receptor kinases (GRKs) in the desensitization of GABA~B~ receptor‐mediated signaling using Xenopus oocytes and baby hamster kidney (BHK) cells. Baclofen elicited inward K^+^ currents in oocytes coexpressing heterodimeric GABA~B~ receptor, GABA~B1a~ subunit (GB~1a~R) and GABA~B2~ subunit (GB~2~R), together with G protein‐activated inwardly rectifying K^+^ channels (GIRKs), in a concentration‐dependent manner. Repetitive application of baclofen to oocytes coexpressing GABA~B~R and GIRKs did not change peak K^+^ currents in the first and second responses, but the latter responses were significantly attenuated by coexpression of either GRK4 or GRK5 with attenuation efficacy of GRK4 > GRK5. Coexpression of other GRKs including GRK2, GRK3, and GRK6 had no effect on GABA~B~ receptor‐mediated desensitization processes. In BHK cells coexpressing GRK4 fused to Venus (brighter variant of yellow fluorescent protein, GRK4‐Venus) with GB~1a~R and GB~2~R, GRK4‐Venus was expressed in the cytosol but was translocated to the plasma membranes by GABA~B~R activation. In BHK cells coexpressing GRK4 fused to Cerulean (brighter variant of cyan fluorescent protein, GRK4‐Cerulean) with GB~1a~R and GB~2~R‐Venus, fluorescence resonance energy transfer (FRET) analysis demonstrated that GRK4‐Cerulean formed a protein complex with GB~2~R‐Venus. Immunoprecipitation and Western blot analysis confirmed GB~2~R‐GRK4 complex formation. GRK5 also formed a complex with GB~2~R on the plasma membranes as determined by FRET and Western blotting but not GRK2, GRK3, and GRK6. Our results indicate that GRK4 and GRK5 desensitize GABA~B~ receptor‐mediated responses by forming protein complexes with GB~2~R subunit of GABA~B~R at the plasma membranes. J. Cell. Physiol. 210: 237–245, 2007. © 2006 Wiley‐Liss, Inc.