In:
Synapse, Wiley, Vol. 66, No. 9 ( 2012-09), p. 759-769
Abstract:
The mechanism of agonist‐induced GABA B receptor (GABA B R) internalization is not well understood. To investigate this process, we focused on the interaction of GABA B R with β‐arrestins, which are key proteins in the internalization of most of the G protein‐coupled receptors, and the agonist‐induced GABA B R internalization and the interaction of GABA B R with β‐arrestin1 and β‐arrestin2 were investigated in real time using GABA B R and β‐arrestins both of which were fluorescent protein‐tagged. We then compared these profiles with those of μ‐opioid receptors (μOR), well‐studied receptors that associate and cointernalize with β‐arrestins. When stimulated by the specific GABA B R agonist baclofen, GABA B R composed of GABA B1a R (GB 1a R) and fluorescent protein‐tagged GABA B2 R‐Venus (GB 2 R‐V) formed functional GABA B R; they elicited G protein‐activated inwardly rectifying potassium channels as well as nontagged GABA B R. In cells coexpressing GB 1a R, GB 2 R‐V, and β‐arrestin1‐Cerulean (βarr1‐C) or β‐arrestin2‐Cerulean (βarr2‐C), real‐time imaging studies showed that baclofen treatment neither internalized GB 2 R‐V nor mobilized βarr1‐C or βarr2‐C to the cell surface. This happened regardless of the presence of G protein‐coupled receptor kinase 4 (GRK4), which forms a complex with GABA B R and causes GABA B R desensitization. On the other hand, in cells coexpressing μOR‐Venus, GRK2, and βarr1‐C or βarr2‐C, the μOR molecule formed μOR/βarr1 or μOR/βarr2 complexes on the cell surface, which were then internalized into the cytoplasm in a time‐dependent manner. Fluorescence resonance energy transfer assay also indicated scarce association of GB 2 R‐V and β‐arrestins‐C with or without the stimulation of baclofen, while robust association of μOR‐V with β‐arrestins‐C was detected after μOR activation. These findings suggest that GABA B Rs failure to undergo agonist‐induced internalization results in part from its failure to interact with β‐arrestins. Synapse 66:759–769, 2012.© 2012 Wiley Periodicals, Inc.
Type of Medium:
Online Resource
ISSN:
0887-4476
,
1098-2396
Language:
English
Publisher:
Wiley
Publication Date:
2012
detail.hit.zdb_id:
1474927-0
SSG:
12
