Beta-adrenergic receptor trafficking by exercise in rat adipocytes: roles of G-protein-coupled receptor kinase-2, beta-arrestin-2, and the ubiquitin-proteasome pathway.
The effect of exercise on beta-adrenergic receptor (beta-AR) trafficking was investigated in rat adipocytes. The binding sites of a hydrophilic ligand, [(3)H]CGP12177, increased immediately (0 h) and at 3 h after exercise (3 h) but decreased at 24 h after exercise (24 h). The data of immunoblotting revealed that the alterations in the binding sites mainly paralleled the alterations in the beta2-AR proteins in membrane fractions. The protein expressions of both G-protein-coupled receptor kinase (GRK)-2 and beta-arrestin-2 were reduced, with a decline in beta2-AR ubiquitination at 0 h and 3 h. The protein expressions of beta2-AR, GRK-2, beta-arrestin-2, the beta2-AR/beta-arrestin-2 complex, and beta2-AR ubiquitination returned to their respective control levels at 24 h, whereas the beta2-AR mRNA level was reduced. Administration of either lactacystin or propranolol did not alter GRK-2 and beta2-AR protein expressions after exercise. Thus, the mechanism underlying the increased density of beta2-AR up to at least 3 h may involve alterations in a multistep event involving the coordinate interaction among proteins mediating beta2-AR trafficking, in which both the receptor-agonist interactions and ubiquitin-proteasome pathway have a key role. However, the decreased protein expression of beta2-AR at 24 h might be due to some change occurring at the translational levels.
Ogasawara
Junetsu
J
Department of Kinesiology, Graduate School of Science, Tokyo Metropolitan University, Hachioji, Tokyo, Japan.
Sanpei
Minori
M
Rahman
Nazibur
N
Sakurai
Tomonobu
T
Kizaki
Takako
T
Hitomi
Yoshiaki
Y
Ohno
Hideki
H
Izawa
Tetsuya
T
D017667:Adipocytes / Q000378:metabolism*; D000818:Animals; D019390:Arrestins / Q000235:genetics / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D054769:G-Protein-Coupled Receptor Kinase 2; D005786:Gene Expression Regulation; D008297:Male; D010805:Physical Conditioning, Animal / Q000502:physiology*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011943:Receptors, Adrenergic, beta / Q000235:genetics / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism*; D051552:beta-Adrenergic Receptor Kinases / Q000235:genetics / Q000378:metabolism*; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins
C000605257:Arrb2 protein, rat; D019390:Arrestins; D012333:RNA, Messenger; D011943:Receptors, Adrenergic, beta; D025801:Ubiquitin; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins; D000242:Cyclic AMP; C496569:Grk2 protein, rat; D051552:beta-Adrenergic Receptor Kinases; D054769:G-Protein-Coupled Receptor Kinase 2; D046988:Proteasome Endopeptidase Complex