Translocation of G-Protein β3 subunit from the cytosol pool to the membrane pool by β1-Adrenergic receptor stimulation in perfused rat hearts

1999 ◽  
Vol 58 (9) ◽  
pp. 1497-1500 ◽  
Author(s):  
Ken Kageyama ◽  
Takeshi Murakami ◽  
Kenji Iizuka ◽  
Kumi Sato ◽  
Kazuo Ichihara ◽  
...  
Keyword(s):  
G Protein ◽  
Adrenergic Receptor ◽  
Receptor Stimulation ◽  
Rat Hearts ◽  
Perfused Rat Hearts

Adenosine A3-receptor stimulation attenuates postischemic dysfunction through KATP channels

1999 ◽  
Vol 277 (1) ◽  
pp. H228-H235 ◽  
Author(s):  
Vinod H. Thourani ◽  
Masanori Nakamura ◽  
Russell S. Ronson ◽  
James E. Jordan ◽  
Zhi-Qing Zhao ◽  
...  
Keyword(s):  
Katp Channels ◽  
Left Ventricular ◽  
Rate Of Change ◽  
Control Group ◽  
Receptor Stimulation ◽  
Rat Hearts ◽  
Positive Rate ◽  
Perfused Rat Hearts ◽  
Adenosine Agonists ◽  
Developed Pressure

We tested the hypothesis that selective adenosine A3-receptor stimulation reduces postischemic contractile dysfunction through activation of ATP-sensitive potassium (KATP) channels. Isolated, buffer-perfused rat hearts ( n = 8/group) were not drug pretreated (control) or were pretreated with adenosine (20 μM), 2-chloro- N 6-(3-iodobenzyl)-adenosine-5′- N-methyluronamide (Cl-IB-MECA; A3 agonist, 100 nM), Cl-IB-MECA + 8-(3-noradamantyl)-1,3-dipropylxanthine (KW-3902; A1 antagonist, 5 μM), Cl-IB-MECA + glibenclamide (Glib; KATP-channel blocker, 0.3 μM), or Glib alone for 12 min before 30 min of global normothermic ischemia followed by 2 h of reperfusion. After 2 h of reperfusion, left ventricular developed pressure (LVDP, %baseline) in control hearts was depressed to 34 ± 2%. In hearts pretreated with Cl-IB-MECA, there was a statistically significant increase in LVDP (50 ± 6%), which was reversed with coadministration of Glib (37 ± 1%). Control hearts also showed similar decreases in left ventricular peak positive rate of change in pressure (dP/d t). Therefore, the A3 agonist significantly attenuated postischemic cardiodynamic injury compared with the control, which was reversed by Glib. Cumulative creatine kinase (CK in U/min) activity was most pronounced in the control group (10.4 ± 0.6) and was significantly decreased by Cl-IB-MECA (7.5 ± 0.4), which was reversed by coadministration of Glib (9.4 ± 0.2). Coronary flow was increased during adenosine infusion (160% of baseline) but not during Cl-IB-MECA infusion. Effects of Cl-IB-MECA were not reversed by the specific A1 antagonist KW-3902. We conclude that cardioprotection afforded by A3-receptor stimulation may be mediated in part by KATP channels. Cl-IB-MECA may be an effective pretreatment agent that attenuates postischemic cardiodynamic dysfunction and CK release without the vasodilator liability of other adenosine agonists.

Development of a Novel SNAP-Epitope Tag/Near-Infrared Imaging Assay to Quantify G Protein-Coupled Receptor Degradation in Human Cells

2021 ◽  
pp. 247255522097979
Author(s):  
Kyung-Soon Lee ◽  
Edelmar Navaluna ◽  
Nicole M. Marsh ◽  
Eric M. Janezic ◽  
Chris Hague
Keyword(s):  
G Protein ◽  
Adrenergic Receptor ◽  
Near Infrared ◽  
Human Cells ◽  
Receptor Subtypes ◽  
G Protein Coupled Receptor ◽  
Functional Responses ◽  
Epitope Tag ◽  
Nir Imaging ◽  
G Protein Coupled

We have developed a novel reporter assay that leverages SNAP-epitope tag/near-infrared (NIR) imaging technology to monitor G protein-coupled receptor (GPCR) degradation in human cell lines. N-terminal SNAP-tagged GPCRs were subcloned and expressed in human embryonic kidney (HEK) 293 cells and then subjected to 24 h of cycloheximide (CHX)-chase degradation assays to quantify receptor degradation half-lives ( t1/2) using LICOR NIR imaging–polyacrylamide gel electrophoresis (PAGE) analysis. Thus far, we have used this method to quantify t1/2 for all nine adrenergic (ADRA1A, ADRA1B, ADRA1D, ADRA2A, ADRA2B, ADRA2C, ADRB1, ADRB2, ADRB3), five somatostatin (SSTR1, SSTR2, SSTR3, SSTR4, SSTR5), four chemokine (CXCR1, CXCR2, CXCR3, CXCR5), and three 5-HT2 (5HT2A, 5HT2B, 5HT2C) receptor subtypes. SNAP-GPCR-CHX degradation t1/2 values ranged from 0.52 h (ADRA1D) to 5.5 h (SSTR3). On the contrary, both the SNAP-tag alone and SNAP-tagged and endogenous β-actin were resistant to degradation with CHX treatment. Treatment with the proteasome inhibitor bortezomib produced significant but variable increases in SNAP-GPCR protein expression levels, indicating that SNAP-GPCR degradation primarily occurs through the proteasome. Remarkably, endogenous β2-adrenergic receptor/ADRB2 dynamic mass redistribution functional responses to norepinephrine were significantly decreased following CHX treatment, with a time course equivalent to that observed with the SNAP-ADRB2 degradation assay. We subsequently adapted this assay into a 96-well glass-bottom plate format to facilitate high-throughput GPCR degradation screening. t1/2 values quantified for the α1-adrenergic receptor subtypes (ADRA1A, ADRA1B, ADR1D) using the 96-well-plate format correlated with t1/2 values quantified using NIR-PAGE imaging analysis. In summary, this novel assay permits precise quantitative analysis of GPCR degradation in human cells and can be readily adapted to quantify degradation for any membrane protein of interest.

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