Abstract
The three α2-adrenergic receptor subtypes (α2a, α2b, and α2c) are highly homologous G protein-coupled receptors. These receptors all couple to pertussis toxin-sensitive G proteins and have relatively similar pharmacological properties. To further explore functional differences between these receptors, we used immunocytochemical techniques to compare the ability of the three α2-receptor subtypes to undergo agonist-mediated internalization. The α2a-receptor does not internalize after agonist treatment. In contrast, we observed that the α2b-receptor is able to undergo agonist-induced internalization and seems to follow the same endosomal pathway used by the β2-adrenergic receptor. Attempts to examine internalization of the α2c-receptor were complicated by the fact that the majority of the α2c-receptor resides in the endoplasmic reticulum and cis/medial Golgi and there is relatively little cell surface localization. Nevertheless, we were able to detect some internalization of the α2c-receptor after prolonged agonist treatment. However, we observed no significant movement of α2c-receptor from the intracellular pool to the plasma membrane during a 4-hr treatment of cells with cycloheximide, suggesting that these cells are unable to process α2c-receptors in the same way they process the α2a or α2b subtypes.
Footnotes
- Received October 28, 1996.
- Accepted February 10, 1997.
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Send reprint requests to: Dr. Brian K. Kobilka, B159 Beckman Center, Stanford University, Stanford, CA 94305. E-mail:kobilka{at}cmgm.stanford.edu
- The American Society for Pharmacology and Experimental Therapeutics
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