The α_1D-Adrenergic Receptor Is Expressed Intracellularly and Coupled to Increases in Intracellular Calcium and Reactive Oxygen Species in Human Aortic Smooth Muscle Cells

Authors

Mary L. García-Cazarín, University of KentuckyFollow
Jennifer L. Smith, University of KentuckyFollow
Kyle A. Olszewski, Wilkes University
Dan F. McCune, Wilkes University
Linda A. Simmerman, University of KentuckyFollow
Robert W. Hadley, University of KentuckyFollow
Susan D. Kraner, University of KentuckyFollow
Michael T. Piascik, University of KentuckyFollow

Abstract

Background: The cellular localization of the α_1D-adrenergic receptor (α_1D-AR) is controversial. Studies in heterologous cell systems have shown that this receptor is expressed in intracellular compartments. Other studies show that dimerization with other ARs promotes the cell surface expression of the α_1D-AR. To assess the cellular localization in vascular smooth muscle cells, we developed an adenoviral vector for the efficient expression of a GFP labeled α_1D-AR. We also measured cellular localization with immunocytochemistry. Intracellular calcium levels, measurement of reactive oxygen species and contraction of the rat aorta were used as measures of functional activity.

Results: The adenovirally expressed α_1D-AR was expressed in intracellular compartments in human aortic smooth muscle cells. The intracellular localization of the α_1D-AR was also demonstrated with immunocytochemistry using an α_1D-AR specific antibody. RT-PCR analysis detected mRNA transcripts corresponding to the α_1A-α_1B- and α_1D-ARs in these aortic smooth muscle cells. Therefore, the presence of the other α₁-ARs, and the potential for dimerization with these receptors, does not alter the intracellular expression of the α_1D-AR. Despite the predominant intracellular localization in vascular smooth muscle cells, the α_1D-AR remained signaling competent and mediated the phenylephrine-induced increases in intracellular calcium. The α_1D-AR also was coupled to the generation of reactive oxygen species in smooth muscle cells. There is evidence from heterologous systems that the α_1D-AR heterodimerizes with the β₂-AR and that desensitization of the β₂-AR results in α_1D-AR desensitization. In the rat aorta, desensitization of the β₂-AR had no effect on contractile responses mediated by the α_1D-AR.

Conclusion: Our results suggest that the dimerization of the α_1D-AR with other ARs does not alter the cellular expression or functional response characteristics of the α_1D-AR.

Document Type

Article

Publication Date

2-27-2008

Notes/Citation Information

Published in Journal of Molecular Signaling, v. 3, 6, p. 1-9.

© 2008 García-Cazarín et al; licensee BioMed Central Ltd.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Digital Object Identifier (DOI)

https://doi.org/10.1186/1750-2187-3-6

Funding Information

Funding for Study: HL-38120-14

MTP, MLG, JLS, KAO and DFM: HL-38120-14

SDK: AR46477

RWH and LAS: Natl Heart Lung and Blood Institute: 2 R01 HL056910-5A1

For manuscript: HL-38120-14

Repository Citation

García-Cazarín, Mary L.; Smith, Jennifer L.; Olszewski, Kyle A.; McCune, Dan F.; Simmerman, Linda A.; Hadley, Robert W.; Kraner, Susan D.; and Piascik, Michael T., "The α_1D-Adrenergic Receptor Is Expressed Intracellularly and Coupled to Increases in Intracellular Calcium and Reactive Oxygen Species in Human Aortic Smooth Muscle Cells" (2008). Pharmacology and Nutritional Sciences Faculty Publications. 14.
https://uknowledge.uky.edu/pharmacol_facpub/14