Visualization of β-adrenergic receptor dynamics and differential localization in cardiomyocytes
Summary
A key question in receptor signaling is how specificity is realized, particularly when different receptors trigger the same biochemical pathway(s). A notable case is the two β-adrenergic receptor (β-AR) subtypes, β1 and β2, in cardiomyocytes. They are both coupled to stimulatory Gs proteins, mediate an increase in cyclic adenosine monophosphate (cAMP), and stimulate cardiac contractility; however, other effects, such as changes in gene transcription leading to cardiac hypertrophy, are prominent only for β1-AR but not for β2-AR. Here, we employ highly sensitive fluorescence spectroscopy approaches, in combination with a fluorescent β-AR antagonist, to determine the presence and dynamics of the endogenous receptors on the outer plasma membrane as well as on the T-tubular network of intact adult cardiomyocytes. These techniques allow us to visualize that the β2-AR is confined to and diffuses within the T-tubular network, as opposed to the β1-AR, which is found to diffuse both on the outer plasma membrane as well as on the T-tubules. Upon overexpression of the β2-AR, this compartmentalization is lost, and the receptors are also seen on the cell surface. Such receptor segregation depends on the development of the T-tubular network in adult cardiomyocytes since both the cardiomyoblast cell line H9c2 and the cardiomyocyte-differentiated human-induced pluripotent stem cells express the β2-AR on the outer plasma membrane. These data support the notion that specific cell surface targeting of receptor subtypes can be the basis for distinct signaling and functional effects. Copyright © 2021 the Author(s). Published by PNAS.
| Authors | Bathe-Peters M, Gmach P, Boltz HH, Einsiedel J, Gotthardt M, Hübner H, Gmeiner P, Lohse MJ, Annibale P |
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| Journal | Proceedings of the National Academy of Sciences of the United States of America |
| Publication Date | 2021 Jun 8;118(23) |
| PubMed | 34088840 |
| PubMed Central | PMC8201832 |
| DOI | 10.1073/pnas.2101119118 |