Microtubule-Mediated Regulation of β
2
AR Translation and Function in Failing Hearts
Authors: Kwan Zoe , Paulose Nadappuram Binoy , Leung Manton M. , Mohagaonkar Sanika , Li Ao , Amaradasa Kumuthu S. , Chen Ji , Rothery Stephen , Kibreab Iyobel , Fu Jiarong , Sanchez-Alonso Jose L. , Mansfield Catherine A. , Subramanian Hariharan , Kondrashov Alexander , Wright Peter T. , Swiatlowska Pamela , Nikolaev Viacheslav O. , Wojciak-Stothard Beata , Ivanov Aleksandar P. , Edel Joshua B. , Gorelik Julia 
Published: October 2023

Background:

β
1
AR (beta-1 adrenergic receptor) and β
2
AR (beta-2 adrenergic receptor)-mediated cyclic adenosine monophosphate signaling has distinct effects on cardiac function and heart failure progression. However, the mechanism regulating spatial localization and functional compartmentation of cardiac β-ARs remains elusive. Emerging evidence suggests that microtubule-dependent trafficking of mRNP (messenger ribonucleoprotein) and localized protein translation modulates protein compartmentation in cardiomyocytes. We hypothesized that β-AR compartmentation in cardiomyocytes is accomplished by selective trafficking of its mRNAs and localized translation.

Methods:
The localization pattern of β-AR mRNA was investigated using single molecule fluorescence in situ hybridization and subcellular nanobiopsy in rat cardiomyocytes. The role of microtubule on β-AR mRNA localization was studied using vinblastine, and its effect on receptor localization and function was evaluated with immunofluorescent and high-throughput Förster resonance energy transfer microscopy. An mRNA protein co-detection assay identified plausible β-AR translation sites in cardiomyocytes. The mechanism by which β-AR mRNA is redistributed post–heart failure was elucidated by single molecule fluorescence in situ hybridization, nanobiopsy, and high-throughput Förster resonance energy transfer microscopy on 16 weeks post–myocardial infarction and detubulated cardiomyocytes.

Results:

β
1
AR and β
2
AR mRNAs show differential localization in cardiomyocytes, with β
1
AR found in the perinuclear region and β
2
AR showing diffuse distribution throughout the cell. Disruption of microtubules induces a shift of β
2
AR transcripts toward the perinuclear region. The close proximity between β
2
AR transcripts and translated proteins suggests that the translation process occurs in specialized, precisely defined cellular compartments. Redistribution of β
2
AR transcripts is microtubule-dependent, as microtubule depolymerization markedly reduces the number of functional receptors on the membrane. In failing hearts, both β
1
AR and β
2
AR mRNAs are redistributed toward the cell periphery, similar to what is seen in cardiomyocytes undergoing drug-induced detubulation. This suggests that t-tubule remodeling contributes to β-AR mRNA redistribution and impaired β
2
AR function in failing hearts.

Conclusions:

Asymmetrical microtubule-dependent trafficking dictates differential β
1
AR and β
2
AR localization in healthy cardiomyocyte microtubules, underlying the distinctive compartmentation of the 2 β-ARs on the plasma membrane. The localization pattern is altered post–myocardial infarction, resulting from transverse tubule remodeling, leading to distorted β
2
AR-mediated cyclic adenosine monophosphate signaling.