National Heart and Lung Institute (Z.K., S.M., A.L., K.S.A., J.C., I.K., J.F., J.L.S.-A., C.A.M., P.S., B.W.-S., P.T.W., J.G.), Imperial College London, United Kingdom.
Department of Chemistry (Z.K., B.P.N., A.P.I., J.B.E.), Imperial College London, United Kingdom.
Circ Res. 2023 Nov 10;133(11):944-958. doi: 10.1161/CIRCRESAHA.123.323174. Epub 2023 Oct 23.
βAR (beta-1 adrenergic receptor) and βAR (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.
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.
βAR and βAR mRNAs show differential localization in cardiomyocytes, with βAR found in the perinuclear region and βAR showing diffuse distribution throughout the cell. Disruption of microtubules induces a shift of βAR transcripts toward the perinuclear region. The close proximity between βAR transcripts and translated proteins suggests that the translation process occurs in specialized, precisely defined cellular compartments. Redistribution of βAR transcripts is microtubule-dependent, as microtubule depolymerization markedly reduces the number of functional receptors on the membrane. In failing hearts, both βAR and βAR 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 βAR function in failing hearts.
Asymmetrical microtubule-dependent trafficking dictates differential βAR and βAR 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 βAR-mediated cyclic adenosine monophosphate signaling.
βAR（β-1 肾上腺素能受体）和βAR（β-2 肾上腺素能受体）介导的环磷酸腺苷信号转导对心脏功能和心力衰竭进展有不同的影响。然而，调节心脏β-AR 空间定位和功能区室化的机制仍不清楚。新出现的证据表明，mRNA（信使核糖核酸）的微管依赖性运输和局部蛋白质翻译调节了心肌细胞中的蛋白质区室化。我们假设心肌细胞中的β-AR 区室化是通过其 mRNA 的选择性运输和局部翻译来实现的。
使用单分子荧光原位杂交和大鼠心肌细胞的亚细胞纳米活检研究β-AR mRNA 的定位模式。使用长春花碱研究微管对β-AR mRNA 定位的作用，并通过免疫荧光和高通量Förster 共振能量转移显微镜评估其对受体定位和功能的影响。mRNA 蛋白共检测分析鉴定了心肌细胞中可能的β-AR 翻译位点。通过单分子荧光原位杂交、纳米活检和高通量Förster 共振能量转移显微镜，在心肌梗死后 16 周和去微管化的心肌细胞中，阐明了心力衰竭后β-AR mRNA 再分布的机制。
βAR 和βAR mRNA 在心肌细胞中表现出不同的定位，βAR 位于核周区，βAR 则在整个细胞中呈弥散分布。微管的破坏诱导βAR 转录本向核周区转移。βAR 转录本与翻译蛋白的紧密接近表明，翻译过程发生在专门的、精确定义的细胞区室中。βAR 转录本的再分布依赖于微管，因为微管解聚会显著减少膜上功能性受体的数量。在衰竭的心脏中，βAR 和βAR mRNA 都向细胞外周重新分布，这与药物诱导的去微管化的心肌细胞中所见相似。这表明 T 管重塑有助于β-AR mRNA 的重新分布和衰竭心脏中βAR 功能受损。
不对称的微管依赖性运输决定了健康心肌细胞微管中βAR 和βAR 的不同定位，为 2 种β-AR 在质膜上的独特区室化奠定了基础。心肌梗死后，由于横管重塑，定位模式发生改变，导致βAR 介导的环磷酸腺苷信号转导扭曲。
