北京大學(xué)生命科學(xué)學(xué)院王世強教授領(lǐng)導(dǎo)的實驗室與北京大學(xué)第三醫(yī)院張幼怡研究員領(lǐng)導(dǎo)的實驗室通力合作,，利用心衰動物模型開展了心衰早期發(fā)病的分子病理機制研究,，業(yè)已取得重要科研成果,。1月9日，有較高學(xué)術(shù)影響的國際期刊《PloSBiology》發(fā)表了他們的研究論文,。  
    據(jù)介紹,，心衰是威脅人類生命的重大疾病之一，患者最終因心肌收縮能力不足而死亡,。心衰往往由心肌肥厚演變而來,，因此闡明心肌肥厚到心衰的演變規(guī)律對防治心衰有重要意義。
    王世強教授和張幼怡研究員的協(xié)作組為了探索這一演變的分子機制,，對控制心肌興奮收縮耦聯(lián)的鈣信號轉(zhuǎn)導(dǎo)過程進行了細(xì)胞和亞細(xì)胞水平的功能鑒定,，并從分子間相互作用的角度系統(tǒng)研究了細(xì)胞膜鈣離子通道與肌質(zhì)網(wǎng)Ryanodine受體相互耦聯(lián)的分子動力學(xué)過程，首次發(fā)現(xiàn)兩分子的耦聯(lián)效率在心肌肥厚發(fā)生早期,、細(xì)胞收縮功能尚無變化的時候就已經(jīng)發(fā)生了衰退,。衰退的原因是錨定兩分子所在膜結(jié)構(gòu)的蛋白分子Junctophilin的表達(dá)量下降。Junctophilin的減少使細(xì)胞膜鈣離子通道與肌質(zhì)網(wǎng)Ryanodine受體間耦聯(lián)效率進行性地衰退,，最終導(dǎo)致細(xì)胞整體鈣信號下降和心肌收縮能力的降低,。這一研究為心衰病理發(fā)生提供了重要分子機制。  
     根據(jù)上述發(fā)現(xiàn),，他們還提出了生理功能“穩(wěn)定余量”的概念,，并證明穩(wěn)定余量的存在是細(xì)胞鈣信號等生理系統(tǒng)保持功能穩(wěn)態(tài)的前提；分子耦聯(lián)效率的降低在一定范圍內(nèi)只是在消耗穩(wěn)定余量,，不會引起細(xì)胞整體功能的變化,；當(dāng)穩(wěn)定余量最終被耗竭后，分子耦聯(lián)效率的進行性下降將表現(xiàn)為細(xì)胞鈣信號和心臟收縮功能的不斷惡化,。這一論述闡釋了心衰病理發(fā)生的演變規(guī)律,，并為心衰的早期診斷、防治的必要性和可行性提供了理論依據(jù),。

部分英文原文：

Intermolecular Failure of L-type Ca2+ Channel and Ryanodine Receptor Signaling in Hypertrophy
Ming Xu, Peng Zhou, Shi-Ming Xu, Yin Liu, Xinheng Feng, Shu-Hua Bai, Yan Bai, Xue-Mei Hao, Qide Han, Youyi Zhang*, Shi-Qiang Wang*

1 State Key Lab of Biomembrane and Membrane Biotechnology, Ministry of Education Key Lab of Molecular Cardiovascular Sciences and Institute of Vascular Medicine, Third Hospital, College of Life Sciences, Peking University, Beijing, China

Pressure overload–induced hypertrophy is a key step leading to heart failure. The Ca2+-induced Ca2+ release (CICR) process that governs cardiac contractility is defective in hypertrophy/heart failure, but the molecular mechanisms remain elusive. To examine the intermolecular aspects of CICR during hypertrophy, we utilized loose-patch confocal imaging to visualize the signaling between a single L-type Ca2+ channel (LCC) and ryanodine receptors (RyRs) in aortic stenosis rat models of compensated (CHT) and decompensated (DHT) hypertrophy. We found that the LCC-RyR intermolecular coupling showed a 49% prolongation in coupling latency, a 47% decrease in chance of hit, and a 72% increase in chance of miss in DHT, demonstrating a state of “intermolecular failure.” Unexpectedly, these modifications also occurred robustly in CHT due at least partially to decreased expression of junctophilin, indicating that intermolecular failure occurs prior to cellular manifestations. As a result, cell-wide Ca2+ release, visualized as “Ca2+ spikes,” became desynchronized, which contrasted sharply with unaltered spike integrals and whole-cell Ca2+ transients in CHT. These data suggested that, within a certain limit, termed the “stability margin,” mild intermolecular failure does not damage the cellular integrity of excitation-contraction coupling. Only when the modification steps beyond the stability margin does global failure occur. The discovery of “hidden” intermolecular failure in CHT has important clinical implications.

Introduction
In response to pressure overload, the heart produces an adaptive response in the form of cardiac hypertrophy to maintain adequate cardiac output and tissue perfusion [1–3]. In the early stage of hypertrophy, cardiac contractile dysfunction is not present, and the ventricle is hemodynamically compensated. When the pressure stimuli are persistent, the heart usually undergoes functional deterioration, eventually leading to heart failure [3,4]. In the failure stage, the heart becomes incapable of generating sufficient pumping power. To prevent the pathogenesis of heart failure, one strategy has been to stop or postpone the transition of hypertrophy from the compensated stage toward the decompensated stage [4]. Therefore, understanding the cellular and molecular mechanisms involved in cardiac hypertrophy is important for developing clinical therapies against heart failure.

At the cellular level, the contractile power during excitation-contraction coupling (E-C coupling) is governed by a mechanism known as Ca2+-induced Ca2+ release (CICR) [5,6]. In this process, Ca2+ influx through L-type Ca2+ channels (LCCs) on the cell surface membrane (including T-tubules) activates ryanodine receptor (RyR) Ca2+ release from the sarcoplasmic reticulum (SR) to generate cell-wide Ca2+ transients [7–9]. Besides LCCs and RyRs, Ca2+ cycling proteins, e.g., SR Ca2+ pumps (SERCA), Na+-Ca2+ exchangers, and their regulatory mechanisms, are also important in determining the amplitude and kinetics of Ca2+ transients [8]. All these mechanisms have been studied in a wide variety of hypertrophy and heart failure models [8,10–14]. Most studies support the idea that the LCC activity does not change much during hypertrophy and heart failure [11]. However, the Ca2+ transients triggered by comparable LCC currents are decreased in amplitude and/or slowed in kinetics in most models of decompensated hypertrophy (DHT) and heart failure [11,13]. These studies lead to the notion that the Ca2+ influx through LCCs becomes less effective in triggering RyR Ca2+ release [13]. Yet the molecular details underlying defective E-C coupling remain unknown. On the other hand, studies on compensated hypertrophy (CHT), a stage prior to DHT, show that the cellular aspects of E-C coupling still appear to be normal or even slightly enhanced [15]. It is thus intriguing to know whether and when the intermolecular process of CICR is modified and how the modification eventually leads to cellular failure in E-C coupling.

During past years, we have developed a local Ca2+ imaging protocol in conjunction with a loose-seal patch clamp technique to investigate LCC-RyR intermolecular coupling [9,16]. In the present study, we utilized this technique and an aortic stenosis model to test the hypothesis that the intermolecular coupling between an LCC and RyRs undergoes a progressive modification during the development of hypertrophy. Our results showed that hypertrophy resulted in an increase in LCC-RyR coupling latency and a decrease in intermolecular signaling efficiency, which started at the early, compensated stage when cellular E-C coupling appeared normal. Our findings provided intermolecular insights into the remodeling of Ca2+ signaling during the pathogenesis leading to heart failure.

Results
To elucidate the microscopic modification of E-C coupling during hypertrophy, we created pressure-overload hypertrophy models induced by aortic stenosis [17]. About 7–11 wk after aorta banding, hemodynamic and echocardiographic measurements identified the status of CHT by increased left ventricle (LV) wall thickness and normal contractile indices, and the status of DHT by the onset of mild depression of contractile indices in addition to thickened LV walls (Figure 1A, 1B, and 1C; Table S1). To characterize the cellular aspects of E-C coupling, we combined a whole-cell patch clamp technique and confocal line-scan imaging to record simultaneously LCC Ca2+ current (ICa) and intracellular Ca2+ transients when the cell membrane was depolarized to 0 mV (Figure 1D). Cell capacitance (Figure S1A) and contraction (Figure S1B) were also measured. In DHT, despite the unchanged ICa density and kinetics (Figure 1E and Figure S1C and S1D), both the amplitude of Ca2+ transients and cell contraction decreased significantly (Figure 1F and Figure S1B). As a result, the gain of E-C coupling was significantly lower than that of the control (Figure 1G). By contrast, neither the amplitude of Ca2+ transients nor the gain of E-C coupling was altered in CHT, indicating that the hypertrophy-associated E-C coupling deficiency occurs only in the late, decompensated stage, but not in the early, compensated stage.

更多原文鏈接：

http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.0050021