Histidine-rich Ca-binding protein interacts with sarcoplasmic reticulum Ca-ATPase
Histidine-rich Ca-binding protein interacts with sarcoplasmic reticulum Ca-ATPase
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DOI：
10.1152/ajpheart.00278.2007
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发表时间：
2007-09-01
影响因子：
4.8
通讯作者：
Kranias, Evangelia G.
中科院分区：
文献类型：
--
作者：
Arvanitis, Demetrios A.;Vafiadaki, Elizabeth;Kranias, Evangelia G.
肌浆网（SR）抑制心脏Ca循环与收缩力减弱相关，可进展为心力衰竭。富含组氨酸的钙结合蛋白（HRC）是一种SR组分，与三聚体结合，并可能通过兰尼碱受体影响钙释放。转基因小鼠心脏中HRC过表达与SR Ca摄取率降低和舒张延迟相关，随着年龄的增长，SR Ca摄取率降低和舒张延迟进展为肥大。目前的研究表明，HRC可能介导其直接结合到心肌中的肌（内）浆网Ca-ATP酶2型（SERCA 2）的调节作用的一部分，这是通过共聚焦显微镜下观察到的共免疫染色证实。这种相互作用涉及HRC的富含组氨酸和谷氨酸的结构域（320-460 aa）和SERCA 2的NH 2-末端阳离子转运蛋白结构域的一部分（74-90 aa），其突出到SR腔中。SERCA 2结合结构域位于人HRC中三聚氰胺结合区的上游（609-699 aa）。HRC和SERCA之间的特异性结合进行了验证，通过免疫共沉淀和下拉分析，使用人类和小鼠的心脏匀浆，并通过印迹覆盖使用谷胱甘肽S-转移酶和麦芽糖结合蛋白重组蛋白。重要的是，钙浓度的增加与HRC与SERCA 2结合的显著减少相关，而它们对心脏匀浆中HRC-三聚体相互作用具有相反的影响。总的来说，我们的数据表明，HRC可能发挥了关键作用，通过其与SERCA 2和三聚体的直接相互作用，调节SR钙循环，介导了一个很好的串扰之间的SR钙摄取和释放的心脏。
Depressed cardiac Ca cycling by the sarcoplasmic reticulum (SR) has been associated with attenuated contractility, which can progress to heart failure. The histidine-rich Ca-binding protein (HRC) is an SR component that binds to triadin and may affect Ca release through the ryanodine receptor. HRC overexpression in transgenic mouse hearts was associated with decreased rates of SR Ca uptake and delayed relaxation, which progressed to hypertrophy with aging. The present study shows that HRC may mediate part of its regulatory effects by binding directly to sarco(endo) plasmic reticulum Ca-ATPase type 2 (SERCA2) in cardiac muscle, which is confirmed by coimmunostaining observed under confocal microscopy. This interaction involves the histidine- and glutamic acid-rich domain of HRC (320-460 aa) and the part of the NH2-terminal cation transporter domain of SERCA2 (74-90 aa) that projects into the SR lumen. The SERCA2-binding domain is upstream from the triadin-binding region in human HRC (609-699 aa). Specific binding between HRC and SERCA was verified by coimmunoprecipitation and pull-down assays using human and mouse cardiac homogenates and by blot overlays using glutathione S-transferase and maltose-binding protein recombinant proteins. Importantly, increases in Ca concentration were associated with a significant reduction of HRC binding to SERCA2, whereas they had opposite effects on the HRC-triadin interaction in cardiac homogenates. Collectively, our data suggest that HRC may play a key role in the regulation of SR Ca cycling through its direct interactions with SERCA2 and triadin, mediating a fine cross talk between SR Ca uptake and release in the heart.