Characteristics of a store-operated calcium-permeable channel - Sarcoendoplasmic reticulum calcium pump function controls channel gating
Characteristics of a store-operated calcium-permeable channel - Sarcoendoplasmic reticulum calcium pump function controls channel gating
复制标题
DOI：
10.1074/jbc.m103283200
复制
发表时间：
2001-08-10
影响因子：
4.8
通讯作者：
Ambudkar, IS
中科院分区：
文献类型：
--
作者：
Liu, XB;Ambudkar, IS
我们研究了储存操作钙通道（SOCC）的单通道特性和调控。在人颌下腺细胞中，carbachol （CCh）诱导闪现通道活性，而thapsigargin （Tg）诱导爆发样活性，其打开概率（NPo）相对较低，平均打开时间较长。在没有Ca2+的情况下，Tg和cch激活的通道可渗透Na+和Ba2+，但不能渗透ntug。这些通道具有相似的Ca2+、Na2+和Ba2+电导，并被2-氨基乙氧基二苯硼酸盐、xestospongin C、Gd3+和La3+抑制。通过(i)添加Tg， （ii）使用Na+代替Ca2+， （iii）使用无Ca2+的浴液，或（iv）用BAPTA-AM缓冲[Ca2+](i)， CCh刺激的闪烁活性改变为爆发样活性。缓冲[Ca2+](i)诱导tg刺激的SOCC的NPo增加2倍。用二价阳离子螯合剂N，N,N ',N ' -四（2-吡啶基甲基）乙二胺（TPEN）减少内质网中的游离[Ca2+]，诱导与CCh + Tg相似的爆发样通道活性。因此，SOCC通过刺激毒碱受体、抑制肌内质Ca2+泵和降低内部储存的[Ca2+]而被激活。重要的是，SOCC的活性取决于[Ca2+](i)和内部存储的游离[Ca2+]。这些新发现表明，SERCA通过(i)重新填充内部Ca2+储存(s)和（ii）减少[Ca2+](i)依赖性抑制，在SOCC的门控中起主要作用。
We examined the single channel properties and regulation of store-operated calcium channels (SOCC). In human submandibular gland cells, carbachol (CCh) induced flickery channel activity while thapsigargin (Tg) induced burst-like activity, with relatively lower open probability (NPo) and longer mean open time. Tg- and CCh-activated channels were permeable to Na+ and Ba2+, but not to NTUDG, in the absence of Ca2+. The channels exhibited similar Ca2+, Na2+, and Ba2+ conductances and were inhibited by 2-aminoethoxydiphenylborate, xestospongin C, Gd3+, and La3+. CCh stimulated flickery activity changed to burst-like activity by (i) addition of Tg, (ii) using Na+ instead of Ca2+, (iii) using Ca2+-free bath solution, or (iv) buffering [Ca2+](i) with BAPTA-AM. Buffering [Ca2+](i) induced a 2-fold increase in NPo of Tg-stimulated SOCC. Reducing free [Ca2+] in the endoplasmic reticulum with the divalent cation chelator, N,N,N ' ,N ' -tetrakis(2-pyridylmethyl)ethylenediamine (TPEN), induced burst-like channel activity similar to that seen with CCh + Tg. Thus, SOCC is activated by stimulation of muscarinic receptors, inhibition of the sarcoendoplasmic Ca2+ pump, and lowering [Ca2+] in the internal store. Importantly, SOCC activity depends on [Ca2+](i) and the free [Ca2+] in the internal store. These novel findings reveal that SERCA plays a major role in the gating of SOCC by (i) refilling the internal Ca2+ store(s) and (ii) decreasing the [Ca2+](i)-dependent inhibition.