A novel gene, hKCa4, encodes the calcium-activated potassium channel in human T lymphocytes
A novel gene, hKCa4, encodes the calcium-activated potassium channel in human T lymphocytes
复制标题
DOI：
10.1074/jbc.272.52.32723
复制
发表时间：
1997-12-26
影响因子：
4.8
通讯作者：
Aiyar, J
中科院分区：
文献类型：
--
作者：
Logsdon, NJ;Kang, JS;Aiyar, J
我们从人淋巴结文库中分离出一个新基因hKCa4，它编码中等电导的钙激活钾通道，翻译后的蛋白包含427个氨基酸，具有6个跨膜片段S1-S6，以及S5和S6之间的孔基序。 hKCa4 在氨基酸水平上与从大脑克隆的三个小电导钙激活钾通道有 41-42% 的相似性，原代人 T 淋巴细胞的 Northern 印迹分析显示，与静息细胞相比，激活的 2.2 kb 转录物高度上调，伴随着 KCa 电流的增加，hKCa4 转录物也可以通过 Northern 印迹或通过 胎盘、前列腺、胸腺、脾脏、结肠和许多造血来源的细胞系中的聚合酶链反应。 hKCa4 转染的 HEK 293 细胞的膜片钳记录揭示了一个大的电压无关的内向整流钾电流，该电流被外部应用的四乙铵 (K-d = 30 +/- 7 mM)、charybdotoxin (K-d = 10 +/- 1 nM 和克霉唑 (K-d = 387 +/- 34 nM) 阻断，但 对 apamin、iberiotoxin、kaliotoxin、scyllatoxin (K-d > 1 mu M) 和 margatoxin (K-d > 100 nM) 具有抗性。在对称钾溶液中，单个 hKCa4 通道的电导率为 33 +/- 2 皮西。该通道由细胞内钙 (K-d = 270 +/- 8 nM) 激活，并与以下物质高度协作相互作用： 每个通道大约有 3 个钙离子，克隆通道的这些特性与激活的人 T 淋巴细胞中天然 KCa 通道的特性非常相似，表明 hKCa4 编码这种通道类型。
We have isolated a novel gene, hKCa4, encoding an intermediate conductance, calcium-activated potassium channel from a human lymph node library, The translated protein comprises 427 amino acids, has six transmembrane segments, S1-S6, and a pore motif between S5 and S6. hKCa4 shares 41-42% similarity at the amino acid level with three small conductance calcium-activated potassium channels cloned from brain, Northern blot analysis of primary human T lymphocytes reveals a 2.2-kilobase transcript that is highly up-regulated in activated compared with resting cells, concomitant with an increase in KCa current, hKCa4 transcript is also detected by Northern blots or by polymerase chain reaction in placenta, prostate, thymus, spleen, colon, and many cell lines of hematopoietic origin. Patch-clamp recordings of hKCa4-transfected HEK 293 cells reveal a large voltage-independent, inwardly rectifying potassium current that is blocked by externally applied tetraethylammonium (K-d = 30 +/- 7 mM), charybdotoxin (K-d = 10 +/- 1 nM and clotrimazole (K-d = 387 +/- 34 nM), but is resistant to apamin, iberiotoxin, kaliotoxin, scyllatoxin (K-d > 1 mu M), and margatoxin (K-d > 100 nM). Single hKCa4 channels have a conductance of 33 +/- 2 picosiemens in symmetrical potassium solutions. The channel is activated by intracellular calcium (K-d = 270 +/- 8 nM) with a highly cooperative interaction of approximately three calcium ions per channel, These properties of the cloned channel are very similar to those reported for the native KCa channel in activated human T lymphocytes, indicating that hKCa4 encodes this channel type.