hSK4/hIK1, a calmodulin-binding KCa channel in human T lymphocytes -: Roles in proliferation and volume regulation
hSK4/hIK1, a calmodulin-binding KCa channel in human T lymphocytes -: Roles in proliferation and volume regulation
复制标题
DOI：
10.1074/jbc.274.21.14838
复制
发表时间：
1999-05-21
影响因子：
4.8
通讯作者：
Schlichter, LC
中科院分区：
文献类型：
--
作者：
Khanna, R;Chang, MC;Schlichter, LC
人T淋巴细胞表达Ca 2+激活的K+电流（IK），其作用和调节知之甚少。我们从人T淋巴母细胞中扩增了hSK 4 cDNA，并且我们表明，当在中国仓鼠卵巢细胞中稳定表达时，其生物物理学和药理学性质与天然IK电流基本相同。在活化的淋巴母细胞中，hSK 4 mRNA增加14.6倍（Kv1.3 mRNA增加1.3倍），具有功能性后果。当Kv1.3和IK在幼稚T细胞中被阻断时，增殖被抑制，但单独的IK阻断抑制再刺激的淋巴母细胞。IK和Kv1.3参与容量调节，但IK更重要，特别是在淋巴母细胞中。hSK 4缺乏已知的钙离子结合位点，然而，我们映射了一个钙离子依赖性钙调蛋白（CaM）结合位点的近端C末端（Ct 1）的hSK 4。全长hSK 4在中国仓鼠卵巢细胞中产生高度负的膜电位（V-m），而当Ctl或远端C末端缺失时，通道不起作用（V-m类似于0 mV）。天然IK（但不表达hSK 4）电流抑制钙调素和钙调素激酶拮抗剂在生理V-M值，表明调制的辅助分子在天然细胞。我们的研究结果为IK/hSK 4在活化T细胞功能中的作用增加提供了证据;因此，hSK 4可能是涉及继发性免疫应答的疾病的有希望的治疗靶点。
Human T lymphocytes express a Ca2+-activated K+ current (IK), whose roles and regulation are poorly understood. We amplified hSK4 cDNA hom human T lymphoblasts, and we showed that its biophysical and pharmacological properties when stably expressed in Chinese hamster ovary cells were essentially identical to the native IK current. In activated lymphoblasts, hSK4 mRNA increased 14.6-fold (Kv1.3 mRNA increased 1.3-fold), with functional consequences. Proliferation was inhibited when Kv1.3 and IK were blocked in naive T cells, but IK block alone inhibited re-stimulated lymphoblasts. IK and Kv1.3 were involved in volume regulation, but IK was more important, particularly in lymphoblasts. hSK4 lacks known Ca2+-binding sites; however, we mapped a Ca2+-dependent calmodulin (CaM)-binding site to the proximal C terminus (Ct1) of hSK4. Full-length hSK4 produced a highly negative membrane potential (V-m) in Chinese hamster ovary cells, whereas the channels did not function when either Ctl or the distal C terminus was deleted (V-m similar to 0 mV). Native IK (but not expressed hSK4) current was inhibited by CaM and CaM kinase antagonists at physiological V-m values, suggesting modulation by an accessory molecule in native cells. Our results provide evidence for increased roles for IK/hSK4 in activated T cell functions; thus hSK4 may be a promising therapeutic target for disorders involving the secondary immune response.