Ca2+涌入需要KCa3.1離子通道,，進(jìn)而激活T細(xì)胞和B細(xì)胞。弄清KCa3.1的調(diào)節(jié)機(jī)制有助于治療自身免疫性疾病和移植排斥,。先前有研究證實(shí)KCa3.1可被PI(3)P間接激活,。最近,，紐約州立大學(xué)醫(yī)學(xué)院藥理學(xué)系的Shekhar Srivastava及其同事為PI(3)P激活KCa3.1找到了中間體——NDPK-B,。研究結(jié)果刊登于12月8日《Molecular Cell》雜志電子版,。
KCa3.1羧基端的14個(gè)氨基酸殘基是PI(3)P進(jìn)行調(diào)節(jié)的部位。研究人員利用這14個(gè)氨基酸肽段進(jìn)行酵母雙雜交實(shí)驗(yàn),，發(fā)現(xiàn)NDPK-B是相互作用的助手,。轉(zhuǎn)染細(xì)胞的KCa3.1和NDPK-B發(fā)生免疫共沉淀,，T細(xì)胞的內(nèi)源蛋白也發(fā)生免疫共沉淀,。
NDPK-B過表達(dá)，可激活全細(xì)胞KCa3.1通道的活性,；NDPK-B激酶無活性突變體（kinase inactive mutant）或者NDPK-A不能激活KCa3.1用wortmannin消除整個(gè)細(xì)胞的PI(3)P,，導(dǎo)致KCa3.1通道無活性，NDPK-B引起這些細(xì)胞的活性需要補(bǔ)充額外的PI(3)P,。
KCa3.1第358位點(diǎn)的組氨酸殘基,，位于C末端14個(gè)氨基酸序列內(nèi)部，需要PI(3)P調(diào)節(jié),。相關(guān)的KCa2.1,、KCa2.2、KCa2.3通道第358位是天門冬氨酸,，這些通道不需要PI(3)P調(diào)節(jié)（先前研究證實(shí)）,，也不能被NDPK-B激活,。體外實(shí)驗(yàn)中，KCa3.1的C末端可被NDPK-B磷酸化,。His358發(fā)生突變,，NDPK-B不能激活通道，這些突變的通道對(duì)PI(3)P削弱的引起抑制性效果有抵抗性,。
對(duì)有活性的CD4+ T細(xì)胞進(jìn)行mRNA分析,，發(fā)現(xiàn)編碼KCa3.1的基因數(shù)量上升；siRNA下調(diào)NDPK-B的活性,，被激活的T細(xì)胞中的KCa3.1通道活性下降,，不相關(guān)的K+通道活性不受影響。
KCa3.1使膜超極化,，為Ca2+涌入提供了潛在的動(dòng)力,。實(shí)驗(yàn)證實(shí)RNAi沉默NDPK-B后，Ca2+向被激活的T細(xì)胞的涌入能力下降,。由此證明NDPK-B對(duì)于調(diào)節(jié)T細(xì)胞功能有重要作用,。
這些研究結(jié)果為證實(shí)“組胺酸磷酸化調(diào)節(jié)哺乳動(dòng)物的生理學(xué)過程”，弄清“組胺酸磷酸化調(diào)節(jié)離子通道活性”提供了模型,。NDPK-B在CD4 T細(xì)胞活化過程中的關(guān)鍵作用,，有助于尋找激活T細(xì)胞的新途徑。
部分英文原文：
Histidine Phosphorylation of the Potassium Channel KCa3.1 by Nucleoside Diphosphate Kinase B Is Required for Activation of KCa3.1 and CD4 T Cells
The Ca2+-activated K+ channel KCa3.1 is required for Ca2+ influx and the subsequent activation of B and T cells. Inhibitors of KCa3.1 are in development to treat autoimmune diseases and transplant rejection, underscoring the importance in understanding how these channels are regulated. We show that nucleoside diphosphate kinase B (NDPK-B), a mammalian histidine kinase, functions downstream of PI(3)P to activate KCa3.1. NDPK-B directly binds and activates KCa3.1 by phosphorylating histidine 358 in the carboxyl terminus of KCa3.1. Endogenous NDPK-B is also critical for KCa3.1 channel activity and the subsequent activation of CD4 T cells. These findings provide one of the best examples whereby histidine phosphorylation regulates a biological process in mammals, and provide an example whereby a channel is regulated by histidine phosphorylation. The critical role for NDPK-B in the reactivation of CD4 T cells indicates that understanding NDPK-B regulation should uncover novel pathways required for T cell activation.
更多原文鏈接：
http://www.molecule.org/content/article/abstract?uid=PIIS1097276506007830
