Proceedings of the National Academy of Sciences of the United States of America ( IF 11.1 ) Pub Date : 2020-07-14 , DOI: 10.1073/pnas.1915386117 Ga-Yeon Son 1 , Krishna Prasad Subedi 1 , Hwei Ling Ong 1 , Lucile Noyer 2 , Hassan Saadi 1 , Changyu Zheng 3 , Rajesh Bhardwaj 4 , Stefan Feske 2 , Indu Suresh Ambudkar 5
The Orai1 channel is regulated by stromal interaction molecules STIM1 and STIM2 within endoplasmic reticulum (ER)-plasma membrane (PM) contact sites. Ca2+ signals generated by Orai1 activate Ca2+-dependent gene expression. When compared with STIM1, STIM2 is a weak activator of Orai1, but it has been suggested to have a unique role in nuclear factor of activated T cells 1 (NFAT1) activation triggered by Orai1-mediated Ca2+ entry. In this study, we examined the contribution of STIM2 in NFAT1 activation. We report that STIM2 recruitment of Orai1/STIM1 to ER-PM junctions in response to depletion of ER-Ca2+ promotes assembly of the channel with AKAP79 to form a signaling complex that couples Orai1 channel function to the activation of NFAT1. Knockdown of STIM2 expression had relatively little effect on Orai1/STIM1 clustering or local and global [Ca2+]i increases but significantly attenuated NFAT1 activation and assembly of Orai1 with AKAP79. STIM1ΔK, which lacks the PIP2-binding polybasic domain, was recruited to ER-PM junctions following ER-Ca2+ depletion by binding to Orai1 and caused local and global [Ca2+]i increases comparable to those induced by STIM1 activation of Orai1. However, in contrast to STIM1, STIM1ΔK induced less NFAT1 activation and attenuated the association of Orai1 with STIM2 and AKAP79. Orai1-AKAP79 interaction and NFAT1 activation were recovered by coexpressing STIM2 with STIM1ΔK. Replacing the PIP2-binding domain of STIM1 with that of STIM2 eliminated the requirement of STIM2 for NFAT1 activation. Together, these data demonstrate an important role for STIM2 in coupling Orai1-mediated Ca2+ influx to NFAT1 activation.
中文翻译:
STIM2将Orai1 / STIM1靶向AKAP79信号复合物,并使Ca2 +进入与NFAT1激活结合。
Orai1通道受内质网(ER)-质膜(PM)接触位点内的基质相互作用分子STIM1和STIM2调控。Orai1生成的Ca 2+信号激活了Ca 2+依赖性基因表达。与STIM1相比,STIM2是Orai1的弱激活因子,但已建议在Orai1介导的Ca 2+进入触发的激活T细胞1(NFAT1)激活的核因子中具有独特作用。在这项研究中,我们检查了STIM2在NFAT1激活中的作用。我们报告说,响应于ER-Ca 2+的耗竭,Orai1 / STIM1向ER-PM连接的STIM2募集促进AKAP79通道的组装,形成一个信号复合物,将Orai1通道功能与NFAT1激活耦合。击倒STIM2表达对Orai1 / STIM1聚簇或局部和全局[Ca 2+ ] i的增加影响相对较小,但NAK1激活和AKAP79组装的Orai1明显减弱。缺少PIP 2结合多元结构域的STIM1ΔK通过与Orai1结合而在ER-Ca 2+耗尽后被募集至ER-PM连接,并引起局部和全局[Ca 2+ ] i的增加与Orai1的STIM1激活所诱导的增加相当。但是,与STIM1相比,STIM1ΔK诱导的NFAT1激活较少,并且减弱了Orai1与STIM2和AKAP79的关联。通过与STIM1ΔK共表达STIM2,恢复了Orai1-AKAP79相互作用和NFAT1激活。用STIM2替换STIM1的PIP 2绑定域消除了STIM2对NFAT1激活的需求。在一起,这些数据表明STIM2在Orai1介导的Ca 2+内流与NFAT1激活偶联中起重要作用。