Junctophilin在小电导Ca2+-激活K+通道与RyR受体功能耦联中的作用

Dysfunction in small conductance Ca2+-activated K+ channels (SK) is close associated with atrial arrhythmias. Searching for molecular modulations of SK channels have important implication in our understandings of inducibility for arrhythmias. Our previous study demenstrated a functional modulation of ryanodine receptor type 2 (RyR2) on the SK2 channel in mouse cardiac myocytes. However, molecular mechanisms underlying the coupling of the SK2 channel to RyR2 are not known. Our newly data show that both SK2 protein and RyR2 form immunocomplexes with junctophilin2（JPH2）that is component of the cardiac junctional complexes ，in native mouse atria by co-immunoprecipitation assays.Till now no report has showed functional coupling of SK2 channel with RyR2 Ca2+ release channels via JPHs in the cardiac muscle yet. In this present study we'll directly documente interactions between JPH2 and these two proteins of SK2 and RyR2. Next,we'll determine whether JPH2 could aid in the proper membrane localization of SK2 channels and contribute RyR2-sensitive Ca2+ release to calcium homeostasis. Moreover, we will examine mRNA and protein levels of SK2 and RyR2 in culture mouse neonatal cardiomyocytes treated with lentivirus-mediated siRNA specific to JPH2. Finally, we will investigate knockdown of JPH2 on functional crosstalk between SK2 channel and RyR2 in the cardiac myocytes. Our study will present those roles of junctophilin2 on coupling of SK2 channel with RyR2 in the cardiac myocytes. These studies will reveal molecular mechanisms of the coupling of SK2 channel with RyR2-sensitive Ca2+ release channel via junctophilin. The new insights may provide drug targets for the treatment of atrial arrhythmias.

小电导Ca2+激活K+通道（SK）功能异常与心律失常的发生密切相关。研究SK通道的分子调控对揭示心律失常的发生机制有重要的科学意义。我们前期工作表明RyR2对心肌SK2通道具有调控作用，但不清楚其机理。预实验提示耦联胞浆膜与肌质网膜的Junctophilin2（JPH2）蛋白与心肌RyR2和SK2可形成免疫共沉淀。RyR2对心肌SK2调控是否与JPHs相关，国内外尚未见报道。本项目拟在此基础上深入研究JPH在心肌SK通道与RyRs功能耦联中的作用:1.研究心肌JPH2与SK2、RyR2蛋白交联及相互作用；2.研究JPH2与SK2通道膜表面定位、与RyR2Ca2+释放的生理性相关；3.研究心肌细胞JPH2敲减与心肌细胞SK2和RyR2表达;4.研究JPH2敲减对SK2与RyR2功能耦联的影响。从理论上阐明JPH是心肌SK通道与RyRs功能耦联的关键分子，为心律失常的防治和药物筛选提供新靶点。