Functional analyses of heteromeric human PIEZO1 Channels

PIEZO1 and PIEZO2 are mechanosensitive channels (MSCs) important for cellular function and mutations in them lead to human disorders. We examined how functional heteromers form between subunits of PIEZO1 using the mutants E2117K, E2117D, and E2117A. Homomers of E2117K do not conduct. E2117A homomers have low conductance with rapid inactivation, and those of E2117D have high conductance with slow inactivation. Pairing E2117K with E2117D or E2117A with E2117D gave rise to new channel species representing heteromers with distinct conductances. Whole-cell currents from co-expression of E2117A and E2117D fit well with a linear-combination model of homomeric channel currents suggesting that functional channels do not form from freely-diffusing, randomly-mixed monomers in-vitro. Whole-cell current from coexpressed PIEZO1/PIEZO2 also fit as a linear combination of homomer currents. High-resolution optical images of fluorescently-tagged channels support this interpretation because coexpressed subunits segregate into discrete domains.PIEZO1与PIEZO2均为机械敏感性离子通道（mechanosensitive channels, MSCs），对细胞功能至关重要，其突变会引发人类疾病。本研究利用E2117K、E2117D及E2117A三种突变体，探究了PIEZO1亚基间功能性异源多聚体的形成机制。E2117K的同源多聚体无法传导电流；E2117A同源多聚体具有低电导特性且快速失活，而E2117D同源多聚体则表现为高电导且缓慢失活。将E2117K与E2117D组合，或E2117A与E2117D组合，可产生具有独特电导特性的异源多聚体通道新类型。对E2117A与E2117D共表达所产生的全细胞电流进行拟合，结果与同源多聚体通道电流的线性组合模型高度吻合，这表明在体外环境中，功能性通道并非由自由扩散、随机混合的亚基单体组装而成。共表达的PIEZO1/PIEZO2所产生的全细胞电流，同样符合同源多聚体电流的线性组合模型。对荧光标记通道的高分辨率光学成像结果也支持这一结论，因为共表达的亚基会分离为离散的结构域。