Okada Toshiaki, Islam Md Rafiqul, Tsiferova Nargiza A, Okada Yasunobu, Sabirov Ravshan Z
a International Collaborative Research Project, National Institute for Physiological Sciences , Okazaki , Japan.
b Division of Cell Signaling , National Institute for Physiological Sciences , National Institutes of Natural Sciences , Okazaki , Japan.
Channels (Austin). 2017 Mar 4;11(2):109-120. doi: 10.1080/19336950.2016.1247133. Epub 2016 Oct 20.
The broadly expressed volume-sensitive outwardly rectifying anion channel (VSOR, also called VRAC) plays essential roles in cell survival and death. Recent findings have suggested that LRRC8A is a core component of VSOR in human cells. In the present study, VSOR currents were found to be largely reduced by siRNA against LRRC8A in mouse C127 cells as well. In contrast, LRRC8A knockdown never affected activities of 4 other types of anion channel activated by acid, Ca, patch excision or cAMP. While cisplatin-resistant KCP-4 cells poorly expressed endogenous VSOR activity, molecular expression levels of LRRC8A, LRRC8D and LRRC8E were indistinguishable between VSOR-deficient KCP-4 cells and the parental VSOR-rich KB cells. Furthermore, overexpression of LRRC8A alone or together with LRRC8D or LRRC8E in KCP-4 cells failed to restore VSOR activity. These results show that deficiency of VSOR currents in KCP-4 cells is not due to insufficient expression of the LRRC8A/D/E gene, suggesting an essential involvement of some other factor(s), and indicate that further study is required to better understand the complexities of the molecular determinants of VSOR, including the precise role of LRRC8 proteins.
广泛表达的容积敏感性外向整流阴离子通道（VSOR，也称为VRAC）在细胞存活和死亡中起重要作用。最近的研究结果表明，LRRC8A是人类细胞中VSOR的核心成分。在本研究中，在小鼠C127细胞中，针对LRRC8A的小干扰RNA（siRNA）也使VSOR电流大幅降低。相比之下，敲低LRRC8A对其他4种由酸、钙、膜片切除或环磷酸腺苷（cAMP）激活的阴离子通道的活性没有影响。虽然顺铂耐药的KCP-4细胞内源性VSOR活性表达较差，但在缺乏VSOR的KCP-4细胞和富含VSOR的亲代KB细胞之间，LRRC8A、LRRC8D和LRRC8E的分子表达水平没有差异。此外，在KCP-4细胞中单独过表达LRRC8A或与LRRC8D或LRRC8E一起过表达均未能恢复VSOR活性。这些结果表明，KCP-4细胞中VSOR电流的缺乏不是由于LRRC8A/D/E基因表达不足所致，提示有其他一些因素的重要参与，并表明需要进一步研究以更好地理解VSOR分子决定因素的复杂性，包括LRRC8蛋白的确切作用。
