PDF(Pubmed)
Abstract：
The interplay of SK3, a Ca2+ sensitive K+ ion channel, with Orai1, a Ca2+ ion channel, has been reported to increase cytosolic Ca2+ levels, thereby triggering proliferation of breast and colon cancer cells, although a molecular mechanism has remained elusive to date. We show in the current study, via heterologous protein expression, that Orai1 can enhance SK3 K+ currents, in addition to constitutively bound calmodulin (CaM). At low cytosolic Ca2+ levels that decrease SK3 K+ permeation, co-expressed Orai1 potentiates SK3 currents. This positive feedback mechanism of SK3 and Orai1 is enabled by their close co-localization. Remarkably, we discovered that loss of SK3 channel activity due to overexpressed CaM mutants could be restored by Orai1, likely via its interplay with the SK3-CaM binding site. Mapping for interaction sites within Orai1, we identified that the cytosolic strands and pore residues are critical for a functional communication with SK3. Moreover, STIM1 has a bimodal role in SK3-Orai1 regulation. Under physiological ionic conditions, STIM1 is able to impede SK3-Orai1 interplay by significantly decreasing their co-localization. Forced STIM1-Orai1 activity and associated Ca2+ influx promote SK3 K+ currents. The dynamic regulation of Orai1 to boost endogenous SK3 channels was also determined in the human prostate cancer cell line LNCaP.
摘要：
SK3，Ca2+敏感的K+离子通道的相互作用，与Orai1，Ca2+离子通道，据报道可以增加细胞溶质的Ca2+水平，从而引发乳腺癌和结肠癌细胞的增殖，尽管迄今为止分子机制仍然难以捉摸。我们在目前的研究中表明，通过异源蛋白表达，Orai1可以增强SK3K+电流，除了组成型结合的钙调蛋白（CaM）。在低胞质Ca2+水平降低SK3K+渗透，共表达的Orai1增强SK3电流。SK3和Orai1的这种正反馈机制是通过它们的紧密共同定位而实现的。值得注意的是,我们发现，由于过表达的CaM突变体而导致的SK3通道活性的丧失可以通过Orai1恢复，可能是通过其与SK3-CaM结合位点的相互作用。对Orai1内的相互作用位点进行作图，我们确定胞质链和孔残基对于与SK3的功能通讯至关重要。此外，STIM1在SK3-Orai1调节中具有双峰作用。在生理离子条件下,STIM1能够通过显着降低SK3-Orai1的共同定位来阻止它们的相互作用。强制STIM1-Orai1活性和相关的Ca2流入促进SK3K电流。在人前列腺癌细胞系LNCaP中还确定了Orai1增强内源性SK3通道的动态调节。
