Williams Sandile E, Wootton Phillippa, Mason Helen S, Iles David E, Peers C, Kemp Paul J
School of Biomedical Sciences, University of Leeds, UK.
Biochem Biophys Res Commun. 2004 Jan 30;314(1):63-8. doi: 10.1016/j.bbrc.2003.12.052.
Large conductance, Ca(2+)-sensitive potassium (BK) channels are critical components of the O(2) signalling cascade in a number of cells, including the carotid body and central neurones. Although the nature of the BK channel O(2) sensor is still unknown, evidence suggests redox modulators might form part of the O(2) sensing channel complex. By metabolising glutathione, gamma-glutamyl transpeptidase (gammaGT) could act as such an O(2) sensor. Western blotting and immunocytochemistry revealed high gammaGT expression in HEK293 cells expressing the alpha- and beta-subunits of human recombinant BK and gammaGT co-immunoprecipitated with BKalpha. Acivicin blockade of gammaGT reversibly inhibited BK channels, suggesting that this BKalpha protein partner contributes to tonic channel activity. However, knock-out of gammaGT using siRNA had no effect on hypoxic BK channel inhibition. Together, these data indicate that gammaGT is a BKalpha protein partner, that its activity regulates BK channels but that it is not the BK O(2) sensor.
大电导钙敏感钾（BK）通道是包括颈动脉体和中枢神经元在内的许多细胞中氧信号级联反应的关键组成部分。尽管BK通道氧传感器的本质仍不清楚，但有证据表明氧化还原调节剂可能是氧传感通道复合物的一部分。γ-谷氨酰转肽酶（γGT）通过代谢谷胱甘肽可能充当这样一种氧传感器。蛋白质免疫印迹法和免疫细胞化学分析显示，在表达人重组BKα和β亚基的HEK293细胞中γGT表达较高，且γGT与BKα共免疫沉淀。阿西维辛对γGT的阻断可可逆地抑制BK通道，这表明这种BKα蛋白伴侣有助于通道的静息活性。然而，使用小干扰RNA敲除γGT对缺氧时BK通道的抑制作用没有影响。总之，这些数据表明γGT是BKα的蛋白伴侣，其活性调节BK通道，但它不是BK氧传感器。
