Aydemir Tolunay B, Liuzzi Juan P, McClellan Steve, Cousins Robert J
Center for Nutritional Sciences, College of Agricultural and Life Sciences, University of Florida, Gainesville, FL 32611, USA.
J Leukoc Biol. 2009 Aug;86(2):337-48. doi: 10.1189/jlb.1208759. Epub 2009 Apr 28.
The zinc transporter ZIP8 is highly expressed in T cells derived from human subjects. T cell ZIP8 expression was markedly up-regulated upon in vitro activation. T cells collected from human subjects who had received oral zinc supplementation (15 mg/day) had higher expression of the activation marker IFN-gamma upon in vitro activation, indicating a potentiating effect of zinc on T cell activation. Similarly, in vitro zinc treatment of T cells along with activation resulted in increased IFN-gamma expression with a maximum effect at 3.1 microM. Knockdown of ZIP8 in T cells by siRNA decreased ZIP8 levels in nonactivated and activated cells and concomitantly reduced secretion of IFN-gamma and perforin, both signatures of activation. Overexpression of ZIP8 by transient transfection caused T cells to exhibit enhanced activation. Confocal microscopy established that ZIP8 is localized to the lysosome where ZIP8 abundance is increased upon activation. Loss of lysosomal labile zinc in response to activation was measured by flow cytometry using a zinc fluorophore. Zinc between 0.8 and 3.1 microM reduced CN phosphatase activity. CN was also inhibited by the CN inhibitor FK506 and ZIP8 overexpression. The results suggest that zinc at low concentrations, through inhibition of CN, sustains phosphorylation of the transcription factor CREB, yielding greater IFN-gamma expression in T cells. ZIP8, through control of zinc transport from the lysosome, may provide a secondary level of IFN-gamma regulation in T cells.
锌转运蛋白ZIP8在源自人类受试者的T细胞中高度表达。T细胞ZIP8表达在体外激活后显著上调。从接受口服锌补充剂（15毫克/天）的人类受试者收集的T细胞在体外激活时激活标志物IFN-γ的表达更高，表明锌对T细胞激活有增强作用。同样，体外锌处理T细胞并同时激活导致IFN-γ表达增加，在3.1微摩尔时效果最佳。通过小干扰RNA敲低T细胞中的ZIP8可降低未激活和激活细胞中的ZIP8水平，并同时减少IFN-γ和穿孔素的分泌，这两者都是激活的标志。通过瞬时转染过表达ZIP8使T细胞表现出增强的激活。共聚焦显微镜检查确定ZIP8定位于溶酶体，激活后ZIP8丰度增加。使用锌荧光团通过流式细胞术测量激活后溶酶体不稳定锌的损失。0.8至3.1微摩尔的锌降低了钙调神经磷酸酶活性。钙调神经磷酸酶也受到钙调神经磷酸酶抑制剂FK506和ZIP8过表达的抑制。结果表明，低浓度的锌通过抑制钙调神经磷酸酶，维持转录因子CREB的磷酸化，在T细胞中产生更高的IFN-γ表达。ZIP8通过控制锌从溶酶体的转运，可能在T细胞中提供IFN-γ调节的二级水平。
