Hashimoto Kazunori, Majumdar Rima, Tsuji Yoshiaki
Department of Biological Sciences, North Carolina State University, Campus Box 7633, Raleigh, NC 27695-7633, United States.
Department of Biological Sciences, North Carolina State University, Campus Box 7633, Raleigh, NC 27695-7633, United States.
Cell Signal. 2017 May;33:69-78. doi: 10.1016/j.cellsig.2017.02.012. Epub 2017 Feb 14.
Lamins are important constituents of the nuclear inner membrane and provide a platform for transcription factors and chromatin. Progerin, a C-terminal truncated lamin A mutant, causes premature aging termed Hutchinson-Gilford Progeria Syndrome (HGPS). Oxidative stress appears to be involved in the pathogenesis of HGPS, although the mechanistic role of progerin remains elusive. Here we examined whether nuclear lamins are important for a cellular antioxidant mechanism, and whether progerin compromises it. We investigated the activation of nuclear factor-E2-related factor 2 (Nrf2) which regulates various antioxidant genes including heme oxygenase-1 (HMOX1), following exposure to sodium arsenite or cadmium chloride in lamin knockdown human cell lines and primary HGPS human fibroblasts. Knocking down lamin A/C, or B, or all nuclear lamins simultaneously in three human cell lines (HaCaT, SW480, and K562) did not impair arsenite- or cadmium-induced activation of Nrf2. Progerin-expressing human primary HGPS fibroblasts showed lower basal levels of HMOX1 and NQO1 expression; however, in response to arsenic stress both normal and HGPS primary fibroblasts showed Nrf2 nuclear accumulation along with upregulation and phosphorylation of p62/SQSTM1 at Ser351, downregulation of Keap1, and comparable expression of an array of downstream Nrf2-regulated antioxidant genes. We also observed new forms of cleaved lamin A, B1 and B2 induced by cadmium stress although their roles in the Nrf2 antioxidant system need further investigation. These results suggest that the nuclear lamins and progerin have marginal roles in the activation of the antioxidant Nrf2 response to arsenic and cadmium.
核纤层蛋白是核内膜的重要组成部分，为转录因子和染色质提供了一个平台。早老素是一种C末端截短的核纤层蛋白A突变体，会导致被称为哈钦森-吉尔福德早衰综合征（HGPS）的早衰现象。氧化应激似乎参与了HGPS的发病机制，尽管早老素的作用机制仍不清楚。在这里，我们研究了核纤层蛋白对细胞抗氧化机制是否重要，以及早老素是否会损害该机制。我们在核纤层蛋白敲低的人类细胞系和原发性HGPS人类成纤维细胞中，研究了在暴露于亚砷酸钠或氯化镉后，调节包括血红素加氧酶-1（HMOX1）在内的各种抗氧化基因的核因子-E2相关因子2（Nrf2）的激活情况。在三种人类细胞系（HaCaT、SW480和K562）中同时敲低核纤层蛋白A/C、或B、或所有核纤层蛋白，并不损害亚砷酸盐或镉诱导的Nrf2激活。表达早老素的人类原发性HGPS成纤维细胞显示出较低的HMOX1和NQO1基础表达水平；然而，在砷应激反应中，正常和HGPS原发性成纤维细胞均显示出Nrf2核积累，同时Ser351处的p62/SQSTM1上调和磷酸化、Keap1下调，以及一系列下游Nrf2调节的抗氧化基因的表达相当。我们还观察到镉应激诱导的新形式的裂解核纤层蛋白A、B1和B2，尽管它们在Nrf2抗氧化系统中的作用需要进一步研究。这些结果表明，核纤层蛋白和早老素在抗氧化剂Nrf2对砷和镉的反应激活中作用不大。
