Stein Colleen S, Linzer Connor R, Heer Collin D, Witmer Nathan H, Cochran Jesse D, Spitz Douglas R, Boudreau Ryan L
Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA.
Free Radical and Radiation Biology Program, Department of Radiation Oncology, Holden Comprehensive Cancer Center, University of Iowa, Iowa City, IA 52242, USA.
Int J Mol Sci. 2025 Feb 24;26(5):1939. doi: 10.3390/ijms26051939.
Mitoregulin (MTLN) is a 56-amino-acid mitochondrial microprotein known to modulate mitochondrial energetics. MTLN gene expression is elevated broadly across most cancers and has been proposed as a prognostic biomarker for non-small cell lung cancer (NSCLC). In addition, lower MTLN expression in lung adenocarcinoma (LUAD) correlates with significantly improved patient survival. In our studies, we have found that MTLN silencing in A549 NSCLC cells slowed proliferation and, in accordance with this, we observed the following: (1) increased proportion of cells in the G1 phase of cell cycle; (2) protein changes consistent with G1 arrest (e.g., reduced levels and/or reduced phosphorylation of ERK, MYC, CDK2, and RB, and elevated p27); (3) reduction in clonogenic cell survival and; (4) lower steady-state cytosolic and mitochondrial HO levels as indicated by use of the roGFP2-Orp1 redox sensor. Conflicting with G1 arrest, we observed a boost in cyclin D1 abundance. We also tested MTLN silencing in combination with buthionine sulfoximine (BSO) and auranofin (AF), drugs that inhibit GSH synthesis and thioredoxin reductase, respectively, to elevate the reactive oxygen species (ROS) amount to a toxic range. Interestingly, clonogenic survival after drug treatment was greater for MTLN-silenced cultures versus the control cultures. Lower HO output and reduced vulnerability to ROS damage due to G1 status may have jointly contributed to the partial BSO + AF resistance. Overall, our results provide evidence that MTLN fosters HO signaling to propel G1/S transition and suggest MTLN silencing as a therapeutic strategy to limit NSCLC growth.
线粒体调节蛋白（MTLN）是一种由56个氨基酸组成的线粒体微蛋白，已知其可调节线粒体能量代谢。MTLN基因表达在大多数癌症中普遍升高，并已被提议作为非小细胞肺癌（NSCLC）的预后生物标志物。此外，肺腺癌（LUAD）中MTLN表达较低与患者生存率显著提高相关。在我们的研究中，我们发现A549 NSCLC细胞中MTLN沉默会减缓增殖，据此我们观察到以下情况：（1）细胞周期G1期细胞比例增加；（2）与G1期阻滞一致的蛋白质变化（例如，ERK、MYC、CDK2和RB的水平降低和/或磷酸化减少，以及p27升高）；（3）克隆形成细胞存活率降低；（4）使用roGFP2-Orp1氧化还原传感器表明，稳态胞质和线粒体HO水平降低。与G1期阻滞相反，我们观察到细胞周期蛋白D1丰度增加。我们还测试了MTLN沉默与丁硫氨酸亚砜胺（BSO）和金诺芬（AF）联合使用的情况，这两种药物分别抑制谷胱甘肽合成和硫氧还蛋白还原酶，以将活性氧（ROS）量提高到有毒范围。有趣的是，与对照培养物相比，药物处理后MTLN沉默培养物的克隆形成存活率更高。较低的HO输出和由于G1期状态导致的对ROS损伤的易感性降低可能共同导致了对BSO + AF的部分抗性。总体而言，我们的结果提供了证据，表明MTLN促进HO信号传导以推动G1/S期转变，并表明MTLN沉默作为一种限制NSCLC生长的治疗策略。
