Alternative splicing of UCP1 by non-cell-autonomous action of PEMT.,Molecular Metabolism

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Alternative splicing of UCP1 by non-cell-autonomous action of PEMT.
Molecular Metabolism ( IF 7.0 ) Pub Date : 2019-11-08 , DOI: 10.1016/j.molmet.2019.10.007
Jordan M Johnson ₁ , Anthony R P Verkerke ₁ , J Alan Maschek ₂ , Patrick J Ferrara ₁ , Chien-Te Lin ₃ , Kimberly A Kew ₄ , P Darrell Neufer ₃ , Irfan J Lodhi ₅ , James E Cox ₂ , Katsuhiko Funai ₆

Affiliation

Diabetes & Metabolism Research Center, University of Utah, 15 N. 2030 E, Salt Lake City, UT, 84112, USA; Department of Nutrition & Integrative Physiology, University of Utah, 250 S. 1850 E., RM 214, Salt Lake City, UT, 84112, USA; Department of Physical Therapy & Athletic Training, University of Utah, 520 Wakara Way, Salt Lake City, UT, 84108, USA; East Carolina Diabetes & Obesity Institute, East Carolina University, 115 Heart Drive, 4101 ECHI, Greenville, NC, 27834, USA.
Diabetes & Metabolism Research Center, University of Utah, 15 N. 2030 E, Salt Lake City, UT, 84112, USA; Metabolomics Core Research Facility, University of Utah, 15 N. Medical Dr. East RM A306, Salt Lake City, UT, 84112, USA; Department of Biochemistry, University of Utah, 15 N. Medical Dr. East RM 4100, Salt Lake City, UT, 84112, USA.
East Carolina Diabetes & Obesity Institute, East Carolina University, 115 Heart Drive, 4101 ECHI, Greenville, NC, 27834, USA.
East Carolina Diabetes & Obesity Institute, East Carolina University, 115 Heart Drive, 4101 ECHI, Greenville, NC, 27834, USA; Department of Chemistry, East Carolina University, Greenville, NC, 27858, USA.
Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, 660 S. Euclid Ave, St. Louis, MO, 63110, USA.
Diabetes & Metabolism Research Center, University of Utah, 15 N. 2030 E, Salt Lake City, UT, 84112, USA; Department of Nutrition & Integrative Physiology, University of Utah, 250 S. 1850 E., RM 214, Salt Lake City, UT, 84112, USA; Department of Physical Therapy & Athletic Training, University of Utah, 520 Wakara Way, Salt Lake City, UT, 84108, USA; East Carolina Diabetes & Obesity Institute, East Carolina University, 115 Heart Drive, 4101 ECHI, Greenville, NC, 27834, USA; Molecular Medicine Program, University of Utah, 15 N. 2030 E. RM 4145, Salt Lake City, UT, 84112, USA.

Objective

Phosphatidylethanolamine methyltransferase (PEMT) generates phosphatidylcholine (PC), the most abundant phospholipid in the mitochondria and an important acyl chain donor for cardiolipin (CL) biosynthesis. Mice lacking PEMT (PEMTKO) are cold-intolerant when fed a high-fat diet (HFD) due to unclear mechanisms. The purpose of this study was to determine whether PEMT-derived phospholipids are important for the function of uncoupling protein 1 (UCP1) and thus for maintenance of core temperature.

Methods

To test whether PEMT-derived phospholipids are important for UCP1 function, we examined cold-tolerance and brown adipose (BAT) mitochondria from PEMTKO mice with or without HFD feeding. We complemented these studies with experiments on mice lacking functional CL due to tafazzin knockdown (TAZKD). We generated several conditional mouse models to study the tissue-specific roles of PEMT, including mice with BAT-specific knockout of PEMT (PEMT-BKO).

Results

Chow- and HFD-fed PEMTKO mice completely lacked UCP1 protein in BAT, despite a lack of difference in mRNA levels, and the mice were accordingly cold-intolerant. While HFD-fed PEMTKO mice exhibited reduced mitochondrial CL content, this was not observed in chow-fed PEMTKO mice or TAZKD mice, indicating that the lack of UCP1 was not attributable to CL deficiency. Surprisingly, the PEMT-BKO mice exhibited normal UCP1 protein levels. Knockout of PEMT in the adipose tissue (PEMT-AKO), liver (PEMT-LKO), or skeletal muscle (PEMT-MKO) also did not affect UCP1 protein levels, suggesting that lack of PEMT in other non-UCP1-expressing cells communicates to BAT to suppress UCP1. Instead, we identified an untranslated UCP1 splice variant that was triggered during the perinatal period in the PEMTKO mice.

Conclusions

PEMT is required for UCP1 splicing that yields functional protein. This effect is derived by PEMT in nonadipocytes that communicates to BAT during embryonic development. Future research will focus on identifying the non-cell-autonomous PEMT-dependent mechanism of UCP1 splicing.

中文翻译：

通过 PEMT 的非细胞自主作用对 UCP1 进行选择性剪接。

客观的

磷脂酰乙醇胺甲基转移酶 (PEMT) 产生磷脂酰胆碱 (PC)，这是线粒体中最丰富的磷脂，也是心磷脂 (CL) 生物合成的重要酰基链供体。由于不明确的机制，缺乏 PEMT (PEMTKO) 的小鼠在喂食高脂肪饮食 (HFD) 时不耐寒。本研究的目的是确定 PEMT 衍生的磷脂是否对解偶联蛋白 1 (UCP1) 的功能以及维持核心温度是否重要。

方法

为了测试 PEMT 衍生的磷脂对 UCP1 功能是否重要，我们检查了有或没有 HFD 喂养的 PEMTKO 小鼠的耐寒性和棕色脂肪 (BAT) 线粒体。我们通过对由于 tafazzin 敲低（TAZKD）而缺乏功能性 CL 的小鼠进行的实验来补充这些研究。我们生成了几个条件小鼠模型来研究 PEMT 的组织特异性作用，包括具有 BAT 特异性敲除 PEMT (PEMT-BKO) 的小鼠。

结果

Chow 和 HFD 喂养的 PEMTKO 小鼠在 BAT 中完全缺乏 UCP1 蛋白，尽管 mRNA 水平没有差异，因此小鼠不耐寒。虽然 HFD 喂养的 PEMTKO 小鼠表现出线粒体 CL 含量降低，但在食物喂养的 PEMTKO 小鼠或 TAZKD 小鼠中没有观察到，这表明 UCP1 的缺乏不是由于 CL 缺乏所致。令人惊讶的是，PEMT-BKO 小鼠的 UCP1 蛋白水平正常。在脂肪组织 (PEMT-AKO)、肝脏 (PEMT-LKO) 或骨骼肌 (PEMT-MKO) 中敲除 PEMT 也不会影响 UCP1 蛋白水平，这表明在其他非 UCP1 表达细胞中缺乏 PEMT到 BAT 以抑制 UCP1。相反，我们在 PEMTKO 小鼠的围产期发现了一种未翻译的 UCP1 剪接变体。