Obesity Research Centre, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Australia.
Biochem J. 2012 Jun 1;444(2):323-31. doi: 10.1042/BJ20112033.
CARM1 (co-activator-associated arginine methyltransferase 1)/PRMT4 (protein arginine methyltransferase 4), functions as a co-activator for transcription factors that are regulators of muscle fibre type and oxidative metabolism, including PGC (peroxisome-proliferator-activated receptor γ co-activator)-1α and MEF2 (myocyte enhancer factor 2). We observed significantly higher Prmt4 mRNA expression in comparison with Prmt1-Prmt6 mRNA expression in mouse muscle (in vitro and in vivo). Transfection of Prmt4 siRNA (small interfering RNA) into mouse skeletal muscle C2C12 cells attenuated PRMT4 mRNA and protein expression. We subsequently performed additional qPCR (quantitative PCR) analysis (in the context of metabolism) to examine the effect of Prmt4 siRNA expression on >200 critical genes that control (and are involved in) lipid, glucose and energy homoeostasis, and circadian rhythm. This analysis revealed a strikingly specific metabolic expression footprint, and revealed that PRMT4 is necessary for the expression of genes involved in glycogen metabolism in skeletal muscle cells. Prmt4 siRNA expression selectively suppressed the mRNAs encoding Gys1 (glycogen synthase 1), Pgam2 (muscle phosphoglycerate mutase 2) and Pygm (muscle glycogen phosphorylase). Significantly, PGAM, PYGM and GYS1 deficiency in humans causes glycogen storage diseases type X, type V/McArdle's disease and type 0 respectively. Attenuation of PRMT4 was also associated with decreased expression of the mRNAs encoding AMPK (AMP-activated protein kinase) α2/γ3 (Prkaa2 and Prkag3) and p38 MAPK (mitogen-activated protein kinase), previously implicated in Wolff-Parkinson-White syndrome and Pompe Disease (glycogen storage disease type II). Furthermore, stable transfection of two PRMT4-site-specific (methyltransferase deficient) mutants (CARM1/PRMT4 VLD and CARM1E267Q) significantly repressed the expression of Gys1, Pgam2 and AMPKγ3. Finally, in concordance, we observed increased and decreased glycogen levels in PRMT4 (native)- and VLD (methylation deficient mutant)-transfected skeletal muscle cells respectively. This demonstrated that PRMT4 expression and the associated methyltransferase activity is necessary for the gene expression programme involved in glycogen metabolism and human glycogen storage diseases.
CARM1（共激活剂相关精氨酸甲基转移酶 1）/PRMT4（蛋白精氨酸甲基转移酶 4）作为转录因子的共激活因子发挥作用，这些转录因子是肌纤维类型和氧化代谢的调节剂，包括 PGC（过氧化物酶体增殖物激活受体 γ 共激活因子）-1α 和 MEF2（肌增强因子 2）。与 Prmt1-Prmt6 mRNA 在小鼠肌肉中的表达相比，我们观察到小鼠肌肉中的 Prmt4 mRNA 表达显著更高（体外和体内）。将 Prmt4 siRNA（小干扰 RNA）转染入小鼠骨骼肌 C2C12 细胞可减弱 PRMT4 mRNA 和蛋白表达。随后，我们进行了额外的 qPCR（定量 PCR）分析（在代谢背景下），以检查 Prmt4 siRNA 表达对 200 多个控制（和参与）脂质、葡萄糖和能量动态平衡以及昼夜节律的关键基因的影响。该分析揭示了一个惊人的特定代谢表达特征，并表明 PRMT4 是骨骼肌细胞中参与糖原代谢的基因表达所必需的。Prmt4 siRNA 表达选择性抑制编码 Gys1（糖原合酶 1）、Pgam2（肌肉磷酸甘油酸变位酶 2）和 Pygm（肌肉糖原磷酸化酶）的 mRNA。值得注意的是，PGAM、PYGM 和 GYS1 缺陷导致人类糖原贮积症 X 型、V/McArdle 病和 0 型糖原贮积症。PRMT4 的衰减也与编码 AMPK（AMP 激活蛋白激酶）α2/γ3（Prkaa2 和 Prkag3）和 p38 MAPK（丝裂原激活蛋白激酶）的 mRNA 表达降低相关，这些基因先前与 Wolff-Parkinson-White 综合征和 Pompe 病（糖原贮积症 II 型）有关。此外，两种 PRMT4 特异性（甲基转移酶缺陷）突变体（CARM1/PRMT4 VLD 和 CARM1E267Q）的稳定转染显著抑制了 Gys1、Pgam2 和 AMPKγ3 的表达。最后，与预期一致，我们观察到在 PRMT4（天然）和 VLD（甲基化缺陷突变体）转染的骨骼肌细胞中糖原水平分别增加和减少。这表明 PRMT4 表达和相关的甲基转移酶活性对于涉及糖原代谢和人类糖原贮积症的基因表达程序是必需的。
