Inhibition of Smurf2 translation by miR-322/503 modulates TGF-β/Smad2 signaling and intestinal epithelial homeostasis.
Inhibition of Smurf2 translation by miR-322/503 modulates TGF-β/Smad2 signaling and intestinal epithelial homeostasis.
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DOI：
10.1091/mbc.e13-09-0560
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发表时间：
2014-04
影响因子：
3.3
通讯作者：
Wang JY
中科院分区：
文献类型：
--
作者：
Cao S;Xiao L;Rao JN;Zou T;Liu L;Zhang D;Turner DJ;Gorospe M;Wang JY
Smurf 2是调节TGF-β/Smad信号传导的E3泛素连接酶，并且涉及多种细胞应答。miR-322和miR-503抑制Smurf 2翻译，从而调节TGF-β/Smad 2信号传导和肠上皮稳态。Smad泛素调节因子2（Smurf 2）是一种E3泛素连接酶，调节转化生长因子β（TGF-β）/Smad信号传导，并参与多种细胞反应，但控制Smurf 2丰度的确切机制在很大程度上是未知的。在这里，我们确定microRNA-322（miR-322）和miR-503作为转录后调节Smurf 2表达的新因子。miR-322和miR-503均通过其3′-非翻译区（UTR）与Smurf 2 mRNA相互作用，并抑制Smurf 2翻译，但不影响总Smurf 2 mRNA水平。使用异源报告基因构建体的研究揭示了miR-322/503通过Smurf 2 3′-UTR中的单个结合位点产生更大的抑制作用，而该位点的点突变阻止了miR-322/503诱导的Smurf 2翻译抑制。通过miR-322/503的拮抗作用增加内源性Smurf 2的水平通过增加磷酸化Smad 2的降解来抑制TGF-β诱导的Smad 2活化。此外，在表达较低水平miR-322/503的肠上皮细胞（IEC）中Smurf 2的增加与对凋亡的抗性增加相关，这通过Smurf 2沉默而消除。这些发现表明，miR-322/503抑制Smurf 2翻译，进而通过改变TGF-β/Smad 2信号传导和IEC凋亡影响肠上皮稳态。
Smurf2 is an E3 ubiquitin ligase that regulates TGF-β/Smad signaling and is implicated in a wide variety of cellular responses. miR-322 and miR-503 repress Smurf2 translation and thus modulate TGF-β/Smad2 signaling and intestinal epithelial homeostasis. Smad ubiquitin regulatory factor 2 (Smurf2) is an E3 ubiquitin ligase that regulates transforming growth factor β (TGF-β)/Smad signaling and is implicated in a wide variety of cellular responses, but the exact mechanisms that control Smurf2 abundance are largely unknown. Here we identify microRNA-322 (miR-322) and miR-503 as novel factors that regulate Smurf2 expression posttranscriptionally. Both miR-322 and miR-503 interact with Smurf2 mRNA via its 3′-untranslated region (UTR) and repress Smurf2 translation but do not affect total Smurf2 mRNA levels. Studies using heterologous reporter constructs reveal a greater repressive effect of miR-322/503 through a single binding site in the Smurf2 3′-UTR, whereas point mutation of this site prevents miR-322/503–induced repression of Smurf2 translation. Increased levels of endogenous Smurf2 via antagonism of miR-322/503 inhibits TGF-β–induced Smad2 activation by increasing degradation of phosphorylated Smad2. Furthermore, the increase in Smurf2 in intestinal epithelial cells (IECs) expressing lower levels of miR-322/503 is associated with increased resistance to apoptosis, which is abolished by Smurf2 silencing. These findings indicate that miR-322/503 represses Smurf2 translation, in turn affecting intestinal epithelial homeostasis by altering TGF-β/Smad2 signaling and IEC apoptosis.