Agca Cavit, Boldt Karsten, Gubler Andrea, Meneau Isabelle, Corpet Armelle, Samardzija Marijana, Stucki Manuel, Ueffing Marius, Grimm Christian
Department of Ophthalmology, Lab for Retinal Cell Biology, University of Zurich, Wagistrasse 14, Zurich, 8091, Switzerland.
Present address: Department of Biomedicine, University Hospital Basel, Basel, 4031, Switzerland.
BMC Biol. 2015 Apr 25;13:30. doi: 10.1186/s12915-015-0137-1.
Photoreceptor degeneration is a main hallmark of many blinding diseases making protection of photoreceptors crucial to prevent vision loss. Thus, regulation of endogenous neuroprotective factors may be key for cell survival and attenuation of disease progression. Important neuroprotective factors in the retina include H2O2 generated by injured photoreceptors, and leukemia inhibitory factor (LIF) expressed in Müller glia cells in response to photoreceptor damage.
We present evidence that H2O2 connects to the LIF response by inducing stabilization of Lif transcripts in Müller cells. This process was independent of active gene transcription and p38 MAPK, but relied on AU-rich elements (AREs), which we identified within the highly conserved Lif 3'UTR. Affinity purification combined with quantitative mass spectrometry identified several proteins that bound to these AREs. Among those, interleukin enhancer binding factor 3 (ILF3) was confirmed to participate in the redox-dependent Lif mRNA stabilization. Additionally we show that KH-type splicing regulatory protein (KHSRP) was crucial for maintaining basal Lif expression levels in non-stressed Müller cells.
Our results suggest that H2O2-induced redox signaling increases Lif transcript levels through ILF3 mediated mRNA stabilization. Generation of H2O2 by injured photoreceptors may thus enhance stability of Lif mRNA and therefore augment neuroprotective LIF signaling during degenerative conditions in vivo.
光感受器变性是许多致盲疾病的主要特征，因此保护光感受器对于预防视力丧失至关重要。因此，调节内源性神经保护因子可能是细胞存活和减缓疾病进展的关键。视网膜中重要的神经保护因子包括受损光感受器产生的过氧化氢（H2O2），以及Müller胶质细胞在光感受器损伤时表达的白血病抑制因子（LIF）。
我们提供的证据表明，H2O2通过诱导Müller细胞中Lif转录本的稳定来连接LIF反应。这个过程独立于活跃的基因转录和p38丝裂原活化蛋白激酶（p38 MAPK），但依赖于富含AU元件（AREs），我们在高度保守的Lif 3'非翻译区（UTR）中鉴定到了这些元件。亲和纯化结合定量质谱分析鉴定出了几种与这些AREs结合的蛋白质。其中，白细胞介素增强子结合因子3（ILF3）被证实参与了氧化还原依赖性的Lif mRNA稳定。此外，我们还表明KH型剪接调节蛋白（KHSRP）对于维持非应激Müller细胞中基础Lif表达水平至关重要。
我们的结果表明，H2O2诱导的氧化还原信号通过ILF3介导的mRNA稳定增加了Lif转录水平。因此，受损光感受器产生的H2O2可能会增强Lif mRNA的稳定性，从而在体内退行性病变过程中增强神经保护LIF信号。
