Lady Davis Institute for Medical Research, McGill University, Montreal, Quebec, Canada.
Biochem J. 2010 Nov 15;432(1):145-51. doi: 10.1042/BJ20100541.
Late-stage erythroid cells synthesize large quantities of haemoglobin, a process requiring the co-ordinated regulation of globin and haem synthesis as well as iron uptake. In the present study, we investigated the role of the ERK (extracellular-signal-regulated kinase) and p38 MAPK (mitogen-activated protein kinase) signalling pathways in MEL (mouse erythroleukaemia) cell differentiation. We found that treatment of HMBA (hexamethylene bisacetamide)-induced MEL cells with the ERK pathway inhibitor UO126 results in an increase in intracellular haem and haemoglobin levels. The transcript levels of the genes coding for β(major)-globin, the haem biosynthesis enzyme 5-aminolevulinate synthase 2 and the mitochondrial iron transporter mitoferrin 1 are up-regulated. We also showed enhanced expression of globin and transferrin receptor 1 proteins upon UO126 treatment. With respect to iron uptake, we found that ERK inhibitor treatment led to an increase in both haem-bound and total iron. In contrast, treatment of MEL cells with the p38 MAPK pathway inhibitor SB202190 had the opposite effect, resulting in decreased globin expression, haem synthesis and iron uptake. Reporter assays showed that globin promoter and HS2 enhancer-mediated transcription was under the control of MAPKs, as inhibition of the ERK and p38 MAPK pathways led to increased and decreased gene activity respectively. Our present results suggest that the ERK1/2 and p38α/β MAPKs play antagonistic roles in HMBA-induced globin gene expression and erythroid differentiation. These results provide a novel link between MAPK signalling and the regulation of haem biosynthesis and iron uptake in erythroid cells.
晚期红细胞合成大量血红蛋白，这一过程需要协调调节珠蛋白和血红素的合成以及铁的摄取。本研究探讨了 ERK（细胞外信号调节激酶）和 p38 MAPK（丝裂原活化蛋白激酶）信号通路在 MEL（小鼠红白血病）细胞分化中的作用。我们发现，用 ERK 通路抑制剂 UO126 处理 HMBA（己二烯双乙酰胺）诱导的 MEL 细胞，会导致细胞内血红素和血红蛋白水平升高。编码β（主要）珠蛋白、血红素生物合成酶 5-氨基乙酰丙酸合酶 2 和线粒体铁转运蛋白 mitoferrin 1 的基因转录水平上调。我们还表明，UO126 处理后，珠蛋白和转铁蛋白受体 1 蛋白的表达增强。关于铁摄取，我们发现 ERK 抑制剂处理导致血红素结合铁和总铁增加。相比之下，用 p38 MAPK 通路抑制剂 SB202190 处理 MEL 细胞则产生相反的效果，导致珠蛋白表达、血红素合成和铁摄取减少。报告基因实验表明，珠蛋白启动子和 HS2 增强子介导的转录受 MAPKs 控制，因为 ERK 和 p38 MAPK 通路的抑制分别导致基因活性的增加和减少。我们目前的结果表明，ERK1/2 和 p38α/β MAPKs 在 HMBA 诱导的珠蛋白基因表达和红细胞分化中发挥拮抗作用。这些结果为 MAPK 信号与红细胞中血红素生物合成和铁摄取的调节之间提供了新的联系。
