Institute of Pathological Physiology, First Faculty of Medicine, Charles University , Prague , Czech Republic.
Laboratory of Tumour Resistance, Institute of Biotechnology, Biotechnology and Biomedicine Center of the Academy of Sciences and Charles University in Vestec Research Center, Czech Academy of Sciences, Vestec, Czech Republic.
Am J Physiol Gastrointest Liver Physiol. 2018 Oct 1;315(4):G560-G568. doi: 10.1152/ajpgi.00070.2018. Epub 2018 Jun 21.
Although the relationship between hereditary hemochromatosis and mutations in the HFE gene was discovered more than 20 years ago, information on the in vivo regulation of HFE protein expression is still limited. The purpose of the study was to determine the response of liver HFE protein content to iron deficiency in mice and rats by immunoblotting. Attempts to visualize the HFE protein in whole liver homogenates were unsuccessful; however, HFE could be detected in liver microsomes or in plasma membrane-enriched fractions. Five-week-old male C57BL/6 mice fed an iron-deficient diet for 4 wk presented with a significant decrease in liver iron content and liver Hamp expression, as well as with a significant decrease in liver HFE protein content. Rats fed an iron-deficient diet for 4 wk also displayed significant decrease in liver Hamp expression and liver HFE protein content. These results suggest that the downregulation of HFE-dependent signaling may contribute to decreased Hamp gene expression in states of prolonged iron deficiency. It has recently been proposed that HFE protein could be a potential target of matriptase-2, a hepatocyte protease mutated in iron-refractory iron deficiency anemia. However, immunoblot analysis of HFE protein in the livers from Tmprss6-mutated mask mice did not show evidence of matriptase-2-dependent HFE protein cleavage. In addition, no indication of HFE protein cleavage was seen in iron-deficient rats, whereas the full-length matriptase-2 protein content in the same animals was significantly increased. These results suggest that HFE is probably not a major physiological target of matriptase-2. NEW & NOTEWORTHY Feeding of iron-deficient diet for 4 wk decreased liver HFE protein content in both mice and rats, suggesting that decreased HFE-dependent signaling may contribute to hepcidin downregulation in iron deficiency. There was no difference in HFE protein band appearance between matriptase-2-mutated mask mice and wild-type mice, indicating that HFE is probably not a major physiological substrate of matriptase-2-mediated protease activity in vivo.
尽管遗传性血色素沉着症与 HFE 基因突变之间的关系在 20 多年前就已被发现，但有关 HFE 蛋白表达的体内调控信息仍然有限。本研究的目的是通过免疫印迹法确定铁缺乏时小鼠和大鼠肝脏 HFE 蛋白含量的反应。尽管未能成功观察到整个肝匀浆中的 HFE 蛋白，但可以在肝微粒体或质膜富集部分检测到 HFE。用缺铁饮食喂养 5 周龄雄性 C57BL/6 小鼠 4 周后，肝铁含量、肝 Hamp 表达以及肝 HFE 蛋白含量显著下降。用缺铁饮食喂养 4 周的大鼠也表现出肝 Hamp 表达和肝 HFE 蛋白含量显著下降。这些结果表明，在长期缺铁状态下，HFE 依赖性信号的下调可能导致 Hamp 基因表达下调。最近有人提出，HFE 蛋白可能是组织蛋白酶 2（一种在铁难治性缺铁性贫血中突变的肝细胞蛋白酶）的潜在靶点。然而，对 Tmprss6 突变的 mask 小鼠肝脏中的 HFE 蛋白进行免疫印迹分析并未显示出依赖于 matriptase-2 的 HFE 蛋白裂解的证据。此外，在缺铁大鼠中也没有观察到 HFE 蛋白裂解的迹象，而同一动物中的全长 matriptase-2 蛋白含量显著增加。这些结果表明，HFE 可能不是 matriptase-2 的主要生理靶点。新的和值得注意的是，用缺铁饮食喂养 4 周会降低小鼠和大鼠肝脏中的 HFE 蛋白含量，这表明 HFE 依赖性信号的降低可能导致铁缺乏时 hepcidin 的下调。matriptase-2 突变的 mask 小鼠和野生型小鼠的 HFE 蛋白条带外观没有差异，这表明 HFE 可能不是体内 matriptase-2 介导的蛋白酶活性的主要生理底物。
