Regulation of cellular iron metabolism: Iron-dependent degradation of IRP by SCFFBXL5 ubiquitin ligase

Because of essentiality and toxicity of iron in our body, iron metabolism is tightly regulated in cells. In mammalian cells, iron regulatory protein 1 and 2 (IRP1 and IRP2) are the central regulators of cellular iron metabolism. IRPs regulate iron metabolism by interacting with the RNA stem-loop structures, iron-responsive elements (IREs), found on the transcripts encoding proteins involved in iron metabolism only in iron depleted condition. It is also well-known that the ubiquitin system plays central roles in cellular iron regulation because both IRPs having the IRE binding activity are recognized and ubiquitinated by the SCFFBXL5 ubiquitin ligase in condition of iron-replete. FBXL5, which is a substrate recognition subunit of SCFFBXL5, senses iron availability via its hemerythrin-like domain. In this small article, current understanding of the roles of SCFFBXL5-mediated degradation of IRPs played in cellular iron metabolism is discussed.