Mast Jacob F, Leach Edmund A E, Thompson Thomas B
Department of Molecular and Cellular Biosciences, University of Cincinnati.
bioRxiv. 2023 Sep 2:2023.09.01.555965. doi: 10.1101/2023.09.01.555965.
Hepcidin, a peptide hormone that negatively regulates iron metabolism, is expressed by bone morphogenetic protein (BMP) signaling. Erythroferrone (ERFE) is an extracellular protein that binds and inhibits BMP ligands, thus positively regulating iron import by indirectly suppressing hepcidin. This allows for rapid erythrocyte regeneration after blood loss. ERFE belongs to the C1Q/TNF related protein (CTRP) family and is suggested to adopt multiple oligomeric forms: a trimer, a hexamer, and a high molecular weight species. The molecular basis for how ERFE binds BMP ligands and how the different oligomeric states impact BMP inhibition are poorly understood. In this study, we demonstrated that ERFE activity is dependent on the presence of stable dimeric or trimeric ERFE, and that larger species are dispensable for BMP inhibition. Additionally, we used an approach to identify a helix, termed the ligand binding domain (LBD), that was predicted to bind BMPs and occlude the type I receptor pocket. We provide evidence that the LBD is crucial for activity through luciferase assays and surface plasmon resonance (SPR) analysis. Our findings provide new insight into how ERFE oligomerization impacts BMP inhibition, while identifying critical molecular features of ERFE essential for binding BMP ligands.
铁调素是一种对铁代谢起负调控作用的肽类激素，由骨形态发生蛋白（BMP）信号通路表达。促红细胞生成素铁调节蛋白（ERFE）是一种细胞外蛋白，它能结合并抑制BMP配体，从而通过间接抑制铁调素对铁的摄取起正调控作用。这使得失血后红细胞能够快速再生。ERFE属于C1Q/TNF相关蛋白（CTRP）家族，被认为具有多种寡聚形式：三聚体、六聚体和高分子量形式。目前对于ERFE如何结合BMP配体以及不同寡聚状态如何影响BMP抑制作用的分子基础了解甚少。在本研究中，我们证明ERFE的活性依赖于稳定的二聚体或三聚体ERFE的存在，而更大的形式对于BMP抑制作用并非必需。此外，我们采用一种方法鉴定出一个螺旋结构，称为配体结合结构域（LBD），预计它能结合BMP并封闭I型受体口袋。我们通过荧光素酶测定和表面等离子体共振（SPR）分析提供证据表明LBD对活性至关重要。我们的研究结果为ERFE寡聚化如何影响BMP抑制作用提供了新的见解，同时确定了ERFE结合BMP配体所必需的关键分子特征。
