Physiology and pathology of the ubiquitin-mediated quality control system

1. HOIL-1泛素连接酶的功能分析。HOIL-1的靶点识别机制IRP 2中的血红素调节基序（HRM）是IRP 2的血红素结合位点。由血红素结合到HRM和氧产生的IRP 2的氧化修饰被HOIL-1识别，这导致IRP 2泛素化。从这些分析中，我们展示了一种新的铁感应机制，其中细胞通过血红素感应铁浓度的变化（Nature Cell Biology，2003; Molecular Cell，2005）。含有HOIL-1的连接酶复合物的功能LUBAC泛素连接酶复合物由HOIP和HOIL-1 L（HOIL-1的同种型）组成，产生新的多聚泛素链，其中泛素的C-末端Gly残基与泛素的N-末端Met的α-氨基缀合（EMBO J. 2006）。HOIL-1连接酶的生理作用我们已经证明LUBAC通过NEMO的线性泛素化选择性地激活NF-κ B通路（提交中）.我们表明，SCF连接<Fbs1>酶选择性地识别N-连接糖链的壳二糖部分，该识别机制适用于选择性识别变性糖蛋白（Nature，2002; Nat. Strut.摩尔生物学：2004年）。我们已经产生了在神经元中表达IRP 2的转基因小鼠（IRP 2 Tg），并分析了神经退行性疾病中铁代谢紊乱所产生的氧化应激的作用。虽然没有观察到大量的铁积累，但反应性Fe 2+在IRP 2 Tg神经元中积累，引起这些细胞的氧化损伤。此外，在老年IRP 2 Tg小鼠中观察到神经元丢失和共济失调（提交中）。

1. Functional analyses of the HOIL-1 ubiquitin ligasea. Mechanism of target recognition by HOIL-1 A heme-regulatory motif (HRM) in IRP2 is the heme-binding site of IRP2. Oxidative modification of IRP2, generated by heme bound to the HRM and oxygen is recognized by HOIL-1, which leads to IRP2 ubiquitination. From these analyses, we show a novel iron-sensing mechanism, in which cells are sensing changes in iron concentration through heme (Nature Cell Biology, 2003; Molecular Cell, 2005).b. Function of the ligase complex containing HOIL-1 The LUBAC ubiquitin ligase complex, composed of HOIP and HOIL-1L, an isoform of HOIL-1, generates a novel polyubiquitin chain, in which C-terminal Gly residue of ubiquitin is conjugated to a-amino group of N-terminal Met of ubiquitin (EMBO J. 2006).c. Physiological roles of the HOIL-1 ligase We have shown that LUBAC selectively activates the NF-kB pathway through linear ubiquitination of NEMO (In submission).2. We showed that the SCF^<Fbs1> ligase selectively recognizes the chitobiose portion of the N-linked sugar chain, which recognition mechanism is suitable for selective recognition of denatured glycoproteins (Nature, 2002; Nat. Strut. Mol. Biol., 2004).3. We have generated transgenic mice expressing IRP2 in neuron (IRP2 Tg) and analyzed the roles of oxidative stress generated by perturbation of iron metabolism in neurodegenerative disorders. Although massive iron accumulation was not observed, reactive Fe 2+ was accumulated in IRP2 Tg neurons, which provokes oxidative damages in those cells. Also, neuronal loss and ataxia was observed in aged IRP2 Tg mice (In submission).