School of Biological Sciences, College of Natural Sciences, Seoul National University, Seoul 151-742, Korea.
J Neurosci. 2013 Jul 31;33(31):12728-38. doi: 10.1523/JNEUROSCI.0698-13.2013.
Katanin is a heterodimeric enzyme that severs and disassembles microtubules. While the p60 subunit has the enzyme activity, the p80 subunit regulates the p60 activity. The microtubule-severing activity of katanin plays an essential role in axonal growth. However, the mechanisms by which neuronal cells regulate the expression of katanin-p60 remains unknown. Here we showed that USP47 and C terminus of Hsp70-interacting protein (CHIP) antagonistically regulate the stability of katanin-p60 and thereby axonal growth. USP47 was identified as a katanin-p60-specific deubiquitinating enzyme for its stabilization. We also identified CHIP as a ubiquitin E3 ligase that promotes proteasome-mediated degradation of katanin-p60. Moreover, USP47 promoted axonal growth of cultured rat hippocampal neurons, whereas CHIP inhibited it. Significantly, treatment with basic fibroblast growth factor (bFGF), an inducer of axonal growth, increased the levels of USP47 and katanin-p60, but not CHIP. Consistently, bFGF treatment resulted in a marked decrease in the level of ubiquitinated katanin-p60 and thereby in the promotion of axonal growth. On the other hand, the level of USP47, but not CHIP, decreased concurrently with that of katanin-p60 as axons reached their target cells. These results indicate that USP47 plays a crucial role in the control of axonal growth during neuronal development by antagonizing CHIP-mediated katanin-p60 degradation.
卡坦丁是一种异源二聚体酶，可切断和解聚微管。虽然 p60 亚基具有酶活性，但 p80 亚基调节 p60 活性。卡坦丁的微管切断活性在轴突生长中起着至关重要的作用。然而，神经元细胞调节卡坦丁-p60 表达的机制尚不清楚。在这里，我们表明 USP47 和热休克蛋白 70 相互作用蛋白 (CHIP) 的 C 末端拮抗调节卡坦丁-p60 的稳定性，从而调节轴突生长。USP47 被鉴定为一种卡坦丁-p60 特异性去泛素化酶，可稳定其表达。我们还发现 CHIP 是一种泛素 E3 连接酶，可促进蛋白酶体介导的卡坦丁-p60 降解。此外，USP47 促进培养的大鼠海马神经元的轴突生长，而 CHIP 则抑制其生长。值得注意的是，碱性成纤维细胞生长因子 (bFGF) 作为轴突生长的诱导剂，可增加 USP47 和卡坦丁-p60 的水平，但不增加 CHIP 的水平。一致地，bFGF 处理导致泛素化卡坦丁-p60 的水平显著降低，从而促进轴突生长。另一方面，随着轴突到达靶细胞，USP47 的水平（而非 CHIP）与卡坦丁-p60 的水平同时降低。这些结果表明，USP47 通过拮抗 CHIP 介导的卡坦丁-p60 降解，在神经元发育过程中控制轴突生长中发挥关键作用。
