Glycochemistry and Glycobiology Laboratory, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.
Biochem J. 2011 Dec 1;440(2):273-82. doi: 10.1042/BJ20110167.
Heparanase is involved in the cleavage of the HS (heparan sulfate) chain of HSPGs (HS proteoglycans) and hence participates in remodelling of the ECM (extracellular matrix) and BM (basement membrane). In the present study we have shown that NGF (nerve growth factor) promoted nuclear enrichment of EGR1 (early growth response 1), a transcription factor for heparanase, and markedly induced heparanase expression in rat adrenal pheochromocytoma (PC12) cells. K252a, an antagonist of the NGF receptor TrkA (tyrosine kinase receptor A), decreased heparanase protein expression induced by NGF in PC12 cells. Suramin, a heparanase inhibitor, decreased heparanase in PC12 cells and blocked NGF-induced PC12 neuritogenesis. Stable overexpression of heparanase activated p38 MAPK (mitogen-activated protein kinase) by phosphorylation and enhanced the neurite outgrowth induced by NGF, whereas knock down of heparanase impaired this process. However, overexpression of latent pro-heparanase with a Y156A mutation still led to enhanced NGF-induced neurite outgrowth and increased p38 MAPK phosphorylation. Inhibition of p38 MAPK by SB203580 suppressed the promotion of NGF-induced neuritogenesis by the wild-type and mutant heparanase. The impaired differentiation by knock down of heparanase could be restored by transfection of wild-type or mutant heparanase in PC12 cells. The results of the present study suggest that heparanase, at least in the non-enzymatic form, may promote NGF-induced neuritogenesis via the p38 MAPK pathway.
乙酰肝素酶参与 HSPGs（硫酸乙酰肝素蛋白聚糖）中 HS（硫酸乙酰肝素）链的裂解，因此参与 ECM（细胞外基质）和 BM（基底膜）的重塑。在本研究中，我们已经表明，NGF（神经生长因子）促进 EGR1（早期生长反应 1）的核富集，EGR1 是乙酰肝素酶的转录因子，并显著诱导大鼠肾上腺嗜铬细胞瘤（PC12）细胞中乙酰肝素酶的表达。NGF 受体 TrkA（酪氨酸激酶受体 A）的拮抗剂 K252a 降低了 NGF 在 PC12 细胞中诱导的乙酰肝素酶蛋白表达。乙酰肝素酶抑制剂苏拉明降低了 PC12 细胞中的乙酰肝素酶，并阻断了 NGF 诱导的 PC12 神经元突起形成。乙酰肝素酶的稳定过表达通过磷酸化激活 p38 MAPK（丝裂原激活蛋白激酶），并增强 NGF 诱导的神经突生长，而乙酰肝素酶的敲低则损害了这一过程。然而，具有 Y156A 突变的潜伏前乙酰肝素酶的过表达仍然导致增强的 NGF 诱导的神经突生长和增加的 p38 MAPK 磷酸化。通过 SB203580 抑制 p38 MAPK 抑制了野生型和突变型乙酰肝素酶对 NGF 诱导的神经突发生的促进作用。通过在 PC12 细胞中转染野生型或突变型乙酰肝素酶，可以恢复乙酰肝素酶敲低导致的分化受损。本研究的结果表明，乙酰肝素酶，至少在非酶形式下，可能通过 p38 MAPK 途径促进 NGF 诱导的神经突发生。
