Miller Shyra J, Li Hongzhen, Rizvi Tilat A, Huang Yuan, Johansson Gunnar, Bowersock Jason, Sidani Amer, Vitullo John, Vogel Kristine, Parysek Linda M, DeClue Jeffrey E, Ratner Nancy
Department of Cell Biology, Neurobiology and Anatomy, University of Cincinnati College of Medicine, 231 Bethesda Avenue, Cincinnati, OH 45267-0521, USA.
Mol Cell Biol. 2003 Mar;23(6):2213-24. doi: 10.1128/MCB.23.6.2213-2224.2003.
Loss of axonal contact characterizes Schwann cells in benign and malignant peripheral nerve sheath tumors (MPNST) from neurofibromatosis type 1 (NF1) patients. Tumor Schwann cells demonstrate NF1 mutations, elevated Ras activity, and aberrant epidermal growth factor receptor (EGFR) expression. Using cDNA microarrays, we found that brain lipid binding protein (BLBP) is elevated in an EGFR-positive subpopulation of Nf1 mutant mouse Schwann cells (Nf1(-/-) TXF) that grows away from axons; BLBP expression was not affected by farnesyltransferase inhibitor, an inhibitor of H-Ras. BLBP was also detected in EGFR-positive cell lines derived from Nf1:p53 double mutant mice and human MPNST. BLBP expression was induced in normal Schwann cells following transfection with EGFR but not H-Ras12V. Furthermore, EGFR-mediated BLBP expression was not inhibited by dominant-negative H-Ras, indicating that BLBP expression is downstream of Ras-independent EGFR signaling. BLBP-blocking antibodies enabled process outgrowth from Nf1(-/-) TXF cells and restored interaction with axons, without affecting cell proliferation or migration. Following injury, BLBP expression was induced in normal sciatic nerves when nonmyelinating Schwann cells remodeled their processes. These data suggest that BLBP, stimulated by Ras-independent pathways, regulates Schwann cell-axon interactions in normal peripheral nerve and peripheral nerve tumors.
轴突接触丧失是1型神经纤维瘤病(NF1)患者良性和恶性周围神经鞘瘤(MPNST)中雪旺细胞的特征。肿瘤雪旺细胞表现出NF1突变、Ras活性升高和表皮生长因子受体(EGFR)表达异常。利用cDNA微阵列,我们发现脑脂质结合蛋白(BLBP)在Nf1突变小鼠雪旺细胞(Nf1(-/-) TXF)的EGFR阳性亚群中升高,该亚群远离轴突生长;BLBP表达不受法尼基转移酶抑制剂(一种H-Ras抑制剂)的影响。在源自Nf1:p53双突变小鼠和人MPNST的EGFR阳性细胞系中也检测到了BLBP。用EGFR而非H-Ras12V转染后,正常雪旺细胞中诱导了BLBP表达。此外,EGFR介导的BLBP表达不受显性负性H-Ras的抑制,表明BLBP表达在Ras非依赖性EGFR信号传导的下游。BLBP阻断抗体使Nf1(-/-) TXF细胞能够长出突起并恢复与轴突的相互作用,而不影响细胞增殖或迁移。损伤后,当无髓鞘雪旺细胞重塑其突起时,正常坐骨神经中诱导了BLBP表达。这些数据表明,由Ras非依赖性途径刺激的BLBP调节正常周围神经和周围神经肿瘤中雪旺细胞与轴突的相互作用。