Gurwitz D, Cunningham D D
Department of Microbiology and Molecular Genetics, College of Medicine, University of California, Irvine 92717.
J Cell Physiol. 1990 Jan;142(1):155-62. doi: 10.1002/jcp.1041420119.
Protease nexin-1 (PN-1) is a protein proteinase inhibitor recently shown to be identical with the glial-derived neurite-promoting factor or glial-derived nexin. It has been shown to promote neurite outgrowth in neuroblastoma cells and in sympathetic neurons. The present experiments were designed to further test the hypothesis that this activity on neuroblastoma cells is due to its ability to complex and inhibit thrombin. It has been suggested that PN-1:thrombin complexes might mediate the neurite outgrowth activity of PN-1. However, the present studies showed that such complexes, unlike free PN-1, did not promote neurite outgrowth. The neurite outgrowth activity of PN-1 was only detected in the presence of thrombin or serum (which contains thrombin). PN-1 did not affect the rate or extent of neurite outgrowth that occurred when neuroblastoma cells were placed in serum-free medium. Retraction of neurites by thrombin was indistinguishable in cells whose neurites had been extended in the presence or absence of PN-1. The neurite-promoting activity of PN-1 was inhibited by an anti-PN-1 monoclonal antibody, which blocks its capacity to complex serine proteinases. The plasma thrombin inhibitor, antithrombin III, stimulated neurite outgrowth but only when its thrombin inhibitory activity was accelerated by heparin. The neurite outgrowth activity of both antithrombin III and PN-1 corresponded to their inhibition of thrombin. Together, these observations show that PN-1 promotes neurite outgrowth from neuroblastoma cells by inhibiting thrombin and suggest that this depends on the ability of thrombin to retract neurites.
蛋白酶连接素-1（PN-1）是一种蛋白质蛋白酶抑制剂，最近被证明与神经胶质细胞衍生的神经突促进因子或神经胶质细胞衍生的连接素相同。它已被证明能促进神经母细胞瘤细胞和交感神经元的神经突生长。本实验旨在进一步验证这一假说，即其对神经母细胞瘤细胞的这种活性是由于它能够结合并抑制凝血酶。有人提出，PN-1：凝血酶复合物可能介导了PN-1的神经突生长活性。然而，目前的研究表明，与游离的PN-1不同，这种复合物并不能促进神经突生长。只有在存在凝血酶或血清（其中含有凝血酶）的情况下，才能检测到PN-1的神经突生长活性。当将神经母细胞瘤细胞置于无血清培养基中时，PN-1不会影响神经突生长的速率或程度。在神经突生长过程中，无论是否存在PN-1，凝血酶对神经突的回缩作用并无差异。PN-1的神经突促进活性被一种抗PN-1单克隆抗体所抑制，该抗体可阻断其结合丝氨酸蛋白酶的能力。血浆凝血酶抑制剂抗凝血酶III能刺激神经突生长，但只有在肝素加速其凝血酶抑制活性时才会如此。抗凝血酶III和PN-1的神经突生长活性与其对凝血酶的抑制作用相对应。这些观察结果共同表明，PN-1通过抑制凝血酶来促进神经母细胞瘤细胞的神经突生长，并提示这取决于凝血酶回缩神经突的能力。
