Proteolytic maturation and activation of autotaxin (NPP2), a secreted metastasis-enhancing lysophospholipase D
Proteolytic maturation and activation of autotaxin (NPP2), a secreted metastasis-enhancing lysophospholipase D
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DOI：
10.1242/jcs.02438
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发表时间：
2005-07-15
影响因子：
4
通讯作者：
Bollen, M
中科院分区：
文献类型：
--
作者：
Jansen, S;Stefan, C;Bollen, M
自分泌运动因子 (NPP2) 是一种细胞外蛋白，在多种恶性肿瘤（包括乳腺癌和肺癌）中表达上调。它能有效刺激细胞增殖、细胞运动和血管生成，这是由于其内在的溶血磷脂酶-D 活性产生脂质介质溶血磷脂酸和 1-磷酸鞘氨醇。基于其与更好表征的核苷酸焦磷酸酶/磷酸二酯酶 NPP1 的结构相似性，人们一直认为 NPP2 也是作为 II 型整合膜蛋白合成的，并且细胞外 NPP2 是由该膜前体产生的。然而，我们在这里通过结构域交换和诱变实验以及 N 端蛋白质测序表明，NPP2 实际上是作为前酶原合成的，并且蛋白水解加工的蛋白质是分泌的。信号肽酶去除 27 个残基的信号肽后，NPP2 随后被原蛋白转化酶 (PC) 裂解。 PC 去除 N 末端八肽与 NPP2 作为溶血磷脂酶 D 的活性增强有关。这些关于 NPP2 成熟的新见解也对 NPP2 抑制剂作为潜在抗癌药物的开发具有影响。
Autotaxin (NPP2) is an extracellular protein that is upregulated in various malignancies, including breast and lung cancer. It potently stimulates cell proliferation, cell motility and angiogenesis, which is accounted for by its intrinsic lysophospholipase-D activity that generates the lipid mediators lysophosphatidic acid and sphingosine-1-phosphate. Based on its structural similarities with the better characterized nucleotide pyrophosphatase/ phosphodiesterase NPP1, it has always been assumed that NPP2 is also synthesized as a type-II integral membrane protein and that extracellular NPP2 is generated from this membrane precursor. We show here, however, using domain swapping and mutagenesis experiments as well as N-terminal protein sequencing, that NPP2 is actually synthesized as a pre-pro-enzyme and that the proteolytically processed protein is secreted. Following the removal of a 27-residue signal peptide by the signal peptidase, NPP2 is subsequently cleaved by proprotein convertases (PCs). The removal of an N-terminal octapeptide by PCs is associated with an enhanced activity of NPP2 as a lysophospholipase D. These novel insights in the maturation of NPP2 have also implications for the development of NPP2 inhibitors as potential anti-cancer agents.