Regulation of the stepwise proteolytic cleavage and secretion of PDGF-B by the proprotein convertases
Regulation of the stepwise proteolytic cleavage and secretion of PDGF-B by the proprotein convertases
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DOI：
10.1038/sj.onc.1208838
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发表时间：
2005-10-20
期刊：
影响因子：
8
通讯作者：
Khatib, AM
中科院分区：
文献类型：
--
作者：
Siegfried, G;Basak, A;Khatib, AM
血小板源性生长因子-B（PDGF-B）对于正常组织生长和维持是重要的，并且其过表达已经与包括癌症、纤维化疾病和动脉粥样硬化在内的若干疾病相关联。在这里，我们表明，作为前体合成，proPDGF-B转化为成熟形式的蛋白水解裂解在两个网站和其N-末端裂解是在其C-末端加工的先决条件。第一次切割发生在RGRR残基（81）向下箭头处，第二次切割靠近残基ARPVT（190），就在对PDGF-B保留到细胞表面至关重要的C-末端氨基酸序列之前。用proPDGF-B和不同的PC成员共转染弗林蛋白酶缺陷细胞系LoVo-C5，显示弗林蛋白酶、PACE 4、PC 5和PC 7是候选的proPDGF-B转化酶。这一发现与模拟proPDGF-B切割位点的合成肽的体外双链断裂一致。proPDGF-B的加工被RGRR（81）向下箭头序列的定点诱变和各种PC抑制剂阻断。PDGF-A和/或PDGF-B转化酶位点的突变揭示了A和B链的加工是形成成熟的PDGF-B二聚体所必需的，并且B链的加工控制分泌的和基质结合的PDGF-BB形式的水平。我们的研究结果强调了在RGRR（81）向下箭头序列处proPDGF-B的转化酶定向加工对于PDGF-B成熟和分泌的重要性。
Platelet-derived growth factor-B (PDGF-B) is important for normal tissue growth and maintenance and its overexpression has been linked to several diseases, including cancer, fibrotic disease and atherosclerosis. Here, we show that synthesized as a precursor, proPDGF-B is converted to a mature form by proteolytic cleavage at two sites and its N-terminal cleavage is a prerequisite for processing at its C-terminus. The first cleavage occurs at residues RGRR(81)down arrow, and the second cleavage close to residues ARPVT(190), just before the C-terminal amino-acid sequence crucial for PDGF-B retention to cell surface. Cotransfection of a Furin-deficient cell line LoVo-C5 with proPDGF-B and different PC members revealed that Furin, PACE4, PC5, and PC7 are candidate proPDGF-B convertases. This finding is consistent with the in vitro digestions of a synthetic peptide mimicking the cleavage site of proPDGF-B. The processing of proPDGF-B is blocked by site-directed mutagenesis of the RGRR(81)down arrow sequence and by various PC inhibitors. Mutation of the PDGF-A and/or PDGF-B convertase sites, revealed that processing of both A and B chains is required for the formation of mature PDGF-B dimers and that the processing of the B chain controls the level of secreted and matrix-bound PDGF-BB forms. Our findings emphasize the importance of the convertase-directed processing of proPDGF-B at the RGRR(81)down arrow sequence for PDGF-B maturation and secretion.