Implication of the oligomeric state of the N-terminal PTX3 domain in cumulus matrix assembly.
Implication of the oligomeric state of the N-terminal PTX3 domain in cumulus matrix assembly.
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DOI：
10.1016/j.matbio.2011.05.002
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发表时间：
2011-06
期刊：
影响因子：
6.9
通讯作者：
Salustri, Antonietta
中科院分区：
文献类型：
--
作者：
Ievoli, Elena;Lindstedt, Ragnar;Inforzato, Antonio;Camaioni, Antonella;Palone, Francesca;Day, Anthony J.;Mantovani, Alberto;Salvatori, Giovanni;Salustri, Antonietta
正五聚蛋白3（PTX 3）在形成围绕排卵卵的卵丘的富含透明质酸的基质中起关键作用，所述基质是成功受精和雌性生育力所需的。PTX 3是一种多聚体蛋白，由八个相同的原聚体组成，通过非共价相互作用和二硫键的组合保持在一起。最近的研究结果表明，低聚状态的PTX 3是重要的稳定积云基质。由于PTX 3在卵丘中的作用在于其独特的N-末端序列，我们通过测试具有不同寡聚体排列的PTX 3重组N-末端区域（N_PTX 3）的不同Cys/Ser突变体促进Ptx 3缺失小鼠卵丘体外正常扩增的能力来进一步研究这个问题。在这里，我们报告的N_PTX 3的二聚体是无法拯救卵丘基质组织，和四聚体组装的蛋白质是完成这一功能所需的最小的寡聚状态。我们先前已经证明，PTX 3结合到IαI和TSG-6的HC上，这是卵丘基质形成所必需的，并且能够与透明质酸相互作用。有趣的是，在这里，我们通过固相结合实验表明，N_PTX 3的二聚体保留了与IαI和TSG-6结合的能力，这表明PTX 3的八聚体结构为这些配体中的每一个提供了多个结合位点。这些发现支持以下假设：PTX 3通过与IαI和/或TSG-6的多种HC相互作用交联HA聚合物，从而促进卵丘基质组织化。最近报道，N末端PTX 3四聚体寡聚化也是识别和抑制FGF 2所必需的。鉴于这种生长因子已在哺乳动物排卵前卵泡中检测到，我们想知道FGF 2是否会对卵丘扩张产生负面影响，而PTX 3也可能在体内拮抗其活性。我们发现，超过PTX 3结合能力的摩尔过量的FGF 2不影响体外卵丘基质形成，从而排除了这种可能性。总之，数据加强了PTX 3在基质中交联HA中充当节点分子的观点。
Pentraxin 3 (PTX3) plays a key role in the formation of the hyaluronan-rich matrix of the cumulus oophorus surrounding ovulated eggs that is required for successful fertilization and female fertility. PTX3 is a multimeric protein consisting of eight identical protomers held together by a combination of non-covalent interactions and disulfide bonds. Recent findings suggest that the oligomeric status of PTX3 is important for stabilizing the cumulus matrix. Because the role of PTX3 in the cumulus resides in the unique N-terminal sequence of the protomer, we investigated further this issue by testing the ability of distinct Cys/Ser mutants of recombinant N-terminal region of PTX3 (N_PTX3) with different oligomeric arrangement to promote in vitro normal expansion in cumuli from Ptx3-null mice. Here we report that the dimer of the N_PTX3 is unable to rescue cumulus matrix organization, and that the tetrameric assembly of the protein is the minimal oligomeric state required for accomplishing this function. We have previously demonstrated that PTX3 binds to HCs of IαI and TSG-6, which are essential for cumulus matrix formation and able to interact with hyaluronan. Interestingly, here we show by solid-phase binding experiments that the dimer of the N_PTX3 retains the ability to bind to both IαI and TSG-6, suggesting that the octameric structure of PTX3 provides multiple binding sites for each of these ligands. These findings support the hypothesis that PTX3 contributes to cumulus matrix organization by cross-linking HA polymers through interactions with multiple HCs of IαI and/or TSG-6. The N-terminal PTX3 tetrameric oligomerization was recently reported to be also required for recognition and inhibition of FGF2. Given that this growth factor has been detected in the mammalian preovulatory follicle, we wondered whether FGF2 negatively influences cumulus expansion and PTX3 may also serve in vivo to antagonize its activity. We found that a molar excess of FGF2, above PTX3 binding capacity, does not affect in vitro cumulus matrix formation thus ruling out this possibility. In conclusion, the data strength the view that PTX3 acts as a nodal molecule in cross-linking HA in the matrix.
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