Capillary Morphogenesis Gene 2 protein (CMG2) is a transmembrane, integrin-like receptor and the primary receptor for the anthrax toxin. CMG2 also plays a role in angiogenic processes. However, the molecular mechanism that mediates the observed CMG2-related angiogenic effects is not fully elucidated. Previous studies have reported that CMG2 binds type IV collagen (Col-IV), a vital component of the vascular basement membrane, as well as other ECM proteins. Here, we further characterize the interaction between CMG2 and individual peptides from Col-IV and explore the effects of this interaction on angiogenesis. Using a peptide array, we observed that CMG2 preferentially binds peptide fragments of the NC1 (noncollagenous domain 1) domains of Col-IV. These domains are also known as the fragments arresten (from the α1 chain) and canstatin (from the α2 chain) and have documented antiangiogenic properties. A second peptide array was probed to map a putative peptide-binding epitope onto the Col-IV structure. A top hit from the initial array, a canstatin-derived peptide, binds to the CMG2 ligand-binding von Willebrand factor A (vWA) domain with a submicromolar affinity (peptide S16, Kd = 400 ± 200 nM). This peptide competes with anthrax protective antigen (PA) for CMG2 binding and does not bind CMG2 in the presence of EDTA. Together these data suggest that, like PA, S16 interacts with CMG2 at the metal-ion dependent adhesion site (MIDAS) of its vWA domain. CMG2 specifically mediates endocytic uptake of S16; both CMG2-/- endothelial cells and WT cells treated with PA show markedly reduced S16 uptake. Furthermore, S16 dramatically reduces directional endothelial cell migration with no impact on cell proliferation. These data demonstrate that this canstatin-derived peptide acts via CMG2 to elicit a marked effect on a critical process required for angiogenesis.

中文翻译：

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Canstatin衍生肽可深入了解毛细血管形态发生基因2在血管生成调节和基质摄取中的作用。

毛细管形态发生基因2蛋白（CMG2）是跨膜，整联蛋白样受体，是炭疽毒素的主要受体。CMG2在血管生成过程中也起作用。但是，尚未完全阐明介导观察到的CMG2相关血管生成作用的分子机制。先前的研究报道CMG2结合IV型胶原（Col-IV）和其他ECM蛋白，IV型胶原是血管基底膜的重要组成部分。在这里，我们进一步表征CMG2和Col-IV的各个肽之间的相互作用，并探讨这种相互作用对血管生成的影响。使用肽阵列，我们观察到CMG2优先结合Col-IV的NC1（非胶原结构域1）结构域的肽片段。这些结构域也被称为阻滞剂片段（来自α1链）和坎他汀（来自α2链），并具有已证明的抗血管生成特性。探测第二肽阵列以将推定的肽结合表位定位到Col-IV结构上。初始阵列中的最畅销品是一种来自他汀类药物的肽，其以亚微摩尔亲和力（肽S16，Kd = 400±200 nM）与CMG2配体结合von Willebrand因子A（vWA）域结合。该肽与炭疽保护性抗原（PA）竞争CMG2结合，在EDTA存在下不结合CMG2。这些数据共同表明，与PA一样，S16在其vWA域的金属离子依赖性粘附位点（MIDAS）与CMG2相互作用。CMG2特异性介导S16的内吞摄取。用PA处理的CMG2-/-内皮细胞和WT细胞均显示S16摄取显着降低。此外，S16极大地减少了定向内皮细胞迁移，而对细胞增殖没有影响。这些数据表明，这种源自坎他汀的肽通过CMG2发挥作用，对血管生成所需的关键过程产生了明显的影响。