MediCity Research Laboratory and Department of Medical Microbiology and Immunology, University of Turku, Turku, Finland.
Turku PET Centre, University of Turku, Turku, Finland.
Blood. 2011 Sep 29;118(13):3725-33. doi: 10.1182/blood-2010-09-311076. Epub 2011 Aug 5.
Leukocyte migration to sites of inflammation is regulated by several endothelial adhesion molecules. Vascular adhesion protein-1 (VAP-1) is unique among the homing-associated molecules as it is both an enzyme that oxidizes primary amines and an adhesin. Although granulocytes can bind to endothelium via a VAP-1-dependent manner, the counter-receptor(s) on this leukocyte population is(are) not known. Here we used a phage display approach and identified Siglec-9 as a candidate ligand on granulocytes. The binding between Siglec-9 and VAP-1 was confirmed by in vitro and ex vivo adhesion assays. The interaction sites between VAP-1 and Siglec-9 were identified by molecular modeling and confirmed by further binding assays with mutated proteins. Although the binding takes place in the enzymatic groove of VAP-1, it is only partially dependent on the enzymatic activity of VAP-1. In positron emission tomography, the ⁶⁸Gallium-labeled peptide of Siglec-9 specifically detected VAP-1 in vasculature at sites of inflammation and cancer. Thus, the peptide binding to the enzymatic groove of VAP-1 can be used for imaging conditions, such as inflammation and cancer.
白细胞向炎症部位的迁移受几种内皮细胞黏附分子的调节。血管黏附蛋白-1（VAP-1）在归巢相关分子中是独一无二的，因为它既是一种氧化伯胺的酶，也是一种黏附素。尽管粒细胞可以通过依赖 VAP-1 的方式与内皮细胞结合，但这种白细胞群体的相应受体尚不清楚。在这里，我们使用噬菌体展示技术，鉴定 Siglec-9 是粒细胞上的一个候选配体。Siglec-9 与 VAP-1 之间的结合通过体外和离体黏附实验得到了证实。通过分子建模确定了 VAP-1 和 Siglec-9 之间的相互作用位点，并通过进一步的与突变蛋白的结合实验得到了确认。虽然结合发生在 VAP-1 的酶槽中，但它只部分依赖于 VAP-1 的酶活性。在正电子发射断层扫描中，Siglec-9 的 ⁶⁸Ga 标记肽特异性地在炎症和癌症部位的血管中检测到 VAP-1。因此，与 VAP-1 的酶槽结合的肽可用于成像条件，如炎症和癌症。
