人類endosialin蛋白最早在1992年利用單株抗體FB5針對腫瘤或正常組織進行免疫染色而被發現。在文獻中指出，endosailin只表現於腫瘤組織之內皮層，正常的組織切片則為陰性反應。人類endosialin蛋白為由757個氨基酸組成分子量大小為165 kDa的第一型膜蛋白，具有六個功能性區域，包括一個C-type lectin-like區域、一個和Sushi/ccp/scr pattern類似的區域、三個重複的EGF-like區域、一個sialomucin-like的區域，緊接著為穿膜區和位於細胞內的短片段。後續的文獻發現人類endosialin蛋白具有高度的唾液性、O-link的醣化作用，所以歸類為sialomucin-like蛋白家族。而其N端的360個胺基酸和一個與調控凝血作用有關的膜蛋白-人類凝血酶調節素 (thrombomodulin) 具有39 %的同源性，同時也與補體受器-CD93 (C1qRp) 具有33 %的同源。本實驗室近期的研究指出人類凝血脢調節素可作為細胞與細胞間連結的分子，而其EGF-like到serine/threonine-rich區域的重組蛋白則為一個促進血管新生的因子。由結構上的同緣關係，我們測試人類endosialin蛋白是否具有類似調控細胞細胞連結、血管新生或腫瘤生成的功能。我們發現與轉染載體的控制組細胞相比，穩定持續表現endosialin蛋白之人類角質細胞株雖然在增生能力上並不受影響，但在Boyden chamber和細胞對collagen type I這幾個基質之spreading能力的實驗中卻發現趨化爬行、細胞貼附及spreading的能力受到抑制。我們同時也表現了具有三個EGF-like重複片段的重組蛋白 (rhESD2)，發現此重組蛋白對刺激人類臍帶靜脈內皮細胞 (HUVECs) 的增生能力不明顯，而對於細胞的趨化爬行卻具有明顯的誘導作用。由以上的結果暗示人類endosialin蛋白不僅參與細胞與細胞間或細胞對細胞外間質貼附的連結，更調控了內皮細胞的趨化爬行能力。

　Human endosialin was first discovered in 1992 by immunostaining with a monoclonal antibody FB5 detecting tumor and normal tissues. It was reported to be expressed in tumor endothelium but not in normal endothelium. Human endosialin is a type I trans-membrane protein of 757 amino acids with a molecular mass of 165 kDa. It is composed of six distinct domains including a C-type lectin-like domain, one domain with similarity to the Sushi/ccp/scr pattern, and three EGF-like repeats, followed by a mucin-like region, a transmembrane segment, and a short cytoplasmic tail. Subsequent analysis showed that the endosialin carried abundantly sialylated, O-linked oligosaccharides, placing it in the group of sialomucin-like molecules. The N-terminal 360 amino acids of endosialin showed 39 % homology to thrombomodulin（TM）, a receptor involved in regulating blood coagulation, and 33 % to complement receptor C1qRp. In our recent study, TM can function as a cell-cell adhesion molecule and its EGF-like domain to serine/threonine rich domain could function as an angiogenic factor. This structural kinship indicates a function for endosialin involved in cell adhesion, angiogenesis and tumor progression. In this report, using endosialin stably expressed HaCaT cells, we found that the stable clones expressing endosialin exhibited similar proliferative rate with the vector control. However, using Boyden chamber migration assay and cell spreading assay on collagen type I matrix, the clones stably expressing endosialin showed suppressed migratory, adhesive and spreading ability compared to the vector control. We also expressed the recombinant human endosialin protein consisting of three EGF-like domains（rhESD2）. Recombinant rhESD2 slightly enhanced the proliferative rate and significantly induced the chemotatic migration of human umbilical vein endothelial cells（HUVECs）. These findings revealed that human endosialin might involve not only in the cell-cell interaction and adhesion but also modulate cell migration of endothelial cells.

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