Smith L L, Greenfield B W, Aruffo A, Giachelli C M
Department of Pathology, University of Washington, Seattle 98195, USA.
J Cell Biochem. 1999 Apr 1;73(1):20-30. doi: 10.1002/(sici)1097-4644(19990401)73:1<20::aid-jcb3>3.0.co;2-3.
Osteopontin is a secreted glycoprotein with adhesive and migratory functions. Cellular interactions with osteopontin are mediated through integrin receptors which recognize the RGD domain. Recently, CD44, a non-integrin, multifunctional adhesion molecule was identified as an osteopontin receptor. CD44 is a ubiquitous surface molecule that exists as a number of different isoforms, generated by alternative splicing. To analyze which forms of CD44 mediate binding to osteopontin, we used the standard form of CD44 as CD44-human immunoglobulin fusion proteins and several splice variants in enzyme-linked immunosorbant assays. Multiple preparations of osteopontin were used including native osteopontin derived from smooth muscle cells, human urinary osteopontin, full-length recombinant osteopontin, and two recombinant osteopontin fragments expected to be formed following thrombin cleavage. Our data show that although the CD44-hlg fusion proteins could interact with hyaluronic acid as expected, there was no interaction between CD44H, CD44E, CD44v3,v8-v10, or CD44v3 with osteopontin. These studies suggest that CD44-osteopontin interactions may not be common in vivo and may be limited to a specific CD44 isoform(s), and/or a particular modified form of osteopontin.
骨桥蛋白是一种具有黏附与迁移功能的分泌型糖蛋白。细胞与骨桥蛋白的相互作用是通过识别RGD结构域的整合素受体介导的。最近，CD44（一种非整合素多功能黏附分子）被确定为骨桥蛋白受体。CD44是一种普遍存在的表面分子，以多种不同的异构体形式存在，这些异构体由可变剪接产生。为了分析哪种形式的CD44介导与骨桥蛋白的结合，我们在酶联免疫吸附试验中使用了CD44的标准形式作为CD44-人免疫球蛋白融合蛋白以及几种剪接变体。使用了多种骨桥蛋白制剂，包括源自平滑肌细胞的天然骨桥蛋白、人尿骨桥蛋白、全长重组骨桥蛋白以及预期在凝血酶切割后形成的两种重组骨桥蛋白片段。我们的数据表明，尽管CD44-hlg融合蛋白可以如预期那样与透明质酸相互作用，但CD44H、CD44E、CD44v3,v8-v10或CD44v3与骨桥蛋白之间没有相互作用。这些研究表明，CD44与骨桥蛋白之间的相互作用在体内可能并不常见，可能仅限于特定的CD44异构体和/或特定修饰形式的骨桥蛋白。
