ANTIBODIES TO SPARC INHIBIT ALBUMIN BINDING TO SPARC, GP60, AND MICROVASCULAR ENDOTHELIUM
ANTIBODIES TO SPARC INHIBIT ALBUMIN BINDING TO SPARC, GP60, AND MICROVASCULAR ENDOTHELIUM
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DOI：
10.1152/ajpheart.1992.263.6.h1872
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发表时间：
1992-12-01
影响因子：
--
通讯作者：
OH, P
中科院分区：
文献类型：
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作者：
SCHNITZER, JE;OH, P
白蛋白通过与内皮糖萼结合，充当毛细血管通透性的主要决定因素，并在通过质膜囊泡跨连续内皮的转胞吞作用中作为各种小分子的载体。已鉴定出几种白蛋白结合蛋白 (ABP)：三种膜相关 ABP，我们称之为 gp60、gp30 和 gp18，以及一种富含半胱氨酸的酸性分泌蛋白 (SPARC)。在本研究中，我们使用针对牛 SPARC (BON) 的抗血清来研究 ABP 之间可能的相互关系，以更好地了解它们在结合和转胞吞作用中的作用。 BON 不仅与培养的内皮细胞分泌的 SPARC 相互作用，而且还能识别培养的大鼠、人和牛内皮细胞裂解物中的 gp60。纯化的 SPARC 抑制 BON 与 gp60 的相互作用。 BON 免疫球蛋白 (Ig)G 特异性抑制白蛋白与 SPARC 和 gp60 提取物的结合。通过将 BON 预吸附到固定的 SPARC 上，可以消除这种影响。 BON 还通过与 gp60 的相互作用显着抑制白蛋白与培养的微血管内皮细胞的结合。还测试了抗 SPARC 肽血清，针对包含 SPARC NH2 末端区域的肽而产生的一种血清识别 SPARC 和 gp60，但不抑制白蛋白结合； gp30 和 gp18 不被任何这些抗 SPARC 抗体识别。这些结果表明 SPARC 和 gp60 是功能和免疫学相关的 ABP，可能具有共同的白蛋白结合域。 gp60 似乎是白蛋白与微血管内皮结合的主要介质。
Albumin, through its binding to the endothelial glycocalyx, functions as a major determinant of capillary permeability and as a carrier for various small molecules in its transcytosis across continuous endothelium via plasmalemmal vesicles. Several albumin-binding proteins (ABP) have been identified: three membrane-associated ABP, which we call gp60, gp30, and gp18, and one secreted protein, acidic and rich in cysteine (SPARC). In this study, we used antiserum raised against bovine SPARC (BON) to investigate the possible interrelationships among ABP to better understand their role in binding and transcytosis. BON not only interacted with SPARC secreted by cultured endothelium but also recognized gp60 in lysates of cultured rat, human, and bovine endothelial cells. Purified SPARC inhibited BON interaction with gp60. BON immunoglobulin (Ig)G specifically inhibited albumin binding to both SPARC and gp60 extracts. This effect was eliminated by preabsorption of BON to immobilized SPARC. BON also significantly inhibited albumin binding to cultured microvascular endothelial cells via its interaction with gp60. Anti-SPARC peptide sera were also tested, and one serum raised against a peptide encompassing an NH2-terminal region of SPARC recognized both SPARC and gp60 but did not inhibit albumin binding; gp30 and gp18 were not recognized by any of these anti-SPARC antibodies. These results suggest that SPARC and gp60 are functionally and immunologically related ABP that may share a common albumin-binding domain. gp60 appears to be the major mediator of albumin binding to microvascular endothelium.