Zhu W Q, Ochieng J
Department of Biochemistry, Meharry Medical College, Nashville, Tennessee 37208, USA.
Cancer Res. 2001 Mar 1;61(5):1869-73.
Galectin-3, a beta-galactoside binding protein, plays a significant role in cell to extracellular matrix interactions. Despite its extracellular expression, the precise physiological mechanisms that trigger its release from the intracellular milieu have not been characterized. The present analyses were, therefore, done to identify the extracellular matrix proteins with propensity to induce the release of intracellular galectin-3 from breast carcinoma cells. Our studies demonstrate that fetuin, a serum glycoprotein that is abundant in the fetal serum, is capable of inducing the rapid release (approximately 1 min) of intracellular galectin-3 from the cells. The mechanism by which galectin-3 is rapidly released appears to be novel and does not depend on changes in intracellular calcium levels. We also report that galectin-3-expressing breast carcinoma cells in serumless medium adhere and spread well on microtiter wells in the presence of fetuin and divalent ions in a carbohydrate-dependent manner. The data suggest that fetuin is a natural modulator of galectin-3 secretion/release and that the secreted galectin-3 modulates the activity of cell surface receptors for extracellular matrix proteins.
半乳糖凝集素-3是一种β-半乳糖苷结合蛋白，在细胞与细胞外基质的相互作用中发挥着重要作用。尽管它在细胞外表达，但其从细胞内环境释放的精确生理机制尚未明确。因此，进行了本分析以鉴定倾向于诱导乳腺癌细胞释放细胞内半乳糖凝集素-3的细胞外基质蛋白。我们的研究表明，胎球蛋白是一种在胎儿血清中丰富的血清糖蛋白，能够诱导细胞快速释放（约1分钟）细胞内的半乳糖凝集素-3。半乳糖凝集素-3快速释放的机制似乎是新颖的，且不依赖于细胞内钙水平的变化。我们还报告说，在无血清培养基中表达半乳糖凝集素-3的乳腺癌细胞在胎球蛋白和二价离子存在的情况下，以碳水化合物依赖的方式在微量滴定孔上很好地粘附和铺展。数据表明，胎球蛋白是半乳糖凝集素-3分泌/释放的天然调节剂，并且分泌的半乳糖凝集素-3调节细胞表面细胞外基质蛋白受体的活性。
