期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 285, 期 53, 页码 41827-41835出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M110.128926
关键词
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资金
- National Institutes of Health [1SC1CA134018-01, G12RR03032-19, 5U54NS041071]
- Department of Defense [W81XWH-07-1-0254]
The identity of the cell adhesive factors in fetal bovine serum, commonly used to supplement growth media, remains a mystery due to the plethora of serum proteins. In the present analyses, we showed that fetuin-A, whose function in cellular attachment in tissue culture has been debated for many years, is indeed a major serum cell attachment factor particularly for tumor cells. We are able to report this because of a new purification strategy that has for the first time given us a homogeneous protein band in colloidal Coomassie-stained gels that retains biological activity. The tumor cells adhered to immobilized fetuin-A and not alpha(2)-macroglobulin, its major contaminant. The interaction of cells with fetuin-A was driven mainly by Ca2+ ions, and cells growing in regular medium supplemented with fetal bovine serum were just as sensitive to loss of extracellular Ca2+ ions as cells growing in fetuin-A. Fractionation of human serum revealed that cell attachment was confined to the fractions that had fetuin-A. Interestingly, the tumor cells also took up fetuin-A and secreted it back to the medium using an unknown mechanism that can be observed in live cells. The attachment of tumor cells to fetuin-A was accompanied by phosphatidylinositol 3-kinase/Akt activation that was down-regulated in cells that lack annexin-A6, one of the cell surface receptors for fetuin-A. Taken together, our data show the significance of fetuin-A in tumor cell growth mechanisms in vitro and open new research vistas for this protein.
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