Actin is a binding protein for angiogenin.

Abstract

The 42-kDa angiogenin binding protein isolated previously has been purified to electrophoretic homogeneity. It has been identified as a member of the actin family by peptide mapping and partial amino acid sequencing. The interaction of bovine muscle actin with angiogenin is similar to that of the angiogenin binding protein. Angiogenin induces the polymerization of actin below the critical concentration for spontaneous polymerization. The interaction occurs both in solution and on a poly(vinylidene difluoride) membrane. It is inhibited by excess unlabeled angiogenin and also by platelet factor 4 and protamine, which are known inhibitors of angiogenesis. Two other angiogenic molecules, basic fibroblast growth factor and tumor necrosis factor a, bind to 125I-labeled actin and can be crosslinked by a water-soluble carbodilmide. Both actin and an anti-actin antibody inhibit the angiogenic activity of angiogenin in the chicken embryo chorioallantoic membrane assay. The results indicate that the angiogenin binding protein is a cell surface actin and suggest that the reaction between angiogenin and this actin is an essential step in the angiogenesis process induced by angiogenin.Angiogenin is a 14-kDa protein purified initially from serumfree supernatants of an established human adenocarcinoma cell line, HT-29 (1). It was the first human tumor-derived angiogenic protein to be isolated based on its in vivo activity. It stimulates endothelial cells to produce diacylglycerol (2) and secrete prostacyclin (3) by phospholipase activation. It supports endothelial and fibroblast cell adhesion (4) and modulates a mitogenic effect in certain cells (5). An angiogenin binding protein (AngBP), which has properties consistent with its being a component of a cellular receptor for angiogenin, has been identified and isolated from a transformed endothelial cell line, GM7373 (6). It is a cell-surface protein with an apparent molecular mass of 42 kDa and is released from endothelial cells by exposure to heparnn, heparan sulfate, or angiogenin itself.We report here the further purification and characterization of AngBP. Tryptic peptide mapping and amino acid sequence analysis indicate that AngBP is a member of the actin family. The binding of angiogenin to bovine muscle actin and the inhibitory effect of actin and anti-actin antibodies on angiogenin-induced neovascularization on the chicken embryo chorioallantoic membrane (CAM) are also reported. The mechanism by which AngBP is released from the cell surface and the physiological significance of its presence and displacement remain to be elucidated.

Cell Surface-Dependent Generation of Angiostatin4.5

“…There have been a series of studies demonstrating the presence of one or more actin isoforms on the external cell surface. One or more actin isoform was found by several independent groups of researchers on the surface of lymphocytes (44,45), brain capillary endothelial cells (46), and bovine pulmonary endothelial cells (47)(48)(49)(50). Actin was also discovered as a cell surface binding site for plasminogen on endothelial cells (39), monocytoid cells, blood monocytes (34), and breast cancer cells (40).…”

Angiogenin antagonists prevent tumor growth in vivo.

“…It, like commercial actin preparations, binds tightly not only to bovine but also to mouse and human Ang (G.-F. Hu, personal communication). The demonstration that both actin and antiactin antibodies inhibit Ang-induced angiogenesis in the chicken embryo chorioallantoic membrane underscores the functional relevance of this interaction (16).…”

“…It activates intracellular second-messenger pathways (12), supports tumor and endothelial cell adhesion (6,13), and undergoes nuclear translocation (14). A 42-kDa Ang-binding protein isolated from the surface of cultured bovine endothelial cells has been identified as a smooth muscle type of a-actin (15)(16)(17). It, like commercial actin preparations, binds tightly not only to bovine but also to mouse and human Ang (G.-F. Hu, personal communication).…”

Angiogenin Regulation by Estradiol in Breast Tissue: Tamoxifen Inhibits Angiogenin Nuclear Translocation and Antiangiogenin Therapy Reduces Breast Cancer Growth In vivo

“…Angiogenin binds to endothelial cells (6,7), undergoes nuclear translocation, a process essential for its angiogenic activity (8)(9)(10)(11), and thereby induces a wide variety of responses including cell proliferation, activation of cellassociated proteases, and cell migration and invasion. Moreover, nuclear angiogenin in endothelial cells is necessary for angiogenesis induced by other angiogenic factors including vascular endothelial growth factor (VEGF), acidic and basic fibroblast growth factors, and epidermal growth factor (8).…”