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The proliferation of normal human fibroblast cells was enhanced by the addition of inorganic polyphosphate (poly(P)) into culture media. The mitogenic activities of acidic fibroblast growth factor (FGF-1) and basic fibroblast growth factor (FGF-2) were also enhanced by poly(P). A physical interaction between poly(P) and FGF-2 was observed, and FGF-2 was both physically and functionally stabilized by poly(P). Furthermore, poly(P) facilitated the FGF-2 binding to its cell surface receptors. Because poly(P) is widely distributed in mammalian tissues, it may be a spontaneous modulator of FGFs. Inorganic polyphosphates (poly(P))1 are linear polymers of many tens or hundreds of orthophosphate residues linked by high energy phosphoanhydride bonds that have been found in a wide range of organisms including bacteria, fungi, algae, mosses, insects, and protozoa and in the tissues of higher plants and animals (1-4). The biological functions of poly(P) have been investigated mostly in microorganisms, and the following functions have been proposed: (i) storage substance of energy or orthophosphate; (ii) chelator of metal cations; (iii) donor for sugar and adenylate kinase; (iv) buffer against alkaline stress; (v) structural element in competence for DNA entry and transformation; and (vi) a regulatory factor of gene expression (1-4). Although the presence of poly(P) has been demonstrated in the rat brain, rat liver, human peripheral blood mononuclear cells, human erythrocytes, human gingival fibroblasts, human osteoblasts, and human plasma and intracellularly in the nucleus, the mitochondria, lysosomes and plasma membrane (5), little is known regarding the functions of poly(P) and the effects of poly(P) on mammalian cells. Recently, the involvement of poly(P) in apoptosis and in modulation of the mineralization process in bone tissue (5, 6) has been suggested.Because there has been no report concerning the direct effect of poly(P) on mammalian cells and because poly(P) is widely distributed in mammalian tissues and plasma (5), we speculated that poly(P) has some physiological effect on cells. Based on this idea, we first studied in this report the effect of poly(P) on mammalian cell growth or proliferation in vitro and revealed the novel poly(P) functions concerning the modulation of mitogenic activity of fibroblast growth factors (FGF) (8). EXPERIMENTAL PROCEDURESMaterials-Normal dermal fibroblasts (NHDF) isolated from adult human were purchased from BioWhittaker, Inc. Normal human gingival fibroblasts (HGF) isolated from adult human were provided by Dr. Nishimura (Osaka Dental University). Balb/c 3T3 cells were from Riken Cell Bank (Tsukuba, Japan). Poly(P) type 65 (sodium salts with average chain length of 65 phosphate residues) was purchased from Sigma. Concentrations of poly(P) are given in terms of phosphate residues. As the control of poly(P), NaPO 4 buffer (orthophosphate) was used. The pH of the NaPO 4 buffer was adjusted to 7.0 by mixing the same concentrations of Na 2 HPO 4 and NaH 2 PO 4 solution. MTS (3-(4,5-dime...
The proliferation of normal human fibroblast cells was enhanced by the addition of inorganic polyphosphate (poly(P)) into culture media. The mitogenic activities of acidic fibroblast growth factor (FGF-1) and basic fibroblast growth factor (FGF-2) were also enhanced by poly(P). A physical interaction between poly(P) and FGF-2 was observed, and FGF-2 was both physically and functionally stabilized by poly(P). Furthermore, poly(P) facilitated the FGF-2 binding to its cell surface receptors. Because poly(P) is widely distributed in mammalian tissues, it may be a spontaneous modulator of FGFs. Inorganic polyphosphates (poly(P))1 are linear polymers of many tens or hundreds of orthophosphate residues linked by high energy phosphoanhydride bonds that have been found in a wide range of organisms including bacteria, fungi, algae, mosses, insects, and protozoa and in the tissues of higher plants and animals (1-4). The biological functions of poly(P) have been investigated mostly in microorganisms, and the following functions have been proposed: (i) storage substance of energy or orthophosphate; (ii) chelator of metal cations; (iii) donor for sugar and adenylate kinase; (iv) buffer against alkaline stress; (v) structural element in competence for DNA entry and transformation; and (vi) a regulatory factor of gene expression (1-4). Although the presence of poly(P) has been demonstrated in the rat brain, rat liver, human peripheral blood mononuclear cells, human erythrocytes, human gingival fibroblasts, human osteoblasts, and human plasma and intracellularly in the nucleus, the mitochondria, lysosomes and plasma membrane (5), little is known regarding the functions of poly(P) and the effects of poly(P) on mammalian cells. Recently, the involvement of poly(P) in apoptosis and in modulation of the mineralization process in bone tissue (5, 6) has been suggested.Because there has been no report concerning the direct effect of poly(P) on mammalian cells and because poly(P) is widely distributed in mammalian tissues and plasma (5), we speculated that poly(P) has some physiological effect on cells. Based on this idea, we first studied in this report the effect of poly(P) on mammalian cell growth or proliferation in vitro and revealed the novel poly(P) functions concerning the modulation of mitogenic activity of fibroblast growth factors (FGF) (8). EXPERIMENTAL PROCEDURESMaterials-Normal dermal fibroblasts (NHDF) isolated from adult human were purchased from BioWhittaker, Inc. Normal human gingival fibroblasts (HGF) isolated from adult human were provided by Dr. Nishimura (Osaka Dental University). Balb/c 3T3 cells were from Riken Cell Bank (Tsukuba, Japan). Poly(P) type 65 (sodium salts with average chain length of 65 phosphate residues) was purchased from Sigma. Concentrations of poly(P) are given in terms of phosphate residues. As the control of poly(P), NaPO 4 buffer (orthophosphate) was used. The pH of the NaPO 4 buffer was adjusted to 7.0 by mixing the same concentrations of Na 2 HPO 4 and NaH 2 PO 4 solution. MTS (3-(4,5-dime...
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