Modulation of Mitogenic Activity of Fibroblast Growth Factors by Inorganic Polyphosphate

Abstract

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...

Diabetes Autoantibodies Mediate Neural- and Endothelial Cell- Inhibitory Effects Via 5-Hydroxytryptamine- 2 Receptor Coupled to Phospholipase C/Inositol Triphosphate/Ca2+ Pathway

“…basic fibroblast growth factor (bFGF) [29], whose increased concentration in plasma correlated with the spontaneous appearance of agonist FGF-like autoantibodies in various pathologies including cancer subsets [11,30] and obese type 2 diabetes [31]. Vascular injury also causes platelets to release serotonin together with polyphosphates, the latter of which, like heparin, is a highly anionic substance capable of binding and protecting (locallyreleased) bFGF from inactivation [32]. Since platelet activation increases in obesity and inflammation [33], it is possible that repeated vascular injury through the release of sequestered antigens promotes immune response(s) (in susceptible individuals) leading to the formation of agonist 5-HT-2A receptor autoantibodies.…”

Myeloma cells contain high levels of inorganic polyphosphate which is associated with nucleolar transcription

“…6 We have also discovered that polyP polymers of approximately 75-80 Pi residues are the main intracellular type of polyP found in MC ( Figure 1B). PolyP polymers of this size are frequently found in mammalian cell signaling, and these molecules have been reported to stimulate mTOR kinase in mammary cancer cells, 39 to interact with fibroblast growth factor, 40 to be released by activated platelets, 6 and to modulate blood coagulation. 7 We have previously described that the addition of millimolar concentrations of extracellular polyP induces apoptosis specifically in MC and plasma cells.…”

Retraction: Polyphosphate-induced matrix metalloproteinase-3-mediated proliferation in rat dental pulp fibroblast-like cells is mediated by a Wnt5 signaling cascade

“…In mammals, Poly(P) is found in cells of the brain, heart, lung, and liver, and in erythrocytes (1)(2)(3). The most studied and well-known role of Poly(P) is the promotion of intracellular calcification (4). Poly(P) induces alkaline phosphate activity and up-regulates osteopontin and osteocalcin gene expression in osteoblastic cells (5,6).…”