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McKeehan WL, Wang F, Kan M. The heparan sulfate-fibroblast growth factor family: diversity of structure and function. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1998; 59:135-76. [PMID: 9427842 DOI: 10.1016/s0079-6603(08)61031-4] [Citation(s) in RCA: 290] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The fibroblast growth factor (FGF) receptor complex is a ubiquitous regulator of development and adult tissue homeostasis that bridges the peri-cellular matrix and the intracellular environment. Diverse members of the FGF polypeptide family, the FGF receptor tyrosine kinase (FGFRTK) family and the FGF receptor heparan sulfate proteoglycan (FGFRHS) family combine to result in active and specific FGFR signal transduction complexes. Regulated alternate splicing and combination of variant subdomains give rise to diversity of FGFRTK monomers. Divalent cations cooperate with the FGFRHS to conformationally restrict FGFRTK trans-phosphorylation, which causes depression of kinase activity and facilitates appropriate activation of the FGFR complex by FGF. Diffusional and conformational molecular models of the oligomeric FGFR complex are presented to explain how different point mutations in the FGFRTK commonly cause craniofacial and skeletal abnormalities of graded severity by graded increases in FGF-independent activity of total FGFR complexes. The role of the FGF family in liver growth and function and in prostate tumor progression is discussed.
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Feng S, Wang F, Matsubara A, Kan M, McKeehan WL. Fibroblast growth factor receptor 2 limits and receptor 1 accelerates tumorigenicity of prostate epithelial cells. Cancer Res 1997; 57:5369-78. [PMID: 9393762] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Progressive loss of the differentiated phenotype and communication with stroma accompanies the transition of nonmalignant rat prostate epithelial cells to anaplastic, malignant tumors. Here we show that cell surface expression of the fibroblast growth factor receptor 2 (FGFR2) tyrosine kinase is reduced in malignant tumor cell populations (type II) and undetectable at the mRNA level in 30% of cells. This is in addition to the irreversible loss by splice switching of the FGFR2 ectodomain that abrogates response to FGF-7 and homologues from the stroma. One hundred % of type II malignant cells express FGFR1, which is normally expressed in the stroma. Expression of the FGFR1 kinase in premalignant type I tumor epithelial cells by transfection accelerated progression to the malignant phenotype. In contrast to the FGFR2 kinase fused to the ectodomain of FGFR1, the FGFR1 kinase failed initially to support a mitogenic response to FGF-2 in type I tumor cells. However, the FGFR1-transfected cells acquired a mitogenic response after extensive proliferation of the cell population. Resident FGFR2 and ectopic FGFR1 appeared to be partitioned in the type I cells, because neither full-length nor truncated isoforms of FGFR1 affected the mitogenic response of the other. Restoration of the FGFR2IIIb kinase to malignant cells expressing FGFR1 depressed tumor growth rates, restored responsiveness to stromal cells, and restored epithelial cell differentiation. These observations reveal that homologous FGFR1 and FGFR2 kinases play very different roles in cell growth and differentiation and in development and support of the malignant phenotype.
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McKeehan WL, Wu X, Jang JH, Kan M. High salt inhibits both heparin-dependent and heparin-independent complexes of fibroblast growth factor and the receptor kinase. In Vitro Cell Dev Biol Anim 1997; 33:727-30. [PMID: 9466672 DOI: 10.1007/s11626-997-0146-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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Wang F, Kan M, McKeehan K, Jang JH, Feng S, McKeehan WL. A homeo-interaction sequence in the ectodomain of the fibroblast growth factor receptor. J Biol Chem 1997; 272:23887-95. [PMID: 9295338 DOI: 10.1074/jbc.272.38.23887] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Interaction of fibroblast growth factor receptors (FGFR) sufficient for a trans-phosphorylation event in which one intracellular domain is substrate for the other is essential for signal transduction. By analysis of the direct interaction of recombinant constructions co-expressed in baculoviral-infected insect cells, we identified a 17-amino acid sequence that is required for the stable interaction between ectodomains of FGFR. The sequence 160ERSPHRPILQAGLPANK176 (Glu160-Lys176) connects immunoglobulin modules II and III. In insect cells, the interaction between Glu160-Lys176 domains occurs independently of intact heparin or FGF binding domains. The sequence is not required for the binding of heparin or FGF-1, but is essential for mitogenic activity of the FGFR kinase in mammalian cells. The results support a model in which the homeo-interaction between Glu160-Lys176 in the ectodomain contributes to the interaction between intracellular domains in mammalian cell membranes (Kan, M., Wang, F., Kan, M., To, B., Gabriel, J. L., and McKeehan, W. L. (1996) J. Biol. Chem. 271, 26143-26148). We propose that the Glu160-Lys176 domain plays a pivotal role in restriction of the interaction between kinases by pericellular matrix heparan sulfate proteoglycan and divalent cations. Restrictions are overcome by FGF or constitutively by diverse gain of function mutations which cause skeletal and craniofacial abnormalities.
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Zhou FY, Kan M, Owens RT, McKeehan WL, Thompson JA, Linhardt RJ, Höök M. Heparin-dependent fibroblast growth factor activities: effects of defined heparin oligosaccharides. Eur J Cell Biol 1997; 73:71-80. [PMID: 9174673] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Heparin and related molecules have been identified as important participants in fibroblast growth factor (FGF) signaling although the mechanisms of action remain unclear. We have used heparin oligosaccharides to examine steps in the signaling process which could be affected by the polysaccharide. Immobilized FGF-1 and FGF-2 bound all sizes of oligosaccharides tested, ranging from tetrasaccharide to decasaccharide, at physiological salt concentration. Each group of oligosaccharide was eluted from the FGF affinity columns in several peaks, and larger oligosaccharides showed higher apparent affinity for the immobilized growth factors compared to the shorter ones. Heparin hexasaccharides were the smallest fragments providing complete protection of FGF-1 and FGF-2 against trypsin digestion. Tetrasaccharides, however, were able to provide partial protection. The requirement of heparin for ligand-receptor interaction was evaluated in receptor binding assays using Sf9 insect cells engineered to overexpress different recombinant FGF receptor (FGFR) species including FGFR1 beta, FGFR1 alpha or FGFR4 at the cell surface. In these assays hexasaccharides were the smallest fragments capable of stimulating FGF-receptor interaction. Over the range of concentrations examined, neither hexasaccharides nor octasaccharides were able to stimulate receptor binding to the level attained by intact heparin. In fact, these oligosaccharides interfered with the ability of intact heparin in promoting FGF-receptor binding. The presence of both stimulatory and inhibitory activities in hexasaccharide and octasaccharide populations could be attributed to structural heterogeneity within the oligosaccharide preparations. However, similar observations were obtained with "highly-sulfated" structurally homogeneous preparations of hexasaccharide and octasaccharide, although these molecules generally had greater stimulatory and less inhibitory activity than their structurally heterogeneous counterparts. Hexasaccharides were found to be the smallest fragments able to potentiate the FGF-1-induced 3T3 cell proliferation while their effect on FGF-2 signaling was less clear. These observations suggest that heparin can modulate FGF-signaling at several stages with different end results.
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Myoken Y, Myoken Y, Okamoto T, Sato JD, Kan M, McKeehan WL, Fujihara M, Takada K. Immunohistochemical localization of fibroblast growth factor-1 (FGF-1), FGF-2 and fibroblast growth factor receptor-1 (FGFR-1) in pleomorphic adenoma of the salivary glands. J Oral Pathol Med 1997; 26:17-22. [PMID: 9021547 DOI: 10.1111/j.1600-0714.1997.tb00004.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Fibroblast growth factor-1 (FGF-1) and FGF-2 are heparin-binding polypeptides that are potent mitogens for neoplastic cells. In this study, fibroblast growth factor-1 (FGF-1), FGF-2, and fibroblast growth factor receptor-1 (FGFR-1) were immunohistochemically analyzed in 10 patients with pleomorphic adenoma of the salivary gland by using specific monoclonal antibodies. The tumor tissues were histopathologically classified as: tubular, solid, myxoid or chondroid. Both FGF-1 and FGF-2 were immunohistochemically identified in the tumor cells of all histological types. In addition, immunoreactive FGF-2 was also found in the basement membrane of tubular type tumor cells. Conversely, FGFR-1-positive tumor cells were essentially confined to the tubular and solid areas of tumors. Tumor cells in the myxoid and chondroid areas were FGFR-1 immunonegative. These results suggest that the co-expression of FGF and its receptor appears to be related to the proliferative activity of tumor cells in the tubular and solid areas, whereas loss of FGF receptor expression may be associated with the differentiation of tumor cells into myxoid and chondroid tissue types.
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Luo Y, Gabriel JL, Wang F, Zhan X, Maciag T, Kan M, McKeehan WL. Molecular modeling and deletion mutagenesis implicate the nuclear translocation sequence in structural integrity of fibroblast growth factor-1. J Biol Chem 1996; 271:26876-83. [PMID: 8900171 DOI: 10.1074/jbc.271.43.26876] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The sequence NYKKPKL in the NH2 terminus of fibroblast growth factor (FGF)-1 has been proposed to affect the long term activities of FGF-1 through its function as a nuclear translocation signal or its role in stabilization of the structure required to sustain binding and activation of the transmembrane receptor kinase. A dynamic molecular model of FGF-1 docked into a duplex of the FGF receptor ectodomain and a hexadecameric heparin chain suggests that the NYKKPKL sequence does not directly interact with heparin or the receptor, but rather the lysine-leucine residues within the sequence indirectly stabilize a major receptor-binding domain. Concurrent with a marked increase in dependence on exogenous heparin for optimal activity, sequential deletion of residues in the NYKKPKL sequence in FGF-1 resulted in a progressive loss of thermal stability, resistance to protease, mitogenic activity, and affinity for the transmembrane receptor. The largest change resulted from deletion of the entire sequence through the lysine-leucine residues. In the presence of sufficiently high concentrations of heparin, the deletion mutants exhibited mitogenic activity equal to wild-type FGF-1. The results confirm that a primary role of the NYKKPKL sequence domain is to maintain the structural integrity of FGF-1 required for optimal binding to and activation of the heparan sulfate-transmembrane receptor complex.
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Kan M, Wang F, To B, Gabriel JL, McKeehan WL. Divalent cations and heparin/heparan sulfate cooperate to control assembly and activity of the fibroblast growth factor receptor complex. J Biol Chem 1996; 271:26143-8. [PMID: 8824259 DOI: 10.1074/jbc.271.42.26143] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Polypeptides of the fibroblast growth factor (FGF) family are ubiquitous bioregulators within tissues whose activity is controlled by heparan sulfates within the pericellular matrix. FGF and the ectodomain of their transmembrane tyrosine kinase receptors (FGFR) exhibit heparin-binding domains that when juxtaposed in a FGF middle dotFGFR complex can accommodate a single, potentially bivalent, decameric polysaccharide chain in a ternary complex. Here we show that the interaction of heparin with FGF ligands is not affected by divalent cations. In contrast, the high affinity interaction (apparent Kd = 10 nM) of heparin with FGFR requires Ca2+ or Mg2+ at physiological concentrations. Divalent cations maintain FGFR in a heparan sulfate-dependent state in respect to FGF binding and an FGF- and heparan sulfate-dependent state in respect to autophosphorylation. A model is proposed where divalent cations and heparan sulfate cooperate to maintain FGFR in a conformation that restricts trans-phosphorylation between intracellular kinase domains. The restriction is overcome by FGF or constitutively as a common consequence of diverse mutations in FGFR associated with skeletal and craniofacial abnormalities.
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Byrd V, Zhao XM, McKeehan WL, Miller GG, Thomas JW. Expression and functional expansion of fibroblast growth factor receptor T cells in rheumatoid synovium and peripheral blood of patients with rheumatoid arthritis. ARTHRITIS AND RHEUMATISM 1996; 39:914-22. [PMID: 8651984 DOI: 10.1002/art.1780390607] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
OBJECTIVE Rheumatoid arthritis (RA) is an inflammatory disorder of the diarthroidial joints, characterized by fibroblast proliferation, angiogenesis, and perivascular CD4+ T cell infiltration. The present study examined the interactions between fibroblast growth factor-1 (FGF-1) and T cells. METHODS Synovial tissues from patients with RA or noninflammatory arthritis were examined for the expression of FGF-1 and its receptor, FGFR-1, by immunohistology and reverse transcriptase-polymerase chain reaction. Functional assays were used to detect enrichment of FGF-1-responsive peripheral CD4+ T cells in RA. RESULTS FGF-1 is abundantly expressed by rheumatoid synovium. Enhanced expression of its receptor, FGFR-1, was found in perivascular CD4+ T cells. In addition, T cells that are activated by FGF-1 are increased in the peripheral blood of patients with RA, as compared with other inflammatory conditions. CONCLUSION The increased frequency of peripheral T cells that respond to FGF-1 in RA is consistent with expansion of FGFR-1-expressing T cells in the rheumatoid synovium.
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Matsuzaki K, Kan M, McKeehan WL. Reconstitution of a pentameric complex of dimeric transforming growth factor beta ligand and a type I, II, III receptor in baculoviral-infected insect cells. In Vitro Cell Dev Biol Anim 1996; 32:345-60. [PMID: 8842749 DOI: 10.1007/bf02722961] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Two transmembrane serine-threonine kinases (type I and II receptors), a membrane-anchored proteoglycan (type III), and a homodimeric ligand participate in the transforming growth factor beta type one (TGF beta 1) signal transduction complex. The expression of recombinant receptors in insect cells co-infected with up to three recombinant baculoviruses was employed to study interactions among the ectodomains of the three types of receptors and the TGF beta 1 ligand in absence of uncontrollable extrinsic factors in mammalian cells. Multi-subunit complexes were assembled in intact cells and purified on glutathione-conjugated beads for analysis by tagging one of the subunits with glutathione S-transferase (GST). Intrinsic ligand-independent interactions were observed among receptor subunits as follows: type III-III, type I-I, type III-I, and type II-I. The homeotypic complex of type II-II receptors and the heterotypic type III-II interaction was ligand dependent. The type I, but not the type III, subunit displaced about 50% of the type II component in either ligand-dependent homomeric type II-type II complexes or heteromeric type III-type II complexes to form type II-I or type III-II-I oligomers, respectively. The type II subunit displaced type I subunits in oligomers of the type I subunit. Specificity of type I receptors may result from differential affinity for the type II receptor rather than specificity for ligand. A monomeric subunit of the TGF beta 1 ligand bound concurrently to type III and type II or type III and type I receptors, but failed to concurrently bind to the type II and type I subunits. The binding of TGF beta 1 to the type I kinase subunit appears to require an intact disulfide-linked ligand dimer in the absence of a type III subunit. The combined results suggest a pentameric TGF beta signal transduction complex in which one unit each of the type III, type II, and type I components is assembled around the two subunits of the dimeric TGF beta ligand. An immobilized GST-tagged subunit of the receptor complex was utilized to assemble multi-subunit complexes in vitro and to study the phosphorylation events among subunits in the absence of extrinsic cell-derived kinases. The results revealed that (a) a low level of ligand-independent autophosphorylation occurs in the type I kinase; (b) a high level of autophosphorylation occurs in the type II kinase; (c) both the type III and type I subunits are trans-phosphorylated by the type II subunit; and (d) the presence of both type I and II kinases complexed with the type III subunit and dimeric TGF beta 1 ligand in a pentameric complex causes maximum phosphorylation of all three receptor subunits.
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Wang F, McKeehan WL. Insulin-like growth factor-1 messenger RNA isoforms in rat prostate and prostate tumors. In Vitro Cell Dev Biol Anim 1996; 32:265-8. [PMID: 8792155 DOI: 10.1007/bf02723058] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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Myoken Y, Myoken Y, Okamoto T, Sato JD, Kan M, McKeehan WL, Nakahara M, Takada K. Immunohistochemical study of overexpression of fibroblast growth factor-1 (FGF-1), FGF-2, and FGF receptor-1 in human malignant salivary gland tumours. J Pathol 1996; 178:429-36. [PMID: 8691322 DOI: 10.1002/(sici)1096-9896(199604)178:4<429::aid-path495>3.0.co;2-1] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Fibroblast growth factor-1 (FGF-1) and FGF-2 are broad spectrum mitogens. The expression of FGF-1, FGF-2, and their receptor, FGF receptor-1 (FGFR-1), was examined in malignant salivary gland tumours and normal salivary glands, using immunohistochemical methods. In seven cases of adenoid cystic carcinoma (ACC), both duct-like cells and modified myoepithelial cells were apparently immunopositive for FGF-1, FGF-2, and FGFR-1. In five cases of mucoepidermoid carcinoma (MC), all three types of tumour cells including epidermoid cells, and intermediate cells expressed immunoreactive FGF-1, FGF-2, and FGFR-1. In these malignant salivary gland tumours, increased expression of FGFR-1 correlated with the intensity of both FGF-1 and FGF-2 immunoreactivity. In contrast to malignant salivary gland tumours, eight cases of normal salivary gland showed negative immunostaining for FGF-1, FGF-2, and FGFR-1 while four cases were weakly immunoreactive for FGF and its receptor. These results demonstrate that malignant salivary gland tumours overexpress FGF-1, FGF-2, and FGFR-1 compared with normal salivary glands and suggest that these growth factors may play an important role in facilitating neoplastic progression in human salivary glands.
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Myoken Y, Myoken Y, Okamoto T, Kan M, McKeehan WL, Sato JD, Takada K. Expression of fibroblast growth factor-1 (FGF-1), FGF-2 and FGF receptor-1 in a human salivary-gland adenocarcinoma cell line: evidence of growth. Int J Cancer 1996; 65:650-7. [PMID: 8598317 DOI: 10.1002/(sici)1097-0215(19960301)65:5<650::aid-ijc15>3.0.co;2-b] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Fibroblast growth factor-1 (FGF-1) and FGF-2 are heparin-binding polype ptides which express potent mitogenic properties in neoplastic cells. In the present study, we have examined the contribution of endogenous FGF-1 and FGF-2 to the autocrine growth of HSY human salivary-gland adenocarcinoma cells in vitro. Using specific monoclonal antibodies against FGF-1 and FGF-2, immunohistochemical analysis of HSY cells revealed strong expression of both FGF-1 and FGF-2 in the cytoplasm and nucleus. Consistent with these data, 2 molecular mass species of FGF-1 (16 and 18 kDa) and 3 FGF-2 (18, 24 and 27 kDa) were identified in HSY cells by Western-blot analysis. Scatchard analysis of FGF binding sites on HSY cells indicated the presence of 23,000 [125I]FGF-1 binding sites/cells with a dissociation constant (KD) of 178 pM and 13,000 [125I]FGF-2 binding sites/cell with a KD of 102 pM. In addition, HSY cells were shown to express the mRNA for FGF receptor-1 (FGFR-1) by reverse transcription-polymerase chain reaction (RT-PCR), confirming the existence of high-affinity FGF binding sites. The influence of endogenous FGF-1 and FGF-2 on HSY cell growth was evaluated by suppressing the expression and activity of FGF by using anti-sense oligonucleotides and neutralizing antibodies. The addition of 50 micron FGF-1-specific anti-sense oligonucleotides to HSY cells resulted in a 61% inhibition of cell growth, while 50 microM FGF-2-specific anti-sense oligonucleotides resulted in a 76% inhibition. These effects were dose-dependent and specific, since sense oligonucleotides were ineffective in inhibiting HSY cell growth at the same concentration. Furthermore, HSY cell growth was suppressed in the presence of anti-FGF-1 or anti-FGF-2 neutralizing antibody, resulting in a 58% inhibition at 8 micromilligrams/ml. Our observations suggest that FGF-1 and FGF-2 may act as autocrine regulators by interacting with FGF receptors on HSY cells.
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Feng S, Xu J, Wang F, Kan M, McKeehan WL. Nuclear localization of a complex of fibroblast growth factor(FGF)-1 and an NH2-terminal fragment of FGF receptor isoforms R4 and R1alpha in human liver cells. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1310:67-73. [PMID: 9244177 DOI: 10.1016/0167-4889(95)00146-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
FGF ligands and FGF receptor 1 (FGFR1) appear associated with the nucleus in addition to their extracellular and transmembrane locations. After receptor-dependent internalization in liver cells, radiolabeled 16-kDa FGF-1 appears in a 40-kDa covalent complex with a cellular protein. In this report, we show that in a human hepatoma cell line, HepG2, which expresses both FGFR4 and FGFR1, the 40-kDa complex cross-reacts with antibodies against the ectodomain of both types of receptors. In addition to antibody against FGF-1, a polyclonal antiserum against the three immunoglobulin (Ig)-like loop ectodomain of FGFR4 and a monoclonal antibody to a 19-residue sequence in the NH2-terminus of the NH2-terminal Ig Loop I of the three loop splice variant of FGFR1 (FGFR1alpha) reacts with the complex. A monoclonal antibody against an epitope in FGFR1 downstream of the inter-loop I/II sequence which reacts with intact FGFR1 failed to cross-react with the 40-kDa complex. Cell fractionations and indirect immunofluorescent localization revealed that the 40-kDa complex associates with the particulate fraction of cells, particularly the nucleus and associated cytoskeletal elements. We propose that the NH2-terminal Ig-loop of the three loop isoforms of FGFR, which are generally associated inversely with cell growth, may play a role at or in the nucleus in addition to modification of affinity of the FGFR ectodomain for heparan sulfate and FGF ligand.
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Zhao XM, Byrd VM, McKeehan WL, Reich MB, Miller GG, Thomas JW. Costimulation of human CD4+ T cells by fibroblast growth factor-1 (acidic fibroblast growth factor). JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 1995; 155:3904-11. [PMID: 7561097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
T cell infiltration is prevalent in wound healing, atherosclerosis, vascular lesions in chronic allograft rejection, and autoimmune diseases. Whether T cells play a role in the migration and proliferation of vascular smooth muscle cells and endothelial cells in these lesions is not known. We previously reported that some human T cells express FGF-1, a potent growth factor for vascular smooth muscle cells and endothelial cells. In this study, we extend this observation and examine the expression and function of FGF receptors on human T cells. Using reverse transcription-PCR, Northern analysis, and immunohistochemistry, we found that some human T cells also express high affinity FGF receptor 1 (FGFR-1) respond to FGF-1. In the presence of anti-CD3, exogenous FGF-1 functions as a costimulator for these T cells, while FGF-1 alone does not induce T cell proliferation. [3H]Thymidine incorporation is sevenfold higher in T cells costimulated with FGF-1 compared with stimulation with anti-CD3 alone. Using limiting dilution, we demonstrate that FGF-responsive T cells are present in normal peripheral blood at a mean frequency of 1:19780 (95% confidence limits, 1:15100-1:23000), and similar T cells are increased in the peripheral blood of heart transplant recipients (mean frequency, 1:4210; 95% confidence limits, 1:3420-1:6781). In addition, a subline of Jurkat, a human T cell tumor, expresses FGFR-1 receptor. The function of FGFR-1 receptor in Jurkat T cells is demonstrated by the production of IL-2 after stimulation with FGF-1 and anti-CD3. IL-2 levels are sevenfold higher in Jurkat T cells costimulated with FGF-1 compared with those stimulated with anti-CD3 alone. FGF-1 alone has no effect on Jurkat T cells. These findings thus provide evidence that a subset of human T cells expresses a receptor for vascular cell growth factors, and this receptor functions to increase IL-2 production consistent with costimulation. The potential role of FGF-responsive T cells in a variety of vascular and inflammatory lesions is discussed.
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Zhao XM, Byrd VM, McKeehan WL, Reich MB, Miller GG, Thomas JW. Costimulation of human CD4+ T cells by fibroblast growth factor-1 (acidic fibroblast growth factor). THE JOURNAL OF IMMUNOLOGY 1995. [DOI: 10.4049/jimmunol.155.8.3904] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Abstract
T cell infiltration is prevalent in wound healing, atherosclerosis, vascular lesions in chronic allograft rejection, and autoimmune diseases. Whether T cells play a role in the migration and proliferation of vascular smooth muscle cells and endothelial cells in these lesions is not known. We previously reported that some human T cells express FGF-1, a potent growth factor for vascular smooth muscle cells and endothelial cells. In this study, we extend this observation and examine the expression and function of FGF receptors on human T cells. Using reverse transcription-PCR, Northern analysis, and immunohistochemistry, we found that some human T cells also express high affinity FGF receptor 1 (FGFR-1) respond to FGF-1. In the presence of anti-CD3, exogenous FGF-1 functions as a costimulator for these T cells, while FGF-1 alone does not induce T cell proliferation. [3H]Thymidine incorporation is sevenfold higher in T cells costimulated with FGF-1 compared with stimulation with anti-CD3 alone. Using limiting dilution, we demonstrate that FGF-responsive T cells are present in normal peripheral blood at a mean frequency of 1:19780 (95% confidence limits, 1:15100-1:23000), and similar T cells are increased in the peripheral blood of heart transplant recipients (mean frequency, 1:4210; 95% confidence limits, 1:3420-1:6781). In addition, a subline of Jurkat, a human T cell tumor, expresses FGFR-1 receptor. The function of FGFR-1 receptor in Jurkat T cells is demonstrated by the production of IL-2 after stimulation with FGF-1 and anti-CD3. IL-2 levels are sevenfold higher in Jurkat T cells costimulated with FGF-1 compared with those stimulated with anti-CD3 alone. FGF-1 alone has no effect on Jurkat T cells. These findings thus provide evidence that a subset of human T cells expresses a receptor for vascular cell growth factors, and this receptor functions to increase IL-2 production consistent with costimulation. The potential role of FGF-responsive T cells in a variety of vascular and inflammatory lesions is discussed.
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Wang F, Kan M, McKeehan WL. Multiple mutant cDNAs from one reaction mixture using asymmetric primers in PCR. Biotechniques 1995; 19:556-9. [PMID: 8777043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
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Wang F, Kan M, Yan G, Xu J, McKeehan WL. Alternately spliced NH2-terminal immunoglobulin-like Loop I in the ectodomain of the fibroblast growth factor (FGF) receptor 1 lowers affinity for both heparin and FGF-1. J Biol Chem 1995; 270:10231-5. [PMID: 7730327 DOI: 10.1074/jbc.270.17.10231] [Citation(s) in RCA: 109] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Alternate splicing of a single exon encoding an NH2-terminal immunoglobulin (Ig) disulfide loop in the ectodomain of the fibroblast growth factor receptor (FGFR) types 1 and 2 results in alpha and beta isoforms that exhibit 3- and 2-Ig loops, respectively. Previously we demonstrated that alternately spliced Loop I has no independent ligand binding activity but is sufficiently interactive with the ligand- and heparin-binding site formed by Loops II and III to lower affinity for the same fibroblast growth factor (FGF) ligand. Here we show that a lower affinity of FGFR1 alpha for heparin parallels the lower affinity for FGF-1. A mutant of FGFR1 alpha in which the sequence between Loops I and II was deleted exhibits high affinity for both FGF-1 and heparin and other properties of the FGFR1 beta isoform, which include resistance to degradation by trypsin and display of specific antibody epitopes. This suggests that the interloop sequence facilitates the interaction of Loop I with Loops II and III. Lack of expression of both exons coding for Loop I and the sequence between Loops I and II in the FGFR2 gene characterizes rat prostate tumor cells, which exhibit a loss of the low affinity class of FGF receptors. Although the exon coding for the sequence between Loops I and II is alternately spliced in the FGFR2 beta isoform, coordinate expression with the exon coding for Loop I results in the functional differences between the FGFR alpha and FGFR beta variants.
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Wang F, Kan M, Xu J, Yan G, McKeehan WL. Ligand-specific structural domains in the fibroblast growth factor receptor. J Biol Chem 1995; 270:10222-30. [PMID: 7730326 DOI: 10.1074/jbc.270.17.10222] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Two tandem immunoglobulin-like disulfide loops (Loops II and III) linked by a short connecting sequence in the ectodomain of the fibroblast growth factor receptor kinase compose the binding sites for glycosaminoglycan and fibroblast growth factor (FGF) ligands. Alternate splicing of exons IIIb and IIIc coding for the COOH-terminal half of Loop III confers high affinity for FGF-7 or FGF-2, respectively, on the fibroblast growth factor receptor ectodomain without effect on the binding of FGF-1. Here we show that a 139-amino acid fragment composed of Loop II, the inter-Loop II/III sequence, and a short segment of the NH2 terminus of Loop III is sufficient and near the minimal requirement for binding of FGF-1, FGF-2, and FGF-7. Extension of the fragment by five additional highly conserved residues (SD(P/A)QP) within a distinct constitutive structural domain (fl1) in Loop III restricts the binding of FGF-7 without effect on FGF-1 and FGF-2. Since the presence of exon IIIc in the full-length ectodomain does not change this ligand binding profile, we suggest that alternately spliced exon IIIc plays no active role in binding of the three ligands. In contrast, exon IIIb actively abrogates the restriction on the binding of FGF-7 and concurrently lowers the affinity for FGF-2.
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Xu J, McKeehan K, Matsuzaki K, McKeehan WL. Inhibin antagonizes inhibition of liver cell growth by activin by a dominant-negative mechanism. J Biol Chem 1995; 270:6308-13. [PMID: 7890768 DOI: 10.1074/jbc.270.11.6308] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The beta:beta activin homodimer and alpha:beta inhibin heterodimer are mutual antagonists which share a common beta subunit. Recently, it has been shown that, similar to transforming growth factor-beta 1, activin is an inhibitor of hepatocyte DNA synthesis. The activin receptor appears to be an obligatory complex of genetically distinct type I and II transmembrane serine/threonine kinases. Activin type I receptors, SKR1 and SKR2, were first cloned from well differentiated human hepatoma cells (HepG2). This prompted us to investigate the binding of activin and inhibin to receptors from HepG2 cells and the effect of the two ligands on DNA synthesis. Here we show that beta:beta activin binds to the activin type II receptor kinase (ActRII) which induces activin binding to the type I receptor kinase SKR2 to form ActRII.beta:beta.SKR2 complexes in which an activin beta chain occupies each receptor subunit. Inhibin also binds to ActRII through its beta subunit, competes with the binding of activin to ActRII, but fails to form the ActRII.SKR2 complex. No specific binding site for inhibin could be demonstrated in HepG2 cells. Inhibin, which had no activity of its own, antagonized the inhibitory effect of activin on DNA synthesis. The results suggest that inhibin may be a natural antagonist of assembly of the heterodimeric activin receptor complex through a dominant-negative mechanism.
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Prudovsky I, Savion N, Zhan X, Friesel R, Xu J, Hou J, McKeehan WL, Maciag T. Intact and functional fibroblast growth factor (FGF) receptor-1 trafficks near the nucleus in response to FGF-1. J Biol Chem 1994; 269:31720-4. [PMID: 7527394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Exogenous fibroblast growth factor-1 (FGF-1) associates with the nucleus in a receptor-dependent manner during the entire G1 period of the BALB/c 3T3 cell cycle (Zhan, X., Hu, X., Friesel, R., and Maciag, T. (1993) J. Biol. Chem. 268, 9611-9620). To further study the role of the FGF receptor (FGFR) during this translocation, the intracellular fate of FGFR-1 protein and enzymatic activity was examined. Immunoprecipitation using multiple FGFR-1 antibodies followed by an in vitro tyrosine kinase activity assay enabled us to identify FGFR-1 as a 130-kDa phosphotyrosine-containing protein associated with the nuclear fraction of NIH 3T3 cells exposed to FGF-1. While FGFR-1 tyrosine kinase activity could be detected as a nuclear-associated protein after a 2-h exposure of the NIH 3T3 cells to FGF-1, this activity appeared to be maximal in the nuclear fraction between 4 and 12 h after FGF-1 treatment. In addition, analysis by confocal immunofluorescence microscopy of quiescent and FGF-1-stimulated NIH 3T3 cells reveal a prominent perinuclear FGFR-1 staining pattern in the cells exposed to FGF-1 but not in the quiescent population. We also observed FGFR-1 associated with the nuclear fraction in FGFR-1-transfected L6 rat myoblasts, which are known to be refractive to exogenous FGF-1 and express relatively low levels of endogenous FGFR-1. In addition, these cells also exhibited the presence of a 145-kDa phosphoprotein in the nuclear fraction that was recognized by FGFR-1 antibodies. These results suggest that the FGFR-1 may be translocated near the nucleus upon interaction with its ligand during the entire G1 period of the NIH 3T3 cell cycle as a structurally intact and functional tyrosine kinase that may be accessible to perinuclear polypeptides as a regulatory enzyme.
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Morrison RS, Shi E, Kan M, Yamaguchi F, McKeehan W, Rudnicka-Nawrot M, Palczewski K. Inositolhexakisphosphate (InsP6): an antagonist of fibroblast growth factor receptor binding and activity. In Vitro Cell Dev Biol Anim 1994; 30A:783-9. [PMID: 7881632 DOI: 10.1007/bf02631302] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Fibroblast growth factors (FGF), which have been implicated in tumor cell growth and angiogenesis, have biological activities that appear to be mediated by both heparinlike extracellular matrix sites and transmembrane tyrosine kinase receptor sites. In the present study, we demonstrated that inositolhexakisphosphate (InsP6) inhibits basic FGF (bFGF) binding to heparin. Our spectrofluorometric analyses demonstrated that InsP6 not only bound to bFGF, presumably within the bFGF heparin-binding domain, but also protected bFGF from degradation by trypsin. Also, InsP6 inhibited the cellular binding of bFGF and other fibroblast growth factor family members such as acidic FGF (aFGF) and K-FGF in a saturable and dose-dependent manner. Furthermore, concentrations as low as 100 microM InsP6 inhibited bFGF-induced DNA synthesis in AKR-2B fibroblasts, as well as the growth of bFGF- and K-FGF-transfected NIH/3T3 cells. Together, these results indicate that InsP6 may serve as a useful antagonist of FGF activity.
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Fukabori Y, Yan G, Yamanaka H, McKeehan WL. Rapid induction of keratinocyte growth factor (FGF-7) and beta-actin after exposure of prostate stromal cells to androgen. In Vitro Cell Dev Biol Anim 1994; 30A:745-6. [PMID: 7881627 DOI: 10.1007/bf02631296] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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McKeehan WL, Kan M. Heparan sulfate fibroblast growth factor receptor complex: structure-function relationships. Mol Reprod Dev 1994; 39:69-81; discusison 81-2. [PMID: 7999363 DOI: 10.1002/mrd.1080390112] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Splice variations in genes coding for the transmembrane FGF receptor (FGFR) result in isoforms that vary in the ectodomain, intracellular juxtamembrane domain, and the intracellular kinase domain. An analysis of biochemical functions of distinct recombinant isoforms expressed in baculoviral-infected insect cells allowed generation of models for function of splice variants in both the ecto- and intracellular domains. A structural model for the ectodomain of the FGFR is proposed as follows. Alternately-spliced immunoglobulin-like disulfide Loop I, which is not required for ligand-binding, is sufficiently interactive with the base FGF binding site formed by Loops II and III to modify ligand affinity and affect interaction of the receptor with heparan sulfate cofactor. The NH2-terminal domain of Loop II, which is highly conserved across all isoforms, exhibits a 19-residue heparin-binding domain which is obligatory for FGF binding. Heparin protects a 30-kDa ligand-binding fragment from proteolysis that is composed of Loop II, the inter-Loop II/III sequence, and the NH2-terminus of Loop III. This suggests that the high-affinity FGF receptor complex is an intimate ternary complex of transmembrane tyrosine kinase, heparan sulfate glycosaminoglycan, and FGF, each of which have interactive binding domains for the other and may contribute to specificity of the FGFR complex. Although Ig Loop II, the inter-Loop II/III sequence, and the NH2-terminus of Loop III with heparan sulfate form the base FGF binding site, mutually exclusive alternate splicing of two exons coding for the COOH-terminal half of Loop III determines which specific members of the FGF ligand family bind with high affinity to the base site. A kinase- and tyrosine phosphorylation site-defective splice variant, FGFR type 2, acts as a dominant-negative suppressor of phosphorylation of specifically tyr-653 in the catalytic domain of the kinase, with less effect on phosphorylation of tyr-766 in the COOH-terminal tail. We propose that phosphorylation of tyr-766, which is required for interaction of phospholipase C gamma 1 (PLC gamma 1) with the receptor, may occur by a cis-intramolecular mechanism within FGFR monomers, while phosphorylation of tyr-653, which is required for phosphorylation of PLC gamma 1, may occur by a trans-intermolecular mechanism between monomers within kinase homodimers. From the combined results, we propose a model whereby increasing concentrations of FGF may control FGF-mediated signal transduction by heterodimerization of different FGFR monomers. Different monomers arise by regulated combinatorial alternate splicing that alters both the extracellular and intracellular domains.
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Xu J, Matsuzaki K, McKeehan K, Wang F, Kan M, McKeehan WL. Genomic structure and cloned cDNAs predict that four variants in the kinase domain of serine/threonine kinase receptors arise by alternative splicing and poly(A) addition. Proc Natl Acad Sci U S A 1994; 91:7957-61. [PMID: 8058741 PMCID: PMC44523 DOI: 10.1073/pnas.91.17.7957] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Heterodimers of types I and II serine/threonine kinase receptor monomers compose the active receptor complex for ligands of the transforming growth factor beta family. Here we show that the genomic organization of coding sequences for the intracellular domain of a widely expressed type I serine/threonine kinase receptor is similar to that of the activin type II receptor gene. The genomic structure and cDNA clones indicate that poly(A) addition to alternative exons at each of three carboxyl-terminal coding exon-intron junctions may be a common feature of both type I and II receptor genes. The predicted products are monomers truncated at kinase subdomains VII, IX, and X which vary in kinase activity and potential serine, threonine, and tyrosine phosphorylation sites. These results suggest that combinations of variants that affect the signal-transducing intracellular kinase domain of both type I and II receptor monomers within the transforming growth factor beta ligand family may add to the heterogeneity of biological effects of individual ligands in the family.
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MESH Headings
- Alternative Splicing
- Amino Acid Sequence
- Base Sequence
- Carcinoma, Hepatocellular
- Cell Line
- Cloning, Molecular
- Conserved Sequence
- DNA Primers
- DNA, Complementary/chemistry
- DNA, Complementary/metabolism
- Gene Expression
- Genetic Variation
- Humans
- Liver Neoplasms
- Macromolecular Substances
- Molecular Sequence Data
- Poly A/metabolism
- Polymerase Chain Reaction
- Protein Serine-Threonine Kinases/biosynthesis
- RNA, Messenger/biosynthesis
- Receptors, Growth Factor/biosynthesis
- Receptors, Growth Factor/genetics
- Receptors, Transforming Growth Factor beta
- Sequence Homology, Amino Acid
- Transforming Growth Factor beta/metabolism
- Tumor Cells, Cultured
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