-
Seiji Mori,
Vu Tran,
Kyoko Nishikawa,
Teruya Kaneda,
Yoshinosuke Hamada,
Naomasa Kawaguchi,
Masaaki Fujita,
Yoko K Takada,
Nariaki Matsuura,
Min Zhao, Yoshikazu Takada
[show abstract]
[hide abstract]
ABSTRACT: Fibroblast growth factor-1 (FGF1) and FGF2 play a critical role in angiogenesis, a formation of new blood vessels from existing blood vessels. Integrins are critically involved in FGF signaling through crosstalk. We previously reported that FGF1 directly binds to integrin αvβ3 and induces FGF receptor-1 (FGFR1)-FGF1-integrin αvβ3 ternary complex. We previously generated an integrin binding defective FGF1 mutant (Arg-50 to Glu, R50E). R50E is defective in inducing ternary complex formation, cell proliferation, and cell migration, and suppresses FGF signaling induced by WT FGF1 (a dominant-negative effect) These findings suggest that FGFR and αvβ3 crosstalk through direct integrin binding to FGF, and that R50E acts as an antagonist to FGFR. We studied if R50E suppresses tumorigenesis and angiogenesis. Here we describe that R50E suppressed tumor growth in vivo while WT FGF1 enhanced it using cancer cells that stably express WT FGF1 or R50E. Since R50E did not affect proliferation of cancer cells , we hypothesized that R50E suppressed tumorigenesis indirectly through suppressing angiogenesis. We thus studied the effect of R50E on angiogenesis in several angiogenesis models. We found that excess R50E suppressed FGF1-induced migration and tube formation of endothelial cells, FGF1-induced angiogenesis in matrigel plug assays, and the outgrowth of cells in aorta ring assays. Excess R50E suppressed FGF1-induced angiogenesis in chick embryo chorioallantoic membrane (CAM) assays. Interestingly, excess R50E suppressed FGF2-induced angiogenesis in CAM assays as well, suggesting that R50E may uniquely suppress signaling from other members of the FGF family. Taken together, our results suggest that R50E suppresses angiogenesis induced by FGF1 or FGF2, and thereby indirectly suppresses tumorigenesis, in addition to its possible direct effect on tumor cell proliferation We propose that R50E has potential as an anti-cancer and anti-angiogenesis therapeutic agent ("FGF1 decoy").
PLoS ONE 01/2013; 8(2):e57927. · 4.09 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Integrin αvβ3 plays a role in insulin-like growth factor-1 (IGF1) signaling (integrin-IGF1 receptor (IGF1R) crosstalk) in non-transformed cells in anchorage-dependent conditions. We previously reported that IGF1 directly binds to αvβ3, and induces αvβ3-IGF1-IGF1R ternary complex formation in these conditions. The integrin-binding defective IGF1 mutant (R36E/R37E) is defective in inducing ternary complex formation and IGF signaling while it still binds to IGF1R. We studied if IGF1 can induce signaling in anchorage-independent conditions in transformed Chinese hamster ovary (CHO) cells that express αvβ3 (β3-CHO) cells. Here we describe that IGF1 signals were more clearly detectable in anchorage-independent conditions (polyHEMA-coated plates) than in anchorage-dependent conditions. This suggests that IGF signaling is masked by signals from cell-matrix interaction in anchorage-dependent conditions. IGF signaling required αvβ3 expression, and R36E/R37E was defective in inducing signals in polyHEMA-coated plates. These results suggest that αvβ3-IGF1 interaction, not αvβ3-extracellular matrix interaction, is essential for IGF signaling. Inhibitors of IGF1R, Src, AKT, and ERK1/2 did not suppress αvβ3-IGF-IGF1R ternary complex formation, suggesting that activation of these kinases are not required for ternary complex formation. Also, mutations of the β3 cytoplasmic tail (Y747F and Y759F) that block β3 tyrosine phosphorylation did not affect IGF1R phosphorylation or AKT activation. We propose a model, in which IGF1 binding to IGF1R induces recruitment of integrin αvβ3 to the IGF-IGF1R complex, and then β3 and IGF1R are phosphorylated. It is likely that αvβ3 should be together with the IGF1-IGF1R complex for triggering IGF signaling.
Journal of Biological Chemistry 12/2012; · 4.77 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The membrane-bound chemokine fractalkine (FKN, CX3CL1) on endothelial cells plays a role in leukocyte trafficking. The chemokine domain (FKN-CD) is sufficient for inducing FKN signaling (e.g., integrin activation), and FKN-CD binds to its receptor CX3CR1 on leukocytes. Whereas previous studies suggest that FKN-CD does not directly bind to integrins, our docking simulation studies predicted that FKN-CD directly interacts with integrin α(v)β(3). Consistent with this prediction, we demonstrated that FKN-CD directly bound to α(v)β(3) and α(4)β(1) at a very high affinity (K(D) of 3.0 × 10(-10) M to α(v)β(3) in 1 mM Mn(2+)). Also, membrane-bound FKN bound to integrins α(v)β(3) and α(4)β(1), suggesting that the FKN-CD/integrin interaction is biologically relevant. The binding site for FKN-CD in α(v)β(3) was similar to those for other known α(v)β(3) ligands. Wild-type FKN-CD induced coprecipitation of integrins and CX3CR1 in U937 cells, suggesting that FKN-CD induces ternary complex formation (CX3CR1, FKN-CD, and integrin). Based on the docking model, we generated an integrin-binding defective FKN-CD mutant (the K36E/R37E mutant). K36E/R37E was defective in ternary complex formation and integrin activation, whereas K36E/R37E still bound to CX3CR1. These results suggest that FKN-CD binding to CX3CR1 is not sufficient for FKN signaling, and that FKN-CD binding to integrins as coreceptors and the resulting ternary complex formation are required for FKN signaling. Notably, excess K36E/R37E suppressed integrin activation induced by wild-type FKN-CD and effectively suppressed leukocyte infiltration in thioglycollate-induced peritonitis. These findings suggest that K36E/R37E acts as a dominant-negative CX3CR1 antagonist and that FKN-CD/integrin interaction is a novel therapeutic target in inflammatory diseases.
The Journal of Immunology 11/2012; · 5.79 Impact Factor
-
Long Ye,
Tiffany Dickerson,
Handeep Kaur,
Yoko K Takada,
Masaaki Fujita,
Ruiwu Liu,
John M Knapp,
Kit S Lam,
Neil E Schore,
Mark J Kurth, Yoshikazu Takada
[show abstract]
[hide abstract]
ABSTRACT: Increased concentrations of secreted phospholipase A2 type IIA (sPLA2-IIA), have been found in the synovial fluid of patients with rheumatoid arthritis. It has been shown that sPLA2-IIA specifically binds to integrin αvβ3, and initiates a signaling pathway that leads to cell proliferation and inflammation. Therefore, the interaction between integrin and sPLA2-IIA could be a potential therapeutic target for the treatment of proliferation or inflammation-related diseases. Two one-bead-one-compound peptide libraries were constructed and screened, and seven target hits were identified. Herein we report the identification, synthesis, and biological testing of two pyrazolylthiazole-tethered peptide hits and their analogs. Biological assays showed that these compounds were able to suppress the sPLA2-IIA-integrin interaction and sPLA2-IIA-induced migration of monocytic cells and that the blockade of the sPLA2-IIA-integrin binding was specific to sPLA2-IIA and not to the integrin.
Bioorganic & medicinal chemistry letters 10/2012; · 2.65 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Upon vascular injury, platelets initiate interaction with exposed subendothelial matrices through various receptors such as
glycoprotein (GP) Ib/IX/V complex, α2β1 integrin, and GPVI/FcRγ. Although these interactions cannot sustain stable platelet
thrombus formation by themselves, they ultimately lead to the activation of αIIbβ3 integrin (GPIIb-IIIa complex [GPIIb-IIIa]),
the most abundant receptor in platelets. The αIIbβ3 integrin plays a central role in primary hemostasis by serving as a receptor
for fibrinogen and von Willebrand factor (vWf). It establishes a stable interaction with vWf bound to the extracellular matrices
and uses fibrinogen as a bridging molecule in platelet aggregate formation. The αIIbβ3 integrin also plays an important role
in the pathogenesis of thrombosis. Over the past decades, a tremendous amount of effort has been made to elucidate the ligand-binding
mechanisms of αIIbβ3, in part because of its clinical significance. Most of the studies have relied on biochemical analyses
of purified αIIbβ3 or recombinant proteins generated in vitro. With the lack of actual 3-dimensional structure, molecular
modeling has provided a useful framework for interpreting such experimental data on structure-function correlation of integrin
molecules. However, it has also generated disagreement between different models. The aim of this minireview is to summarize
the past efforts as well as the recent accomplishments in elucidating the structure/function of αIIbβ3. Finally, we will try
to explain all those experimental data using the recently published crystal structure of the extracellular domains of the
αVβ3 heterodimeric complex.
International Journal of Hematology 04/2012; 74(4):382-389. · 1.27 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Integrin αvβ3 plays a role in insulin-like growth factor-1 (IGF1) signaling (integrin-IGF1 receptor (IGF1R) cross-talk). The specifics of the cross-talk are, however, unclear. In a current model, "ligand occupancy" of αvβ3 (i.e. the binding of extracellular matrix proteins) enhances signaling induced by IGF1 binding to IGF1R. We recently reported that IGF1 directly binds to αvβ3 and induces αvβ3-IGF1-IGF1R ternary complex formation. Consistently, the integrin binding-defective IGF1 mutant (R36E/R37E) is defective in inducing ternary complex formation and IGF signaling, but it still binds to IGF1R. Like αvβ3, integrin α6β4 is overexpressed in many cancers and is implicated in cancer progression. Here, we discovered that α6β4 directly bound to IGF1, but not to R36E/R37E. Grafting the β4 sequence WPNSDP (residues 167-172), which corresponds to the specificity loop of β3, to integrin β1 markedly enhanced IGF1 binding to β1, suggesting that the WPNSDP sequence is involved in IGF1 recognition. WT IGF1 induced α6β4-IGF1-IGF1R ternary complex formation, whereas R36E/R37E did not. When cells were attached to matrix, exogenous IGF1 or α6β4 expression had little or no effect on intracellular signaling. When cell-matrix adhesion was reduced (in poly(2-hydroxyethyl methacrylate-coated plates), IGF1 induced intracellular signaling and enhanced cell survival in an α6β4-dependent manner. Also IGF1 enhanced colony formation in soft agar in an α6β4-dependent manner. These results suggest that IGF binding to α6β4 plays a major role in IGF signaling in anchorage-independent conditions, which mimic the in vivo environment, and is a novel therapeutic target.
Journal of Biological Chemistry 02/2012; 287(15):12491-500. · 4.77 Impact Factor
-
Joy X Jiang,
Xiangling Chen,
Daniel K Hsu,
Kornelia Baghy,
Nobuko Serizawa,
Fiona Scott, Yoshikazu Takada,
Yoko Takada,
Hiroo Fukada,
Jenny Chen,
Sridevi Devaraj,
Roger Adamson,
Fu-Tong Liu,
Natalie J Török
[show abstract]
[hide abstract]
ABSTRACT: Hepatic stellate cells (HSC), the key fibrogenic cells of the liver, transdifferentiate into myofibroblasts upon phagocytosis of apoptotic hepatocytes. Galectin-3, a β-galactoside-binding lectin, is a regulator of the phagocytic process. In this study, our aim was to study the mechanism by which extracellular galectin-3 modulates HSC phagocytosis and activation. The role of galectin-3 in engulfment was evaluated by phagocytosis and integrin binding assays in primary HSC. Galectin-3 expression was studied by real-time PCR and enzyme-linked immunosorbent assay, and in vivo studies were done in wild-type and galectin-3(-/-) mice. We found that HSC from galectin-3(-/-) mice displayed decreased phagocytic activity, expression of transforming growth factor-β1, and procollagen α1(I). Recombinant galectin-3 reversed this defect, suggesting that extracellular galectin-3 is required for HSC activation. Galectin-3 facilitated the α(v)β(3) heterodimer-dependent binding, indicating that galectin-3 modulates HSC phagocytosis via cross-linking this integrin and enhancing the tethering of apoptotic cells. Blocking integrin α(v)β(3) resulted in decreased phagocytosis. Galectin-3 expression and release were induced in active HSC engulfing apoptotic cells, and this was mediated by the nuclear factor-κB signaling. The upregulation of galectin-3 in active HSC was further confirmed in vivo in bile duct-ligated (BDL) rats. Galectin-3(-/-) mice displayed significantly decreased fibrosis, with reduced expression of α-smooth muscle actin and procollagen α1(I) following BDL. In summary, extracellular galectin-3 plays a key role in liver fibrosis by mediating HSC phagocytosis, activation, and subsequent autocrine and paracrine signaling by a feedforward mechanism.
AJP Gastrointestinal and Liver Physiology 12/2011; 302(4):G439-46. · 3.43 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Cartilage oligomeric matrix protein (COMP) is an important non-collagenous cartilage protein that is essential for the structural integrity of the cartilage extracellular matrix. The repeated modular structure of COMP allows it to "bridge" and assemble multiple cartilage extracellular matrix components such as collagens, matrilins, and proteoglycans. With its modular structure, COMP also has the potential to act as a scaffold for growth factors, thereby affecting how and when the growth factors are presented to cell-surface receptors. However, it is not known whether COMP binds growth factors. We studied the binding interaction between COMP and TGF-β1 in vitro and determined the effect of COMP on TGF-β1-induced signal transduction in reporter cell lines and primary cells. Our results demonstrate that mature COMP protein binds to multiple TGF-β1 molecules and that the peak binding occurs at slightly acidic pH. These interactions were confirmed by dual polarization interferometry and visualized by rotary shadow electron microscopy. There is cation-independent binding of TGF-β1 to the C-terminal domain of COMP. In the presence of manganese, an additional TGF-β-binding site is present in the TSP3 repeats of COMP. Finally, we show that COMP-bound TGF-β1 causes increased TGF-β1-dependent transcription. We conclude that TGF-β1 binds to COMP and that TGF-β1 bound to COMP has enhanced bioactivity.
Journal of Biological Chemistry 09/2011; 286(50):43250-8. · 4.77 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Integrin-growth factor receptor cross-talk plays a role in growth factor signaling, but the specifics are unclear. In a current model, integrins and growth factor receptors independently bind to their ligands (extracellular matrix and growth factors, respectively). We discovered that neuregulin-1 (NRG1), either as an isolated EGF-like domain or as a native multi-domain form, binds to integrins αvβ3 (with a K(D) of 1.36 × 10(-7) m) and α6β4. Docking simulation predicted that three Lys residues at positions 180, 184, and 186 of the EGF-like domain are involved in integrin binding. Mutating these residues to Glu individually or in combination markedly suppressed integrin binding and ErbB3 phosphorylation. Mutating all three Lys residues to Glu (the 3KE mutation) did not affect the ability of NRG1 to bind to ErbB3 but markedly reduced the ability of NRG1 to induce ErbB3 phosphorylation and AKT and Erk1/2 activation in MCF-7 and T47D human breast cancer cells. This suggests that direct integrin binding to NRG1 is critical for NRG1/ErbB signaling. Notably, stimulation of cells with WT NRG1 induced co-precipitation of ErbB3 with α6β4 and with αvβ3 to a much lower extent. This suggests that WT NRG1 induces integrin-NRG1-ErbB3 ternary complex formation. In contrast, the 3KE mutant was much less effective in inducing ternary complex formation than WT NRG1, suggesting that this process depends on the ability of NRG1 to bind to integrins. These results suggest that direct NRG1-integrin interaction mediates integrin-ErbB cross-talk and that α6β4 plays a major role in NRG-ErbB signaling in these cancer cells.
Journal of Biological Chemistry 10/2010; 285(41):31388-98. · 4.77 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Integrin-growth factor receptor cross-talk plays a role in growth factor signaling, but the specifics are unclear. In a current
model, integrins and growth factor receptors independently bind to their ligands (extracellular matrix and growth factors,
respectively). We discovered that neuregulin-1 (NRG1), either as an isolated EGF-like domain or as a native multi-domain form,
binds to integrins αvβ3 (with a KD of 1.36 × 10−7 m) and α6β4. Docking simulation predicted that three Lys residues at positions 180, 184, and 186 of the EGF-like domain are
involved in integrin binding. Mutating these residues to Glu individually or in combination markedly suppressed integrin binding
and ErbB3 phosphorylation. Mutating all three Lys residues to Glu (the 3KE mutation) did not affect the ability of NRG1 to
bind to ErbB3 but markedly reduced the ability of NRG1 to induce ErbB3 phosphorylation and AKT and Erk1/2 activation in MCF-7
and T47D human breast cancer cells. This suggests that direct integrin binding to NRG1 is critical for NRG1/ErbB signaling.
Notably, stimulation of cells with WT NRG1 induced co-precipitation of ErbB3 with α6β4 and with αvβ3 to a much lower extent.
This suggests that WT NRG1 induces integrin-NRG1-ErbB3 ternary complex formation. In contrast, the 3KE mutant was much less
effective in inducing ternary complex formation than WT NRG1, suggesting that this process depends on the ability of NRG1
to bind to integrins. These results suggest that direct NRG1-integrin interaction mediates integrin-ErbB cross-talk and that
α6β4 plays a major role in NRG-ErbB signaling in these cancer cells.
Journal of Biological Chemistry 10/2010; 285(41):31388-31398. · 4.77 Impact Factor
-
Wenwu Xiao,
Yan Wang,
Edmond Y Lau,
Juntao Luo,
Nianhuan Yao,
Changying Shi,
Leah Meza,
Harry Tseng,
Yoshiko Maeda,
Pappanaicken Kumaresan,
Ruiwu Liu,
Felice C Lightstone, Yoshikazu Takada,
Kit S Lam
[show abstract]
[hide abstract]
ABSTRACT: The αvβ3 integrin, expressed on the surface of various normal and cancer cells, is involved in numerous physiologic processes such as angiogenesis, apoptosis, and bone resorption. Because this integrin plays a key role in angiogenesis and metastasis of human tumors, αvβ3 integrin ligands are of great interest to advances in targeted therapy and cancer imaging. In this report, one-bead one-compound (OBOC) combinatorial libraries containing the arginine-glycine-aspartic acid (RGD) motif were designed and screened against K562 myeloid leukemia cells that had been transfected with the human αvβ3 integrin gene. Cyclic peptide LXW7 was identified as a leading ligand with a built-in handle that binds specifically to αvβ3 and showed comparable binding affinity (IC(50) = 0.68 ± 0.08 μmol/L) to some of the well-known RGD "head-to-tail" cyclic pentapeptide ligands reported in the literature. The biotinylated form of LXW7 ligand showed similar binding strength as LXW7 against αvβ3 integrin, whereas biotinylated RGD cyclopentapeptide ligands revealed a 2- to 8-fold weaker binding affinity than their free forms. LXW7 was able to bind to both U-87MG glioblastoma and A375M melanoma cell lines, both of which express high levels of αvβ3 integrin. In vivo and ex vivo optical imaging studies with the biotinylated ligand/streptavidin-Cy5.5 complex in nude mice bearing U-87MG or A375M xenografts revealed preferential uptake of biotinylated LXW7 in tumor. When compared with biotinylated RGD cyclopentapeptide ligands, biotinylated LXW7 showed higher tumor uptake but lower liver uptake.
Molecular Cancer Therapeutics 10/2010; 9(10):2714-23. · 5.23 Impact Factor
-
Yoshikazu Takada,
Yoko Ono,
Jun Saegusa,
Jun Sagusa,
Constantine Mitsiades,
Nicholas Mitsiades,
Jean Tsai,
Yong He,
Ernest Maningding,
Annie Coleman,
Dalila Ramirez-Maverakis,
Raphael Rodrigues,
Raphael Rodriquez,
Yoko Takada,
Emanual Maverakis
[show abstract]
[hide abstract]
ABSTRACT: The C-terminal domain of the fibrinogen gamma chain (gammaC) has been shown to bind to the integrins alphaIIbbeta3, alphaMbeta2 and alphaVbeta3. It has also been reported that a peptide derived from the alphaMbeta2-binding site of gammaC can suppress an animal model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE). Here we have truncated gammaC at position 399 to remove the prothrombotic alphaIIbbeta3-binding site. We show that this truncated version of gammaC, termed gammaC399tr, can bind to activated T cells. In addition, T cells incubated with gammaC399tr secreted less IFN-gamma when stimulated with antigen and APC; however, cytokine secretion was unaltered when T cells were stimulated non-specifically with a mixture of anti-CD3 and anti-CD28 antibodies. Thus, only antigen-dependent T cell activation is inhibited by gammaC399tr. When administered intraperitoneally, gammaC399tr potently inhibited actively induced EAE and reversed ongoing disease. We hypothesize that the ability of gammaC399tr to inhibit autoreactive immune responses is a result of its ability to bind integrins. This activity was not solely dependent on the alphaMbeta2 integrin-binding site. When polyalanine was substituted for the alphaMbeta2-binding site, the resulting gammaC390polyA was still able to inhibit EAE. To our knowledge, this is the first demonstration that T cells can bind to fibrin (ogen), an important extracellular matrix protein that is deposited at sites of inflammation. Our results also identify gammaC399tr as a novel therapeutic molecule.
Journal of Autoimmunity 06/2010; 34(4):453-9. · 7.37 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Crosstalk between integrins and FGF receptors has been implicated in FGF signaling, but the specifics of the crosstalk are unclear. We recently discovered that 1) FGF1 directly binds to integrin alphavbeta3, 2) the integrin-binding site and FGF receptor (FGFR) binding site are distinct, and 3) the integrin-binding-defective FGF1 mutant (R50E) is defective in inducing FGF signaling although R50E still binds to FGFR and heparin and induces transient ERK1/2 activation.
We tested if excess R50E affect DNA synthesis and cell survival induced by WT FGF1 in BaF3 mouse pro-B cells expressing human FGFR1. R50E suppressed DNA synthesis and cell proliferation induced by WT FGF1. We tested if WT FGF1 and R50E generate integrin-FGF1-FGFR ternary complex. WT FGF1 induced ternary complex formation (integrin-FGF-FGFR1) and recruitment of SHP-2 to the complex in NIH 3T3 cells and human umbilical endothelial cells, but R50E was defective in these functions. It has been reported that sustained ERK1/2 activation is integrin-dependent and crucial to cell cycle entry upon FGF stimulation. We thus determined the time-course of ERK1/2 activation induced by WT FGF1 and R50E. We found that WT FGF1 induced sustained activation of ERK1/2, but R50E was defective in this function.
Our results suggest that 1) R50E is a dominant-negative mutant, 2) Ternary complex formation is involved in FGF signaling, 3) The defect of R50E to bind to integrin may be directly related to the antagonistic action of R50E. Taken together, these results suggest that R50E has potential as a therapeutic in cancer.
PLoS ONE 01/2010; 5(4):e10273. · 4.09 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: It has been proposed that ligand occupancy of integrin alphavbeta3 with extracellular matrix ligands (e.g. vitronectin) plays a critical role in insulin-like growth factor-1 (IGF-1) signaling. We found that expression of alphavbeta3 enhanced IGF-1-induced proliferation of Chinese hamster ovary cells in serum-free conditions (in the absence of vitronectin). We hypothesized that the direct integrin binding to IGF-1 may play a role in IGF-1 signaling. We demonstrated that alphavbeta3 specifically and directly bound to IGF-1 in cell adhesion, enzyme-linked immunosorbent assay-type binding, and surface plasmon resonance studies. We localized the amino acid residues of IGF-1 that are critical for integrin binding by docking simulation and mutagenesis. We found that mutating two Arg residues at positions 36 and 37 in the C-domain of IGF-1 to Glu (the R36E/R37E mutation) effectively reduced integrin binding. Interestingly, although the mutant still bound to IGF1R, it was defective in inducing IGF1R phosphorylation, AKT and ERK1/2 activation, and cell proliferation. Furthermore wild type IGF-1 mediated co-precipitation of alphavbeta3 and IGF1R, whereas the R36E/R37E mutant did not, suggesting that IGF-1 mediates the interaction between alphavbeta3 and IGF1R. These results suggest that the direct binding to IGF-1 to integrin alphavbeta3 plays a role in IGF-1 signaling through ternary complex formation (alphavbeta3-IGF-IGF1R), and integrin-IGF-1 interaction is a novel target for drug discovery.
Journal of Biological Chemistry 08/2009; 284(36):24106-14. · 4.77 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Four "one-bead one-compound" (OBOC) combinatorial libraries were designed, synthesized, and screened against MDA-MB-231 breast cancer cells. A novel cyclic peptide 1 (LXY1) with high binding specificity to alpha3 integrin was identified. Molecular interactions between alpha3 integrin and 1 were characterized by using a series of K562 cells transfected with various mutant alpha3 integrins. Using analytic flow cytometry, the binding affinity (K(d)) of 1 to alpha3 integrin on MDA-MB-231 breast cancer cells was determined to be approximately 0.4 microM. Based on the established structure-activity relationship (SAR) study, two highly focused cyclic peptide libraries were further designed, synthesized, and screened against MDA-MB-231 breast cancer cells under stringent conditions. A novel cyclic peptide 2 (LXY3) with a high binding affinity (IC(50) = 57 nM) was identified. Moreover, the targeting efficiency and specificity of 2 to the breast adenocarcinoma tumors in mouse xenografts were further confirmed by in vivo and ex vivo near-infrared fluorescence optical imaging.
Journal of Medicinal Chemistry 01/2009; 52(1):126-33. · 4.80 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Secretory phospholipase A2 group IIA (sPLA2-IIA) plays an important role in the pathogenesis of inflammatory diseases. Catalytic activity of this enzyme that generates arachidonic acid is a major target for development of anti-inflammatory agents. Independent of its catalytic activity, sPLA2-IIA induces pro-inflammatory signals in a receptor-mediated mechanism (e.g. through the M-type receptor). However, the M-type receptor is species-specific: sPLA2-IIA binds to the M-type receptor in rodents and rabbits, but not in human. Thus sPLA2-IIA receptors in human have not been established. Here we demonstrated that sPLA2-IIA bound to integrin alphavbeta3 at a high affinity (K(D)=2 x 10(-7) M). We identified amino acid residues in sPLA2-IIA (Arg-74 and Arg-100) that are critical for integrin binding using docking simulation and mutagenesis. The integrin-binding site did not include the catalytic center or the M-type receptor-binding site. sPLA2-IIA also bound to alpha4beta1. We showed that sPLA2-IIA competed with VCAM-1 for binding to alpha4beta1, and bound to a site close to those for VCAM-1 and CS-1 in the alpha4 subunit. Wild type and the catalytically inactive H47Q mutant of sPLA2-IIA induced cell proliferation and ERK1/2 activation in monocytic cells, but the integrin binding-defective R74E/R100E mutant did not. This indicates that integrin binding is required, but catalytic activity is not required, for sPLA2-IIA-induced proliferative signaling. These results suggest that integrins alphavbeta3 and alpha4beta1 may serve as receptors for sPLA2-IIA and mediate pro-inflammatory action of sPLA2-IIA, and that integrin-sPLA2-IIA interaction is a novel therapeutic target.
Journal of Biological Chemistry 09/2008; 283(38):26107-15. · 4.77 Impact Factor
-
Seiji Mori,
Chun-Yi Wu,
Satoshi Yamaji,
Jun Saegusa,
Biao Shi,
Zi Ma,
Yasuko Kuwabara,
Kit S Lam,
R Rivkah Isseroff,
Yoko K Takada, Yoshikazu Takada
[show abstract]
[hide abstract]
ABSTRACT: Integrins play a role in fibroblast growth factor (FGF) signaling through cross-talk with FGF receptors (FGFRs), but the mechanism underlying the cross-talk is unknown. We discovered that FGF1 directly bound to soluble and cell-surface integrin alphavbeta3 (K(D) about 1 microm). Antagonists to alphavbeta3 (monoclonal antibody 7E3 and cyclic RGDfV) blocked this interaction. alphavbeta3 was the predominant, if not the only, integrin that bound to FGF1, because FGF1 bound only weakly to several beta1 integrins tested. We presented evidence that the CYDMKTTC sequence (the specificity loop) within the ligand-binding site of beta3 plays a role in FGF1 binding. We found that the integrin-binding site of FGF1 overlaps with the heparin-binding site but is distinct from the FGFR-binding site using docking simulation and mutagenesis. We identified an FGF1 mutant (R50E) that was defective in integrin binding but still bound to heparin and FGFR. R50E was defective in inducing DNA synthesis, cell proliferation, cell migration, and chemotaxis, suggesting that the direct integrin binding to FGF1 is critical for FGF signaling. Nevertheless, R50E induced phosphorylation of FGFR1 and FRS2alpha and activation of AKT and ERK1/2. These results suggest that the defect in R50E in FGF signaling is not in the initial activation of FGF signaling pathway components, but in the later steps in FGF signaling. We propose that R50E is a useful tool to identify the role of integrins in FGF signaling.
Journal of Biological Chemistry 07/2008; 283(26):18066-75. · 4.77 Impact Factor
-
Seiji Mori,
Chun-Yi Wu,
Satoshi Yamaji,
Jun Saegusa,
Biao Shi,
Zi Ma,
Yasuko Kuwabara,
Kit S. Lam,
R. Rivkah Isseroff,
Yoko K. Takada, Yoshikazu Takada
[show abstract]
[hide abstract]
ABSTRACT: Integrins play a role in fibroblast growth factor (FGF) signaling through cross-talk with FGF receptors (FGFRs), but the mechanism
underlying the cross-talk is unknown. We discovered that FGF1 directly bound to soluble and cell-surface integrin αvβ3 (KD about 1 μm). Antagonists to αvβ3 (monoclonal antibody 7E3 and cyclic RGDfV) blocked this interaction. αvβ3 was the predominant, if not
the only, integrin that bound to FGF1, because FGF1 bound only weakly to several β1 integrins tested. We presented evidence
that the CYDMKTTC sequence (the specificity loop) within the ligand-binding site of β3 plays a role in FGF1 binding. We found
that the integrin-binding site of FGF1 overlaps with the heparin-binding site but is distinct from the FGFR-binding site using
docking simulation and mutagenesis. We identified an FGF1 mutant (R50E) that was defective in integrin binding but still bound
to heparin and FGFR. R50E was defective in inducing DNA synthesis, cell proliferation, cell migration, and chemotaxis, suggesting
that the direct integrin binding to FGF1 is critical for FGF signaling. Nevertheless, R50E induced phosphorylation of FGFR1
and FRS2α and activation of AKT and ERK1/2. These results suggest that the defect in R50E in FGF signaling is not in the initial
activation of FGF signaling pathway components, but in the later steps in FGF signaling. We propose that R50E is a useful
tool to identify the role of integrins in FGF signaling.
Journal of Biological Chemistry 06/2008; 283(26):18066-18075. · 4.77 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Coagulation activation by tissue factor (TF) is implicated in cancer progression, cancer-associated thrombosis and metastasis. The role of direct TF signaling pathways in cancer, however, remains incompletely understood. Here we address how TF contributes to primary tumor growth by using a unique pair of isotype-matched antibodies that inhibit either coagulation (monoclonal antibody [Mab]-5G9) or direct signaling (Mab-10H10). We demonstrate that the inhibitory antibody of direct TF-VIIa signaling not only blocks TF-VIIa mediated activation of PAR2, but also disrupts the interaction of TF with integrins. In epithelial and TF-expressing endothelial cells, association of TF with beta1 integrins is regulated by TF extracellular ligand binding and independent of PAR2 signaling or proteolytic activity of VIIa. In contrast, alpha3beta1 integrin association of TF is constitutive in breast cancer cells and blocked by Mab-10H10 but not by Mab-5G9. Mab-5G9 has antitumor activity in vivo, but we show here that Mab-10H10 is at least as effective in suppressing human xenograft tumors in 2 different models. Breast tumor growth was also attenuated by blocking PAR2 signaling. These results show that tumor cell TF-PAR2 signaling is crucial for tumor growth and suggest that anti-TF strategies can be applied in cancer therapy with minor impairment of TF-dependent hemostatic pathways.
Blood 02/2008; 111(1):190-9. · 9.90 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The integrins are a superfamily of cell adhesion receptors that bind to extracellular matrix ligands, cell-surface ligands, and soluble ligands. They are transmembrane alphabeta heterodimers and at least 18 alpha and eight beta subunits are known in humans, generating 24 heterodimers. Members of this family have been found in mammals, chicken and zebrafish, as well as lower eukaryotes, including sponges, the nematode Caenorhabditis elegans (two alpha and one beta subunits, generating two integrins) and the fruitfly Drosophila melanogaster (five alpha and one beta, generating five integrins). The alpha and beta subunits have distinct domain structures, with extracellular domains from each subunit contributing to the ligand-binding site of the heterodimer. The sequence arginine-glycine-aspartic acid (RGD) was identified as a general integrin-binding motif, but individual integrins are also specific for particular protein ligands. Immunologically important integrin ligands are the intercellular adhesion molecules (ICAMs), immunoglobulin superfamily members present on inflamed endothelium and antigen-presenting cells. On ligand binding, integrins transduce signals into the cell interior; they can also receive intracellular signals that regulate their ligand-binding affinity. Here we provide a brief overview that concentrates mostly on the organization, structure and function of mammalian integrins, which have been more extensively studied than integrins in other organisms.
Genome biology 02/2007; 8(5):215. · 6.63 Impact Factor
