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Nobutaka Fujii

Publications and source records attributed to Nobutaka Fujii.

At least 55 records · Page 3Linked to original sources
PubMed2005

Development of anti-HIV agents targeting dynamic supramolecular mechanism: entry and fusion inhibitors based on CXCR4/CCR5 antagonists and gp41-C34-remodeling peptides.

A molecular mechanism involved both in HIV-entry and -fusion steps has been disclosed in detail: The interaction of an HIV envelope protein, gp120, with chemokine receptors, CXCR4 and CCR5, which were identified as major co-receptors in association with CD4, triggers conformational changes in the gp120-gp41 (another envelope protein) complex, and subsequently forms the trimer-of-hairpins structure of gp41 followed by virus-cell membrane fusion. The elucidation of the above dynamic supramolecular mechanism in HIV-entry and -fusion has provided insights into new type of drugs that can block HIV infection. Based on this, we have developed not only coreceptor antagonists (1) but also fusion inhibitors (2). (1) Potent CXCR4 antagonists, T22 and T140, have been developed through the structure-activity relationship studies on tachyplesins and polyphemusins that are horseshoe crabs' antimicrobial peptides. T22, which was initially found to bind gp120 and CD4, and T140 selectively suppress T-cell line-tropic HIV-1 (X4-HIV-1) entry based on their specific binding to CXCR4. Furthermore, molecular-size reduction of T140 using cyclic pentapeptide templates brought us to find low molecular weight CXCR4 antagonists, such as FC131. (2) Artificial remodeling of a gp41 fragment, C34, has led to development of strong inhibitors of HIV-fusion into cells. These fusion inhibitors effectively block the formation of the trimer-of-hairpins structure of gp41. HIV-entry/fusion inhibitors such as CXCR4 antagonists and C34 analogs would improve the clinical chemotherapy of AIDS and HIV-infected patients. This review article focuses on our recent research on the development of the above two types of inhibitors, including comparative studies with several CXCR4 antagonists besides T22/T140-related compounds and other fusion inhibitors such as Fuzeon (T-20).

Amino Acid Sequence↗
PubMed2004

Cyclic peptides from the loop region of the laminin alpha 4 chain LG4 module show enhanced biological activity over linear peptides.

Laminins, heterotrimeric glycoproteins in the basement membrane, are involved in diverse biological activities. So far, five alpha, three beta, and three gamma chains have been identified, and at least 15 laminin isoforms exist composed of various combinations of the different three chains. The major cell-surface receptors for laminins are integrins and proteoglycans, such as dystroglycans and syndecans. Previously, we reported that synthetic peptide A4G82 (TLFLAHGRLVFM, mouse laminin alpha4 chain residues 1514-1525) showed strong cell attachment and syndecan binding activities. On the basis of the crystal structure of the LG module and sequence alignment, A4G82 is located in the connecting loop region between beta-strands E and F in the laminin alpha4 chain LG4 module. Here, we have focused on the structural importance of this E-F loop region for the biological activity of the alpha4 chain LG4 module. To determine the importance of the loop structure, we synthesized peptide A4G82X (cyclo-A4G82X, Cys-TLFLAHGRLVFX-Cys, X= norleucine), which was cyclized via disulfide bridges at both the N- and C-termini. The cyclic peptides derived from A4G82X inhibited the heparin binding activity of the alpha4 chain G domain and promoted HT-1080 cell attachment better than the corresponding linear peptides. We determined FLAHGRLVFX as a minimal sequence of cyclo-A4G82X important for cell adhesion and heparin binding using a series of truncated peptides. Moreover, HT-1080 cell attachment to the cyclic peptides was more efficiently blocked by heparin than cell attachment to the linear peptides. Furthermore, the cyclic peptides showed significantly enhanced syndecan-2-mediated cell attachment activity. These results indicate that the activity of A4G82 is highly conformation-dependent, suggesting that the E-F loop structure is crucial for its biological activity.

Amino Acid Sequence↗
PubMed2004

Chemokine receptor expression in EBV-associated lymphoproliferation in hu/SCID mice: implications for CXCL12/CXCR4 axis in lymphoma generation.

The mechanisms by which intraperitoneal injection of peripheral blood mono-nuclear cells (PBMCs) from Epstein-Barr virus (EBV)-seropositive donors into severe combined immunodeficient (SCID) mice gives rise to lymphomas (hu/SCID tumors) are far from clear. This study addressed whether chemokine receptors and their ligands could be implicated in this experimental model. CXCR4 was found to be highly expressed in hu/SCID tumors; surface expression of CXCR4 was prevalently limited to a tumor cell subset poorly expressing CD23, whereas the CXCR4 ligand, CXCL12, was predominantly expressed by the tumor subpopulation expressing CD23. In vitro inhibition of this autocrine/paracrine CXCL12/CXCR4 axis significantly inhibited lymphoma proliferation and survival. Furthermore, CXCL12 was expressed in cells recovered from the mouse peritoneal cavity early after PBMC transfer as well as by EBV-transformed B cells but not by resting or activated B lymphocytes; also, lymphoma development was associated with a dramatic increase in the levels of murine CXCL12 present in the peritoneal cavity. Finally, antagonizing the CXCL12/CXCR4 axis in vivo strongly counteracted lymphoma development. These studies demonstrate that CXCL12 expression may be associated with EBV infection and suggest that the CXCR4/CXCL12 axis may participate in the EBV-associated lymphomagenesis process in immunodeficient hosts.

Animals↗
PubMed2004

Germinal center dark and light zone organization is mediated by CXCR4 and CXCR5.

Germinal center (GC) dark and light zones segregate cells undergoing somatic hypermutation and antigen-driven selection, respectively, yet the factors guiding this organization are unknown. We report here that GC organization was absent from mice deficient in the chemokine receptor CXCR4. Centroblasts had high expression of CXCR4 and GC B cells migrated toward the CXCR4 ligand SDF-1 (CXCL12), which was more abundant in the dark zone than in the light zone. CXCR4-deficient cells were excluded from the dark zone in the context of a wild-type GC. These findings establish that GC organization depends on sorting of centroblasts by CXCR4 into the dark zone. In contrast, CXCR5 helped direct cells to the light zone and deficiency in CXCL13 was associated with aberrant light zone localization.

Animals↗
PubMed2004

Identification of a CXCR4 antagonist, a T140 analog, as an anti-rheumatoid arthritis agent.

Several recent papers support the involvement of an interaction between stromal cell-derived factor-1 (SDF-1/CXCL12) and its receptor, chemokine receptor CXCR4, in memory T cell migration in the inflamed rheumatoid arthritis (RA) synovium. Analogs of the 14-mer peptide T140 were previously found to be specific CXCR4 antagonists that were characterized as not only HIV-entry inhibitors but also anti-cancer-metastatic agents. In this study, a T140 analog, 4F-benzoyl-TN14003, was proven to inhibit CXCL12-mediated migration of human Jurkat cells and mouse splenocyte in a dose-dependent manner in vitro (IC(50)=0.65 and 0.54 nM, respectively). Furthermore, slow release administration by subcutaneous injection (s.c.) of 4F-benzoyl-TN14003 using an Alzet osmotic pump significantly suppressed the delayed-type hypersensitivity response induced by sheep red blood cells in mice, and significantly ameliorated clinical severity in collagen-induced arthritis in mice. As such, T140 analogs might be attractive lead compounds for chemotherapy of RA.

Animals↗
PubMed2004

HIV protease inhibitor nelfinavir inhibits replication of SARS-associated coronavirus.

A novel coronavirus has been identified as an etiological agent of severe acute respiratory syndrome (SARS). To rapidly identify anti-SARS drugs available for clinical use, we screened a set of compounds that included antiviral drugs already in wide use. Here we report that the HIV-1 protease inhibitor, nelfinavir, strongly inhibited replication of the SARS coronavirus (SARS-CoV). Nelfinavir inhibited the cytopathic effect induced by SARS-CoV infection. Expression of viral antigens was much lower in infected cells treated with nelfinavir than in untreated infected cells. Quantitative RT-PCR analysis showed that nelfinavir could decrease the production of virions from Vero cells. Experiments with various timings of drug addition revealed that nelfinavir exerted its effect not at the entry step, but at the post-entry step of SARS-CoV infection. Our results suggest that nelfinavir should be examined clinically for the treatment of SARS and has potential as a good lead compound for designing anti-SARS drugs.

Animals↗
PubMed2004

Indium-mediated atom-transfer and reductive radical cyclizations of iodoalkynes: synthesis and biological evaluation of HIV-protease inhibitors.

Novel indium-mediated radical cyclization reactions of aliphatic iodoalkynes have been studied. Treatment of iodoalkynes with a catalytic amount of In (0.1 equiv) and I(2) (0.05 equiv) promotes atom-transfer 5-exo cyclization to give five-membered alkenyl iodides. In contrast, reaction with In (2 equiv) and I(2) (1 equiv) yields reductive 5-exo cyclization products via the same 5-exo cyclization. Both processes are most likely initiated by low-valent indium species. To demonstrate versatility of these reactions, optically active HIV protease inhibitors were synthesized by this reductive cyclization method. Among them, several products, which contain a hydroxyethylamine dipeptide isostere as a transition state-mimicking substructure, proved to possess potent activity (IC(50) = 5-39 nM) against a wide spectrum of HIV strains, including multidrug-resistant variants.

Combinatorial Chemistry Techniques↗
PubMed2004

Stromal cell-derived factor 1-mediated CXCR4 signaling in rat and human cortical neural progenitor cells.

Stromal cell-derived factor 1 (SDF-1) and the chemokine receptor CXCR4 are highly expressed in the nervous system. Knockout studies have suggested that both SDF-1 and CXCR4 play essential roles in cerebellar, hippocampal, and neocortical neural cell migration during embryogenesis. To extend these observations, CXCR4 signaling events in rat and human neural progenitor cells (NPCs) were examined. Our results show that CXCR4 is expressed in abundance on rat and human NPCs. Moreover, SDF-1alpha induced increased NPCs levels of inositol 1,4,5-triphosphate, extracellular signal-regulated kinases 1/2, Akt, c-Jun N-terminal kinase, and intracellular calcium whereas it diminished cyclic adenosine monophosphate. Finally, SDF-1alpha can induce human NPC chemotaxis in vitro, suggesting that CXCR4 plays a functional role in NPC migration. Both T140, a CXCR4 antagonist, and pertussis toxin (PTX), an inactivator of G protein-coupled receptors, abrogated these events. Ultimately, this study suggested that SDF-1alpha can influence NPC function through CXCR4 and that CXCR4 is functional on NPC.

Animals↗
PubMed2004

Topochemical exploration of potent compounds using retro-enantiomer libraries of cyclic pentapeptides.

Cyclic pentapeptides have been adopted as conformationally restricted peptide templates to dispose pharmacophores of bioactive peptides. In our recent study, use of two orthogonal cyclic pentapeptide libraries involving conformation-based and sequence-based libraries containing critical residues of a bioactive peptide led to the discovery of potent downsized peptides that possess activity comparable to that of the parent peptide. The present study demonstrates that a third library consisting of retro-enantiomers (retro-inverso peptides) that possess not only all residues with the opposite configuration to those in the corresponding original peptide but also amino acid sequences with reversed arrangement, is important as an alternative library for rationally finding active compounds.

Amino Acid Sequence↗
PubMed2004

SmI2-mediated reduction of gamma,gamma-difluoro-alpha,beta-enoates with application to the synthesis of functionalized (Z)-fluoroalkene-type dipeptide isosteres.

A samarium diiodide (SmI(2))-mediated reduction of gamma,gamma-difluoro-alpha,beta-enoates (15, 29, and 34) was successfully applied to the synthesis of (Z)-fluoroalkene dipeptide isosteres (23, 30, and 35), which have served as potential dipeptide mimetics. Reduction of the gamma,gamma-difluoro-alpha,beta-enoates by SmI(2) proceeded via successive two-electron transfers to form dienolate species which upon kinetically controlled trapping with t-BuOH yielded Xaa-Gly-type fluoroalkene isosteres exemplified by 23, 30, and 35. Replacement of the t-BuOH kinetic trapping agent with aldehydes or ketones provided access to alpha-substituted fluoroalkene isosteres (43 and 45) through aldol reactions of Sm-dienolates with the carbonyl compounds. Of particular note, the use of the SmI(2)-HCHO reagent system with chiral enoate 34 provided D-Phe-psi[(Z)-CF[double bond]CH]-D/L-Ser isosteres (45), which could be converted to enantiomerically pure isosteres (49-52) that bore a variety of side chain functionalities at the alpha-position. This was achieved by a sequence of manipulations consisting of beta-lactone formation followed by chromatographic separation and ring-opening with soft nucleophiles. Included in the present work is the first utilization of a Rh-catalyzed Reformatsky reaction of chiral imines for the stereoselective preparation of alpha,alpha-difluoro-beta-amino acid derivatives (28 and 33). The appropriate choice of reagents (carbonyl compounds for kinetic trapping or ring-opening nucleophiles and imines for Reformatsky reactions) allows the presented methodology to yield various fluoroalkene isosteres possessing a wide range of side chain functionalities.

Alkenes↗
PubMed2004

Metastin and its variant forms suppress migration of pancreatic cancer cells.

Metastin, a post-translationally modified variant of KiSS1, was recently identified as an endogenous peptide agonist for a novel G-protein coupled receptor, hOT7T175 (AXOR12, GPR54). In this study, we analyzed the role of KiSS1 and hOT7T175 in both pancreatic cancer tissues and pancreatic cancer cell lines. Furthermore, we synthesized novel short variant forms of metastin and tested the inhibitory effect of those variants on in vitro cell functions that are relevant to metastasis. Pancreatic cancer tissues showed significantly lower expression of KiSS1 mRNA than normal tissues (p=0.018), while cancer tissues showed significantly higher expression of hOT7T175 mRNA than normal pancreatic tissues (p=0.027). In human pancreatic cancer cell lines, KiSS1 mRNA was highly expressed in 2 out of 6 pancreatic cancer cell lines, while hOT7T175 mRNA was expressed in all cell lines at various degrees. PANC-1 cells showed the highest expression of hOT7T175. Exogenous metastin did not suppress cell proliferation but significantly reduced the in vitro migration of PANC-1 cells (p<0.01). Metastin induced activation of ERK1 in PANC-1 and AsPC-1 cells. Finally, we synthesized 3 novel short variant forms of metastin, FM053a2TFA, FM059a2TFA, and FM052a4TFA. These metastin variants significantly suppressed the migration of PANC-1 cells and activated ERK1. These data suggest that the metastin receptor, hOT7T175, is one of the promising targets for suppression of metastasis, and that small metastin variants could be an anti-metastatic agent to pancreatic cancer.

Cell Line, Tumor↗
PubMed2004

Synthesis of fluorine-containing bioisosteres corresponding to phosphoamino acids and dipeptide units.

It has been shown that fluorinated analogues of naturally occurring biological active compounds including amino acids often exhibit unique physiological activity. Among wide varieties of fluorine-containing amino acids, nonhydrolyzable phosphoamino acids possessing a substituent of the difluoromethylene (CF(2)) unit for the phosphoryl ester oxygen are of value in the medicinal and biological fields. We have engaged in the synthesis of these classes of nonhydrolyzable phosphoamino acids corresponding to pTyr 3, pSer 4, and pThr 5 with their incorporation into peptides using newly developed deprotecting procedures. In this article, stereoselective synthesis of the CF(2)-substituted pThr mimetics and development of a two-step deprotecting methodology for the nonhydrolyzable analogues are reviewed. In the course of the above synthetic study, we found that gamma,gamma-difluoro-alpha,beta-enoates were reduced to gamma-fluoro-beta,gamma-enoates by organocopper reagents and then applied to the synthesis of (Z)-fluoroalkene dipeptide isosteres, which have served as potential dipeptide mimetics having structural as well as electrostatic similarity to the parent peptide bonds. Furthermore, mechanistic investigation of the organocopper-mediated reduction led us to development of a SmI(2)-mediated approach toward the synthesis of the fluoroalkene isosteres.

Biomimetic Materials↗
PubMed2004

Stereodivergent synthesis of chiral 2-alkenylaziridines: palladium(0)-catalyzed 2,3-cis-selective aziridination and base-mediated 2,3-trans-selective aziridination.

Whereas treatment of the allylic mesylates of N-protected 2-alkyl-4-amino-(E)-2-alken-1-ols with sodium hydride in DMF yields exclusively the corresponding thermodynamically less stable 2,3-trans-2-alkenyl-3-alkylaziridines, exposure of the methyl carbonates of N-protected 2-alkyl-4-amino-(E)-2-alken-1-ols to a catalytic amount of Pd(PPh(3))(4) in THF or 1,4-dioxane affords predominantly the corresponding thermodynamically more stable 2,3-cis-2-alkenyl-3-alkylaziridines. The kinetically favored trans-selective aziridination would be attributed to the allylic 1,3-strain in aza-anionic intermediates. The conformational analysis of the sterically highly congested 2-alkenylaziridines thus obtained is also presented.

Aziridines↗
PubMed2004

Two orthogonal approaches to overcome multi-drug resistant HIV-1s: development of protease inhibitors and entry inhibitors based on CXCR4 antagonists.

The development of novel drugs active against multi-drug resistant (MDR) HIV-1 strains is urgently required. HIV protease inhibitors and reverse transcriptase inhibitors constitute two categories of important drugs, which have greatly improved the clinical treatment of HIV-infected patients by their cocktail use designated as highly active anti-retroviral therapy (HAART). By combinatorial chemistry involving substructure units contained in known HIV protease inhibitors, we found effective protease inhibitors, TYA5 and TYB5, which showed potent anti-HIV activity even against MDR strains. Selection of drug-resistant viruses is also decreased when these new agents are tested in vitro. Subsequently, introduction of an (E)-alkene dipeptide isostere into TYB5 led to the development of a pure non-peptide protease inhibitor, TYB1. We have also studied the development of effective inhibitors for blocking HIV-entry into host cells based on recent discovery of an HIV entry mechanism involving the viral usage of chemokine receptors as coreceptors, CXCR4 and CCR5. We developed highly selective CXCR4 antagonists, T22 and T140 (18-mer and 14-mer peptides, respectively), which strongly suppress T-cell line-tropic HIV-1 (X4-HIV-1) entry through their specific binding to CXCR4. Recently, molecular-size reduction of T140 yielded low molecular weight CXCR4 antagonists, which might be more useful leads to drug-like structures. In this review, we discuss the development of two types of anti-HIV agents, protease inhibitors and CXCR4 antagonists, which would improve clinical AIDS chemotherapy.

Animals↗
PubMed2004

CXCR4 antagonist inhibits stromal cell-derived factor 1-induced migration and invasion of human pancreatic cancer.

The stromal cell-derived factor-1 (SDF-1)/CXCR4 system is implicated in various instances of cell migration in mammals, including the migration of lymphocytes and the formation of metastases. We have recently synthesized a potent novel CXCR4 antagonist, TN14003. The purpose of this study was to investigate the role of SDF-1/CXCR4 axis in the pancreatic cancer metastasis via cell migration and invasion, and the inhibitory effect of TN14003 on pancreatic cancer cell metastasis. The expression of CXCR4 was detected in six pancreatic cancer cell lines by Western blotting and immunocytochemistry. In migration and invasion assays, SDF-1 stimulated both migration and invasion of cancer cells in a dose-dependent manner. The maximal effect of SDF-1 was observed at 100 ng/ml. SDF-1-induced migration and invasion of cancer cells were completely blocked by 100 nM TN14003. The stimulatory effect of SDF-1 on cancer migration and the inhibitory effect of TN14003 were mediated via the alteration in phosphorylation of mitogen-activated protein kinases. Treatment of cancer cells with 100 ng/ml SDF-1 resulted in a significant increase of actin polymerization, which was reduced by 100 nM TN14003. SDF-1 enhanced cancer cell adhesion to laminin, which was not reversed by TN14003. Taken together, SDF-1/CXCR4 axis is involved in pancreatic cancer metastasis through migration and invasion. The small molecule antagonists against CXCR4 such as TN14003 might be an effective anti-metastatic agent for pancreatic cancer.

Actins↗
PubMed2003

Synthesis of potent CXCR4 inhibitors possessing low cytotoxicity and improved biostability based on T140 derivatives.

A peptidic CXCR4 antagonist T140 efficiently blocks the entry of T cell line-tropic strains of HIV-1 (X4-HIV-1) into target cells. In this study, a series of T140 derivatives, replacing the basic amino acid residues with Glu (D-Glu) and/or L-citrulline (Cit), were synthesized in order to reduce non-specific binding and cytotoxicity. Among them, TE14011 ([Cit6, D-Glu8]-T140 with the C-terminal amide) exhibited strong anti-HIV activity and low cytotoxicity. TE14011 was found to be stable in mouse serum, but unstable in rat liver homogenate due to the deletion of the N-terminal Arg1-Arg2-L-3-(2-naphthyl)alanine (Nal)3 residues from the parent peptide. N-Terminal acetylation of TE14011 led to the development of a novel lead compound, Ac-TE 14011, which possesses a high selectivity index as well as increased stability in serum and liver homogenate.

Amino Acid Sequence↗
PubMed2003

Enhancement of the T140-based pharmacophores leads to the development of more potent and bio-stable CXCR4 antagonists.

A CXCR4 antagonistic peptide, T140, and its bio-stable analogs, such as Ac-TE14011, were previously developed. These peptides inhibit the entry of T cell line-tropic strains of HIV-1 (X4-HIV-1) into T cells. Herein, a series of TE14011 analogs having modifications in the N-terminal region were synthesized to develop effective compounds with increased biostability. Among these analogs, 4F-benzoyl-TE14011 (TF14013) showed the strongest anti-HIV activity derived from CXCR4-antagonism, suggesting that a 4-fluorobenzoyl moiety at the N-terminus of T140 analogs constitutes a novel T140-based pharmacophore for CXCR4 antagonists. Structure-activity relationship (SAR) studies on TE14011 analogs with N(alpha)-acylation by several benzoic acid derivatives have disclosed a significant relationship between the anti-HIV activity and the Hammett constant (sigma) of substituted benzoic acids. TF14013 was found to be stable in mouse serum, but not completely stable in rat liver homogenate due to deletion of the C-terminal Arg14-NH2 from the parent peptide. This biodegradation was completely suppressed by N-alkyl-amidation at the C-terminus. Taken together, the enhancement of the T140-based pharmacophores led to development of a novel CXCR4 antagonist, 4F-benzoyl-TE14011-Me (TF14013-Me), which has very high anti-HIV activity and increased biostability.

Circular Dichroism↗