The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Erkki Ruoslahti - One of the best experts on this subject based on the ideXlab platform.
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a peptide isolated from phage display libraries is a structural and functional mimic of an rgd binding site on integrins
Journal of Cell Biology, 1995Co-Authors: Renata Pasqualini, Erkki Koivunen, Erkki RuoslahtiAbstract:Many integrins recognize short RGD-containing amino acid sequences and such peptide sequences can be identified from phage libraries by panning with an integrin. Here, in a reverse strategy, we have used such libraries to isolate minimal receptor sequences that bind to fibronectin and RGD-containing fibronectin fragments in affinity panning. A predominant cyclic motif, *CWDDG/LWLC*, was obtained (the asterisks denote a potential disulfide bond). Studies using the purified phage and the corresponding synthetic cyclic peptides showed that *CWDDGWLC*-expressing phage binds specifically to fibronectin and to fibronectin fragments containing the RGD sequence. The binding did not require divalent cations and was inhibited by both RGD and *CWDDGWLC*-containing synthetic peptides. Conversely, RGD-expressing phage attached specifically to immobilized *CWDDGWLC*-peptide and the binding could be blocked by the respective synthetic peptides in solution. Moreover, fibronectin bound to a *CWDDGWLC*-peptide affinity column, and could be eluted with an RGD-containing peptide. The *CWDDGWLC*-peptide inhibited RGD-dependent cell attachment to fibronectin and vitronectin, but not to collagen. A region of the beta subunit of RGD-binding integrins that has been previously demonstrated to be involved in ligand binding includes a polypeptide stretch, KDDLW (in beta 3) similar to WDDG/LWL. Synthetic peptides corresponding to this region in beta 3 were found to bind RGD-displaying phage and conversion of its two aspartic residues into alanines greatly reduced the RGD binding. Polyclonal antibodies raised against the *CWDDGWLC*-peptide recognized beta 1 and beta 3 in immunoblots. These data indicate that the *CWDDGWLC*-peptide is a functional mimic of ligand binding sites of RGD-directed integrins, and that the structurally similar site in the integrin beta subunit is a binding site for RGD.
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isolation of a highly specific ligand for the alpha 5 beta 1 integrin from a phage display library
Journal of Cell Biology, 1994Co-Authors: Erkki Koivunen, Bingcheng Wang, Erkki RuoslahtiAbstract:Our previous studies showed that the alpha 5 beta 1 integrin selects cysteine pair-containing RGD peptides from a phage display library based on a random hexapeptide. We have therefore searched for more selective peptides for this integrin using a larger phage display library, where heptapeptides are flanked by cysteine residues, thus making the inserts potentially cyclic. Most of the phage sequences that bound to alpha 5 beta 1 (69 of 125) contained the RGD motif. Some of the heptapeptides contained an NGR motif. As the NGR sequence occurs in the cell-binding region of the fibronectin molecule, this sequence could contribute to the specific recognition of fibronectin by alpha 5 beta 1. Selection for high affinity peptides for alpha 5 beta 1 surprisingly yielded a sequence RRETAWA that does not bear obvious resemblance to known integrin ligand sequences. The synthetic cyclic peptide GACRRETAWACGA (*CRRETAWAC*) was a potent inhibitor of alpha 5 beta 1-mediated cell attachment to fibronectin. This peptide is nearly specific for the alpha 5 beta 1 integrin, because much higher concentrations were needed to inhibit the alpha v beta 1 integrin, and there was no effect on alpha v beta 3- and alpha v beta 5-mediated cell attachment to vitronectin. The peptide also did not bind to the alpha IIb beta 3 integrin. *CRRETAWAC* appears to interact with the same or an overlapping binding site in alpha 5 beta 1 as RGD, because cell attachment to *CRRETAWAC* coated on plastic was divalent cation dependent and could be blocked by an RGD-containing peptide. These results reveal a novel binding specificity in the alpha 5 beta 1 integrin.
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Isolation of a highly specific ligand for the α5β1 integrin from a phage display library
Journal of Cell Biology, 1994Co-Authors: Erkki Koivunen, Bingcheng Wang, Erkki RuoslahtiAbstract:Our previous studies showed that the alpha 5 beta 1 integrin selects cysteine pair-containing RGD peptides from a phage display library based on a random hexapeptide. We have therefore searched for more selective peptides for this integrin using a larger phage display library, where heptapeptides are flanked by cysteine residues, thus making the inserts potentially cyclic. Most of the phage sequences that bound to alpha 5 beta 1 (69 of 125) contained the RGD motif. Some of the heptapeptides contained an NGR motif. As the NGR sequence occurs in the cell-binding region of the fibronectin molecule, this sequence could contribute to the specific recognition of fibronectin by alpha 5 beta 1. Selection for high affinity peptides for alpha 5 beta 1 surprisingly yielded a sequence RRETAWA that does not bear obvious resemblance to known integrin ligand sequences. The synthetic cyclic peptide GACRRETAWACGA (*CRRETAWAC*) was a potent inhibitor of alpha 5 beta 1-mediated cell attachment to fibronectin. This peptide is nearly specific for the alpha 5 beta 1 integrin, because much higher concentrations were needed to inhibit the alpha v beta 1 integrin, and there was no effect on alpha v beta 3- and alpha v beta 5-mediated cell attachment to vitronectin. The peptide also did not bind to the alpha IIb beta 3 integrin. *CRRETAWAC* appears to interact with the same or an overlapping binding site in alpha 5 beta 1 as RGD, because cell attachment to *CRRETAWAC* coated on plastic was divalent cation dependent and could be blocked by an RGD-containing peptide. These results reveal a novel binding specificity in the alpha 5 beta 1 integrin.
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selection of peptides binding to the alpha 5 beta 1 integrin from phage display library
Journal of Biological Chemistry, 1993Co-Authors: Erkki Koivunen, Erkki RuoslahtiAbstract:Abstract The alpha 5 beta 1 integrin binds fibronectin through the integrin recognition sequence Arg-Gly-Asp (RGD). We have used a 6-amino acid peptide library expressed on filamentous phage to identify peptide ligands for alpha 5 beta 1. We found that this integrin selectively binds RGD-containing peptides from the library. Of the 32 different sequences obtained, 28 had the RGD motif, 3 contained sequences related to RGD, and only 1 had a clearly different sequence. One of the RGD-containing phage encoded a potentially cyclic insert CRGDCL. The cyclic peptide GAC*RGDC*LGA (where * denotes cysteines forming a disulfide bond) was 10-fold more efficient than any of the linear RGD-containing hexapeptides in inhibiting the binding of RGD-expressing phage to alpha 5 beta 1 or the attachment of alpha 5 beta 1-expressing cells to fibronectin. This peptide also inhibited cell attachment mediated by the alpha v beta 1, alpha v beta 3, and alpha v beta 5 integrins with about 10-fold higher efficiency than linear GRGDSP. One peptide containing an RGD-related sequence, NGRAHA, was also found to inhibit phage attachment and cell adhesion, especially adhesion mediated by the alpha v beta 5 integrin. These results indicate that novel and high affinity ligands for integrins can be isolated from a random peptide library.
Erkki Koivunen - One of the best experts on this subject based on the ideXlab platform.
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a peptide isolated from phage display libraries is a structural and functional mimic of an rgd binding site on integrins
Journal of Cell Biology, 1995Co-Authors: Renata Pasqualini, Erkki Koivunen, Erkki RuoslahtiAbstract:Many integrins recognize short RGD-containing amino acid sequences and such peptide sequences can be identified from phage libraries by panning with an integrin. Here, in a reverse strategy, we have used such libraries to isolate minimal receptor sequences that bind to fibronectin and RGD-containing fibronectin fragments in affinity panning. A predominant cyclic motif, *CWDDG/LWLC*, was obtained (the asterisks denote a potential disulfide bond). Studies using the purified phage and the corresponding synthetic cyclic peptides showed that *CWDDGWLC*-expressing phage binds specifically to fibronectin and to fibronectin fragments containing the RGD sequence. The binding did not require divalent cations and was inhibited by both RGD and *CWDDGWLC*-containing synthetic peptides. Conversely, RGD-expressing phage attached specifically to immobilized *CWDDGWLC*-peptide and the binding could be blocked by the respective synthetic peptides in solution. Moreover, fibronectin bound to a *CWDDGWLC*-peptide affinity column, and could be eluted with an RGD-containing peptide. The *CWDDGWLC*-peptide inhibited RGD-dependent cell attachment to fibronectin and vitronectin, but not to collagen. A region of the beta subunit of RGD-binding integrins that has been previously demonstrated to be involved in ligand binding includes a polypeptide stretch, KDDLW (in beta 3) similar to WDDG/LWL. Synthetic peptides corresponding to this region in beta 3 were found to bind RGD-displaying phage and conversion of its two aspartic residues into alanines greatly reduced the RGD binding. Polyclonal antibodies raised against the *CWDDGWLC*-peptide recognized beta 1 and beta 3 in immunoblots. These data indicate that the *CWDDGWLC*-peptide is a functional mimic of ligand binding sites of RGD-directed integrins, and that the structurally similar site in the integrin beta subunit is a binding site for RGD.
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isolation of a highly specific ligand for the alpha 5 beta 1 integrin from a phage display library
Journal of Cell Biology, 1994Co-Authors: Erkki Koivunen, Bingcheng Wang, Erkki RuoslahtiAbstract:Our previous studies showed that the alpha 5 beta 1 integrin selects cysteine pair-containing RGD peptides from a phage display library based on a random hexapeptide. We have therefore searched for more selective peptides for this integrin using a larger phage display library, where heptapeptides are flanked by cysteine residues, thus making the inserts potentially cyclic. Most of the phage sequences that bound to alpha 5 beta 1 (69 of 125) contained the RGD motif. Some of the heptapeptides contained an NGR motif. As the NGR sequence occurs in the cell-binding region of the fibronectin molecule, this sequence could contribute to the specific recognition of fibronectin by alpha 5 beta 1. Selection for high affinity peptides for alpha 5 beta 1 surprisingly yielded a sequence RRETAWA that does not bear obvious resemblance to known integrin ligand sequences. The synthetic cyclic peptide GACRRETAWACGA (*CRRETAWAC*) was a potent inhibitor of alpha 5 beta 1-mediated cell attachment to fibronectin. This peptide is nearly specific for the alpha 5 beta 1 integrin, because much higher concentrations were needed to inhibit the alpha v beta 1 integrin, and there was no effect on alpha v beta 3- and alpha v beta 5-mediated cell attachment to vitronectin. The peptide also did not bind to the alpha IIb beta 3 integrin. *CRRETAWAC* appears to interact with the same or an overlapping binding site in alpha 5 beta 1 as RGD, because cell attachment to *CRRETAWAC* coated on plastic was divalent cation dependent and could be blocked by an RGD-containing peptide. These results reveal a novel binding specificity in the alpha 5 beta 1 integrin.
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Isolation of a highly specific ligand for the α5β1 integrin from a phage display library
Journal of Cell Biology, 1994Co-Authors: Erkki Koivunen, Bingcheng Wang, Erkki RuoslahtiAbstract:Our previous studies showed that the alpha 5 beta 1 integrin selects cysteine pair-containing RGD peptides from a phage display library based on a random hexapeptide. We have therefore searched for more selective peptides for this integrin using a larger phage display library, where heptapeptides are flanked by cysteine residues, thus making the inserts potentially cyclic. Most of the phage sequences that bound to alpha 5 beta 1 (69 of 125) contained the RGD motif. Some of the heptapeptides contained an NGR motif. As the NGR sequence occurs in the cell-binding region of the fibronectin molecule, this sequence could contribute to the specific recognition of fibronectin by alpha 5 beta 1. Selection for high affinity peptides for alpha 5 beta 1 surprisingly yielded a sequence RRETAWA that does not bear obvious resemblance to known integrin ligand sequences. The synthetic cyclic peptide GACRRETAWACGA (*CRRETAWAC*) was a potent inhibitor of alpha 5 beta 1-mediated cell attachment to fibronectin. This peptide is nearly specific for the alpha 5 beta 1 integrin, because much higher concentrations were needed to inhibit the alpha v beta 1 integrin, and there was no effect on alpha v beta 3- and alpha v beta 5-mediated cell attachment to vitronectin. The peptide also did not bind to the alpha IIb beta 3 integrin. *CRRETAWAC* appears to interact with the same or an overlapping binding site in alpha 5 beta 1 as RGD, because cell attachment to *CRRETAWAC* coated on plastic was divalent cation dependent and could be blocked by an RGD-containing peptide. These results reveal a novel binding specificity in the alpha 5 beta 1 integrin.
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selection of peptides binding to the alpha 5 beta 1 integrin from phage display library
Journal of Biological Chemistry, 1993Co-Authors: Erkki Koivunen, Erkki RuoslahtiAbstract:Abstract The alpha 5 beta 1 integrin binds fibronectin through the integrin recognition sequence Arg-Gly-Asp (RGD). We have used a 6-amino acid peptide library expressed on filamentous phage to identify peptide ligands for alpha 5 beta 1. We found that this integrin selectively binds RGD-containing peptides from the library. Of the 32 different sequences obtained, 28 had the RGD motif, 3 contained sequences related to RGD, and only 1 had a clearly different sequence. One of the RGD-containing phage encoded a potentially cyclic insert CRGDCL. The cyclic peptide GAC*RGDC*LGA (where * denotes cysteines forming a disulfide bond) was 10-fold more efficient than any of the linear RGD-containing hexapeptides in inhibiting the binding of RGD-expressing phage to alpha 5 beta 1 or the attachment of alpha 5 beta 1-expressing cells to fibronectin. This peptide also inhibited cell attachment mediated by the alpha v beta 1, alpha v beta 3, and alpha v beta 5 integrins with about 10-fold higher efficiency than linear GRGDSP. One peptide containing an RGD-related sequence, NGRAHA, was also found to inhibit phage attachment and cell adhesion, especially adhesion mediated by the alpha v beta 5 integrin. These results indicate that novel and high affinity ligands for integrins can be isolated from a random peptide library.
Bingcheng Wang - One of the best experts on this subject based on the ideXlab platform.
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isolation of a highly specific ligand for the alpha 5 beta 1 integrin from a phage display library
Journal of Cell Biology, 1994Co-Authors: Erkki Koivunen, Bingcheng Wang, Erkki RuoslahtiAbstract:Our previous studies showed that the alpha 5 beta 1 integrin selects cysteine pair-containing RGD peptides from a phage display library based on a random hexapeptide. We have therefore searched for more selective peptides for this integrin using a larger phage display library, where heptapeptides are flanked by cysteine residues, thus making the inserts potentially cyclic. Most of the phage sequences that bound to alpha 5 beta 1 (69 of 125) contained the RGD motif. Some of the heptapeptides contained an NGR motif. As the NGR sequence occurs in the cell-binding region of the fibronectin molecule, this sequence could contribute to the specific recognition of fibronectin by alpha 5 beta 1. Selection for high affinity peptides for alpha 5 beta 1 surprisingly yielded a sequence RRETAWA that does not bear obvious resemblance to known integrin ligand sequences. The synthetic cyclic peptide GACRRETAWACGA (*CRRETAWAC*) was a potent inhibitor of alpha 5 beta 1-mediated cell attachment to fibronectin. This peptide is nearly specific for the alpha 5 beta 1 integrin, because much higher concentrations were needed to inhibit the alpha v beta 1 integrin, and there was no effect on alpha v beta 3- and alpha v beta 5-mediated cell attachment to vitronectin. The peptide also did not bind to the alpha IIb beta 3 integrin. *CRRETAWAC* appears to interact with the same or an overlapping binding site in alpha 5 beta 1 as RGD, because cell attachment to *CRRETAWAC* coated on plastic was divalent cation dependent and could be blocked by an RGD-containing peptide. These results reveal a novel binding specificity in the alpha 5 beta 1 integrin.
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Isolation of a highly specific ligand for the α5β1 integrin from a phage display library
Journal of Cell Biology, 1994Co-Authors: Erkki Koivunen, Bingcheng Wang, Erkki RuoslahtiAbstract:Our previous studies showed that the alpha 5 beta 1 integrin selects cysteine pair-containing RGD peptides from a phage display library based on a random hexapeptide. We have therefore searched for more selective peptides for this integrin using a larger phage display library, where heptapeptides are flanked by cysteine residues, thus making the inserts potentially cyclic. Most of the phage sequences that bound to alpha 5 beta 1 (69 of 125) contained the RGD motif. Some of the heptapeptides contained an NGR motif. As the NGR sequence occurs in the cell-binding region of the fibronectin molecule, this sequence could contribute to the specific recognition of fibronectin by alpha 5 beta 1. Selection for high affinity peptides for alpha 5 beta 1 surprisingly yielded a sequence RRETAWA that does not bear obvious resemblance to known integrin ligand sequences. The synthetic cyclic peptide GACRRETAWACGA (*CRRETAWAC*) was a potent inhibitor of alpha 5 beta 1-mediated cell attachment to fibronectin. This peptide is nearly specific for the alpha 5 beta 1 integrin, because much higher concentrations were needed to inhibit the alpha v beta 1 integrin, and there was no effect on alpha v beta 3- and alpha v beta 5-mediated cell attachment to vitronectin. The peptide also did not bind to the alpha IIb beta 3 integrin. *CRRETAWAC* appears to interact with the same or an overlapping binding site in alpha 5 beta 1 as RGD, because cell attachment to *CRRETAWAC* coated on plastic was divalent cation dependent and could be blocked by an RGD-containing peptide. These results reveal a novel binding specificity in the alpha 5 beta 1 integrin.
Mai Suan Li - One of the best experts on this subject based on the ideXlab platform.
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Inhibition of aggregation of amyloid peptides by beta-sheet breaker peptides and their binding affinity
Journal of Physical Chemistry B, 2011Co-Authors: Man Hoang Viet, Son Tung Ngo, Nguyen Sy Lam, Mai Suan LiAbstract:The effects of beta-sheet breaker peptides KLVFF and LPFFD on the oligomerization of amyloid peptides were studied by all-atom simulations. It was found that LPFFD interferes the aggregation of Aβ16–22 peptides to a greater extent than does KLVFF. Using the molecular mechanics-Poisson–Boltzmann surface area (MM-PBSA) method, we found that the former binds more strongly to Aβ16–22. Therefore, by simulations, we have clarified the relationship between aggregation rates and binding affinity: the stronger the ligand binding, the slower the oligomerization process. The binding affinity of pentapeptides to full-length peptide Aβ1–40 and its mature fibrils has been considered using the Autodock and MM-PBSA methods. The hydrophobic interaction between ligands and receptors plays a more important role for association than does hydrogen bonding. The influence of beta-sheet breaker peptides on the secondary structures of monomer Aβ1–40 was studied in detail, and it turns out that, in their presence, the total beta-s...
Nibaldo C Inestrosa - One of the best experts on this subject based on the ideXlab platform.
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Beta-sheet breaker peptide prevents Abeta-induced spatial memory impairments with partial reduction of amyloid deposits.
Molecular psychiatry, 2004Co-Authors: M A Chacón, M I Barría, C. Soto, Nibaldo C InestrosaAbstract:Current evidence supports the notion that beta-amyloid deposits or Abeta intermediates may be responsible for the pathogenesis in Alzheimer's disease (AD) patients. In the present work, we have assessed the neuroprotective effect of the chronic intraperitoneal administration of a five-amino-acid beta-sheet breaker peptide (iAbeta5p) on the rat behavioral deficit induced by the intrahippocampal Abeta-fibrils injection. At 1 month after the injection, animals showed a partial reduction of the amyloid deposits formed and a decreased astrocytic response around the injection site. More importantly, we report that following the iAbeta5p treatment, hippocampal-dependent spatial learning paradigms, including the standard Morris water maze and a working memory analysis, showed a significant prevention from impairments induced by Abeta deposits in the dorsal hippocampus. Thus, it is possible that a noninvasive treatment such as the one presented here with beta-sheet breaker peptides may be used as a potential therapy for AD patients.
