ABSTRACT
QK peptide is a vascular endothelial growth factor (VEGF)-mimetic molecule with significant proangiogenic activity. In particular, QK is able to bind and activate VEGF receptors (VEGFRs) to stimulate a functional response in endothelial cells. To characterize the peptide bioactivity and its molecular recognition properties, a detailed picture of the interaction between peptide QK and VEGF receptors is reported. By combining NMR spectroscopy studies in solution on the purified receptor and in the presence of intact endothelial cells, a molecular description of the binding interaction between peptide QK and VEGFR2 in the cellular context is obtained. These results reveal useful insights into the peptide biological mechanism, which opens the way to further optimization of this class of VEGF-mimicking peptides.
Subject(s)
Biomimetic Materials/chemistry , Peptides/chemistry , Receptors, Vascular Endothelial Growth Factor/chemistry , Vascular Endothelial Growth Factor A/chemistry , Endothelial Cells , Magnetic Resonance Spectroscopy , Models, Molecular , Protein Binding , Protein ConformationABSTRACT
Molecular tools to stabilize the ß-hairpin conformation are needed as ß-hairpin peptides are useful molecules for pharmaceutical, biological and materials applications. We explored the use of a "triazole bridge", a covalent link between two ß-hairpin strands obtained through Cu-catalyzed alkyne-azide cycloaddition, combined with an aromatic-aromatic interaction. Highly conformationally stable peptides were identified by NMR screening of a small collection of cyclic peptides based on the Trpzip2 scaffold. The characteristic Trp-Trp interaction of Trpzip2 was replaced by a diagonal triazole bridge of variable length. NMR and CD analyses showed that triazole and indole rings could favorably interact to stabilize a ß-hairpin conformation. The conformational stabilization depends on the length of the triazole bridge and the reciprocal position between the aromatic rings. Combining aromatic interactions and the covalent inter-strand triazole bridge is a useful strategy to obtain peptides with a high ß-hairpin content.
Subject(s)
Peptides/chemistry , Triazoles/chemistry , Tryptophan/chemistry , Amino Acid Sequence , Catalysis , Copper/chemistry , Cycloaddition Reaction , Peptides/chemical synthesis , Peptides, Cyclic/chemical synthesis , Peptides, Cyclic/chemistry , Protein Conformation, beta-Strand , Protein Stability , Thermodynamics , Triazoles/chemical synthesis , Tryptophan/chemical synthesisABSTRACT
The ability to modulate angiogenesis by chemical tools has several important applications in different scientific fields. With the perspective of finding novel proangiogenic molecules, we searched peptide sequences with a chemical profile similar to that of the QK peptide, a well described VEGF mimetic peptide. We found that residues 1617-1627 of the IQGAP1 protein show molecular features similar to those of the QK peptide sequence. The IQGAP1-derived synthetic peptide was analyzed by NMR spectroscopy and its biological activity was characterized in endothelial cells. These studies showed that this IQGAP1-derived peptide has a biological activity similar to that of VEGF and could be considered as a novel tool for reparative angiogenesis.
Subject(s)
Angiogenesis Inducing Agents/pharmacology , Endothelial Cells/drug effects , Human Umbilical Vein Endothelial Cells/drug effects , Peptides/pharmacology , Vascular Endothelial Growth Factor A/pharmacology , ras GTPase-Activating Proteins/chemistry , Amino Acid Sequence , Angiogenesis Inducing Agents/chemical synthesis , Animals , Aorta/cytology , Aorta/drug effects , Aorta/metabolism , Caspase 3/genetics , Caspase 3/metabolism , Cell Line, Transformed , Cell Proliferation/drug effects , Endothelial Cells/cytology , Endothelial Cells/metabolism , Gene Expression Regulation , Human Umbilical Vein Endothelial Cells/cytology , Human Umbilical Vein Endothelial Cells/metabolism , Humans , Molecular Mimicry , Neovascularization, Physiologic/drug effects , Peptides/chemical synthesis , Protein Conformation, alpha-Helical , Swine , Vascular Endothelial Growth Factor A/chemistry , Vascular Endothelial Growth Factor Receptor-1/genetics , Vascular Endothelial Growth Factor Receptor-1/metabolism , Vascular Endothelial Growth Factor Receptor-2/genetics , Vascular Endothelial Growth Factor Receptor-2/metabolismABSTRACT
Vascular Endothelial Growth Factor mimetic peptides have interesting applications in therapeutic angiogenesis. Recently, we described the proangiogenic properties of a 15 mer peptide designed on the N-terminal helix 17-25 of VEGF. The peptide was stabilized introducing well known peptide chemical tools among which N- and C-terminal capping sequence. Here, we show that the C-terminal sequence does not affect the structural and biological properties of the full-length peptide. In fact, a C-terminal truncated analog peptide resulted in a well folded and stable helix retaining the ability to bind to VEGF receptors. This study will allow to develop smaller peptidomimetic analogs able to modulate the VEGF-dependent angiogenesis.
Subject(s)
Biomimetic Materials/chemistry , Neovascularization, Pathologic/metabolism , Neovascularization, Physiologic/drug effects , Peptides/chemistry , Vascular Endothelial Growth Factor A/chemistry , Vascular Endothelial Growth Factor Receptor-1/chemistry , Biomimetic Materials/pharmacology , Cell Line, Tumor , Circular Dichroism , Humans , Nuclear Magnetic Resonance, Biomolecular , Peptides/pharmacology , Protein Binding , Protein Structure, Secondary , Vascular Endothelial Growth Factor A/pharmacologyABSTRACT
ß-Hairpin peptides were conformationally stabilized through a 1,4 disubstituted 1,2,3-triazole interstrand linkage. A NMR conformational analysis revealed that the ß-hairpin content depends on the number and position of substituent methylene units of the 1,2,3-triazole ring. These results will allow the design of metabolically stable peptidomimetic analogs of bioactive ß-hairpin peptides.