title: Stimulation of human formyl peptide receptors by calpain inhibitors: homology modeling of receptors and ligand docking simulation.
abstract: Calpain inhibitors, including peptide aldehydes (N-acetyl-Leu-Leu-Nle-CHO and N-acetyl-Leu-Leu-Met-CHO) and α-mercapto-acrylic acid derivatives (PD150606 and PD151746), have been shown to stimulate phagocyte functions via activation of human formyl peptide receptor (hFPR) and/or hFPR-like 1 (hFPRL1). Using the homology modeling of the receptors and the ligand docking simulation, here we show that these calpain inhibitors could bind to the putative N-formyl-Met-Leu-Phe (fMLF) binding site on hFPR and/or hFPRL1. The studies with HEK-293 cells stably expressing hFPR or hFPRL1 showed that the concentrations of calpain inhibitors required to induce an increase in cytoplasmic free Ca(2+) ([Ca(2+)](i)) was much higher (>100 folds) than those of fMLF and Trp-Lys-Tyr-Met-Val-D-Met (WKYMVm). HEK-293 cells expressing hFPR or hFPRL1 with the mutated fMLF binding site never exhibited the [Ca(2+)](i) response to calpain inhibitors. When the optimal concentrations of each stimulus were used, pretreatment of cells with fMLF or WKYMVm abolished an increase in [Ca(2+)](i) induced by calpain inhibitors as well as the same stimulus, whereas pretreatment of cells with calpain inhibitors significantly suppressed, but never abolished, the [Ca(2+)](i) response induced by fMLF or WKYMVm, suggesting that the binding affinity of the inhibitors to the putative fMLF binding site may be lower than that of fMLF or WKYMVm.
authors: Department of Physiology, Osaka City University, Graduate School of Medicine, Asahi-machi, Abeno-ku, Japan.
authors: Hisakazu
authors: H
authors: Fujita
authors: Takayuki
authors: T
authors: Kato
authors: Norifumi
authors: N
authors: Watanabe
authors: Tatsuji
authors: T
authors: Takahashi
authors: Seiichi
authors: S
authors: Kitagawa
mesh_terms: D000179:Acrylates / Q000494:pharmacology; D001483:Base Sequence; D001665:Binding Sites; D020013:Calcium Signaling / Q000187:drug effects; D003198:Computer Simulation; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D017931:DNA Primers / Q000235:genetics; D006023:Glycoproteins / Q000494:pharmacology*; D057809:HEK293 Cells; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology; D008024:Ligands; D008958:Models, Molecular; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology; D044042:Receptors, Formyl Peptide / Q000737:chemistry* / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D044067:Receptors, Lipoxin / Q000737:chemistry* / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D040681:Structural Homology, Protein
chemical_list: D000179:Acrylates; D015853:Cysteine Proteinase Inhibitors; D017931:DNA Primers; C469986:FPR1 protein, human; C105101:FPR2 protein, human; D006023:Glycoproteins; D007976:Leupeptins; D008024:Ligands; D009842:Oligopeptides; C100442:PD 150606; C117345:PD 151746; D044042:Receptors, Formyl Peptide; D044067:Receptors, Lipoxin; D011994:Recombinant Proteins; C113617:Trp-Lys-Tyr-Met-Val-Met; C039304:calpain inhibitors; C063261:acetylleucyl-leucyl-norleucinal; C069861:calpain inhibitor 2; D009240:N-Formylmethionine Leucyl-Phenylalanine