Binding and internalization of an ICAM-1 peptide by the surface receptors of T cells.
The objective of this work was to evaluate the binding characteristics of a cyclic peptide, cyclo (1, 12)-Pen1-Pro2-Arg3-Gly4-Gly5-Ser6-Val7-Leu8-V al9-Thr10-Gly11-Cys12-OH (cIBR), to Molt-3 T cells. This cIBR peptide is derived from sequence numbers 11-20 of intercellular adhesion molecule-1 (ICAM-1). Binding studies were performed using a fluorescence-labeled peptide (FITC-cIBR) in which the fluorescence marker fluorescein 5-isothiocyanate (FITC) was conjugated to the N-terminal of the cIBR peptide. The binding affinity of the FITC-cIBR peptide to Molt-3 T cells was evaluated using a FACScan flow cytometer. The binding specificity of the FITC-cIBR peptide was also confirmed by inhibition of binding using unlabeled peptide (cIBR). The results show that FITC-cIBR binds to two populations of T cells with different affinities; population 1 has high cell numbers (75%) but low affinity, and population 2 has high binding affinity but low cell numbers (25%). Binding to both populations was saturable and could be inhibited by the unlabeled peptide (cIBR), suggesting a receptor-mediated binding process. In addition to binding, receptor-mediated internalization was also observed for population 2; this was confirmed by confocal microscopy and temperature-dependence studies at 37 degrees C and 4 degrees C. The binding and internalization of this peptide may be carried out by surface receptors on Molt-3 T cells such as LFA-1. In the future, the binding and internalization of cIBR peptide can be utilized as a method of targeted drug delivery to leukocytes for the treatment of leukocyte-related diseases.
Department of Pharmaceutical Chemistry, The University of Kansas, Lawrence 66047, USA.
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Gürsoy
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Siahaan
D000595:Amino Acid Sequence; D002118:Calcium / Q000494:pharmacology; D005434:Flow Cytometry / Q000379:methods; D016650:Fluorescein-5-isothiocyanate / Q000737:chemistry; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000737:chemistry / Q000378:metabolism*; D007938:Leukemia / Q000188:drug therapy / Q000378:metabolism; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism; D008274:Magnesium / Q000494:pharmacology; D018613:Microscopy, Confocal; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D011948:Receptors, Antigen, T-Cell / Q000187:drug effects / Q000378:metabolism*; D013696:Temperature; D014407:Tumor Cells, Cultured
D016169:Lymphocyte Function-Associated Antigen-1; D010446:Peptide Fragments; D010456:Peptides, Cyclic; D011948:Receptors, Antigen, T-Cell; D018799:Intercellular Adhesion Molecule-1; D016650:Fluorescein-5-isothiocyanate; D008274:Magnesium; D002118:Calcium