Specific binding sites on human phagocytic blood cells for Gly-Leu-Phe and Val-Glu-Pro-Ile-Pro-Tyr, immunostimulating peptides from human milk proteins

• Published in: Biochimica et biophysica acta Vol. 1160; no. 3; pp. 251 - 261
• Main Authors: Jaziri, M'hamed, Migliore-Samour, Danièle, Casabianca-Pignède, Marie-Rose, Keddad, Karim, Morgat, Jean Louis, Jollès, Pierre
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 28.12.1992; Elsevier
• Subjects: Adjuvants, Immunologic - metabolism; Amino Acid Sequence; Animals; Binding site, Phagocytic cell; Binding Sites; Biological and medical sciences; Cell physiology; Fundamental and applied biological sciences. Psychology; Humans; Immunostimulating peptide; Immunostimulation; Macrophages - metabolism; Mice; Milk peptide; Milk Proteins - chemistry; Milk Proteins - metabolism; Miscellaneous; Molecular and cellular biology; Molecular Sequence Data; Neutrophils - metabolism; Oligopeptides - isolation & purification; Oligopeptides - metabolism; Tritium; Tumor Cells, Cultured - metabolism; Binding site, Phagocytic cell; BSA, bovine serum albumine; Immunostimulation; dhCB, dihydrocytochalasin B; EDTA, ethylenediaminetetraacetic acid; The one-letter amino acid abbreviation system is used. B m , maximum binding capacity; Milk peptide; PBS, phosphate buffered saline; TPA, 12-O- tetradecanoylphorbol; IC 50, concentration giving half-maximal inhibition; PMNL, polymorphonuclear leukocytes; f-MLF, formyl-Met-Leu-Phe; Immunostimulating peptide; DMSO, dimethylsulfoxide; MNL: mononuclear lymphocytes; PMSF, phenylmethylsulfonyl fluoride; MLS, medium for lymphocytes separation; FCS, fetal calf serum; Human; Binding capacity; Monocyte; Plasma membrane; Tripeptide; Scatchard plot; Binding site; Competitive inhibition; Phagocytosis; Blood; Hexapeptide
• ISSN: 0167-4838; 0006-3002; 1879-2588
• DOI: 10.1016/0167-4838(92)90085-R

Two immunostimulating peptides were isolated from human milk proteins by enzymatic digestion, the tripeptide GLF and the hexapeptide VEPIPY. These peptides increased the phagocytosis of human and murine macrophages and protected mice against Klebsiella pneumoniae infection. The present study showed that this activity may be correlated to the presence of specific binding sites on human blood phagocytic cells. The receptor molecules implicated were different for the two peptides. [ 3H]GLF specifically bound to PMNL and monocytes, whereas [ 3H]VEPIPY only bound to monocytes. The leukemic promyelocytic cell line HL-60 differentiated into granulocytes or into macrophages (depending on inducer used) coroborated these results. Specific binding of [ 3H]GLF on plasma membrane preparations of human PMNL (20°C) was saturable and Scatchard analysis indicated two classes of binding sites: high-affinity sites of K d 2.3 ± 1.0 nM and B m 60 ± 9 fmol/ mg protein and low-affinity sites of K d 26.0 ± 3.5 nM and B m 208 ± 45 fmol/ mg protein . [ 3H]GLF binding was inhibited in a concentration-dependent manner by various analogous peptides, such as LLF, GLY, LLY and RGDGLF, but not by RGD, RGDS, VEPIPY and the chemotactic peptide f-Met-Leu-Phe (f-MLF). Only at high concentrations the direct analog MLF competed with labeled GLF. An important inhibitory effect was also observed with C1q component of the complement whereas C3 and BSA were uneffective. Specific binding of [ 3H]VEPIPY on monocyte membranes (20°C) was saturable and Scatchard analysis was consistent with one class of binding sites of K d 3.7 ± 0.3 nM and B m 150 ± 6 fmol/ mg protein .