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LL-37, a cationic antimicrobial peptide, has numerous immune-modulating effects. However, the identity of a receptor that mediates the responses in immune cells remains uncertain. We have recently demonstrated that LL-37 interacts with the αMI-domain of integrin αMβ2 (Mac-1), a major

LL-37, a cationic antimicrobial peptide, has numerous immune-modulating effects. However, the identity of a receptor that mediates the responses in immune cells remains uncertain. We have recently demonstrated that LL-37 interacts with the αMI-domain of integrin αMβ2 (Mac-1), a major receptor on the surface of myeloid cells, and induces a migratory response in Mac-1-expressing monocyte/macrophages as well as activation of Mac-1 on neutrophils. Here, we show that LL-37 and its C-terminal derivative supported strong adhesion of various Mac-1-expressing cells, including human embryonic kidney cells stably transfected with Mac-1, human U937 monocytic cells, and murine IC-21 macrophages. The cell adhesion to LL-37 was partially inhibited by specific Mac-1 antagonists, including monoclonal antibody against the αM integrin subunit and neutrophil inhibitory factor, and completely blocked when anti-Mac-1 antibodies were combined with heparin, suggesting that cell surface heparan sulfate proteoglycans act cooperatively with integrin Mac-1. Coating both gram-negative and gram-positive bacteria with LL-37 significantly potentiated their phagocytosis by macrophages, and this process was blocked by a combination of anti-Mac-1 monoclonal antibody and heparin. Furthermore, phagocytosis by wild-type murine peritoneal macrophages of LL-37-coated latex beads, a model of foreign surfaces, was several fold higher than that of untreated beads. In contrast, LL-37 failed to augment phagocytosis of beads by Mac-1-deficient macrophages. These results identify LL-37 as a novel ligand for integrin Mac-1 and demonstrate that the interaction between Mac-1 on macrophages and bacteria-bound LL-37 promotes phagocytosis.

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    Title
    • Identification of Human Cathelicidin Peptide LL-37 as a Ligand for Macrophage Integrin αMβ2 (Mac-1, CD11b/CD18) That Promotes Phagocytosis by Opsonizing Bacteria
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    Date Created
    2016-07-07
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    Identifier
    • Digital object identifier: 10.2147/RRBC.S107070
    • Identifier Type
      International standard serial number
      Identifier Value
      2230-3154
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    • The final version of this article, as published in Research and Reports in Biochemistry, can be viewed online at: https://www.dovepress.com/identification-of-human-cathelicidin-peptide-ll-37-as-a-ligand-for-mac-peer-reviewed-article-RRBC

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    Ugarova, T., Moreno, B., Podolnikova, N., & Lishko, V. (2016). Identification of human cathelicidin peptide LL-37 as a ligand for macrophage integrin aMb2 (Mac-1, CD11b/CD18) that promotes phagocytosis by opsonizing bacteria. Research and Reports in Biochemistry, Volume 6, 39-55. doi:10.2147/rrbc.s107070

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