The Systemic Lupus Erythematosus-Associated Single Nucleotide Polymorphism rs1143678 in Integrin {alpha}M Cytoplasmic Tail Generates a 14-3-3{zeta} Binding Site That Is Proinflammatory [MOLECULAR AND STRUCTURAL IMMUNOLOGY]

Abstract

The leukocyte integrin αMβ2 (CR3 or Mac-1) has both proinflammatory and immune regulatory functions. Genome-wide association studies have identified several ITGAMM subunit) single nucleotide polymorphisms that are associated with systemic lupus erythematosus. The single nucleotide polymorphism rs1143678 substitutes Pro1146 for Ser in the integrin αM cytoplasmic tail. A detailed functional characterization of this substitution is lacking. Using transfected human cell lines, reconstituted mouse bone marrow neutrophils, and bone marrow–derived macrophages (BMDMs), we showed that P1146S (PS) substitution promoted integrin αMβ2–mediated adhesion, spreading, and migration of cells on iC3b and fibrinogen. In the presence of LPS together with iC3b or fibrinogen, the expression levels of IL-6 and TNF-α in integrin αM(PS)β2 BMDMs were significantly higher than those of integrin αM(wild-type)β2 BMDMs, and they showed faster kinetics of Erk1/2 activation through the src family kinase(s)–Syk signaling pathway. Integrin αM(PS)β2 BMDMs also exhibited higher levels of active RhoA and phagocytic activity. Mechanistically, P1146S substitution in the αM cytoplasmic tail generates a noncanonical 14-3-3ζ binding site that modulates integrin αM(PS)β2 outside-in signaling.

Footnotes

  • This work was supported by Ministry of Education, Singapore Grant MOE2010-T2-2-014 (to S.-M.T.) and Nanyang Technological University, Singapore Grant M4081320 (to S.-M.T.).

  • The online version of this article contains supplemental material.

  • Abbreviations used in this article:

    BMDM
    bone marrow–derived macrophage
    CT
    cytoplasmic tail
    eCFP
    enhanced cyan fluorescent protein
    ECIS
    electric cell–substrate impedance sensing
    EI
    expression index
    EV
    empty vector
    eYFP
    enhanced yellow fluorescent protein
    FRET
    fluorescence resonance energy transfer
    HA
    hemagglutinin
    PdBu
    phorbol dibutyrate
    PVDF
    polyvinylidene difluoride
    qRT-PCR
    quantitative RT-PCR
    RBD
    rhotekin binding domain
    RT
    room temperature
    SFK
    Src family kinase
    SLE
    systemic lupus erythematosus
    SNP
    single nucleotide polymorphism
    WT
    wild-type.
  • Received August 19, 2016.
  • Accepted November 16, 2016.

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