Soluble CD40L activates soluble and cell-surface integrin αvβ3, α5β1, and α4β1 by binding to the allosteric ligand-binding site (site 2)

Journal of Biological Chemistry · 2021 · 27 citations

• Chemistry
• Biophysics
• Cell biology

CD40L is a member of the TNF superfamily that participates in immune cell activation. It binds to and signals through several integrins, including αvβ3 and α5β1, which bind to the trimeric interface of CD40L. We previously showed that several integrin ligands can bind to the allosteric site (site 2), which is distinct from the classical ligand-binding site (site 1), raising the question of if CD40L activates integrins. In our explorations of this question, we determined that integrin α4β1, which is prevalently expressed on the same CD4+ T cells as CD40L, is another receptor for CD40L. Soluble (s)CD40L activated soluble integrins αvβ3, α5β1, and α4β1 in cell-free conditions, indicating that this activation does not require inside-out signaling. Moreover, sCD40L activated cell-surface integrins in CHO cells that do not express CD40. To learn more about the mechanism of binding, we determined that sCD40L bound to a cyclic peptide from site 2. Docking simulations predicted that the residues of CD40L that bind to site 2 are located outside of the CD40L trimer interface, at a site where four HIGM1 (hyper-IgM syndrome type 1) mutations are clustered. We tested the effect of these mutations, finding that the K143T and G144E mutants were the most defective in integrin activation, providing support that this region interacts with site 2. We propose that allosteric integrin activation by CD40L also plays a role in CD40L signaling, and defective site 2 binding may be related to the impaired CD40L signaling functions of these HIGM1 mutants.

Anti-Monomeric C-Reactive Protein Antibody Ameliorates Arthritis and Nephritis in Mice

The Journal of Immunology · 2021 · 21 citations

• Medicine
• Immunology
• Pathology

Conformation-specific Ags are ideal targets for mAb-based immunotherapy. Here, we demonstrate that the monomeric form of C-reactive protein (mCRP) is a specific therapeutic target for arthritis and nephritis in a murine model. Screening of >1800 anti-mCRP mAb clones identified 3C as a clone recognizing the monomeric, but not polymeric, form of CRP. The anti-mCRP mAb suppressed leukocyte infiltration in thioglycollate-induced peritonitis, attenuated rheumatoid arthritis symptoms in collagen Ab-induced arthritis model mice, and attenuated lupus nephritis symptoms in MRL/Mp-lpr/lpr lupus-prone model mice. These data suggest that the anti-mCRP mAb 3C has therapeutic potential against rheumatoid arthritis and lupus nephritis.

Histological and Immunohistochemical Features of Normal Histiocytes and Langerhans Cells, and Histiocytic Sarcomas in Four-Toed Hedgehogs (Atelerix albiventris)

Journal of Comparative Pathology · 2020 · 13 citations

• Pathology
• Biology
• Medicine