Fig. 5: CR4 binds preferentially aggregated Aβ.
From: Amyloid-β aggregates activate peripheral monocytes in mild cognitive impairment
a Stacking of 5 parallel beta sheet strands of an Aβ amyloid generated from the PDB entry #6SHS. b The ligand binding αXI domain of CR4 (PDB #4NEH) was docked onto one Glu-3 side chain from the fibril to coordinate the Mg2+ ion (in blue) in the metal ion-dependent adhesion site of the I domain. The other negative charge of the Glu-3 ladder fitted a mainly positively charged groove in the I domain. c Model of the CR4 ectodomain on a cell surface in contact with a segment of a mature Aβ fibril repeating the orientation of CR4 I domain binding site with a periodicity of ∼43 nm. Adhesion to surfaces coated with Aβ by parental K562 cells (d) or with recombinant CR3 (e) or CR4 (f) expression. Surfaces were treated with Gu·HCl or left untreated n = 5 biologically independent experiments; mean ± SEM. Statistical analyses were made in a two-way ANOVA test with Geisser–Greenhouse correction. g, h Monocyte adhesion to aggregated Aβ. g Adhesion was compared in the presence or absence of CD18 integrin-activating KIM127 Ab. Monocytes from n = 3 donors used in biologically independent experiments; mean ± SEM, were using a two-way ANOVA test with Geisser–Greenhouse correction. h Adhesion of CR3 and CR4 was tested using function-blocking Abs ICRF44 and Ab 3.9 to CR3 and CR4, respectively, with isotypic IgG1 Ab as control. Surfaces were coated with Aβ at 2 µg/mL. Monocytes from n = 8 donors were used in biologically independent experiments and analyzed in repeated-measures one-way-ANOVA with Turkey’s correction for multiple comparison; mean ± SEM. SPR analysis of CR3 (i, j) and CR4 I-domain (k, l) binding to aggregated and monomeric Aβ coated at a density of 100 fmol Aβ42/mm2. All sensorgrams were fitted using EVILFIT. The ensemble of 1:1 interactions was distributed according to equilibrium dissociation constant (KD) and dissociation rate (koff) with the abundance in arbitrary resonance units (RU) shown in colors. The total sum of binding (∫∫dkoffdKD) and root-mean-square deviation (rmsd) between the experimental data and the model, both in RU, are indicated for each analysis. All results are representative of three biologically independent experiments. Source data are provided as a Source Data file.
