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Hypofibrinolytic effects of complement C3 and its modulation
tion of fibrin clot lysis by interfering with fibrinogen-C3 interactions.
While C3 protein purified from individual plasma sam- ples consistently prolonged clot lysis, an inter-individual variability in the response was noted, which may be relat- ed to the degree of incorporation of C3 into the clot.19 This was particularly pronounced in C3 purified from patients with diabetes, which may be related to alternative post- translational modifications in the protein. We identified
AB
six lysine residues that were glycated in samples from patients with type 1 diabetes, but not in samples from controls. The variability in glycation sites comparing indi- viduals with type 1 diabetes suggests that the ability of lysine residues on C3 to undergo glycation has a large inter-individual variability, which may modulate the antifibrinolytic effects of the protein. Interestingly, in vitro glycation of C3 showed largely similar patterns, favoring glycation of certain lysine residues, suggesting this consis-
CD
Figure 4. Modulation of C3-induced prolongation of fibrinolysis by affimer A6 and pontential inter- action sites on fibrino- gen. (A) Pre-incubation of fibrinogen with affimer A6 completely abolished complement C3-mediated prolongation of lysis with no effect observed on prolongation of lysis by plasmin inhibitor indicat- ing a C3-specific effect. (B) Dose-response curve using different molar ratios of affimer A6:fib- rinogen (or scaffold-only control protein), conduct- ed on pooled plasma samples from 12 individu- als. (C) Effects of affimer A6 on plasma clot lysis using pooled healthy con- trol plasma (control, n=12) or plasma from patients with type 1 dia- betes (patients, n=12). Results represent the mean ± standard error of mean of three independ- ent experiments each per-
E
formed in
unpaired t-test. (D) The effect of affimer A6 on plasma clot lysis in 24 patients with high vascu- lar risk (11 with coronary artery disease and 13 with type 2 diabetes). (E) The crystal structure of fibrinogen with predicted binding sites of loop 1 (red) and loop 2 (blue) of affimer A6 within the b chain (shown in green), lying in close proximity to peptide motifs B and C identified from microarray screening (colored spheres). C3: comple- ment C3; A6: affimer A6; PI: plasmin inhibitor; T1D: type 1 diabetes; CVD: car- diovascular disease; DM: diabetes mellitus.
duplicate,
haematologica | 2021; 106(6)
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