Fig. 6

CD44v3 physically interacts with CHI3L1 and IL-13Rα2. a Illustration of CD44 gene and alternative spliced variants (e.g., CD44s, CD44v3, v6 and v9 isoforms) which contain external, transmembrane (TM) and intracellular domain. b The structure of CD44v3 transmembrane protein, which contains the hyaluronic acid (HA) binding sites at the external N-terminal region, a heparin sulfate (HS) assembly site in v3 domain, and the signaling regulator binding sites at the cytoplasmic region. CD44v3 domain amino acid sequences and v3 peptide used in the current study (in red) were listed. c-e Binding of CD44v3 extracellular domain (ECD) (c) or CD44v3 peptide (d and e) to rhCHI3L1 or rhIL-13Rα2 ECD. The binding affinity was evaluated by the absorbance at 450 nm in a direct ELISA. Results shown are representative of a minimum of three independent experiments. The values represent the mean ± SEM in triplicate; *p < 0.05. f and g Measurement of the binding affinity of CD44v3 peptide to rhCHI3L1 (f) or rhIL-13Rα2 ECD (g) by biolayer interferometry (BLI). Various concentrations of CD44v3 peptide were shown. All experiments were performed in triplicate. h Binding of CD44v6 peptide to rhCHI3L1 or rhIL-13Rα2 ECD evaluated by a direct ELISA as describe above. i-j Measurement of the binding affinity of CD44s ECD to rhCHI3L1 (i) or rhIL-13Rα2 ECD (j) by biolayer interferometry (BLI). CD44s ECD was immobilized and CHI3L1 (500 μM) or IL-13Rα2 (500 μM) was in the mobile phase