The carbohydrate-binding protein galectin-3 (Gal3) is an attractive drug target due to its role as a modulator of cell behavior in various pathological processes. However, development of effective Gal3 inhibitors has been hindered by the conserved binding properties of different galectins and the low affinity of monovalent protein-carbohydrate interactions. Immobilizing carbohydrates onto biomaterials can enhance their effectiveness for inhibiting galectins by establishing multivalent avidity effects that increase their apparent galectin-binding affinity. Here, we evaluated a candidate multivalent Gal3 inhibitor based on self-assembled peptide nanofibers modified with N,N’-diacetyllacto... More
The carbohydrate-binding protein galectin-3 (Gal3) is an attractive drug target due to its role as a modulator of cell behavior in various pathological processes. However, development of effective Gal3 inhibitors has been hindered by the conserved binding properties of different galectins and the low affinity of monovalent protein-carbohydrate interactions. Immobilizing carbohydrates onto biomaterials can enhance their effectiveness for inhibiting galectins by establishing multivalent avidity effects that increase their apparent galectin-binding affinity. Here, we evaluated a candidate multivalent Gal3 inhibitor based on self-assembled peptide nanofibers modified with N,N’-diacetyllactosamine (i.e., “LacDiNAc”), a disaccharide that preferentially binds Gal3. QQKFQFQFEQQ (“Q11”) nanofibers modified with LacDiNAc (i.e., “LacDiNAc-Q11”) bound Gal3 with micromolar affinity and selectively captured Gal3 in the presence of galectin-1. However, LacDiNAc-Q11 nanofibers failed to inhibit Jurkat T cell death induced by Gal3 in media supplemented with 10% serum. Unexpectedly, co-precipitation experiments demonstrated that serum glycoproteins blocked Gal3 binding to LacDiNAc-Q11 nanofibers, as well as Q11 nanofibers modified with N-acetyllactosamine (i.e., “LacNAc-Q11”), yet did not affect galectin-1 binding to LacNAc-Q11 nanofibers. When serum content of culture media was reduced, LacDiNAc-Q11 nanofibers inhibited Jurkat T cell agglutination and death induced by Gal3. Collectively, these observations demonstrate that serum glycoproteins can selectively antagonize Gal3 interactions with self-assembled glycopeptide nanofibers, thereby diminishing their effectiveness as Gal3 inhibitors. These studies underscore the need for candidate multivalent Gal3 inhibitors with robust binding selectivity, as well as exceptionally high binding affinity that can disrupt Gal3 interactions with both cell surface glycans and abundant serum glycoproteins.
