Elucidation of GlcNAc-binding properties of type III intermediate filament proteins, using GlcNAc-bearing polymers

Vimentin, desmin, glial fibrillary acidic protein (GFAP) and peripherin belong to type III intermediate filament family and are expressed in mesenchymal cells, skeletal muscle cells, astrocytes and peripheral neurons, respectively. Vimentin and desmin possess N-acetyl-d-glucosamine (GlcNAc)-binding properties on cell surfaces. The rod II domain of these proteins is a GlcNAc-binding site, which also exists in GFAP and peripherin. However, the GlcNAc-binding activities and behaviors of these proteins remain unclear. Here, we characterized the interaction and binding behaviors of these proteins, using various well-defined GlcNAc-bearing polymers synthesized by radical polymerization with a reversible addition-fragmentation chain transfer reagent. The small GlcNAc-bearing polymers strongly interacted with HeLa cells through vimentin expressed on the cell surface and interacted with vimentin-, desmin-, GFAP- and peripherin-transfected vimentin-deficient HeLa cells. These proteins present high affinity to GlcNAc-bearing polymers, as shown by surface plasmon resonance. These results show that type III intermediate filament proteins possess GlcNAc-binding activities on cell surfaces. These findings provide important insights into novel cellular functions and physiological significance of type III intermediate filaments.