Abstract:
Chemokines, acting as small chemotactic cytokines, control migration in nearby responsive cells, including macrophages and leukocytes. The molecules are broadly associated with inflammation, angiogenesis, tumor progression and viral infection. Most chemokines enable to form different orders of oligomers, responsible for their functional diversities. Although several oligomerization mechanisms were already reported, lacking of decisive experiment makes the mechanisms unclear. To understand it, we studied an inflammation related chemokine, CCL5. CCL5 shows a strong propensity to polymerize itself in a physiological condition. The aggregation process is important for carbohydrate binding and has been related to apoptosis, T cell activation and HIV cell entry. By testing various mutants, we noticed a novel feature of filamentous CCL5. Later, we proved CCL5 and the other close-related chemokines can aggregate into a huge filament structure. Here, we will demonstrate our strategy starting from determining the CCL5 micro-structure (monomer and dimer) by NMR and X-ray diffraction, and meanwhile, extended our understanding to the CCL5 macro-structure (filament) by using SAXS, TEM and cryo-EM methods. The integration of different methods gives a complete spectrum of how CCL5 polymerizes.