Integrative model to coordinate the oligomerization and aggregation mechanisms of CCL5

The CC-type chemokine ligand 5 (CCL5) is involved in the pathogenesis of many inflammatory conditions. The oligomerization and aggregation of CCL5 are considered to be responsible for its inflammatory properties. The CC-type dimer acts as the basic unit to constitute the oligomer. However, the structural basis of CCL5 oligomerization remains controversial. In this study, NMR and biophysical analyses proposed evidence that no single dimer-dimer interaction dominates in the oligomerization process of CCL5. CCL5 could oligomerize alternatively through two different interactions, E66-K25 and E66-R44/K45. In addition, a newly determined trimer structure reported an interfacial interaction through the N-terminal 12 FAY 14 sequence. The interaction contributes to aggregation and precipitation. In accordance with the observations, an integrative model explains the CCL5 oligomerization and aggregation process. CCL5 assembly consists of two types of dimer-dimer interactions and one aggregation mechanism. For full-length CCL5, the molecular accumulation triggers oligomerization through the E66-K25 interaction, and the 12 FAY 14 interaction acts as a secondary effect to derive aggregation. The E66-R44/K45 interaction dominates in CCL5 N-terminal truncations. The interaction would lead to filament-like formation in solution.