Structural basis for oligomerization and glycosaminoglycan binding of CCL5 and CCL3.
CC chemokine ligand 5 (CCL5) and CCL3 are critical for immune surveillance and inflammation. Consequently, they are linked to the pathogenesis of many inflammatory conditions and are therapeutic targets. Oligomerization and glycosaminoglycan (GAG) binding of CCL5 and CCL3 are vital for the functions of these chemokines. Our structural and biophysical analyses of human CCL5 reveal that CCL5 oligomerization is a polymerization process in which CCL5 forms rod-shaped, double-helical oligomers. This CCL5 structure explains mutational data and offers a unified mechanism for CCL3, CCL4, and CCL5 assembly into high-molecular-weight, polydisperse oligomers. A conserved, positively charged BBXB motif is key for the binding of CC chemokines to GAG. However, this motif is partially buried when CCL3, CCL4, and CCL5 are oligomerized; thus, the mechanism by which GAG binds these chemokine oligomers has been elusive. Our structures of GAG-bound CCL5 and CCL3 oligomers reveal that these chemokine oligomers have distinct GAG-binding mechanisms. The CCL5 oligomer uses another positively charged and fully exposed motif, KKWVR, in GAG binding. However, residues from two partially buried BBXB motifs along with other residues combine to form a GAG-binding groove in the CCL3 oligomer. The N termini of CC chemokines are shown to be involved in receptor binding and oligomerization. We also report an alternative CCL3 oligomer structure that reveals how conformational changes in CCL3 N termini profoundly alter its surface properties and dimer-dimer interactions to affect GAG binding and oligomerization. Such complexity in oligomerization and GAG binding enables intricate, physiologically relevant regulation of CC chemokine functions.
Ben May Department for Cancer Research, The University of Chicago, Chicago, IL 60637;
Wenguang G
WG
Liang
Graduate Program in Biophysical Sciences, The University of Chicago, Chicago, IL 60637;
Catherine G
CG
Triandafillou
Genomics Research Center, Academia Sinica, Taipei 115, Taiwan;
Teng-Yi
TY
Huang
Genomics Research Center, Academia Sinica, Taipei 115, Taiwan;
Medel Manuel L
MM
Zulueta
James Franck Institute, The University of Chicago, Chicago, IL 60637;
Shiladitya
S
Banerjee
James Franck Institute, The University of Chicago, Chicago, IL 60637; Department of Chemistry, The University of Chicago, Chicago, IL 60637.
Aaron R
AR
Dinner
Genomics Research Center, Academia Sinica, Taipei 115, Taiwan; schung@gate.sinica.edu.tw wtang@uchicago.edu.
Shang-Cheng
SC
Hung
Ben May Department for Cancer Research, The University of Chicago, Chicago, IL 60637; schung@gate.sinica.edu.tw wtang@uchicago.edu.
Wei-Jen
WJ
Tang
D001665:Binding Sites; D054405:Chemokine CCL3 / Q000737:chemistry* / Q000648:ultrastructure*; D018946:Chemokine CCL5 / Q000737:chemistry* / Q000648:ultrastructure*; D019281:Dimerization; D006025:Glycosaminoglycans / Q000737:chemistry*; D006801:Humans; D011485:Protein Binding; D011487:Protein Conformation; D013329:Structure-Activity Relationship
C515429:CCL3 protein, human; C483024:CCL5 protein, human; D054405:Chemokine CCL3; D018946:Chemokine CCL5; D006025:Glycosaminoglycans
CC chemokine; X-ray crystallography; glycosaminoglycan; protein oligomerization; signal transduction