The C-terminal peptide of CCL21 drastically augments CCL21 activity through the dendritic cell lymph node homing receptor CCR7 by interaction with the receptor N-terminus

• DOI: 10.1007/s00018-021-03930-7
• Publication Date: 2021-09-29T05:03:14Z
• Authors: Astrid Sissel Jør...; Emma Probst Brandum; Jeppe Malthe Mikk...; Klaudia A. Orfin; Ditte Rahbæk Boil...; Kristoffer Lihme ...; Natasha A. Mousso...; Frederik Vilhardt; Pawel Kalinski; Per Basse; Yen-Hsi Chen; Zhang Yang; Michael B. Dwinell; Brian F. Volkman; Christopher T. Ve...; Peter Johannes Holst; Katharina Lahl; Christoffer Knak ...; Mette Marie Rosen...; Gertrud Malene Hj...
• Keywords: RECRUITMENT; 0301 basic medicine; Receptors, CCR7; Glycosylation; MIGRATION; Static Electricity; Receptors, Lymphocyte Homing; GRADIENTS; CHO Cells; Ligands; ACTIVATION; 03 medical and health sciences; Cricetulus; Animals; Humans; Cells, Cultured; Chemokine CCL21; RECOGNITION; Dendritic Cells; CHEMOKINE; MOLECULAR-MECHANISM; Chemokine; Peptide; HIGH-AFFINITY BINDING; PATTERNS; Original Article; Lymph Nodes; LIGAND; Peptides; Dendritic cell; CCR7; Protein Binding; Signal Transduction

AbstractThe endogenous chemokines CCL19 and CCL21 signal via their common receptor CCR7. CCL21 is the main lymph node homing chemokine, but a weak chemo-attractant compared to CCL19. Here we show that the 41-amino acid positively charged peptide, released through C-terminal cleavage of CCL21, C21TP, boosts the immune cell recruiting activity of CCL21 by up to 25-fold and the signaling activity via CCR7 by ~ 100-fold. Such boosting is unprecedented. Despite the presence of multiple basic glycosaminoglycan (GAG) binding motifs, C21TP boosting of CCL21 signaling does not involve interference with GAG mediated cell-surface retention. Instead, boosting is directly dependent on O-glycosylations in the CCR7 N-terminus. As dictated by the two-step binding model, the initial chemokine binding involves interaction of the chemokine fold with the receptor N-terminus, followed by insertion of the chemokine N-terminus deep into the receptor binding pocket. Our data suggest that apart from a role in initial chemokine binding, the receptor N-terminus also partakes in a gating mechanism, which could give rise to a reduced ligand activity, presumably through affecting the ligand positioning. Based on experiments that support a direct interaction of C21TP with the glycosylated CCR7 N-terminus, we propose that electrostatic interactions between the positively charged peptide and sialylated O-glycans in CCR7 N-terminus may create a more accessible version of the receptor and thus guide chemokine docking to generate a more favorable chemokine-receptor interaction, giving rise to the peptide boosting effect.