TY - JOUR

T1 - Structural Features of an Extended C-Terminal Tail Modulate the Function of the Chemokine CCL21

AU - Moussouras, Natasha A.

AU - Hjortø, Gertrud M.

AU - Peterson, Francis C.

AU - Szpakowska, Martyna

AU - Chevigné, Andy

AU - Rosenkilde, Mette M.

AU - Volkman, Brian F.

AU - Dwinell, Michael B.

PY - 2020/4/7

Y1 - 2020/4/7

N2 - The chemokines CCL21 and CCL19, through binding of their cognate receptor CCR7, orchestrate lymph node homing of dendritic cells and naïve T cells. CCL21 differs from CCL19 via an unstructured 32 residue C-terminal domain. Previously described roles for the CCL21 C-terminus include GAG-binding, spatial localization to lymphatic vessels, and autoinhibitory modulation of CCR7-mediated chemotaxis. While truncation of the C-terminal tail induced chemical shift changes in the folded chemokine domain, the structural basis for its influence on CCL21 function remains largely unexplored. CCL21 concentration-dependent NMR chemical shifts revealed weak, nonphysiological self-association that mimics the truncation of the C-terminal tail. We generated a series of C-terminal truncation variants to dissect the C-terminus influence on CCL21 structure and receptor activation. Using NMR spectroscopy, we found that CCL21 residues 80-90 mediate contacts with the chemokine domain. In cell-based assays for CCR7 and ACKR4 activation, we also found that residues 92-100 reduced CCL21 potency in calcium flux, cAMP inhibition, and β-arrestin recruitment. Taken together, these structure-function studies support a model wherein intramolecular interactions with specific residues of the flexible C-terminus stabilize a less active monomer conformation of the CCL21. We speculate that the autoinhibitory intramolecular contacts between the C-terminal tail and chemokine body are disrupted by GAG binding and/or interactions with the CCR7 receptor to ensure optimal functionality.

AB - The chemokines CCL21 and CCL19, through binding of their cognate receptor CCR7, orchestrate lymph node homing of dendritic cells and naïve T cells. CCL21 differs from CCL19 via an unstructured 32 residue C-terminal domain. Previously described roles for the CCL21 C-terminus include GAG-binding, spatial localization to lymphatic vessels, and autoinhibitory modulation of CCR7-mediated chemotaxis. While truncation of the C-terminal tail induced chemical shift changes in the folded chemokine domain, the structural basis for its influence on CCL21 function remains largely unexplored. CCL21 concentration-dependent NMR chemical shifts revealed weak, nonphysiological self-association that mimics the truncation of the C-terminal tail. We generated a series of C-terminal truncation variants to dissect the C-terminus influence on CCL21 structure and receptor activation. Using NMR spectroscopy, we found that CCL21 residues 80-90 mediate contacts with the chemokine domain. In cell-based assays for CCR7 and ACKR4 activation, we also found that residues 92-100 reduced CCL21 potency in calcium flux, cAMP inhibition, and β-arrestin recruitment. Taken together, these structure-function studies support a model wherein intramolecular interactions with specific residues of the flexible C-terminus stabilize a less active monomer conformation of the CCL21. We speculate that the autoinhibitory intramolecular contacts between the C-terminal tail and chemokine body are disrupted by GAG binding and/or interactions with the CCR7 receptor to ensure optimal functionality.

U2 - 10.1021/acs.biochem.0c00047

DO - 10.1021/acs.biochem.0c00047

M3 - Journal article

C2 - 32182428

AN - SCOPUS:85083041593

VL - 59

SP - 1338

EP - 1350

JO - Biochemistry

JF - Biochemistry

SN - 0006-2960

IS - 13

ER -