Encoding and decoding selectivity and promiscuity in the human chemokine-GPCR interaction network

In humans, selective and promiscuous interactions between 46 secreted chemokine ligands and 23 cell surface chemokine receptors of the G-protein-coupled receptor (GPCR) family form a complex network to coordinate cell migration. While chemokines and their GPCRs each share common structural scaffolds, the molecular principles driving selectivity and promiscuity remain elusive. Here, we identify conserved, semi-conserved, and variable determinants (i.e., recognition elements) that are encoded and decoded by chemokines and their receptors to mediate interactions. Selectivity and promiscuity emerge from an ensemble of generalized ("public/conserved") and specific ("private/variable") determinants distributed among structured and unstructured protein regions, with ligands and receptors recognizing these determinants combinatorially. We employ these principles to engineer a viral chemokine with altered GPCR coupling preferences and provide a web resource to facilitate sequence-structure-function studies and protein design efforts for developing immuno-therapeutics and cell therapies.