Molecular insights into ligand recognition and activation of chemokine receptors CCR2 and CCR3

Abstract

Chemokine receptors are a family of G-protein-coupled receptors with key roles in leukocyte migration and inflammatory responses. Here, we present cryo-electron microscopy structures of two human CC chemokine receptor–G-protein complexes: CCR2 bound to its endogenous ligand CCL2, and CCR3 in the apo state. The structure of the CCL2–CCR2–G-protein complex reveals that CCL2 inserts deeply into the extracellular half of the transmembrane domain, and forms substantial interactions with the receptor through the most N-terminal glutamine. Extensive hydrophobic and polar interactions are present between both two chemokine receptors and the Gα-protein, contributing to the constitutive activity of these receptors. Notably, complemented with functional experiments, the interactions around intracellular loop 2 of the receptors are found to be conserved and play a more critical role in G-protein activation than those around intracellular loop 3. Together, our findings provide structural insights into chemokine recognition and receptor activation, shedding lights on drug design targeting chemokine receptors.

Macrophages and microglia in glioblastoma: heterogeneity, plasticity, and therapy

“…Cancer cell–secreted CCL2 recruits CCR2 + myeloid cells (e.g., TAMs and myeloid-derived suppressor cells) into the GBM TME ( 65 , 66 ). Preclinical data demonstrate that blockade of CCR2 using an antagonist suppresses TAM recruitment and enhances ICI efficacy in GBM mouse models ( 65 , 67 ). Although further studies are needed to evaluate the antitumor efficiency of CCL2/CCR2 axis blockade in GBM patients, it is worth noting that CCL2 neutralizing antibody (e.g., carlumab) shows a modest effect in patients with prostate cancer ( 68 ).…”

Impact of Cancer-Associated Mutations in CC Chemokine Receptor 2 on Receptor Function and Antagonism

“…For example E105Q 23.49 and V107A 23.51 located in ECL1 showed an approximate two-fold decrease in expression, as measured with two different radioligands (Table 2). In silico mutagenesis demonstrated no direct consequences in receptor conformation (data not shown) and ECL1 has been shown not to be involved in chemokine recognition in a recent cryoEM structure of a CCL2-CCR2-Gprotein complex [37]. Hence, the reduced activation is likely related to a decreased receptor expression.…”

“…In silico mutagenesis indicated π-stacking between F116 and T94 that was retained for the F116Y 3.28 mutant but lost for F116V 3.28 , causing a disruption in the orthosteric binding pocket. In the recent cryo-EM structure of the active CCR2 conformation, extensive hydrogen bonding in this area with a direct interaction of the N-terminus of CCL2 to the neighbouring residue T117 3.29 was shown [37]. The reduction in F116V 3.28 activation thus appears to be binary: 1) consisting of a collapse of the orthosteric binding pocket and 2) subsequent reduced interaction with the chemokine N-terminal tail.…”

Illumination of the complement receptors C3aR and C5aR signaling by anaphylatoxins

“…In this paper, we reported the relatively high-resolution structures of C3aR and C5aR1 either in the apo or in the C3a and C5a bound states. These structures provide insight into the unique Cterminus inside binding modes of C3a and C5a to their receptors, in contrast to the Nterminus inside mode occupied by other chemoattractant peptides, such as formylpeptides [59][60][61] and chemokines [51][52][53][54][55][56] . Like many chemokine-bound to their receptors, the N-terminal loop of C5aR1, rather than that of C3aR, serves as important anchoring site for high affinity binding to C5a.…”

“…Similar to chemokines, C3a and C5a belong to large macromolecular ligands of GPCRs and behave as strong chemotaxis for immune cells. The molecular recognition of chemokines to their cognate chemokine receptors were previously investigated [51][52][53][54][55][56] .…”