TY - JOUR
T1 - Dynamics-derived insights into complex formation between the CXCL8 monomer and CXCR1 N-terminal domain
T2 - An NMR study
AU - Joseph, Prem Raj B.
AU - Spyracopoulos, Leo
AU - Rajarathnam, Krishna
N1 - Funding Information:
Funding: This work was supported by grants from the National Institutes of Health P01 HL107152 and S10OD023576, and Sealy and Smith foundation grant to the Sealy Center for Structural Biology and Molecular Biophysics.
Publisher Copyright:
© 2018 by the authors.
PY - 2018/10/31
Y1 - 2018/10/31
N2 - Interleukin-8 (CXCL8), a potent neutrophil-activating chemokine, exerts its function by activating the CXCR1 receptor that belongs to class A G protein-coupled receptors (GPCRs). Receptor activation involves interactions between the CXCL8 N-terminal loop and CXCR1 N-terminal domain (N-domain) residues (Site-I) and between the CXCL8 N-terminal and CXCR1 extracellular/ transmembrane residues (Site-II). CXCL8 exists in equilibrium between monomers and dimers, and it is known that the monomer binds CXCR1 with much higher affinity and that Site-I interactions are largely responsible for the differences in monomer vs. dimer affinity. Here, using backbone 15N-relaxation nuclear magnetic resonance (NMR) data, we characterized the dynamic properties of the CXCL8 monomer and the CXCR1 N-domain in the free and bound states. The main chain of CXCL8 appears largely rigid on the picosecond time scale as evident from high order parameters (S2). However, on average, S2 are higher in the bound state. Interestingly, several residues show millisecond-microsecond (ms-µs) dynamics only in the bound state. The CXCR1 N-domain is unstructured in the free state but structured with significant dynamics in the bound state. Isothermal titration calorimetry (ITC) data indicate that both enthalpic and entropic factors contribute to affinity, suggesting that increased slow dynamics in the bound state contribute to affinity. In sum, our data indicate a critical and complex role for dynamics in driving CXCL8 monomer-CXCR1 Site-I interactions.
AB - Interleukin-8 (CXCL8), a potent neutrophil-activating chemokine, exerts its function by activating the CXCR1 receptor that belongs to class A G protein-coupled receptors (GPCRs). Receptor activation involves interactions between the CXCL8 N-terminal loop and CXCR1 N-terminal domain (N-domain) residues (Site-I) and between the CXCL8 N-terminal and CXCR1 extracellular/ transmembrane residues (Site-II). CXCL8 exists in equilibrium between monomers and dimers, and it is known that the monomer binds CXCR1 with much higher affinity and that Site-I interactions are largely responsible for the differences in monomer vs. dimer affinity. Here, using backbone 15N-relaxation nuclear magnetic resonance (NMR) data, we characterized the dynamic properties of the CXCL8 monomer and the CXCR1 N-domain in the free and bound states. The main chain of CXCL8 appears largely rigid on the picosecond time scale as evident from high order parameters (S2). However, on average, S2 are higher in the bound state. Interestingly, several residues show millisecond-microsecond (ms-µs) dynamics only in the bound state. The CXCR1 N-domain is unstructured in the free state but structured with significant dynamics in the bound state. Isothermal titration calorimetry (ITC) data indicate that both enthalpic and entropic factors contribute to affinity, suggesting that increased slow dynamics in the bound state contribute to affinity. In sum, our data indicate a critical and complex role for dynamics in driving CXCL8 monomer-CXCR1 Site-I interactions.
KW - CXCL8
KW - CXCR1
KW - Chemokine
KW - Dynamics
KW - G protein-coupled receptor (GPCR)
KW - Isothermal titration calorimetry (ITC)
KW - N-relaxation
KW - Nuclear magnetic resonance (NMR)
KW - Receptor interactions
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U2 - 10.3390/molecules23112825
DO - 10.3390/molecules23112825
M3 - Article
C2 - 30384436
AN - SCOPUS:85055916876
VL - 23
JO - Molecules
JF - Molecules
SN - 1420-3049
IS - 11
ER -