TY - JOUR
T1 - Extracellular Disulfide Bridges Serve Different Purposes in Two Homologous Chemokine Receptors, CCR1 and CCR5
AU - Rummel, Pia Cwarzko
AU - Thiele, Stefanie
AU - Hansen, Laerke Smidt
AU - Petersen, Trine Puggaard
AU - Sparre-Ulrich, Alexander Hovard
AU - Ulven, Trond
AU - Rosenkilde, Mette Marie
PY - 2013/6/13
Y1 - 2013/6/13
N2 - In addition to the 7TM receptor-conserved disulfide bridge between transmembrane helix (TM) 3 and extracellular loop (ECL) 2, chemokine receptors contain a disulfide bridge between the N-terminus and what previously was believed to be ECL-3. Recent crystal- and NMR-structures of CXCR4 and CXCR1, combined with structural analysis of all endogenous chemokine receptors indicate that this chemokine receptor-conserved bridge in fact connects the N-terminus to the top of TM-7. By employing chemokine ligands that mainly target extracellular receptor regions and small molecule ligands that predominantly interact with residues in the main binding crevice, we show that the 7TM-conserved bridge is essential for all types of ligand-mediated activation, whereas the chemokine-conserved bridge is dispensable for small-molecule activation in CCR1. However, in striking contrast to previous studies in other chemokine receptors, high affinity CCL3 chemokine binding was maintained in the absence of either bridge. In CCR5, the closest homolog to CCR1, a completely different dependency was observed as neither chemokine activation nor binding was retained in the absence of either bridge. In contrast, both bridges where dispensable for small-molecule activation. This indicates that CCR5 activity is independent of extracellular regions, whereas in CCR1, preserved folding of ECL2 is necessary for activation. These results indicate that conserved structural features in a receptor subgroup, does not necessarily provide specific traits for the whole subgroup, but rather provides unique traits to the single receptors.
AB - In addition to the 7TM receptor-conserved disulfide bridge between transmembrane helix (TM) 3 and extracellular loop (ECL) 2, chemokine receptors contain a disulfide bridge between the N-terminus and what previously was believed to be ECL-3. Recent crystal- and NMR-structures of CXCR4 and CXCR1, combined with structural analysis of all endogenous chemokine receptors indicate that this chemokine receptor-conserved bridge in fact connects the N-terminus to the top of TM-7. By employing chemokine ligands that mainly target extracellular receptor regions and small molecule ligands that predominantly interact with residues in the main binding crevice, we show that the 7TM-conserved bridge is essential for all types of ligand-mediated activation, whereas the chemokine-conserved bridge is dispensable for small-molecule activation in CCR1. However, in striking contrast to previous studies in other chemokine receptors, high affinity CCL3 chemokine binding was maintained in the absence of either bridge. In CCR5, the closest homolog to CCR1, a completely different dependency was observed as neither chemokine activation nor binding was retained in the absence of either bridge. In contrast, both bridges where dispensable for small-molecule activation. This indicates that CCR5 activity is independent of extracellular regions, whereas in CCR1, preserved folding of ECL2 is necessary for activation. These results indicate that conserved structural features in a receptor subgroup, does not necessarily provide specific traits for the whole subgroup, but rather provides unique traits to the single receptors.
U2 - 10.1124/mol.113.086702
DO - 10.1124/mol.113.086702
M3 - Journal article
C2 - 23765404
VL - 84
SP - 335
EP - 345
JO - Current Molecular Pharmacology
JF - Current Molecular Pharmacology
SN - 1874-4702
IS - 3
ER -