tc14012 and plerixafor

The role of dimerization and oligomerization of G-protein-coupled receptors in their signal transduction is highly controversial. Delineating this issue can greatly facilitate rational drug design. With single-molecule imaging, we show that chemokine receptor CXCR4 exists mainly as a monomer in normal mammalian living cells and forms dimers and higher-order oligomers at a high expression level, such as in cancer cells. Chemotaxis tests demonstrate that the signal transduction activity of CXCR4 does not depend only on its expression level, indicating a close relation with the oligomeric status of CXCR4. Moreover, binding ligands can effectively upregulate or downregulate the oligomeric level of CXCR4, which suggests that binding ligands may realize their pivotal roles by regulating the oligomeric status of CXCR4 rather than by simply inducing conformational changes.

Topics: Benzylamines; Cell Line, Transformed; Cell Line, Tumor; Chemokine CXCL12; Cyclams; Heterocyclic Compounds; Humans; Ligands; Microscopy, Fluorescence; Oligopeptides; Protein Multimerization; Receptors, CXCR4

Chemokine (C-X-C motif) receptor (CXCR) 4 and atypical chemokine receptor (ACKR) 3 ligands have been reported to modulate cardiovascular function in various disease models. The underlying mechanisms, however, remain unknown. Thus, it was the aim of the present study to determine how pharmacological modulation of CXCR4 and ACKR3 regulate cardiovascular function. In vivo administration of TC14012, a CXCR4 antagonist and ACKR3 agonist, caused cardiovascular collapse in normal animals. During the cardiovascular stress response to hemorrhagic shock, ubiquitin, a CXCR4 agonist, stabilized blood pressure, whereas coactivation of CXCR4 and ACKR3 with CXC chemokine ligand 12 (CXCL12), or blockade of CXCR4 with AMD3100 showed opposite effects. While CXCR4 and ACKR3 ligands did not affect myocardial function, they selectively altered vascular reactivity upon α1-adrenergic receptor (AR) activation in pressure myography experiments. CXCR4 activation with ubiquitin enhanced α1-AR-mediated vasoconstriction, whereas ACKR3 activation with various natural and synthetic ligands antagonized α1-AR-mediated vasoconstriction. The opposing effects of CXCR4 and ACKR3 activation by CXCL12 could be dissected pharmacologically. CXCR4 and ACKR3 ligands did not affect vasoconstriction upon activation of voltage-operated Ca(2+) channels or endothelin receptors. Effects of CXCR4 and ACKR3 agonists on vascular α1-AR responsiveness were independent of the endothelium. These findings suggest that CXCR4 and ACKR3 modulate α1-AR reactivity in vascular smooth muscle and regulate hemodynamics in normal and pathological conditions. Our observations point toward CXCR4 and ACKR3 as new pharmacological targets to control vasoreactivity and blood pressure.

Topics: Adrenergic Agonists; Animals; Benzylamines; Blood Pressure; Chemokine CXCL12; Cyclams; Heterocyclic Compounds; In Vitro Techniques; Ligands; Male; Mesenteric Arteries; Myocytes, Cardiac; Oligopeptides; Phenylephrine; Rats, Inbred Lew; Receptors, Adrenergic, alpha-1; Receptors, CXCR; Receptors, CXCR4; Shock, Hemorrhagic; Ubiquitin; Vasoconstriction; Ventricular Function, Left

CXCL12 and VCAM1 retain hematopoietic stem cells (HSCs) in the BM, but the factors mediating HSC egress from the BM to the blood are not known. The sphingosine-1-phosphate receptor 1 (S1P(1)) is expressed on HSCs, and S1P facilitates the egress of committed hematopoietic progenitors from the BM into the blood. In the present study, we show that both the S1P gradient between the BM and the blood and the expression of S1P(1) are essential for optimal HSC mobilization by CXCR4 antagonists, including AMD3100, and for the trafficking of HSCs during steady-state hematopoiesis. We also demonstrate that the S1P(1) agonist SEW2871 increases AMD3100-induced HSC and progenitor cell mobilization. These results suggest that the combination of a CXCR4 antagonist and a S1P(1) agonist may prove to be sufficient for mobilizing HSCs in normal donors for transplantation purposes, potentially providing a single mobilization procedure and eliminating the need to expose normal donors to G-CSF with its associated side effects.

Topics: Adult; Aged; Animals; Anti-HIV Agents; Benzylamines; Blotting, Western; Cell Movement; Cell Proliferation; Cells, Cultured; Chemokine CXCL12; Cyclams; Cytokines; Drug Combinations; Drug Synergism; Female; Granulocyte Colony-Stimulating Factor; Hematopoietic Stem Cell Mobilization; Hematopoietic Stem Cell Transplantation; Hematopoietic Stem Cells; Heterocyclic Compounds; Humans; Immunoenzyme Techniques; Lysophospholipids; Male; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, Inbred DBA; Mice, Knockout; Mice, SCID; Mice, Transgenic; Middle Aged; Oligopeptides; Phosphotransferases (Alcohol Group Acceptor); Prognosis; Real-Time Polymerase Chain Reaction; Receptors, CXCR4; Receptors, Lysosphingolipid; RNA, Messenger; Sphingosine; Sphingosine-1-Phosphate Receptors

CXCR7 is an atypical chemokine receptor that signals through β-arrestin in response to agonists without detectable activation of heterotrimeric G-proteins. Its cognate chemokine ligand CXCL12 also binds CXCR4, a chemokine receptor of considerable clinical interest. Here we report that TC14012, a peptidomimetic inverse agonist of CXCR4, is an agonist on CXCR7. The potency of β-arrestin recruitment to CXCR7 by TC14012 is much higher than that of the previously reported CXCR4 antagonist AMD3100 and differs only by one log from that of the natural ligand CXCL12 (EC(50) 350 nM for TC14012, as compared with 30 nM for CXCL12 and 140 μM for AMD3100). Moreover, like CXCL12, TC14012 leads to Erk 1/2 activation in U373 glioma cells that express only CXCR7, but not CXCR4. Given that with TC14012 and AMD3100 two structurally unrelated CXCR4 antagonists turn out to be agonists on CXCR7, this likely reflects differences in the activation mechanism of the arrestin pathway by both receptors. To identify the receptor domain responsible for these opposed effects, we investigated CXCR4 and CXCR7 C terminus-swapping chimeras. Using quantitative bioluminescence resonance energy transfer, we find that the CXCR7 receptor core formed by the seven-transmembrane domains and the connecting loops determines the agonistic activity of both TC14012 and AMD3100. Moreover, we find that the CXCR7 chimera bearing the CXCR4 C-terminal constitutively associates with arrestin in the absence of ligands. Our data suggest that the CXCR4 and CXCR7 cores share ligand-binding surfaces for the binding of the synthetic ligands, indicating that CXCR4 inhibitors should be tested also on CXCR7.

Topics: Anti-HIV Agents; Arrestins; Benzylamines; beta-Arrestins; Cell Line, Tumor; Chemokine CXCL12; Cyclams; Dose-Response Relationship, Drug; Enzyme Activation; HEK293 Cells; Heterocyclic Compounds; Humans; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Oligopeptides; Peptidomimetics; Protein Structure, Tertiary; Receptors, CXCR; Receptors, CXCR4; Recombinant Fusion Proteins

The mechanisms regulating the migration of leukaemic cells between the blood and bone marrow compartments remain obscure, but are of fundamental importance for the dissemination of the disease. This study investigated the in vivo homing of human B cell progenitor acute lymphoblastic leukaemia (ALL) cells to the femoral bone marrow of non-obese diabetic severe combined immunodeficient (NOD/SCID) mice. It was demonstrated that patient ALL cells use the chemokine axis, chemokine (CXC motif) receptor 4 (CXCR4)/ chemokine (CXC motif) ligand 12 (CXCL12), to home to the femoral marrow. CXCL12-mediated signalling through p38 mitogen-activated protein kinase (MAPK) was required for optimal homing. In contrast, the homing of normal peripheral blood CD34(+) cells and the cytokine-dependent CD34(+) cell line Mo7e was independent of p38MAPK, consistent with the dependence of these cells, as well as normal CD34(+) CD19(+) B cell progenitors, on PI-3K/AKT signalling. Altogether, our data provide clarification of the direct role of CXCL12 in the bone marrow homing of ALL cells and demonstrate unique signalling molecule usage that may have therapeutic implications for this disease.

Topics: Animals; B-Lymphocytes; Benzylamines; Bone Marrow; Cell Line, Tumor; Chemokine CXCL12; Chemotaxis, Leukocyte; Chromones; Cyclams; Enzyme Activation; Enzyme Inhibitors; Flavonoids; Heterocyclic Compounds; Humans; Imidazoles; Mice; Mice, Inbred NOD; Mice, SCID; Morpholines; Neoplastic Stem Cells; Oligopeptides; p38 Mitogen-Activated Protein Kinases; Phosphoinositide-3 Kinase Inhibitors; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Protein Binding; Receptors, CXCR4