Receptor reserve analysis of the human CCR3 receptor in eosinophils and CCR3-transfected cells.
A novel pharmacological study of CCR3 receptor reserve in a CCR3-transfected cell (CREM3) and human eosinophils was done; functional responses measured were increases in intracellular calcium and chemotaxis. Eotaxin, eotaxin-2, monocyte chemoattractant protein-4 (MCP-4), RANTES, and MCP-3 induced similar maximal eosinophil chemotaxis, whereas MCP-3 and RANTES induced submaximal calcium responses in eosinophils compared to eotaxin, MCP-4, and eotaxin-2. This suggested a receptor reserve in the chemotaxis response. Receptor reserve was quantitated for eotaxin. Occupancy of all CCR3 receptors was required for a maximal calcium response in both CREM3 and eosinophils (reserve = 1.0 or 0.17, respectively); the stimulus-calcium response relationship was linear, indicating no receptor reserve. In contrast, in eosinophils a large receptor reserve (6.5) was found for chemotaxis, where occupancy of 15% receptors drove half-maximal responses. These studies indicate that CCR3 interacts with G-proteins that are poorly coupled to the calcium response, whereas coupling efficiency and/or amplification to the chemotaxis apparatus in human eosinophils is significantly greater.
Umland
S P
SP
Department of Allergy, Schering-Plough Research Institute, Kenilworth, New Jersey 07033, USA. shelby.umland@spcorp.com
Wan
Y
Y
Shortall
J
J
Shah
H
H
Jakway
J
J
Garlisi
C G
CG
Tian
F
F
Egan
R W
RW
Billah
M M
MM
D000818:Animals; D001667:Binding, Competitive; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D002460:Cell Line; D002478:Cells, Cultured; D054413:Chemokine CCL11; D018946:Chemokine CCL5 / Q000378:metabolism / Q000494:pharmacology; D019742:Chemokines, CC; D002631:Chemotactic Factors, Eosinophil / Q000378:metabolism / Q000494:pharmacology; D002634:Chemotaxis, Leukocyte / Q000187:drug effects; D016207:Cytokines / Q000378:metabolism / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004804:Eosinophils / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D008024:Ligands; D018945:Monocyte Chemoattractant Proteins / Q000378:metabolism / Q000494:pharmacology; D051381:Rats; D054397:Receptors, CCR3; D019707:Receptors, Chemokine / Q000819:agonists* / Q000235:genetics / Q000378:metabolism*; D013816:Thermodynamics; D014162:Transfection
C515456:CCL11 protein, human; C515350:CCR3 protein, human; C515458:Ccl11 protein, rat; C515352:Ccr3 protein, rat; D054413:Chemokine CCL11; D018946:Chemokine CCL5; D019742:Chemokines, CC; D002631:Chemotactic Factors, Eosinophil; D016207:Cytokines; D008024:Ligands; D018945:Monocyte Chemoattractant Proteins; D054397:Receptors, CCR3; D019707:Receptors, Chemokine; D002118:Calcium