Differential regulation of G-protein-mediated signaling by chemokine receptors.
Monocyte chemoattractant protein-1 (MCP-1) is a member of a family of chemotactic cytokines that induce directed migration of leukocytes via activation of seven-transmembrane domain receptors. To identify G-proteins that couple to the two forms of the MCP-1 receptor, as well as to related chemokine receptors, we have performed cotransfection experiments in mammalian cells. In COS-7 cells, the type A and type B MCP-1 receptors coupled to Galphai, Galphaq, and Galpha16, whereas the macrophage inflammatory protein-1alpha/RANTES (regulated on activation, normal T cell-expressed and secreted) receptor (C-CR1) coupled to Galphai and Galphaq but failed to couple to Galpha16. In HEK-293 cells, however, the MCP-1 receptors and C-CR1 coupled to Galphaq but failed to couple to Galpha16. In contrast, the interleukin-8 and C5a receptors did not couple to Galphaq in either COS-7 or HEK-293 cells but did couple to Galpha16. Exchange of intracellular loops between the MCP-1 and interleukin-8 receptors to create chimeric receptors revealed that the third loop of the MCP-1 receptor accounted for virtually all of the coupling to Galphaq. We conclude that the MCP-1 and related chemokine receptors couple to multiple G-proteins, that coupling is cell type-specific, and that the third intracellular loop of the C-C type receptors mediates Galphaq coupling.
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Gladstone Institute of Cardiovascular Disease, University of California, San Francisco, California 94141-9100, USA.
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D000595:Amino Acid Sequence; D015703:Antigens, CD / Q000378:metabolism; D002460:Cell Line; D018932:Chemokine CCL2 / Q000378:metabolism*; D018946:Chemokine CCL5 / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D006868:Hydrolysis; D007295:Inositol Phosphates / Q000378:metabolism; D008969:Molecular Sequence Data; D010716:Phosphatidylinositols / Q000378:metabolism; D017433:Protein Structure, Secondary; D044087:Receptor, Anaphylatoxin C5a; D054390:Receptors, CCR2; D019707:Receptors, Chemokine; D011951:Receptors, Complement / Q000378:metabolism; D018121:Receptors, Cytokine / Q000378:metabolism*; D018123:Receptors, Interleukin / Q000378:metabolism; D023062:Receptors, Interleukin-8A; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D010566:Virulence Factors, Bordetella / Q000494:pharmacology; D051552:beta-Adrenergic Receptor Kinases
D015703:Antigens, CD; C515334:CCR2 protein, human; D018932:Chemokine CCL2; D018946:Chemokine CCL5; D007295:Inositol Phosphates; D010716:Phosphatidylinositols; D044087:Receptor, Anaphylatoxin C5a; D054390:Receptors, CCR2; D019707:Receptors, Chemokine; D011951:Receptors, Complement; D018121:Receptors, Cytokine; D018123:Receptors, Interleukin; D023062:Receptors, Interleukin-8A; D010566:Virulence Factors, Bordetella; D017868:Cyclic AMP-Dependent Protein Kinases; D051552:beta-Adrenergic Receptor Kinases; D019204:GTP-Binding Proteins