Five-transmembrane domains appear sufficient for a G protein-coupled receptor: functional five-transmembrane domain chemokine receptors.
The putative seven-transmembrane (TM) domains have been the structural hallmark for the superfamily of heterotrimeric G protein-coupled receptors (GPCRs) that regulate a variety of cellular functions by mediating a large number of extracellular signals. Five-TM GPCR mutants of chemokine receptor CCR5 and CXCR4, the N-terminal segment of which connected directly to TM3 as a result of a deletion of TM1-2 and the first intracellular and extracellular loops, have been obtained in this study. Laser confocal microscopy and flow cytometry analysis revealed that these five-TM mutant GPCRs were expressed stably on the cell surface after transfection into human embryonic kidney 293 cells. The five-TM CCR5 and CXCR4 functioned as normal chemokine receptors in mediating chemokine-stimulated chemotaxis, Ca2+ influx, and activation of pertussis toxin-sensitive G proteins. Like the wild-type GPCRs, the five-TM mutant receptors also underwent agonist-dependent internalization and desensitization and were subjected to regulation by GPCR kinases and arrestins. Our study indicates that five-TM domains, at least in the case of CCR5 and CXCR4, appear to meet the minimum structural requirements for a functional GPCR and suggests possible existence of functional five-TM GPCRs in nature during evolution.
Shanghai Institute of Cell Biology, Chinese Academy of Sciences, Shanghai, 200031, People's Republic of China.
K
K
Ling
P
P
Wang
J
J
Zhao
Y L
YL
Wu
Z J
ZJ
Cheng
G X
GX
Wu
W
W
Hu
L
L
Ma
G
G
Pei
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000595:Amino Acid Sequence; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000502:physiology; D018946:Chemokine CCL5 / Q000737:chemistry / Q000502:physiology; D002633:Chemotaxis; D003001:Cloning, Molecular; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D019143:Evolution, Molecular; D019204:GTP-Binding Proteins / Q000502:physiology*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006801:Humans; D007668:Kidney; D008958:Models, Molecular; D008969:Molecular Sequence Data; D037342:Pertussis Toxin; D017433:Protein Structure, Secondary; D019713:Receptors, CCR5 / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D019718:Receptors, CXCR4 / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D014162:Transfection; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D018946:Chemokine CCL5; D019713:Receptors, CCR5; D019718:Receptors, CXCR4; D011994:Recombinant Proteins; D010566:Virulence Factors, Bordetella; D005576:Colforsin; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D000242:Cyclic AMP; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D002118:Calcium; D015056:1-Methyl-3-isobutylxanthine