beta-arrestin differentially regulates the chemokine receptor CXCR4-mediated signaling and receptor internalization, and this implicates multiple interaction sites between beta-arrestin and CXCR4.
The chemokine receptor CXCR4 has recently been shown to be a co-receptor involved in the entry of human immunodeficiency virus type 1 into target cells. This study shows that coexpression of beta-arrestin with CXCR4 in human embryonic kidney 293 cells attenuated chemokine-stimulated G protein activation and inhibition of cAMP production. Truncation of the C-terminal 34 amino acids of CXCR4 (CXCR4-T) abolished the effects of beta-arrestin on CXCR4/G protein signaling, indicating the functional interaction of the receptor C terminus with beta-arrestin. On the other hand, receptor internalization and the subsequent activation of extracellular signal-regulated kinases were significantly promoted by coexpression of beta-arrestin with CXCR4, whereas the C-terminal truncation of CXCR4 did not affect this regulation of beta-arrestin, suggesting that beta-arrestin can functionally interact with CXCR4 with or without the C terminus. Moreover, beta(2)V54D, the dominant inhibitory mutant of beta-arrestin 2, exerted no effects on CXCR4/G protein signaling, but strongly influenced receptor internalization and extracellular signal-regulated kinase activation. Further cross-linking experiments demonstrated that beta-arrestin as well as beta(2)V54D could physically contact both CXCR4 and CXCR4-T. Glutathione S-transferase pull-down assay showed that beta-arrestin was able to bind efficiently in vitro to both the third intracellular loop and the 34-amino acid C terminus of CXCR4. Taken together, our data clearly establish that beta-arrestin can effectively regulate different functions of CXCR4 and that this is mediated through its distinct interactions with the C terminus and other regions including the third loop of CXCR4.
Cheng
Z J
ZJ
Shanghai Institute of Cell Biology, Chinese Academy of Sciences, Shanghai 200031, People's Republic of China.
Zhao
J
J
Sun
Y
Y
Hu
W
W
Wu
Y L
YL
Cen
B
B
Wu
G X
GX
Pei
G
G
D019390:Arrestins / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D002460:Cell Line; D004705:Endocytosis; D006801:Humans; D016296:Mutagenesis; D019718:Receptors, CXCR4 / Q000378:metabolism*; D015398:Signal Transduction; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins
C000605254:ARRB2 protein, human; D019390:Arrestins; D019718:Receptors, CXCR4; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins