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Journal of Virology, June 2001, p. 5457-5464, Vol. 75, No. 12
INSERM U.332, Institut Cochin de
Génétique Moléculaire, 75014 Paris, France
Received 4 January 2001/Accepted 21 March 2001
Human immunodeficiency virus type 1 (HIV-1) entry is triggered by
the interaction of the gp120 envelope glycoprotein with a cellular
chemokine receptor, either CCR5 or CXCR4. We have identified different
mutations in human CXCR4 that prevent efficient infection by one HIV-1
strain (NDK) but not another (LAI) and sought to define these
strain-dependent effects at the gp120 level. The lack of activity
toward the NDK strain of the HHRH chimeric CXCR4 in which the second
extracellular loop (ECL2) derived from the rat CXCR4 and of CXCR4 with
mutations at an aspartic acid in ECL2 (D193A and D193R) was apparently
due to the sequence of the third variable loop (V3) of gp120, more
precisely, to its C-terminal part. Indeed, substitution of the LAI V3
loop or only its C-terminal part in the NDK gp 120 context was
sufficient to restore usage of the HHRH, D193A, and D193R receptors.
The same result was achieved upon mutation of a single lysine residue
of the NDK V3 loop to alanine (K319A) but not to arginine (K319R).
These results provide a strong case for a direct interaction between
the gp120 V3 loop and the ECL2 domain of CXCR4. By contrast, V3
substitutions had no effect on the inability of NDK to infect cells via
a mutant CXCR4 in which the amino-terminal extracellular domain (NT) is deleted. In experiments with a set of chimeric NDK-LAI gp120s, the
V1/V2 region from LAI gp120 was both necessary and sufficient for usage
of the NT-deleted CXCR4. Different variable domains of gp120 can
therefore cooperate for a functional interaction with CXCR4.
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.12.5457-5464.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Cooperation of the V1/V2 and V3 Domains of Human
Immunodeficiency Virus Type 1 gp120 for Interaction with the
CXCR4 Receptor
*
Corresponding author. Mailing address: INSERM U.332,
Institut Cochin de Génétique Moléculaire, 22 rue
Méchain, 75014 Paris, France. Phone: 33-1-40 51 64 86. Fax:
33-1-40 51 64 54. E-mail: alizon{at}cochin.inserm.fr.
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