Identification of V3 loop-binding proteins as potential receptors implicated in the binding of HIV particles to CD4(+) cells.
The binding of human immunodeficiency virus (HIV) type 1 particles to CD4(+) cells could be blocked either by antibodies against the V3 loop domain of the viral external envelope glycoprotein gp120, or by the V3 loop mimicking pseudopeptide 5[Kpsi(CH2N)PR]-TASP, which forms a stable complex with a cell-surface-expressed 95-kDa protein. Here, by using an affinity matrix containing 5[Kpsi(CH2N)PR]-TASP and cytoplasmic extracts from human CEM cells, we purified three V3 loop-binding proteins of 95, 40, and 30 kDa, which after microsequencing were revealed to be as nucleolin, putative HLA class II-associated protein (PHAP) II, and PHAP I, respectively. The 95-kDa cell-surface protein was also isolated and found to be nucleolin. We show that recombinant preparations of gp120 bind the purified preparations containing the V3 loop-binding proteins with a high affinity, comparable to the binding of gp120 to soluble CD4. Such binding is inhibited either by 5[Kpsi(CH2N)PR]-TASP or antibodies against the V3 loop. Moreover, these purified preparations inhibit HIV entry into CD4(+) cells as efficiently as soluble CD4. Taken together, our results suggest that nucleolin, PHAP II, and PHAP I appear to be functional as potential receptors in the HIV binding process by virtue of their capacity to interact with the V3 loop of gp120.
Unité de Virologie et Immunologie Cellulaire, ERS 572 CNRS, Institut Pasteur, 28 rue du Dr Roux, 75724 Paris Cedex 15, France.
C
C
Callebaut
J
J
Blanco
N
N
Benkirane
B
B
Krust
E
E
Jacotot
G
G
Guichard
N
N
Seddiki
J
J
Svab
E
E
Dam
S
S
Muller
J P
JP
Briand
A G
AG
Hovanessian
D000595:Amino Acid Sequence; D015704:CD4 Antigens / Q000378:metabolism; D015496:CD4-Positive T-Lymphocytes / Q000821:virology*; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D015699:HIV Envelope Protein gp120 / Q000378:metabolism*; D015497:HIV-1 / Q000378:metabolism*; D056488:Histone Chaperones; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009687:Nuclear Proteins; D010446:Peptide Fragments / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism; D015728:Receptors, HIV / Q000378:metabolism*; D014157:Transcription Factors; D014771:Virion / Q000378:metabolism*; D000097796:Nucleolin
D015704:CD4 Antigens; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D015699:HIV Envelope Protein gp120; D056488:Histone Chaperones; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; D010446:Peptide Fragments; D010750:Phosphoproteins; D011506:Proteins; D016601:RNA-Binding Proteins; D015728:Receptors, HIV; D014157:Transcription Factors; D000097796:Nucleolin; C087425:ANP32A protein, human; C059762:HIV envelope protein gp120 (305-321); C513473:SET protein, human