N-linked glycosylation in the CXCR4 N-terminus inhibits binding to HIV-1 envelope glycoproteins.
CXCR4 is a co-receptor along with CD4 for human immunodeficiency virus type 1 (HIV-1). We investigated the role of N-linked glycosylation in the N-terminus of CXCR4 in binding to HIV-1 gp120 envelope glycoproteins. Gp120s from CXCR4 (X4) and CCR5 (R5) using HIV-1 strains bound more efficiently to non-N-glycosylated than to N-glycosylated CXCR4 proteoliposomes in a CD4-dependent manner. Similar results were observed in binding studies using non-N-glycosylated or N-glycosylated CXCR4 expressed on cells. Mutation of the N-glycosylation site N11 in CXCR4 (N11Q-CXCR4) enhanced CD4-dependent binding of X4 and R5 gp120s and allowed more efficient entry of viruses pseudotyped with X4 or R5 HIV-1 envelope glycoproteins. However, the binding of R5 gp120 to N11Q-CXCR4 and entry of R5 HIV-1 viruses into cells expressing N11Q-CXCR4 were 20- and 100- to 1000-fold less efficient, respectively, than the levels achieved using X4 gp120 or X4 HIV-1 viruses. Binding of stromal cell-derived factor (SDF)-1alpha, the natural ligand of CXCR4, and SDF-1alpha-induced signaling were reduced by the N11Q mutation. These findings demonstrate that N-glycosylation at N11 inhibits the binding of CXCR4 to X4 and R5 HIV-1 gp120, and provide a better understanding of the structural elements of CXCR4 involved in HIV-1 Env-co-receptor interactions.
Wang
Jianbin
J
Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Boston, MA 02115, USA.
Babcock
Gregory J
GJ
Choe
Hyeryun
H
Farzan
Michael
M
Sodroski
Joseph
J
Gabuzda
Dana
D
D001216:Asparagine / Q000378:metabolism; D002460:Cell Line; D054377:Chemokine CXCL12; D019743:Chemokines, CXC / Q000378:metabolism; D006031:Glycosylation; D015699:HIV Envelope Protein gp120 / Q000378:metabolism*; D015497:HIV-1 / Q000502:physiology*; D006801:Humans; D011510:Proteolipids / Q000502:physiology; D019713:Receptors, CCR5 / Q000378:metabolism; D019718:Receptors, CXCR4 / Q000737:chemistry / Q000378:metabolism*; D013329:Structure-Activity Relationship; D014415:Tunicamycin / Q000494:pharmacology
C515255:CXCL12 protein, human; D054377:Chemokine CXCL12; D019743:Chemokines, CXC; D015699:HIV Envelope Protein gp120; D011510:Proteolipids; D019713:Receptors, CCR5; D019718:Receptors, CXCR4; C020485:proteoliposomes; D014415:Tunicamycin; D001216:Asparagine