Theta-defensins prevent HIV-1 Env-mediated fusion by binding gp41 and blocking 6-helix bundle formation.
Retrocyclin-1, a -defensin, protects target cells from human immunodeficiency virus, type 1 (HIV-1) by preventing viral entry. To delineate its mechanism, we conducted fusion assays between susceptible target cells and effector cells that expressed HIV-1 Env. Retrocyclin-1 (4 microm) completely blocked fusion mediated by HIV-1 Envs that used CXCR4 or CCR5 but had little effect on cell fusion mediated by HIV-2 and simian immunodeficiency virus Envs. Retrocyclin-1 inhibited HIV-1 Env-mediated fusion without impairing the lateral mobility of CD4, and it inhibited the fusion of CD4-deficient cells with cells bearing CD4-independent HIV-1 Env. Thus, it could act without cross-linking membrane proteins or inhibiting gp120-CD4 interactions. Retrocyclin-1 acted late in the HIV-1 Env fusion cascade but prior to 6-helix bundle formation. Surface plasmon resonance experiments revealed that retrocyclin bound the ectodomain of gp41 with high affinity in a glycan-independent manner and that it bound selectively to the gp41 C-terminal heptad repeat. Native-PAGE, enzyme-linked immunosorbent assay, and CD spectroscopic analyses all revealed that retrocyclin-1 prevented 6-helix bundle formation. This mode of action, although novel for an innate effector molecule, resembles the mechanism of peptidic entry inhibitors based on portions of the gp41 sequence.
Gallo
Stephen A
SA
Center for Cancer Research Nanobiology Program, NCI-Frederick, National Institutes of Health, Frederick, Maryland 21702, USA.
Wang
Wei
W
Rawat
Satinder S
SS
Jung
Grace
G
Waring
Alan J
AJ
Cole
Alexander M
AM
Lu
Hong
H
Yan
Xuxia
X
Daly
Norelle L
NL
Craik
David J
DJ
Jiang
Shibo
S
Lehrer
Robert I
RI
Blumenthal
Robert
R
D001665:Binding Sites; D023082:Defensins / Q000378:metabolism / Q000494:pharmacology*; D015700:HIV Envelope Protein gp41 / Q000378:metabolism; D023581:HIV Fusion Inhibitors / Q000378:metabolism / Q000494:pharmacology*; D015658:HIV Infections / Q000188:drug therapy / Q000821:virology; D015497:HIV-1 / Q000187:drug effects* / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D011485:Protein Binding; D011487:Protein Conformation; D014779:Virus Replication / Q000187:drug effects* / Q000235:genetics
D023082:Defensins; D015700:HIV Envelope Protein gp41; D023581:HIV Fusion Inhibitors; C450142:theta-defensin