Document 3330
 DOCN  M94A3330
 TI    Gp120 induces CD4-association with membrane component(s) and
       susceptibility to PMA-induced co-modulation.
 DT    9412
 AU    Golding H; Lapham C; CBER, FDA, Bethesda, MD 20892.
 SO    Int Conf AIDS. 1994 Aug 7-12;10(1):100 (abstract no. PA0017). Unique
       Identifier : AIDSLINE ICA10/94369245
 AB    OBJECTIVE: To identify additional membrane components required for HIV-1
       entry and envelope mediated fusion (CD4-co-receptor). METHODS: Using
       cell lines expressing either tailless CD4 molecules (CD4.401) or
       chimeric CD4.CD8 molecules, we found that PMA does not induce
       down-modulation of these receptors. Yet PMA treatment dramatically
       inhibited HIV-1 env-mediated fusion and infection, due to
       down-modulation of a co-receptor expressed by the CD4-bearing cells (H.
       Golding et al J. Virol. 1994). In the current study, soluble gp120 was
       added to these cell lines at different temperatures followed by 3 hr PMA
       treatment. Surface expression of the CD4.401 and CD4.CD8 molecules was
       determines by FACS analysis. RESULTS: Incubation of CD4.401-expressing
       cells with monomeric soluble gp120 for 1-2 hr at 37 degrees C, resulted
       in small (25-35%) down-modulation of the CD4 receptors. However,
       subsequent treatment with PMA for 3 hr at 37 degrees C, resulted in
       marked (50-70%) down-modulation of the CD4 molecules. The ability of
       gp120 to prime cells for CD4-down-modulation was temperature dependent
       since it was not seen after incubation at 4 degrees C under maximal
       binding conditions. Furthermore, gp120 incubation in the presence of
       hypertonic buffer which blocks formation of clathrine coated pits
       blocked the subsequent PMA-induced down-modulation. Interestingly, gp120
       treatment of the CD4.CD8-expressing cells (which contain two membrane
       proximal domains and cytoplasmic tail from CD8), did not result in
       significant down-modulation by subsequent PMA treatment. DISCUSSION: Our
       data suggest that incubation of cells with gp120 induces conformational
       changes in the CD4 receptors resulting in their association with other
       surface component(s). These complexes are susceptible to
       co-down-modulation via clathrine-coated pits. The membrane proximal
       domains of CD4 may be involved in this association.
 DE    Antigens, CD4/DRUG EFFECTS/GENETICS/*PHYSIOLOGY  Antigens,
       CD8/GENETICS/PHYSIOLOGY  Cell Fusion/PHYSIOLOGY  Cell Line  Cell
       Membrane/DRUG EFFECTS/MICROBIOLOGY/PHYSIOLOGY  Coated Pits,
       Cell-Membrane/DRUG EFFECTS/MICROBIOLOGY/PHYSIOLOGY  Down-Regulation
       (Physiology)  Human  HIV Envelope Protein gp120/*PHYSIOLOGY  HIV-1/DRUG
       EFFECTS/*PHYSIOLOGY/PATHOGENICITY  Recombinant Proteins/GENETICS
       Tetradecanoylphorbol Acetate/PHARMACOLOGY  MEETING ABSTRACT

       SOURCE: National Library of Medicine.  NOTICE: This material may be
       protected by Copyright Law (Title 17, U.S.Code).