Document 0420
 DOCN  M9590420
 TI    Degradation of CD4 induced by human immunodeficiency virus type 1 Vpu
       protein: a predicted alpha-helix structure in the proximal cytoplasmic
       region of CD4 contributes to Vpu sensitivity.
 DT    9509
 AU    Yao XJ; Friborg J; Checroune F; Gratton S; Boisvert F; Sekaly RP; Cohen
       EA; Departement de Microbiologie et Immunologie, Faculte de; Medecine,
       Universite de Montreal, Quebec, Canada.
 SO    Virology. 1995 Jun 1;209(2):615-23. Unique Identifier : AIDSLINE
       MED/95297162
 AB    The HIV-1-encoded Vpu protein induces a rapid and specific degradation
       of CD4 molecules in the endoplasmic reticulum (ER). In this study,
       Vpu-induced degradation of CD4 in the ER was investigated by
       quantitative immunoprecipitation of CD4 following cotransfection of
       COS-7 cells with CD4 and Vpu expressors in the presence of brefeldin A,
       a drug that blocks protein transport from the ER to the Golgi complex.
       In order to precisely define the sequence(s) or structural element(s) in
       the CD4 cytoplasmic domain necessary for Vpu-induced degradation, a
       panel of deletion and substitution mutants in the cytoplasmic domain of
       CD4 was generated and analyzed. In agreement with previous reports, our
       deletion analysis indicates that a region encompassing amino acids 411
       to 419 (KRLLSEKKT) in the cytoplasmic domain of CD4 was required to
       confer Vpu sensitivity. However, six specific substitution mutations
       within this region did not confer CD4 resistance to Vpu, suggesting that
       neither the amino acid sequence nor the charge of the amino acids in
       this region was critical to Vpu-induced CD4 degradation. A dileucine
       motif that is important for internalization of CD4 and Nef-induced CD4
       down-regulation was also not required for Vpu-induced CD4 degradation.
       Interestingly, two substitution mutants (CD4EMKL and CD4MK407,11PP)
       located in a more proximal cytoplasmic region of CD4 abolished
       Vpu-induced CD4 degradation. Computer-assisted analysis of the
       substitution and deletion mutants conferring CD4 resistance to
       Vpu-induced degradation indicated that these mutations disrupted a
       putative alpha-helix formed in the proximal cytoplasmic region of CD4.
       Taken together, these studies strongly suggest that a structural element
       in the proximal cytoplasmic region of CD4 contributes to Vpu
       sensitivity.
 DE    Amino Acid Sequence  Animal  Antigens,
       CD/BIOSYNTHESIS/CHEMISTRY/*METABOLISM  Antigens,
       CD4/BIOSYNTHESIS/CHEMISTRY/*METABOLISM  Base Sequence  Cell Line
       Cercopithecus aethiops  Comparative Study  Cyclopentanes/PHARMACOLOGY
       DNA Primers  Endoplasmic Reticulum/METABOLISM  Gene Products,
       vpu/BIOSYNTHESIS/*IMMUNOLOGY/METABOLISM  Golgi Apparatus/METABOLISM
       Human  HIV-1/*IMMUNOLOGY/METABOLISM  Molecular Sequence Data  Polymerase
       Chain Reaction  Protein Processing, Post-Translational/DRUG EFFECTS
       *Protein Structure, Secondary  Recombinant
       Proteins/BIOSYNTHESIS/CHEMISTRY/METABOLISM  Sequence Deletion  Substrate
       Specificity  Support, Non-U.S. Gov't  Transfection  JOURNAL ARTICLE

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