Chandrasekhar S, Popov S, Gratton S, Sekaly RP, Venkatesan S; National Conference on Human Retroviruses and Related Infections.

Program Abstr Second Natl Conf Hum Retrovir Relat Infect Natl Conf Hum Retrovir Relat Infect 2nd 1995 Wash DC. 1995 Jan 29-Feb 2; 61.

Laboratory of Molecular Microbiology, NIADI, NIH, Bethesda, MD.

Nef expression from a vaccinia vector reduced the surface expression of pre-synthesized CD4 by enhancing the receptor internalization in both the CD4+ T cell and HeLa cell lines. Nef induced endosomal sequestration and degradation of internalized CD4. This effect of Nef on CD4 was reversible to varying degrees by agents that disrupt receptor endocytosis and/or inhibit lysosomal proteolysis. The loss of cell-surface CD4 required the cytoplasmic tail of CD4, but not the PKC phosphorylation or lck p56 interaction motifs. Nef failed to induce endocytosis of a CD4 mutant that substituted the di-leucine motif in the cytoplasmic domain. But, Nef did not accentuate the accelerated turn- over of natural or chimeric receptor(s) containing a generic di-leucine motif in the cytoplasmic domain. These findings suggest that the Nef effect may require physical interaction with CD4 or Nef may mediate unidentified phosphorylation events on the CD4 receptor that results in endocytosis. We have failed to demonstrate a consistent, and stoichiometrically meaningful physical association of Nef with CD4 and/or lck p56. However, a distinct 80 kDal ATP dependent protein kinase was coprecipitated with Nef and unique cellular cDNA expression plasmids reacting with Nef were tentatively identified in a yeast 2-hybrid system of genetic selection. When Nef and CD4 were co-expressed by simultaneous infection of T cells with the respective vaccinia recombinants, there was a quantitative defect in the biosynthetic rates of CD4 that was followed by enhanced turnover of the nascent receptor at the cell surface. The Nef effect on the CD4 receptor turn-over at the cell surface was moderated in T cell lines that express endogenous CD4. With CD4 mutants lacking the cytoplasmic tail, only the biosynthetic defect but not the receptor turnover was demonstrated. Nef also induced a biosynthetic defect of the secretory form of CD4.

Publication Types:

• Meeting Abstracts

Keywords:

• Animals
• Antigens, CD4
• CD4-Positive T-Lymphocytes
• Cell Line
• Endocytosis
• HIV-1
• Hela Cells
• Humans
• Leucine
• Lymphocyte Specific Protein Tyrosine Kinase p56(lck)
• Lysosomes
• Protein Binding
• T-Lymphocytes
• immunology

Other ID:

• 95920069

UI: 102213014

From Meeting Abstracts