AIDSWEEKLY Plus; Monday, May 21, 2001
Michael Greer, Staff Medical Writer

NewsRx - Researchers in Germany have discovered a pair of motifs in HIV's cytoplasmic tail that suppress surface expression of the Env protein.

"Only a small fraction of [Env glycoprotein] gp160 appears to be ... transported to the cell surface, which makes it difficult to identify negative sequence elements regulating steady-state surface expression of Env at the post-ER [endoplasmic reticulum] level," Jurgen Haas and colleagues explained in the Journal of Virology.

Haas and colleagues devised a method to isolate Env-regulating motifs, which yielded two sequences shown to inhibit surface Env expression, they said.

The researchers used two heterologous systems to find regulatory amino acid sequences. They combined the cytoplasmic domain of gp160 with the extracellular/transmembrane domains of CD4 or immunoglobulin, according to the report.

Using this technique, Haas and coauthors found two adjacent motifs, which they termed is1 and is2. These sequences comprised amino acids 750-763 and 764-785, study data showed.

Further research confirmed that these two motifs act similarly in the homologous Env environment ("Identification of two sequences in the cytoplasmic tail of the human immunodeficiency virus type 1 envelope glycoprotein that inhibit cell surface expression," J Virol 2001 Jun;75(11):5263-76.

"In accordance with the results in heterologous systems, an internal deletion of both elements considerably increased surface expression of gp160," Haas and colleagues concluded.

The corresponding author for this report is Jurgen Haas, Max von Pettenkofer-Institut, Genzentrum, Ludwig Maximilians Universitat Munchen, Munich, Germany.

Key points reported in this study include:

• Researchers have found two motifs in the cytoplasmic tail of Env that suppress its surface expression;
  
  
• Such regulatory sequences are difficult to isolate because much of Env gp160 is not transported to the cell surface;
  
  
• The researchers combined domains from gp160 and CD4 to find the regulatory motifs.
  

This article was prepared by AIDS Weekly editors from staff and other reports.

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