Membrane permeabilization by different regions of the human immunodeficiency virus type 1 transmembrane glycoprotein gp41

Abstract

The transmembrane glycoprotein (gp41) of human immunodeficiency virus type 1 (HIV-1) has been implicated in the cytopathology observed during HIV infection. The first amino acids located at the amino terminus are involved in membrane fusion and syncytium formation, while sequences located at the carboxy terminus have been predicted to interact with membranes and modify membrane permeability. The HIV-1 gp41 gene has been cloned and expressed in Escherichia coli cells by using pET vectors to analyze changes in membrane permeability produced by this protein. This system is well suited for expressing toxic genes in an inducible manner and for analyzing the function of proteins that modify membrane permeability. gp41 enhances the permeability of the bacterial membrane to hygromycin B despite the low level of expression of this protein. To localize the regions of gp41 responsible for these effects, a number of fragments spanning different portions of gp41 were inducibly expressed in E. coli. Two regions of gp41 were shown to increase membrane permeability: one located at the carboxy terminus, where two highly amphipathic helices have been predicted, and another one corresponding to the membrane-spanning domain. Expression of the central region of gp41 comprising this domain was highly lytic for E. coli cells and increased membrane permeability to a number of compounds. These findings are discussed in the light of HIV-induced cytopathology and gp41 structure.

The small envelope protein of porcine reproductive and respiratory syndrome virus possesses ion channel protein-like properties

“…Hygromycin B is normally impermeable to the membrane barrier during a short period of time at low concentration, but it can readily penetrate the permeabilized membrane to cause strong inhibition of intracellular protein synthesis. The hygromycin B permeability assay therefore is widely used to study changes of membrane permeability as well as to identify proteins that can form pores in lipid membranes (Aldabe et al, 1996;Arroyo et al, 1995;Bodelón et al, 2002;Chang et al, 1999;Ciccaglione et al, 1998;de Jong et al, 2003;Doedens and Kirkegaard, 1995;Han and Harty, 2004;Liao et al, 2004;Madan et al, 2005). At 1 h induction for E protein expression, hygromycin B was added to the culture media.…”

The C-terminal tail of the gp41 transmembrane envelope glycoprotein of HIV-1 clades A, B, C, and D may exist in two conformations: an analysis of sequence, structure, and function

“…Degradation of the 1-MSD gp41 and recycling of the 3-MSD form would both act to reduce the surface expression of gp120-gp41. This may be important, as high intracellular concentrations of gp41 can be cytotoxic (Arroyo et al, 1995;Chernomordik et al, 1994;Comardelle et al, 1997;Gawrisch et al, 1993;Miller et al, 1993;Zhang et al, 1996), and provoke immune responses against the infected cell. It may be that such post-translational control measures, utilizing tyrosine-dependent sorting signals and the host cell's degradation pathways, have evolved as envelope expression is not easily controlled at a genetic level due to the overlap of the env, tat, and rev ORFs.…”

Viroporins from RNA viruses induce caspase-dependent apoptosis

“…Additionally, a number of viral glycoproteins (e.g. NS3 of bluetongue virus or gp41 of HIV-1) have also been described to possess viroporin-like activity (Arroyo et al, 1995;Han and Harty, 2004).…”