Previous Article | Next Article ![]()
J. Virol., 10 1996, 6973-6981, Vol 70, No. 10
P Tian, JM Ball, CQ Zeng and MK Estes
During a unique morphogenetic process, rotaviruses obtain a transient
membrane envelope when newly synthesized subviral particles bud into the
endoplasmic reticulum (ER). As rotavirus particles mature, they lose their
transient membrane and a layer of the glycoprotein VP7 forms the virion
outer capsid shell. The nonstructural glycoprotein NSP4 functions as an
intracellular receptor in the ER membrane (K. S. Au, W. K. Chan, J. W.
Burns, and M. K. Estes, J. Virol. 63:4553-4562, 1989), and it has been
hypothesized that NSP4 is involved in the removal of the envelope during
viral morphogenesis (M. K. Estes and J. Cohen, Microbiol. Rev. 53:410-449,
1989; B. L. Petrie, M. K. Estes, and D. Y. Graham, J. Virol. 46:270-274,
1983). The purpose of the present study was to determine if NSP4 has a
direct membrane destabilization activity (MDA) by using liposome leakage
assays and electron microscopic visualization of liposome, microsome, and
viral envelope disruption. The fluorescent marker (calcein) incorporated
into liposomes was released when the liposomes were incubated with purified
NSP4. A region corresponding to amino acid residues 114 to 135 of NSP4 also
released calcein from liposomes. NSP4(114-135) peptide-specific antibody
completely blocked the MDA of the purified NSP4 protein. These results
suggest that this region contains at least part of the functional domain of
NSP4. Liposomes composed of phosphatidylcholine and microsomes (to simulate
ER membranes) were broken when observed by electron microscopy after
incubation with NSP4 or the NSP4(114-135) peptide. In contrast, the
envelope of Sendai virus, which is derived from cytoplasmic membranes, and
erythrocytes were not disrupted by NSP4 and the NSP4(114-135) peptide.
These results provide direct evidence that NSP4 possesses MDA and suggest
that it can cause ER membrane damage. Therefore, NSP4 might play an
important role in the removal of the transient envelope from budding
particles during viral morphogenesis. A model for the MDA of NSP4 in viral
morphogenesis is proposed.
Copyright © 1996, American Society for Microbiology
The rotavirus nonstructural glycoprotein NSP4 possesses membrane destabilization activity
Division of Molecular Virology, Baylor College of Medicine, Houston, Texas 77030, USA.
This article has been cited by other articles:
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»