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An additional role for the outer nuclear membrane in the morphogenesis of herpes simplex virus
Abstract:
Ultrastructural study of MRC-5 cells infected by herpes simplex virus yielded several examples of physical continuity between the outer nuclear membrane and the envelope of viral particles in the perinuclear cisterna, suggesting a fusion between the two. Such virions would thus lose their envelope and enter the cytoplasm as naked capsids. Fusion first occurred at 6-8 h postinfection (p.i.), while naked cytoplasmic capsids appeared at 6 h p.i. Since nuclear membrane disruption was not observed until 24 h p.i., it is unlikely to account for the early appearance of these capsids. Thus, in addition to its other roles, the outer nuclear membrane may be involved in naked cytoplasmic capsid production via a fusion event.
Insights
Herpes simplex virus may fuse with the outer nuclear membrane in MRC-5 cells, releasing naked capsids into the cytoplasm. This suggests a novel role for the nuclear membrane in viral replication before cell lysis.
Area of Science:
- Virology
- Cell Biology
- Microbiology
Background:
- Herpes simplex virus (HSV) infection involves complex interactions with host cell machinery.
- The precise mechanisms of HSV capsid transport and envelopment within host cells are not fully understood.
- The role of the nuclear envelope in viral egress and replication requires further elucidation.
Purpose of the Study:
- To investigate the potential involvement of the outer nuclear membrane in herpes simplex virus replication.
- To identify the ultrastructural basis for the early appearance of naked cytoplasmic capsids during HSV infection.
- To explore a novel pathway for viral particle release and cytoplasmic entry.
Main Methods:
- Ultrastructural analysis of MRC-5 cells infected with herpes simplex virus.
- Time-course observation of viral particle formation and localization postinfection (p.i.).
- Microscopy techniques to visualize the nuclear envelope and viral structures.
Main Results:
- Observed physical continuity between the outer nuclear membrane and viral envelopes in the perinuclear cisterna.
- Evidence suggesting fusion between the nuclear membrane and viral envelopes, leading to capsid envelopment.
- Naked cytoplasmic capsids appeared as early as 6 hours postinfection (p.i.).
- Nuclear membrane disruption was observed significantly later, at 24 hours p.i.
Conclusions:
- The outer nuclear membrane may directly participate in the production of naked cytoplasmic capsids through a fusion event.
- This fusion mechanism provides an alternative pathway for viral particles to enter the cytoplasm, preceding nuclear membrane breakdown.
- Suggests a previously unrecognized role for the outer nuclear membrane in herpes simplex virus life cycle and replication.