A role for the SNARE protein syntaxin 3 in human cytomegalovirus morphogenesis

Area of Science:

• Virology
• Cell Biology
• Molecular Biology

Background:

• Human cytomegalovirus (HCMV) is an enveloped virus requiring cellular membrane systems for replication.
• HCMV envelopment occurs within intracellular membranes, a process with poorly understood mechanisms.

Purpose of the Study:

• To investigate the role of syntaxin 3 (STX3), a SNARE protein, in HCMV replication and morphogenesis.
• To elucidate the cellular machinery involved in HCMV final envelopment.

Main Methods:

• Studied HCMV-infected cells, observing STX3 expression and localization via immunogold labeling.
• Utilized RNA interference (RNAi) to deplete STX3 and assessed its impact on HCMV production.
• Performed ultrastructural examination of viral assembly sites in STX3-depleted cells.
• Examined the effect of STX3 silencing on herpes simplex virus type 1 (HSV-1) production.
• Assessed the expression of lysosomal membrane glycoproteins following STX3 depletion.

Main Results:

• HCMV infection induced STX3 expression, with STX3 localized at the plasma membrane and viral assembly sites.
• STX3 depletion reduced HCMV production, while STX3 overexpression enhanced it.
• Ultrastructural analysis revealed fewer mature virions and more viruses undergoing envelopment in STX3-depleted cells.
• STX3 silencing did not affect HSV-1 production, indicating specificity.
• STX3 depletion led to reduced expression of lysosomal membrane glycoproteins, suggesting involvement of late endosomes/lysosomes.

Conclusions:

• Syntaxin 3 (STX3) plays a significant role in human cytomegalovirus (HCMV) morphogenesis.
• STX3 is involved in the late endosomes/lysosomes compartments, contributing to HCMV assembly and maturation.
• The findings reveal a novel function for STX3 in the viral life cycle of HCMV.