Contribution of Sorting Nexin 3 in the Cytomegalovirus Assembly

Area of Science:

• Cell Biology
• Virology
• Molecular Biology

Background:

• Cytomegalovirus (CMV) infection induces early endosome (EE) tubulation, potentially aiding viral replication and assembly.
• Sorting nexins (SNXs) and protein coats organize EE membrane domains for tubulation and cargo retrieval, including viral components.

Purpose of the Study:

• To investigate the role of the sorting nexin 3 (SNX3)-dependent EE domain in cytomegalovirus (CMV) replication and assembly.
• To determine the contribution of SNX3 to murine CMV (MCMV) replication, assembly compartment (AC) formation, and virion release.

Main Methods:

• Utilized confocal imaging for protein localization and Western blot for expression analysis.
• Employed siRNA and shRNA to deplete SNX3 and assess its impact on MCMV replication and virion release.
• Investigated the effects of combined knockdowns of SNX1, SNX2, SNX4, SNX17, and SNX27 with SNX3 depletion.

Main Results:

• SNX3 depletion did not affect MCMV replication but impaired virion release.
• The SNX3-dependent EE zone recruited SNX27 and facilitated Rab10-dependent tubulation in the pre-AC.
• SNX3 acts sequentially with SNX27, SNX4, and SNX17 to promote virion release, particularly affecting recycling to the plasma membrane.

Conclusions:

• SNX3 is essential for the formation of the pre-assembly compartment (pre-AC) and efficient MCMV assembly.
• SNX3 plays a sequential role with other SNXs (SNX27, SNX4, SNX17) in the recycling pathway for virion production and release.
• These findings suggest that multiple membrane sources contribute to the secondary envelopment of MCMV virions.