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Updated: May 9, 2026
Vaccinia Reporter Viruses for Quantifying Viral Function at All Stages of Gene Expression
Published on: May 15, 2014
Study of vaccinia and cowpox viruses' replication in Rac1-N17 dominant-negative cells
Ana Paula Carneiro Salgado1, Jamária Adriana Pinheiro Soares-Martins, Luciana Garcia Andrade
1Grupo de Transdução de Sinal/Orthopoxvirus e Flavivírus - LABVÍRUS, Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brasil.
Abstract:
Interfering with cellular signal transduction pathways is a common strategy used by many viruses to create a propitious intracellular environment for an efficient replication. Our group has been studying cellular signalling pathways activated by the orthopoxviruses Vaccinia (VACV) and Cowpox (CPXV) and their significance to viral replication. In the present study our aim was to investigate whether the GTPase Rac1 was an upstream signal that led to the activation of MEK/ERK1/2, JNK1/2 or Akt pathways upon VACV or CPXV' infections. Therefore, we generated stable murine fibroblasts exhibiting negative dominance to Rac1-N17 to evaluate viral growth and the phosphorylation status of ERK1/2, JNK1/2 and Akt. Our results demonstrated that VACV replication, but not CPXV, was affected in dominant-negative (DN) Rac1-N17 cell lines in which viral yield was reduced in about 10-fold. Viral late gene expression, but not early, was also reduced. Furthermore, our data showed that Akt phosphorylation was diminished upon VACV infection in DN Rac1-N17 cells, suggesting that Rac1 participates in the phosphoinositide-3 kinase pathway leading to the activation of Akt. In conclusion, our results indicate that while Rac1 indeed plays a role in VACV biology, perhaps another GTPase may be involved in CPXV replication.
Insights
The GTPase Rac1 is crucial for Vaccinia virus (VACV) replication by activating the Akt pathway, but not for Cowpox virus (CPXV). This discovery offers insights into poxvirus manipulation of host cell signaling for efficient viral propagation.
Area of Science:
- Virology
- Cellular Biology
- Molecular Biology
Background:
- Viruses manipulate host cell signaling pathways to facilitate replication.
- Orthopoxviruses like Vaccinia (VACV) and Cowpox (CPXV) activate cellular signaling cascades.
- The role of GTPase Rac1 in poxvirus infection signaling remains unclear.
Purpose of the Study:
- To investigate if GTPase Rac1 is an upstream activator of MEK/ERK1/2, JNK1/2, or Akt pathways during VACV and CPXV infections.
- To determine the significance of Rac1 in the replication and gene expression of VACV and CPXV.
Main Methods:
- Generation of stable murine fibroblasts expressing dominant-negative Rac1 (Rac1-N17).
- Evaluation of viral yield and phosphorylation status of ERK1/2, JNK1/2, and Akt in infected cells.
- Assessment of viral early and late gene expression.
Main Results:
- VACV replication was significantly reduced (10-fold) in Rac1-N17 cells, impacting late gene expression.
- CPXV replication was not affected by dominant-negative Rac1.
- Akt phosphorylation was diminished in VACV-infected Rac1-N17 cells, indicating Rac1's role in the phosphoinositide-3 kinase/Akt pathway.
Conclusions:
- GTPase Rac1 plays a significant role in VACV replication, likely through the Akt pathway.
- Rac1 does not appear to be essential for CPXV replication, suggesting alternative GTPases may be involved.
- Understanding these viral-host interactions can inform antiviral strategies.
