The Host Protein CAD Regulates the Replication of FMDV through the Function of Pyrimidines' De Novo Synthesis

by Selleckchem | Aug 17 2023

Foot-and-mouth disease virus (FMDV) is a single-stranded picornavirus that causes economically devastating disease in even-hooved animals. There has been little research on the function of host cells during FMDV infection. We aimed to shed light on key host factors associated with FMDV replication during acute infection. We found that HDAC1 overexpression in host cells induced upregulation of FMDV RNA and protein levels. Activation of the AKT-mammalian target of rapamycin (mTOR) signaling pathway using bpV(HOpic) or SC79 also promoted FMDV replication. Furthermore, short hairpin RNA (shRNA)-induced suppression of carbamoyl-phosphate synthetase 2, aspartate transcarbamylase, and dihydroorotase (CAD), a transcription factor downstream of the AKT-mTOR signaling pathway, resulted in downregulation of FMDV RNA and protein levels. Coimmunoprecipitation assays showed that the ACTase domain of CAD could interact with the FMDV 2C protein, suggesting that the ACTase domain of CAD may be critical in FMDV replication. CAD proteins participate in de novo pyrimidine synthesis. Inhibition of FMDV replication by deletion of the ACTase domain of CAD in host cells could be reversed by supplementation with uracil. These results revealed that the contribution of the CAD ACTase domain to FMDV replication is dependent on de novo pyrimidine synthesis. Our research shows that HDAC1 promotes FMDV replication by regulating de novo pyrimidine synthesis from CAD via the AKT-mTOR signaling pathway.

IMPORTANCE Foot-and-mouth disease virus is an animal virus of the Picornaviridae family that seriously harms the development of animal husbandry and foreign trade of related products, and there is still a lack of effective means to control its harm. Replication complexes would generate during FMDV replication to ensure efficient replication cycles. 2C is a common viral protein in the replication complex of Picornaviridae virus, which is thought to be an essential component of membrane rearrangement and viral replication complex formation. The host protein CAD is a key protein in the pyrimidines de novo synthesis. In our research, the interaction of CAD and FMDV 2C was demonstrated in FMDV-infected BHK-21 cells, and it colocalized with 2C in the replication complex. The inhibition of the expression of FMDV 3D protein through interference with CAD and supplementation with exogenous pyrimidines reversed this inhibition, suggesting that FMDV might recruit CAD through the 2C protein to ensure pyrimidine supply during replication. In addition, we also found that FMDV infection decreased the expression of the host protein HDAC1 and ultimately inhibited CAD activity through the AKT-mTOR signaling pathway. These results revealed a unique means of counteracting the virus in BHK-21 cells lacking the interferon (IFN) signaling pathway. In conclusion, our study provides some potential targets for the development of drugs against FMDV.

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The provided information describes a research study conducted to investigate the host factors associated with Foot-and-mouth disease virus (FMDV) replication during acute infection. Here are the key findings and implications of the study:

1. HDAC1 Overexpression and FMDV Replication: The researchers found that overexpression of HDAC1, a host protein called histone deacetylase 1, in host cells led to an increase in FMDV RNA and protein levels. This suggests that HDAC1 promotes FMDV replication.

2. AKT-mTOR Signaling Pathway and FMDV Replication: Activation of the AKT-mTOR signaling pathway, achieved using substances called bpV(HOpic) or SC79, also promoted FMDV replication. This pathway plays a role in cell growth and metabolism and appears to contribute to FMDV replication.

3. CAD and FMDV Replication: The researchers observed that the host protein CAD (carbamoyl-phosphate synthetase 2, aspartate transcarbamylase, and dihydroorotase) is involved in FMDV replication. CAD is a key protein in the de novo synthesis of pyrimidines, which are essential components of nucleic acids. They found that CAD interacts with the FMDV 2C protein and colocalizes with it in the replication complex.

4. Importance of CAD ACTase Domain and Pyrimidine Synthesis: The researchers discovered that the ACTase domain of CAD is critical for FMDV replication. Inhibition of FMDV replication was achieved by suppressing the ACTase domain of CAD in host cells. The inhibition could be reversed by supplementing the cells with uracil, one of the pyrimidine bases. This indicates that the contribution of the CAD ACTase domain to FMDV replication is dependent on de novo pyrimidine synthesis.

5. Role of HDAC1 in CAD Regulation: The study revealed that FMDV infection decreases the expression of HDAC1, which ultimately inhibits CAD activity. This regulation occurs through the AKT-mTOR signaling pathway.

6. Potential Targets for Drug Development: The research findings provide potential targets for the development of drugs against FMDV. Targeting HDAC1 or the AKT-mTOR pathway could potentially disrupt FMDV replication. Additionally, CAD could be explored as a target for inhibiting FMDV replication by interfering with de novo pyrimidine synthesis.

Overall, this study contributes to our understanding of the host factors involved in FMDV replication and highlights potential avenues for the development of antiviral strategies against FMDV.