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Altered expression of Bag-1 in Coxsackievirus B3 infected mouse heart
1Key Laboratory of Viral Heart Disease of Ministry of Public Health, Shanghai Institute of Cardiovascular Disease, Zhongshan Hospital, Shanghai, PR China.
Insights
Coxsackievirus B3 (CVB3) infection down-regulates Bag-1 protein in mouse heart cytoplasm, potentially contributing to viral myocarditis and apoptosis. This study investigates gene expression changes during enterovirus heart muscle disease.
Area of Science:
- Cardiology
- Virology
- Molecular Biology
Background:
- The pathogenesis of Coxsackie B virus (CVB)-induced myocarditis and dilated cardiomyopathy remains unclear.
- Understanding cardiac gene expression changes during viral infection is crucial for elucidating disease mechanisms.
Purpose of the Study:
- To investigate alterations in cardiac gene expression following Coxsackievirus B3 (CVB3) infection in a mouse model.
- To specifically examine the role of the Bag-1 gene and its isoforms in CVB3-induced myocarditis.
Main Methods:
- Mice were experimentally infected with CVB3 or mock-infected.
- Gene expression changes were identified using cDNA arrays and confirmed by semiquantitative RT-PCR, western blot, and immunohistochemistry.
- Cell fractionation and TUNEL assays were employed to analyze Bag-1 protein distribution and apoptosis.
Main Results:
- CVB3 infection altered the expression of 42 cardiac genes.
- Bag-1 expression, particularly the p32 isoform in the cytoplasm, was significantly down-regulated in infected mouse hearts.
- An increase in the nuclear Bag-1 isoform (p50) and evidence of apoptosis were observed in infected hearts.
Conclusions:
- CVB3 infection induces differential expression of Bag-1 in cytoplasmic and nuclear fractions of the mouse heart.
- The observed changes in Bag-1 expression and induction of apoptosis may play a significant role in the pathogenesis of enterovirus-induced heart muscle disease.
Objective:
The mechanisms by which Coxsackie B viruses cause myocarditis or dilated cardiomyopathy are not well understood. This study examined changes in the expression of cardiac genes resulting from Coxsackievirus B3 (CVB3) infection of mice.
Methods:
Mice (five per group) were experimentally infected with CVB3 or mock-infected with diluent. Altered expression of genes was initially identified by cDNA array, and confirmed by semiquantitative RT-PCR, western blot and immunohistochemistry.
Results:
Forty-two up-regulated or down-regulated genes were observed in cDNA arrays carrying 588 known mouse genes. Among these, one down-regulated gene, Bag-1, known to be involved in inhibition of apoptosis and modulation of chaperone activity, was investigated further. Semiquantitative RT-PCR showed that Bag-1 expression was down-regulated by up to 30% in virus-infected mouse heart on day 7 compared to the mock-infected. Cell fractionation and western blot analysis confirmed that Bag-1 isoform p32 was predominant in the cytoplasm of mouse myocardium and down-regulated at 4 days or 7 days after CVB3 infection. In contrast, Bag-1 isoform p50 appeared to increase in the nuclear fraction of mouse heart at 7 days after infection. Down regulated expression and distribution of Bag-1 protein or evidence of apoptosis in the infected mouse heart was demonstrated by immunostaining or histochemistry (TUNEL assay), respectively.
Conclusion:
CVB3 infection induced differential expression of Bag-1 in cytoplasmic and nuclear fractions of mouse heart and apoptosis. This may be important in the pathogenesis of enterovirus heart muscle disease.