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MCMV-mediated inhibition of the pro-apoptotic Bak protein is required for optimal in vivo replication.

Fleming P, Kvansakul M, Voigt V, Kile BT, Kluck RM, Huang DC, Degli-Esposti MA, Andoniou CE - PLoS Pathog. (2013)

Bottom Line: Here we show that m41.1 is critical for optimal MCMV replication in vivo.Growth of a m41.1 mutant was attenuated in multiple organs, a defect that was not apparent in Bak(-/-) mice.Thus, m41.1 promotes MCMV replication by inhibiting Bak-dependent apoptosis during in vivo infection.

View Article: PubMed Central - PubMed

Affiliation: Immunology and Virology Program, Centre for Ophthalmology and Visual Science, The University of Western Australia, Nedlands, Western Australia, Australia.

ABSTRACT
Successful replication and transmission of large DNA viruses such as the cytomegaloviruses (CMV) family of viruses depends on the ability to interfere with multiple aspects of the host immune response. Apoptosis functions as a host innate defence mechanism against viral infection, and the capacity to interfere with this process is essential for the replication of many viruses. The Bcl-2 family of proteins are the principle regulators of apoptosis, with two pro-apoptotic members, Bax and Bak, essential for apoptosis to proceed. The m38.5 protein encoded by murine CMV (MCMV) has been identified as Bax-specific inhibitor of apoptosis. Recently, m41.1, a protein product encoded by the m41 open reading frame (ORF) of MCMV, has been shown to inhibit Bak activity in vitro. Here we show that m41.1 is critical for optimal MCMV replication in vivo. Growth of a m41.1 mutant was attenuated in multiple organs, a defect that was not apparent in Bak(-/-) mice. Thus, m41.1 promotes MCMV replication by inhibiting Bak-dependent apoptosis during in vivo infection. The results show that Bax and Bak mediate non-redundant functions during MCMV infection and that the virus produces distinct inhibitors for each protein to counter the activity of these proteins.

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m41.1 encodes a Bak-specific inhibitor.(A) The predicted amino acid sequences of m41 and m41.1 in the K181-Perth MCMV strain are shown. (B) In vitro transcription/translation reactions using cDNA constructs encoding m41 or m41L were performed, the resulting protein products were separated by SDS-PAGE and detected by autoradiography. (C) Fibroblasts derived from WT, Bax- or Bak-deficient mice were infected with retroviruses encoding the indicated proteins. Cells were treated with 10 µM staurosporine for 24 hr and cell viability assessed. (n = 6).
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ppat-1003192-g002: m41.1 encodes a Bak-specific inhibitor.(A) The predicted amino acid sequences of m41 and m41.1 in the K181-Perth MCMV strain are shown. (B) In vitro transcription/translation reactions using cDNA constructs encoding m41 or m41L were performed, the resulting protein products were separated by SDS-PAGE and detected by autoradiography. (C) Fibroblasts derived from WT, Bax- or Bak-deficient mice were infected with retroviruses encoding the indicated proteins. Cells were treated with 10 µM staurosporine for 24 hr and cell viability assessed. (n = 6).

Mentions: The m41.1 protein was recently identified as a Bak-specific inhibitor of apoptosis in the Smith strain of MCMV, and a similar protein was identified in rat CMV [19]. An m41.1 protein is also predicted to be encoded within the 41 ORF of the K181-Perth strain of MCMV used in this study (Fig. 2A). The predicted sequence of the K181 derived m41.1 protein is identical to that of the Smith derived protein, with the exception of the seventh amino acid (Ala in K181 versus Thr in Smith) suggesting that the Bak-inhibitory function mediated by m41.1 is retained in the K181-Perth strain of MCMV.


MCMV-mediated inhibition of the pro-apoptotic Bak protein is required for optimal in vivo replication.

Fleming P, Kvansakul M, Voigt V, Kile BT, Kluck RM, Huang DC, Degli-Esposti MA, Andoniou CE - PLoS Pathog. (2013)

m41.1 encodes a Bak-specific inhibitor.(A) The predicted amino acid sequences of m41 and m41.1 in the K181-Perth MCMV strain are shown. (B) In vitro transcription/translation reactions using cDNA constructs encoding m41 or m41L were performed, the resulting protein products were separated by SDS-PAGE and detected by autoradiography. (C) Fibroblasts derived from WT, Bax- or Bak-deficient mice were infected with retroviruses encoding the indicated proteins. Cells were treated with 10 µM staurosporine for 24 hr and cell viability assessed. (n = 6).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3585157&req=5

ppat-1003192-g002: m41.1 encodes a Bak-specific inhibitor.(A) The predicted amino acid sequences of m41 and m41.1 in the K181-Perth MCMV strain are shown. (B) In vitro transcription/translation reactions using cDNA constructs encoding m41 or m41L were performed, the resulting protein products were separated by SDS-PAGE and detected by autoradiography. (C) Fibroblasts derived from WT, Bax- or Bak-deficient mice were infected with retroviruses encoding the indicated proteins. Cells were treated with 10 µM staurosporine for 24 hr and cell viability assessed. (n = 6).
Mentions: The m41.1 protein was recently identified as a Bak-specific inhibitor of apoptosis in the Smith strain of MCMV, and a similar protein was identified in rat CMV [19]. An m41.1 protein is also predicted to be encoded within the 41 ORF of the K181-Perth strain of MCMV used in this study (Fig. 2A). The predicted sequence of the K181 derived m41.1 protein is identical to that of the Smith derived protein, with the exception of the seventh amino acid (Ala in K181 versus Thr in Smith) suggesting that the Bak-inhibitory function mediated by m41.1 is retained in the K181-Perth strain of MCMV.

Bottom Line: Here we show that m41.1 is critical for optimal MCMV replication in vivo.Growth of a m41.1 mutant was attenuated in multiple organs, a defect that was not apparent in Bak(-/-) mice.Thus, m41.1 promotes MCMV replication by inhibiting Bak-dependent apoptosis during in vivo infection.

View Article: PubMed Central - PubMed

Affiliation: Immunology and Virology Program, Centre for Ophthalmology and Visual Science, The University of Western Australia, Nedlands, Western Australia, Australia.

ABSTRACT
Successful replication and transmission of large DNA viruses such as the cytomegaloviruses (CMV) family of viruses depends on the ability to interfere with multiple aspects of the host immune response. Apoptosis functions as a host innate defence mechanism against viral infection, and the capacity to interfere with this process is essential for the replication of many viruses. The Bcl-2 family of proteins are the principle regulators of apoptosis, with two pro-apoptotic members, Bax and Bak, essential for apoptosis to proceed. The m38.5 protein encoded by murine CMV (MCMV) has been identified as Bax-specific inhibitor of apoptosis. Recently, m41.1, a protein product encoded by the m41 open reading frame (ORF) of MCMV, has been shown to inhibit Bak activity in vitro. Here we show that m41.1 is critical for optimal MCMV replication in vivo. Growth of a m41.1 mutant was attenuated in multiple organs, a defect that was not apparent in Bak(-/-) mice. Thus, m41.1 promotes MCMV replication by inhibiting Bak-dependent apoptosis during in vivo infection. The results show that Bax and Bak mediate non-redundant functions during MCMV infection and that the virus produces distinct inhibitors for each protein to counter the activity of these proteins.

Show MeSH
Related in: MedlinePlus