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M1 of Murine Gamma-Herpesvirus 68 Induces Endoplasmic Reticulum Chaperone Production.

Feng J, Gong D, Fu X, Wu TT, Wang J, Chang J, Zhou J, Lu G, Wang Y, Sun R - Sci Rep (2015)

Bottom Line: We found that M1 protein selectively induces the chaperon-producing pathways (IRE1, ATF6) while, interestingly, sparing the translation-blocking arm (PERK).We identified, for the first time, a viral factor capable of selectively intervening the initiation of ER stress signaling to induce chaperon production.This finding provides a unique opportunity of using viral protein as a tool to define the activation mechanisms of individual UPR pathways.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California 90095.

ABSTRACT
Viruses rely on host chaperone network to support their infection. In particular, the endoplasmic reticulum (ER) resident chaperones play key roles in synthesizing and processing viral proteins. Influx of a large amount of foreign proteins exhausts the folding capacity in ER and triggers the unfolded protein response (UPR). A fully-executed UPR comprises signaling pathways that induce ER folding chaperones, increase protein degradation, block new protein synthesis and may eventually activate apoptosis, presenting both opportunities and threats to the virus. Here, we define a role of the MHV-68M1 gene in differential modulation of UPR pathways to enhance ER chaperone production. Ectopic expression of M1 markedly induces ER chaperone genes and expansion of ER. The M1 protein accumulates in ER during infection and this localization is indispensable for its function, suggesting M1 acts from the ER. We found that M1 protein selectively induces the chaperon-producing pathways (IRE1, ATF6) while, interestingly, sparing the translation-blocking arm (PERK). We identified, for the first time, a viral factor capable of selectively intervening the initiation of ER stress signaling to induce chaperon production. This finding provides a unique opportunity of using viral protein as a tool to define the activation mechanisms of individual UPR pathways.

No MeSH data available.


Related in: MedlinePlus

M1 localizes to cellular ER during MHV-68 infection.(A) NIH3T3 cells were infected with M1-cHA MHV-68 at MOI 10 and harvested at indicated time points for western blot analysis using antibodies specific for tublin (top), HA (middle), ORF26 and M9 (bottom). (B) NIH3T3 cells were mock-infected or infected with wild-type (WT) or M1-cHA MHV-68 at MOI 10 and fixed for IFA analysis as described in Materials and Methods using antibodies against HA (red), concanavaline A (conc A) (green) and Hoechst (Blue).
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f3: M1 localizes to cellular ER during MHV-68 infection.(A) NIH3T3 cells were infected with M1-cHA MHV-68 at MOI 10 and harvested at indicated time points for western blot analysis using antibodies specific for tublin (top), HA (middle), ORF26 and M9 (bottom). (B) NIH3T3 cells were mock-infected or infected with wild-type (WT) or M1-cHA MHV-68 at MOI 10 and fixed for IFA analysis as described in Materials and Methods using antibodies against HA (red), concanavaline A (conc A) (green) and Hoechst (Blue).

Mentions: To determine whether in the context of viral infection that M1 protein also enters ER, we constructed a recombinant MHV-68 (M1cHA) with an HA tag added to the C-terminus of the M1 ORF. The tagged virus replicates normally (Fig. S2) and enables detection of the M1 protein during infection. M1 expression was induced at 12 hours post infection in the NIH3T3 cells, in accordance with the production of viral capsid proteins ORF26 and M9 (Fig. 3A). In addition, we observed significant a co-localization of M1 with Conc A at its peak expression in the infected NIH3T3 cells (Fig. 3B), suggesting the presence of M1 protein in the ER lumen.


M1 of Murine Gamma-Herpesvirus 68 Induces Endoplasmic Reticulum Chaperone Production.

Feng J, Gong D, Fu X, Wu TT, Wang J, Chang J, Zhou J, Lu G, Wang Y, Sun R - Sci Rep (2015)

M1 localizes to cellular ER during MHV-68 infection.(A) NIH3T3 cells were infected with M1-cHA MHV-68 at MOI 10 and harvested at indicated time points for western blot analysis using antibodies specific for tublin (top), HA (middle), ORF26 and M9 (bottom). (B) NIH3T3 cells were mock-infected or infected with wild-type (WT) or M1-cHA MHV-68 at MOI 10 and fixed for IFA analysis as described in Materials and Methods using antibodies against HA (red), concanavaline A (conc A) (green) and Hoechst (Blue).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4663489&req=5

f3: M1 localizes to cellular ER during MHV-68 infection.(A) NIH3T3 cells were infected with M1-cHA MHV-68 at MOI 10 and harvested at indicated time points for western blot analysis using antibodies specific for tublin (top), HA (middle), ORF26 and M9 (bottom). (B) NIH3T3 cells were mock-infected or infected with wild-type (WT) or M1-cHA MHV-68 at MOI 10 and fixed for IFA analysis as described in Materials and Methods using antibodies against HA (red), concanavaline A (conc A) (green) and Hoechst (Blue).
Mentions: To determine whether in the context of viral infection that M1 protein also enters ER, we constructed a recombinant MHV-68 (M1cHA) with an HA tag added to the C-terminus of the M1 ORF. The tagged virus replicates normally (Fig. S2) and enables detection of the M1 protein during infection. M1 expression was induced at 12 hours post infection in the NIH3T3 cells, in accordance with the production of viral capsid proteins ORF26 and M9 (Fig. 3A). In addition, we observed significant a co-localization of M1 with Conc A at its peak expression in the infected NIH3T3 cells (Fig. 3B), suggesting the presence of M1 protein in the ER lumen.

Bottom Line: We found that M1 protein selectively induces the chaperon-producing pathways (IRE1, ATF6) while, interestingly, sparing the translation-blocking arm (PERK).We identified, for the first time, a viral factor capable of selectively intervening the initiation of ER stress signaling to induce chaperon production.This finding provides a unique opportunity of using viral protein as a tool to define the activation mechanisms of individual UPR pathways.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California 90095.

ABSTRACT
Viruses rely on host chaperone network to support their infection. In particular, the endoplasmic reticulum (ER) resident chaperones play key roles in synthesizing and processing viral proteins. Influx of a large amount of foreign proteins exhausts the folding capacity in ER and triggers the unfolded protein response (UPR). A fully-executed UPR comprises signaling pathways that induce ER folding chaperones, increase protein degradation, block new protein synthesis and may eventually activate apoptosis, presenting both opportunities and threats to the virus. Here, we define a role of the MHV-68M1 gene in differential modulation of UPR pathways to enhance ER chaperone production. Ectopic expression of M1 markedly induces ER chaperone genes and expansion of ER. The M1 protein accumulates in ER during infection and this localization is indispensable for its function, suggesting M1 acts from the ER. We found that M1 protein selectively induces the chaperon-producing pathways (IRE1, ATF6) while, interestingly, sparing the translation-blocking arm (PERK). We identified, for the first time, a viral factor capable of selectively intervening the initiation of ER stress signaling to induce chaperon production. This finding provides a unique opportunity of using viral protein as a tool to define the activation mechanisms of individual UPR pathways.

No MeSH data available.


Related in: MedlinePlus