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The YXXPhi motif within the severe acute respiratory syndrome coronavirus (SARS-CoV) 3a protein is crucial for its intracellular transport
Rinki Minakshi and Kartika Padhan
Author Affiliations
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Virology Journal 2014, 11:75 doi:10.1186/1743-422X-11-75
Published: 24 April 2014
Abstract (provisional)
Background
The SARS coronavirus (SARS-CoV) 3a protein functions as an ion channel, induces apoptosis and is important for viral pathogenesis. It is expressed on the cell surface and contains a tyrosine-based sorting motif and a di-acidic motif, which may be crucial for its intracellular trafficking. However the role of these motifs is not fully understood in the case of 3a protein.
Methods
The subcellular distribution of the 3a protein was studied by immunofluorescence staining of cells transfected with wild type and mutant constructs along with markers for different intracellular compartments. Semi-quantitative RT-PCR was performed to estimate the mRNA where as western blotting was carried out to detect protein levels of wild type and mutant 3a proteins. In vitro transcription- translation was performed to estimate cell free protein synthesis.
Results
While the wild type 3a protein is efficiently transported to the plasma membrane, the protein with mutations in the tyrosine and valine residues within the YXXV motif (DeltaYXXPhi) accumulated in the Golgi compartment. However the 3a protein with mutations within the EXD di-acidic motif (DeltaEXD) showed an intracellular distribution similar to the wild type protein. Increased retention of the DeltaYXXPhi protein in the Golgi compartment also increased its association with lipid droplets. The DeltaYXXPhi protein also expressed at significantly lower levels compared to the wild type 3a protein, which was reversed with Brefeldin A and Aprotonin.
Conclusions
The data suggest that the YXXPhi motif of the SARS-CoV 3a protein is necessary for Golgi to plasma membrane transport, in the absence of which the protein is targeted to lysosomal degradation compartment via lipid droplets.
full article
Rinki Minakshi and Kartika Padhan
Author Affiliations
For all author emails, please log on.
Virology Journal 2014, 11:75 doi:10.1186/1743-422X-11-75
Published: 24 April 2014
Abstract (provisional)
Background
The SARS coronavirus (SARS-CoV) 3a protein functions as an ion channel, induces apoptosis and is important for viral pathogenesis. It is expressed on the cell surface and contains a tyrosine-based sorting motif and a di-acidic motif, which may be crucial for its intracellular trafficking. However the role of these motifs is not fully understood in the case of 3a protein.
Methods
The subcellular distribution of the 3a protein was studied by immunofluorescence staining of cells transfected with wild type and mutant constructs along with markers for different intracellular compartments. Semi-quantitative RT-PCR was performed to estimate the mRNA where as western blotting was carried out to detect protein levels of wild type and mutant 3a proteins. In vitro transcription- translation was performed to estimate cell free protein synthesis.
Results
While the wild type 3a protein is efficiently transported to the plasma membrane, the protein with mutations in the tyrosine and valine residues within the YXXV motif (DeltaYXXPhi) accumulated in the Golgi compartment. However the 3a protein with mutations within the EXD di-acidic motif (DeltaEXD) showed an intracellular distribution similar to the wild type protein. Increased retention of the DeltaYXXPhi protein in the Golgi compartment also increased its association with lipid droplets. The DeltaYXXPhi protein also expressed at significantly lower levels compared to the wild type 3a protein, which was reversed with Brefeldin A and Aprotonin.
Conclusions
The data suggest that the YXXPhi motif of the SARS-CoV 3a protein is necessary for Golgi to plasma membrane transport, in the absence of which the protein is targeted to lysosomal degradation compartment via lipid droplets.
full article
