Severe acute respiratory syndrome coronavirus envelope protein ion channel activity promotes virus fitness and pathogenesis.
Deletion of Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) envelope (E) gene attenuates the virus. E gene encodes a small multifunctional protein that possesses ion channel (IC) activity, an important function in virus-host interaction. To test the contribution of E protein IC activity in virus pathogenesis, two recombinant mouse-adapted SARS-CoVs, each containing one single amino acid mutation that suppressed ion conductivity, were engineered. After serial infections, mutant viruses, in general, incorporated compensatory mutations within E gene that rendered active ion channels. Furthermore, IC activity conferred better fitness in competition assays, suggesting that ion conductivity represents an advantage for the virus. Interestingly, mice infected with viruses displaying E protein IC activity, either with the wild-type E protein sequence or with the revertants that restored ion transport, rapidly lost weight and died. In contrast, mice infected with mutants lacking IC activity, which did not incorporate mutations within E gene during the experiment, recovered from disease and most survived. Knocking down E protein IC activity did not significantly affect virus growth in infected mice but decreased edema accumulation, the major determinant of acute respiratory distress syndrome (ARDS) leading to death. Reduced edema correlated with lung epithelia integrity and proper localization of Na+/K+ ATPase, which participates in edema resolution. Levels of inflammasome-activated IL-1β were reduced in the lung airways of the animals infected with viruses lacking E protein IC activity, indicating that E protein IC function is required for inflammasome activation. Reduction of IL-1β was accompanied by diminished amounts of TNF and IL-6 in the absence of E protein ion conductivity. All these key cytokines promote the progression of lung damage and ARDS pathology. In conclusion, E protein IC activity represents a new determinant for SARS-CoV virulence.
Department of Molecular and Cell Biology, Centro Nacional de Biotecnología (CNB-CSIC), Campus Universidad Autónoma de Madrid, Madrid, Spain.
Jose L
JL
Nieto-Torres
Department of Molecular and Cell Biology, Centro Nacional de Biotecnología (CNB-CSIC), Campus Universidad Autónoma de Madrid, Madrid, Spain.
Marta L
ML
DeDiego
Department of Physics, Laboratory of Molecular Biophysics. Universitat Jaume I, Castellón, Spain.
Carmina
C
Verdiá-Báguena
Department of Molecular and Cell Biology, Centro Nacional de Biotecnología (CNB-CSIC), Campus Universidad Autónoma de Madrid, Madrid, Spain.
Jose M
JM
Jimenez-Guardeño
Department of Molecular and Cell Biology, Centro Nacional de Biotecnología (CNB-CSIC), Campus Universidad Autónoma de Madrid, Madrid, Spain.
Jose A
JA
Regla-Nava
Department of Molecular and Cell Biology, Centro Nacional de Biotecnología (CNB-CSIC), Campus Universidad Autónoma de Madrid, Madrid, Spain.
Raul
R
Fernandez-Delgado
Department of Molecular and Cell Biology, Centro Nacional de Biotecnología (CNB-CSIC), Campus Universidad Autónoma de Madrid, Madrid, Spain.
Carlos
C
Castaño-Rodriguez
Department of Physics, Laboratory of Molecular Biophysics. Universitat Jaume I, Castellón, Spain.
Antonio
A
Alcaraz
School of Biological Sciences, Division of Structural and Computational Biology, Nanyang Technological University, Singapore, Singapore.
Jaume
J
Torres
Department of Physics, Laboratory of Molecular Biophysics. Universitat Jaume I, Castellón, Spain.
Vicente M
VM
Aguilella
Department of Molecular and Cell Biology, Centro Nacional de Biotecnología (CNB-CSIC), Campus Universidad Autónoma de Madrid, Madrid, Spain.
Luis
L
Enjuanes
D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D006224:Cricetinae; D005260:Female; D054884:Host-Pathogen Interactions / Q000235:genetics; D007473:Ion Channels / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008958:Models, Molecular; D030781:Organisms, Genetically Modified; D017434:Protein Structure, Tertiary; D045473:Severe acute respiratory syndrome-related coronavirus / Q000235:genetics / Q000254:growth & development* / Q000472:pathogenicity*; D045169:Severe Acute Respiratory Syndrome / Q000821:virology*; D014709:Vero Cells; D014759:Viral Envelope Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*
D007473:Ion Channels; D014759:Viral Envelope Proteins