SARS-CoV proteins decrease levels and activity of human ENaC via activation of distinct PKC isoforms.
Among the multiple organ disorders caused by the severe acute respiratory syndrome coronavirus (SARS-CoV), acute lung failure following atypical pneumonia is the most serious and often fatal event. We hypothesized that two of the hydrophilic structural coronoviral proteins (S and E) would regulate alveolar fluid clearance by decreasing the cell surface expression and activity of amiloride-sensitive epithelial sodium (Na(+)) channels (ENaC), the rate-limiting protein in transepithelial Na(+) vectorial transport across distal lung epithelial cells. Coexpression of either S or E protein with human alpha-, beta-, and gamma-ENaC in Xenopus oocytes led to significant decreases of both amiloride-sensitive Na(+) currents and gamma-ENaC protein levels at their plasma membranes. S and E proteins decreased the rate of ENaC exocytosis and either had no effect (S) or decreased (E) rates of endocytosis. No direct interactions among SARS-CoV E protein with either alpha- or gamma-ENaC were indentified. Instead, the downregulation of ENaC activity by SARS proteins was partially or completely restored by administration of inhibitors of PKCalpha/beta1 and PKCzeta. Consistent with the whole cell data, expression of S and E proteins decreased ENaC single-channel activity in oocytes, and these effects were partially abrogated by PKCalpha/beta1 inhibitors. Finally, transfection of human airway epithelial (H441) cells with SARS E protein decreased whole cell amiloride-sensitive currents. These findings indicate that lung edema in SARS infection may be due at least in part to activation of PKC by SARS proteins, leading to decreasing levels and activity of ENaC at the apical surfaces of lung epithelial cells.
Ji
Hong-Long
HL
Department of Anesthesiology, University of Alabama at Birmingham School of Medicine, Birmingham, Alabama 35233-6810, USA.
Song
Weifeng
W
Gao
Zhiqian
Z
Su
Xue-Feng
XF
Nie
Hong-Guang
HG
Jiang
Yi
Y
Peng
Ji-Bin
JB
He
Yu-Xian
YX
Liao
Ying
Y
Zhou
Yong-Jian
YJ
Tousson
Albert
A
Matalon
Sadis
S
D055371:Acute Lung Injury / Q000209:etiology; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D004705:Endocytosis; D004789:Enzyme Activation; D053503:Epithelial Sodium Channels / Q000235:genetics / Q000378:metabolism*; D005089:Exocytosis; D005260:Female; D015870:Gene Expression; D006801:Humans; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D009865:Oocytes / Q000378:metabolism; D018408:Patch-Clamp Techniques; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011654:Pulmonary Edema / Q000209:etiology; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D045473:Severe acute respiratory syndrome-related coronavirus / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D064370:Spike Glycoprotein, Coronavirus; D014162:Transfection; D014759:Viral Envelope Proteins / Q000235:genetics / Q000378:metabolism; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*; D000086082:Viroporin Proteins; D014981:Xenopus
C501689:E protein, SARS coronavirus; D053503:Epithelial Sodium Channels; D007527:Isoenzymes; D008562:Membrane Glycoproteins; D047428:Protein Kinase Inhibitors; D011994:Recombinant Proteins; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins; D014764:Viral Proteins; D000086082:Viroporin Proteins; D000584:Amiloride; D011493:Protein Kinase C