Rapid translocation and insertion of the epithelial Na+ channel in response to RhoA signaling.
Activity of the epithelial Na+ channel (ENaC) is limiting for Na+ absorption across many epithelia. Consequently, ENaC is a central effector impacting systemic blood volume and pressure. Two members of the Ras superfamily of small GTPases, K-Ras and RhoA, activate ENaC. K-Ras activates ENaC via a signaling pathway involving phosphatidylinositol 3-kinase and production of phosphatidylinositol 3,4,5-trisphosphate with the phospholipid directly interacting with the channel to increase open probability. How RhoA increases ENaC activity is less clear. Here we report that RhoA and K-Ras activate ENaC through independent signaling pathways and final mechanisms of action. Activation of RhoA signaling rapidly increases the membrane levels of ENaC likely by promoting channel insertion. This process dramatically increases functional ENaC current, resulting in tight spatial-temporal control of these channels. RhoA signals to ENaC via a transduction pathway, including the downstream effectors Rho kinase and phosphatidylinositol-4-phosphate 5-kinase. Phosphatidylinositol 4,5-biphosphate produced by activated phosphatidylinositol 4-phosphate 5-kinase may play a role in targeting vesicles containing ENaC to the plasma membrane.
Pochynyuk
Oleh
O
Department of Physiology, University of Texas Health Science Center, San Antonio, Texas 78229, USA.
Medina
Jorge
J
Gamper
Nikita
N
Genth
Harald
H
Stockand
James D
JD
Staruschenko
Alexander
A
D000818:Animals; D016466:CHO Cells; D019556:COS Cells; D002462:Cell Membrane / Q000378:metabolism*; D002522:Chlorocebus aethiops; D006224:Cricetinae; D053503:Epithelial Sodium Channels / Q000235:genetics / Q000378:metabolism*; D011905:Genes, ras; D018408:Patch-Clamp Techniques; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
D053503:Epithelial Sodium Channels; D019869:Phosphatidylinositol 3-Kinases; D019269:Phosphatidylinositol 4,5-Diphosphate; D017853:Phosphotransferases (Alcohol Group Acceptor); D011993:Recombinant Fusion Proteins; D020741:rho GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein; C020077:1-phosphatidylinositol-4-phosphate 5-kinase